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Zhao, P., Fodor, G., Dán, G. & Telek, M. (2019). A Game Theoretic Approach to Uplink Pilot and Data Power Control in Multi-Cell Multi-User MIMO Systems. IEEE Transactions on Vehicular Technology, 68(9), 8707-8720
Open this publication in new window or tab >>A Game Theoretic Approach to Uplink Pilot and Data Power Control in Multi-Cell Multi-User MIMO Systems
2019 (English)In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 68, no 9, p. 8707-8720Article in journal (Refereed) Published
Abstract [en]

In multi-user multiple-input-multiple-output (MU-MIMO) systems that employ pilot-symbol aided channel estimation, the pilot-to-data power ratio (PDPR) has a large impact on the system performance. In this paper, we consider the problem of setting the PDPR in multi-cell MU-MIMO systems in the presence of channel estimation errors, intercell interference and pilot contamination. To analyze and address this problem, we first develop a model of the multi-cell MU-MIMO system and derive a closed-form expression for the mean squared error of the uplink received data symbols. Building on this result, we then propose two decentralized PDPR-setting algorithms based on game theoretic approaches that are applicable in multi-cell systems. We find that both algorithms converge to a Nash equilibrium and provide performance improvements over systems that do not properly set the PDPR, while they maintain different levels of fairness.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019
Keywords
Multi-antenna systems, channel state information, estimation techniques, receiver algorithms
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-261969 (URN)10.1109/TVT.2019.2927127 (DOI)000487191500036 ()
Note

QC 20191014

Available from: 2019-10-14 Created: 2019-10-14 Last updated: 2019-10-14Bibliographically approved
Abrardo, A., Fodor, G. & Moretti, M. (2019). Distributed Digital and Hybrid Beamforming Schemes With MMSE-SIC Receivers for the MIMO Interference Channel. IEEE Transactions on Vehicular Technology, 68(7), 6790-6804
Open this publication in new window or tab >>Distributed Digital and Hybrid Beamforming Schemes With MMSE-SIC Receivers for the MIMO Interference Channel
2019 (English)In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 68, no 7, p. 6790-6804Article in journal (Refereed) Published
Abstract [en]

This paper addresses the problem of weighted sumrate maximization and mean squared error (MSE) minimization for the multiple-input multiple-output (MIMO) interference channel. Specifically, we consider a weighted minimum MSE architecture where each receiver employs successive interference cancellation (SIC) to separate the various received data streams and derive a hybrid beamforming scheme, where the transmitters operate with a number of radio frequency chains smaller than the number of antennas, particularly suited for millimeter-wave channels and 5G applications. To derive our proposed schemes, we first study the relationship between sum-rate maximization and weighted MSE minimization when using SIC receivers, assuming fully digital beamforming. Next, we consider the important-and, as it turns out, highly non-trivial-case where the transmitters employ hybrid digital/analog beamforming, developing a distributed joint hybrid precoding and SIC-based combining algorithm. Moreover, for practical implementation, we propose a signaling scheme that utilizes a common broadcast channel and facilitates the acquisition of channel state information, assuming minimal assistance from a central node such as a cellular base station. Numerical results show that both the proposed weighted MMSE-SIC schemes exhibit great advantages with respect to their linear counterparts in terms of complexity, feedback information, and performance.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2019
Keywords
MIMO, weighted MSE minimization, successive interference cancellation, hybrid beamforming
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-255766 (URN)10.1109/TVT.2019.2918066 (DOI)000476775000046 ()2-s2.0-85069527149 (Scopus ID)
Note

QC 20190812

Available from: 2019-08-12 Created: 2019-08-12 Last updated: 2019-08-12Bibliographically approved
B. da Silva Jr., J. M., Sabharwal, A., Fodor, G. & Fischione, C. (2019). Low Resolution Phase Shifters Suffice for Full-Duplex mmWave Communications. In: IEEE International Conference on Communications: Workshop on Full-Duplex Communications for Future Wireless Networks. Paper presented at IEEE International Conference on Communications. Shangai, China: IEEE Communications Society
Open this publication in new window or tab >>Low Resolution Phase Shifters Suffice for Full-Duplex mmWave Communications
2019 (English)In: IEEE International Conference on Communications: Workshop on Full-Duplex Communications for Future Wireless Networks, Shangai, China: IEEE Communications Society, 2019Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Full-duplex base-stations with half-duplex nodes,allowing simultaneous uplink and downlink from different nodes,have the potential to double the spectrum efficiency withoutadding additional complexity at mobile nodes. Hybrid beam-forming is commonly used in millimeter-wave systems for itsimplementation efficiency. An important element of hybrid beam-forming is quantized phase shifters. In this paper, we ask iflow-resolution phase shifters suffice for beamforming-based full-duplex millimeter-wave systems. We formulate the problem ofjoint design for both self-interference suppression and downlinkbeamforming as an optimization problem, which we solve usingpenalty dual decomposition to obtain a near-optimal solution.Numerical results indicate that low-resolution phase shifters canperform close to systems that use infinite phase shifter resolution,and that even a single quantization bit outperforms half-duplextransmissions in both low and high residual self-interferencescenarios.

Place, publisher, year, edition, pages
Shangai, China: IEEE Communications Society, 2019
Keywords
full-duplex, millimeter wave, beamforming, phase shifter
National Category
Telecommunications
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-246220 (URN)
Conference
IEEE International Conference on Communications
Funder
Lars Hierta Memorial Foundation, FO2017-0236
Note

QC 20190617

Available from: 2019-04-23 Created: 2019-04-23 Last updated: 2019-06-17Bibliographically approved
Barros da Silva Jr., J. M., Sabharwal, A., Fodor, G. & Fischione, C. (2019). Low Resolution Phase Shifters Suffice for Full-Duplex mmWave Communications. In: 2019 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS WORKSHOPS (ICC WORKSHOPS): . Paper presented at IEEE International Conference on Communications (ICC), MAY 20-24, 2019, Shanghai, PEOPLES R CHINA. IEEE
Open this publication in new window or tab >>Low Resolution Phase Shifters Suffice for Full-Duplex mmWave Communications
2019 (English)In: 2019 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS WORKSHOPS (ICC WORKSHOPS), IEEE , 2019Conference paper, Published paper (Refereed)
Abstract [en]

Full-duplex base-stations with half-duplex nodes, allowing simultaneous uplink and downlink from different nodes, have the potential to double the spectrum efficiency without adding additional complexity at mobile nodes. Hybrid beam forming is commonly used in millimeter wave systems for its implementation efficiency. An important element of hybrid beam-forming is quantized phase shifters. In this paper, we ask if low-resolution phase shifters suffice for beamforming-based full-duplex millimeter wave systems. We formulate the problem of joint design for both self-interference suppression and downlink beamforming as an optimization problem, which we solve using penalty dual decomposition to obtain a near-optimal solution. Numerical results indicate that low-resolution phase shifters can perform close to systems that use infinite phase shifter resolution, and that even a single quantization bit outperforms half-duplex transmissions in both low and high residual self-interference scenarios.

Place, publisher, year, edition, pages
IEEE, 2019
Series
IEEE International Conference on Communications Workshops, ISSN 2164-7038
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-261051 (URN)10.1109/ICCW.2019.8756743 (DOI)000484917800046 ()2-s2.0-85070255997 (Scopus ID)978-1-7281-2373-8 (ISBN)
Conference
IEEE International Conference on Communications (ICC), MAY 20-24, 2019, Shanghai, PEOPLES R CHINA
Note

QC 20191002

Available from: 2019-10-02 Created: 2019-10-02 Last updated: 2019-10-02Bibliographically approved
Kant, S., Fodor, G., Bengtsson, M., Göransson, B. & Fischione, C. (2019). Low-Complexity OFDM Spectral Precoding. In: 20th IEEE International Workshop on Signal Processing Advances in Wireless Communications (SPAWC) 2019: . Paper presented at SPAWC.
Open this publication in new window or tab >>Low-Complexity OFDM Spectral Precoding
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2019 (English)In: 20th IEEE International Workshop on Signal Processing Advances in Wireless Communications (SPAWC) 2019, 2019Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

This paper proposes a new large-scale mask compliant spectral precoder (LS-MSP) for orthogonal frequency division multiplexing systems. In this paper, we first consider a previously proposed mask-compliant spectral precoding scheme that utilizes a generic convex optimization solver which suffers from high computational complexity, notably in large-scale systems. To mitigate the complexity of computing the LS-MSP, we propose a divide-and-conquer approach that breaks the original problem into smaller rank 1 quadratic-constraint problems and each small problem yields closed-form solution. Based on these solutions, we develop three specialized first-order low-complexity algorithms, based on 1) projection on convex sets and 2) the alternating direction method of multipliers. We also develop an algorithm that capitalizes on the closed-form solutions for the rank 1 quadratic constraints, which is referred to as 3) semianalytical spectral precoding. Numerical results show that the proposed LS-MSP techniques outperform previously proposed techniques in terms of the computational burden while complying with the spectrum mask. The results also indicate that 3) typically needs 3 iterations to achieve similar results as 1) and 2) at the expense of a slightly increased computational complexity.

Keywords
Spectral Precoding, OFDM, 5G, mmWave
National Category
Signal Processing
Research subject
Telecommunication
Identifiers
urn:nbn:se:kth:diva-258067 (URN)
Conference
SPAWC
Funder
Swedish Foundation for Strategic Research , ID17-0114
Note

QC 20190923

Available from: 2019-09-09 Created: 2019-09-09 Last updated: 2019-09-23Bibliographically approved
Abrardo, A., Fodor, G., Moretti, M. & Telek, M. (2019). MMSE Receiver Design and SINR Calculation in MU-MIMO Systems With Imperfect CSI. IEEE Wireless Communications Letters, 8(1), 269-272
Open this publication in new window or tab >>MMSE Receiver Design and SINR Calculation in MU-MIMO Systems With Imperfect CSI
2019 (English)In: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 8, no 1, p. 269-272Article in journal (Refereed) Published
Abstract [en]

The performance of the uplink of multiuser multiple input multiple output systems depends critically on the receiver architecture and on the quality of the acquired channel state information. A popular approach is to design linear receivers that minimize the mean squared error (MSE) of the received data symbols. Unfortunately, most of the literature does not take into account the presence of channel state information errors in the MSE minimization. In this letter we develop a linear minimum MSE (MMSE) receiver that employs the noisy instantaneous channel estimates to minimize the MSE, and highlight the dependence of the receiver performance on the pilot-to-data power ratio. By invoking the theory of random matrices, we calculate the users' signal-to-interference-plus-noise ratio as a function of the number of antennas and the pilot-to-data power ratio of all users. Numerical results indicate that this new linear receiver outperforms the classical mismatched MMSE receiver.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2019
Keywords
MIMO, channel state information, estimation error, mean square error methods
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-245929 (URN)10.1109/LWC.2018.2869763 (DOI)000459510200067 ()2-s2.0-85053318281 (Scopus ID)
Note

QC 20190312

Available from: 2019-03-12 Created: 2019-03-12 Last updated: 2019-03-12Bibliographically approved
Petrov, V., Fodor, G., Kokkoniemi, J., Moltchanov, D., Lehtomaki, J., Andreev, S., . . . Valkama, M. (2019). ON UNIFIED VEHICULAR COMMUNICATIONS AND RADAR SENSING IN MILLIMETER-WAVE AND LOW TERAHERTZ BANDS. IEEE wireless communications, 26(3), 146-153
Open this publication in new window or tab >>ON UNIFIED VEHICULAR COMMUNICATIONS AND RADAR SENSING IN MILLIMETER-WAVE AND LOW TERAHERTZ BANDS
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2019 (English)In: IEEE wireless communications, ISSN 1536-1284, E-ISSN 1558-0687, Vol. 26, no 3, p. 146-153Article in journal (Refereed) Published
Abstract [en]

Future smart vehicles will incorporate high-data-rate communications and high-resolution radar sensing capabilities operating in the millimeter-wave and higher frequencies. These two systems are preparing to share and reuse many common functionalities, such as steerable millimeter-wave antenna arrays. Motivated by this growing overlap, which is advanced further by space and cost constraints, the vehicular community is pursuing a vision of unified vehicular communications and radar sensing that represents a major paradigm shift for next-generation connected and self-driving cars. This article outlines a path to materialize this decisive transformation. We begin by reviewing the latest developments in hybrid vehicular communications and radar systems, and then propose a concept of unified channel access over millimeter-wave and higher frequencies. Our supporting system-level performance characterization relies upon real-life measurements and extensive ray-based modeling to confirm the significant improvements brought by our proposal to mitigating the interference and deafness effects. Since our results aim to open the door to unified vehicular communications and radar sensing, we conclude by outlining the potential research directions in this rapidly developing field.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-255495 (URN)10.1109/MWC.2019.1800328 (DOI)000474597100022 ()2-s2.0-85066981988 (Scopus ID)
Note

QC 20190919

Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2019-09-19Bibliographically approved
Petrov, V., Mikhaylov, K., Moltchanov, D., Andreev, S., Fodor, G., Torsner, J., . . . Koucheryavy, Y. (2019). When IoT Keeps People in the Loop: A Path Towards a New Global Utility. IEEE Communications Magazine, 57(1), 114-121
Open this publication in new window or tab >>When IoT Keeps People in the Loop: A Path Towards a New Global Utility
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2019 (English)In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 57, no 1, p. 114-121Article in journal (Refereed) Published
Abstract [en]

While the IoT has made significant progress supporting individual machine-type applications, it is only recently that the importance of people as an integral component of the overall IoT infrastructure has started to be fully recognized. Several powerful concepts have emerged to facilitate this vision, whether involving the human context whenever required or directly impacting user behavior and decisions. As these become the stepping stones to develop the IoT into a novel people-centric utility, this article outlines a path to realize this decisive transformation. We begin by reviewing the latest progress in human-aware wireless networking, then classify the attractive human-machine applications and summarize the enabling IoT radio technologies. We continue with a unique system-level performance characterization of a representative urban IoT scenario and quantify the benefits of keeping people in the loop on various levels. Our comprehensive numerical results confirm the significant gains that have been made available with tighter user involvement, and also corroborate the development of efficient incentivization mechanisms, thereby opening the door to future commoditization of the global people-centric IoT utility.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-244556 (URN)10.1109/MCOM.2018.1700018 (DOI)000457640200018 ()2-s2.0-85058102701 (Scopus ID)
Note

QC 20190312

Available from: 2019-03-12 Created: 2019-03-12 Last updated: 2019-03-12Bibliographically approved
Zhao, P., Fodor, G., Dan, G. & Telek, M. (2018). A Game Theoretic Approach to Setting the Pilot Power Ratio in Multi-User MIMO Systems. IEEE Transactions on Communications, 66(3), 999-1012
Open this publication in new window or tab >>A Game Theoretic Approach to Setting the Pilot Power Ratio in Multi-User MIMO Systems
2018 (English)In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 66, no 3, p. 999-1012Article in journal (Refereed) Published
Abstract [en]

We consider the uplink of a single cell multi-user multiple input multiple output (MU-MIMO) system, in which the base station acquires channel state information at the receiver by means of uplink pilot signals. Since each mobile station has a sum power budget that is used to transmit pilot and data symbols, the pilot power ratio (PPR) has a large impact on the system performance in terms of spectral and energy efficiency. We formulate the problem of PPR setting as a non-cooperative game, in which each mobile station aims at minimizing the mean squared error of the uplink received data symbols at the base station. We show that in this game a unique Nash equilibrium exists, and propose an iterative decentralized algorithm-termed best PPR algorithm (BPA)-that is guaranteed to converge to that Nash equilibrium. Since BPA dynamically responds to the measured interference, it outperforms widely used schemes that use a predetermined PPR. BPA also performs close to the global optimum, especially when mobile stations with similar path loss values are co-scheduled in the MU-MIMO system. Based on these insights, we propose a practical signaling mechanism for implementing BPA in MU-MIMO systems.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2018
Keywords
MIMO systems, power control, game theory, mean square error methods, Gaussian channels
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-227239 (URN)10.1109/TCOMM.2017.2778094 (DOI)000427678000008 ()
Note

QC 20180514

Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2019-08-20Bibliographically approved
Ardah, K., Fodor, G., Silva, Y. C. B., Freitas, W. C. . & Cavalcanti, F. R. P. (2018). A Novel Cell Reconfiguration Technique for Dynamic TDD Wireless Networks. IEEE Wireless Communications Letters, 7(3), 320-323
Open this publication in new window or tab >>A Novel Cell Reconfiguration Technique for Dynamic TDD Wireless Networks
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2018 (English)In: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 7, no 3, p. 320-323Article in journal (Refereed) Published
Abstract [en]

In dynamic time division duplexing (DTDD) systems, the uplink (UL) and downlink (DL) resources can be configured to adapt to changing traffic conditions. Therefiwe, DTDD systems are advantageously deployed in scenarios in which the UL and DL traffic demands are asymmetric and timevarying. Unfortunately, multicell DTDD systems give rise to base station-to-base station and user equipment-to-user equipment interference, that can severely degrade the system performance. Previous works on DTDD either assumed that the UL/DL configurations are given, or they did not take into account the negative impact of multicell DTDD interference. In this letter, we propose a novel cell reconfiguration technique that considers both the prevailing traffic conditions and multicell interference levels. The proposed technique is based on an efficient solution of a mixed integer linear program, whose objective is to maximize the overall system throughput taking into account users' traffic preferences. Realistic system level simulations indicate that the proposed scheme outperforms not only the static TDD system but also other reference schemes, that disregard the DTDD specific interference effects.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2018
Keywords
Dynamic TDD, cell reconfiguration, mixed integer linear programming, rate maximization
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-240236 (URN)10.1109/LWC.2017.2776264 (DOI)000436010400010 ()2-s2.0-85035803412 (Scopus ID)
Note

QC 20181218

Available from: 2018-12-18 Created: 2018-12-18 Last updated: 2018-12-18Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-2289-3159

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