Backhauling for Small‐Cell Networks

Abstract

Densely deploying small cells is an attractive solution to the explosion of network traffic. However, it is well known that backhaul is a major challenge limiting the improvement of network performance. In this article, we first introduce the characteristics of different wired or wireless backhaul technologies, including fiber, xDSL, sub‐6 GHz, microwave, and millimeter wave (mmWave). As the main performance factors, throughput, latency, energy efficiency, and cost models are analyzed to provide useful guidance for the selection and deployment of backhaul links. Next, we survey existing works on joint optimization of access and backhaul links. Base station (BS) association schemes and caching techniques are also studied for their importance to further improve backhaul performance. Finally, research challenges on backhauling for small‐cell networks are summarized to inspire future research directions.