Measurements and modeling of CDMA PCS in-building systems with distributed antenna

Abstract

To investigate the application of spread spectrum Code Division Multiple Access (CDMA) technology t o the future Personal Communications Services (PCS), a comprehensive study of CDMA PCS in the 1.8 GHz band in various radio environments has been conducted by Telesis Technologies Laboratory (TTL) in cooperation with Qualcomm Inc. in San Diego. This paper presents measurement and modeling results on CDMA PCS in-building systems. A distributed antenna system with three nodes, each having two time delayed elements, was set up in a Qualcomm two story office building in San Diego. Wideband CDMA signal coverage was predicted by using a ray tracing tool. The prediction shows good signal coverage in both floors of the building using the three nodes mounted in the ceiling space between the first and second floors with each active element transmitting at -5 dBm. The prediction results are confirmed by measurements at numerous discrete points with a standard deviation of 3.3 dB. Measurements using various combinations of number of nodes and delay elements show significant time and path diversity advantages due to the three finger RAKE receiver in indoor radio environments. Trade-offs between diversity gain and self-interference due to uncaptured finger energy in fringe areas are also discussed.