Research On GRAKE Receiver Technology In HSUPA Of WCDMA System

HSUPA is a new kind of radio access technology in 3GPP Release 6, for the purpose of improving the uplink bit rate and system capacity in WCDMA. In order to reach the uplink peak bit rate in physical layer, extremely low spreading factor is applied in HSUPA. Multi-path interference can not be suppressed effectively because of low spreading gain and weak partial autocorrelation of scrambling code. Thus, the performance of traditional RAKE receiver can not meet the requirement of 3GPP. For the condition of low spreading gain applying in HSUPA' uplink technology, a new type of GRAKE receiver is introduced based on traditional RAKE receiver of WCDMA R99.It can whiten colored noise effectively, and eliminate the interference brought by both multi-path and multi-user.The basic principles and algorithms for the uplink GRAKE receiver in WCDMA R6 are discussed in this paper. Based on the multi-path transmission characteristics of radio channel, the system model of uplink GRAKE receiver is given, and the combining of coefficient is discussed in detail. This paper also illustrates how the GRAKE technology restrains interference. Then, the demodulation algorithm for the uplink GRAKE receiver has been analyzed. The whole designed blueprint of GRAKE receiver is given, and three technologies multi-path detection,noise-finger selection and channel estimation are discussed in detail. The implementation of multi-path detection and noise-finger selection algorithm has been studied well, and the formulas for the channel estimation and channel compensation in WCDMA uplink are derived. In the end, the simulation chain on MATLAB 6.5 platform and simulation steps are enumerated.The performance of demodulation algorithm in GRAKE receiver is simulated and compared, and some reasonable conclusions are listed.