Distributed space time block coding in asynchronous cooperative relay networks

The design and analysis of various distributed space time block coding schemes for asynchronous cooperative relay networks is considered in this thesis. Rayleigh frequency flat fading channels are assumed to model the links in the networks, and interference suppression techniques together with an orthogonal frequency division multiplexing type transmission approach are employed to mitigate the synchronization errors at the destination node induced by the different delays through the relay nodes. Closed-loop space time block coding is first considered in the context of decode-and-forward (regenerative) networks. In particular, quasi orthogonal and extended orthogonal coding techniques are employed for transmission from four relay nodes and parallel interference cancellation detection is exploited to mitigate synchronization errors. Availability of a direct link between the source and destination nodes is studied, and a new Alamouti space time block coding technique with parallel interference cancellation detection which does not require such a direct link connection and employs two relay nodes is proposed. Outer coding is then added to gain further improvement in end-to-end performance and amplify-and-forward (non regenerative) type networks together with distributed space time coding are considered to reduce relay node complexity. Novel detection schemes are then proposed for decode-and-forward networks with closed-loop extended orthogonal coding which reduce the computational complexity of the parallel interference cancellation. Both sub-optimum and near-optimum detectors are presented for relay nodes with single or dual antennas. End-to-end bit error rate simulations confirm the potential of the approaches and their ability to mitigate synchronization errors. A relay selection approach is also formulated which maximizes spatial diversity gain and attains robustness to timing errors. Finally, a new closed-loop distributed extended orthogonal space time block coding solution for amplify-and-forward type networks which minimizes the number of feedback bits by using a cyclic rotation phase is presented. This approach utilizes an orthogonal frequency division multiplexing type transmission structure with a cyclic prefix to mitigate synchronization errors. End-to-end bit error performance evaluations verify the efficacy of the scheme and its success in overcoming synchronization errors

Closed-loop extended orthogonal space time block coding for four relay nodes under imperfect synchronization

In future collaborative wireless communication systems with high data rate, interference cancellation is likely to be required in cooperative networks at the symbol level to mitigate synchronization errors. In this paper, we therefore examine closed-loop extended orthogonal space time block coding (CL EO-STBC) for four relay nodes and apply parallel interference cancellation (PIC) detection scheme to mitigate the impact of imperfect synchronization. Simulation results illustrate that the closed-loop EO-STBC scheme under imperfect synchronization can achieve good performance with simple linear processing and outperform previous methods. Moreover, a PIC scheme is shown to be very effective in mitigating impact of imperfect synchronization with low structural and computational complexity

Distributed closed-loop quasi-orthogonal space time block coding with four relay nodes: overcoming imperfect synchronization

In this paper, closed-loop quasi-orthogonal space time block coding (QO-STBC) is exploited within a four relay node transmission scheme to achieve full-rate and increase the available diversity gain provided by earlier two relay approaches. The problem of imperfect synchronization between relay nodes is overcome by applying a parallel interference cancellation (PIC) detection scheme at the destination node. Bit error rate simulations confirm the advantages of the proposed methodology for a range of levels of imperfect synchronization and that only a small number of iterations is necessary within the PIC detectio

Distributed quasi-orthogonal space-time coding for two-way wireless relay networks

Abstract—The contribution in this paper is to consider distributed quasi orthogonal space-time block coding (D-QO-STBC) for two-way (TW) wireless relay networks. In particular we exploit a two time slot protocol and both open-loop and closedloop D-QO-STBC with full cooperative diversity. In the openloop approach constellation rotation is exploited to improve performance, whereas two feedback terms are used in the closedloop schemes. Our end-to-end bit error rate simulations show that TW closed-loop D-QO-STBC and rotated open-loop D-QO-STBC are approximately 8 dB and 7.5 dB better than the distributed Alamouti TW approach at 10−4 bit error rate (BER), which confirms the advantage of four relay schemes in relay network

Distributed Closed-Loop Quasi-Orthogonal Space Time Block Coding with four relay Nodes: overcoming Imperfect Synchronization

In this paper, closed-loop quasi-orthogonal space time block coding (QO-STBC) is exploited within a four relay node transmission scheme to achieve full-rate and increase the available diversity gain provided by earlier two relay approaches. The problem of imperfect synchronization between relay nodes is overcome by applying a parallel interference cancellation (PIC) detection scheme at the destination node. Bit error rate simulations confirm the advantages of the proposed methodology for a range of levels of imperfect synchronization and that only a small number of iterations is necessary within the PIC detectio