Combined space time adaptive processing and multiuser detection for enhanced reverse link IS-95 CDMA reception with experimental results

We present novel approaches to reverse link signal reception in IS-95 CDMA systems that utilize space time adaptive processing (STAP), multi-user detection (MUD), and combined STAP/MUD techniques to implement receivers that are resistant to the near-far problem. We also present experimental results that were obtained by applying STAP, MUD, and combined STAP/MUD techniques to actual over-the-air collected signals. The focus of the experiment is on applications where power control is not available to the receiver, which results in a severe interference environment due to the near-far problem. In applying STAP techniques to the IS-95 reverse link, we consider the use of blind adaptive techniques to compensate for the lack of pilot reference symbols. For multiuser detection we focus on the technique known as successive interference cancellation (SIC), where signals are detected one at a time, in order of signal strength, and at each stage, higher level interfering signals are estimated, reconstructed, and subtracted out. We also explore the use of adaptive MMSE channel estimation techniques in conjunction with SIC detection, where the adaptive reconstruction filter recreates both the temporal structure of the channel as well as the frequency-spread characteristics of the signal components