Airborne reception of CDMA communications
Terrestrial CDMA networks are optimized and designed to operate in strictly controlled interference environments through the use of orthogonal coding, adaptive power control, beamforming, and other techniques that involve the sharing of known configuration information between the basestation and cooperative mobile users. Basestations are sited and configured based on terrain limitations, so that their downlinks (forward links) will have minimum interference to mobile users operating in their vicinity. Therefore, each mobile user will "see" at most a few basestation downlinks simultaneously and only cares to decode the one channel intended for him. We desire to operate a CDMA receiver on board an airborne platform where many more basestations than normal will be visible. At high altitudes, this will result in detrimental effects of intercell multiple-access interference, Doppler spreading due to receiver motion, channel nonlinearities, path loss, and near-far power control. This research focuses on the development and evaluation of robust array processing algorithms to simultaneously receive and decode multiple terrestrial CDMA downlinks in the instantaneous field of view. We utilize a 2-stage approach, where blind beamforming is used to initially sort signals based on known signal properties and spatial separation, followed by a second stage of interference cancellation to isolate and recover individual channels. A joint Space-Time Adaptive Processing - Multiuser Detection (STAP-MUD) solution to optimally combine these stages to further enhance performance is developed. ^
Michael D. Zoltowski, Purdue University.
Engineering, Electronics and Electrical