Characterisation of the Performance of Cooperative Networks in Ricean Fading Channels

We consider cooperative networks where two singleantenna users assist each other in their transmissions by relaying their partner’s messages. Both users achieve space diversity from sharing their partner’s antenna. The target applications of cooperative networks are systems in which multiple antennas cannot be supported due to size limitation and wireless systems operating in very high frequency bands where line of sight (LOS) propagation dominates and little diversity is available from conventional antenna arrays. Most present work concerning cooperative networks has assumed that the propagation channel exhibits Rayleigh fading (e.g., [1], [2], [3], [4], [5]). However, in situations where an LOS component exists the Ricean fading model is more appropriate. Consequently, this paper presents a characterisation of the performance of cooperative networks in Ricean fading channels. It will be shown that in contrast to the situation in Rayleigh fading channels, in Ricean fading channels there is a region where cooperation is not advantageous, even though the inter-user SNRs are reasonably high. This is of interest particularly in high-frequency applications where LOS propagation often predominates. Also, in Ricean channels having low K-factor values, the gain from cooperating is found to be greater than that available in Rayleigh channels.