Large-scale MIMO-based wireless backhaul in 5G networks

In order to enhance the attainable transmission rates to the levels specified by future wireless communications, a paradigm shift from conventional small-scale MIMO to large-scale (LS)-MIMO is highly desirable. LS-MIMO technology as a "cleanslate" approach is shown to be capable of dramatically increasing the area spectral efficiency (SE, as measured in bits per second per Hertz per square kilometer) while simultaneously improving the energy efficiency as measured in bits per Joule. Furthermore, the concept of LS-MIMO has established itself as a beneficial transmission/detection paradigm, thus substantially reducing the impact of interference relying on some advanced transmit precoding/ beamforming/detection techniques. This article is intended to offer a state-of-the-art survey on LS-MIMO research, to promote the discussion of its beneficial application areas and the research challenges associated with BF aided wireless backhaul, LS-MIMO channel modeling, signal detection, and so on. Additionally, a joint group power allocation and pre-beamforming scheme called JGPAPBF is proposed to substantially improve the performance of LS-MIMO-based wireless backhaul in heterogeneous networks. Our hope is that this article will stimulate future research efforts.