Methods for channel estimation and signal detection of CDMA signals

摘要

A method and apparatus for increasing the capacity and quality of code-division-multiple-access (CDMA) communications in a near-far and frequency-selective fading environment is disclosed. The invention can be utilized in both synchronous and asynchronous CDMA systems. For convenience, only applications of this invention to synchronous CDMA are described herein. Unique to this invention is that using measurements from a receiver and multiple receivers at the base station, propagation channel parameters associated with a plurality of subscribers are determined without the use of training sequences. The channel parameters are used to calculate any individual user's signature waveform and reconstruct its transmitted signal from the received data. This invention can also be implemented at base stations with multiple antennas or/and fractionally spaced measurements to further improve signal quality by incorporating spatial and temporal diversities. When used at the mobile sites, the invention can alleviate the synchronization problem and mitigating frequency-selective fading.