Differential Amplify-and-Forward Relaying in Time-Varying Rayleigh Fading Channels

This paper considers the performance of differential amplify-and-forward (D-AF) relaying over time-varying Rayleigh fading channels. Using the auto-regressive time-series model to characterize the time-varying nature of the wireless channels, new weights for the maximum ratio combining (MRC) of the received signals at the destination are proposed. Expression for the pair-wise error probability (PEP) is provided and used to obtain an approximation of the total average bit error probability (BEP). The obtained BEP approximation clearly shows how the system performance depends on the auto-correlation of the direct and the cascaded channels and an irreducible error floor exists at high signal-to-noise ratio (SNR). Simulation results also demonstrate that, for fast-fading channels, the new MRC weights lead to a better performance when compared to the classical combining scheme. Our analysis is verified with simulation results in different fading scenarios

Outage rates and outage durations of opportunistic relaying systems

Opportunistic relaying is a simple yet efficient cooperation scheme that achieves full diversity and preserves the spectral efficiency among the spatially distributed stations. However, the stations' mobility causes temporal correlation of the system's capacity outage events, which gives rise to its important second-order outage statistical parameters, such as the average outage rate (AOR) and the average outage duration (AOD). This letter presents exact analytical expressions for the AOR and the AOD of an opportunistic relaying system, which employs a mobile source and a mobile destination (without a direct path), and an arbitrary number of (fixed-gain amplify-and-forward or decode-and-forward) mobile relays in Rayleigh fading environment