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  • 1.
    Björnson, Emil
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Devarakota, Pandu Ranga Rao
    IEE S.A., Zone Industrielle, 2b, Route de Tr`eves L-2632 Findel, Luxembourg.
    Medawar, Samer
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jorswieck, Eduard
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Schur-convexity of the Symbol Error Rate in Correlated MIMO Systems with Precoding and Space-time Coding2008Inngår i: Proceedings of the twentieth Nordic Conference on Radio Science and Communications, 2008Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    This paper analyzes the symbol error rate (SER) of spatially correlated multiple-input multiple-output (MIMO) systems with linear precoding, space-time block codes, and long-term statistical channel state information at the transmitter. Majorization theory and the notion of Schur-convexity is used to show how the SER depends on the signal-to-noise ratio (SNR), on the transmit and receive correlation, and on the choice of precoder. Depending on these conditions, the Chernoff bound on the SER is shown to be Schur- convex (i.e., increasing with the amount of correlation) with respect to the receive correlation, while it is Schur-convex at high SNR and Schur-concave (i.e., decreasing with increasing amount of correlation) at low SNR with respect to the transmit correlation. These properties are inherited by the exact SER, as shown analytically and illustrated numerically.

  • 2.
    Björnson, Emil
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jorswieck, Eduard A.
    Dresden University of Technology (TUD), Germany.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Impact of Spatial Correlation and Precoding Design in OSTBC MIMO Systems2010Inngår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 9, nr 11, s. 3578-3589Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The impact of transmission design and spatial correlation on the symbol error rate (SER) is analyzed for multi-antenna communication links. The receiver has perfect channel state information (CSI), while the transmitter has either statistical or no CSI. The transmission is based on orthogonal space-time block codes (OSTBCs) and linear precoding. The precoding strategy that minimizes the worst-case SER is derived for the case when the transmitter has no CSI. Based on this strategy, the intuitive result that spatial correlation degrades the SER performance is proved mathematically. In the case when the transmitter knows the channel statistics, the correlation matrix is assumed to be jointly-correlated (a generalization of the Kronecker model). The eigenvectors of the SER-optimal precoding matrix are shown to originate from the correlation matrix and the remaining power allocation is a convex problem. Equal power allocation is SER-optimal at high SNR. Beamforming is SER-optimal at low SNR, or for increasing constellation sizes, and its optimality range is characterized. A heuristic low-complexity power allocation is proposed and evaluated numerically. Finally, it is proved analytically that receive-side correlation always degrades the SER. Transmit-side correlation will however improve the SER at low to medium SNR, while its impact is negligible at high SNR.

  • 3.
    Björnson, Emil
    et al.
    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.
    Jorswieck, Eduard
    Communication Theory, Communications Laboratory, Dresden University of Technology, D-01062 Dresden, Germany.
    On the impact of spatial correlation and precoder design on the performance of MIMO systems with space-time coding2009Inngår i: 2009 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH, AND SIGNAL PROCESSING, VOLS 1- 8, PROCEEDINGS, IEEE , 2009, s. 2741-2744Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The symbol error performance of spatially correlated multi-antenna systems is analyzed herein. When the transmitter only has statistical channel information, the use of space-time block codes still permits spatial multiplexing and mitigation of fading. The statistical information can be used for precoding to optimize some quality measure. Herein, we analyze the performance in terms of the symbol error rate (SER). It is shown analytically that spatial correlation at the receiver decreases the performance both without precoding and with an SER minimizing precoder. Without precoding, correlation should also be avoided at the transmitter side, but with an SER minimizing precoder the performance is actually improved by increasing spatial correlation at the transmitter. The structure of the optimized precoder is analyzed and the asymptotic properties at high and low SNRs are characterized and illustrated numerically.

  • 4.
    Jarmyr, Simon
    et al.
    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.
    Jorswieck, Eduard A.
    Dresden University of Technology (TUD), Germany.
    Statistical Precoding With Decision Feedback Equalization Over a Correlated MIMO Channel2010Inngår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 58, nr 12, s. 6298-6311Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The decision feedback (DF) transceiver, combining linear precoding and DF equalization, can establish point-to-point communication over a wireless multiple-input multiple-output channel. Matching the DF-transceiver design parameters to the channel characteristics can improve system performance, but requires channel knowledge. We consider the fast-fading channel scenario, with a receiver capable of tracking the channel-state variations accurately, while the transmitter only has long-term, channel-distribution information. The receiver design problem given channel-state information is well studied in the literature. We focus on transmitter optimization, which amounts to designing a statistical precoder to assist the channel-tailored DF equalizer. We develop a design framework that encompasses a wide range of performance metrics. Common cost functions for precoder optimization are analyzed, thereby identifying a structure of typical cost functions. Transmitter design is approached for typical cost functions in general, and we derive a precoder design formulation as a convex optimization problem. Two important subclasses of cost functions are considered in more detail. First, we explore a symmetry of DF transceivers with a uniform subchannel rate allocation, and derive a simplified convex optimization problem, which can be efficiently solved even as system dimensions grow. Second, we explore the tractability of a certain class of mean square error based cost functions, and solve the transmitter design problem with a simple algorithm that identifies the convex hull of a set of points in R-2. The behavior of DF transceivers with optimal precoders is investigated by numerical means.

  • 5.
    Jorswieck, Eduard
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Lack of duality between SISO Gaussian MAC and BC with statistical CSIT2006Inngår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 42, nr 25, s. 1466-1468Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recently, the duality between capacity regions of certain single and multiple antenna MAC with SIC and BC with DPC was proved under the assumption of perfect CSI at the transmitter as well as the receiver. Considered is the case in which the transmitter has only statistical CSI.. It is shown that the average rate region of the SISO BC is a subset of the average rate region of the SISO MAC and that there is a lack of duality between the MAC and BC.

  • 6.
    Jorswieck, Eduard
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Uplink throughput maximization with combined sum and individual power constraints2006Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 10, nr 12, s. 816-818Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Optimal power allocation in cellular uplink systems is used to maximize the average throughput under individual and sum power constraints. In the uplink, the transmit power of the mobiles is limited leading to individual power constraints. Additionally, in order to reduce the inter-cell interference, the sum power is constraint. First, we approximate the individual and sum power constraints by a combined constraint on a suitable l-norm of the power allocation vector. Then, we derive the optimal power allocation for individual and sum power constraints as well as for the combined constraint for the three CSI scenarios with uninformed transmitter, long-term feedback, and perfect CSI. The results and illustrations show that under combined sum and individual power constraints completely different power allocation strategies are optimal than with pure sum or pure individual power constraints.

  • 7.
    Jorswieck, Eduard A.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Boche, Holger
    Delay-limited capacity: Multiple antennas, moment constraints, and fading statistics2007Inngår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 6, nr 12, s. 4204-4208Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Different performance measures are an important mean in order to analyze and design wireless communications systems. Examples of common performance measures are the ergodic capacity, the outage capacity, and the average mean-square error (MSE). In this work, we study the delay-limited capacity (DLC). The DLC depends on the properties of the fading channel, e.g. on the spatial correlation and on the line-of-sight (LOS) component. In this letter, we derive the DLC for the general class of parallel fading channels, including the multiple antenna channels under moment and long-term power constraint. We prove that the DLC is Schur-concave with respect to the spatial correlation in single-input multiple-output (SIMO), and multiple-input single-output (MISO). Bounds for the DLC of multiple-input multiple-output (MIMO) and parallel fading channels are derived and the impact of the the mean component and spatial correlation on these bounds is characterized.

  • 8.
    Jorswieck, Eduard A.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Boche, Holger
    Fraunhofer German-Sino Lab for Mobile Communications, Berlin, Germany.
    Majorization and Matrix-monotone Functions in Wireless Communications2007Bok (Annet vitenskapelig)
    Abstract [en]

    This short tutorial presents two mathematical techniques namely Majorization Theory and Matrix-Monotone Functions, reviews their basic definitions and describes their concepts clearly with many illustrative examples. In addition to this tutorial, new results are presented with respect to Schur-convex functions and regarding the properties of matrix-monotone functions.

      The techniques are applied to solve communication and information theoretic problems in wireless communications. The impact of spatial correlation in multiple antenna systems is characterized for many important performance measures, e.g., average mutual information, outage probability, error performance, minimum and wideband slope, zero-outage capacity, and capacity region. The impact of user distribution in cellular systems is characterized for different scenarios including perfectly informed transmitters and receivers, regarding, e.g., the average sum rate, the outage sum rate, maximum throughput. Finally, a unified framework for the performance analysis of multiple antenna systems is developed based on matrix-monotone functions. The optimization of transmit strategies for multiple antennas is carried out by optimization of matrix-monotone functions. The results within this framework resemble and complement the various results on optimal transmit strategies in single-user and multiple-user multiple-antenna systems.

  • 9.
    Jorswieck, Eduard A.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Hammarwall, David
    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.
    Ergodic capacity achieving transmit strategy in MIMO systems with statistical and short-term norm CSI2007Inngår i: 2007 IEEE International Conference on Acoustics, Speech, and Signal Processing, IEEE , 2007, s. 393-396Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The type and quality of the channel state information at the transmitter of a fading multiple-input multiple-output system greatly affects the ergodic capacity of the wireless link. In order to compare and unify the different proposals of transmit strategies for different scenarios, recently classes of MIMO channels are introduced that share a common optimal transmit strategy. In this work, we derive the ergodic capacity achieving transmit strategy for the class of unitary invariant norm feedback which complements statistical channel information at the transmitter. The impact of the short-term feedback quality is illustrated by the beamforming optimality range. The higher the feedback norm is the more likely is single stream beamforming to be optimal.

  • 10.
    Jorswieck, Eduard A.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Larsson, Erik G.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Multiuser gaussianity and constellation randomization for the MIMO multiple access channel: A unified view2007Inngår i: 2007 IEEE 8th Workshop On Signal Processing Advances In Wireless Communications, Vols 1 And 2, IEEE , 2007, s. 126-130Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In recent analyses of multiuser MIMO systems and their capacity achieving transmit strategies, Gaussian codebooks; are usually used. For the case in which the input signals are constrained to belong to a finite constellation, we study and explain two effects, namely Multiuser Gaussianity (MuG) and constellation randomization (CoRa). MuG means that the more users transmit simultaneously, the higher is the similarity of the received density to the optimal Gaussian one. Hence, the instantaneous mutual information is increased by MuG. This leads to a tradeoff between multiuser diversity and MuG. On the other hand, CoRa is done by linear precoding by random unitary matrices. Based on the observations from MuG, we explain why the outage capacity is increased by CoRa. The effects are illustrated by various numerical simulations.

  • 11.
    Jorswieck, Eduard A.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Larsson, Erik G.
    Linköping University Department of Electrical Engineering (ISY) Division of Communication Systems.
    The MISO interference channel from a game-theoretic perspective: A combination of selfishness and altruism achieves Pareto optimality2008Inngår i: 2008 IEEE International Conference On Acoustics, Speech And Signal Processing: Vols 1-12, 2008, s. 5364-5367Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We study the MISO interference channel from a game-theoretic perspective. Recently, it was shown that the rates at the non-cooperative Nash equilibrium (NE) strategy are poor especially in the medium and high SNR regimes. A reasonable outcome of the cooperative approach, close to the Pareto boundary of the achievable rate region, was shown to be the zero-forcing (ZF) strategy. In this work, we prove that any point on the Pareto boundary can be achieved by a certain linear combination of the NE and ZF strategies. A scalar weight per user chooses between "selfish" (NE) and altruistic (ZF) behavior. Thereby, the difficult beamforming optimization is reduced to a simple weight optimization. Different optimal operating points, e.g. maximum weighted sum-rate, the Nash-bargaining solution, or the Egalitarian solution, can be obtained by a computationally efficient iterative algorithm. The results are characterized by instantaneous achievable rate regions and the corresponding operating points.

  • 12.
    Jorswieck, Eduard A.
    et al.
    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.
    Sezgin, Aydin
    Information Systems Laboratory, Computer Forum, Department of Electrical Engineering, School of Engineering, Stanford University, USA.
    Paulraj, Arogyasvsami
    Information Systems Laboratory, Computer Forum, Department of Electrical Engineering, School of Engineering, Stanford University, USA.
    Guaranteed performance region in fading orthogonal space-time coded broadcast channels2008Inngår i: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recently, the capacity region of the MIMO broadcast channel (BC) was completely characterized and duality between MIMO multiple access channel (MAC) and MIMO BC with perfect channel state information (CSI) at transmitter and receiver was established. In this work, we propose a MIMO BC approach in which only information about the channel norm is available at the base and hence no joint beamforming and dirty paper precoding (DPC) can be applied. However, a certain set of individual performances in terms of MSE or zero-outage rates can be guaranteed at any time by applying an orthogonal space-time block code (OSTBC). The guaranteed MSE region without superposition coding is characterized in closed form and the impact of diversity, fading statistics, and number of transmit antennas and receive antennas is analyzed. Finally, six CSI and precoding scenarios with different levels of CSI and precoding are compared numerically in terms of their guaranteed MSE region. Depending on the long-term SNR, superposition coding as well as successive interference cancellation (SIC) with norm feedback performs better than linear precoding with perfect CSI.

  • 13.
    Jorswieck, Eduard A.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Sezgin, Aydin
    Information Systems Laboratory, Stanford University, USA.
    Paulraj, Arogyaswami
    Information Systems Laboratory, Stanford University, USA.
    Guaranteed performance region in fading orthogonal space-time coded broadcast channels2007Inngår i: 2007 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY PROCEEDINGS, NEW YORK: IEEE , 2007, s. 96-100Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Recently, the capacity region of the MIMO broadcast channel (BC) was completely characterized and duality between MIMO multiple access channel (MAC) and MIMO BC with perfect channel state information (CSI) at transmitter and receiver was established. In this work, we propose a MIMO BC approach in which only information about the channel norm is available at the base and hence no dirty paper precoding (DPC) can be applied. However, a certain set of individual performances in terms of MSE or zero-outage rates can be guaranteed at any time by applying an orthogonal space time block code (OSTBC). The guaranteed MSE region without superposition coding is characterized in closed form and the impact of diversity, fading statistics, and number of transmit antennas is analyzed. The guaranteed MSE region with superposition coding is also studied. Finally, the guaranteed sum MSE is briefly discussed.

  • 14.
    Jorswieck, Eduard A.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Sezgin, Aydin
    Information Systems Laboratory, Stanford University, USA.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Paulraj, Arogyasvsami
    Information Systems Laboratory, Stanford University, USA.
    Feedback reduction in uplink MIMO OFDM systems by chunk optimization2008Inngår i: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The performance of multiuser MIMO systems can be significantly increased by channel-aware scheduling and signal processing at the transmitters based on channel state information. In the multiple antenna uplink multicarrier scenario, the base station decides centrally on the optimal signal processing and spectral power allocation as well as scheduling. An interesting challenge is the reduction of the overhead in order to inform the mobiles about their transmit strategies. In this work, we propose to reduce the feedback by chunk processing and quantization. We maximize the weighted sum rate of a MIMO OFDM MAC under individual power constraints and chunk size constraints. An efficient iterative algorithm is developed and convergence is proved. The feedback overhead as a function of the chunk size is considered in the rate computation and the optimal chunk size is determined by numerical simulations for various channel models. Finally, the issues of finite modulation and coding schemes as well as quantization of the precoding matrices are addressed.

  • 15.
    Jorswieck, Eduard A.
    et al.
    Dresden University of Technology (TUD), Germany.
    Sezgin, Aydin
    Information Systems Laboratory, Stanford University, USA.
    Zhang, Xi
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Framework for Analysis of Opportunistic Schedulers: Average Sum Rate vs. Average Fairness2008Inngår i: Proceedings of the 6th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks, WiOpt 2008, 2008, s. 100-105Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Channel aware and opportunistic scheduling algorithms exploit the channel knowledge and fading to increase the average throughput. The maximum throughput scheduler (MTS) transmits only to the best user at a time. It is unfair to users at the cell edge. Obviously, there is a tradeoff between average throughput and fairness in the system. In this work, we study four representative schedulers, namely the MTS, the proportional fair scheduler (PFS), the (relative) opportunistic round robin scheduler (ORS), and the round robin scheduler (RRS). We show that the average sum rate performance and the average worst-case delay depend strongly on the user distribution within the cell. MTS gains from asymmetrically distributed users whereas the other three schedulers suffer. On the other hand, the average fairness of MTS and PFS decreases with asymmetrical user distribution. The key contribution of this paper is to put these tradeoffs and observations on a solid theoretical basis. The scaling laws of the average sum rate with the number of users as well as of the average worst-case delay are derived. Both the PFS and the ORS provide a reasonable performance in terms of throughput and fairness. However, PFS outperforms ORS for symmetrical user distributions, whereas ORS outperforms PFS for asymmetrical user distributions.

  • 16.
    Jorswieck, Eduard A.
    et al.
    Dresden University of Technology (TUD), Germany.
    Sezgin, Aydin
    Information Systems Laboratory, Stanford University, USA.
    Zhang, Xi
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Throughput versus Fairness: Channel-Aware Scheduling in Multiple Antenna Downlink2009Inngår i: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, s. 271540-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Channel aware and opportunistic scheduling algorithms exploit the channel knowledge and fading to increase the average throughput. Alternatively, each user could be served equally in order to maximize fairness. Obviously, there is a tradeoff between average throughput and fairness in the system. In this paper, we study four representative schedulers, namely the maximum throughput scheduler (MTS), the proportional fair scheduler (PFS), the (relative) opportunistic round robin scheduler (ORS), and the round robin scheduler (RRS) for a space-time coded multiple antenna downlink system. The system applies TDMA based scheduling and exploits the multiple antennas in terms of spatial diversity. We show that the average sum rate performance and the average worst-case delay depend strongly on the user distribution within the cell. MTS gains from asymmetrical distributed users whereas the other three schedulers suffer. On the other hand, the average fairness of MTS and PFS decreases with asymmetrical user distribution. The key contribution of this paper is to put these tradeoffs and observations on a solid theoretical basis. Both the PFS and the ORS provide a reasonable performance in terms of throughput and fairness. However, PFS outperforms ORS for symmetrical user distributions, whereas ORS outperforms PFS for asymmetrical user distribution.

  • 17.
    Jorswieck, Eduard A.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Svedman, Patrick
    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.
    Performance of TDMA and SDMA based Opportunistic Beamforming2008Inngår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 7, nr 11, s. 4058-4063Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, we analyze opportunistic beamforming with finite number of single-antenna users under the constraint that the feedback overhead from the mobiles to the base is constant. First, we characterize the impact of the fading variances of the users and the spatial correlation on the sum rate of TDMA based opportunistic beamforming using majorization theory. Further, we describe quantitatively the high-SNR behavior in terms of throughput slope and power offset. Next, the impact of the fading variances of the users on an upper bound of the sum rate for space division multiple access (SDMA) based opportunistic beamforming is derived which is tight for high SNR. We propose to adapt the number of active beams to the SNR and the number of active users in a cell and illustrate the corresponding optimization problem by simulations.

  • 18.
    Jorswieck, Eduard
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Sezgin, Aydin
    Information Systems Laboratory Stanford University, USA.
    Paulraj, Arogyaswami
    Information Systems Laboratory Stanford University, USA.
    Feedback reduction in uplink MIMO OFDM systems by chunk optimization2008Inngår i: 2008 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, PROCEEDINGS, 2008, s. 4348-4352Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The performance of multiuser MIMO systems can be significantly increased by channel aware scheduling and signal processing at the transmitters based on channel state information. In the multiple-antenna uplink multi-carrier scenario, the base station decides centrally on the optimal signal processing and spectral power allocation as well as scheduling. An interesting challenge is the reduction of the overhead in order to inform the mobiles about their transmit strategies. In this work, we propose to reduce the feedback by chunk processing and quantization. We maximize the weighted sum rate of a MIMO OFDM MAC under individual power constraints and chunk size constraints. An efficient iterative algorithm is developed and convergence proved. The feedback overhead as a function of the chunk size is considered in the rate computation and the optimal chunk size is determined by numerical simulations for various channel models. Finally, the issues of finite modulation and coding schemes as well as quantization of the precoding matrices are addressed.

  • 19.
    Järmyr, Simon
    et al.
    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.
    Jorswieck, Eduard
    Communication Theory, Communications Laboratory, Dresden University of Technology, D-01062 Dresden, Germany.
    Optimal V-BLAST ordering in fast Rayleigh fading: A linear assignment problem2011Inngår i: IEEE International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), 2011, s. 366-370Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We explore a novel approach to perform decoding-order optimization in the vertical Bell Labs layered space-time (V-BLAST) architecture. Allowing for simultaneous transmission of multiple, separately encoded data streams, the V-BLAST transmit-receive scheme applies to the uplink of a multi-user communication system. A multi-antenna receiver decodes data streams successively, dealing with inter-stream interference by means of cancelling and nulling; interference from previously decoded streams is cancelled by subtraction, and remaining interference is nulled by linear equalization. The order in which the streams are decoded can have a noticeable impact on system performance. We consider the optimization of a fixed decoding order in fast Rayleigh fading, based on long-term channel-fading parameters. For a wide range of performance measures, we show that the fast-fading ordering problem can be treated as a classical linear assignment problem, allowing a solution using existing, efficient algorithms.

  • 20.
    Järmyr, Simon
    et al.
    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.
    Jorswieck, Eduard
    Dresden University of Technology, Germany.
    Statistical Precoding and Detection Ordering in MIMO Multiple-Access Channels with Decision Feedback Equalization2011Inngår i: 2011 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), New York: IEEE , 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present a novel approach for joint transmitter-receiver design in the uplink of a wireless multiple-input multiple-output communication system. It applies to, e. g., a fast-fading frequency-division duplexing system with periodic pilot signaling from each user - a scenario hindering transmitter optimization based on channel state information (CSI), while CSI-based receiver optimization is possible. Each user multiplexes data onto several, independently coded data streams processed by a linear precoder, and detected at a base station (BS) employing zero-forcing decision feedback (DF) equalization, eliminating all interference prior to detection. We target the problem of jointly designing fixed linear precoders for all users as well as a fixed detection order for the DF receiver based on long-term channel statistics. We propose an efficiently implementable alternating-minimization technique that is verified numerically to converge fast, and to outperform the popular V-BLAST scheme -a computationally more complex ordered-DF receiver with limited applicability by requiring equal-rate data streams in the system.

  • 21.
    Lv, Jing
    et al.
    Dresden University of Technology.
    Blasco-Serrano, Ricardo
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jorswieck, Eduard
    Dresden University of Technology.
    Thobaben, Ragnar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Kliks, Adrian
    Poznan University of Technology.
    Optimal beamforming in MISO cognitive channels with degraded message sets2012Inngår i: Wireless Communications and Networking Conference (WCNC), 2012 IEEE, IEEE Communications Society, 2012, s. 538-543Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we consider the coexistence of a single-input single-output (SISO) primary link with a multiple-input single-output (MISO) secondary user pair that has non-causal knowledge of the primary message. We study an achievable rate region that exploits this knowledge by combining selfless relaying to maintain the rate supported by the primary link with dirty paper coding to pre-cancel the interference at the secondary receiver. We find the optimal choice of power allocation between these operating modes at the secondary transmitter as well as the optimal beamforming vectors. Moreover, we address the robustness of the solution to uncertainties in the channel knowledge. Finally, we show by numerical evaluation the gains obtained due to the additional knowledge of the primary message.

  • 22.
    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 Channel2009Inngår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 57, nr 12, s. 3817-3826Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 23.
    Osseiran, Afif
    et al.
    Ericsson Research, Stockholm, Sweden.
    Stankovic, Veljko
    Technische Universit¨at Ilmenau (TUI), Ilmenau, Germany.
    Jorswieck, Eduard A.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Wild, Thorsten
    Alcatel-Lucent, Germany.
    Fuchs, Martin
    Technische Universit¨at Ilmenau (TUI), Ilmenau, Germany.
    Olsson, Magnus
    Ericsson Research, Stockholm, Sweden.
    A MIMO framework for 4G systems: WINNER concept and results2007Inngår i: 2007 IEEE 8th Workshop on Signal Processing Advances in Wireless Communications, IEEE , 2007, s. 798-802Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, the MIMO framework within WINNER for fourth generation radio systems is further developed and assessed for various deployment scenarios. The emphasis is on radio network system aspects of multi-antenna techniques where preferred configurations for three basic deployment scenarios are given. In the wide area scenario which aims to provide ubiquitous coverage for rural, suburban and urban areas, the scheme selection depends on the user density of spatially separated users. It ranges from grid of fixed beams (GoB) (TDMA based) in case of few users to SDMA with a fixed linear precoding codebook, and finally to adaptive beams with SDMA for highly dense system. In the metropolitan area scenario which is targeting system deployments in large urban environments, multi-user (MU) MIMO precoding performs very well for slow moving users. For higher velocities, per antenna rate control (PARC) or adaptive linear dispersion codes (LDCs) are better choices. In the local area scenario which is characterized by isolated sites, the combination of SDMA and spatial multiplexing achieved by MU-MIMO precoding provides high spectral efficiency.

  • 24.
    Sezgin, Aydin
    et al.
    Information Systems Laboratory, Stanford University, USA.
    Jorswieck, Eduard A.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Boche, Holger
    Fraunhofer German-Sino Lab for Mobile Communications, Berlin, Germany.
    Performance Optimization of Open-Loop MIMO Systems With Orthogonal Space?Time Block Codes2007Inngår i: IEEE Signal Processing Letters, ISSN 1070-9908, Vol. 14, nr 1, s. 13-16Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order to obtain full spatial divversity available in a multiple-input multiple-output (MIMO) system, orthogonal space?time block codes (OSTBC) are employed due to their low decoding complexity. However, the drawback of OSTBC is that the code rate decreases with increasing number of transmit antennas. Using a recent result on the properties of Gaussian quadratic forms, we show that an OSTBC for an odd number of transmit antennas is always outperformed in terms of different performance measures, namely, the outage probability, the outage mean-squared error (MSE), and the raw bit-error rate (BER), by an OSTBC for an even number of transmit antennas, which has a strong impact on the design and application of OSTBC.

  • 25.
    Sezgin, Aydin
    et al.
    Information Systems Laboratory, Stanford University, USA.
    Jorswieck, Eduard A.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Henkel, Oliver
    Fraunhofer-Institute for Telecommunications, 10587 Berlin, Germany .
    Pereira, Stephanie
    Information Systems Laboratory, Stanford University, CA 94305 USA.
    Paulraj, Arogyaswami
    Information Systems Laboratory, Stanford University, CA 94305 USA .
    On the relation of OSTBC and code rate one QSTBC: Average rate, BER, and coding gain2008Inngår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 56, nr 10, s. 4879-4891Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recently, the statistical properties of the equivalent channel representation of a multiple-input-multiple output (MIMO) system employing code rate one quasi-orthogonal space-time block codes (QSTBC), which are constructed by using orthogonal space-time block codes (OSTBC) as building elements, was characterized. Based on these characterizations we analyze the average rate (or mean mutual information), the bit-error-rate performance, and the coding gain achieved with QSTBC for any number of receive and n(T) = 2(n), n >= 2 transmit antennas. First, we study constellation rotation using a systematic approach in order to maximize the coding gain and to achieve full diversity QSTBC. Moreover, we present an upper bound on the coding gain. We derive a lower and upper bound on the BER-performance for QSTBC. Furthermore, we analyze the average rate achievable with QSTBC in case of an uninformed transmitter and also the case, in which the transmitter knows the mean channel matrix whereas the receiver has perfect CSI. Along with the analysis, we compare all the results of these performance measures with the results achieved with OSTBC, revealing important connections between OSTBC and QSTBC. For example, the coding gain of a QSTBC is upper bounded by the coding gain of the underlying OSTBC. Also, the BER of a QSTBC for n(T),T transmit and n(R) receive antennas is tightly lower bounded by the BER of a full-diversity providing intersymbol-interference free system. In addition to that, we show that gains in terms of average rate by using a QSTBC (and, thus, with higher n(T)) instead of the underlying OSTBC are only attainable, if the available channel state information at the transmitter (CSIT) is utilized. Finally, we illustrate our theoretical results using numerical simulations.

  • 26.
    Sjöbergh, Olof
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jorswieck, Eduard A.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Larsson, Erik G.
    Linköping University Department of Electrical Engineering (ISY) Division of Communication Systems.
    Greedy user selection for zero-forcing and MMSE multiuser beamforming with channel estimation errors2008Inngår i: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings, 2008, s. 3137-3140Konferansepaper (Fagfellevurdert)
    Abstract [en]

    in a multi-user MIMO downlink where the base station has only estimates of the channels of the users, the sum-rate of multi-user beamforming saturates at high SNR. However, this is not the case for single-user beamforming. We propose a low-complexity user scheduling algorithm that selects the number of active users based on a closed-form approximation of the average sum-rate, and in particular does not add multiple users in the single-user optimality range. In order to develop this algorithm we derive the expected value of the rate of zero-forcing beamforming and MMSE beamforming with estimated channels and modify the greedy user selection accordingly. The gain of the proposed method is shown in numerical simulations.

  • 27.
    Svedman, Patrick
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jorswieck, Eduard A.
    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.
    Reduced Feedback SDMA Based on Subspace Packings2009Inngår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 8, nr 3, s. 1329-1339Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Herein, we treat Space Division Multiple Access (SDMA) based on partial channel state information and limited feedback. We propose a novel framework utilizing subspace packings, where beamforming, feedback, and scheduling are integrated. Advantages of the proposed framework are that the fed back supportable rates are based on the post-scheduling SINR and that the feedback implicitly contains information about the spatial compatibility of the users. The feasibility region of packings of different dimensions is indicated by the allocation outage probability which is derived. Grassmannian subspace packings, DFT-based packings, and non-orthogonal Grassmannian packings are formulated and studied as candidates. Numerical simulations show better performance for the proposed scheme compared to conventional channel quantization at the receiver with zero-forcing transmission in i.i.d. Rayleigh fading. Finally, we propose and evaluate a beam-graph method to further reduce the feedback load, that can be used in the context of tracking quantized beamformers.

  • 28.
    Zhang, Xi
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jorswieck, Eduard A.
    Communications Laboratory, Faculty of Electrical Engineering and Information Technology,Dresden University of Technology (TUD), Germany.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Paulraj, Arogyasvsami
    Information Systems Laboratory, Stanford University, US.
    On the Asymptotic Optimality of Opportunistic Norm-Based User Selection with Hard SINR Constraint2009Inngår i: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180, ISSN 1687-6172Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recently, user selection algorithms in combination with linear precoding have been proposed that achieve the same scaling as the sum capacity of the MIMO broadcast channel. Robust opportunistic beamforming, which only requires partial channel state information for user selection, further reduces feedback requirements. In this work, we study the optimality of the opportunistic norm-based user selection system in conjunction with hard SINR requirements under max-min fair beamforming transmit power minimization. It is shown that opportunistic norm-based user selection is asymptotically optimal, as the number of transmit antennas goes to infinity when only two users are selected in high SNR regime. The asymptotic performance of opportunistic norm-based user selection is also studied when the number of users goes to infinity. When a limited number of transmit antennas and/or median range of users are available, only insignificant performance degradation is observed in simulations with an ideal channel model or based on measurement data.

  • 29.
    Zhang, Xi
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Jorswieck, Eduard A.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Paulraj, Arogyaswami
    Information Systems Laboratory, Stanford University, USA.
    MSE based optimization of multiuser MIMO MAC with partial CSI2006Inngår i: 2006 Fortieth Asilomar Conference on Signals, Systems and Computers, 2006, s. 374-378Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper studies the optimal transmission design for multiple antenna multiple access channels with linear MMSE receiver at the base station and partial channel state information at the mobiles. The performance criterium for optimization is based on a Schur-concave function that works on the average individual MSEs of all users. The optimal beamforming matrix of each user corresponds to the eigenvector matrix of his channel correlation matrix. The remaining power allocation problem can be solved at reduced complexity. It is also direct to extend the results to Schur-convex functions. The results are illustrated by numerical simulations.

  • 30.
    Zhang, Xi
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Jorswieck, Eduard A.
    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.
    Paulraj, Arogyaswami
    Information Systems Laboratory, Stanford University, USA.
    User selection schemes in multiple antenna broadcast channels with guaranteed performance2007Inngår i: 2007 IEEE 8TH WORKSHOP ON SIGNAL PROCESSING ADVANCES IN WIRELESS COMMUNICATIONS, NEW YORK: IEEE , 2007, s. 1-5Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Recently, user selection algorithms in combination with linear precoding have been proposed that achieve the same scaling as the sum capacity of the MIMO BC. In this work, we study the properties of four user selection algorithms in conjunction with beamforming that guarantee certain SINR requirements under transmit power minimization. It is shown that for a large number of transmit antennas, the norm-based user selection performs close to the optimum. The results are illustrated by various numerical simulations.

1 - 30 of 30
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