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Publications (5)3.12 Total impact

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    ABSTRACT: Space-division multiple-access (SDMA) is a communication technique that enables a base station to communicate with several mobile users simultaneously. The ability of the base station to spatially separate several users depends on the pairwise cross correlations between the channel matrices of the users (the inter-user correlation). In this paper, we propose an improved steering downlink multiple-input-multiple-output-orthogonal frequency-division multiplexing (OFDM) system that reduces both the inter-user correlation and the near-far problem resulting in a significant enhancement in system performance. In this system, several base station multiantenna arrays are distributed in a given area. Each array communicates with the base station via optical fiber links, and all transmitter signal processing is performed at the base station. Multiantenna users are spatially separated such that only a subset of the users is served by each tone of the OFDM symbol. The served users are selected based on an algorithm that reduces the inter-user correlations. Distributing the arrays around the users also balances the channel matrix leading to significant reduction in the effect of the near-far problem. The channel matrix of each user is assumed correlated and Ricean distributed. Several data symbols can be spatially multiplexed to each user over each OFDM tone with high reliability and with good total system capacity.
    IEEE Journal on Selected Areas in Communications 01/2006; 24:419-426. · 3.12 Impact Factor
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    ABSTRACT: The near-far problem and the correlations in a MIMO channel are two major obstacles in the way of widely implementing space division multiple access (SDMA) systems. In this paper we investigate the effect of distributing the basestation antennas and the reduction of intra-user correlations on the performance of a MIMO-OFDM system in which a basestation, composed of distributed antenna arrays, is communicating (downlink transmission) with several single antenna mobile users. The arrays are located at different sites in a Ricean-Lognormal channel environment. Very significant improvement in system performance is achieved due to the improved spatial properties of the MIMO channel and due to the reduction of channel matrix correlations
    Proceedings of the Canadian Conference on Electrical and Computer Engineering, CCECE 2006, May 7-10, 2006, Ottawa Congress Centre, Ottawa, Canada; 01/2006
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    ABSTRACT: Mobile users scattered in a microcell and communicating with co-located base station antennas, may cause a severe near-far problem for an uplink space division multiple access (SDMA) system. Also correlations within the multi-input multi-output (MIMO) channel matrix, in such uplink SDMA propagation scenario, can cause significant degradation in system performance. In this paper, we investigate the above problems. We propose to distribute the base station antennas, as multi- antenna arrays, at different sites in the microcell and deploy a correlation reduction algorithm. A significant improvement in the performance of the SDMA system is evident.
    Proceedings of the 64th IEEE Vehicular Technology Conference, VTC Fall 2006, 25-28 September 2006, Montréal, Québec, Canada; 01/2006
  • The IASTED International Conference on Communication Systems and Applications, Banff, Alberta, Canada, July 19-21, 2005; 01/2005
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    ABSTRACT: In this paper we investigate the performance of two-way relaying that uses Alamouti space-time block code (STBC) and network coding. In this scheme, two nodes use Alamouti STBC to transmit their symbols to the relay consecutively in two phases. The relay detects and demodulates the transmitted symbols from the nodes, and then uses the bitwise-XOR operation to combine the detected bits. Then the relay modulates and broadcasts the XORed bits to the nodes using Alamouti STBC. In this paper, the bit error rate of the proposed scheme is derived for an uncorrelated Rayleigh fading channel with perfect channel estimation at receivers.