Performance Analysis of NOMA in Training Based Multiuser MIMO Systems

TL;DR

This paper evaluates the performance of a new NOMA scheme in multiuser MIMO systems with practical CSI acquisition, showing its advantages over orthogonal schemes under certain conditions.

Contribution

It introduces a shared pilot-based NOMA scheme for multiuser MIMO, generalizing orthogonal schemes and analyzing achievable rates with practical pilot signaling.

Findings

NOMA with shared pilots outperforms orthogonal schemes when downlink CSI is available.

The proposed scheme reduces to orthogonal schemes with specific power allocation.

Multi-user beamforming is preferable over NOMA with many user groups.

Abstract

This paper considers the use of NOMA in multiuser MIMO systems in practical scenarios where CSI is acquired through pilot signaling. A new NOMA scheme that uses shared pilots is proposed. Achievable rate analysis is carried out for different pilot signaling schemes including both uplink and downlink pilots. The achievable rate performance of the proposed NOMA scheme with shared pilot within each group is compared with the traditional orthogonal access scheme with orthogonal pilots. Our proposed scheme is a generalization of the orthogonal scheme, and can be reduced to the orthogonal scheme when appropriate power allocation parameters are chosen. Numerical results show that when downlink CSI is available at the users, our proposed NOMA scheme outperforms orthogonal schemes. However with more groups of users present in the cell, it is preferable to use multi-user beamforming in stead of NOMA.