Mobile gNB with Wireless Access Backhauling

Description

Mobile gNB with Wireless Access Backhauling (MWAB) is a network node concept in 5G where a gNodeB (gNB) utilizes a wireless link for its backhaul transport, rather than relying on a traditional fixed-line connection like fiber or microwave point-to-point. The gNB itself is mounted on a mobile platform, such as a vehicle, drone, or portable unit, making the entire access node movable. The primary wireless backhaul link is typically established via a separate 5G radio link, often using a higher frequency band with substantial bandwidth, to a donor gNB or a dedicated backhaul aggregation node that has a fixed connection to the 5G Core Network. This creates a two-hop wireless path: the first hop is the wireless backhaul between the MWAB and the donor site, and the second hop is the access link between the MWAB and the end-user devices (UEs).

Architecturally, the MWAB contains all the standard gNB functions—comprising the Central Unit (CU) and Distributed Unit (DU)—but its transport network layer is designed to manage the specific challenges of a wireless backhaul. This includes robust layer 2 and layer 3 protocols for routing, quality of service (QoS), and synchronization over the wireless medium. Key to its operation is integrated access and backhaul (IAB) technology, standardized in 3GPP, which allows the same spectrum and air interface to be dynamically shared between access and backhaul functions, though MWAB may also use dedicated spectrum. The MWAB must handle mobility management for itself if its platform moves, requiring handover procedures for its own backhaul link to ensure continuous service for its attached UEs.

Its role in the network is to provide extreme deployment flexibility and network densification. It acts as a capacity and coverage booster that can be dynamically positioned based on real-time demand, such as during a sports event, a natural disaster where infrastructure is damaged, or in a developing area without built-out fiber. The MWAB extends the reach of the 5G network by creating a movable cell site that is not constrained by the availability of physical backhaul cables, enabling non-terrestrial networks, rapid military deployments, and cost-effective coverage in rural or temporary scenarios.

Purpose & Motivation

MWAB was developed to overcome the fundamental limitation of fixed backhaul infrastructure, which is expensive, time-consuming to deploy, and inflexible. Traditional cell sites require trenching for fiber or careful alignment for microwave links, making rapid deployment or temporary coverage economically unviable. This posed a significant challenge for providing immediate connectivity in emergency response situations, for pop-up capacity at large events, or for covering remote areas. The motivation for MWAB is deeply tied to the 5G vision of ubiquitous, ultra-reliable, and high-capacity connectivity anywhere, anytime.

The creation of MWAB is driven by the convergence of several technological enablers: the high throughput and low latency of 5G New Radio (NR), which makes wireless backhaul performance competitive with fixed links; advanced beamforming and mmWave spectrum, which provide the necessary directional gain and bandwidth; and the standardization of Integrated Access and Backhaul (IAB) in 3GPP Release 16. MWAB solves the 'last-mile' backhaul problem for mobile nodes, allowing network operators to deploy cells on-demand without pre-existing infrastructure. This is crucial for realizing the full potential of 5G in scenarios like vehicular networks, where a gNB on a bus could provide localized hotspot coverage, or in disaster recovery where the existing network is compromised.