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  • 51. Li, Jun
    et al.
    Lin, Zihuai
    Vucetic, Branka
    Xu, Jin
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Chen, Wen
    Threshold-Based One-Bit Soft Forwarding for a Network Coded Multi-Source Single-Relay System2014Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 62, nr 5, s. 1604-1620Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we propose a threshold-based one-bit soft forwarding (TOB-SF) protocol for a multi-source relaying system with network coding, where two sources communicate with the destination with the help of a relay. Specifically in the TOB-SF protocol, the relay calculates the log-likelihood ratio (LLR) value of each network coded symbol, compares this LLR value with a pre-optimized threshold, and determines whether to transmit or keep silent. We are interested in optimizing the TOB-SF protocol in fading channels, and consider both the uncoded and low-density parity check coded systems. In the uncoded system, we first derive the bit error rate (BER) expressions at the destination, based on which, we derive the optimal threshold. Then we theoretically prove that the system can achieve the full diversity gain by using this threshold. Further, we optimize the power allocation at the relay to achieve a higher coding gain. In the coded system, we first optimize the LLR threshold. Then we develop a methodology to track the BER evolution at the destination by using Gaussian approximations. Based on the BER evolution, we further optimize the power allocation at the relay which minimizes the system BER. Simulation results show that the proposed TOB-SF protocol outperforms other conventional relaying protocols in terms of error performance.

  • 52.
    Lim, Teng Joon
    et al.
    National University of Singapore.
    Rasmussen, Lars Kildehöj
    National University of Singapore.
    Adaptive symbol and parameter estimation in asynchronous multiuser CDMA detectors1997Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 45, nr 2, s. 213-220Artikel i tidskrift (Refereegranskat)
  • 53. Liu, Yanping
    et al.
    Fang, Xuming
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Discrete Power Control and Transmission Duration Allocation for Self-Backhauling Dense mmWave Cellular Networks2018Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 66, nr 1, s. 432-447Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wireless self-backhauling is a promising solution for dense millimeter wave (mmWave) small cell networks, the system efficiency of which, however, depends upon the balance of resources between the backhaul link and access links of each small cell. In this paper, we address the discrete power control and non-unified transmission duration allocation problem for self-backhauling mmWave cellular networks, in which each small cell is allowed to adopt individual transmission duration allocation ratio according to its own channel and load conditions. We first formulate the considered problem as a non-cooperative game G with a common utility function. We prove the feasibility and existence of the pure strategy Nash equilibrium (NE) of game G under some mild conditions. Then, we design a centralized resource allocation algorithm based on the best response dynamic and a decentralized resource allocation algorithm (DRA) based on control-plane/user-plane split architecture and loglinear learning to obtain a feasible pure strategy NE of game G. For speeding up convergence and reducing signaling overheads, we reformulate the considered problem as a non-cooperative game G' with local interaction, in which only local information exchange is required. Based on DRA, we design a concurrent DRA to obtain the best feasible pure strategy NE of game G'. Furthermore, we extend the proposed algorithms to the discrete power control and unified transmission duration allocation optimization problem. Extensive simulations are conducted with different system configurations to demonstrate the convergence and effectiveness of the proposed algorithms.

  • 54.
    Liu, Yanping
    et al.
    Southwest Jiaotong Univ, Key Lab Informat Coding & Transmiss, Chengdu 610031, Sichuan, Peoples R China..
    Fang, Xuming
    Southwest Jiaotong Univ, Key Lab Informat Coding & Transmiss, Chengdu 610031, Sichuan, Peoples R China..
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Mumtaz, Shahid
    Inst Telecomunicacoes, P-3810193 Aveiro, Portugal..
    Decentralized Beam Pair Selection in Multi-Beam Millimeter-Wave Networks2018Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 66, nr 6, s. 2722-2737Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Multi-beam concurrent transmission is one of promising solutions for a millimeter-wave (mmWave) network to provide seamless handover, robustness to blockage, and continuous connectivity. Nevertheless, one of the major obstacles in multi-beam concurrent transmissions is the optimization of beam pair selection, which is essential to improve the mmWave network performance. Therefore, in this paper, we propose a novel heterogeneous multi-beam cloud radio access network (HMBCRAN) architecture which provides seamless mobility and coverage for mmWave networks. We also design a novel acquirement method for candidate beam pair links (BPLs) in HMBCRANs architecture, which reduces user power consumption, signaling overhead, and overall time consumption. Based on HMBCRANs architecture and the resulted candidate BPLs for each user equipment, a beam pair selection optimization problem aiming at maximizing network sum rate is formulated. To find the solution efficiently, the considered problem is reformulated as a non-operative game with local interaction, which only needs local information exchanging among players. A decentralized algorithm based on HMBCRANs architecture and binary loglinear learning is proposed to obtain the optimal pure strategy Nash equilibrium of the proposed game, in which a concurrent multi-player selection scheme and an information exchanging protocol among players are developed to reduce the complexity and signal overheads. The stability, optimality, and complexity of the proposed algorithm are analyzed via theoretical and simulation method. The results prove that the proposed scheme has better convergence speed and sum rate against the state-ofthe- art schemes.

  • 55.
    Miao, Guowang
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Azari, Amin
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Hwang, Taewon
    E2-MAC: Energy Efficient Medium Access for Massive M2M Communications2016Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 64, nr 11, s. 4720-4735Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we investigate energy-efficient clustering and medium access control (MAC) for cellular-based M2M networks to minimize device energy consumption and prolong network battery lifetime. First, we present an accurate energy consumption model that considers both static and dynamic energy consumptions, and utilize this model to derive the network lifetime. Second, we find the cluster size to maximize the network lifetime and develop an energy-efficient cluster-head selection scheme.

    Furthermore, we find feasible regions where clustering is beneficial in enhancing network lifetime. We further investigate communications protocols for both intra- and inter-cluster communications. While inter-cluster communications use conventional cellular access schemes, we develop an energy-efficient and load-adaptive multiple access scheme, called n-phase CSMA/CA, which provides a tunable tradeoff between energy efficiency, delay, and spectral efficiency of the network. The simulation results show that the proposed clustering, cluster-head selection, and communications protocol design outperform the others in energy saving and significantly prolong the lifetimes of both individual nodes and the whole M2M network.

  • 56.
    Miao, Guowang
    et al.
    School of ECE, Georgia Institute of Technology.
    Himayat, Nageen
    Wireless Communications Lab., Intel Labs.
    Li, Geoffrey Ye
    School of ECE, Georgia Institute of Technology.
    Talwar, Shilpa
    Wireless Communications Lab., Intel Labs.
    Low-Complexity Energy-Efficient Scheduling for Uplink OFDMA2012Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 60, nr 1, s. 112-120Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Energy-efficient wireless communication is very important for battery-constrained mobile devices. For mobile devices in a cellular system, uplink power consumption dominates the wireless power budget because of RF power requirements for reliable transmission over long distances. Our previous work in this area focused on optimizing energy efficiency by maximizing the instantaneous bits-per-Joule metric through iterative approaches, which resulted in significant energy savings for uplink cellular OFDMA transmissions. In this paper, we develop energy efficient schemes with significantly lower complexity when compared to iterative approaches, by considering time-averaged bits-per-Joule metrics. We consider an uplink OFDMA system where multiple users communicate to a central scheduler over frequency-selective channels with high energy efficiency. The scheduler allocates the system bandwidth among all users to optimize energy efficiency across the whole network. Using time-averaged metrics, we derive energy optimal techniques in "closed forms" for per-user link adaptation and resource scheduling across users. Simulation results show that the proposed schemes not only have low complexity but also perform close to the globally optimum solutions obtained through exhaustive search.

  • 57. Nasir, A. A.
    et al.
    Mehrpouyan, H.
    Durrani, S.
    Blostein, S. D.
    Kennedy, R. A.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Optimal Training Sequences for Joint Timing Synchronization and Channel Estimation in Distributed Communication Networks2013Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 61, nr 7, s. 3002-3015Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For distributed multi-user and multi-relay cooperative networks, the received signal may be affected by multiple timing offsets (MTOs) and multiple channels that need to be jointly estimated for successful decoding at the receiver. This paper addresses the design of optimal training sequences for efficient estimation of MTOs and multiple channel parameters. A new hybrid Cramer-Rao lower bound (HCRB) for joint estimation of MTOs and channels is derived. Subsequently, by minimizing the derived HCRB as a function of training sequences, three training sequence design guidelines are derived and according to these guidelines, two training sequences are proposed. In order to show that the proposed design guidelines also improve estimation accuracy, the conditional Cramer-Rao lower bound (ECRB), which is a tighter lower bound on the estimation accuracy compared to the HCRB, is also derived. Numerical results show that the proposed training sequence design guidelines not only lower the HCRB, but they also lower the ECRB and the mean-square error of the proposed maximum a posteriori estimator. Moreover, extensive simulations demonstrate that application of the proposed training sequences significantly lowers the bit-error rate performance of multi-relay cooperative networks when compared to training sequences that violate these design guidelines.

  • 58.
    Nasiri Khormuji, Majid
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Zaidi, Ali A.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Interference Management Using Nonlinear Relaying2010Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 58, nr 7, s. 1924-1930Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We consider the three-node Gaussian relay channel where the relay observes a noisy version of the interference present in the source-destination link. We investigate three fundamental relaying approaches: linear relaying, memoryless nonlinear relaying, and compress-and-forward (CF). For interference-limited cases, we illustrate that optimized memoryless nonlinear relaying almost achieves the capacity.

  • 59.
    Negusse, Senay
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Zetterberg, Per
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Phase-noise mitigation in OFDM by best match trajectories2015Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 63, nr 5, s. 1712-1725Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper proposes a novel approach to phasenoise compensation. The basic idea is to approximate the phasenoise statistics by a finite number of realizations, i.e., a phasenoise codebook. The receiver then uses an augmented received signal model, where the codebook index is estimated along with other parameters. The realization of the basic idea depends on the details of the air interface, the phase-noise statistics, the propagation scenario and the computational constraints. In this paper, we will focus on a MQAM-OFDM system with pilot subcarriers within each OFDM symbol. The channel is frequency selective, fading and unknown. A decision-feedback method is employed to further enhance performance of the system. Simulation results are shown for uncoded and coded systems to illustrate the performance of the algorithm, which is als o compared with previously employed methods. Our simulation s show that for a 16-QAM coded OFDM system over a frequency selective Rayleigh fading channel affected by phase noise with root-mean-square (RMS) of 14.4 degrees per OFDM symbol, the proposed algorithm is 1.5dB from the ideal phase-noise free case at a BER of 10 − 4 . The performance of the best reference scheme is 2.5dB from the ideal case at BER of 10 − 4 . The proposed scheme is also computationally attractive.

  • 60. Nomikos, Nikolaos
    et al.
    Charalambous, Themistoklis
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Krikidis, Ioannis
    Skoutas, Dimitrios N.
    Vouyioukas, Demosthenes
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    A Buffer-Aided Successive Opportunistic Relay Selection Scheme With Power Adaptation and Inter-Relay Interference Cancellation for Cooperative Diversity Systems2015Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 63, nr 5, s. 1623-1634Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we present a relay selection scheme which combines the spectral efficiency of successive opportunistic relaying with the robustness of single-link relay selection. More specifically, we propose a scheme that minimizes the total energy expenditure per time slot under an inter-relay interference cancellation scheme. The new relay selection policy is analyzed in terms of outage probability and diversity by modeling the evolution of relay buffers as a Markov Chain. We construct the state transition matrix of the Markov Chain and obtain its stationary distribution, which in turn, yields the outage probability. The proposed scheme outperforms relevant state-of-the-art relay selection schemes in terms of throughput, diversity, energy efficiency and average delay, as demonstrated via representative numerical examples.

  • 61.
    Oechtering, Tobias J.
    et al.
    Technical University of Berlin, Heinrich-Hertz Chair for Mobile Communication, Berlin, Germany.
    Boche, Holger
    Stability region of an optimized bidirectional regenerative half-duplex relaying protocol2008Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 56, nr 9, s. 1519-1529Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, we study a cross-layer design of a spectrally efficient bidirectional relay communication in a three-node network using superposition encoding at the relay node. On the physical layer, a half-duplex relay node decodes-and-forwards the messages of two nodes in a two-phase protocol with optimal time-division. On the data link layer, we assume ergodic arrival processes at node 1 and 2 which have queues with infinite buffer length. At the beginning of each time-slot a centralized controller chooses the service rate pair which achieves the weighted rate sum maximum of the instantaneous achievable rate region for the block-fading channel state of the next time-slot with weights equal to the current buffer levels. To this end, the controller adjusts the time-division and relay power distribution. The policy is throughput optimal since the stability region is equal to the bidirectional ergodic rate region. This is because whenever the mean queue length is large, a negative drift of a quadratic Lyapunov function on the buffer levels can be proved.

  • 62.
    Oechtering, Tobias J.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jorswieck, Eduard A.
    Dresden University of Technology (TUD), Germany.
    Wyrembelski, Rafael F.
    Technische Universität Berlin, Heinrich- Hertz-Chair for Mobile Communications, Berlin, Germany.
    Boche, Holger
    Fraunhofer German-Sino Lab for Mobile Communications, Berlin, Germany.
    On the Optimal Transmit Strategy for the MIMO Bidirectional Broadcast Channel2009Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 57, nr 12, s. 3817-3826Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work the transmit covariance matrix optimization problem for the discrete memoryless MIMO Gaussian bidirectional broadcast channel is studied. A half-duplex relay node establishes bidirectional communication between two nodes using a decode-and-forward protocol. In the initial multiple access phase both nodes transmit their messages to the relay node. In the succeeding phase the relay broadcasts an optimal re-encoded message so that both nodes can decode the other's message using their own message as side information. The capacity region of the bidirectional broadcast channel is completely characterized by a weighted rate sum maximization problem, which can be solved by a simple iterative fixed point algorithm. If an efficient transmit covariance matrix is invariant with respect to the joint subspace spanned by the channels, then different combinations of the part transmitted on the orthogonal subspaces result in equivalent transmit strategies with different ranks. A closed-form procedure to obtain the optimal transmit covariance is derived for the case where the rank of the channels is equal to the number of antennas at the relay node and a full-rank transmission is optimal. It shows the complicated structure of the optimal eigenspace, which depends on the weights and the mean transmit power constraint. For parallel channels the optimal solution is completely characterized and discussed, which also solves the optimal power allocation problem for a single-antenna OFDM system.

  • 63.
    Ottosson, Tony
    et al.
    Department of Signals and Systems, Chalmers University of Technology.
    Skoglund, Mikael
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Joint source-channel and multiuser decoding for Rayleigh fading CDMA Channels2000Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 48, nr 1, s. 13-16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We consider joint source-channel and multiuser decoding for frequency-selective Rayleigh fading code-division multiple-access channels. The block source-channel encoder is defined by a vector quantizer, We investigate optimal (minimum mean-square error) decoding and user-separated decoding of lower complexity, The studied decoders are soft in the sense that they utilize all soft information available at the receiver. Simulations indicate significant performance gains of the introduced decoders compared with a tandem approach that uses maximum-likelihood multiuser detection plus table-lookup decoding.

  • 64.
    Parkvall, Stefan
    et al.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Strom, Erik G
    Department of Signals and Systems, Chalmers University of Technology, 412 96 G¨oteborg, Sweden.
    Milstein, Laurence B
    Wireless Communication, University of California, San Diego, La Jolla, CA 92093 USA.
    Ottersten, Björn
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Asynchronous near-far resistant DS-CDMA receivers without a priori synchronization1999Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 47, nr 1, s. 78-88Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, several receivers for data demodulation in an asynchronous direct-sequence code-division multiple access (DS-CDMA) system operating without prior knowledge of the propagation delays are proposed and compared. Special attention is paid to the near-far problem, and the proposed schemes are numerically shown to he near-far resistant, The near-far resistance is obtained by estimating the a priori unknown propagation delay using a subspace-based technique. Quantities obtained in the estimation procedure are used to design a filter used for suppression of interference, according to the minimum mean square error criterion. Either a decision feedback technique or a simple two-state Viterbi algorithm is subsequently used for the data demodulation in the uncoded case, By extending the trellis used in the Viterbi algorithm, error correcting coding is easily implemented.

  • 65. Pobloth, H.
    et al.
    Vafin, R.
    Kleijn, W. Bastiaan
    KTH, Skolan för elektro- och systemteknik (EES), Ljud- och bildbehandling.
    Multivariate block polar quantization2005Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 53, nr 12, s. 2043-2053Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We introduce multivariate block polar quantization (MBPQ). MBPQ minimizes the weighted squared-error distortion for a set of complex variables representing one block of a signal under a resolution constraint for the entire block. MBPQ performs below the lower bound for classical bivariate quantization, both for Gaussian complex variables and for complex variables found from sinusoidal analysis of audio data. Still, it is of similar complexity as traditional polar quantizers. In the case of audio data, we found a performance gain of about 2.5 dB over the best performing conventional resolution-constrained polar quantization (an extension of unrestricted polar quantization).

  • 66.
    Qi, Nan
    et al.
    KTH. Northwestern Polytechnical University, China.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Tsiftsis, Theodoros A.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Cao, Phuong
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Li, Lixin
    Energy-Efficient Cooperative Network Coding With Joint Relay Scheduling and Power Allocation2016Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 64, nr 11, s. 4506-4519Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The energy efficiency (EE) of a multi-user multi-relay system with the maximum diversity network coding (MDNC) is studied. We explicitly find the connection among the outage probability, energy consumption, and EE, and formulate the maximizing EE problem under the outage probability constraint. Relay scheduling (RS) and power allocation (PA) are applied to schedule the relay states (transmitting, sleeping, and so on) and optimize the transmitting power under the practical channel and power consumption models. Since the optimization problem is NP hard, to reduce computational complexity, the outage probability is first tightly approximated to a log-convex form. Furthermore, the EE is converted into a subtractive form based on the fractional programming. Then, a convex mixed-integer nonlinear problem is eventually obtained. With a generalized outer approximation algorithm, RS and PA are solved in an iterative manner. The Pareto-optimal curves between the EE and the target outage probability show the EE gains from PA and RS. Moreover, by comparing with the no network coding (NoNC) scenario, we conclude that with the same number of relays, MDNC can lead to EE gains. However, if RS is implemented, NoNC can outperform MDNC in terms of the EE when more relays are needed in the MDNC scheme.

  • 67.
    Rasmussen, Lars Kildehöj
    et al.
    National University of Singapore.
    Lim, Teng Joon
    National University of Singapore.
    Aulin, Tor M.
    Chalmers University of Technology.
    Breadth-first maximum likelihood detection in multiuser CDMA1997Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 45, nr 10, s. 1176-1178Artikel i tidskrift (Refereegranskat)
  • 68.
    Rasmussen, Lars Kildehöj
    et al.
    National University of Singapore.
    Lim, Teng Joon
    National University of Singapore.
    Johansson, Ann-Louise
    Chalmers University of Technology.
    A matrix-algebraic approach to successive interference cancellation in CDMA2000Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 48, nr 1, s. 145-151Artikel i tidskrift (Refereegranskat)
  • 69.
    Rasmussen, Lars Kildehöj
    et al.
    Georgia Institute of Technology.
    Wicker, Stephen B.
    Georgia Institute of Technology.
    TRELLIS-CODED, TYPE-I HYBRID-ARQ PROTOCOLS BASED ON CRC ERROR-DETECTING CODES1995Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 43, nr 10, s. 2569-2575Artikel i tidskrift (Refereegranskat)
  • 70.
    Schiessl, Sebastian
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Al-Zubaidy, Hussein
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Skoglund, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Gross, James
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Delay Performance of Wireless Communications With Imperfect CSI and Finite-Length Coding2018Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 66, nr 12, s. 6527-6541Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With the rise of critical machine-to-machine applications, next generation wireless communication systems must meet challenging requirements with respect to latency and reliability. A key question in this context relates to channel state estimation, which allows the transmitter to adapt the code rate to the channel state. In this paper, we characterize the tradeoff between the training sequence length and data codeword length: shorter channel estimation leaves more time for the payload transmission but reduces the estimation accuracy and causes more decoding errors. Using lower coding rates can mitigate this effect, but may result in a higher backlog of data at the transmitter. In order to optimize the training sequence length and the rate adaptation scheme with respect to the delay performance, we employ queuing analysis on top of accurate models of the physical layer. We obtain an analytically tractable solution to the problem by deriving a closed-form approximation for the decoding error probability due to imperfect channel knowledge and finite-blocklength channel coding. The optimized training sequence length and rate adaptation strategy can reduce the delay violation probability by an order of magnitude, compared with suboptimal strategies that do not consider the delay constraints.

  • 71.
    Schrammar, Nicolas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Transmission Strategies for Wireless Relay Networks Obtained from Linear Finite-Field Deterministic Models2012Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 60, nr 8, s. 2167-2176Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper we show how the recently proposed linear finite-field deterministic model (LFFM) can be used to design transmission strategies for the corresponding AWGN model of wireless relay networks. The transmission scheme in the AWGN model uses hierarchical modulation to transmit information on multiple layers. We show that a transmission strategy in the LFFM can be translated to the AWGN model if it is coordinated, that is, if the amount of interference is limited in a certain way. We consider two types of coordination, full and partial, with different restrictions on the transmission scheme. In both cases we show that the rate in the AWGN model is at most a constant gap below the rate in the LFFM, which provides a link between the models. Closed-form upper bounds on the gap are derived based on the analysis of noise and interference forwarding. The bounds are evaluated numerically, and the dependency on the system parameters and the parameters of coordination are discussed. The trade-off between full and partial coordination and the corresponding parameters are illustrated.

  • 72.
    Schrammar, Nicolas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Wang, Chao
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Rasmussen, Lars Kildehøj
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    New Achievable Rates for Gaussian Partially Cognitive Interference Channels With Multiple Cognitive Pairs2014Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 62, nr 6, s. 2051-2060Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper characterizes achievable rate regions for the Gaussian partially cognitive interference channel with multiple cognitive pairs (K-PCIFC), where the cognitive transmitters know one part of the primary transmitter's message. We explore a novel methodology using the deterministic discrete superposition model (DSM). We find codes and their achievable rate regions in the DSM, and we show that they yield achievable rate regions in the Gaussian model. Our coding scheme in the DSM can be applied in general scenarios. We devise an achievable rate region for the K-PCIFC, which is within a constant gap to known outer bounds for K = 2 in the weak interference regime. From our expressions we derive guidelines for designing the cognitive link between the primary transmitter and the cognitive transmitters. Furthermore, we show that the gain from cognition diminishes for increasing K.

  • 73.
    Shokri-Ghadikolaei, Hossein
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    The Transitional Behavior of Interference in Millimeter Wave Networks and Its Impact on Medium Access Control2015Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 64, nr 2, s. 723-740Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Millimeter wave (mmWave) communication systems use large number of antenna elements that can potentially overcome severe channel attenuation by narrow beamforming. Narrow-beam operation in mmWave networks also reduces multiuser interference, introducing the concept of noise-limited wireless networks as opposed to interference-limited ones. The noise-limited or interference-limited regime heavily reflects on the medium access control (MAC) layer throughput and on proper resource allocation and interference management strategies. Yet, these regimes are ignored in current approaches to mmWave MAC layer design, with the potential disastrous consequences on the communication performance. In this paper, we investigate these regimes in terms of collision probability and throughput. We derive tractable closed-form expressions for the collision probability and MAC layer throughput of mmWave ad hoc networks, operating under slotted ALOHA. The new analysis reveals that mmWave networks may exhibit a non-negligible transitional behavior from a noise-limited regime to an interference-limited one, depending on the density of the transmitters, density and size of obstacles, transmission probability, operating beamwidth, and transmission power. Such transitional behavior necessitates a new framework of adaptive hybrid resource allocation procedure, containing both contention-based and contention-free phases with on-demand realization of the contention-free phase. Moreover, the conventional collision avoidance procedure in the contention-based phase should be revisited, due to the transitional behavior of interference, to maximize throughput/delay performance of mmWave networks. We conclude that, unless proper hybrid schemes are investigated, the severity of the transitional behavior may significantly reduce throughput/delay performance of mmWave networks.

  • 74.
    Shokri-Ghadikolaei, Hossein
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Fodor, Gabor
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. Ericsson Res, Sweden.
    Popovski, Petar
    Aalborg Univ, Denmark.
    Zorzi, Michele
    Univ Padua, Italy.
    Millimeter Wave Cellular Networks: A MAC Layer Perspective2015Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 63, nr 10, s. 3437-3458Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The millimeter wave (mmWave) frequency band is seen as a key enabler of multi-gigabit wireless access in future cellular networks. In order to overcome the propagation challenges, mmWave systems use a large number of antenna elements both at the base station and at the user equipment, which lead to high directivity gains, fully-directional communications, and possible noise-limited operations. The fundamental differences between mmWave networks and traditional ones challenge the classical design constraints, objectives, and available degrees of freedom. This paper addresses the implications that highly directional communication has on the design of an efficient medium access control (MAC) layer. The paper discusses key MAC layer issues, such as synchronization, random access, handover, channelization, interference management, scheduling, and association. The paper provides an integrated view on MAC layer issues for cellular networks, identifies new challenges and tradeoffs, and provides novel insights and solution approaches.

  • 75.
    Si, Zhongwei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Bilayer LDPC Convolutional Codes for Decode-and-Forward Relaying2013Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 61, nr 8, s. 3086-3099Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper we present bilayer LDPC convolutional codes for half-duplex relay channels. Two types of codes, bilayer expurgated LDPC convolutional codes and bilayer lengthened LDPC convolutional codes, are proposed for decode-and-forward (DF) relaying. In the case of the binary erasure relay channel, we prove analytically that both code constructions achieve the capacities of the source-relay link and the source-destination link simultaneously, provided that the channel conditions are known when designing the codes. Meanwhile, both codes enable the highest transmission rate possible with DF relaying for a wide range of channel parameters. In addition, the regular degree distributions can easily be computed from the channel parameters, which significantly simplifies the code optimization. The code construction and performance analysis are extended to the general binary memoryless symmetric channel, where a capacity-achieving performance is conjectured. Numerical results are provided for both types of codes with finite node degrees over binary erasure channels and binary-input additive white Gaussian noise channels, which verify the aforementioned theoretical analysis.

  • 76.
    Skoglund, Mikael
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Larsson, Erik G.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Optimal Modulation for Known Interference2008Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 56, nr 11, s. 1892-1899Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a symbol-by-symbol approach to the problem of canceling known interference at the transmitter in a communication system. In the envisioned system, the modulator maps an information symbol (taken from a finite alphabet) and an interference symbol (from the complex field) onto a transmitted constellation point. Our scheme is based on joint optimization of a modulator and demodulator, subject to a constraint on the average transmit power. The demodulator picks the information symbol (as a function of the received symbol) that minimizes the average error probability. We emphasize that our focus is on transmission in a single (complex) dimension, and hence the proposed technique is a "modulation" rather than a "coding" scheme. We illustrate that the new scheme outperforms Tomlinson-Harashima precoding, which is a classical but suboptimal solution to the one-dimensional known-interference precoding problem. In our simulations, the new approach is able to perform close to the no-interference bound.

  • 77.
    Skoglund, Mikael O.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Bit-estimate based decoding for vector quantization over noisy channels with intersymbol interference2000Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 48, nr 8, s. 1309-1317Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We introduce new techniques for quantization over noisy channels with intersymbol interference. We focus on the decoding problem, and present a decoder structure that allows the decoding to be based on soft minimum mean-square-error estimates of the transmitted bits. The new bit-estimate based decoder provides a structured lower-complexity approximation of optimal decoding for general codebooks, and for so-called linear mapping codebooks, it is shown that its implementation becomes particularly simple, We investigate decoding based on optimal bit-estimates, and on suboptimal estimates of lower computational complexity. We also consider encoder optimization and combined source-channel code design. Numerical simulations demonstrate that bit estimate based de coding is able to outperform a two-stage decision-based approach implemented using Viterbi sequence detection plus table look-up source decoding. The simulations also show that decoding based on suboptimal bit-estimates performs well, at a considerably lowered complexity.

  • 78.
    Stathakis, Efthymios
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Rasmussen, Lars K.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. Univ S Australia, Inst Telecommun Res, Mawson Lakes 5095, Australia.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Closed-Form Capacity Result for Interference-Limited Environments With Mixed Fading2015Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 63, nr 6, s. 2374-2387Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study a multinode network, where a multiantenna transmitter T-x communicates with its desired receiver R-x, whereas a cluster P (sic) {P-x,P- n, n = 1,..., N} of unintended nodes is disturbed by the T-x-R-x (TR) communication. To prevent severe performance degradation, we impose a constraint on the total interference that is inflicted at the nodes of P. The TR link contains a line-of-sight component, whereas the propagation environment for each T-x-P-x, n link is shadowed. The T-x node is preprocessing the information sequence by means of a precoding matrix that is optimized to achieve the ergodic capacity under a constraint on the maximum admissible ergodic interference power, arriving on P. In this paper, we show that the optimum precoding strategy involves the transmission of a single stream over the precoding direction, i.e., the eigenvector of the precoding matrix, which corresponds to beamforming along the instantaneous direction of the TR-link channel. The solution of the remaining power allocation problem yields the optimal precoding matrix. For this setup, we provide an efficient stochastic characterization of the network, which allows us to obtain an analytical expression for the TR-link ergodic capacity; this problem has been previously open, even for the case of a single-antenna node T-x and a single-element set P. We complement the analysis by deriving the TR-link signal-to-noise ratio and the average bit error rate, which are associated with our transmission scheme. Numerical results corroborate the theoretical analysis and reveal an interplay between the network parameters and their impact on the TR-link performance.

  • 79.
    Stathakis, Efthymios
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Rasmussen, Lars K.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    On Beamforming and Orthogonal Space-Time Coding in Cognitive Networks with Partial CSI2013Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 61, nr 3, s. 961-972Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We consider a pair of secondary users that coexist, in a cognitive network, with multiple primary user pairs. The secondary link is supplied with partial network side information (NSI), which comprises message side information and partial channel side information (CSI), available in different levels at both the transmitter and the receiver of the cognitive link. The cognitive transceiver design has to obey predefined quality-of-service (QoS) criteria, that need to be maintained at the primary receivers, and at the same time properly handle the incoming interference from each primary transmitter in order to establish reliable communication. In this framework, we investigate the design and performance of the combined beamforming and orthogonal space-time block coding (BOSTBC) strategy, whose merits are well-documented, as a candidate transmission scheme for the secondary link. We study both aspects, QoS and interference, of the composite problem and characterize how they affect the beamformer design and the cognitive link performance, in the presence of partial NSI. Further, we propose a CSI quality-dependent model for the QoS criteria which yields an interesting trade-off between the cognitive link design and the primary QoS. Numerical results illustrate the system performance in this framework.

  • 80.
    Ström, Erik G
    et al.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Parkvall, Stefan
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Miller, Scott L
    Department of Electrical Engineering, University of Florida, Gainesville, FL 3261 1 USA.
    Ottersten, Björn
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Propagation delay estimation in asynchronous direct-sequence code-division multiple access systems1996Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 44, nr 1, s. 84-93Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In an asynchronous direct-sequence code-division multiple access CDS-CDMA) communication system, the parameter estimation problem, i.e., estimating the propagation delay, attenuation and phase shift of each user's transmitted signal, may be complicated by the so-called near-far problem. The near-far problem occurs when the amplitudes of the users' received signals are very dissimilar, as the case might be in many important applications, In particular, the standard method for estimating the propagation delays will fail in a near-far situation, Several new estimators, the maximum likelihood, an approximative maximum likelihood and a subspace-based estimator, are therefore proposed and are shown to be robust against the near-far problem, No knowledge of the transmitted bits is assumed, and the proposed estimators can thus be used for both acquisition and tracking. In addition, the Cramer-Rao bound is derived for the parameter estimation problem.

  • 81.
    Svedman, Patrick
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Wilson, Sarah Kate
    Department of Electrical Engineering, Santa Clara University, Santa Clara, USA.
    Cimini, Leonard J., Jr.
    e Electrical and Computer Engineering Department, University of Delaware, Newark, USA..
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Opportunistic beamforming and scheduling for OFDMA systems2007Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 55, nr 5, s. 941-952Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Orthogonal frequency-division multiple access (OFDMA) is an attractive technique for exploiting multiuser diversity in the downlink of a cellular system. This paper addresses three problems in multiuser diversity for OFDMA systems. First, we propose a way to significantly reduce the amount of channel state information (CSI) feedback without sacrificing performance too much, by selective and adaptive feedback. Second, we propose a way to increase the cell throughput and fairness by appying an opportunistic beamforming scheme to orthogonal frequency-division multiplexing. This beamforming scheme increases the frequency fading rate, which increases the multiuser diversity effect. Thirdly, we deal with the issue of fairness and quality-of-service (QoS) in opportunistic systems by proposing a modified proportional fair (PF) scheduler for OFDMA. Key features in the scheduler are that it incorporates QoS classes into the PF scheduler and that it has a tunable fairness level. Extensive simulation results are presented to evaluate. the performance of the proposed schemes. The opportunistic beamforming scheme performed well in comparison with several other schemes. The modified PF scheduler was able to give users different QoS, based on their requirements, while still exploiting multiuser diversity.

  • 82.
    Svedman, Patrick
    et al.
    KTH.
    Wilson, Sarah Kate
    Cimini, Leonard J., Jr.
    Ottersten, Björn
    KTH, Tidigare Institutioner (före 2005), Tal, musik och hörsel.
    Opportunistic beamforming and scheduling for OFDMA systems (vol 55, pg 941, 2007)2007Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 55, nr 6, s. 1266-1266Artikel i tidskrift (Refereegranskat)
  • 83.
    Takeuchi, Keigo
    et al.
    University of Electro-Communications, Department of Communication Engineering and Informatics.
    Müller, Ralf R.
    University Erlangen-Nürnberg.
    Vehkaperä, Mikko
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Iterative LMMSE Channel Estimation and Decoding Based on Probabilistic Bias2013Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 61, nr 7, s. 2853-2863Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Iterative channel estimation and decoding based on probabilistic bias is investigated. In order to control the occurrence probability of transmitted symbols, biased convolutional codes (CCs) are proposed. A biased CC is obtained by puncturing the parity bit of a conventional (unbiased) CC and by inserting a fixed bit at the punctured position when the state is contained in a certain subset of all possible states. A priori information about the imposed bias is utilized for the initial linear minimum mean-squared error (LMMSE) channel estimation. This paper focuses on biased turbo codes that are constructed as the parallel concatenation of two biased CCs with interleaving, and proposes an iterative LMMSE channel estimation and decoding scheme based on approximate belief propagation. The convergence property of the iterative LMMSE channel estimation and decoding scheme is analyzed via density evolution (DE). The DE analysis allows one to design the magnitude of the bias according to the coherence time, in terms of the decoding threshold. The proposed scheme is numerically shown to outperform conventional pilot-based schemes in the moderate signal-to-noise ratio (SNR) regime, at the expense of a performance degradation in the high SNR regime.

  • 84.
    Tan, Peng Hui
    et al.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Asymptotically optimal nonlinear MMSE multiuser detection based on multivariate Gaussian approximation2006Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 54, nr 8, s. 1427-1438Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a class of nonlinear minimum mean-squared error multiuser detectors is derived based on a multivariate Gaussian approximation of the multiple-access interference for large systems. This approach leads to expressions identical to those describing the probabilistic data association (PDA) detector, thus providing an alternative analytical justification for this structure. A simplification to the PDA detector based on approximating the covariance matrix of the multivariate Gaussian distribution is suggested, resulting in a soft interference-cancellation scheme. Corresponding multiuser soft-input, soft-output detectors delivering extrinsic log-likelihood ratios are derived for application in iterative multiuser decoders. Finally, a large-system performance analysis is conducted for the simplified PDA, showing that the bit-error rate (BER) performance of this detector can be accurately predicted and related to the replica method analysis for the optimal detector. Methods from statistical neurodynamics are shown to provide a closely related alternative large-system prediction. Numerical results demonstrate that for large systems, the BER is accurately predicted by the analysis and found to be close to optimal performance.

  • 85. Tan, Peng Hui
    et al.
    Rasmussen, Lars Kildehöj
    National University of Singapore.
    Linear interference cancellation in CDMA based on iterative techniques for linear equation systems2000Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 48, nr 12, s. 2099-2108Artikel i tidskrift (Refereegranskat)
  • 86. Tan, Peng Hui
    et al.
    Rasmussen, Lars Kildehöj
    National University of Singapore.
    Lim, Teng Joon
    National University of Singapore.
    Constrained maximum-likelihood detection in CDMA2001Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 49, nr 1, s. 142-153Artikel i tidskrift (Refereegranskat)
  • 87.
    Thobaben, Ragnar
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Kliewer, J.
    An Efficient Variable-Length Code Construction for Iterative Source-Channel Decoding2009Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 57, nr 7, s. 2005-2013Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a novel variable-length code (VLC) construction which exhibits an inherent error correcting capability due to the exclusive presence of codewords with even Hamming weight. Besides error robustness, the proposed code construction features a similar codeword length distribution as Golomb-Rice codes, and therefore, in particular for sources with exponentially distributed symbols, has good source compression properties at the same time. We show that in a source channel coding framework with outer source encoding, inner channel encoding with a recursive convolutional code, and iterative decoding the proposed VLC construction can. lead to significant performance improvements compared to fixed-length source encoding with optimized mappings. In particular, simulation results for the AWGN channel verify that for Gauss-Markov sources a performance close to the theoretical limit can be achieved.

  • 88.
    Thobaben, Ragnar
    et al.
    University of Kiel.
    Kliewer, J.
    University of Kiel.
    Low-complexity iterative joint source-channel decoding for variable-length encoded Markov sources2005Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 53, nr 12, s. 2054-2064Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we present a novel packetized bit-level decoding algorithm for variable-length encoded Markov sources, which calculates reliability information for the decoded bits in the form of a posteriori probabilities (APPs). An interesting feature of the proposed approach is that symbol-based source statistics in the form of the transition probabilities of the Markov source are exploited as a priori information on a bit-level trellis. This method is especially well-suited for long input blocks, since in contrast to other symbol-based APP decoding approaches, the number of trellis states does not depend on the packet length. When additionally the variable-length encoded source data is protected by channel codes, an iterative source-channel decoding scheme can be obtained in the same way as for serially concatenated codes. Furthermore, based on an analysis of the iterative decoder via extrinsic information transfer charts, it can be shown that by using reversible variable-length codes with a free distance of two, in combination with rate-1 channel codes and residual source redundancy, a reliable transmission is possible even for highly corrupted channels. This justifies a new source-channel encoding technique where explicit redundancy for error protection is only added in the source encoder.

  • 89.
    Tran, Le-Nam
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Juntti, Markku
    Bengtsson, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Weighted Sum Rate Maximization for MIMO Broadcast Channels Using Dirty Paper Coding and Zero-forcing Methods2013Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 61, nr 6, s. 2362-2373Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We consider precoder design for maximizing the weighted sum rate (WSR) of successive zero-forcing dirty paper coding (SZF-DPC). For this problem, the existing precoder designs often assume a sum power constraint (SPC) and rely on the singular value decomposition (SVD). The SVD-based designs are known to be optimal but require high complexity. We first propose a low-complexity optimal precoder design for SZF-DPC under SPC, using the QR decomposition. Then, we propose an efficient numerical algorithm to find the optimal precoders subject to per-antenna power constraints (PAPCs). To this end, the precoder design for PAPCs is formulated as an optimization problem with a rank constraint on the covariance matrices. A well-known approach to solve this problem is to relax the rank constraints and solve the relaxed problem. Interestingly, for SZF-DPC, we are able to prove that the rank relaxation is tight. Consequently, the optimal precoder design for PAPCs is computed by solving the relaxed problem, for which we propose a customized interior-point method that exhibits a superlinear convergence rate. Two suboptimal precoder designs are also presented and compared to the optimal ones. We also show that the proposed numerical method is applicable for finding the optimal precoders for block diagonalization scheme.

  • 90. Vehkapera, Mikko
    et al.
    Riihonen, Taneli
    Girnyk, Maksym A.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Bjornson, Emil
    Debbah, Merouane
    Kildehøj, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Wichman, Risto
    Asymptotic Analysis of SU-MIMO Channels With Transmitter Noise and Mismatched Joint Decoding2015Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 63, nr 3, s. 749-765Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hardware impairments in radio-frequency components of a wireless system cause unavoidable distortions to transmission that are not captured by the conventional linear channel model. In this paper, a "binoisy" single-user multiple-input multiple-output (SU-MIMO) relation is considered where the additional distortions are modeled via an additive noise term at the transmit side. Through this extended SU-MIMO channel model, the effects of transceiver hardware impairments on the achievable rate of multi-antenna point-to-point systems are studied. Channel input distributions encompassing practical discrete modulation schemes, such as, QAM and PSK, as well as Gaussian signaling are covered. In addition, the impact of mismatched detection and decoding when the receiver has insufficient information about the non-idealities is investigated. The numerical results show that for realistic system parameters, the effects of transmit-side noise and mismatched decoding become significant only at high modulation orders.

  • 91.
    Vehkaperä, Mikko
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Juntti, Markku
    Department of Electrical and Information Engineering, University of Oulu.
    On the Performance of Space-Time Coded and Spatially Multiplexed MIMO Systems with Linear Receivers2010Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 58, nr 2, s. 642-651Artikel i tidskrift (Refereegranskat)
  • 92.
    Wang, Chao
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Farhadi, Hamed
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Achieving the Degrees of Freedom of Wireless Multi-User Relay Networks2012Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 60, nr 9, s. 2612-2622Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the available degrees of freedom (DOF) of a class of wireless single-antenna multi-user relay networks. In these networks the communications between M unconnected source-destination pairs are provided by a large number of half-duplex relays. To conduct the communications we propose a cluster successive relaying protocol that divides the relays into two equal-size clusters. Unlike the conventional orthogonal relaying protocol that demands all the relays to simultaneously assist the sources, we require the two relay clusters to take turns forwarding the source messages to more efficiently use the channel. In a time-varying fading environment, through appropriate interference alignment the negative impact of inter-user interference can be effectively minimized. Thus the two clusters of half-duplex relays can mimic a cluster of full-duplex relays. When the number of relays is infinitely large, we show that the M-user half-duplex relay networks have M DOF, i.e. their sum capacity can be characterized as C-Sigma(SNR) = M log(SNR)+ o(log(SNR)). This result implies that allowing only distributed processing and half-duplex operation is able to provide the same DOF performance as permitting joint processing and full-duplex operation in wireless relay networks.

  • 93.
    Wang, Chao
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Diversity-Multiplexing Tradeoff Analysis of Coded Multi-User Relay Networks2011Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 59, nr 7, s. 1995-2005Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the impact of multiple access strategies on the diversity-multiplexing tradeoff (DMT) performance in wireless multi-user relay networks. The networks contain multiple independent sources, multiple half-duplex decode-and-forward (DF) relays, and one common destination. Instead of separately retransmitting each source message, the relays employ a class of spectrally efficient finite field network codes to assist the sources. It is shown that fully orthogonal or fully non-orthogonal transmission among sources/relays does not necessarily provide optimized DMT performance. We propose a novel transmission protocol that divides the sources and relays into individual clusters. The nodes within one cluster transmit non-orthogonally while the transmissions of different clusters span orthogonal channels. We provide the method to calculate the achievable DMT for each clustering strategy. The network DMT performance can thus be optimized by properly clustering the multiple sources and relays.

  • 94.
    Wang, Zhao
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Poor, H. Vincent
    Secure Degrees of Freedom of Wireless X Networks Using Artificial Noise Alignment2015Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 63, nr 7, s. 2632-2646Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The problem of transmitting confidential messages in M x K wireless X networks is considered in which each transmitter intends to send one confidential message to every receiver. In particular, the secure degrees of freedom (SDOF) of the considered network are studied based on an artificial noise alignment (ANA) approach, which integrates interference alignment and artificial noise transmission. At first, an SDOF upper bound is derived for the M x K X network with confidential messages (XNCM) to be K(M-1)/K+M-2. By proposing an ANA approach, it is shown that the SDOF upper bound is tight when K = 2 for the considered XNCM with time-/frequency-varying channels. For K >= 3, it is shown that SDOF of K(M-1)K+M-1 can be achieved, even when an external eavesdropper is present. The key idea of the proposed scheme is to inject artificial noise into the network, which can be aligned in the interference space at receivers for confidentiality. Moreover, for the network with no channel state information at transmitters, a blind ANA scheme is proposed to achieve SDOF of K(M-1)K+M-1 for K, M >= 2, with reconfigurable antennas at receivers. The proposedmethod provides a linear approach to secrecy coding and interference alignment.

  • 95.
    Wei, Lei
    et al.
    University of South Australia.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    A near ideal noise whitening filter for an asynchronous time-varying CDMA system1996Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 44, nr 10, s. 1355-1361Artikel i tidskrift (Refereegranskat)
  • 96.
    Wei, Lei
    et al.
    University of South Australia.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Wyrwas, Richard
    University of South Australia.
    Near optimum tree-search detection schemes for bit-synchronous multiuser CDMA systems over Gaussian and two-path Rayleigh-fading channels1997Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 45, nr 6, s. 691-700Artikel i tidskrift (Refereegranskat)
  • 97.
    Wernersson, Niklas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Karlsson, Johannes
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Distributed Quantization over Noisy Channels2009Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 57, nr 6, s. 1693-1700Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The problem of designing simple and energyefficient sensor nodes in a wireless sensor network is considered from a joint source-channel coding perspective. An algorithm for designing distributed scalar quantizers for orthogonal channels is proposed and evaluated. In particular the cases of the binary symmetric channel as well as the additive white Gaussian noise channel are studied. It is demonstrated that correlation between sources can be useful in order to reduce quantization distortion as well as protecting data when being transmitted over nonideal channels. It is also demonstrated that the obtained system is robust against channel SNR mismatch.

  • 98.
    Wernersson, Niklas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Nonlinear Coding and Estimation for Correlated Data in Wireless Sensor Networks2009Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 57, nr 10, s. 2932-2939Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The problem of designing simple and energy-efficient nonlinear distributed source-channel codes is considered. By demonstrating similarities between this problem and the problem of bandwidth expansion, a structure for source-channel codes is presented and analyzed. Based on this analysis an understanding about desirable properties for such a system is gained and used to produce an explicit source-channel code which is then analyzed and simulated. One of the main advantages of the proposed scheme is that it is implementable for many sources, contrary to most existing nonlinear distributed source-channel coding systems.

  • 99.
    Wernersson, Niklas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Sorting-Based Multiple Description Quantization2006Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 54, nr 9, s. 1521-1526Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We introduce a new method for multiple description quantization (MDQ), based on sorting a frame of samples and transmitting, as side-information/redundancy, an index that describes the resulting permutation. The sorting-based approach has a similar performance to multiple description scalar quantization and a flexible structure, providing straightforward implementation of multidimensional MDQ.

  • 100.
    Wernersson, Niklas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Ramstad, Tor
    Department of Electronics and Telecommunications, Norwegian University of Science and Technology, NTNU.
    Polynomial Based Analog Source-Channel Codes2009Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 57, nr 9, s. 2600-2606Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In many communication applications one is interested in transmitting a time-discrete analog-valued (i.e. continuous alphabet) source over a time-discrete analog channel. We study this problem in the case of bandwidth expansion, in the sense that one source sample, X, is transmitted over N orthogonal channels. An analog source-channel code based on orthogonal polynomials is proposed and analyzed. The code can be generated using a Gram-Schmidt procedure, to fit virtually any source distribution.

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