Hybrid automatic-repeat-reQuest systems for cooperative wireless communications

Abstract

As a benefit of achieving a diversity gain and/or a multiplexing gain, MIMO techniques are capable of significantly increasing the achievable throughput and/or the network coverage without additional bandwidth or transmit power. For the sake of striking an attractive trade-off between the attainable diversity gain and/or multiplexing gain, in this thesis the novel Space-Time-Frequency Shift Keying (STFSK) concept is proposed for the family of MIMO systems. More specifically, in order to generate space-time-frequency domain codewords, the STFSK encoding schemes activate one out of Q dispersion matrices, and the associated address bits are then combined with a classic time-domain and frequency-domain modulation scheme. The resultant arrangements impose no inter-symbol interference and are capable of eliminating the inter-antenna interference, hence offering a range of benefits over other classic MIMO arrangements. Additionally, a soft-output STFSK demodulator is designed for iterative detection and the complexity of both the hard- as well as soft-decision demodulators is quantified. Furthermore, the STFSK performance is studied in both the single-user and the multipleuser multi-cell environment in order to investigate the effects of these techniques on the performance of the holistically optimized systems.

Furthermore, we studied the H-ARQ systems advocated in the context of cooperation-aided wireless networks, where the MIMO elements are constituted by the individual elements of separate network nodes. Both perfect and imperfect coherent detection as well as non-coherent detection aided cooperative H-ARQ schemes are considered. In the perfect coherent detection based pilot symbol assisted scheme, a novel relay-switching aided H-ARQ scheme is proposed for mitigating the effects of correlation in fading wireless channels, followed by a H-ARQ scheme employing systematic Luby transform codes. In contrast to the unrealistic perfect coherent detection, realistic imperfect coherent schemes are studied, where the channel impulse responses are imperfectly estimated. Furthermore, non-coherent differential detection aided cooperative H-ARQ schemes are proposed and compared to their coherent detection assisted counterparts. Finally, a novel cooperative H-ARQ arrangement based on distributed space-time codes is proposed for the sake of improving the attainable system throughput, while reducing the system’s complexity.

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Identifiers

ORCID for Lajos Hanzo: orcid.org/0000-0002-2636-5214

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