Variable Time-Fraction Collaborative Communications

Variable Time-Fraction Collaborative Communications Patrick Tooher, Ph.D. Concordia University 2009 In order to improve the performance of the wireless channel, collaborative communications has recently been proposed. In such a scenario, a source wishing to transmit a signal to a destination can be aided by an otherwise idle transmitter (labeled a relay). Due to the half duplex constraint, the relay node cannot transmit and receive at the same time. It has been shown that having a variable amount of time for which the relay will receive data, can provide further gains in collaborative communications. In this thesis we develop and study methods to implement the use of a variable time-fraction in collaborative communications. We study our proposed method under different channel state information scenarios. We design channel codes that allow for a relay to collaborate with a finite set of time-fractions. Through analysis, we provide design criteria that allow variable timefraction collaborative codes to optimize their error rate performance. Our variable timefraction collaborative codes are shown to approach the outage probability of collaborative channels. Furthermore, through the use of an upper bound on the error rate, we show the robustness of variable time-fraction collaboration over all relay locations when compared to traditional fixed time-fraction collaboration.