Abstract
An adaptive delay-tolerant distributed space-time coding (DSTC) scheme equipped with a feedback channel is proposed for two-hop cooperative multiple-input multiple-output (MIMO) networks. A maximum likelihood receiver and adjustable code matrices subject to a power constraint with a decode-and-forward cooperation strategy are considered with different DSTC antenna configurations. In the proposed delay-tolerant DSTC schemes, an adjustable code matrix is employed to transform the space-time coded matrices at the relay nodes. Stochastic gradient and least squares algorithms are also developed with reduced computational complexity. The proposed algorithms are then extended to a cooperative MIMO system using amplify-and-forward strategy and opportunistic relaying algorithms in order to develop a delay-tolerant coding scheme combined with optimal relay selection strategies. An upper bound on the pairwise error probability and a rank criterion analysis are derived which indicate the advantage of the proposed algorithms. Simulation results show that the proposed algorithms obtain significant performance gains and address the delay issue in cooperative MIMO systems as compared to existing DSTC schemes.
Highlights
Cooperative multiple-input multiple-output (MIMO) systems can obtain diversity gains by providing copies of transmitted signals with the help of relays to improve the reliability of wireless communications [1,2,3,4,5] and in applications to spectrum sensing [6, 7]
7 Conclusions We have proposed a delay-tolerant adjustable code matrix optimization (DT-ACMO) scheme and algorithms for cooperative MIMO systems with a feedback channel using an maximum likelihood (ML) receiver at the destination node to mitigate the effect of the delay associated with distributed space-time coding (DSTC) from relay nodes
The multiple-antenna system (MAS) and single-antenna system (SAS) configurations have been analyzed by comparing the pairwise error probability of the delayed DSTCs and the rank criterion
Summary
Cooperative multiple-input multiple-output (MIMO) systems can obtain diversity gains by providing copies of transmitted signals with the help of relays to improve the reliability of wireless communications [1,2,3,4,5] and in applications to spectrum sensing [6, 7]. We propose an adaptive delay-tolerant DSTC scheme and algorithms for cooperative MIMO relaying systems equipped with a feedback channel in both MAS and SAS scenarios. We first consider the kth relay node in MAS which employs relays with multiple antennas, and the N × 1 signal vector s[i] will be re-encoded by an N × T DSTC coding scheme, where T refers to the number of time slots. Where GRkDMAS [i] denotes the (δmax + T) × N delayed version of the channel matrix between the kth relay node and the destination node and MRkDMAS [i] is the N × T DSTC scheme. Where gRkDSAS [i] denotes the (δmax + T) × 1 delayed version of the channel vector between the kth relay node and the destination and N RkD[i] stands for the noise matrix whose samples have zero mean and variance σd. We have studied the effect of using a binary symmetric channel (BSC) as the feedback channel in [16] and concluded that imperfect feedback channel with different error probabilities and different numbers of bits in quantization lead to different detection errors in the optimized code matrices at the relays and cause degradation of the BER performance at the destination
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