Equitable MAC Layer Performance Comparison of Cooperative Diversity Protocols for Wireless Networks

Cooperative diversity protocols, in which broadcast nature of the wireless medium is exploited to improve transmission reliability, have recently been proposed as a solution to combat fading effects in wireless networks that are constrained by size and cost. Much of the performance comparison of these protocols has been carried out at the physical layer. In this paper, we argue that due to the inherent difficulty of physical layer modifications, practical cooperative diversity protocols would be implemented at or above the MAC layer. Moreover, in addition to reliability, energy efficiency (in terms of the total number of bits transmitted) of the cooperative diversity protocols must also be considered for equitable performance comparison. To this end, in this paper we analytically compare the performance of well-known cooperative diversity protocols with a Direct Transmission protocol under equitable conditions in terms of a fixed bit transmission budget; the investigated protocols are direct transmission with no cooperation, decode & forward protocol and coded cooperation. Probability of packet error is used as a performance metric which is analyzed over a range of bit-error rates. Our conclusions are at odds with the deductions of prior studies as we show that direct transmission outperforms cooperative diversity protocols under equitable MAC layer performance comparison.