Transmit beamformer based performance analysis and diversity gains of cell edge user in cooperative MISO-NOMA system

Abstract

This paper investigates the cell-edge user’s performance in a two-user multiple-input single-output non-orthogonal multiple access (MISO-NOMA) systems using downlink beamformers for optimal power allocation. In particular, power allocation coefficients (PACs) are adjusted through beamformers so that the cell-edge user’s performance is improved in a two-user network scenario. In the proposed model, a cell-center user with strong channel conditions plays a role as an energy harvesting (EH) relay by using simultaneous wireless information and power transfer (SWIPT) protocol to assist the cell-edge user having weak channel conditions. Initially, we formulate the expressions for signal-to-interference-plus-noise ratio (SINR) at the cell-center user and signal-to-noise ratio (SNR) and SINR at the cell-edge user in terms of an indefinite quadratic form (IQF) whilst considering distinct correlation matrices for each link. Next, we achieve exact and approximate closed-form expressions for outage probability of linearly dependent and of distinct beamformers, respectively by using IQF approach. The proposed model achieves diversity gain whereas the analytical expressions are validated by simulation means.