RAKE reception with maximal-ratio and equal-gain combining for DS-CDMA systems in Nakagami fading

We study coherent binary direct-sequence code division multiple access (DS-CDMA) systems operating over frequency-selective Nakagami fading channels. In particular a performance comparison between maximal-ratio combining (MRC) and equal-gain combining (EGC) RAKE receivers is considered. For interference limited systems, perfect MRC RAKE receivers can accommodate about 5m/(5m-1) more users than EGC RAKE receivers, where m is the Nakagami fading parameter. MRC has a higher rate of improvement than EGC as the number of combined paths increases. However, imperfect or inaccurate channel fading estimation leads to serious degradation in the performance of MRC receivers and in that case EGC becomes superior to MRC.