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UBC Theses and Dissertations

Analysis and design of BICM-OFDM and buffer-aided relaying Islam, Toufiqul


The growing demand for high data rates, reliability, network densification, and coverage extension will make relaying one of the key enabling technologies in future wireless cellular and broadband access networks. As the underlying channels in broadband wireless communication experience frequency-selective fading, it is necessary to study new relaying schemes to exploit the inherent diversity offered by the frequency-selective channels. We adopt the combination of bit-interleaved coded modulation (BICM) and orthogonal frequency division multiplexing (OFDM) to combat frequency-selective fading. We propose and analyze several new half-duplex (HD) BICM-OFDM relaying schemes for single- and multi-source communication systems. We derive the asymptotic pairwise error probability (PEP) and show that the proposed schemes can successfully extract full space and frequency diversity offered by the channel. The PEP expressions are exploited to develop guidelines for system design such as sub-carrier allocation, relay selection, relay grouping, relay placement, and power allocation. Although conventional HD relaying schemes, where relays receive and transmit according to a pre-fixed schedule, are simple in operation, their performance can be limited because the best links may not be exploited, in particular, when the channel changes from one time slot to the next. To circumvent this problem, we present buffer-aided relaying protocols where the relay decides on its transmission and reception based on the instantaneous qualities of the source-relay and relay-destination channels. For both flat-fading and frequency-selective fading links, we propose link selection protocols for buffer-aided relaying, which can yield a large coding and/or diversity gain advantage over conventional HD relaying for finite and infinite buffer sizes. We assume that the channel state information (CSI) can be outdated when link selection is performed and show that if both the instantaneous signal-to-noise ratio (SNR) and the reliability of the CSI estimates are incorporated into the link selection protocols, a lower error rate can be achieved compared to considering the SNR only. We introduce a decision threshold to the link selection protocols, which can be tuned to ensure buffer stability and trade error rate with delay and/or throughput.

Item Citations and Data


Attribution 2.5 Canada