Cooperative Diversity Performance in Millimeter Wave Radio Systems

The constantly increasing demand for capacity in modern communication systems such as wireless backhaul has led to the employment of frequencies above 10 GHz where the dominant fading mechanism is rain attenuation which is usually modelled as a lognormal random variable (when expressed in dB - log-lognormal in linear scale). In addition, in the context of green communications the use of cooperative diversity techniques can be considered as an important tool which improves the performance, reliability and efficiency of such systems. In this paper, the outage performance analysis of a cooperative system operating at frequencies above 10 GHz is presented, where the propagation medium consists of spatially correlated fading channels. In addition, the energy and spectral efficiency of various multiple-access protocols as well as different relay retransmission and receiver combining techniques are investigated. Moreover, it is proposed that the high correlation coefficient between various rain fading channels can be exploited by the relay to estimate the rain fading of the next hop. Extended numerical results present the impact of various system parameters on the end-to-end performance. Finally, comparison with an energy- and bandwidth- equivalent direct link highlights the system parameter regions where cooperative diversity offers gains over non-cooperation.