Multipath fading statistics of a direct sequence CDMA signal at 2 GHz, in microcellular and indoor environment

This paper describes the results of field tests consisting of received signal variations and multipath returns seen by a mobile receiver using direct sequence (DS) code division multiple access (CDMA) waveforms. The results reveal that the instantaneous received power lost due to fading (sometimes called the fade margin) increases dramatically as the signalling bandwidth decreases. It also shows that for most of the outdoor locations the significant multipath was confined primarily to 1μs of excess delay with average delay of less than 200 ns. A broader band CDMA system, having a bandwidth exceeding 10-MHz could resolve the multipath components and could use a RAKE receiver to further reduce the transmitted power. However, a narrower band CDMA system could not resolve these multipath components and thereby would suffer signal fading which would have to be compensated by 15 dB or more signal amplification. As a result, a narrower band CDMA system would interfere with its other users and reduce its user capacity if no other forms of diversity are used