Exact Performance Analysis of Cooperative Non-Coherent Detection under Symmetric and Asymmetric Fading

Abstract

The increasing demand for high data rate applications and high link reliability have led to the emergence of cooperative diversity, which is generally used in reduced infrastructure based networks, as a promising candidate to increase spectral and power efficiency, network coverage, and reduce outage probability. Similar to multi-antenna transceivers, relay nodes provide diversity by creating multiple replicas of the signal of interest. The basic idea behind cooperative networks is that various terminals/nodes in a relay network attempt to assist each other in moving information around the network, instead of competing for system resources. The result is an improvement of the overall quality of services- such as the statistical measures of bit-error-rate (BER), outage, throughput, and delay- at all the nodes and an associated increase in system spectral efficiency. Different relaying protocols are implemented in the context of cooperative diversity where the amplify-and-forward (AaF) protocol is considered as one of the simple and attractive protocols that achieve diversity without the need for signal decoding. Most of the reported investigations are typically based on the assumption of full or partial knowledge of channel state information (CSI). However, in practical implementation and realization of wireless communication systems, correct and accurate estimation of CSI is a rather challenging and a cumbersome task, especially in cases of fast-fading scenarios. Furthermore, the estimation of the corresponding CSI demands sophisticated hardware which ultimately increase the overall corresponding power consumption and transceiver complexity. Motivated by the above, this thesis investigates a non-coherent detection technique that does not require CSI in cooperative communication over doubly-selective channel. The proposed detection scheme is based on the generalized maximum likelihood (ML) estimation that can be reduced to a recursive expression, allowing for the implementation of Viterbi-type algorithm. In this context, it is recalled that differential phase shift keying (DPSK) modulation is an effective solution to avoid the requirement of CSI while it has been shown capable of providing robustness against phase ambiguities, particularly in fast-fading channels. Based on this, several analyses have been focused on investigating and improving the performance of differentially modulated cooperative systems. Nevertheless, and given that generalized fading phenomena have detrimental effects on wireless communication systems, all reported results in the open literature are limited to the conventional cases of Rayleigh and Nakagami−m fading conditions, which have been shown to exhibit poor modeling performance compared to generalized fading models. In the same context, the present work is also devoted to the error analysis of differentially modulated cooperative systems over multi-path, shadowing, and composite fading channels. To this end, the statistics of the end-to-end signal-to-noise ratio (SNR) are firstly derived and are subsequently utilized in the derivation of novel closed-form expressions for the corresponding average BER of DPSK based AaF systems. All derived expressions are given in terms of known elementary and special functions and are then subsequently used in quantifying the effect of generalized fading on the system performance. Overall, it is shown that the investigations and contributions in the present thesis provide tools, results and useful insights for implementing energy-efficient and low-complexity cooperative networks.

Date of Award	Jun 2016
Original language	American English
Supervisor	Sami Muhaidat (Supervisor)