Performance Analysis of NOMA System using Fair Power Allocation Policy

This work addresses the problem of fair power allocation policy in non-orthogonal multiple access (NOMA) system. NOMA is the multiple access (MA) scheme where data corresponding to multiple users are superimposed at the base station (BS). Data decoding at each user is done by employing successive interference cancellation (SIC) strategy. The transmission of multiple users’ data over the same carrier enables to get a better bandwidth efficiency and high achievable capacity, which are the fundamental requirements in 5G communications and beyond. Conventionally, power allocation in NOMA is done based on channel conditions of the corresponding users. Users with weak channel conditions are allocated more power as compared to users with good channel conditions. Hence, to address the fairness, we have proposed a fair power allocation scheme. The proposed low complexity iterative algorithm is developed based on the maximization of the rate of the user with worst channel condition. Simulation results shows the significant improvement in minimum achievable rate as compared to conventional orthogonal multiple access (OMA) scheme for different number of users.

I. Introduction

In the era of internet of things (IoT) and mobile internet, both humans and machines demand a very high data rate and connectivity. The attraction towards 5G technology is driven by the aim to achieve one fifth latency, 10-20 times peak data rate, high reliability, massive connectivity and fairness. Further, with massive interest and capacity of academia-industry alliance, hopefully 6G is set to roll out commercially by 2030. The improvement in the next generation wireless communication is measured by its ability to serve multiple users at a time, with minimum data rate requirement. The techniques of multiple access (MA) act as enablers in this. Based on the fact that same time or frequency resource block is utilized by one or more users, the MA schemes can be categorized into Non-orthogonal multiple access (NOMA) [1]– [2] and Orthogonal multiple access(OMA) [3]. Orthogonal frequency-division multiple access (OFDMA) and time division multiple access (TDMA) are examples of OMA schemes. OFDMA was introduced to enable 4G while TDMA was developed during 3G. On the other hand, techniques such as sparse code multiple access (SCMA) [4], multiuser shared access (MUSA) [5], pattern division multiple access (PDMA) [6], low-density spreading (LDS) [7] and bit division multiplexing (BDM) [8] use principle of NOMA for this purpose.