Multi-carrier Communication System Performance Based On WPDM-CDMA

WPDM-CDMA system is the core technology of3G integrated into the waveletpacket division multiplexing，this technology has a wide application prospect and practicalvalue. It is based on the theory of wavelet packet, and has self-orthogonal andmutual-orthogonal of wavelet packet, while retaining the advantages of CDMA, such aslarger capacity, a variety of diversity techniques, lower transmission power, largercoverage, make the WPDM-CDMA system has high spectrum efficiency, highanti-interference ability characteristics. With the rapid development，channel estimation,searching for the optimal wavelet packet basis, multi-user subcarrier allocation in theWPDM-CDMA system is the research hotspot. In this paper, I will in-depth andmeticulous research these three issues. The main contents include the following aspects:Summarized the current statue and future prospects of WPDM-CDMA, introduces thewavelet packet theory. Based on that, build the frame of it. Analysis the method of optimalwavelet packet basis, select the logarithmic energy entropy as cost function. Core idea andof the algorithm is given in this paper. Next make node’s choice from bottom to top basedon entropy size. Simulation data show that the characterize of data signal can be betterdescribe. In addition to achieve with fewer amounts of data express more information inshort time.This paper analyzes the importance of sub-carrier allocation in WPDM-CDMAsystem, and according to the grouping and interval algorithm proposed a joint algorithm.This algorithm uses the function of user bit demand determining user priority, thencalculates transmission power, allocate the small power to high priority user. This canavoid resource waste. Then simulated in Rayleigh fading channel, compare with groupingand interval algorithm. The result shows that joint algorithm has better fairness and biterror rate performance so that WPDM-CDMA system can gain more excellentperformance.Then, according to the requirement of reliable data transmission, discusses thenecessity of channel estimation. In WPDM-CDMA system use LS and MMSE criterionfinish channel estimation. According to result，when finish channel estimation can gainbetter BER performance than no channel estimation. In the last chapter points out theshortcomings,and looks forward to the future development trend of WPDM-CDMA.