A Research On WCDMA Uplink Signal Separation Technique

Because of good anti-jamming,low interception,confidentiality and other characteristics,spread spectrum communication system is widely used in military,electromagnetic countermeasure and other fields.WCDMA is a spread spectrum communication system that is widely used in mobile communication.This system has been applied in the field of satellite communication after some inprovements.Mobile User Object System(MUOS)is a satellite communication system which works in UHF band.Its uplink uses a Spectrum-Adaptive wideband code division multiple access(SA-WCDMA)technology,which can support a transmission rate up to 384 Kbps.However,most of the existing research on WCDMA is in the field of mobile communication.At the same time,for MUOS system research,current works focus on the link simulation and anti-jamming performance,while the research on non-cooperative communication is less.Therefore,this paper focuses on the uplink signal separation technology in non-collaborative communication in WCDMA system.This paper mainly focuses on the following aspects:(1)According to the standard of uplink signal in WCDMA system,this paper completes the simulation of the system.The simulation results show that,when using single antenna to receive,the bit error rate is10^-5 when_bE/N₀(28)4d B;and the diversity gain around 3d B can be obtained with multiple antenna reception compared with the SISO system.(2)To solve the problem of simultaneous multi-user communication,this paper studies the performance of traditional multi-user detector in the specific environment of the system.The simulation results show that the performance of each user is the same as the single user's simulation when power control exists,but without power control,the performance of traditional multi-user detector is poor for the weak power signal,especially when power difference is large.In actual scenarios,power control can't be ensured in non-cooperative communication.(3)Aiming at the problems of traditional multi-user detector,this paper adopts blind source separation method to separate the signals received by multiple antennas.Firstly,in order to meet the requirements of signal separation,the received signal is preprocessed,including the estimation of the number of sources and whitening noise reduction;Then,the simulation results of JADE algorithm and Fast ICA algorithm in the system are studied when the number of source signals does not exceed the number of receiving antennas.The simulation results show that the performance of signal separation is close to that of traditional MMSE detector in some scenarios;Finally,for the case that the number of source signals exceeds the number of receiving antennas,a modified scheme based on the traditional separation method is proposed.At the same time,another channel parameter estimation method based on the second generate function is studied.The simulation results show that the separation of mixed WCDMA signals can be realized on the premise that the number of sources is not more than twice of the received signals.