Dual-hop Vs multihop AF relaying systems

Closed-form expression for the outage probability of dual-hop amplify-and-forward (AF) systems with relay selection from N independent and non-identically (i.ni.d.) distributed dual-hop branches is obtained. Closed-form expression for the probability density function of the end-to-end signal-to-noise ratio (SNR) is also obtained for such systems, and is used to obtain the exact average symbol error probability for systems operating over i.ni.d. Nakagami-m fading links. It is found that the limiting slopes of the outage probability and the average symbol error probability curves are proportional to the sum of the minimums of the fading parameters of the source-to-relay and relay-to-destination links of each branch. The modified generalized transformed characteristic function (M-GTCF) is used to obtain exact, integral solutions for the outage probability and the average symbol error probability of multihop AF relaying systems operating over N i.ni.d. Nakagami-m fading links. It is found that the limiting slopes of the performance metrics curves are proportional to the minimum of the fading parameters of the individual links. Dual-hop AF systems with relay selection from N available relays are compared to multihop AF systems with N intermediate relays. It is found that dual-hop AF systems can significantly outperform multihop AF systems. The findings are used to propose multiple criteria for practical design of wireless cooperative systems.