RAKE receiver finger assignment in CDMA terminals with fractionally spaced multipaths

CDMA mobile handsets use a RAKE receiver for pilot assisted demodulation. The RAKE receiver has multiple demodulators, called fingers, which can be used to demodulate distinct multipath components in parallel making it possible to implement diversity reception in the handsets. Typical analyses of the performance of CDMA handsets assume these multipath components to be separated from each other by at least a chip duration which lends a white noise like appearance to multipath interference. In this paper, we present a model to study the performance of a RAKE receiver whose fingers can be assigned to fractionally spaced (i.e., separated by less than a chip duration) multipath components. Based on simulation results, we propose a finger assignment strategy to obtain the best performance under a complexity constraint limiting the number of RAKE receiver fingers available for demodulation.