5G Wireless Backhaul

: [Princeton University]

- Overview

5G wireless backhaul, or wireless transport as some call it, is a method of wirelessly connecting broadband sites to the core network. For mobile networks, this is a common method of connecting radio access network (RAN) tail sites (such as base stations, eNodeB/eNB or gNodeB/gNB) to the core of the mobile network – without deploying fiber optics. It is used when a high-speed wired connection (usually via fiber optics) to a telecommunications site is not available, rapid deployment is required, and a cost-effective solution is desired.

In fact, according to the 5G Microwave Report, by 2025, approximately 38 percent of telecom sites worldwide will be connected to the rest of the network via wireless backhaul.

The convergence of fronthaul and backhaul is coming, and it will shape a large part of the 5G networks we will see tomorrow. On the cost side, there is a need to use as little fiber as possible (e.g. DWDM and/or fiber-like wireless), and to move from dedicated switching hardware to virtualized switches running on COTS (commercial off-the-shelf or commercial off-the-shelf) servers. As such, Network Functions Virtualization (NFV) is a key technology for backhaul.

- Future Mobile Network More On Machine-Centric

It is clear that the future mobile network (i.e., 5G) will no longer human centric, it will be more on machine centric which will interconnect billions of smart devices to the mobile network. Recent research and standardization work have been addressing requirements and challenges from radio perspective (e.g., new spectrum allocation, network densification, massive multiple-input-multiple-output antenna, carrier aggregation, inter-cell interference mitigation techniques, and coordinated multi-point processing). In addition, a new network bottleneck has emerged: the backhaul network which will allow to interconnect and support billions of devices from the core network.

Up to 4G cellular networks, the major challenges to meet the backhaul requirements were capacity, availability, deployment cost, and long-distance reach. However, as 5G network capabilities and services added to 4G cellular networks, the backhaul network would face two additional challenges that include ultralow latency (i.e., 1 ms) requirements and ultradense nature of the network.

Due to the dense small cell deployment and heavy traffic cells in 5G, 5G backhaul network will need to support hundreds of gigabits of traffic from the core network and today’s cellular backhaul networks are infeasible to meet these requirements in terms of capacity, availability, latency, energy, and cost efficiency.

- 5G Backhaul Upgrades

To bring the 5G network in reality, a simple upgrade of mobile network will not be enough where we just add new spectrum and enhance the capacity or use advanced radio technology. It will need to upgrade from the system and architecture levels down to the physical layer. Although some research and standardization work addressing the corresponding challenges from radio perspective (e.g., new spectrum exploration, carrier aggregation, network densification, massive multiple-input-multiple-output, and inter-cell interference mitigation techniques) but there is a new challenge has emerged: the backhaul.

5G is going to need a lot of backhaul upgrades. Globally, the average backhaul is less than 5 Mbps. Much of the existing backhaul network in America is a really low capacity network. And when 5G starts to become pervasive, and it’s delivering speeds over 1 Gbps. We need a new backhaul network.

When mobile carriers are building their 5G networks they have to select vendors in three key areas: They have to pick a radio vendor; they need a backhaul vendor to rebuild their network because the current network can’t handle the 5G speeds; and they need a 5G core vendor.