Analysis of hybrid diversity receivers in Rayleigh fading channels

This thesis analyses the performance of hybrid diversity receivers which are essentially a hybrid of the three classical receivers: Selection Combining (SC), Equal Gain Combining (EGC) and Maximal Ratio Combining (MRC).; The hybrid selection/maximal ratio combining (H-S/MRC) receiver uses channel statistical information (CSI) to select and combine only the strongest of the available diversity branches. The average output SNR of this receiver and the SEP are derived. Lower computational complexity expressions are derived to compensate for an N!-fold increase in complexity ( N is the number of diversity branches) in receivers with unequal branch statistics. Furthermore, an asymptotical SEP expression valid at high SNR is derived which provides further insight into the factors affecting the asymptotic SEP of the H-S/MRC receiver.; The selection combining (SC) and the double selection/equal gain combining (2S/EGC) receivers which do not use CSI are analysed and exact expressions for their SEP are derived. Furthermore, asymptotic SEP expressions are derived which are enlightening about the factors affecting their SEP at high SNR. It is found that while uneven distribution of the branch signal powers affects the error floor of the receivers, uneven distribution of the branch noise powers affects the asymptotic area above the error floor. The hybrid selection/equal gain combining (H-S/EGC) receiver which allows combining of an arbitrary number of selected branches is a generalization of the SC and 2S/EGC receivers. The asymptotic analysis of this receiver provides a closed form expression for the SEP and indicates that in some environments the asymptotic SEP may actually deteriorate with an increase in the number of combined branches. The asymptotic SEP of the H-S/MRC receiver, on the other hand, is proven to always improve by the combining of additional diversity branches.; A reduced complexity hybrid diversity receiver (RHDR) which tackles the problem of maintaining differential phase reference in selective diversity receivers at switch time is described and simulated. The RHDR uses two branches and achieves a SEP which is upper bounded by the SC receiver and lower bounded by the 2S/EGC receiver.