Research On Multiuser Multistage SIC/RAKE Receiver Algrithm

With the large-scale commercialization of 4G mobile communication system,people's research on 5G technology is in full swing.5G will face the explosive growth of the Internet of things applications,in the face of massive nodes with massive machine communication and ultra-high reliability low-delay connection of two types of scenarios,the existing orthogonal multiple access technology can not meet the needs of more than 5G,Non-orthogonal multiple access technology in the system capacity of the superior performance,making the combination of code domain and power domain non-orthogonal multiple access technology has become a popular candidate in the 5G technology.Based on the idea of spread spectrum communication,the use of advanced interference cancellation technology to deal with the orthogonality of address code to reduce the multiple access interference is one of the important class of non-orthogonal multiple access scheme.Direct Sequence CDMA(DS-CDMA)technology is the most important and popular technology in CDMA.DS-CDMA transmitter is used to allocate unique codewords for each user to support multi-user sharing of the same time and frequency resources and transmit user data.However,Multipath transport channel to bring inter-symbol interference,the number of address codes,non-orthogonal address code under the more serious multiple access interference and other issues need to be resolved.Based on the RAKE receiving algorithm,this paper uses the modular programming idea to establish the DS-CDMA system simulation platform.Then,the performance of several m-sequences and Walsh codes are analyzed theoretically.An improved algorithm of m-sequence is proposed,and its performance is simulated and analyzed.The tolerability of the characteristics of the degree of tolerance,access to more suitable for non-orthogonal multiple access technology,the length of the sequence and the number of performance improvement.Finally,the SIC algorithm of nonlinear multiuser detection is studied.Based on SIC and RAKE technology,the SIC/RAKE receiver simulation model is designed.By setting the number of users,the number of paths and the Rayleigh fading channel,the results show that although the introduction of SIC algorithm increases the complexity of the system,and the performance improvement of SIC/RAKE receiver for non-orthogonal codes is obvious,which can reduce the multi-access interference and anti-multipath Interference effect.