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Sökning: swepub > Ottersten Björn 1961 > Kungliga Tekniska Högskolan > Jorswieck Eduard A. 1975

  • Resultat 1-7 av 7
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1.
  • Björnson, Emil, 1983-, et al. (författare)
  • Impact of Spatial Correlation and Precoding Design in OSTBC MIMO Systems
  • 2010
  • Ingår i: IEEE Transactions on Wireless Communications. - IEEE. - 1536-1276. ; 9:11, s. 3578-3589
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
2.
  • Jarmyr, Simon, 1982-, et al. (författare)
  • Statistical Precoding With Decision Feedback Equalization Over a Correlated MIMO Channel
  • 2010
  • Ingår i: IEEE Transactions on Signal Processing. - IEEE. - 1053-587X. ; 58:12, s. 6298-6311
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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3.
  • Jorswieck, Eduard A., 1975-, et al. (författare)
  • Feedback reduction in uplink MIMO OFDM systems by chunk optimization
  • 2008
  • Ingår i: EURASIP Journal on Advances in Signal Processing. - 1687-6172.
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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4.
  • Jorswieck, Eduard A., 1975-, et al. (författare)
  • Guaranteed performance region in fading orthogonal space-time coded broadcast channels
  • 2008
  • Ingår i: EURASIP Journal on Wireless Communications and Networking. - 1687-1472.
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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5.
  • Jorswieck, Eduard A., 1975-, et al. (författare)
  • Performance of TDMA and SDMA based Opportunistic Beamforming
  • 2008
  • Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276. ; 7:11, s. 4058-4063
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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6.
  • Svedman, Patrick, et al. (författare)
  • Reduced Feedback SDMA Based on Subspace Packings
  • 2009
  • Ingår i: IEEE Transactions on Wireless Communications. - IEEE. - 1536-1276. ; 8:3, s. 1329-1339
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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7.
  • Zhang, Xi, et al. (författare)
  • On the Asymptotic Optimality of Opportunistic Norm-Based User Selection with Hard SINR Constraint
  • 2009
  • Ingår i: EURASIP Journal on Advances in Signal Processing. - 1687-6172.
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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