Access profile

Ideal applicants are holders of master’s degrees in Information and Communication Technologies, and preferably Telecommunications Engineering. However, the multidisciplinary nature of some of the Department’s research groups makes it desirable to consider admitting candidates with other degrees in the fields of physics, computing, biology and computational linguistics.

In addition to this academic profile, certain characteristics are considered important for applicants to have, including interest in the research projects being carried out in the Department, having critical and analytical abilities, having initiative, being consistent and persistent in their work and being able to work in a team.

Degree classifications:

• Direct admission: European Master of Science in Research on Information and Communication Technologies (MERIT) and Master of Science in Communication and Network Engineering (COMNET). This last programme has not been submitted for verification, but it is expected to be verified very soon.
• Preferential admission: other postgraduate programmes in the field of ICT engineering: telecommunications engineering, telematic engineering, computer sciences and photonic technologies.
• Others: depending upon the presence of other multidisciplinary research groups in the Department, applicants with degrees from other programmes that do not coincide with the aforementioned profiles will also be considered: informatics, physical sciences, chemistry, mathematics, biology and computational linguistics.

An appropriate level of English is required for this programme.

Output profile

Doctoral candidates who complete a doctoral degree will have acquired the following competencies, which are needed to carry out quality research (Royal Decree 99/2011, of 28 January, which regulates official doctoral studies):

a) A systematic understanding of the field of study and a mastery of the research skills and methods related to the field.
b) An ability to conceive, design or create, put into practice and adopt a substantial process of research or creation.
c) An ability to contribute to pushing back the frontiers of knowledge through original research.
d) A capacity for critical analysis and an ability to assess and summarise new and complex ideas.
e) An ability to communicate with the academic and scientific community and with society in general as regards their fields of knowledge in the manner and languages that are typical of the international scientific community to which they belong.
f) An ability to foster scientific, technological, social, artistic and cultural progress in academic and professional contexts within a knowledge-based society.

The award of a doctoral degree must equip the graduate for work in a variety of settings, especially those requiring creativity and innovation. Doctoral graduates must have at least acquired the personal skills needed to:

a) Develop in contexts in which there is little specific information.
b) Find the key questions that must be answered to solve a complex problem.
c) Design, create, develop and undertake original, innovative projects in their field.
d) Work as part of a team and independently in an international or multidisciplinary context.
e) Integrate knowledge, deal with complexity and make judgements with limited information.
f) Offer criticism on and intellectually defend solutions.

Finally, with respect to competencies, doctoral students must:
a) have acquired advanced knowledge at the frontier of their discipline and demonstrated, in the context of internationally recognised scientific research, a deep, detailed and well-grounded understanding of theoretical and practical issues and scientific methodology in one or more research fields;
b) have made an original and significant contribution to scientific research in their field of expertise that has been recognised as such by the international scientific community;
c) have demonstrated that they are capable of designing a research project that serves as a framework for carrying out a critical analysis and assessment of imprecise situations, in which they are able to apply their contributions, expertise and working method to synthesise new and complex ideas that yield a deeper knowledge of the research context in which they work;
d) have developed sufficient autonomy to set up, manage and lead innovative research teams and projects and scientific collaborations (both national and international) within their subject area, in multidisciplinary contexts and, where appropriate, with a substantial element of knowledge transfer;
e) have demonstrated that they are able to carry out their research activity in a socially responsible manner and with scientific integrity;
f) have demonstrated, within their specific scientific context, that they are able to make cultural, social or technological advances and promote innovation in all areas within a knowledge-based society;
g) have demonstrated that they are able to participate in scientific discussions at the international level in their field of expertise and disseminate the results of their research activity to audiences of all kinds.

Number of places

30

Duration of studies and dedication regime

Duration
The maximum period of study for full-time doctoral studies is three years, counted from the date of admission to the programme to the date of submission of the doctoral thesis. The academic committee of the doctoral programme may authorise a doctoral candidate to pursue doctoral studies on a part-time basis. In this case, the maximum period of study is five years, counting from the date of admission to the programme to the date of submission of the doctoral thesis. For calculating these periods, the date of admission is considered to be the date of the first enrolment for tutorials, and the date of submission the moment in which the Doctoral School officially deposits the doctoral thesis.

For full-time doctoral candidates, the minimum period of study is two years, counted from the date of an applicant's admission to the programme until the date on which the doctoral thesis is deposited; for part-time doctoral candidates it is four years. When there are justified grounds for doing so, and the thesis supervisor and academic tutor have given their authorisation, doctoral candidates may request that the academic committee of their doctoral programme exempt them from the minimum period of study requirement.

The calculation of periods of study will not include periods of absence due to illness, pregnancy or any other reason provided for in the regulations in force. Students who find themselves in any of these circumstances must notify the academic committee of the doctoral programme, which, where appropriate, must inform the Doctoral School. Doctoral candidates may also temporarily withdraw from the programme for up to one year, and this period may be extended for an additional year. Doctoral candidates who wish to interrupt their studies must submit a justified request to the academic committee of the doctoral programme, which will decide whether or not to approve the request. Each programme will establish conditions for readmission to doctoral studies.

Extension
If full-time doctoral candidates have not applied to deposit their thesis by the end of the three-year period of study, the academic committee of the programme may authorise an extension of up to one year. In exceptional circumstances, a further one-year extension may be granted, subject to the conditions established by the corresponding doctoral programme. In the case of part-time doctoral candidates, an extension of two years may be authorised. In both cases, in exceptional circumstances a further one-year extension may be granted by the Doctoral School's Standing Committee, upon the submission of a reasoned application by the academic committee of the doctoral programme.

Dismissal from the doctoral programme
A doctoral candidate may be dismissed from a doctoral programme for the following reasons:

• The doctoral candidate submitting a justified application to withdraw from the programme.
• The maximum period of study and of extensions thereof ending.
• The doctoral candidate not having enrolled every academic year (unless he or she has been authorised to temporarily withdraw).
• The doctoral candidate failing two consecutive assessments.
• The doctoral candidate having disciplinary proceedings filed against him or her that rule that he or she must be dismissed from the UPC.

Dismissal from the programme implies that doctoral candidates cannot continue studying at the UPC and the closing of their academic record. This notwithstanding, they may apply to the academic committee of the programme for readmission and the committee must reevaluate them in accordance with the criteria established in the regulations.

Organization

• Muñoz Medina, Olga

• Lazaro Villa, Jose Antonio
• Lopez Martinez, Carlos
• Mateu Mateu, Jordi
• Muñoz Medina, Olga
• Villares Piera, Nemesio Javier

• Department of Signal Theory and Communications (PROMOTORA)

Doctoral Unit - ICT North Campus Management and Support Unit (UTGCNTIC)

C. Jordi Girona, 1-3. Building B4-003 (North Campus)
Tel.: 934 017 233
E-mail: doctorat.tsc@upc.edu

Access profile

Ideal applicants are holders of master’s degrees in Information and Communication Technologies, and preferably Telecommunications Engineering. However, the multidisciplinary nature of some of the Department’s research groups makes it desirable to consider admitting candidates with other degrees in the fields of physics, computing, biology and computational linguistics.

In addition to this academic profile, certain characteristics are considered important for applicants to have, including interest in the research projects being carried out in the Department, having critical and analytical abilities, having initiative, being consistent and persistent in their work and being able to work in a team.

Degree classifications:

• Direct admission: European Master of Science in Research on Information and Communication Technologies (MERIT) and Master of Science in Communication and Network Engineering (COMNET). This last programme has not been submitted for verification, but it is expected to be verified very soon.
• Preferential admission: other postgraduate programmes in the field of ICT engineering: telecommunications engineering, telematic engineering, computer sciences and photonic technologies.
• Others: depending upon the presence of other multidisciplinary research groups in the Department, applicants with degrees from other programmes that do not coincide with the aforementioned profiles will also be considered: informatics, physical sciences, chemistry, mathematics, biology and computational linguistics.

An appropriate level of English is required for this programme.

Access requirements

Applicants must hold a Spanish bachelor’s degree or equivalent and a Spanish master’s degree or equivalent, provided they have completed a minimum of 300 ECTS credits on the two degrees (Royal Decree 43/2015, of 2 February)

In addition, the following may apply:

• Holders of an official degree awarded by a university in Spain or any other country in the European Higher Education Area, pursuant to the provisions of Article 16 of Royal Decree 1393/2007, of 29 October, which establishes official university course regulations, who have completed a minimum of 300 ECTS credits on official university degrees, of which at least 60 must be at the master's degree level.
• Holders of an official Spanish bachelor’s degree comprising at least 300 credits, as provided for by EU regulations. Holder of degrees of this kind must complete bridging courses unless the curriculum of the bachelor’s degree in question included research training credits equivalent in value to those which would be earned on a master's degree.
• Holders of an official university qualification who, having passed the entrance examination for specialised medical training, have completed at least two years of a training course leading to an official degree in a health-sciences specialisation.
• Holders of a degree issued under a foreign education system. In these cases, homologation is not required, but the UPC must verify that the degree certifies a level of training equivalent to an official Spanish master's degree and qualifies the holder for admission to doctoral studies in the country where it was issued. Admission on this basis does not imply homologation of the foreign degree or its recognition for any purpose other than admission to doctoral studies.
• Holders of a Spanish doctoral qualification issued under previous university regulations.

Note 1: Doctoral studies entrance regulations for holders of an undergraduate degree awarded before the introduction of the EHEA (CG 47/02 2014)

Note 2: Governing Council Decision 64/2014, which approves the procedure and criteria for assessing the fulfilment of academic admission requirements for doctoral studies by holders of non-homologated foreign degrees (CG 25/03 2014)

Admission criteria and merits assessment

• Appropriateness of academic background with the activities carried out in the proposed research group: 25%.
• Knowledge of the English language: 20%.
• Quality of university from which previous degree was awarded: 10%.
• Motivation letter/letters of recommendation: 10%.

An assessment will be considered positive is an applicant is given a score of 3 or more out of 5.

Based on the content of the motivation letter and the applicant’s preparedness, the Postgraduate Committee will assign a thesis supervisor.

If candidates do not have a degree in some kind of ICT engineering, they will have to take the bridging courses recommended by their supervisors and the programme, whether courses from the associated master’s programmes (MET, MATT) or other ones.

Training complements

The Postgraduate Committee of the Signal Theory and Communications Department may require candidates to complete specific bridging courses. In this case, the Committee will monitor the bridging courses and set up appropriate criteria to limit their length.

The courses shall involve training in research, but in no case will candidates be required to enrol in 60 or more ECTS credits (according to the academic regulations for doctoral studies, bridging courses could include transversal education, but there are plans to change to this so that these bridging courses exclusively provide research credits, especially in cases involving doctoral programmes with 300 ECTS credits).

Depending on the activities completed by the candidates, the Postgraduate Committee of the Signal Theory and Communications Department may propose measures, in addition to those established by current regulations, that would disassociate candidates who do not meet the established requisites.

The Postgraduate Committee may require candidates who are to be admitted to complete certain bridging courses in order to better adapt their profiles to the programme’s requirements regarding the knowledge necessary to properly complete the doctoral studies.

No bridging courses will be required for those who graduated from the MET, MASTEAM or MATT programmes, or any of the other previously mentioned ICT programmes.

For those who completed other programmes, the bridging coursework required will depend upon their backgrounds and the activities carried out by the research groups in which they will participate, and it could be up to 30 ECTS.

The courses to be taken are offered by the MET, MASTEAM or MATT programmes.

Also, depending on the characteristics of some of the Department’s research groups, courses from the following UPC programmes will also be considered:
• Master’s programme in Telecommunications Engineering
• Master’s programme in Electrical Engineering
• Master’s programme in Photonics
• Master’s programme in Innovation and Research in Informatics
• Master’s programme in Artificial Intelligence

After consulting with candidates’ supervisors, it will be the sole responsibility of the TSC Department’s Postgraduate Committee to determine which courses students will have to take to complete these bridging courses. In any case, the aim of the courses will always be to fill in the gaps that students are seen to have in their academic transcripts with regard to the activities carried out by the research group in which they will participate.

Enrolment period for new doctoral students

Students enrolling in the doctoral programme for the first time must do so by the deadline specified in the admission decision.
Unless otherwise expressly indicated, enrolments corresponding to admission decisions issued from the second half of April on must be completed within the ordinary enrolment period for the current academic year.

More information at the registration section for new doctoral students

Enrolment period

Ordinary period for second and successive enrolments: first half of October.

More information at the general registration section

Procedure for the preparation and defense of the research plan

Doctoral candidates must submit a research plan, which will be included in their doctoral student activity report, before the end of the first year. The plan may be improved over the course of the doctoral degree. It must be endorsed by the tutor and the supervisor, and it must include the method that is to be followed and the aims of the research.

At least one of these annual assessments will include a public presentation and defence of the research plan and work done before a committee composed of three doctoral degree holders, which will be conducted in the manner determined by each academic committee. The examination committee awards a Pass or Fail mark. A Pass mark is a prerequisite for continuing on the doctoral programme. Doctoral candidates awarded a Fail mark must submit a new research plan for assessment by the academic committee of the doctoral programme within six months.

The committee assesses the research plan every year, in addition to all of the other activities in the doctoral student activity report. Doctoral candidates who are awarded two consecutive Fail marks for the research plan will be obliged to definitely withdraw from the programme.

If they change the subject of their thesis, they must submit a new research plan.

Formation activities

Activity: Tutorial.
- Hours: 288.
- Type: compulsory.

Activity: Mobility.
- Hours: 480.
- Type: optional.

Activity: Assessment based on doctoral student activity report (DAD) and research plan.
- Hours: 4.
- Type: compulsory.

Activity: Training in information skills.
- Hours: 1,5.
- Type: compulsory.

Activity: Research methodology.
- Hours: 12.
- Type: compulsory.

Activity: Innovation and creativity.
- Hours: 8.
- Type: optional.

Activity: Language and communication skills.
- Hours: 18.
- Type: optional.

Activity: Courses and seminars.
- Hours: 50.
- Type: optional.

Activity: Workshops.
- Hours: 8.
- Type: optional.

Procedure for assignment of tutor and thesis director

The academic committee of the doctoral programme assigns a thesis supervisor to each doctoral candidate when they are admitted or enrol for the first time, taking account of the thesis supervision commitment referred to in the admission decision.

The thesis supervisor will ensure that training activities carried out by the doctoral candidate are coherent and suitable, and that the topic of the candidate’s doctoral thesis will have an impact and make a novel contribution to knowledge in the relevant field. The thesis supervisor will also guide the doctoral candidate in planning the thesis and, if necessary, tailoring it to any other projects or activities undertaken. The thesis supervisor will generally be a UPC professor or researcher who holds a doctoral degree and has documented research experience. This includes PhD-holding staff at associated schools (as determined by the Governing Council) and UPC-affiliated research institutes (in accordance with corresponding collaboration and affiliation agreements). When thesis supervisors are UPC staff members, they also act as the doctoral candidate’s tutor.

PhD holders who do not meet these criteria (as a result of their contractual relationship or the nature of the institution to which they are attached) must be approved by the UPC Doctoral School's Standing Committee in order to participate in a doctoral programme as researchers with documented research experience.

The academic committee of the doctoral programme may approve the appointment of a PhD-holding expert who is not a UPC staff member as a candidate’s thesis supervisor. In such cases, the prior authorisation of the UPC Doctoral School's Standing Committee is required. A UPC staff member who holds a doctoral degree and has documented research experience must also be proposed to act as a co-supervisor, or as the doctoral candidate’s tutor if one has not been assigned.

A thesis supervisor may step down from this role if there are justified reasons (recognised as valid by the committee) for doing so. If this occurs, the academic committee of the doctoral programme will assign the doctoral candidate a new thesis supervisor.

Provided there are justified reasons for doing so, and after hearing any relevant input from the doctoral candidate, the academic committee of the doctoral programme may assign a new thesis supervisor at any time during the period of doctoral study.

If there are academic reasons for doing so (an interdisciplinary topic, joint or international programmes, etc.) and the academic committee of the programme gives its approval, an additional thesis supervisor may be assigned. Supervisors and co-supervisors have the same responsibilities and academic recognition.

The maximum number of supervisors of a doctoral thesis is two: a supervisor and a co-supervisor.

For theses carried out under a cotutelle agreement or as part of an Industrial Doctorate, if necessary and if the agreement foresees it this maximum number of supervisors may not apply. This notwithstanding, the maximum number of supervisors belonging to the UPC is two.

More information at the PhD theses section

Permanence

The academic committee of the programme may authorise an extension of up to one year for full-time doctoral candidates who have not applied to deposit their thesis by the end of the three-year period of study, in the terms outlined in the Academic Regulations for Doctoral Studies of the Universitat Politècnica de Catalunya. In the case of part-time candidates, an extension of two years may be authorised. In both cases, in exceptional circumstances a further one-year extension may be granted by the Doctoral School's Standing Committee, upon the submission of a reasoned application by the academic committee of the doctoral programme.

A doctoral candidate may be dismissed from a doctoral programme for the following reasons:

• The doctoral candidate submitting a justified application to withdraw from the programme.
• The maximum period of study and of extensions thereof ending.
• The doctoral candidate not having enrolled every academic year (unless he or she has been authorised to temporarily withdraw).
• The doctoral candidate failing two consecutive assessments.
• The doctoral candidate having disciplinary proceedings filed against him or her that rule that he or she must be dismissed from the UPC.

Dismissal from the programme implies that doctoral candidates cannot continue studying at the UPC and the closing of their academic record. This notwithstanding, they may apply to the academic committee of the programme for readmission and the committee must reevaluate them in accordance with the criteria established in the regulations.

International Mention

The doctoral degree certificate may include International Doctorate mention. In this case, the doctoral candidate must meet the following requirements:

a) During the period of study leading to the award of the doctoral degree, the doctoral candidate must have spent at least three months at a respected higher education institution or research centre outside Spain to complete courses or do research work. The stays and activities carried out must be endorsed by the thesis supervisor and authorised by the academic committee of the programme. The candidate must provide a certifying document issued by the person responsible for the research group of the body or bodies where the stay or activity was completed. This information will be added to the doctoral student’s activity report.
b) Part of the thesis (at least the summary and conclusions) must be written and presented in one of the languages commonly used for science communication in the relevant field of knowledge, which must not be an official language of Spain. This rule does not apply to stays and reports in Spanish or to experts from Spanish-speaking countries.
c) At least two PhD-holding experts belonging to a higher education institution or research centre outside Spain must have issued officially certified reports on the thesis.
d) The thesis examination committee must have included at least one PhD-holding expert from a higher education or research institution outside Spain who was not responsible for the candidate’s stay abroad (point a) above).
e) The thesis defence must have taken place on UPC premises or, in the case of joint programmes, at the location specified in the collaboration agreement.

List of authorized thesis for defense

• FERNÁNDEZ CAÑELLAS, DÈLIA: Knowledge graph population from news streams
  
  Author: FERNÁNDEZ CAÑELLAS, DÈLIA
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Deposit date: 14/07/2023
  Reading date: 09/10/2023
  Reading time: 16:30
  Reading place: Aula Merit Edifici D5 porta 010, Dpt. TSC
  Thesis director: GIRÓ NIETO, XAVIER | BOU BALUST, ELISENDA
  Committee:
       PRESIDENT: RIGAU CLARAMUNT, GERMAN
       SECRETARI: RODRÍGUEZ HONTORIA, HORACIO
       VOCAL: LANGMEAD, GREGORY
  Thesis abstract: Media producers publish large amounts of multimedia content online - both text, audio, image and video. As the online media market grows, the management and delivery of contents becomes a challenge.Semantic and linking technologies can be used to organize and exploit these contents through the use of knowledge graphs.This industrial doctorate dissertation addresses the problem of constructing knowledge resources and integrating them into a system used by media producers to manage and explore their contents. For that purpose, knowledge graphs and their maintenance through Information Extraction (IE) from news streams is studied. This thesis presents solutions for multimedia understanding and knowledge extraction from online news, and their exploitation in real product applications, and it is structured in three parts.The first part consists on the construction of IE tools that will be used for knowledge graph population. For that, we built an holistic Entity Linking (EL) system capable of combining multimodal data inputs to extract a set of semantic entities that describe news content. The EL system is followed by a Relation Extraction (RE) model that predicts relations between pairs of entities with a novel method based on entity-type knowledge. The final system is capable of extracting triples describing the contents of a news article.The second part focuses on the automatic construction of a news event knowledge graph. We present an online multilingual system for event detection and comprehension from media feeds, called VLX-Stories.The system retrieves information from news sites, aggregates them into events (event detection), and summarizes them by extracting semantic labels of its most relevant entities (event representation) in order to answer four Ws from journalism: who, what, when and where. This part of the thesis deals with the problems of Topic Detection and Tracking (TDT), topic modeling and event representation.The third part of the thesis builds on top of the models developed in the two previous parts to populate a knowledge graph from aggregated news. The system is completed with an emerging entity detection module, which detects mentions of novel people appearing on the news and creates new knowledge graph entities from them.Finally, data validation and triple classification tools are added to increase the quality of the knowledge graph population.This dissertation addresses many general knowledge graph and information extraction problems, like knowledge dynamicity, self-learning, and quality assessment. Moreover, as an industrial work, we provide solutions that were deployed in production and verify our methods with real customers.
  
• LUGO HERNÁNDEZ, EDUARDO: Analysis of thin-film solidly mounted resonators for applications in harsh environments
  
  Author: LUGO HERNÁNDEZ, EDUARDO
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Deposit date: 24/07/2023
  Reading date: 10/10/2023
  Reading time: 16:00
  Reading place: difici C4 Aula 131G, Escola T.S.E. de Telecomunicació de Barcelona
  Thesis director: MATEU MATEU, JORDI | MIREA, TEONA
  Committee:
       PRESIDENT: RODRÍGUEZ MÉNDEZ, LUIS MANUEL
       SECRETARI: VALENZUELA GONZALEZ, JOSE LUIS
       VOCAL NO PRESENCIAL: MIGUEL RAMOS, MARIO DE
  Thesis abstract: The sensing industry is constantly growing due to its demand in fields that require critical and essential information (data environment) for human safeness and quality of life. In recent years, designers, researchers and engineers have paid especial attention in at least three important characteristics in order to obtain reliable devices. These characteristics are: costs reduction, miniaturization for electronic integration compatibility (IC) and sensitivity. A promising technology that has the capacity to meet these requirements is the electroacoustic one. This technology is primary based on the propagation of surface acoustic waves (SAWs) and bulk acoustic waves (BAWs) in a piezoelectric material. For the last years, these devices have been studied and tested in different sensing applications such as gas detectors (gravimetric sensors), temperature monitoring and thin film growth. They have been tested in different fields such as automotive industry, food preservation and thin film deposition, and they have proved excellent performance. Moreover, these applications are special because the collected data occurs in harsh environments. Therefore, the required technology must possess special characteristics to meet these requirements under such environmental conditions. One more time, electroacoustic devices have showed good performance on this type of environments and conditions. BAW devices are an excellent solution to overcome the requirements needed due to their high resolution, straightforward fabrication process, high sensitivity, low costs, low size and compatibility with the IC technology. Specifically, the Solidly Mounted Resonator (SMR) configuration based on AlN is one of the best option since it has been widely studied. This configuration is well-known for its applications in Radio Frequency communication systems. Furthermore, it has demonstrated excellent performance and high quality factors in various sensing applications, even at high temperatures up to 1000°C. Additionally, it has exhibited spurious-free resonances. This characteristic is especially important in sensing applications as the presence of spurious modes can distort the sensor behavior and modify the results i.e., in mass detectors these spurious modes might affect the series frequency resonance, which is directly related with the change of the detected mass. Although this technology has been tested and showed excellent performance at high temperatures, there is a lack of studies in applications at very low or cryogenic temperatures. In this research work, we present results based on specific designs and simulations, considering the aforementioned requirements, such as temperature and pressure variations, as well as spurious-free resonances. This thesis introduces two significant novelties: the investigation conducted at low temperatures, which remains an essential area of research, on the other side, we include the examination of geometry and topology as potential contributors to the presence of spurious resonances. Additionally, we experimentally validate our models by means of data extracted from fabricated SMRs, which are based on the c-axis oriented AlN piezoelectric material. In order to carry out our simulations, we have paid careful attention to the well-known one-dimensional Mason¿s model and Butterworth-Van Dyke (BVD), which are based on the physical properties of materials and equivalent electrical circuit, respectively. We have modified and updated these models to analyze the presence of a new resonator coupled with the main resonance frequency (2.5 GHz). In addition, we have put an enormous attention in the quality factor (Q), frequency resonances and effective piezoelectric coupling factor (keff2) behavior as a function of temperature. We carried out simulations and compared them with measurements from -160 °C up to 422°C.
  
• REZAZADEH, FARHAD: Lifelong AI-Driven Zero-Touch Network Slicing
  
  Author: REZAZADEH, FARHAD
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Deposit date: 08/09/2023
  Reading date: 13/10/2023
  Reading time: 10:00
  Reading place: Aula Multimèdia, B3, ETSETB
  Thesis director: VERIKOUKIS, CHRISTOS
  Committee:
       PRESIDENT: NIYATO, DUSIT
       SECRETARI: ADELANTADO FREIXER, FERRAN
       VOCAL NO PRESENCIAL: SPYROPOULOS, THRASYVOULOS
  Thesis abstract: The sixth-generation (6G) network's evolution necessitates advancements in algorithms and architecture to transition from an AI-native to an intrinsic trustworthy automation-native system. Network slicing creates multiple virtual networks for diverse service requirements and is a crucial technology for future communication systems and 6G networks. This technology will facilitate numerous aspects of life, society, and industry, meeting the communication needs of both humans and intelligent machines. This is made possible by employing softwarization and virtualization technologies, including software-defined networking (SDN) and network functions virtualization (NFV), to enable the necessary flexibility and programmability required for network slicing. However, the implementation of network slicing in radio access networks (RAN) is challenging due to the complexity of managing RAN operations. This gap is addressed with zero-touch network slicing, a fully automated management and orchestration scheme, which eliminates the need for fixed contracts and manual intervention. The decision engine, a main component of this technology, employs algorithmic innovation to optimize network resource allocation and handle the challenges of RAN slicing, including energy efficiency, latency, scalability, and trustworthiness. In resource allocation, a joint optimization approach is used to balance energy and latency with service quality. A stochastic Actor-Critic approach is proposed to streamline the learning procedure and reduce the need for hyperparameter tuning in an energy-aware network slicing setup. Additionally, a massive deep reinforcement learning-based actor-learner framework is introduced to tackle complexity issues and control challenges in network slicing. The temporal variations of traffic demand pose a significant challenge for resource planning and allocation in the RAN domain. To mitigate this, a distributed architecture for RAN slice resource orchestration is proposed, featuring multiple AI-enabled decision agents that perform local radio allocation decisions without a centralized control entity. A federated learning scheme, aligned with the recent development of the Open RAN architecture, is designed to enhance local decision-making capabilities. Despite AI's effectiveness, concerns persist regarding the lack of transparency in deep neural networks, posing risks to reliability and security in network scenarios. This lack of trust prevents telecommunications operators from widely deploying AI models in their networks. To address this, we proposed SliceOps architecture that consolidates explainable ML operations in a standalone slice, offering AI services to other slices. This setup enhances the reliability and interpretability of AI models, facilitating swift deployment in the network with greater consistency. By transitioning from AI-native to automation-native, this framework manages both service and underlying AI functions, allowing full potential harnessing of slicing in RAN while reducing complexities.
  

Last update: 04/10/2023 04:45:29.

List of lodged theses

• AYENEW, TADEGE MIHRETU: Optimized content caching strategies for multi-access edge computing (MEC)-assisted future cellular networks
  
  Author: AYENEW, TADEGE MIHRETU
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Deposit date: 29/09/2023
  Reading date: pending
  Reading time: pending
  Reading place: pending
  Thesis director: MERAKOS, LAZAROS | PASSAS, NIKOLAOS
  Committee:
       PRESIDENT NO PRESENCIAL: CASSIOLI, DAJANA
       SECRETARI: RUIZ BOQUE, SILVIA
       VOCAL NO PRESENCIAL: GKONIS, PANAGIOTIS
  Thesis abstract: Handling the tsunami of multimedia content is a big challenge for heterogeneous cellular networks.Serving large volumes of content from the central system to end-users, through a bandwidth-limitednetwork, at peak time leads to network congestion. Typically, popular contents impede network performance and incur a high cost because they are redundantly transmitted to users. Also, somecontents are too far from users, causing service delays. Owing to the above reasons, the networkperformance deteriorates, and meeting the required quality of experience becomes difficult. One way to improve HCN performance is through the use of caching of popular contents. This research proposes and analyzes content caching optimization strategies for several scenarios of cellular networks enhanced with multi-access edge computing.Several studies have shown that backhaul congestion and service latency can be reduced by applying efficient content caching policies. However, a challenging issue is that the network edges have limited resources, such as cache size and computation. Due to such limitations, how to effectively exploit the available network resource and cache contents optimally remains to be an open-ended question. Content caching strategies have been the subject of several research efforts; however, in most works, the accurate modeling of the caching problem is a challenging open problem. In addition, most of them employ intractable optimization tools, which depend on greedy algorithms and heuristics. Most strategiesmust also be scaled into large networks and have computationally feasible solutions. More specifically,the complex joint-caching problem remains open.This dissertation aims to fill these gaps and contribute to modeling real-network characteristics using advanced combinatorial optimization tools. We propose different content caching formulations and design novel optimization strategies. The general approach is to effectively model caching schemes using popularity-based selection problems and solve the models using efficient algorithms. We devise an optimal caching scheme using dynamic programming. A more complex but exact caching strategy is proposed, where heterogeneous caching edges are clustered to offload the central system. Furthermore, we propose three demand-aware caching strategies, where a source caches contents to multiple caching edges, and the content popularity differs for each edge. Finally, we propose a demand-aware joint caching problem modeling where the content placement and delivery are mutually optimized.The performances of the proposed strategies are thoroughly evaluated using extensive system-levelsimulations, comparing them with existing content caching strategies. The numerical results show thatthe proposed strategies outperform baseline strategies in terms of relevant key performance indicators. Also, the associated Multi-access Edge Computing (MEC) functionalities are omputationally feasible. Finally, useful cache design guidelines are set for various wireless network scenarios, contributing to the future design of emerging technologies and practical business models.
  

Last update: 04/10/2023 04:30:30.

List of defended theses by year

• ALEMANY PRATS, POL: Quality of service, security and trustworthiness for network slices
  
  Author: ALEMANY PRATS, POL
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 23/03/2023
  Thesis director: VILALTA CAÑELLAS, RICARD | MUÑOZ GONZALEZ, RAUL
  

  Committee:
       PRESIDENT: MOZO VELASCO, ALBERTO
       SECRETARI: SPADARO, SALVATORE
       VOCAL: NATALINO, CARLOS
  Thesis abstract: The telecommunications' systems are becoming much more intelligent and dynamic due to the expansion of the multiple network types (i.e., wired, wireless, Internet of Things (IoT) and cloud-based networks). Due to this network variety, the old model of designing a specific network for a single purpose and so, the coexistence of different and multiple control systems is evolving towards a new model in which the use of a more unified control system is able to offer a wide range of services for multiple purposes with different requirements and characteristics. To achieve this situation, the networks have become moredigital and virtual thanks to the creation of the Software-Defined Networking (SDN) and the Network Function Virtualization (NFV).Network Slicing takes the strengths from these two technologies and allows the network control systems to improve their performance as the services may be deployed and their interconnection configured through multiple-transport domainsby using NFV/SDN tools such as NFV-Orchestrators (NFV-O) and SDN Controllers. This thesis has the main objective to contribute to the state of the art of Network Slicing, with a special focus on security aspects towards the architectures and processes to deploy, monitor and enforce secured and trusted resources to compose network slices. Finally, this document is structured in eight chapters:Chapter 1 provides the motivation and objectives of this thesis which describes to where this thesis contributes and what it was expected to study, evaluate and research. Chapter 2 presents the background necessary to understand the followingchapters. This chapter presents a state of the art with three clear sections: 1) the key technologies necessary to create network slices, 2) an overview about the relationship between Service Level Agreements (SLAs) and network slices with aspecific view on Security Service Level Agreements (SSLAs), and, 3) the literature related about distributed architectures and systems and the use of abstraction models to generate trust, security, and avoid management centralization. Chapter 3introduces the research done associated to Network Slicing. First with the creation of network slices using resources placed multiple computing and transport domains. Then, this chapter illustrates how the use of multiple virtualization technologies allows to have more efficient network slices deployments and where each technology fits better to accomplish the performance improvements. Chapter 4 presents the research done about the management of network slices and the definition of SLAs and SSLAs to define the service and security requirements to accomplish the expected QoS and the right security level. Chapter 5 studies the possibility to change at certain level the trend to centralise the control and management architectures towards a distributed design. Chapter 6 follows focuses on the generation of trust among service resourcesproviders. This chapter first describes how the concept of trust is mapped into an analytical system and then, how the trust management among providers and clients is done in a transparent and fair way. Chapter 7 is devoted to the dissemination results and presents the set of scientific publications produced in the format of journals, international conferences or collaborations. Chapter 8 concludes the work and outcomes previously presented and presents possible future research.
  

• ARAUJO DA SILVA, MARCOS PAULO: Remote sensing for atmospheric observation and wind energy: over-land boundary layer and off-shore atmospheric stability
  
  Author: ARAUJO DA SILVA, MARCOS PAULO
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 29/06/2023
  Thesis director: ROCADENBOSCH BURILLO, FRANCISCO
  

  Committee:
       PRESIDENT: BAY HASAGER, CHARLOTTE
       SECRETARI: BALDASANO RECIO, JOSE M.
       VOCAL: O\'CONNOR, EWAN JAMES
  Thesis abstract: Monitoring the atmospheric boundary layer (ABL) is a matter of interest for many applications, such as weather forecasting, pollutant-dispersion models and wind energy. The ABL is the most turbulent part of the troposphere, and it is directly affected by the earth's surface characteristics. Thus, monitoring the ABL is a complex task that requires continuous improvement of the remote sensing techniques. This PhD thesis tackles remote sensing as the key technology to assess different ABL parameters in both over-land and over-sea dimensions. The over-land dimension is oriented to the study of the ABL height (ABLH), whereas the over-sea dimension is focused in assessment of surface-layer atmospheric stability from solely wind profiles in the context of wind energy. In the over-land dimension, a synergistic ABLH estimation me\-thod via a combination of microwave-radiometer and lidar-ceilometer-based estimates is presented. The synergistic method uses these two instruments in a cooperative way with the aim of providing an enhanced high-resolution ABLH estimation. Data gathered by multiple remote-sensing instruments during the HOPE campaign at Jülich, Germany, are used to outline the robustness of the synergistic method in relation to estimates which rely on a single instrument. In the over-sea dimension, the 2D parametric-solver algorithm is presented as an alternative method to assess surface-layer parameters from solely floating Doppler wind lidar measurements. Comparative results with reference retrievals from the IJmuiden meteorological mast show that the 2D accurately estimates the friction velocity, and it correctly determines atmospheric stability via its Obukhov length estimation. Accordingly, the 2D algorithm corroborates to stand the floating Doppler wind lidar as the wind-energy-industry preferred solution to replace the off-shore metmast.
  

• BLASCO COLL, ANDREU: Quasi-perfect codes for the classical-quantum channel
  
  Author: BLASCO COLL, ANDREU
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 27/09/2023
  Thesis director: RODRIGUEZ FONOLLOSA, JAVIER
  

  Committee:
       PRESIDENT: CRESPO BOFILL, PEDRO
       SECRETARI: COCCO, GIUSEPPE
       VOCAL: SENTÍS HERRERA, GAEL
  Thesis abstract: Quantum computers use the laws of quantum mechanics to do complex operations that classical computers can't solve. Quantum computers and other physical quantum systems require quantum information to be completely isolated from the environment in order to be perfectly functional. Quantum systems that are not completely isolated suffer from decoherence noise and may suffer from errors. Implementing these systems is a huge challenge and development of suboptimal systems with a low error rate seems to be the best way forward to building these systems.In quantum communications, designing codes that are able to reduce or protect against errors is a necessity. This work focuses on perfect and quasi-perfect quantum codes, which are a family of codes that exists in the classical setting and are optimum in terms of minimizing the error probability for a given number of channel uses. In the first part of the work we generalize the definition of quasi-perfect codes to include both classical codes and quantum codes. We also provide an example of a quantum quasi-perfect code for 2-qubits classical-quantum channels that make use of quantum entanglement and that can be extrapolated to an N-dimensional classical-quantum channel. The second part of this work focuses on quasi-perfect codes in optical communications, where coherent states are used to convey information through an optical channel, known as the Bosonic channel. The Bosonic channel has infinite dimension, so instead we consider a finite-dimensional approximation of the Bosonic channel with a negligible approximation error for a sufficiently large channel dimension. We show that phase-modulated coherent states constitute a codebook that is quasi-perfect for the approximated channel, and thus are close to optimal for the Bosonic channel.The last part of the work focuses on stabilizer error correction codes, which are practical codes that use redundancy to protect against errors. Error correction is not specifically used to transmit classical information, but to protect quantum information instead. However, it is possible that we require to obtain classical information from a quantum state after performing error correction. For these particular cases we may be able to prove that an error correction code is quasi-perfect and thus optimum.
  

• BORRÀS PINO, JORDI: Opportunistic communications in large uncoordinated networks
  
  Author: BORRÀS PINO, JORDI
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 25/01/2023
  Thesis director: VAZQUEZ GRAU, GREGORIO
  

  Committee:
       PRESIDENT: SANTAMARÍA CABALLERO, IGNACIO
       SECRETARI: PASCUAL ISERTE, ANTONIO
       VOCAL: LOPEZ SALCEDO, JOSE ANTONIO
  Thesis abstract: The increase of wireless devices offering high data rate services limits the coexistence of wireless systems sharing the same resources in a given geographical area because of inter-system interference. Therefore, interference management plays a key role in permitting the coexistence of several heterogeneous communication services. However, classical interference management strategies require lateral information giving rise to the need for inter-system coordination and cooperation, which is not always practical.Opportunistic communications offer a potential solution to the problem of inter-system interference management. The basic principle of opportunistic communications is to efficiently and robustly exploit the resources available in a wireless network and adapt the transmitted signals to the state of the network to avoid inter-system interference. Therefore, opportunistic communications depend on inferring the available network resources that can be safely exploited without inducing interference in coexisting communication nodes. Once the available network resources are identified, the most prominent opportunistic communication techniques consist in designing scenario-adapted precoding/decoding strategies to exploit the so-called null space. Despite this, classical solutions in the literature suffer from two main drawbacks: the lack of robustness to detection errors and the need for intra-system cooperation.This thesis focuses on the design of a null space-based opportunistic communication scheme that addresses the drawbacks exhibited by existing methodologies under the assumption that opportunistic nodes do not cooperate. For this purpose, a generalized detection error model independent of the null-space identification mechanism is introduced that allows the design of solutions that exhibit minimal inter-system interference in the worst case. These solutions respond to a maximum signal-to-interference ratio (SIR) criterion, which is optimal under non-cooperative conditions. The proposed methodology allows the design of a family of orthonormal waveforms that perform a spreading of the modulated symbols within the detected null space, which is key to minimizing the induced interference density. The proposed solutions are invariant within the inferred null space, allowing the removal of the feedback link without giving up coherent waveform detection.In the absence of coordination, the waveform design relies solely on locally sensed network state information, inducing a mismatch between the null spaces identified by the transmitter and receiver that may worsen system performance. Although the proposed solution is robust to this mismatch, the design of enhanced receivers using active subspace detection schemes is also studied.When the total number of network resources increases arbitrarily, the proposed solutions tend to be linear combinations of complex exponentials, providing an interpretation in the frequency domain. This asymptotic behavior allows us to adapt the proposed solution to frequency-selective channels by means of a cyclic prefix and to study an efficient modulation similar to the time division multiplexing scheme but using circulant waveforms.Finally, the impact of the use of multiple antennas in opportunistic null space-based communications is studied. The performed analysis reveals that, in any case, the structure of the antenna clusters affects the opportunistic communication, since the proposed waveform mimics the behavior of a single-antenna transmitter. On the other hand, the number of sensors employed translates into an improvement in terms of SIR.
  

• DE CABRERA ESTANYOL, FERRAN: Data-driven information-theoretic tools under a second-order statistics perspective
  
  Author: DE CABRERA ESTANYOL, FERRAN
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 03/07/2023
  Thesis director: RIBA SAGARRA, JAUME
  

  Committee:
       PRESIDENT: RAMIREZ GARCÍA, DAVID
       SECRETARI: FONT SEGURA, JOSEP
       VOCAL: LAMARCA OROZCO, M. MERITXELL
  Thesis abstract: A great deal is known about second-order statistics. For many years, most of the signal processing problems have been addressed under the perspective of the first and second-order moments of the data, known to be optimal under normal conditions. Nevertheless, nowadays data grow in complexity, rendering the second-order approach insufficient. To cope with this, descriptors of data that come from the field of information theory have been utilized in recent years as a substitute for classical second-order methods. Divergence, entropy, and information are the basis of the information-theoretic methods, endowed with the capability of discovering the intricacies of the underlying distributions. However, due to its nonlinear nature and the difficulty of estimating a density function, the estimation and utilization of these measures have also proven to be a difficult task. Meanwhile, the field of machine learning has also advanced toward the analysis of data in a nonlinear fashion. Kernel methods are a primer example of this, procuring an apparently simple way of dealing with nonlinearities, called the kernel ¿trick¿, but concealing a mathematically rigorous background that strengthens the method. In essence, a kernel performs linear operations in a possibly infinite-dimensional feature space without the requirement of explicitly operating in such space. Thanks to this, kernels have the potential to define nonparametric methods that may be unfeasible otherwise. This approach has been used to deal with the aforementioned information-theoretical measures, whose nonlinearity is easily manageable in the feature space. However, its strengths also become its disadvantages. To operate in an unvisited feature space is to lack interpretability. To operate in a high-dimensional feature space is an ingredient for sparsity, requiring regularization. Furthermore, their blind approach often comes at the cost of an increased computational complexity.This dissertation deals with the analysis of complex phenomena embedded in large amounts of data by leveraging well-known second-order statistics tools. This task is performed from two different points of view. In the first part, and following a similar rationale to kernel methods, this thesis develops a framework that is capable of dealing with nonlinearities in a linear fashion. To do so, the data is mapped into a feature space of higher dimensionality than the data space. However, this feature space is neither infinite-dimensional nor unknown, gaining not only in interpretability but also scalability for its use on large data sets. In this space, correlation and covariance are measured with the purpose of estimating measures of information, which constitutes the primary motivation of the mapping. While regularization is still needed in the proposed approach, a consequence of increasing the intrinsic dimensionality of the problem, the deterministic feature space allows the characterization of an appropriate regularization, which ends up exhibiting a strong duality with classical spectral estimation techniques.The second part of the dissertation focuses on the applications of information measures in problems that are typically solved through second-order statistics. Specifically, entropy is an uncertainty measure that provides better granularity of the underlying distribution than the variance. Entropy not only retains the information of first and second-order statistics but also those of higher-order. The resulting methods gain in robustness thanks to this generalization of moments, and at the same time, the information provided by the variance is still discerned. A specific entropy estimator that derives into kernel methods is used for this task thanks to its relationship with U-statistics, which have the advantage of an asymptotic tendency to the sample variance. Consequently, the framework is again rotated, providing a unified rationale of information and second-order statistics.
  

• GONZÁLEZ RODRÍGUEZ, MARTA: Nonlinear modeling and characterization of SAW devices for communications systems
  
  Author: GONZÁLEZ RODRÍGUEZ, MARTA
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 10/02/2023
  Thesis director: COLLADO GOMEZ, JUAN CARLOS | GONZALEZ ARBESU, JOSE MARIA
  

  Committee:
       PRESIDENT: AIGNER, ROBERT
       SECRETARI: GELONCH BOSCH, ANTONIO JOSE
       VOCAL: OLIVARES ROZA, JIMENA
  Thesis abstract: Nowadays, worldwide booming growth in mobile devices puts a lot of pressure on the mobile communications technologies since an enormous amount of requirements, mainly focused on delivering enhanced mobile broadband services to consumers, are needed. The ever-increasing data rate requirements and the support for wireless technologies, like 5th Generation (5G), set a lot of pressure to manufacturers in finding new solutions to face the coexistence and integration of several radio systems operating in the Radio-Frequency (RF) modules.This scenario introduces a variety of challenges that have to be faced when using multi-band operation. One of them is to fight against the desensitization in the RF front-end due to the generation of spurious signals by the nonlinearity of passive components inside the handset. Passive InterModulation (PIM) is becoming a major concern in the design of RF transceivers where the transmitter and receiver share the antenna, since it can cause receiver blocking. PIM might arise from different components such as antennas, mixers, filters, etc. Among the components into the RF chain, the filtering stage is one of the critical components since apart from high selectivity and miniaturization, they also have to meet low PIM specifications and thus, becoming a challenging taskfor RF designers.To face these technological constraints, acoustic wave filters have been giving response to this need because of their outstanding performance, and have become a suitable solution for the emerging communications standards. Bulk Acoustic Wave (BAW) and Surface Acoustic Wave (SAW) are nowadays the main technologies, offering filtering structures with very low insertion losses andgood out-of-band rejection that are in compliance with current system specifications. Despite it seems clear that the acoustic technology shows major advantages, there are some drawbacks too. One of them is that both BAW and SAW resonators exhibit a nonlinear behavior giving place to Intermodulation (IMD) and Harmonic distortion (H). Accordingly, RF front-end high linearization demands may become an issue to be solved in the definition of new advanced services in future standards.There has been a rise in interest in the modeling and simulation of the nonlinearities of SAW devices during the last two decades. Despite different approaches Finite Element Model (FEM), Coupling of Modes (COM) and P-Matrix had been widely used, there is a lack of consensus about the nonlinear generation driven by the difficulty to identify geometry-independent material parameters that could predict the nonlinear behavior of any resonator before manufacturing.To this end, the thesis will be focused on the accurate nonlinear characterization of SAW devices. The modeling and simulation ofnonlinearities on SAW resonators will be the most important milestone of the thesis. Specifically, the development of fundamental circuit models to account for the nonlinear mechanism occurring in SAW resonators and, the implementation of mathematical techniques to synthesize circuital networks based on these models to reduce the computational time to improve the simulation andmodeling of these resonators.The novelty of this thesis lies in the development of a characterization process for SAW resonators allowing to predict the behavior of new devices with other geometries. To be successful in this process, an equivalent nonlinear circuital model is proposed. The developed model is distributed and directly related to the the local constitutive equations of the piezoelectricity. Special efforts areexpended towards developing a new method of analysis for the simulation of both H and IMD generation in SAW resonators and filters. Several experimental verifications have shown that despite of its simplicity, the proposed model is extremely consistent and fast to simulate the linear and nonlinear response of different devices using only a geometry-independent nonlinear parameter.
  

• GUERRA GÓMEZ, ROLANDO: Radio access network optimization with proactive resource management for 5G and beyond
  
  Author: GUERRA GÓMEZ, ROLANDO
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 19/05/2023
  Thesis director: RUIZ BOQUE, SILVIA
  

  Committee:
       PRESIDENT: VALDOVINOS BARDAJÍ, ANTONIO
       SECRETARI: VALENZUELA GONZALEZ, JOSE LUIS
       VOCAL: KARTSAKLI, ELLI
  Thesis abstract: The Fifth-Generation (5G) of cellular networks significantly increases the performance and flexibility of the offered services to users and service providers. The strict network requirement of 5G use cases has been supported by integrating service-based architecture in the core network,flexible radio access network architecture, and implementing numerous wireless technologies. Researchers and Mobile Network Operators (MNOs) face vast challenges not only in the definition process but also in the deployment phase.The research community should define robust and dynamic radio network solutions to tackle the complexity and flexibility of 5G and beyond mobile network requirements. As mentioned, the radio access network architecture has been crucial in defining 5G systems. Especially the Cloud Radio Access Network (C-RAN) architecture has played a fundamental role as part of the new generation radio access network (NG-RAN) because it has the potential to support extremely dense radio network deployments while reducing costs because of the simplification of the radio units. Moreover, C-RAN enhances the network capacity by reducing the number of required resources because it centralizes the baseband functionalities in Baseband Units (BBU) pools or Central Units (CUs), sharing the same resource to manage multiple Remote Radio Heads (RRHs) or Radio Units (RUs). Moreover, Coordinated Multipoint (CoMP), enhanced Inter-Cell Interference Coordination (eICIC), and beamforming technologies could be easily implemented in the C-RAN structure, improving the 5G network performance.However, sustainability and energy efficiency are crucial to support future services and network requirements. Namely, It is fundamental to reduce energy consumption, resource usage, and emissions footprints to avoid excessive power consumption. The enormous increase in the number of devices, data amounts, and data rates implies an increase in the overall data traffic and required capacity, while energy reduction is not automatically guaranteed. On the other hand, the optimal management of the computational resources to satisfy current and future network requirements also becomes a challenge. This doctoral thesis aims to address some of the challenges above. Most of the published research works employ synthetic scenarios to validate the results. A realistic C-RAN platform has been implemented, opposing these approaches. The proposed architecture considers rural and urban zones, heterogeneous deployment with macro and small cells, time-variant traffic patterns, realistic user equipments with guaranteed bit rate and best effort services, Quality of Service (QoS) constraints, a 3D ray-tracing propagation model, multiple frequency bands, different split options, among other significant features. This platform becomes fundamental in the validation of the proposed algorithms.5G and beyond radio network deployment will be ultra-dense. However, optimizing the costs and energy consumption is not automatically guaranteed. For this reason, this thesis also provides a non-linear data modeling and decision-making tool to maximize cost reduction versus coverage-QoS trade-off by optimizing the active RRHs needed according to traffic demands. Besides, it proposes a novel strategy for Dynamic Resource Management with Adaptive Computational capacity (DRM-AC) using Machine Learning (ML) techniques. Three ML algorithms have been considered in the final design after testing multiple approaches: support vector machine (SVM), time-delay neural network (TDNN), and long short-term memory (LSTM). DRM-AC reduces the average of unused resources by 96 %, but there is still QoS degradation when RCC is higher than the predicted computational capacity (PCC). To further improve, two new strategies are proposed and tested in a realistic scenario: DRM-AC with pre-filtering and DRM-AC with error shifting, reducing the average of unsatisfied resources by 98% and 99.9% compared to the DRM-AC.
  

• IBRAHIM MOHAMED BADR, ASMAA: Machine learning algorithms for 5G optical network
  
  Author: IBRAHIM MOHAMED BADR, ASMAA
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 18/07/2023
  Thesis director: PRAT GOMA, JOSEP JOAN
  

  Committee:
       PRESIDENT: URBAN, PATRYK
       SECRETARI: SANTOS BLANCO, MARÍA CONCEPCIÓN
       VOCAL: FÀBREGA SÁNCHEZ, JOSEP MARIA
  Thesis abstract: Throughout this thesis we addressed 5G network challenges. The non-coherent optical modulationtradeoff has been addressed, as we proposed FBMC and artificial intelligence-based schemes. Theproposed schemes have been proved to solve the spectral and the power efficiency trade off in non-coherent optical modulation schemes. Then we addressed the problem of interference management for indoor and outdoor networks. We evaluated the proposed scheme for VLC network and for the front haul optical network. The proposed schemes show significant enhancement in the network behavior regarding power saving and network management. Chapter 2 presented a non-coherent optical modulation transceiver based on artificial neural network and decision regression tree. It is shown that nonlinear regression provides the best system performance, over linear and polynomial regression, as it offers betterfeature extraction. While the transceiver based on decision regression tree eliminates the clippingdistortion produced by clipping the transmitted signal over optical channel. The proposed transceiver overcomes the tradeoff between the spectral and the power efficiency of the noncoherent optical modulation, moreover it shows better performance and enhanced BER for high subcarrier spacing. On the other side, reducing the subcarrier spacing highly influences the RDT scheme, as it increases the BER and the complexity of the scheme. It is shown that the AI based transceiver enhances the BER of the DCO-OFDM, as the BER reaches 10^-3 at 5 db SNR with the same spectral efficiency. While in chapter 3, the optical ACO-FBMC scheme for direct detection modulation was presented. We have shown that the proposed scheme eliminates self-frame interference and suffers from inter-frame interference. Interframeinterference is eliminated using the proposed iterative receiver. Also, the ACO-FBMC enhances the BER performance of the ACO-OFDM with the perfect rectangular pulse shaping and eliminating the emission of the filter bank out of the band. Our system model has higher spectral efficiency than the classic ACO-OFDM, as FBMC shows better spectral efficiency by removing the guard interval. Moreover, it has been shown that the ACO-FBMC with 8 overlapping factors improves the BER performance of the ACO-OFDM by 4 dB due to the perfect rectangular pulse shaping and the elimination of the out-band emission of the filter bank. In chapter 4, we addressed the problem of interference management in a VLC indoorsystem with multi-user access. The performance of the system applying the SRF technique compared toUFR and PFR. The results showed that the proposed approach improves system performance in terms of total system throughput, outage probability, and SINR. It solves the problem of high SINR at the cell edge as experienced by UFR and improved the overall system throughput as compared with PFR. In chapter 5, we proposed RRH-BBU assignment based on clustering algorithm that targets minimizing the power consumption and the inter BBU handover. The proposed algorithm computes the required number of installed BBUs to accommodate the maximum traffic load, deploys time series clustering as temporal clustering method, and applies DBSCAN algorithm to divide each temporal cluster into several spatial cluster based on the cell location. Then the problem of assigning RRH of each cluster is described as a binpacking optimization problem to find the optimum number of BBUs for each cluster. The proposedalgorithm has been validated using real world CDR of Milan city and it is verified the published Milanland use map. The inter BBU handover signals have been enhanced by assigning near RRHs to the samespatial cluster and same BBU, to avoid inter BBU handover. It is shown that the algorithm reduces the total power consumption of the current deployed network by 28.8 %, by assigning all the active RRHs tocertain BBUs based on the traffic load and switching off the unassigned BBUs.
  

• LOPEZ BUENO, DAVID: Machine learning techniques for adaptive polynomial and neural network digital predistorters
  
  Author: LOPEZ BUENO, DAVID
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 07/07/2023
  Thesis director: GILABERT PINAL, PERE LLUIS | MONTORO LOPEZ, GABRIEL
  

  Committee:
       PRESIDENT: QUAGLIA, ROBERTO
       SECRETARI: MATEU MATEU, JORDI
       VOCAL: MADERO AYORA, MARIA JOSÉ
  Thesis abstract: The power amplifier (PA) is a core element in the radio transmitters to support the required mobile and fixed broadband communication link ranges. However, the PA is a power-hungry and nonlinear by nature device. Under spectrally efficient wideband modulated waveforms with high peak-to-average power ratio, the PA energy efficiency is significantly decreased since back-off operation is needed to meet the transmission quality requirements. Moreover, when employing highly efficient amplification architectures, like Doherty, load modulated balanced amplifier (LMBA) or envelope tracking (ET) PAs, the added distortion is left as an issue to be addressed at system level by a linearizer. In this context, the closed-loop adaptive digital predistorter (DPD) is a key component of the digital front-end (DFE) to counteract the PA nonlinear response under varying conditions and to cope with the inherent trade-off between linearity and efficiency. According to the fifth generation (5G) and beyond communication technologies and the proposed radio transmitter and PA architectures, the DPD may have to deal with strong nonlinearities and memory effects, in-phase and quadrature (IQ) modulator imbalances and DC offsets, additional PA supply or load modulation distortion, and multi-antenna PA input and output cross talk and beam-dependent effects. Such impairments degrade the radio access network (RAN) energy efficiency, capacity, and the number of potential RAN users due to the increased in-band and out-of-band distortion. The adaptive DPD can overcome such undesired effects but faces relevant obstacles. At every new generation of mobile communication systems, the signal bandwidth is increased and the DPD needs to be operated at higher speed. The DPD challenges are twofold. On the one hand, combining massive bandwidth operation together with handling complex multi-dimensional effects may increase exponentially the complexity of the DPD and make it both commercially unaffordable and energy inefficient due to the increased cost and power consumption at the DFE and data conversion stages. On the other hand, the adaptive DPDs need significantly larger training periods to compensate for all the undesired effects. In line with the above-mentioned challenges, the research presented in this dissertation aims at guaranteeing best DPD linearity versus efficiency trade-off in complex nonlinear scenarios, by leveraging on efficiently deployed machine learning (ML) and artificial intelligence (AI) techniques to reduce the computational complexity of DPD modeling and identification at the DFE, guaranteeing well-conditioned and robust DPD estimation, and drastically reducing the DPD training times while meeting performance requirements. To accomplish that, several newly applied and customized ML feature selection and feature extraction dimensionality reduction techniques are combined with new training data length reduction schemes, to ensure both reduced DPD behavioral modeling matrices and input datasets in single-antenna and multi-antenna adaptive polynomial and neural network DPD architectures, respectively. To validate the benefits of these contributions in accordance with the previous goals, all these techniques have been deployed and thoroughly benchmarked under adverse conditions in realistic laboratory test benches.
  

• MANSO FERNÁNDEZ ARGÜELLES, CARLOS AGUSTÍN: Cloud-native orchestration and automation for disaggregated networks
  
  Author: MANSO FERNÁNDEZ ARGÜELLES, CARLOS AGUSTÍN
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 18/05/2023
  Thesis director: MUÑOZ GONZALEZ, RAUL | VILALTA CAÑELLAS, RICARD
  

  Committee:
       PRESIDENT: CALLE ORTEGA, EUSEBI
       SECRETARI: COMELLAS COLOME, JAUME
       VOCAL: GONZÁLEZ DÍAZ, SERGIO
  Thesis abstract: Transport networks are segmented by different technologies and domains, what makes difficult automated end-to-end operations and making direct human intervention needed to deploy connectivity services.On top of that, datacenter operators are achieving efficiency and cost reduction by decoupling the software from the hardware, using white-box hardware with open Application Programming Interfaces (APIs), enabling more customization and vendor competition. Still, there are no clear standard data models that describe the device capabilities, attributes, operations and notifications, as well as efficient transport protocols that provides primitives to view and manipulate the data.Moreover, the growth of demanded by users, threaten to exhaust the capacity of Wavelength Division Multiplexing (WDM) optical networks. Extending the spectrum of use can be a short term solution, but in the long term, Spatial DivisionMultiplexing (SDM) needs to be deployed to keep up with capacity demands.The first objective is to provide network control to multi-layer multi-domain disaggregated packet optical networks. A control architecture for partially disaggregated optical networks is presented, based on a Software Defined Networking (SDN) controller that is able to controll them. It uses an Open Line System (OLS) controller to manage the optical line, using standard interfaces, and open transponders. To alleviate part of this complexity, an architecture for the orchestration of multi-domain multi-layer, packet and optical networks is also presented. The main idea is orchestrating the packet and opticaldomains using an agnostic centralized orchestrator that is only responsible for domain selection of multi-domain paths, wrapping the underlying domains with SDN controllers with standardiet interfaces. The deployment of SDM links betweenoverloaded WDM nodes is proposed to alleviate links that are reaching full capacity. The presented target architecture consists of OLS controlled domains for WDM and SDM and open transponders following the disaggregated approach. These architectures are demonstrated in real optical testbeds.The second objective is to present an architecture than can keep up with the centralization and the complexity that the SDN approach comes with. A cloud-native architecture for SDN controllers that is able to cope with the complexity and size oftransport networks is presented, based on the micro-services software architecture, that allows for self-healing infrastructure, independent auto scaling of micro-services and autonomous deployment and development of each module.Then, the same micro-service architecture is updated with a solution to scale the database, replicating the micro-service.Data coherence must be kept at all times, and micro-services must be aligned so there is no data corruption or misalignment. This is done using NewSQL databases, included in the architecture.The final objective deals with an architecture that joins the data gathering, training of models, and execution, needed to feed data to support multiple operations in the zero-touch management approach. A telemetry-enabled SDN controller architecture is shown, using novel, open, low-latency, and low-overhead telemetry protocols, with a demonstration of it's scalability. The telemetry system is used to provide the deployment of SDM links between WDM nodes. The proposed architecture also allows dynamic provisioning and reconfiguration of the VNT in case of failure or changes in the requested capacity. The SDN centralization allows improved data gathering from all the segments it controls. This way, machine-learning algorithms can benefit from it, getting access to easy data to train their models. An architecture that joins the data gathering, training of the models, and execution, capable of improving multiple operations is presented and showcased with a Quality of Transmission (QoT) predictor using machine-learning.
  

• MAULE, MASSIMILIANO: Dynamic resource optimization and orchestration techniques for 5G new radio and beyond
  
  Author: MAULE, MASSIMILIANO
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 16/06/2023
  Thesis director: VERIKOUKIS, CHRISTOS | VARDAKAS, JOHN
  

  Committee:
       PRESIDENT: KSENTINI, ADLEN
       SECRETARI: ADELANTADO FREIXER, FERRAN
       VOCAL: LOGOTHETIS, MICHAEL
  Thesis abstract: Earmarked as the revolutionary 5G key enabler, Network Slicing (NS) is the embodiment of the concept of running multiple logical networks as virtually independent business operations on a common physical infrastructure in an efficient and economical way[2]. NS enables the sharing of 5G RAN functional elements and the Transport Network (TN), securing the effective allocation andprioritization of the limited resources available, and offering to the customer improvement in service flexibility and scalability. By combining 5G and NS solutions, Service Providers (SPs) will pave the ways to cutting-edge industry fields such as Massive IoT, high resolution video on-demand services, smart manufacturing, and advanced solutions like Augmented Reality (AR), Virtual Reality (VR) and cloud gaming, gaining access to potential new revenue sources and smarter solutions to support end customers[3].This dissertation provides a contribution to the design, analysis, and evaluation of novel multi- tenant RAN NS techniques for the dynamic orchestration of the radio resources in 5G NR. Our research aims to define in real-time the optimal resources¿ allocation per slice, able to overcome the resources¿ under-over provisioning issue, by exploiting the latest 5G NR features and flexibilityprinciples of the 5G infrastructure. All the proposed mathematical models have been extensively validated using the 5G simulation platforms and\or real 4G-5G testbed configurations. The main thesis contributions are divided into two parts. In the first part, starting from a common baseline scenario, four different resource orchestration frameworks are presented, where the optimization problem is gradually refined through the exploitation of distinct mathematical models, 5G features, and metrics. In the second part, the design of a novel Open-RAN (O-RAN) Functional Split (FS) architecture for Software Defined Radio (SDR) has been proposed;this innovative concept represents a step forward to the creation of a shared RAN environment for the fair coexistence of multivendor solutions, as massively promoted in 5G. During the elaboration of this thesis, two general key conclusions have been extracted. First, higher performance, system stability, and advanced service customization can be achieved using real-time NS in the RAN, outperforming the current state of the art limitations. This is possible through the new set of capabilities, sharing principle, and infrastructure scalability introduced in 5G NR. Second, we highlight the role of virtualization\softwarization of the network functionalities in 5G, illustrating the advantages of a shared infrastructure compared with a single vendor approach. [2] GSMA Association, ¿An Introduction to Network Slicing¿, White Paper, 2017.2GSMA Association, ¿An Introduction to Network Slicing¿, White Paper, 2017. [3] Ericsson, ¿5G RAN Slicing: Capture new business revenues in the 5G era¿, Ericsson Business Review, October 2021.
  

• MONTERO BAYO, LUCA: 5G and its impact on the automotive industry
  
  Author: MONTERO BAYO, LUCA
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 21/09/2023
  Thesis director: JOFRE ROCA, LUIS
  

  Committee:
       PRESIDENT: SIERRA CASTAÑER, MANUEL
       SECRETARI: AGUASCA SOLE, ALBERTO
       VOCAL: MERLANO DUNCAN, JUAN CARLOS
  Thesis abstract: The 5th generation of mobile communications has been designed to address the unstoppable demand of data bandwidth. However, it also gives support to a range of vertical industries with different Quality of Service demands, such as the automotive industry. The automotive industry is undergoing a significant transformation in response to the changing needs of consumers and the advances in Advanced Driver Assistance Systems, catalyzing the development of autonomous driving and redefining the service portfolio of traditional automakers.The next milestone of the industry is the widespread deployment of Vehicle to Everything (V2X) technologies, which aim to connect the vehicle to its neighboring road users. V2X stands as a promising enabler of use cases that can increase driver awareness, extend the perception of sensors beyond line of sight, and have an impact on overall traffic efficiency. This thesis covers the state of the art of V2X technologies, identifying the biggest challenges and putting the performance of current standards to a test. The actual game changer of V2X is the incorporation of 5G features for vehicle connectivity. Vehicles can then make use of ultra-reliable low-latency mechanisms and new frequency bands to enable a set of advanced use cases that assist autonomous decision-making and make reliable autonomous driving a reality. This thesis also covers the implications of multi-element, beamforming antenna systems to give support to these 5G features and the performance they promise to deliver. Accounting for the paradigm shift towards beam-based vehicular communications, this thesis makes an emphasis on several specification and research challenges, such as beam management, which are thoroughly assessed. As such, this thesis sheds light into the inner workings of 5G-V2X and points its biggest white spots to eventually enable the autonomous vision for 5G and beyond.
  

• MOSELLA MONTORO, ALBERT: Graph convolutional neural networks for 3D data analysis
  
  Author: MOSELLA MONTORO, ALBERT
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 22/02/2023
  Thesis director: RUIZ HIDALGO, JAVIER
  

  Committee:
       PRESIDENT: SMOLIC, ALJOSA
       SECRETARI: MARQUES ACOSTA, FERNANDO
       VOCAL: HARO ORTEGA, GLORIA
  Thesis abstract: Deep Learning allows the extraction of complex features directly from raw input data, eliminating the need for hand-crafted features from the classical Machine Learning pipeline. This new paradigm brought a boost in the performance across several domains, including computer vision, natural language processing and audio processing. However, there are still challenges when dealing with unorganized structures. This thesis addresses this challenge using Graph Convolutional Neural Networks, a new set of techniques capable of managing graph structures that can be used for processing 3D data. The first part of the thesis focuses on the Graph Analysis task, in which we will study the capabilities of Graph Convolutional Neural Networks to capture the intrinsic geometric information of 3D data. We propose the Attention Graph Convolution layer that learns to infer the kernel used during the convolution, taking into account the particularities of each neighbourhood of the graph. We explore two variants of the Attention Graph Convolution layer, one that explores a residual approach and another one that allows the convolution to combine different neighbourhood domains. Furthermore, we propose a set of 3D pooling layers that mimics the behaviour of the pooling layers found in common 2D Convolutional Neural Networks architectures. Finally, we present a 2D-3D Fusion block capable of merging the 3D geometric information that we get from a Graph Convolutional Neural Network with the texture information obtained by a 2D Convolutional Neural Network. We evaluate the presented contributions on the RGB-D Scene Classification task. The second part of this thesis focuses on the Node Analysis task, which consists of extracting features on a node level, taking into account the neighbourhood structure. We present the Multi-Aggregator Graph Convolution layer that uses a multiple aggregator approach to better generalize for unseen topologies and learn better local representations. In addition, it reduces the memory footprint with respect to the Attention Graph Convolution layer. Finally, we analyze the capabilities of our proposed Graph Convolution layers to deal with heterogeneous graphs where the nodes of the graph may belong to different modalities. We evaluate the presented contributions with the Computer Graphics process of skinning a character mesh. Specifically, we propose a Two-Stream Graph Neural Network capable of predicting the skinning weights of a 3D character.
  

• NICOLÁS ÁLVAREZ, JORGE: Interferometric Orbit Determination for Geosynchronous Earth Sensing Missions
  
  Author: NICOLÁS ÁLVAREZ, JORGE
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 16/05/2023
  Thesis director: BROQUETAS IBARS, ANTONI | AGUASCA SOLE, ALBERTO
  

  Committee:
       PRESIDENT: LÓPEZ SÁNCHEZ, JUAN MANUEL
       SECRETARI: COMERON TEJERO, ADOLFO
       VOCAL: MAKHOUL VARONA, EDUARDO
  Thesis abstract: Future Geosynchronous Synthetic Aperture Radar (GEOSAR) missions will provide permanent monitoring of continental areas of the planet with revisit times of less than 24 h. Several GEOSAR missions have been studied in the USA, Europe, and China with different applications, including water cycle monitoring and early warning of disasters. GEOSAR missions require unprecedented orbit determination precision in order to form focused SAR images from Geosynchronous Orbits (GEO). A precise orbit determination technique based on microwave interferometry is proposed.An interferometric orbit determination system has been designed and implemented in order to acquire experimental phase observations from which the trajectory of the satellite can be estimated. The technique presents the capacity for tracking illuminators of opportunity, allowing interferometry to be tested without launching any new spacecraft. Multiple experimental campaigns are carried out using the signals of opportunity from the satellites of the Astra 19.2oE constellation.Since the measurement sensitivity of the interferometer increases with the length of the baseline, a signal relay strategy is proposed in order to extend the baseline while keeping all the receivers together, sharing a common clock reference. The use of passive reflectors in the near field of the secondary receivers forms a compact interferometric baseline of 15~m. The interferometer uses correlation techniques to operate with arbitrary transmitted signals. The correlator's high processing gain allows the system to effectively track weak signals well below the noise level. Thus, some buildings found in the vicinity of the campus are used as reflectors of opportunity, providing a weak satellite signal scattered in the direction of the receiver antennas,forming large interferometric baselines of up to 1200 m.An error model is developed in order to estimate the expected orbit determination precision from a set of interferometric phase observations. It considers the most important perturbations affecting a microwave interferometer, such as the tropospheric and ionospheric perturbations, the transmission line errors, the system's temperature differences, the absolute phase ambiguity, and the uncertainty in the receivers positioning. This model allows to establish the requirements and to configure the settings of the tracking system according to the needs of the space mission under consideration.The relative phases measured between the receivers are used to estimate the satellite position. The experimental results prove the technique is able to track GEOSAR satellites based on their transmitted signals. An interferometer with three baselines of 15m, 300 m, and 1200 m uses the shorter baseline to solve the absolute phase ambiguity and the longer ones to retrieve the trajectory of the satellite with precision. The resulting orbit determination error with respect to the true trajectory is estimated to be in the order of 400 m in an urban environment due to the uncertainty of the position of the distributed reflectors of opportunity.The precision would improve substantially with the installation and precise geodetic location of dedicated metallic reflectors. This result cannot be confirmed due to the lack of an accurate ground truth, but it is consistent with the expected orbit determination precision computed with the error model.Finally, the echoes resulting from the scattering of GEO satellite transmissions on the surrounding urban structures and mountains are processed in order to form SAR images of Barcelona. The images were formed with the estimated trajectoryinformation provided by the large baseline interferometric orbit determination system, proving their performance is valid for GEO remote sensing missions to form focused SAR images.
  

• OJAGHI KAHJOGH, BEHNAM: Converged RAN/MEC slicing in beyond 5G (B5G)Networks
  
  Author: OJAGHI KAHJOGH, BEHNAM
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 13/07/2023
  Thesis director: ADELANTADO FREIXER, FERRAN | VERIKOUKIS, CHRISTOS
  

  Committee:
       PRESIDENT: PALAU SALVADOR, CARLOS ENRIQUE
       SECRETARI: SANCHEZ GONZALEZ, JUAN
       VOCAL: GELABERT DORAN, XAVIER
  Thesis abstract: The main objective of this thesis is to propose solutions for implementing dynamic RAN slicing and Functional Split (FS) along with MEC placements in 5G/B5G. In particular, this thesis is divided into three parts. In the first part (Chapter 3), we model a joint slicing and FS optimization in the 5G RAN with the objectives of optimizing the centralization degree and throughput.In this work, the RAN slicing allowed a customized FS deployment per slice, thus optimizing the available resources, e.g., transport network capacity and Remote Radio Head (RRH) or Central Unit (CU) computational capacity. Next, we present the second part in Chapter 4 by extending the first work by proposing SlicedRAN: service-aware network slicing framework for 5G RAN to create isolated RAN slices based on the service requirements with customized functional splits per slice. The proposed framework investigates the bottlenecks in the capacity of RRHs Fronthaul/Backhaul (FH/BH) network capacity along with a minimum level of Service Level Agreement (SLA) for each slice imposed by the different service types. Finally, in the last part presented in Chapter 5, we investigate dynamic RAN/MEC slicing framework in Open-RAN (O-RAN) architecture to dynamically place the RAN protocol stack of Virtual Network Functions (VNFs) and MEC server per slice. This framework contains the bottlenecks in the capacity of Open-RAN Radio Units (O-RUs), MEC server computation capacity, together with a customized FS per slice, to jointly solve the challenge of operating cost-efficient edge networks and maintaining the served traffic with various QoS criteria. We use a robust Benders decomposition algorithm, which reduces the computation complexity while ensuring an exact and optimal global solution. The proposed algorithm successfully optimizes the joint throughput and system cost in various traffic scenarios while satisfying QoS criteria, as shown by trace-driven simulation results. Hence, in order to determine the right MEC settings for on-demand traffic and alter the MEC type to satisfy the QoS requirements of various User Equipment (UEs) belonging to different slice types, we explore the compute and storage capacity for MEC services such as Enhanced Mobile Broadband (eMBB) and ultra-Reliable and Low-Latency Communications (uRLLC). The overall conclusion of the present findings demonstrates a trade-off between the throughput attained and the cost incurred to the network. As a result, we investigate multi-objective optimization to construct slices while optimizing throughput and decreasing computational cost objectives, and we compare its performance to that of a single objective (maximizing throughput). The findings demonstrate that a throughput increase of up to 160% can be made possible by increasing 78% in the computation cost for a single objective when compared with multi-objective without prioritization. In addition, comparing a single objective with a multi-objective with priority in throughput, it increases throughput by up to 82% and adds 17% to computation costs. Consequently, a single objective of maximizing throughput can result in high throughput at the expense of high cost. It is possible to achieve almost half the amount of throughput using multi-objective with prioritization in throughput, whereas costs can be reduced five-fold.
  

• PEREA ROBLES, RAFAEL: Novel transversal topologies and coupled resonator configurations for acoustic wave filters
  
  Author: PEREA ROBLES, RAFAEL
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 09/06/2023
  Thesis director: MATEU MATEU, JORDI | COLLADO GOMEZ, JUAN CARLOS
  

  Committee:
       PRESIDENT: AIGNER, ROBERT
       SECRETARI: GILABERT PINAL, PERE LLUIS
       VOCAL: VILLANUEVA TORRIJO, LUIS GUILLERMO
  Thesis abstract: During the last years, electro-acoustic technology has been a key factor in the development of portable devices thanks to its high performance and very compact filtering structures. Such a technology has enabled the inclusion of several systems and standards in a single device.Specifically, with the introduction of the new 5G and the carrier aggregation techniques, today's handset devices might have more than 50 RF filters to support usage in countries across the world. As a matter of fact, the expectation is that these numbers increase over the future.The new generation of communication standards calls for very wide bandwidths of operation and higher data rates. These requirements impose the development of ultra-wideband filters that can provide outstanding performance in terms of low loss, high rejection and multifrequency operability in the smallest possible footprint.Ladder filter topology has been the preferred one for the development of filters in the past generations of standards, since it provides very high selective filters with low insertion loss levels. However, the maximum achievable bandwidth is limited to the electro-acoustic coupling coefficient, the position of the transmission zeros depends on the resonant frequencies of the resonators and itsout-of-band behavior is determined by the capacitance ratio between resonators. These shortcomings could become a bottleneckfor the forthcoming stringent specifications.In a recent work, a new transversal topology has been introduced that offers a high degree of flexibility in the design of acoustic filters and it has proven to solve some of the limitations of the ladder topology. Nevertheless, its differential behavior requires of a balun stage to properly work. Moreover, some circuital transformations that are carried out in the current synthesis procedures have some limitations when ultra-wideband filters are targeted.The aim of this work is to provide novel solutions that overcome the existing limitation of the current filter topologies in the state-of-the-art. Thereby, contributing with filter synthesis procedures that provide filters with larger relative bandwidths, higher rejection and a higher degree of miniaturization. On the one hand, a new synthesis procedure based on acoustic transversal filters for ultra-wideband filters is presented which culminates with the manufacturing of a real prototype with 24 % of fractional bandwidth operating at the N77 band. Moreover, advanced filtering responses based on multifiltering schemes for transversal topology are also analyzed. On the other hand, the concept of transversal topology is applied to acoustically-coupled structures: Stacked Crystal Filters and Coupled Resonator Filters (CRF). The extension of the transversal topology to these two configurations will allow to remove the balun stage of the convential acoustic transversal filters and also to provide a higher level of miniaturization. Finally, a new synthesis procedure for the development of fourth-order acoustic CRF structures from the mathematical formulation to the real layer configuration is presented. This might be a key factor for the development of the next generation of filters, since it could be mixedwith ladder and transversal topologies and give rise to advanced responses with improved performance, as well as with a further degree of miniaturization.
  

• SAFARI, POOYAN: Unsupervised and attention approaches for deep learning speaker recognition
  
  Author: SAFARI, POOYAN
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 19/05/2023
  Thesis director: HERNANDO PERICAS, FRANCISCO JAVIER
  

  Committee:
       PRESIDENT: LLEIDA SOLANO, EDUARDO
       SECRETARI: RODRIGUEZ FONOLLOSA, JOSE ADRIAN
       VOCAL: DOCÍO FERNÁNDEZ, LAURA
  Thesis abstract: The thesis presents various contributions to the field of speaker recognition. In the first part of the thesis, the focus is on unsupervised methods for speaker recognition. This includes a method that uses Deep Belief Networks (DBN) that is capable of handling a large number of impostor samples. Since the number of samples for each destination speaker is different, the training process is challenging, but we successfully overcome this hurdle using unsupervised learning to train a universal DBN (UDBN) and then adapting it to data for each target speaker. In the same direction, we present a new framework for speaker recognition based on Restricted Boltzmann Machines (RBM). The proposed solution, named RBM-vector, maps the spectral characteristics of the speaker to a single fixed-dimensional vector carrying the speaker-specific information. The framework uses the unsupervised learning capability of RBM to train a global model called Universal RBM (URBM), which is then fitted to the data for each speaker in the development, enrollment, and evaluation datasets. The adapted RBMs are concatenated, subject to dimension reduction, and whitened to generate speaker vectors. Evaluation on the NIST SRE 2006 database shows that RBM vectors outperform i-vectors in terms of EER by 15% using cosine scoring. Score fusion with i-vectors produces a relative improvement of more than 24%. The unsupervised nature of the RBM-vector and i-vector approaches make them a useful alternative to the i-vector/PLDA approach in scenarios where no labeled data is available. The focus of the second part of the thesis is on supervised methods for speaker recognition. Our first attempt tried to address the limitations of mobile devices, such as storage, processing power, memory, and power consumption, which have motivated researchers to design more efficient deep learning models. We proposed a new approach called the tandem Self-Attention Encoding and Pooling (SAEP) mechanism, inspired by the self-attention networks of the Transformer architecture. SAEP is a stack of blocks based on self-attention and positional feed-forward networks that create a vector tor representation of speakers from speech utterances of non-fixed length. This approach encodes short-term spectral features into speaker embeddings that can be used in text-independent speaker verification. We tested this approach on VoxCeleb1 and 2 datasets and found that it exceeds the benchmark x-vector and is competitive with some other benchmarks based on convolutions while shrinking the model size significantly. Compared to ResNet-34, ResNet-50 and x-vector, it uses 94%, 95% and 73% fewer parameters, respectively. Recently, it is common to use large self-supervised language models for speech recognition tasks. These models can be fine-tuned for specific tasks like speaker verification. Typically, these models are based on Self-Attention Networks (SANs). To explore the potentials and challenges of using these models for speaker verification, we propose a SAN-based speaker embedding extractor that can create a vector representation of a speaker from speech utterances of non-fixed length. We made some architectural modifications to the SAEP architecture to improve its performance and could achieve a relative improvement of 41% in terms of EER. The role of data augmentation was also studied. We addressed the training instability in these architectures in terms of rank collapse and proposed potential solutions to these shortcomings. The approach was tested on both VoxCeleb1 & 2 datasets.
  

• SALCEDO BOSCH, ANDREU: Artificial intelligence, lidar and co-operative remote sensing for atmospheric observation and off-shore wind energy
  
  Author: SALCEDO BOSCH, ANDREU
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 30/06/2023
  Thesis director: ROCADENBOSCH BURILLO, FRANCISCO
  

  Committee:
       PRESIDENT: BAY HASAGER, CHARLOTTE
       SECRETARI: BALDASANO RECIO, JOSE M.
       VOCAL: O\'CONNOR, EWAN JAMES
  Thesis abstract: Remote sensing of the atmosphere is widely used by the wind energy industry to both assess future wind farms deployment sites as well as to improve their operation. With the rising interest in offshore wind energy, remote sensing of the atmosphere has become essential in offshore deep-sea sites in order to reduce deployment and operation costs. Particularly, floating LiDARs have become the de-facto instrument for offshore wind resource assessment due to its flexibility and capabilities to measure the wind with equivalent accuracy as meteorological met-masts in a cost-effective manner. The main goal of this Thesis is to study and exploit the potentialities of existing atmospheric remote sensing instruments, with special emphasis on floating Doppler wind LiDARs. Towards this purpose, different signal processing and machine learning solutions are proposed and analysed. First, the correction of the effect of vertical wind on micro-rain-radar measurements is tackled by means of inverse methods. Second, the capabilities of floating LiDARs to retrieve ocean-related parameters is studied. To that end, signal processing techniques based on spectral analysis of the buoy's motion are used to characterize the ocean waves period. Third, and core part of this Thesis, the motion-induced error of floating-LiDAR measurements of the wind is studied in terms of estimation and compensation. Regarding the former, a novel analytical formulation to estimate horizontal-wind-speed bias and turbulence-intensity-increment error products is presented. The latter topic is tackled using machine learning techniques, specifically, an Unscented Kalman filter for motion compensation of floating-Doppler-wind-LiDAR measurements is presented, and its performance is analyzed under different wave and atmospheric scenarios.The presented methodologies are validated against reference fixed LiDARs and anemometers in the context of two measurement campaigns: "Pont del Petroli" and IJmuiden campaigns. Data clustering techniques are used to assess the quality of the retrieved data products under different scenarios of interest for the industry. The results attained by the novel solutions presented here further demonstrate the capabilities of floating Doppler wind LiDARs for off-shore wind monitoring, which strengthens their position as key remote-sensing instruments for the off-shore wind energy industry.
  

• SARRIGIANNIS, IOANNIS: SFC Placement and lifecycle management in edge-enabled 5G architectures
  
  Author: SARRIGIANNIS, IOANNIS
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Reading date: 10/02/2023
  Thesis director: ANTONOPOULOS, ANGELOS | RAMANTAS, KONSTANTINOS
  

  Committee:
       PRESIDENT: PEREZ ROMERO, JORGE
       SECRETARI: SIOKIS, APOSTOLOS
       VOCAL: FIORE, MARCO
  Thesis abstract: The fifth generation (5G) of mobile communications urges software defined networking (SDN) and network function virtualization (NFV) to join forces with the multi-access edge computing (MEC) cause. Thus, reduced latency and increased capacity at the edge of the network can be achieved, to satisfy the requirements of a diverse ecosystem where multiple virtualization technologies (VTs) may be employed. 5G service providers highly rely on network softwarization for addressing the latency and resource demanding use cases of the 5G vertical industries, where both applications and network functions are incorporated into virtual network functions (VNFs). If not properly orchestrated, the flexibility of deployment, placement and lifecycle management (LCM) that the VNFs manifest, may cause serious issues in the NFV scheme. As the service level agreements (SLAs) of the 5G applications compete in an environment with traffic variations and VNF placement options with diverse compute and network resources, online placement techniques and advanced LCM approaches become mandatory.The local breakout that MEC-enabled architectures offer, signify that the data will not have to cross the entire network until they reach the application and return to the user, as the application is running at the MEC that is, usually, collocated with the access network.In this thesis, we tackle the challenges that arise in core and edge-enabled 5G architectures, and we elaborate how the different schemes of VNF deployments as VTs can be used and collaborate to support the automotive and Internet of things (IoT) use cases, as well as more demanding use cases that derive from the combination of various vertical industries. We go beyond the current state-of-the-art solutions by proposing innovative resource allocation and LCM-enabled scheduling algorithms. Furthermore, we focus on the challenges that arise in single-domain or federated environments, where the flexible placement and LCM of VNFs is supported by the NFV orchestrator (NFVO) that is able to manage, on-the-fly, the network functions and resources. Additionally, we deal with the limitations of the intelligence of the NFVO by providing service aware latency-based embedding and placement mechanisms. Moreover, we propose online scheduling and LCM algorithms where the VNFs are instantiated, scaled, migrated and destroyed based on the actual traffic, respecting the SLA of the 5G use cases, as well as the overall deployment and execution cost.Our work is supported by our versatile, open-source and custom-built 5G experimental platform, modified and adapted at each architecture to support the corresponding 5G use cases. The experimental results demonstrate the efficiency of our innovative algorithms and their efficacy to deal with the VNF placement and resource reallocation and optimization problems in actual demanding environments with unpredictable traffic schemes.Our methods allow the maximization of the total number of users served and the adaptation to real-time incoming traffic. At the same time, the application SLAs are respected in a cost-efficient way.
  

• ZHOU, IVAN: Technologies for injection molded antennas for mass production
  
  Author: ZHOU, IVAN
  Thesis link: http://hdl.handle.net/10803/688924
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Article-based thesis
  Reading date: 19/01/2023
  Thesis director: ROMEU ROBERT, JORDI
  

  Committee:
       PRESIDENT: BAQUERO ESCUDERO, MARIANO
       SECRETARI: BLANCH BORIS, SEBASTIAN
       VOCAL: SEGOVIA VARGAS, DANIEL
  Thesis abstract: The deployment of 5G antenna infrastructure and the mandatory adoption of anti-collision radars for automotive cars will require large amount of antennas operating in the millimeter and sub-millimeter wavelength. These antennas are usually arrays and the possibility to manufacture the antenna array including the feeding network and the radiating element as a plastic piece reducing the need to use large (Printed Circuit Boards) PCB¿s on expensive dielectric substrates, can be an interesting manufacturing technology. In this regard, waveguide-based antennas can be assembled using plastic technology with a proper metallization procedure. They are more scalable in terms of efficiency than microstrip line (ML) antennas and as the number of antennas in the array increases the gain is not reduced due to the losses in the substrate. In this thesis, the industrial challenges of this technology are addressed. A detailed tolerance study by including the plastic manufacturing errors, typically +-0.1mm, is carried out in order to check the feasibility of plastic antennas to address mass production. The antennas will need to be integrated with the radar chipsets, so a transition between the chip and the waveguide-antennas will be presented. These transitions can act as a direct chip-waveguide launcher, potentially reducing the need of using large substrates, hence reducing the cost of the antenna. Also, the need to apply metal coating is also explored to achieve the desired performance. Conventional techniques such as copper electrodeposition is used. The main drawback is that the copper has a lot of difficulties depositing into right angle surfaces. Eventually, these antennas will have to be integrated in the aesthetics of a car, usually behind a plastic radome (with its respective manufacturing errors as well) that will need to be designed and optimized properly in order to introduce the minimum distorsions to the radar. Optimization based on simulators done with commercial electromagnetic softwares like CST is not feasible due to the required large computation time. In this regard an ad-hoc ray-tracing based simulator has been developed to asses radome induced errors in radar performance. All these industrial problems are taken into account from the design stage where the time, price, fabrication tolerances and radiation requirements have to be compromised at the same time increasing dramatically the design complexity.
  

Last update: 04/10/2023 05:01:11.

Research groups

• ANTENNALAB-Antennas and Wireless Systems Laboratory
• CommSensLab-UPC-Centre Especific de Recerca en Comunicacio i Deteccio UPC
• CSC-Components and Systems for Communications Research Group
• GCO-Optical Communications Group
• GPI-Image and Video Processing Group
• GRCM-Mobile Communication Reserach Group
• RF&MW-Laboratory of RF & microwave systems, devices and materials
• RSLAB-Remote Sensing Lab
• SPCOM-Signal Processing and Communications Group
• VEU-Speech Processing Group
• WiComTec-Wireless Communications and Technologies Research Group

Teachers

• Aguasca Sole, Alberto
• Agusti Comes, Ramon
• Alonso Zarate, Lluis
• Artigas Garcia, David
• Barlabe Dalmau, Antoni
• Belmonte Molina, Aniceto
• Bertran Alberti, Eduard
• Blanch Boris, Sebastián
• Broquetas Ibars, Antoni
• Cabrera Bean, Marga
• Camps Carmona, Adriano Jose
• Casadevall Palacio, Ferran
• Casas Pla, Josep Ramon
• Collado Gomez, J.Carlos
• Comellas Colome, Jaume
• Comeron Tejero, Adolfo
• Corbella Sanahuja, Ignasi
• Dios Otin, Victor Federico
• Duffo Ubeda, Nuria
• Fabregas Canovas, Francisco Javier
• Fernandez Rubio, Juan-Antonio
• Ferrus Ferre, Ramon
• Garcia Lozano, Mario
• Garcia Vizcaino, David
• Gasull Llampallas, Antoni
• Gelonch Bosch, Antoni
• Gene Bernaus, Joan M.
• Gilabert Pinal, Pere Lluis
• Giro Nieto, Xavier
• Gonzalez Arbesu, Jose Maria
• Heldring, Alexander
• Hernando Pericas, Francisco Javier
• Jofre Roca, Lluis
• Junyent Giralt, Gabriel
• Lagunas Hernandez, M. A.
• Lamarca Orozco, Meritxell
• Lazaro Villa, Jose Antonio
• Lopez Martinez, Carlos
• Mallorqui Franquet, Jordi Joan
• Marques Acosta, Ferran
• Mateu Mateu, Jordi
• Monte Moreno, Enric
• Montoro Lopez, Gabriel
• Moreno Bilbao, M. Asuncion
• Morros Rubio, Ramon
• Muñoz Medina, Olga
• Nadeu Camprubi, Climent
• Najar Marton, Montse
• O'callaghan Castella, Joan
• Olmos Bonafe, Juan Jose
• Pages Zamora, Alba
• Pardas Feliu, Montse
• Pascual Iserte, Antonio
• Perez Neira, Ana Isabel
• Perez Pueyo, Rosanna
• Perez Romero, Jordi
• Perez Torres, Juan
• Pradell Cara, Lluis
• Prat Goma, Josep
• Rey Micolau, Francesc
• Riba Sagarra, Jaume
• Rius Casals, Juan-Manuel
• roca cl,
• Rocadenbosch Burillo, Francisco
• Rodriguez Fonollosa, Javier
• Rodriguez Fonollosa, Jose Adrian
• Rodriguez Gomez, Alejandro
• Romeu Robert, Jordi
• Ruiz Boque, Silvia
• Ruiz Costa-Jussa, Marta
• Ruiz Hidalgo, Javier
• Ruiz Moreno, Sergio
• Sala Alvarez, Josep
• Salembier Clairon, Philippe
• Sallent Roig, Jose Oriol
• Santos Blanco, María
• Sicard, Michaël
• Soneira Ferrando, M. Jose
• Spadaro, Salvatore
• Tarres Ruiz, Francisco
• Torner Sabata, Lluis
• Torres Torres, Francesc
• Torres Urgell, Luis
• Ubeda Farre, Eduard
• Valenzuela Gonzalez, Jose Luis
• Vall-Llossera Ferran, Mercè
• Vazquez Grau, Gregori
• Vidal Manzano, Josep
• Vilaplana Besler, Veronica
• Villares Piera, Nemesio Javier