Abstract
The rotated quasi-orthogonal space-time block code (RQSTBC) for asynchronous cooperative diversity is proposed in this paper. The source selects half of the symbols from a signal constellation set and the other half of them from that constellation rotated with the optimum angle. Meanwhile, it constructs orthogonal frequency division multiplexing (OFDM) frames to counterbalance time delays of the signals. Then, relays create the frequency domain quasi-orthogonal space-time block transmitted signals matrix in such a way that its items are staggered to take on the Jafarkhani code structure or time-reversion of it. These three stages let the received signals at the destination take on RQSTBC structure with diversity order 4, which results in the fast symbol-pair-wise maximum likelihood (ML) decoder. Simulation results have shown that the proposed scheme outperforms the other asynchronous cooperative diversity schemes considered in this paper.
Highlights
Though multiple transmit antennas and receiver antennas at nodes would lead to substantial gains in channel capacity and robust abilities to combat with different kinds of interference over a scatteringrich wireless environment, constrained by the space complexities, it is impractical for nodes in ad hoc networks or distributed large scale wireless networks [1]
The efficiency of the cooperative diversity for wireless ad hoc networks [1,2] would be evaluated by three aspects: (i) whether it achieves full diversity; (ii) whether it transmits symbols with maximum rate; and (iii) whether the receiver could exploit the decoder with both good performance and a lower complexity [1,3]
In this paper, based on the ideas in [3,7,8], we present a rotated quasi-orthogonal space-time block code (RQSTBC) asynchronous cooperative scheme, diversity order of which is 4
Summary
Though multiple transmit antennas and receiver antennas at nodes would lead to substantial gains in channel capacity and robust abilities to combat with different kinds of interference over a scatteringrich wireless environment, constrained by the space complexities, it is impractical for nodes in ad hoc networks or distributed large scale wireless networks [1]. In contrast to the original one in [7], our novel contribution constructs the frequency domain transmitted signals of the relay nodes in terms of combining the quasi-orthogonal criterion originally proposed in [8] with time-reversion in [7] The application of this idea lets the received signals at the destination turn on Jafarkhani code [8]. The source picks half of the symbols from a signal constellation set and the other half of them from that constellation which is rotated with the optimum angle and and creates OFDM frames to make up for time delays of the signals In this way, the received signals at the destination take on RQSTBC with the Jafarkhani code structure.
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