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QR decomposition (QRD) based relay protocols can achieve both the distributed array gain and the intra-node array gain in multi-relay systems. Because the QRD is not unique if column permutation is utilized, the traditional QRD based relay protocol can be further improved. Row permutation of the forward channel and column permutation of the backward channel are proposed in this paper. Exhaustive and...
In this paper, a distributed power control algorithm is proposed to perform adaptive spatial multiplexing for the relay enhanced orthogonal frequency division multiple access (OFDMA) cellular systems. As the optimal spatial multiplexing problem is non-convex, we utilize the distributed iteration method to achieve its near-optimal solution. By determining the restriction on the transmit power for each...
In the multiuser spatial multiplexing multiple-input multiple-output (MIMO) system, the joint transmitter-receiver (Tx-Rx) design is investigated to minimize the weighted sum power under the post-processing signal-to-interference-and-noise rate (post-SINR) constraints for all subchannels. Firstly, we show that the uplink-downlink duality is equivalent to the Lagrangian duality in the optimization...
In orthogonal frequency division multiplexing (OFDM) systems, conventional channel estimation techniques using comb- type preambles and interpolation between pilot subcarriers give relatively large mean square errors (MSEs) at the edge sub- carriers. Furthermore, the spacing between pilot subcarriers in the frequency domain has to be close enough according to sampling theorem. To solve these problems,...
The time-variation of channels during one OFDM symbol destroys the orthogonality among subcarriers and results in intercarrier interference (ICI), which may detail substantial error performance. Assumed channels vary in linear fashion during one OFDM symbol, we propose an iterative partial-ICI-cancellation (PIC) based detector for OFDM systems with linear modulation over doubly-selective Rayleigh...
In multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems, the conventional channel estimation techniques using comb-type preambles and interpolation between pilot subcarriers give relatively large mean square errors (MSEs) at the edge subcarriers. Furthermore, the spacing between pilot subcarriers in the frequency domain has to be close enough according to...
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