Research On Power Allocation And Interference Elimination Algorithms For Non-orthogonal Multiple Access System

This paper mainly discusses the key technologies for NOMA(Non-Orthogonal Multiple Access) system. Power domain is introduced for NOMA system, to realize multiple access, that is to say, multiple users reuse a band, and allocate different power to reuse users, in order to distinguish users. And the most advantage of NOMA is to improve the spectrum efficiency. This article is divided into four parts to discuss on NOMA system related issues.Firstly, the NOMA system mathematical model is given, and with the two users as example, we describe the NOMA principle in detail. The core of NOMA technology is that power domain was introduced, and how flexible allocation power to users will be the important research content at transmitter of NOMA system, this paper presents two kinds of low complexity power allocation algorithm, which have the better performance and lower complexity.And a user pairing scheme on each sub-band candidate user set is given. For NOMA system based on SIC(Successive Interference Cancellation) algorithm, in order to improve the performance of the system, the user pair must satisfy certain SINR(Signal to Interference and Noise Ratio) differences to ensure the error propagation as small as possible. A user channel-state sorting-pairing algorithm is presented in this paper, then comparing to other classic algorithms, and the simulation results proved to be validity of the new algorithm.Secondly a new user access scheme is given, with the OFDMA system difference, because of the high frequency spectrum efficiency, there is no need to adopt competitive access, so this paper proposes a user access algorithm based on channel state difference, via full consideration to the principle of maximum capacity and the fairness. With the traditional random access and maximum SINR access algorithm, new algorithm is more effective.Finally, this paper studies interference elimination technology on the receiver technology of NOMA system, because interference is actively introduced on transmitter, so the interference elimination technology is very important. This paper mainly investigates successive interference cancellation algorithm(SIC), but only SIC algorithm is poor performance, and considering the advantage of the ZF and MMSE algorithm, we combined linear detection algorithm with SIC algorithm, such as MMSE-SIC and ZF-SIC algorithm, and the sort of MMSE- SIC algorithms presented in this paper. The performance of MMSE-SIC algorithm is the best, with higher complexity. And QR decomposition algorithm is analyzed, whose performance is less than MMSE-SIC, while the complexity is lower. Besides, considering the IRC(Interference Rejection Combining) algorithm and its performance is much better than MRC algorithm, so combining the IRCand SIC achieves significantly performance. Finally paper proposes interference elimination algorithm with the NOMA multicarrier system, called bidirectional SIC algorithm, the simulation results demonstrate the validity of the proposed algorithm.