Wireless Backhaul in 5G and Beyond: Issues, Challenges and Opportunities

With the introduction of new technologies such as Unmanned Aerial Vehicle (UAV), High Altitude Platform Station (HAPS), Millimeter Wave (mmWave) frequencies, Massive Multiple-Input Multiple-Output (mMIMO), and beamforming, wireless backhaul is expected to be an integral part of the 5G networks. While this concept is nothing new, it was shortcoming in terms of performance compared to the fiber backhauling. However, with these new technologies, fiber is no longer the foremost technology for backhauling. With the projected densification of networks, wireless backhaul has become mandatory to use. There are still challenges to be tackled if wireless backhaul is to be used efficiently. Resource allocation, deployment, scheduling, power management and energy efficiency are some of these problems. Wireless backhaul also acts as an enabler for new technologies and improves some of the existing ones significantly. To name a few, rural connectivity, satellite communication, and mobile edge computing are some concepts for which wireless backhauling acts as an enabler. Small cell usage with wireless backhaul presents different security challenges. Governing bodies of cellular networks have standardization efforts going on especially for the Integrated Access & Backhaul (IAB) concept, and this is briefly mentioned. Finally, wireless backhaul is also projected to be an important part of the beyond 5G networks, and newly developed concepts such as cell-free networking, ultramassive MIMO, and extremely dense network show this trend as well. In this survey, we present the aforementioned issues, challenges, opportunities, and applications of wireless backhaul in 5G, while briefly mentioning concepts related to wireless backhaul beyond 5G alongside with security and standardization issues.

Automated summary

Wireless backhaul is expected to play an important role in 5G networks with the introduction of new technologies such as UAV, HAPS, mmWave frequencies, mMIMO, and beamforming. It overcomes the performance limitations compared to fiber backhauling and becomes mandatory for the densification of networks. However, challenges in resource allocation, deployment, scheduling, power management, and energy efficiency still need to be tackled. Wireless backhaul enables new technologies like rural connectivity, satellite communication, and mobile edge computing. Security challenges arise with small cell usage and standardization efforts are being made for the IAB concept. Wireless backhaul is projected to be important in beyond 5G networks, as seen with concepts like cell-free networking, ultramassive MIMO, and extremely dense network.