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Abstract
The next generation wireless networks are expected to meet very ambitious data rates and flexible interfaces for different communication system standards. Multiple-input-multiple-output (MIMO) technique has shown to improve the channel capacity dramatically. However, placing multiple antennas within a tiny and slim mobile handset while maintaining the good isolation between antenna elements poses a big challenge. In pursuit of potentials promised by MIMO, an alternative concept, known as "cooperative relaying" has been developed and flourished over the last decade. This thesis presents novel research results on the design and performance evaluation of various relay protocols with and without memory.
In this thesis, a novel soft information forwarding technique based on symbol-wise mutual information, referred to as mutual information based forwarding (MIF) for memoryless relay networks is proposed. An analytical framework to evaluate the error performance of the proposed MIF scheme in both additive white Gaussian noise and Rayleigh fading channels is presented. Furthermore, it is shown that MIF scheme in Rayleigh fading channels can achieve a full diversity order. A distributed space-time coded soft information relaying in Rayleigh fading channels is also considered. It is shown that the proposed distributed MIF Alamouti scheme can achieve a full diversity order, and outperforms various well-known distributed Alamouti schemes.
Performance of the MIF scheme in two way relay channels (TWRC) is then investigated. Two novel MIF protocols, namely, network coded MIF (NC-MIF) protocol and superposition coded MIF (SC-MIF) protocol, are proposed and analyzed. It is observed that NC-MIF and SC-MIF outperform each other in different channel conditions. Based on this observation, an adaptive scheme that dynamically switch between the SC-MIF and NC-MIF protocols based on the varying channel conditions is proposed. Simulation is employed to demonstrate the improved performance of the proposed MIF schemes in TWRC.
Finally, distributed turbo coded (DTC) relay channel is considered. Unlike the traditional DTC schemes, where the source encodes the information by a single recursive systematic convolutional (RSC) encoder, we adopt a turbo code to encode the source information. The relay decodes the information, interleaves, re-encodes and forwards the information to the destination where a distributed turbo code is formed together with the information received directly from source. Several distributed turbo coding schemes, namely, superposition DTC (SDTC), punctured DTC (PDTC), and nested DTC (NDTC), have been proposed. With the same overall system resources such as power and bandwidth, of the existing DTC scheme, the proposed schemes are shown to outperform the existing DTC schemes significantly.