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PhD Proposal CentraleSupelec: Statistical signal processing methods for wireless communications in sub-THz and THz frequency bands

22 Juillet 2022


Catégorie : Doctorant


1 Keywords

Sub-THz/THz bands, ultra-massive MIMO, beam alignment, beam-division multiple-access, channel estimation, nonlinear impairments, statistical signal processing, belief propagation, random-set theory, compressive sensing.

2 Abstract

This PhD subject explores the unsolved issues in signal processing to develop sub-THz and THz communications to their full potential. We propose to apply advanced tools from information theory, coding theory and signal statistical processing, in order to perform channel estimation, data decoding and localization with low complexity, while making the best use of time, frequency and spatial resources. We intend to tackle challenging use cases under unknown channel conditions, severe nonlinear effects and beam misalignment.

3 Detailed description of the subject

Context:

Wireless transmissions in sub-THz (0.1 − 0.3 THz) and THz (0.3 − 10 THz) bandwidths [1] are widely regarded as an enabling technology for future 6G communications, due to the availability of unused spectrum. The short wavelengths enable to pack a large number of antenna elements at the transmitter and receiver side, thus enabling ultra-massive multiple-input multiple-output (UM-MIMO) with the potential of tera-bits per second data rates and precise localization. Besides traditional backhaul links, deploying sub-THz/THz technologies thus becomes viable for emerging applications such as vehicular and device-to-device communications. However, MIMO channels in these frequency bands suffer from huge signal-to-noise degradation due to significant path loss and blockage [4], which can partly be compensated using high-gain beamforming. A number of signal processing processing issues remain largely unsolved in order to make affordable sub-THz/THz technologies available. First, physical layer waveform design is an important challenge. It is questionable whether orthogonal frequency division multiplexing (OFDM) used in 4G/5G is still relevent in the context of sub-THz/THz [2]-[3] due to complexity issues. Howewer for the single-carrier (SC) techniques described in [4], the narrowband beamforming model, where signals received over different antenna elements are identical up to a phase shift, may become invalid so that additional time delays need to be compensated [5]. Note that accurate channel estimation in known to be a difficult task in UM-MIMO settings [7]-[8] as it usually relies only on pilot symbols to estimate a large number of complex coefficients for growing array sizes. This problem becomes even more complicated in dynamic environments with user mobility. Also, low-cost RF implementations incure hardware impairments such as phase noise, I-Q imbalance and amplifier nonlinearities [14], that need proper compensation. Secondly, beam alignment between the transmitter and the receiver is required in order to overcome the overwhelming path loss (otherwise channel estimation would fail). Such mechanisms to establish communication are often time consuming and imperfect [9]. They also do not account for abrupt user appearance/disappearance caused by blockage. Thirdly, accomodating multiuser transmissions requires space division multiple access (SDMA) or beam division multiplexing (BDM) techniques, where groups of users clustered according to the similarity of their angle of departure (AoD) can be resolved [2]. Specific interference cancellation techniques need to be applied in order to cancel inter-group interference [10].

To conclude, it is worth pointing out that the problem of sub-THz/THz communications with potential beam misalignment or blockage has deep connections with multitarget estimation for direction-of-arrival (DOA) detection and tracking in radar theory [11].

Objectives:

The scientific objectives of the PhD thesis are twofold: (i) develop new statistical signal processing methods and design new algorithms with manageable complexity to solve these four problems, (ii) advance the state-of-the-art in deriving theoretical bounds to evaluate the performance of the proposed solutions.

Expected results:

Solve the following problems:

Problem 1: Reliable single-user UM-MIMO communications under static perfect channel state information at the receiver (CSIR) with hardware impairments. Under ideal beam alignment, assuming perfect CSIR is not unreasonable. However, the effect of phase noise and power amplifier nonlinearities at each RF chain have to be estimated and compensated for.

Problem 2: Reliable single-user UM-MIMO communications under unknown dynamic CSIR. Under ideal beam alignment, CSI has to be acquired and tracked with minimal pilot insertion.

Problem 3: Reliable multi-user beam training. Assuming neither the number of active users (due to potential blockage) nor the channel parameters (due to lack of prior beam alignment) are known, fast beam training is sought.

Problem 4: Joint transmission and localization. Since radar technologies share many features with sub-THz/THz communications, such as the frequency bands and the availability of large antenna arrays, joint radar-communication design is of interest to include localization functionalities, which is of particular interest in automotive applications.

Bibliography

[1] J. Federici and L. Moeller, “Review of terahertz and subterahertz wireless communications”, in Journal of Applied Physics, vol. 107, no. 11, p. 6, 2010.

[2] C. Lin and G. Y. L. Li, “Terahertz Communications: An Array-of-Subarrays Solution,” in IEEE Communications Magazine, vol. 54, no. 12, pp. 124-131, December 2016.

[3] H. Sarieddeen, N. Saeed, T. Y. Al-Naffouri and M.-S. Alouini, “Next Generation Terahertz Communications: A Rendezvous of Sensing, Imaging, and Localization,” arXiv preprint, 2020.

[4] H. Sarieddeen, M. -S. Alouini and T. Y. Al-Naffouri, “An Overview of Signal Processing Techniques for Terahertz Communications,” in Proceedings of the IEEE, vol. 109, no. 10, pp. 1628-1665, Oct. 2021.

[5] B. Wang et al., “Spatial-Wideband Effect in Massive MIMO with Application in mmWave Systems,” in IEEE Communications Magazine, vol. 56, no. 12, pp. 134-141, December 2018.

[6] T. Mao, Q. Wang and Z. Wang, “Receiver Design for the Low-Cost TeraHertz Communication System with Hardware Impairment,” ICC 2020 - 2020 IEEE International Conference on Communications (ICC), 2020, pp. 1-5.

[7] S. Nie and I. F. Akyildiz, “Deep Kernel Learning-Based Channel Estimation in Ultra-Massive MIMO Communications at 0.06-10 THz,” 2019 IEEE Globecom Workshops (GC Wkshps), 2019, pp. 1-6.

[8] J. Tan and L. Dai, “Wideband channel estimation for THz massive MIMO,” in China Communications, vol. 18, no. 5, pp. 66-80, May 2021.

[9] C. Liu, M. Li, S. V. Hanly, I. B. Collings and P. Whiting, “Millimeter Wave Beam Alignment: Large Deviations Analysis and Design Insights,” in IEEE Journal on Selected Areas in Communications, vol. 35, no. 7, pp. 1619-1631, July 2017.

[10] H. Sarieddeen, A. Abdallah, M. M. Mansour, M. -S. Alouini and T. Y. Al-Naffouri, “Terahertz-Band MIMO-NOMA: Adaptive Superposition Coding and Subspace Detection,” in IEEE Open Journal of the Communications Society, vol. 2, pp. 2628-2644, 2021.

[11] A. Saucan, T. Chonavel, C. Sintes and J. Le Caillec, “Marked poisson point process PHD filter for DOA tracking,” 2015 23rd European Signal Processing Conference (EUSIPCO), 2015, pp. 2621-2625.

[12] V. Petrov et al., “On Unified Vehicular Communications and Radar Sensing in Millimeter-Wave and Low Terahertz Bands,” in IEEE Wireless Communications, vol. 26, no. 3, pp. 146-153, June 2019.

[13] H. Du, J. Zhang, K. Guan, B. Ai and T. Kürner, “Reconfigurable Intelligent Surface Aided TeraHertz Communications Under Misalignment and Hardware Impairments,” arXiv preprint, 2020.

[14] T. Mao, Q. Wang and Z. Wang, “Spatial Modulation for Terahertz Communication Systems With Hardware Impairments,” in IEEE Transactions on Vehicular Technology, vol. 69, no. 4, pp. 4553-4557, April 2020.

 

Any PhD candidate should have:

• a research-oriented MSc. degree in applied mathematics/statistics, electrical engineeering, signal processing, or equivalent, with excellent study records, and possibly one or two publications in conference proceedings and/or international journals;

• a strong background in mathematics and statistics, and a deep knowledge in at least one of the following fields: information theory, communication theory, coding theory, signal processing for communications, Bayesian inference and learning;

• a demonstrated ability to work hard and autonomously;

• strong programming skills in one of the following languages: MATLAB, C/C++, or python;

• very good communication skills (French or English), both oral and written;

• a strong motivation for research and a taste for analytical and theoretical subjects.

 

Your application should be sent to the contact below before October 31, 2022, including

• a CV

• a letter of intent

• grades and ranking of your master’s thesis (M1/M2) or engineering school

• 2 recommandation letters

• a list of courses related to the research subject.

Contact:

Prof. Antoine O. Berthet

CentraleSupélec

Department Telecommunications

Laboratory L2S (CNRS UMR 8506)

3–10, rue Joliot Curie, Plateau de Moulon

91192 Gif-sur-Yvette, France

Tel.: +33 (0)1 69 85 14 62

E-mail: antoine.berthet@centralesupelec.fr

Web page: https://scholar.google.fr/citations?user=jxMJvuUAAAAJ&hl=en

Prof. Frédéric Lehmann

Télécom SudParis

Department CITI

Laboratory SAMOVAR

9, rue Charles Fourier

91011 Evry, France

Tel.: +33 (0)1 60 76 46 33

E-mail: frederic.lehmann@telecom-sudparis.eu

Web page: http://www-public.imtbs-tsp.eu/~lehmann/

Offer starting date: January 1, 2023