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IEEE International Conference on Acoustics, Speech and Signal Processing

作者： Song, Bin Haardt, Martin Ilmenau Univ Technol Commun Res Lab D-98694 Ilmenau Germany

ISBN: (纸本)9781424423538

In this paper, we study the achievable throughput for regularized block diagonalization (RBD) precoding in multi-user MIMO broadcast channels at high SNRs. By applying an analytical framework for a high SNR affine approximation to capacity, we derive the multiplexing gains and the power offsets for RBD in two cases separately. In the first case, we assume that the aggregate number of receive antennas is less than or equal to the number of transmit antennas. It is found that RBD can maintain the same multiplexing gain as dirty paper coding (DPC) and block diagonalization (BD) precoding at high SNRs and has a smaller power offset than BD. The sum rate differences relative to DPC and BD are analyzed and bounded as simple functions of the system parameters. In the second case, we assume that the aggregate number of receive antennas is larger than the number of transmit antennas. Although RBD can still be performed, the achievable throughput is degraded with an increasing number of receive antennas. The benefit of spatial multiplexing is completely lost due to a unit spatial multiplexing gain at high SNRs.

关键词： Muli-user MIMO dirty paper coding linear precoding capacity approximation

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Generalized Channel Inversion Methods for Multiuser MIMO Systems

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IEEE TRANSACTIONS ON COMMUNICATIONS 2009年第11期57卷 3489-3499页

作者： Sung, Hakjea Lee, Sang-Rim Lee, Inkyu Korea Univ Sch Elect Eng Seoul South Korea

Block diagonalization (BD) is a well-known pre-coding method in multiuser multi-input multi-output ( MIMO) broadcast channels. This scheme can be considered as a extension of the zero-forcing (ZF) channel inversion to the case where each receiver is equipped with multiple antennas. One of the limitation of the BD is that the sum rate does not grow linearly with the number of users and transmit antennas at low and medium signal-to-noise ratio regime, since the complete suppression of multi-user interference is achieved at the expense of noise enhancement. Also it performs poorly under imperfect channel state information. In this paper, we propose a generalized minimum mean-squared error (MMSE) channel inversion algorithm for users with multiple antennas to overcome the drawbacks of the BD for multiuser MIMO systems. We first introduce a generalized ZF channel inversion algorithm as a new approach of the conventional BD. Applying this idea to the MMSE channel inversion for identifying orthonormal basis vectors of the precoder, and employing the MMSE criterion for finding its combining matrix, the proposed scheme increases the signal-to-interference-plus-noise ratio at each user's receiver. Simulation results confirm that the proposed scheme exhibits a linear growth of the sum rate, as opposed to the BD scheme. For block fading channels with four transmit antennas, the proposed scheme provides a 3dB gain over the conventional BD scheme at 1 % frame error rate. Also, we present a modified precoding method for systems with channel estimation errors and show that the proposed algorithm is robust to channel estimation errors.

关键词： Multi-input multi-output (MIMO) multiuser broadcast channels (BC) linear precoding minimum mean-squared error (MMSE)

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On the MSE-Duality of the Broadcast Channel and the Multiple Access Channel

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2009年第2期57卷 698-713页

作者： Hunger, Raphael Joham, Michael Utschick, Wolfgang Tech Univ Munich Associate Inst Signal Proc D-80290 Munich Germany

We present a mean-square-error (MSE) duality between the broadcast channel and the multiple access channel for multiantenna users communicating with a single base station. We introduce three levels of the duality which allow for a problem specific customization with different computational complexities and resolutions. The first level preserves the sum-MSE during the conversion from the uplink to the downlink and vice versa, whereas the second level not only keeps the sum-MSE constant but also ensures the preservation of the individual users' MSEs. The third level involves the finest resolution and preserves the individual streams' MSEs and the individual streams' signal-to-interference-and-noise ratio (SM) simultaneously. In contrast with hitherto existing MSE-dualities, the proposed sort of duality features a lower complexity since no MSE computation detouring is necessary during the conversion to the dual domain and is capable of handling all combinations of active and passive transmitters and receivers. Moreover, we show how two of these three dualities can be exploited to solve the unweighted total sum-MSE minimization problem and the weighted sum-MSE minimization in the broadcast channel in an efficient way by revealing the hidden convexity in the first case and drastically reducing the computational complexity in the latter case.

关键词： Broadcast channel (BC) decentralized receivers duality joint minimum mean-square error (MMSE) filtering linear precoding projected gradient

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ON THE IMPACT OF SPATIAL CORRELATION AND PRECODER DESIGN ON THE PERFORMANCE OF MIMO SYSTEMS WITH SPACE-TIME CODING

ON THE IMPACT OF SPATIAL CORRELATION AND PRECODER DESIGN ON ...

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IEEE International Conference on Acoustics, Speech and Signal Processing

作者： Bjoernson, Emil Ottersten, Bjoern Jorswieck, Eduard Royal Inst Technol Signal Proc Lab ACCESS Linnaeus Ctr Stockholm Sweden Tech Univ Dresden Commun Lab Chair Commun Theory Dresden Germany

ISBN: (纸本)9781424423538

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 pen-nits 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.

关键词： linear precoding Majorization MIMO Systems Orthogonal Space-Time Block Codes Symbol Error Rate

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Resource Allocation in MIMO-OFDMA Wireless Systems Based on linearly Precoded Orthogonal Space-Time Block Codes

Resource Allocation in MIMO-OFDMA Wireless Systems Based on ...

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15th Open European Summer School and IFIP TC6 6 Workshop, EUNICE 2009

作者： Danobeitia, Borja Femenias, Guillem Riera-Palou, Felip Univ Balearic Isl Mobile Commun Grp Palma De Mallorca 07122 Illes Balears Spain

ISBN: (纸本)9783642036996

This paper proposes and analyzes efficient rate and power allocation algorithms for MIMO-OFDMA broadcast channels based on linearly precoded orthogonal space-time block codes. The weighted sum-rate maximization problem is considered for both continuous and discrete rate allocation schemes. Since this problem is non-convex and combinatorial in nature, the Lagrange dual decomposition method is used to find an accurate near-optimal solution. The effects of using different MIMO configurations and realistic channel models with space and frequency correlation over the weighted sum-rate of the system is considered.

关键词： Resource allocation OFDMA MIMO STBC linear precoding Lagrange dual methods

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Multiple Decision Feedback Equalizers for Vector Systems with Complexity/Performance Tradeoff

Multiple Decision Feedback Equalizers for Vector Systems wit...

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16th International Conference on Telecommunications (ICT)

作者： Cardiff, Barry Gaffney, Brian Fagan, Anthony D. Univ Coll Dublin Sch Elect Elect & Mech Engn Dublin Ireland

ISBN: (纸本)9781424429363

We consider detectors for the class of vector systems describable by the matrix equation y = Ax + n, where y is a vector of observations, n the additive noise vector, A the known system matrix, and x are the unknown (to be estimated) symbols drawn from a finite symbol alphabet. A novel detector is developed consisting of the combination of Multiple Decision Feedback Equalizers (M-DFE) each with a permutation functionality included in such a way as to produce a detector structure that can significantly out-perform the conventional single DFE. Different arrangements are possible allowing a complexity / performance trade-off. The serial cascade where each DFE adapts its permutation based on reliability metrics from the previous DFE out-performs the parallel autonomous arrangement for the same number of DFEs. We also outline complexity reduction techniques for the special cases of Hadamard based precoded OFDM and single carrier OFDM that are more applicable to the parallel arrangement.

关键词： Equalization DFE Multiple DFE (M-DFE) Vector systems OFDM linear precoding MIMO

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Multiple Decision Feedback Equalizers for Vector Systems with Complexity/Performance Tradeoff

Multiple Decision Feedback Equalizers for Vector Systems wit...

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International Conference on Telecommunications (ICT)

作者： Barry Cardiff Brian Gaffney Anthony D. Fagan School of Electrical Electronic & Mechanical Engineering University College Dublin Ireland

We consider detectors for the class of vector systems describable by the matrix equation y = Ax + n, where y is a vector of observations, n the additive noise vector, A the known system matrix, and x are the unknown (to be estimated) symbols drawn from a finite symbol alphabet. A novel detector is developed consisting of the combination of Multiple Decision Feedback Equalizers (M-DFE) each with a permutation functionality included in such a way as to produce a detector structure that can significantly out-perform the conventional single DFE. Different arrangements are possible allowing a complexity/performance trade-off. The serial cascade where each DFE adapts its permutation based on reliability metrics from the previous DFE out-performs the parallel autonomous arrangement for the same number of DFEs. We also outline complexity reduction techniques for the special cases of Hadamard based precoded OFDM and single carrier OFDM that are more applicable to the parallel arrangement.

关键词： Equalization DFE Multiple DFE (M-DFE) Vector systems OFDM linear precoding MIMO

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Quantized principal component selection precoding for spatial multiplexing with limited feedback

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IEEE TRANSACTIONS ON COMMUNICATIONS 2008年第5期56卷 838-846页

作者： Mun, Cheol Chungju Natl Univ Dept Elect Commun Engn Chungju 380702 Chungbuk South Korea

In this paper, for spatial multiplexing with limited feedback, a quantized principal component selection (QPCS) precoding scheme is proposed that achieves comparable capacity to the closed-loop multiple-input multiple-output (MIMO) and furthermore adapts to various fading channel conditions without any additional feedback bits and transmit channel state information (CSI). We propose a systematic design method for a codebook consisting of a finite number of unitary matrices based on a maximizing minimum distance criterion in the one-dimensional angular domain and show that the method outperforms the Grassmannian subspace packing method in various fading channel conditions. The proposed QPCS precoding scheme allows for adjustment of the precoding matrix based on limited feedback information on the principal vectors approximating a MIMO channel in the angular domain according to various channel conditions. Furthermore, for practical implementation of the QPCS precoding scheme, we propose a structured precoder optimization procedure and show that the proposed procedure induces a negligible capacity loss compared with the exhaustive precoder optimization, even with considerably reduced complexity.

关键词： MIMO systems spatial multiplexing linear precoding limited feedback antenna array processing

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Maximum ratio combining precoding for multi-antenna relay systems

Maximum ratio combining precoding for multi-antenna relay sy...

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IEEE International Conference on Communications (ICC 2008)

作者： Bahrami, Hamid Reza Le-Ngoc, Tho McGill Univ Dept ECE Montreal PQ H3A 2A7 Canada

ISBN: (纸本)9781424420742

This paper addresses the problem of design of practical communication strategies for multi-antenna amplify-and-forward and decode-and-forward relay systems. We show that simple linear techniques at source and destination in conjunction with maximum ratio combining can provide an optimal transmission strategy in terms of received SNR without imposing a huge computational load over the relay node(s). Besides the structure of precoding matrices are very similar at source and relay nodes, which reduces the complexity as all nodes can play the role of source and relay nodes without changing their transmission structure. Numerical results show that the proposed transmission and reception techniques can improve the received SNR, and hence enhance the ergodic capacity.

关键词： cooperation relay system linear precoding maximum ratio combining

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Asynchronous interference mitigation in cooperative base station systems

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2008年第1期7卷 155-165页

作者： Zhang, Hongyuan Mehta, Neelesh B. Molisch, Andreas F. Zhang, Jin Dai, Huaiyu Marvell Semicond Inc Santa Clara CA 95054 USA MERL Cambridge MA 02139 USA Lund Univ Dept Electrosci Lund Sweden N Carolina State Univ Dept Elect & Comp Engn Raleigh NC 27695 USA

Cooperative transmission by base stations (BSs) can significantly improve the spectral efficiency of multiuser, multicell, multiple input multiple output (MIMO) systems. We show that contrary to what is often assumed in the literature, the multiuser interference in such systems is fundamentally asynchronous. Intuitively, perfect timing-advance mechanisms can at best only ensure that the desired signal components - but not also the interference components - are perfectly aligned at their intended mobile stations. We develop an accurate mathematical model for the asynchronicity, and show that it leads to a significant performance degradation of existing designs that ignore the asynchronicity of interference. Using three previously proposed linear precoding design methods for BS cooperation, we develop corresponding algorithms that are better at mitigating the impact of the asynchronicity of the interference. Furthermore, we also address timing-advance inaccuracies (jitter), which are inevitable in a practical system. We show that using jitter-statistics-aware precoders can mitigate the impact of these inaccuracies as well. The insights of this paper are critical for the practical implementation of BS cooperation in multiuser MIMO systems, a topic that is typically oversimplified in the literature.

关键词： base station cooperation interference leakage jitter linear precoding mean square error multiuser MIMO spectral efficiency timing-advance

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