Wireless Network Coding in Network MIMO: A New Design for 5G and Beyond

TL;DR

This paper introduces a novel physical layer network coding design for uplink network MIMO in 5G, reducing backhaul load and computational complexity while ensuring reliable message recovery.

Contribution

It proposes a new design guideline for PNC in uplink N-MIMO systems tailored for 5G, including algorithms for optimal PNC mapping and complexity reduction.

Findings

Achieves low outage probability with reduced backhaul load

Guarantees unambiguous message recovery at destinations

Reduces real-time computational complexity significantly

Abstract

Physical layer network coding (PNC) has been studied to serve wireless network MIMO systems with much lower backhaul load than approaches such as Cloud Radio Access Network (Cloud-RAN) and coordinated multipoint (CoMP). In this paper, we present a design guideline of engineering applicable PNC to fulfil the request of high user densities in 5G wireless RAN infrastructure. Unlike compute-and-forward and PNC design criteria for two-way relay channels, the proposed guideline is designed for uplink of network MIMO (N-MIMO) systems. We show that the proposed design criteria guarantee that 1) the whole system operates over binary system; 2) the PNC functions utilised at each access point overcome all singular fade states; 3) the destination can unambiguously recover all source messages while the overall backhaul load remains at the lowest level. We then develop a two-stage search algorithm to identify the optimum PNC mapping functions which greatly reduces the real-time computational complexity. The impact of estimated channel information and reduced number of singular fade states in different QAM modulation schemes is studied in this paper. In addition, a sub-optimal search method based on lookup table mechanism to achieve further reduced computational complexity with limited performance loss is presented. Numerical results show that the proposed schemes achieve low outage probability with reduced backhaul load.