MmWave Massive MIMO Based Wireless Backhaul for 5G Ultra-Dense Network

TL;DR

This paper explores the use of mmWave massive MIMO technology with a novel hybrid precoding scheme to enable reliable, high-capacity wireless backhaul for 5G ultra-dense networks, addressing key challenges and benefits.

Contribution

It introduces a digitally-controlled phase-shifter network based hybrid precoding scheme that supports multi-user, multi-stream backhaul links, reducing cost and complexity.

Findings

The proposed scheme supports multiple small-cell BSs simultaneously.

It leverages the low-rank property of mmWave channels to reduce transceiver complexity.

The approach enhances link reliability and capacity for 5G backhaul.

Abstract

Ultra-dense network (UDN) has been considered as a promising candidate for future 5G network to meet the explosive data demand. To realize UDN, a reliable, Gigahertz bandwidth, and cost-effective backhaul connecting ultra-dense small-cell base stations (BSs) and macro-cell BS is prerequisite. Millimeter-wave (mmWave) can provide the potential Gbps traffic for wireless backhaul. Moreover, mmWave can be easily integrated with massive MIMO for the improved link reliability. In this article, we discuss the feasibility of mmWave massive MIMO based wireless backhaul for 5G UDN, and the benefits and challenges are also addressed. Especially, we propose a digitally-controlled phase-shifter network (DPSN) based hybrid precoding/combining scheme for mmWave massive MIMO, whereby the low-rank property of mmWave massive MIMO channel matrix is leveraged to reduce the required cost and complexity of transceiver with a negligible performance loss. One key feature of the proposed scheme is that the macro-cell BS can simultaneously support multiple small-cell BSs with multiple streams for each smallcell BS, which is essentially different from conventional hybrid precoding/combining schemes typically limited to single-user MIMO with multiple streams or multi-user MIMO with single stream for each user. Based on the proposed scheme, we further explore the fundamental issues of developing mmWave massive MIMO for wireless backhaul, and the associated challenges, insight, and prospect to enable the mmWave massive MIMO based wireless backhaul for 5G UDN are discussed.