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  • 1.
    Akbar, Noman
    et al.
    Australian Natl Univ, Res Sch Engn, Canberra, ACT 2600, Australia..
    Björnson, Emil
    Linköping Univ, Dept Elect Engn ISY, S-58183 Linköping, Sweden..
    Yang, Nan
    Australian Natl Univ, Res Sch Engn, Canberra, ACT 2600, Australia..
    Larsson, Erik G.
    Linköping Univ, Dept Elect Engn ISY, S-58183 Linköping, Sweden..
    Max-Min Power Control in Downlink Massive MIMO With Distributed Antenna Arrays2021In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 69, no 2, p. 740-751Article in journal (Refereed)
    Abstract [en]

    In this paper, we investigate optimal downlink power allocation in massive multiple-input multiple-output (MIMO) networks with distributed antenna arrays (DAAs) under correlated and uncorrelated channel fading. In DAA massive MIMO, a base station (BS) consists of multiple antenna sub-arrays. Notably, the antenna sub-arrays are deployed in arbitrary locations within a DAA massive MIMO cell. Consequently, the distance-dependent large-scale propagation coefficients are different from a user to these different antenna sub-arrays, which makes power control a challenging problem. We assume that the network operates in time-division duplex mode, where each BS obtains the channel estimates via uplink pilots. Based on the channel estimates, the BSs perform maximum-ratio transmission in the downlink. We then derive a closed-form signal-to-interference-plus-noise ratio (SINR) expression, where the channels are subject to correlated fading. Based on the SINR expression, we propose a network-wide max-min power control algorithm to ensure that each user in the network receives a uniform quality of service. Numerical results demonstrate the performance advantages offered by DAA massive MIMO. For some specific scenarios, DAA massive MIMO can improve the average per-user throughput up to 55%. Furthermore, we demonstrate that channel fading covariance is an important factor in determining the performance of DAA massive MIMO.

  • 2.
    Akhlaghpasand, Hossein
    et al.
    Iran Univ Sci & Technol, Sch Elect Engn, Tehran 1684613114, Iran..
    Björnson, Emil
    Linköping Univ, Dept Elect Engn, S-58183 Linköping, Sweden..
    Razavizadeh, S. Mohammad
    Iran Univ Sci & Technol, Sch Elect Engn, Tehran 1684613114, Iran..
    Jamming-Robust Uplink Transmission for Spatially Correlated Massive MIMO Systems2020In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 68, no 6, p. 3495-3504Article in journal (Refereed)
    Abstract [en]

    In this paper, we consider how the uplink transmission of a spatially correlated massive multiple-input multiple-output (MIMO) system can be protected from a jamming attack. To suppress the jamming, we propose a novel framework including a new optimal linear estimator in the training phase and a bilinear equalizer in the data phase. The proposed estimator is optimal in the sense of maximizing the spectral efficiency of the legitimate system attacked by a jammer, and its implementation needs the statistical knowledge about the jammer's channel. We derive an efficient algorithm to estimate the jamming information needed for implementation of the proposed framework. Furthermore, we demonstrate that optimized power allocation at the legitimate users can improve the performance of the proposed framework regardless of the jamming power optimization. Our proposed framework can be exploited to combat jamming in scenarios with either ideal or non-ideal hardware at the legitimate users and the jammer. Numerical results reveal that using the proposed framework, the jammer cannot dramatically affect the performance of the legitimate system.

  • 3.
    Alexander, Paul D.
    et al.
    University of South Australia.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    On the windowed Cholesky factorization of the time-varying asynchronous CDMA channel1998In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 46, no 6, p. 735-737Article in journal (Refereed)
  • 4.
    Alexander, Paul D.
    et al.
    University of South Australia.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Schlegel, Christian B.
    University of Texas, San Antonio, USA.
    A linear receiver for coded multiuser CDMA1997In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 45, no 5, p. 605-610Article in journal (Refereed)
  • 5.
    Andersson, Tomas
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    A COVQ-Based image coder for channels with bit errors and erasures2008In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 56, no 2, p. 161-165Article in journal (Refereed)
    Abstract [en]

    We illustrate how channel optimized vector quantization (COVQ) can be used for channels with both bit-errors and bit-erasures. First, a memoryless channel model is presented, and the performance of COVQ's trained for this channel is evaluated for an i.i.d. Gaussian source. Then, the new method is applied in implementing an error-robust sub-band image coder, and we present image results that illustrate the resulting performance. Our experiments show that the new approach is able to outperform a traditional scheme based on separate source and channel coding.

  • 6.
    Antonioli, Roberto Pinto
    et al.
    Univ Fed Ceara, Wireless Telecom Res Grp, BR-60440900 Fortaleza, Ceara, Brazil..
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control). Ericsson Res, Radio Dept, S-16480 Stockholm, Sweden..
    Soldati, Pablo
    Ericsson Res, Stand & Technol, S-16480 Stockholm, Sweden..
    Maciel, Tarcisio Ferreira
    Univ Fed Ceara, Wireless Telecom Res Grp, BR-60440900 Fortaleza, Ceara, Brazil..
    Decentralized User Scheduling for Rate-Constrained Sum-Utility Maximization in the MIMO IBC2020In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 68, no 10, p. 6215-6229Article in journal (Refereed)
    Abstract [en]

    While the problems of sum-rate maximization and sum-power minimization subject to quality of service (QoS) constraints in the multiple input multiple output interference broadcast channel (MIMO IBC) have been widely studied, most of the proposed solutions have neglected the user scheduling aspect assuming that a feasible set of users has been previously selected. However, ensuring QoS for each user in the MIMO IBC involves the joint optimization of transmit/receive beamforming vectors, transmit powers, and user scheduling variables. To address the full problem, we propose a novel formulation of a rate-constrained sum-utility maximization problem which allows to either deactivate users or minimize the QoS degradation for some scheduled users in infeasible scenarios. Remarkably, this is achieved avoiding the complexity of traditional combinatorial formulations, but rather by introducing a novel expression of the QoS constraints that allows to solve the problem in a continuous domain. We propose centralized and decentralized solutions, where the decentralized solutions focus on practical design and low signaling overhead. The proposed solutions are then compared with benchmarking algorithms, where we show the effectiveness of the joint scheduling and transceiver design as well as the flexibility of the proposed solution performing advantageously in several MIMO IBC scenarios.

  • 7. Azmi, Marwan H.
    et al.
    Yuan, Jinhong
    Lechner, Gottfried
    Rasmussen, Lars Kildehöj
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Design of Multi-Edge-Type Bilayer-Expurgated LDPC Codes for Decode-and-Forward in Relay Channels2011In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 59, no 11, p. 2993-3006Article in journal (Refereed)
    Abstract [en]

    We consider the design of bilayer-expurgated low-density parity-check (BE-LDPC) codes as part of a decode-and-forward protocol for use over the full-duplex relay channel. A new ensemble of codes, termed multi-edge-type bilayer-expurgated LDPC (MET-BE-LDPC) codes, is introduced where the BE-LDPC code design problem is transformed into the problem of optimizing the multinomials of a multi-edge-type LDPC code. We propose two design strategies for optimizing MET-BE-LDPC codes; the bilayer approach is preferred when the difference in SNR between the source-to-relay and the source-to-destination channels is small, while the bilayer approach with intermediate rates is preferred when this difference is large. In both proposed design strategies multi-edge-type density evolution is used for code optimization. The resulting MET-BE-LDPC codes exhibit improved threshold and bit-error-rate performance as compared to previously reported bilayer LDPC codes.

  • 8. Bao, J.
    et al.
    Ma, Z.
    Karagiannidis, G. K.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Zhu, Z.
    Joint Multiuser Detection of Multidimensional Constellations over Fading Channels2017In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 65, no 1, p. 161-172, article id 7723894Article in journal (Refereed)
    Abstract [en]

    We investigate the error performance of multidimensional constellations in the multiple access and broadcast channels. More specifically, we provide closed-form expressions for the pairwise error probability (PEP) of the joint maximum likelihood detection, for multiuser signaling in the presence of additive white Gaussian noise and Rayleigh fading. Arbitrary numbers of users and multidimensional signal sets are assumed, while the provided formula for the PEP is a function of the dimension-wise distances of the multidimensional constellation. Furthermore, a useful upper bound on the average symbol error probability is also obtained through the union bound. The analysis is applied to the sparse code multiple access systems. The analytical results are validated successfully through simulations, and show their importance in the multidimensional constellation design.

  • 9.
    Bao, Jinchen
    et al.
    Southwest Jiaotong Univ, Prov Key Lab Informat Coding & Transmiss, Chengdu 611756, Sichuan, Peoples R China..
    Ma, Zheng
    Southwest Jiaotong Univ, Prov Key Lab Informat Coding & Transmiss, Chengdu 611756, Sichuan, Peoples R China..
    Xiao, Ming
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Tsiftsis, Theodoros A.
    Jinan Univ, Sch Elect & Informat Engn, Zhuhai 519070, Peoples R China..
    Zhu, Zhongliang
    Southwest Jiaotong Univ, Prov Key Lab Informat Coding & Transmiss, Chengdu 611756, Sichuan, Peoples R China..
    Bit-Interleaved Coded SCMA With Iterative Multiuser Detection: Multidimensional Constellations Design2018In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 66, no 11, p. 5292-5304Article in journal (Refereed)
    Abstract [en]

    This paper investigates the constellation/codebook design of a promising uplink multiple access technique, sparse code multiple access (SCMA), proposed for the fifth generation mobile networks. The application of bit-interleaved coded modulation with iterative multiuser detection is considered for uplink SCMA over fading channels. Extrinsic information transfer chart is used to aid the analysis and the design of multidimensional constellations, and the design criteria for multidimensional constellations and labelings optimization are thus established. Furthermore, a new and simple approach of multi-stage optimization for the multidimensional constellation design is proposed for SCMA, to improve the bit-error rate performance and alleviate the complexity of turbo multiuser detection. Numerical and simulation results are also provided to demonstrate the performance and verify the efficiency of the proposed scheme, compared with the state of the art.

  • 10.
    Barros da Silva Jr., José Mairton
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    Ghauch, Hadi
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    Fodor, Gabor
    Ericsson Research, Kista, Sweden..
    Skoglund, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    Smart Antenna Assignment is Essential in Full-Duplex Communications2021In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 69, no 5, p. 3450-3466Article in journal (Refereed)
    Abstract [en]

    Full-duplex communications have the potential to almost double the spectralefficiency. To realize such a potentiality, the signal separation at base station’s antennasplays an essential role. This paper addresses the fundamentals of such separationby proposing a new smart antenna architecture that allows every antenna to beeither shared or separated between uplink and downlink transmissions. The benefitsof such architecture are investigated by an assignment problem to optimally assignantennas, beamforming and power to maximize the weighted sum spectral efficiency.We propose a near-to-optimal solution using block coordinate descent that divides theproblem into assignment problems, which are NP-hard, a beamforming and powerallocation problems. The optimal solutions for the beamforming and power allocationare established while near-to-optimal solutions to the assignment problems are derivedby semidefinite relaxation. Numerical results indicate that the proposed solution isclose to the optimum, and it maintains a similar performance for high and low residualself-interference powers. With respect to the usually assumed antenna separationtechnique and half-duplex transmission, the sum spectral efficiency gains increase withthe number of antennas. We conclude that our proposed smart antenna assignment forsignal separation is essential to realize the benefits of multiple antenna full-duplexcommunications.

  • 11.
    Bashar, Manijeh
    et al.
    Univ Surrey, Inst Commun Syst, Home 5G Innovat Ctr 5GIC, Guildford GU2 7XH, Surrey, England..
    Ngo, Hien Quoc
    Queens Univ Belfast, Sch Elect Elect Engn & Comp Sci, Belfast T7 1NN, Antrim, North Ireland..
    Cumanan, Kanapathippillai
    Univ York, Dept Elect Engn, York YO10 5NG, N Yorkshire, England..
    Burr, Alister G.
    Univ York, Dept Elect Engn, York YO10 5NG, N Yorkshire, England..
    Xiao, Pei
    Univ Surrey, Inst Commun Syst, Home 5G Innovat Ctr 5GIC, Guildford GU2 7XH, Surrey, England..
    Björnson, Emil
    Linköping Univ, Dept Elect Engn, S-58183 Linköping, Sweden..
    Larsson, Erik G.
    Linköping Univ, Dept Elect Engn, S-58183 Linköping, Sweden..
    Uplink Spectral and Energy Efficiency of Cell-Free Massive MIMO With Optimal Uniform Quantization2021In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 69, no 1, p. 223-245Article in journal (Refereed)
    Abstract [en]

    This paper investigates the performance of limited-fronthaul cell-free massive multiple-input multiple-output (MIMO) taking account the fronthaul quantization and imperfect channel acquisition. Three cases are studied, which we refer to as Estimate&Quantize, Quantize&Estimate, and Decentralized, according to where channel estimation is performed and exploited. Maximum-ratio combining (MRC), zero-forcing (ZF), and minimum mean-square error (MMSE) receivers are considered. The Max algorithm and the Bussgang decomposition are exploited to model optimum uniform quantization. Exploiting the optimal step size of the quantizer, analytical expressions for spectral and energy efficiencies are presented. Finally, an access point (AP) assignment algorithm is proposed to improve the performance of the decentralized scheme. Numerical results investigate the performance gap between limited fronthaul and perfect fronthaul cases, and demonstrate that exploiting relatively few quantization bits, the performance of limited-fronthaul cell-free massive MIMO closely approaches the perfect-fronthaul performance.

  • 12.
    Ben Slimane, Slimane
    KTH, Superseded Departments (pre-2005), Signals, Sensors and Systems.
    Bounds on the Distribution of a Sum of Independent Lognormal Random Variables2001In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 49, no 6, p. 975-978Article in journal (Refereed)
    Abstract [en]

    The distribution function of a sum of lognormal random variables (RVs) appears in several communication problems. Approximations are usually used for such distribution as no closed form nor bounds exist. Bounds can be very useful in assessing the performance of any given system. In this letter, we derive upper and lower bounds on the distribution function of a sum of independent lognormal RVs. These bounds are given in a closed form and can be used in studying the performance of cellular radio and broadcasting systems.

  • 13.
    Björnson, Emil
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Matthaiou, M.
    Debbah, M.
    A New Look at Dual-Hop Relaying: Performance Limits with Hardware Impairments2013In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 61, no 11, p. 4512-4525Article in journal (Refereed)
    Abstract [en]

    Physical transceivers have hardware impairments that create distortions which degrade the performance of communication systems. The vast majority of technical contributions in the area of relaying neglect hardware impairments and, thus, assume ideal hardware. Such approximations make sense in low-rate systems, but can lead to very misleading results when analyzing future high-rate systems. This paper quantifies the impact of hardware impairments on dual-hop relaying, for both amplify-and-forward and decode-and-forward protocols. The outage probability (OP) in these practical scenarios is a function of the effective end-to-end signal-to-noise-and-distortion ratio (SNDR). This paper derives new closed-form expressions for the exact and asymptotic OPs, accounting for hardware impairments at the source, relay, and destination. A similar analysis for the ergodic capacity is also pursued, resulting in new upper bounds. We assume that both hops are subject to independent but non-identically distributed Nakagami-m fading. This paper validates that the performance loss is small at low rates, but otherwise can be very substantial. In particular, it is proved that for high signal-to-noise ratio (SNR), the end-to-end SNDR converges to a deterministic constant, coined the SNDR ceiling, which is inversely proportional to the level of impairments. This stands in contrast to the ideal hardware case in which the end-to-end SNDR grows without bound in the high-SNR regime. Finally, we provide fundamental design guidelines for selecting hardware that satisfies the requirements of a practical relaying system.

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  • 14.
    Björnson, Emil
    et al.
    Linköping Univ, Dept Elect Engn ISY, S-58183 Linköping, Sweden..
    Sanguinetti, Luca
    Univ Pisa, Dipartimento Ingn Informaz, I-56122 Pisa, Italy..
    Scalable Cell-Free Massive MIMO Systems2020In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 68, no 7, p. 4247-4261Article in journal (Refereed)
    Abstract [en]

    Imagine a coverage area with many wireless access points that cooperate to jointly serve the users, instead of creating autonomous cells. Such a cell-free network operation can potentially resolve many of the interference issues that appear in current cellular networks. This ambition was previously called Network MIMO (multiple-input multiple-output) and has recently reappeared under the name Cell-Free Massive MIMO. The main challenge is to achieve the benefits of cell-free operation in a practically feasible way, with computational complexity and fronthaul requirements that are scalable to large networks with many users. We propose a new framework for scalable Cell-Free Massive MIMO systems by exploiting the dynamic cooperation cluster concept from the Network MIMO literature. We provide a novel algorithm for joint initial access, pilot assignment, and cluster formation that is proved to be scalable. Moreover, we adapt the standard channel estimation, precoding, and combining methods to become scalable. A new uplink and downlink duality is proved and used to heuristically design the precoding vectors on the basis of the combining vectors. Interestingly, the proposed scalable precoding and combining outperform conventional maximum ratio (MR) processing and also performs closely to the best unscalable alternatives.

  • 15.
    Björnson, Emil
    et al.
    Linköping Univ, Dept Elect Engn ISY, S-58183 Linköping, Sweden..
    Sanguinetti, Luca
    Univ Pisa, Dipartimento Ingn Informaz, I-56122 Pisa, Italy..
    Hoydis, Jakob
    Paris Saclay, Nokia Bell Labs, F-91620 Nozay, France..
    Hardware Distortion Correlation Has Negligible Impact on UL Massive MIMO Spectral Efficiency2019In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 67, no 2, p. 1085-1098Article in journal (Refereed)
    Abstract [en]

    This paper analyzes how the distortion created by hardware impairments in a multiple-antenna base station affects the uplink spectral efficiency (SE), with a focus on massive multiple input multiple output (MIMO). This distortion is correlated across the antennas but has been often approximated as uncorrelated to facilitate (tractable) SE analysis. To determine when this approximation is accurate, basic properties of distortion correlation are first uncovered. Then, we separately analyze the distortion correlation caused by third-order non-linearities and by quantization. Finally, we study the SE numerically and show that the distortion correlation can be safely neglected in massive MIMO when there are sufficiently many users. Under independent identically distributed Rayleigh fading and equal signal-to-noise ratios (SNRs), this occurs for more than five transmitting users. Other channel models and SNR variations have only minor impact on the accuracy. We also demonstrate the importance of taking the distortion characteristics into account in the receive combining.

  • 16.
    Blasco-Serrano, Ricardo
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Andersson, Mattias
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rathi, Vishwambhar
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Polar Codes for Cooperative Relaying2012In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 60, no 11, p. 3263-3273Article in journal (Refereed)
    Abstract [en]

    We consider the symmetric discrete memoryless relay channel with orthogonal receiver components and show that polar codes are suitable for decode-and-forward and compress-and-forward relaying. In the first case we prove that polar codes are capacity achieving for the physically degraded relay channel; for stochastically degraded relay channels our construction provides an achievable rate. In the second case we construct sequences of polar codes that achieve the compress-and-forward rate by nesting polar codes for source compression into polar codes for channel coding. In both cases our constructions inherit most of the properties of polar codes. In particular, the encoding and decoding algorithms and the bound on the block error probability O(2 (N beta)) which holds for any 0 < beta < 1/2.

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  • 17.
    Braga Jr, Iran Mesquita
    et al.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, BR-60455760 Fortaleza, Ceara, Brazil..
    Antonio, Roberto Pinto
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, BR-60455760 Fortaleza, Ceara, Brazil..
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control). Ericsson Res, S-16480 Stockholm, Sweden.;.
    Silva, C. B.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, BR-60455760 Fortaleza, Ceara, Brazil..
    Silva, Carlos F. M. E.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, BR-60455760 Fortaleza, Ceara, Brazil..
    Freitas Jr, Alter C.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, BR-60455760 Fortaleza, Ceara, Brazil..
    Joint Resource Allocation and Transceiver Design for Sum-Rate Maximization Under Latency Constraints in Multicell MU-MIMO Systems2021In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 69, no 7, p. 1-1Article in journal (Refereed)
    Abstract [en]

    Due to the continuous advancements of orthogonal frequency division multiplexing (OFDM) and multiple antenna techniques, multiuser multiple input multiple output (MU-MIMO) OFDM is a key enabler of both fourth and fifth generation networks. In this paper, we consider the problem of weighted sum-rate maximization under latency constraints in finite buffer multicell MU-MIMO OFDM systems. Unlike previous works, the optimization variables include the transceiver beamforming vectors, the scheduled packet size and the resources in the frequency and power domains. This problem is motivated by the observation that multicell MU-MIMO OFDM systems serve multiple quality of service classes and the system performance depends critically on both the transceiver design and the scheduling algorithm. Since this problem is non-convex, we resort to the max-plus queuing method and successive convex approximation. We propose both centralized and decentralized solutions, in which practical design aspects, such as signaling overhead, are considered. Finally, we compare the proposed framework with state-of-the-art algorithms in relevant scenarios, assuming a realistic channel model with space, frequency and time correlations. Numerical results indicate that our design provides significant gains over designs based on the wide-spread saturated buffers assumption, while also outperforming algorithms that consider a finite-buffer model. Due to the continuous advancements of orthogonal frequency division multiplexing (OFDM) and multiple antenna techniques, multiuser multiple input multiple output (MU-MIMO) OFDM is a key enabler of both fourth and fifth generation networks. In this paper, we consider the problem of weighted sum-rate maximization under latency constraints in finite buffer multicell MU-MIMO OFDM systems. Unlike previous works, the optimization variables include the transceiver beamforming vectors, the scheduled packet size and the resources in the frequency and power domains. This problem is motivated by the observation that multicell MU-MIMO OFDM systems serve multiple quality of service classes and the system performance depends critically on both the transceiver design and the scheduling algorithm. Since this problem is non-convex, we resort to the max-plus queuing method and successive convex approximation. We propose both centralized and decentralized solutions, in which practical design aspects, such as signaling overhead, are considered. Finally, we compare the proposed framework with state-of-the-art algorithms in relevant scenarios, assuming a realistic channel model with space, frequency and time correlations. Numerical results indicate that our design provides significant gains over designs based on the widespread saturated buffers assumption, while also outperforming algorithms that consider a finite-buffer model.

  • 18.
    Brännström, Fredrik
    et al.
    Chalmers University of Technology.
    Aulin, Tor M.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    Chalmers University of Technology.
    Iterative detectors for trellis-code multiple-access2002In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 50, no 9, p. 1478-1485Article in journal (Refereed)
  • 19.
    Celebi, Hasan Basri
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Pitarokoilis, Antonius
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering. Ericsson AB, S-16480 Stockholm, Sweden..
    Skoglund, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Latency and Reliability Trade-Off With Computational Complexity Constraints: OS Decoders and Generalizations2021In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 69, no 4, p. 2080-2092Article in journal (Refereed)
    Abstract [en]

    In this article, we study the problem of latency and reliability trade-off in ultra-reliable low-latency communication (URLLC) in the presence of decoding complexity constraints. We consider linear block encoded codewords transmitted over a binary-input AWGN channel and decoded with order-statistic (OS) decoder. We first investigate the performance of OS decoders as a function of decoding complexity and propose an empirical model that accurately quantifies the corresponding trade-off. Next, a consistent way to compute the aggregate latency for complexity constrained receivers is presented, where the latency due to decoding is also included. It is shown that, with strict latency requirements, decoding latency cannot be neglected in complexity constrained receivers. Next, based on the proposed model, several optimization problems, relevant to the design of URLLC systems, are introduced and solved. It is shown that the decoding time has a drastic effect on the design of URLLC systems when constraints on decoding complexity are considered. Finally, it is also illustrated that the proposed model can closely describe the performance versus complexity trade-off for other candidate coding solutions for URLLC such as tail-biting convolutional codes, polar codes, and low-density parity-check codes.

  • 20.
    Celebi, Hasan Basri
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering. ABB AB, S-72161 Västerås, Sweden..
    Skoglund, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Goodput Maximization With Quantized Feedback in the Finite Blocklength Regime for Quasi-Static Channels2022In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 70, no 8, p. 5071-5084Article in journal (Refereed)
    Abstract [en]

    In this paper, we study a quantized feedback scheme to maximize the goodput of a finite blocklength communication scenario over a quasi-static fading channel. It is assumed that the receiver has perfect channel state information (CSI) and sends back the CSI to the transmitter over a resolution-limited error-free feedback channel. With this partial CSI, the transmitter is supposed to select the optimum transmission rate, such that it maximizes the overall goodput of the communication system. This problem has been studied for the asymptotic blocklength regime, however, no solution has so far been presented for finite blocklength. Here, we study this problem in two cases: with and without constraint on reliability. We first formulate the optimization problems and analytically solve them. Iterative algorithms that successfully exploit the system parameters for both cases are presented. It is shown that although the achievable maximum goodput decreases with shorter blocklengths and higher reliability requirements, significant improvement can be achieved even with coarsely quantized feedback schemes.

  • 21.
    Champati, Jaya Prakash
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Al-Zubaidy, Hussein
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Gross, James
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Statistical Guarantee Optimization for AoI in Single-Hop and Two-Hop FCFS Systems With Periodic Arrivals2021In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 69, no 1, p. 365-381Article in journal (Refereed)
    Abstract [en]

    Age of Information (AoI) has proven to be a useful metric in networked systems where timely information updates are of importance. In the literature, minimizing "average age" has received considerable attention. However, various applications pose stricter age requirements on the updates which demand knowledge of the AoI distribution. Furthermore, the analysis of AoI distribution in a multi-hop setting, which is important for the study of Wireless Networked Control Systems (WNCS), has not been addressed before. Toward this end, we study the distribution of AoI in a WNCS with two hops and devise a problem of minimizing the tail of the AoI distribution with respect to the frequency of generating information updates, i.e., the sampling rate of monitoring a process, under first-come-first-serve (FCFS) queuing discipline. We argue that computing an exact expression for the AoI distribution may not always be feasible; therefore, we opt for computing upper bounds on the tail of the AoI distribution. Using these upper bounds, we formulate Upper Bound Minimization Problems (UBMP), namely, Chernoff-UBMP and alpha-relaxed Upper Bound Minimization Problem (alpha-UBMP), where alpha > 1 is an approximation factor, and solve them to obtain "good" heuristic rate solutions for minimizing the tail. We demonstrate the efficacy of our approach by solving the proposed UBMPs for three service distributions: geometric, exponential, and Erlang. Simulation results show that the rate solutions obtained are near optimal for minimizing the tail of the AoI distribution for the considered distributions.

  • 22.
    Champati, Jaya Prakash
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering. IMDEA Networks Inst, Madrid 28918, Spain..
    Skoglund, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Jansson, Magnus
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Gross, James
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Detecting State Transitions of a Markov Source: Sampling Frequency and Age Trade-off2022In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 70, no 5, p. 3081-3095Article in journal (Refereed)
    Abstract [en]

    We consider a finite-state Discrete-Time Markov Chain (DTMC) source that can be sampled for detecting the events when the DTMC transits to a new state. Our goal is to study the trade-off between sampling frequency and staleness in detecting the events. We argue that, for the problem at hand, using Age of Information (AoI) for quantifying the staleness of a sample is conservative and therefore, study another freshness metric age penalty, which is defined as the time elapsed since the first transition out of the most recently observed state. We study two optimization problems: minimize average age penalty subject to an average sampling frequency constraint, and minimize average sampling frequency subject to an average age penalty constraint; both are Constrained Markov Decision Problems. We solve them using the Lagrangian MDP approach, where we also provide structural results that reduce the search space. Our numerical results demonstrate that the computed Markov policies not only outperform optimal periodic sampling policies, but also achieve sampling frequencies close to or lower than that of an optimal clairvoyant (non-causal) sampling policy, if a small age penalty is allowed.

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  • 23.
    Chen, Zheng
    et al.
    Linköping Univ, Dept Elect Engn ISY, S-58183 Linköping, Sweden..
    Björnson, Emil
    Linköping Univ, Dept Elect Engn ISY, S-58183 Linköping, Sweden..
    Channel Hardening and Favorable Propagation in Cell-Free Massive MIMO With Stochastic Geometry2018In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 66, no 11, p. 5205-5219Article in journal (Refereed)
    Abstract [en]

    Cell-free (CF) massive multiple-input multiple-output (MIMO) is an alternative topology for future wireless networks, where a large number of single-antenna access points (APs) are distributed over the coverage area. There are no cells but all users are jointly served by the APs using network MIMO methods. Prior works have claimed that the CF massive MIMO inherits the basic properties of cellular massive MIMO, namely, channel hardening and favorable propagation. In this paper, we evaluate if one can rely on these properties when having a realistic stochastic AP deployment. Our results show that channel hardening only appears in special cases, for example, when the pathloss exponent is small. However, by using 5-10 antennas per AP, instead of one, we can substantially improve the hardening. Only spatially well-separated users will exhibit favorable propagation, but when adding more antennas and/or reducing the pathloss exponent, it becomes more likely for favorable propagation to occur. The conclusion is that we cannot rely on the channel hardening and the favorable propagation when analyzing and designing the CF massive MIMO networks, but we need to use achievable rate expressions and resource allocation schemes that work well also in the absence of these properties. Some options are reviewed in this paper.

  • 24. Chien, Trinh Van
    et al.
    Mollen, Christopher
    Linköping Univ, Dept Elect Engn ISY, S-58183 Linköping, Sweden..
    Björnson, Emil
    Linköping Univ, Dept Elect Engn ISY, S-58183 Linköping, Sweden..
    Large-Scale-Fading Decoding in Cellular Massive MIMO Systems With Spatially Correlated Channels2019In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 67, no 4, p. 2746-2762Article in journal (Refereed)
    Abstract [en]

    Massive multiple-input-multiple-output (MIMO) systems can suffer from coherent intercell interference due to the phenomenon of pilot contamination. This paper investigates a two-layer decoding method that mitigates both coherent and non-coherent interference in multi-cell Massive MIMO. To this end, each base station (BS) first estimates the channels to intra-cell users using either minimum mean-squared error (MMSE) or element-wise MMSE estimation based on uplink pilots. The estimates are used for local decoding on each BS followed by a second decoding layer where the BSs cooperate to mitigate inter-cell interference. An uplink achievable spectral efficiency (SE) expression is computed for arbitrary two-layer decoding schemes. A closed form expression is then obtained for correlated Rayleigh fading, maximum-ratio combining, and the proposed large-scale fading decoding (LSFD) in the second layer. We also formulate a sum SE maximization problem with both the data power and LSFD vectors as optimization variables. Since this is an NP-hard problem, we develop a low-complexity algorithm based on the weighted MMSE approach to obtain a local optimum. The numerical results show that both data power control and LSFD improve the sum SE performance over single-layer decoding multi-cell Massive MIMO systems.

  • 25.
    Cho, Jeong-woo
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.
    Chong, Song
    KAIST (Korea Advanced Institute of Science and Technology).
    Utility Max-Min Flow Control Using Slope-Restricted Utility Functions2007In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 55, no 5, p. 963-972Article in journal (Refereed)
    Abstract [en]

    We present a network architecture for the distributed utility max-min flow control of elastic and nonelastic flows where utility values of users (rather than data rates of users) are enforced to achieve max-min fairness. The proposed link algorithm converges to utility max-min fair bandwidth allocation in the presence of round-trip delays without using the information of users' utility functions. To show that the proposed algorithm can be stabilized not locally but globally, we found that the use of nonlinear control theory is inevitable. Even though we use a distributed flow-control algorithm, it is shown that any kind of utility function can be used as long as the minimum slopes of the functions are greater than a certain positive value. Though our analysis is limited to the single-bottleneck and homogeneous-delay case, we believe that the proposed algorithm is the first to achieve utility max-min fairness with guaranteed stability in a distributed manner

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  • 26.
    Dai, Bin
    et al.
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu 610031, Sichuan, Peoples R China..
    Yu, Liman
    Chengdu Text Coll, Sch Econ & Management, Chengdu 611731, Sichuan, Peoples R China..
    Liu, Xuxun
    South China Univ Technol, Sch Elect & Informat Engn, Guangzhou 510641, Guangdong, Peoples R China..
    Ma, Zheng
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering. Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu 610031, Sichuan, Peoples R China..
    Feedback Coding Schemes for the Broadcast Channel With Mutual Secrecy Requirement at the Receivers2019In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 67, no 9, p. 6039-6052Article in journal (Refereed)
    Abstract [en]

    The broadcast channel with mutual secrecy requirement at the receivers (BC-MSR-R) is a basic model characterizing the physical layer security (PLS) in the down-link of the wireless communication systems, where one transmitter sends two independent messages to two receivers via a broadcast channel, and each receiver can successfully decode his/her intended message and wishes to overhear the other one's message. This paper studies how to enhance the already existing secrecy rate region of the BC-MSR-R via receivers' feedback. Specifically, we propose two feedback strategies for the BC-MSR-R, where one uses the feedback to generate pure secret keys protecting the transmitted messages, and the other uses the feedback to generate not only keys but also cooperative messages helping the receivers to improve their decoding performance. Different inner bounds on the secrecy capacity region of the BC-MSR-R with noiseless feedback are constructed according to different feedback strategies, and these bounds are further illustrated by a Dueck-type example.

  • 27.
    Dan, Lilin
    et al.
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Peoples R China..
    Jiang, Tingmin
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Peoples R China..
    Xiao, Yue
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Peoples R China..
    Xiao, Ming
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Fang, Shu
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Peoples R China..
    Design of Offset Spatial Modulation OFDM2021In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 69, no 9, p. 6267-6280Article in journal (Refereed)
    Abstract [en]

    In this paper, the idea of offset spatial modulation (OSM) is integrated with orthogonal frequency division multiplexing (OFDM), toward an efficient design to bridge their advantages. Compared to its conventional counterpart as spatial modulation (SM)-OFDM, the proposed OSM-OFDM scheme aims at providing a simplified implementation structure with less number of radio frequency (RF) chains, by introducing an offset between the RF chain and the index of the activated transmit antenna on each subcarrier. Specifically, three types of offset antenna selection (OAS) methods are developed to meet different scene requirements for different number of available RF chains. Furthermore, through theoretical analysis, we quantify the bit error rate upper bounds of OSM-OFDM with different types of OAS methods. Finally, extensive computer simulations demonstrate that OSM-OFDM provides a flexible tradeoff among implementation cost, computation complexity and error performance.

  • 28.
    Della Penda, Demia
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fu, Liqun
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Energy efficient D2D communications in dynamic TDD systems2017In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 65, no 3, p. 1260-1273Article in journal (Refereed)
    Abstract [en]

    Device-to-Device (D2D) communication is a promising technology for improving the performance of proximity-based services. This paper demonstrates how the integration of D2D communication in cellular systems operating under dynamic Time Division Duplex (TDD) can improve energy efficiency. We perform joint optimization of mode selection, uplink/downlink transmission period, and power allocation to minimize the transmission energy consumption while satisfying a traffic requirement. Solutions are developed for two scenarios: with and without interference among D2D communications. Both formulations are expressed as mixed-integer nonlinear programming problems, which are NP hardin general. We exploit problem structure to develop efficient solutions for both scenarios. For the interference-free case, we develop algorithms that find the optimal solution in polynomial time. When considering interference, we propose a customized solver based on branch-and-bound that reduces the search complexity by taking advantage of the problem-specific proprieties. We complement this solver by a more practical heuristic algorithm. Simulation results demonstrate that D2D communications in dynamic TDD systems can yield significant energy savings and improved spectral efficiency compared to traditional cellular communication. Furthermore, we give analytical characterizations of the receiver locations relative to a given transmitter where D2D communication is optimal. These regions can be surprisingly large and not necessarily circular.

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    TC_2016
  • 29.
    Do, Hieu
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Chung, Sae-Young
    Korea Advanced Institute of Science and Technology (KAIST), School of EECS.
    Linear Beamforming and Superposition Coding with Common Information for the Gaussian MIMO Broadcast Channel2009In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 57, no 8, p. 2484-2494Article in journal (Refereed)
    Abstract [en]

    A Gaussian multiple-input multiple-output broadcast channel (MIMO GBC) is considered. Throughout the paper it is assumed that 1) input signals are Gaussian and 2) perfect channel state information is available at the transmitter and at the receivers. By considering each data stream as a single user, the uplink-downlink signal-to-interference-plus-noise (SINR) duality is generalized to the MIMO case with general cross-talk matrix. The duality is subsequently applied to finding the solution for the SINR-balancing problem. The result serves as a tool for characterizing achievable rate regions of different coding strategies. Next, we investigate a superposition coding scheme proposed by Cover-van der Meulen-Hajek and Pursley (nicknamed CMHP [1]), where there is a common message to both users. We consider a MIMO broadcast channel with two users, each user has two antennas and the transmitter has four antennas. Assuming one common stream is sent by CMHP coding and successive decoding, a lower bound to the CMHP rate region is found. Behaviors of the CMHP rate region and sumrate are analyzed. We find the sumrate gaps between DPC, CMHP, and MMSE at high SNR for general 2-user multiple-input single-output (MISO) Gaussian broadcast channel. The result suggests when CMHP is beneficial for sumrate.

  • 30.
    Do, Hieu
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Oechtering, Tobias
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On Asymmetric Interference Channels with Cooperating Receivers2013In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 61, no 2, p. 554-563Article in journal (Refereed)
    Abstract [en]

    This paper studies a model for communications in wireless networks supported by designated cooperation links. In particular, a 2-user Gaussian one-sided interference channel with two rate-limited and orthogonal communication links between the receivers is considered. A communication protocol for the channel is proposed, which combines rate-splitting and superposition encoding techniques with the conventional decode-forward and compress-forward strategies. It is shown that a careful design of codebooks and coding scheme, which is obtained from intuition based on superposition coding, can greatly reduce the complexity of the strategy. Analytical and numerical results show that the proposed scheme, although not universally optimal, can achieve the capacity region or sum capacity exactly or asymptotically in certain scenarios. Various limits of sum capacity gain due to cooperation are also discussed.

  • 31.
    Du, Jinfeng
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Larsson, Erik G.
    Division for Communication Systems, Linköping University.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Optimal Symbol-by-Symbol Costa Precoding for a Relay-Aided Downlink Channel2011In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 59, no 8, p. 2274-2284Article in journal (Refereed)
    Abstract [en]

    In this article, we consider practical approaches to Costa precoding (also known as dirty paper coding). Specifically, we propose a symbol-by-symbol scheme for cancellation of interference known at the transmitter in a relay-aided downlink channel. For finite-alphabet signaling and interference, we derive the optimal (in terms of maximum mutual information) modulator under a given power constraint. A sub-optimal modulator is also proposed by formulating an optimization problem that maximizes the minimum distance of the signal constellation, and this non-convex optimization problem is approximately solved by semi-definite relaxation. For the case of binary signaling with binary interference, we obtain a closed-form solution for the sub-optimal modulator, which only suffers little performance degradation compared to the optimal modulator in the region of interest. For more general signal constellations and more general interference distributions, we propose an optimized Tomlinson-Harashima precoder (THP), which uniformly outperforms conventional THP with heuristic parameters. Bit-level simulation shows that the optimal and sub-optimal modulators can achieve significant gains over the THP benchmark as well as over non-Costa reference schemes, especially when the power of the interference is larger than the power of the noise.

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  • 32.
    Du, Jinfeng
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Cooperative Network Coding Strategies for Wireless Relay Networks with Backhaul2011In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 59, no 9, p. 2502-2514Article in journal (Refereed)
    Abstract [en]

    We investigate cooperative network coding strategies for relay-aided two-source two-destination wireless networks with a backhaul connection between the source nodes. Each source multicasts information to all destinations using a shared relay. We study cooperative strategies based on different network coding schemes, namely, finite field and linear network coding, and lattice coding. To further exploit the backhaul connection, we also propose network coding based beamforming. We measure the performance in term of achievable rates over Gaussian channels, and observe significant gains over benchmark schemes. We derive the achievable rate regions for these schemes and find the cut-set bound for our system. We also show that the cut-set bound can be achieved by network coding based beamforming when the signal-to-noise ratios lie in the sphere defined by the source-relay and relay-destination channel gains.

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  • 33.
    Ericson, Thomas
    et al.
    Department of Electrical Engineering, Linköping University.
    Zander, Jens
    KTH, Superseded Departments (pre-2005), Teleinformatics.
    Meteor Burst Communication without feedback1995In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 43, no 234, p. 851-857Article in journal (Refereed)
    Abstract [en]

    Traditional meteor burst communication (MBC) systems are duplex (or half-duplex) systems. These systems provide the transmitter with feedback information for the detection of usable meteor trails. To achieve this feedback, a high power transmitter is required also at receive-only sites. In this paper, however, we discuss the application of channel coding to construct a true broadcast-type MBC system that allows for the simultaneous reception of messages at several receiving sites. Furthermore, MBC-systems without feedback allow for simple low power receivers that are impossible to to detect. Suitable codes, system performance and implementation complexity aspects are considered. Simulations with actual field trial data show that these systems are feasible and provide reliable, low-cost transmission of broadcast data.

  • 34.
    Fang, Shu
    et al.
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Sichuan, Peoples R China..
    Zheng, Kaili
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Sichuan, Peoples R China..
    Xiao, Yue
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Sichuan, Peoples R China..
    Yang, Yuming
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Sichuan, Peoples R China..
    Zeng, Xiaojuan
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Sichuan, Peoples R China..
    Xiao, Ming
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Offset Spatial Modulation and Offset Space Shift Keying: Efficient Designs for Single-RF MIMO Systems2019In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 67, no 8, p. 5434-5444Article in journal (Refereed)
    Abstract [en]

    Spatial modulation (SM) and space shift keying (SSK) techniques have the unique advantages of their single-radio-frequency (RF) structures compared with conventional multiple-input-multiple-output (MIMO) techniques. However, the transmission rates of these techniques are decided by the maximal switching frequency or by the minimal switching time between the RF chain and transmit antennas, which has been a bottleneck for their applications in future broadband wireless communications. To alleviate this problem, we propose a class of novel offset SM (OSM) and offset SSK (OSSK) schemes, with the aid of channel state information (CSI) at the transmitter. Compared with conventional SM and SSK, the proposed OSM and OSSK schemes can reduce the switching frequency of the RF chain, by introducing an offset between the connected RF chain and the index of the spatial modulated antenna. In extreme conditions, the proposed OSM and OSSK can work without RF switching while maintaining the single-RF advantage of conventional SM and SSK schemes. Through theoretical analysis, we also develop the bit-error rate (BER) performance bounds for the proposed two schemes. Finally, our simulation results demonstrate that the proposed OSM and OSSK outperform their counterparts, including conventional SM, SSK, CSI-aided SM, and CSI-aided SSK, while having a simplified RF-switching structure.

  • 35.
    Farhadi, Hamed
    et al.
    Chalmers University of Technology.
    Wang, Chao
    Tongji University.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fixed-rate Transmission over Fading Interference Channels Using Point-to-Point Gaussian Codes2015In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 63, no 10, p. 3633-3644Article in journal (Refereed)
    Abstract [en]

    This paper investigates transmission schemes for fixed-rate communications over a Rayleigh block-fading interference channel. There are two source-destination pairs where each source, in the presence of a short-term power constraint, intends to communicate with its dedicated destination at a fixed data rate. It encodes its messages using a point-to-point Gaussian codebook. The two users' transmissions can be conducted orthogonally or non-orthogonally. In the latter case, each destination performs either direct decoding by treating the interference as noise, or successive interference cancellation (SIC) to recover its desired message. For each scheme, we seek solutions of a power control problem to efficiently assign power to the sources such that the codewords can be successfully decoded at destinations. However, because of the random nature of fading, the power control problem for some channel realizations may not have any feasible solution and the transmission will be in outage. Thus, for each transmission scheme, we first compute a lower bound and an upper bound on the outage probability. Next, we use these results to find an outer bound and an inner bound on the epsilon-outage achievable rate region, i.e., the rate region in which the outage probability is below a certain value epsilon

  • 36. Feldbauer, C.
    et al.
    Kleijn, W. Bastiaan
    KTH, School of Electrical Engineering (EES), Sound and Image Processing.
    Scalable Coding with Side Information for Packet Loss Recovery2009In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 57, no 8, p. 2309-2319Article in journal (Refereed)
    Abstract [en]

    This paper presents a packet loss recovery method that uses an incomplete secondary encoding based on scalar quantization as redundancy. The method is redundancy bit rate scalable and allows an adaptation to varying loss scenarios and a varying packeting strategy. The recovery is performed by minimum mean squared error estimation incorporating a statistical model for the quantizers to facilitate real.-time adaptation. A bit allocation algorithm is proposed that extends 'reverse water filling' to the problem of scalar encoding dependent variables for a decoder with a final estimation stage and available side information. We apply the method to the encoding of line-spectral frequencies (LSFs), which are commonly used in speech coding, illustrating the good performance of the method.

  • 37.
    Femenias, Guillem
    et al.
    Univ Balear Isl UIB, Mobile Commun Grp, Palma De Mallorca 07122, Illes Balears, Spain..
    Riera-Palou, Felip
    Univ Balear Isl UIB, Mobile Commun Grp, Palma De Mallorca 07122, Illes Balears, Spain..
    Björnson, Emil
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Communication Systems, CoS.
    Another Twist to the Scalability in Cell-Free Massive MIMO Networks2023In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 71, no 11, p. 6793-6804Article in journal (Refereed)
    Abstract [en]

    Cell-free massive multiple-input multiple-output (MIMO) networks, where a massive number of geographically distributed access points cooperate to jointly serve the users, have been proved to solve many of the interference related issues associated to cellular networks. One of the main challenges of cell-free massive MIMO networks, however, is to guarantee that the potential benefits this architecture entails can be achieved with signal processing computational complexities and fronthaul resource requirements that are scalable as the number of users goes to infinity. User-centric architectures have been proposed in the literature that potentially solve the scalability issues related to, first, the signal processing associated to channel estimation and massive MIMO combining/precoding, second, the power allocation algorithms and, third, the fronthaul signaling for data and channel state information sharing. One of the best centralized combiners/precoders that have been proposed in practice, however, which is termed as partial minimum mean square error (P-MMSE), does not allow obtaining expressions of its spectral efficiency in a scalable way except when using lower bounds based on the well-known use-and-then-forget (UatF) approach. These lower bounds, however, in addition to being rather inaccurate, are not suited for the design and analysis of non-linear combining/precoding schemes based on successive interference cancellation (SIC) when users are equipped with multiple antennas. In this paper, we propose novel linear and non-linear combining/precoding schemes, which we term improved P-MMSE (IP-MMSE), whose achievable spectral efficiency can be accurately analyzed in a scalable manner. The proposed IP-MMSE combiner/precoder achieves spectral efficiencies close to that provided by MMSE-based unscalable solutions, and outperforms to a great extent the P-MMSE-based counterparts.

  • 38.
    Fischione, Carlo
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Buttissi, M.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    D'Angelo, M.
    Power and Rate Control with Outage Constraints in CDMA Wireless Networks2009In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 57, no 8, p. 2225-2229Article in journal (Refereed)
    Abstract [en]

    A radio power control strategy to achieve maximum throughput for the up-link of CDMA wireless systems with variable spreading factor is investigated. The system model includes slow and fast fading, rake receiver, and multi-access interference caused by users with heterogeneous data sources. The quality of the communication is expressed in terms of outage probability, while the throughput is defined as the sum of the users' transmit rates. The outage probability is accounted for by resorting to a lognormal approximation. A mixed integer-real optimization problem P-1, where the objective function is the throughput under outage probability constraints, is investigated. Problem P-1 is solved in two steps: firstly, we propose a modified problem P-2 to provide feasible solutions, and then the optimal solution is obtained with an efficient branch-and-bound search. Numerical results are presented and discussed to assess the validity of our approach.

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  • 39.
    Fischione, Carlo
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Jakobsson, Martin
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Optimality of Radio Power Control Via Fast-Lipschitz Optimization2016In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 64, no 6, p. 2589-2601Article in journal (Refereed)
    Abstract [en]

    In wireless network resource allocation, the radio power control problems are often solved by fixed point algorithms. Although these algorithms give feasible problem solutions, such solutions often lack notion of problem optimality. This paper reconsiders well-known fixed-point algorithms, such as those with standard and type-II standard interference functions, and investigates the conditions under which they give optimal solutions. The optimality is established by the recently proposed fast-Lipschitz optimization framework. To apply such a framework, the analysis is performed by a logarithmic transformation of variables that gives tractable fast-Lipschitz problems. It is shown how the logarithmic problem constraints are contractive by the standard or type-II standard assumptions on the power control problem, and how sets of cost functions fulfill the fast-Lipschitz qualifying conditions. The analysis on nonmonotonic interference function allows establishing a new qualifying condition for fast-Lipschitz optimization. The results are illustrated by considering power control problems with standard interference function, problems with type-II standard interference functions, and a case of subhomogeneous power control problems. Given the generality of fast-Lipschitz optimization compared to traditional methods for resource allocation, it is concluded that such an optimization may help to determine the optimality of many resource allocation problems in wireless networks.

  • 40. Floor, Pal Anders
    et al.
    Kim, Anna N.
    Ramstad, Tor A.
    Balasingham, Ilangko
    Wernersson, Niklas
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On Joint Source-Channel Coding for a Multivariate Gaussian on a Gaussian MAC2015In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 63, no 5, p. 1824-1836Article in journal (Refereed)
    Abstract [en]

    In this paper, nonlinear distributed joint source-channel coding (JSCC) schemes for transmission of multivariate Gaussian sources over a Gaussian multiple access channel are proposed and analyzed. The main contribution is a zero-delay JSCC named Distributed Quantizer Linear Coder (DQLC), which performs relatively close the information theoretical bounds, improves when the correlation among the sources increases, and does not level off as the signal-to-noise ratio (SNR) becomes large. Therefore it outperforms any linear solution for sufficiently large SNR. Further an extension of DQLC to an arbitrary code length named Vector Quantizer Linear Coder (VQLC) is analyzed. The VQLC closes in on the performance upper bound as the code length increases and can potentially achieve the bound for any number of independent sources. The VQLC leaves a gap to the bound whenever the sources are correlated, however. JSCC achieving the bound for arbitrary correlation has been found for the bivariate case, but that solution is significantly outperformed by the DQLC/VQLC when there is a low delay constraint. This indicates that different approaches are needed to perform close to the bounds when the code length is high and low. The VQLC/DQLC also apply for bandwidth compression of a multivariate Gaussian transmitted on point-to-point links.

  • 41. Floor, Pål Anders
    et al.
    Kim, Anna N.
    Wernersson, Niklas
    Ramstad, Tor A.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Balasingham, Ilangko
    Zero-Delay Joint Source-Channel Coding for a Bivariate Gaussian on a Gaussian MAC2012In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 60, no 10, p. 3091-3102Article in journal (Refereed)
    Abstract [en]

    In this paper, delay-free, low complexity, joint source-channel coding (JSCC) for transmission of two correlated Gaussian memoryless sources over a Gaussian Multiple Access Channel (GMAC) is considered. The main contributions of the paper are two distributed JSCC schemes: one discrete scheme based on nested scalar quantization, and one hybrid discrete-analog scheme based on a scalar quantizer and a linear continuous mapping. The proposed schemes show promising performance which improves with increasing correlation and are robust against variations in noise level. Both schemes also exhibit a constant gap to the performance upper bound when the channel signal-to-noise ratio gets large.

  • 42.
    Fodor, Gabor
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. Ericsson Research, Sweden.
    Di Marco, Piergiuseppe
    Telek, Miklos
    On the Impact of Antenna Correlation and CSI Errors on the Pilot-to-Data Power Ratio2016In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 64, no 6, p. 2622-2633Article in journal (Refereed)
    Abstract [en]

    In systems employing pilot-symbol aided channel estimation, the pilot-to-data power ratio is known to have a large impact on performance. Therefore, previous works proposed methods setting the pilot power such that either the weighted sum of the mean squared error (MSE) of the estimated data symbols is minimized or the overall spectral efficiency (SE) is maximized. However, previous works did not take into account the impact of correlated antennas and channel state information (CSI) errors on the optimal pilot power setting. In this paper, we consider the uplink of a multiuser multiple-input multiple-output (MU MIMO) system employing a receiver that minimizes the MSE of the received data symbols in the presence of CSI errors and derive closed-form expressions for theMSE and the achievable SE. These expressions take into account the impact of antenna correlation and CSI errors, and are a function of pilot power and the number of receive antennas. The analytical and numerical results can help set the pilot power, minimizing the MSE in multiple antenna systems.

  • 43.
    Fodor, Gabor
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control). Ericsson Res, S-16480 Stockholm, Sweden..
    Fodor, Sebastian
    Stockholm Univ, S-10691 Stockholm, Sweden..
    Telek, Miklos
    Budapest Univ Technol & Econ, H-1117 Budapest, Hungary.;MTA BME Informat Syst Res Grp, H-1117 Budapest, Hungary..
    MU-MIMO Receiver Design and Performance Analysis in Time-Varying Rayleigh Fading2022In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 70, no 2, p. 1214-1228Article in journal (Refereed)
    Abstract [en]

    Minimizing the symbol error in the uplink of multi-user multiple input multiple output systems is important, because the symbol error affects the achieved signal-to-interference-plus-noise ratio (SINR) and thereby the spectral efficiency of the system. Despite the vast literature available on minimum mean squared error (MMSE) receivers, previously proposed receivers for block fading channels do not minimize the symbol error in time-varying Rayleigh fading channels. Specifically, we show that the true MMSE receiver structure does not only depend on the statistics of the CSI error, but also on the autocorrelation coefficient of the time-variant channel. It turns out that calculating the average SINR when using the proposed receiver is highly non-trivial. In this paper, we employ a random matrix theoretical approach, which allows us to derive a quasi-closed form for the average SINR, which allows to obtain analytical exact results that give valuable insights into how the SINR depends on the number of antennas, employed pilot and data power and the covariance of the time-varying channel. We benchmark the performance of the proposed receiver against recently proposed receivers and find that the proposed MMSE receiver achieves higher SINR than the previously proposed ones, and this benefit increases with increasing autoregressive coefficient.

  • 44.
    Fodor, Gabor
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control). Ericsson Res, S-16480 Stockholm, Sweden.
    Fodor, Sebastian
    Stockholm Univ, S-10691 Stockholm, Sweden..
    Telek, Miklos
    Budapest Univ Technol & Econ, H-1111 Budapest, Hungary.;MTA BME Informat Syst Res Grp, H-1051 Budapest, Hungary..
    Performance Analysis of a Linear MMSE Receiver in Time-Variant Rayleigh Fading Channels2021In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 69, no 6, p. 4098-4112Article in journal (Refereed)
    Abstract [en]

    The performance of the uplink of single and multiuser multiple input multiple output (MIMO) systems depends crucially on the receiver architecture and the quality of channel state information at the receiver. Therefore, several previous works have developed minimum mean squared error (MMSE) receivers and proposed balancing the resources spent on acquiring channel state information and transmitting the payload of data packets. Somewhat surprisingly, the most popular MIMO linear MMSE receivers do not exploit the correlation structure that is present in autoregressive Rayleigh fading environments. Therefore, in this article we first develop a new linear receiver that not only takes channel state information errors into account in minimizing the MSE of the received data symbols, but it also utilizes that the subsequent noisy channel coefficients are correlated. For this new linear MMSE receiver, we derive the achieved MSE as a function of the number of receive antennas and the pilot-to-data power ratio. Interestingly, we find that the pilot power that minimizes the MSE of the data symbols does not depend on the number of antennas and that the new linear MMSE receiver outperforms previously proposed MIMO receivers when the autocorrelation coefficient of the channel is high.

  • 45.
    Fodor, Sebastian
    et al.
    Jane Street Capital, London, U.K.
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control). Ericsson Research, Stockholm, Sweden.
    Gurgunoglu, Doga
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control).
    Telek, Miklos
    Budapest University of Technology and Economics, Department of Networked Systems and Services, Budapest, Hungary; ELKH-BME Information Systems Research Group, Budapest, Hungary.
    Optimizing Pilot Spacing in MU-MIMO Systems Operating Over Aging Channels2023In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 71, no 6, p. 3708-3720Article in journal (Refereed)
    Abstract [en]

    In the uplink of multiuser multiple input multiple output (MU-MIMO) systems operating over aging channels, pilot spacing is crucial for acquiring channel state information and achieving high signal-to-interference-plus-noise ratio (SINR). Somewhat surprisingly, very few works examine the impact of pilot spacing on the correlation structure of subsequent channel estimates and the resulting quality of channel state information considering channel aging. In this paper, we consider a fast-fading environment characterized by its exponentially decaying autocorrelation function, and model pilot spacing as a sampling problem to capture the inherent trade-off between the quality of channel state information and the number of symbols available for information carrying data symbols. We first establish a quasi-closed form for the achievable deterministic equivalent SINR when the channel estimation algorithm utilizes multiple pilot signals. Next, we establish upper bounds on the achievable SINR and spectral efficiency, as a function of pilot spacing, which helps to find the optimum pilot spacing within a limited search space. Our key insight is that to maximize the achievable SINR and the spectral efficiency of MU-MIMO systems, proper pilot spacing must be applied to control the impact of the aging channel and to tune the trade-off between pilot and data symbols.

  • 46.
    Forssell, Karl Henrik
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Thobaben, Ragnar
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Worst-Case Detection Performance for Distributed SIMO Physical Layer Authentication2022In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 70, no 1, p. 485-499Article in journal (Refereed)
    Abstract [en]

    Feature-based physical layer authentication (PLA) schemes, using position-specific channel characteristics as identifying features, can provide lightweight protection against impersonation attacks in overhead-limited applications like e.g., mission-critical and low-latency scenarios. However, with PLA-aware attack strategies, an attacker can maximize the probability of successfully impersonating the legitimate devices. In this paper, we provide worst-case detection performance bounds under such strategies for a distributed PLA scheme that is based on the channel-state information (CSI) observed at multiple distributed remote radio-heads. This distributed setup exploits the multiple-channel diversity for enhanced detection performance and mimics distributed antenna architectures considered for 4G and 5G radio access networks. We consider (i) a power manipulation attack, in which a single-antenna attacker adopts optimal transmit power and phase; and (ii) an optimal spatial position attack. Interestingly, our results show that the attacker can achieve close-to-optimal success probability with only statistical CSI, which significantly strengthens the relevance of our results for practical scenarios. Furthermore, our results show that, by distributing antennas to multiple radio-heads, the worst-case missed detection probability can be reduced by 4 orders of magnitude without increasing the total number of antennas, illustrating the superiority of distributed PLA over a co-located antenna setup. 

  • 47.
    Ganesan, Unnikrishnan Kunnath
    et al.
    Linköping Univ, Dept Elect Engn ISY, S-58183 Linköping, Sweden..
    Björnson, Emil
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Communication Systems, CoS. Linköping Univ, Dept Elect Engn ISY, S-58183 Linköping, Sweden.
    Larsson, Erik G.
    Linköping Univ, Dept Elect Engn ISY, S-58183 Linköping, Sweden..
    Clustering-Based Activity Detection Algorithms for Grant-Free Random Access in Cell-Free Massive MIMO2021In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 69, no 11, p. 7520-7530Article in journal (Refereed)
    Abstract [en]

    Future wireless networks need to support massive machine type communication (mMTC) where a massive number of devices accesses the network and massive MIMO is a promising enabling technology. Massive access schemes have been studied for co-located massive MIMO arrays. In this paper, we investigate the activity detection in grant-free random access for mMTC in cell-free massive MIMO networks using distributed arrays. Each active device transmits a non-orthogonal pilot sequence to the access points (APs) and the APs send the received signals to a central processing unit (CPU) for joint activity detection. The maximum likelihood device activity detection problem is formulated and algorithms for activity detection in cell-free massive MIMO are provided to solve it. The simulation results show that the macro diversity gain provided by the cell-free architecture improves the activity detection performance compared to co-located architecture when the coverage area is large.

  • 48.
    Gao, Yulan
    et al.
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Sichuan, Peoples R China..
    Xiao, Yue
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Sichuan, Peoples R China.;Southeast Univ, Natl Mobile Commun Res Lab, Nanjing 210096, Jiangsu, Peoples R China..
    Wu, Mingming
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Sichuan, Peoples R China..
    Xiao, Ming
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Shao, Jinliang
    Univ Elect Sci & Technol China, Sch Math Sci, Chengdu 611731, Sichuan, Peoples R China..
    Dynamic Social-Aware Peer Selection for Cooperative Relay Management With D2D Communications2019In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 67, no 5, p. 3124-3139Article in journal (Refereed)
    Abstract [en]

    In this paper, we investigate the optimal dynamic social-aware peer selection with spectrum-power trading to maximize the average sum energy efficiency (EE) of cellular users (CUs) for uplink transmission for an orthogonal frequency division multiple access cellular network with device-to-device (D2D) communications. Different from the previous studies, which mostly focus on how to exploit social ties in human social networks to construct the permutation of all the feasible peers, we consider dynamic peer selection with social awareness-aided spectrum-power trading in D2D overlaying communications. Specifically, the amount of transmit power from the D2D transmitters to relay the CUs for uplink transmission is determined by their social trust levels. Likewise, the D2D transmitters can gain the corresponding amount of spectrum from the CUs for D2D pair link communications, which can be regarded as the compensation of the power consumption for relaying CUs. We formulate the dynamic peer selection problems with social awareness-aided spectrum-power trading in cooperative D2D communications into the infinite-horizon time-average renewal-reward problems subject to time average constraints on a collection of penalty processes. And the Lyapunov optimization concepts-based drift-plus-penalty algorithms are proposed to solve them. The simulation results demonstrate the effectiveness of the proposed dynamic peer selection algorithms. And further performance comparison indicates that the proposed dynamic peer selection algorithms not only maximize the average EE of CUs but also guarantee higher privacy protection.

  • 49.
    Gerami, Majid
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Li, Jun
    KTH, School of Electrical Engineering (EES).
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Lin, Z.
    Repair for distributed storage systems with packet erasure channels and dedicated nodes for repair2016In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 64, no 4, p. 1367-1383, article id 7422022Article in journal (Refereed)
    Abstract [en]

    We study the repair problem in distributed storage systems where storage nodes are connected through packet erasure channels and some nodes are dedicated to repair [termed as dedicated-for-repair (DR) storage nodes]. We first investigate the minimum required repair-bandwidth in an asymptotic setup, in which the stored file is assumed to have an infinite size. The result shows that the asymptotic repair-bandwidth over packet erasure channels with a fixed erasure probability has a closed-form relation to the repair-bandwidth in lossless networks. Next, we show the benefits of DR storage nodes in reducing the repair bandwidth, and then we derive the necessary minimal storage space of DR storage nodes. Finally, we study the repair in a nonasymptotic setup, where the stored file size is finite. We study the minimum practical-repair-bandwidth, i.e., the repair-bandwidth for achieving a given probability of successful repair. A combinatorial optimization problem is formulated to provide the optimal practical-repair-bandwidth for a given packet erasure probability. We show the gain of our proposed approaches in reducing the repair-bandwidth.

  • 50. Gezici, S.
    et al.
    Gholami, M. R.
    Bayram, S.
    Jansson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Jamming of Wireless Localization Systems2016In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 64, no 6, p. 2660-2676, article id 7460155Article in journal (Refereed)
    Abstract [en]

    In this paper, the optimal jamming of wireless localization systems is investigated. Two optimal power allocation schemes are proposed for jammer nodes in the presence of total and peak power constraints. In the first scheme, power is allocated to jammer nodes in order to maximize the average Cramér-Rao lower bound (CRLB) of target nodes, whereas in the second scheme, the power allocation is performed for the aim of maximizing the minimum CRLB of target nodes. Both the schemes are formulated as linear programs, and a closed-form solution is obtained for the first scheme. For the second scheme, under certain conditions, the property of full total power utilization is specified, and a closed-form solution is obtained when the total power is lower than a specific threshold. In addition, it is shown that non-zero power is allocated to at most NT jammer nodes according to the second scheme in the absence of peak power constraints, where NT is the number of target nodes. In the presence of parameter uncertainty, robust versions of the power allocation schemes are proposed. Simulation results are presented to investigate the performance of the proposed schemes and to illustrate the theoretical results.

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