Adaptive Receiver For Multirate CDMA Systems On Frequency-selective Fading Channel

Multiuse detection method is a key problem in CDMA systems. There, the main difficulties are multiple access interference (MAI) "near-far" resistance. Rake receiver is an effective method for MAI. Rake receiver can increase capacity of receiver over frequency-selective fading channel; however, traditional Rake receiver is sensitive to "near-far" resistance.Moreover, since in the wireless communications, channel is generally time-variation. The adaptation should be sufficiently fast to track the variation of channel.If the rate change is allowed, the application of the adaptive receiver to the multirate CDMA system is somewhat cumbersome. The main difficulty to use the adaptive receiver is that the adaptation should resume after the rate change. As a result, the performance will be degraded due to the transient.In order to overcome these difficulties, investigating of the mechanism of frequency-selective fading channel is in detail. Combining LMS criterion on subspace and Kalman filter algorithm, multiple parallel adaptive filters and decorrelation Rake receiver, expound a multirate CDMA receiver of multiple parallel structure. In the proposed receiver, the main structural is Rake receiver; there is an adaptive filter of multiple parallel structural in each channel. Then, the adaptation of the weight vector for each rate is possible during the period of different rates. And deduce corresponding adaptive algorithms.The dissertation is divided into six chapters:Chapter 1 is preface, which summarizes the development, theorem, feature, key technology and academic trends.In the chapter 2, we introduce the LMS and Kalman adaptation algorithm. With them, adaptive filters can achieve filtering, Smoothing etc, and can come after and adapt to dynamic transformation of environment.