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.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (63 CRs across 6 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the MWAB function introduced specific enhancements to the Location Services (LCS) architecture and procedures to support accurate positioning when a User Equipment is connected via a mobile gNB with wireless backhaul. Key new capabilities include the determination of a UE's location based on the location and velocity of the MWAB itself, the introduction of the NL10 reference point for the LMF to send location requests to the GMLC, and special privacy check exemptions when positioning the MWAB-UE solely to locate a different target UE. The procedures were enhanced so the LMF can use reported cell IDs to identify MWAB cells and compensate for timing offsets between the positioning measurements of the target UE and the moving MWAB.
- Mobile Terminated SMS over NAS: 5GS Access Selection TS 23.501CR0201
- Storing of MPS indicator in non-volatile memory of mobile TS 24.501CR0123
- Resolution of editor's note on maximum length of the 5GS mobile identity IE TS 24.501CR0503
- Completion of mobile identity IE definition in messages TS 24.501CR0574
- Correction on 5GS mobile identity IE name TS 24.501CR0766
In Release 16, the specification introduced new support for Location Services (LCS) when a Mobile gNB with Wireless Access Backhauling (MWAB) is involved, requiring enhancements for accurate UE positioning due to the MWAB's mobility. Key additions include procedures for the LMF to determine a UE's location based on the location and velocity of the MWAB, a new NL10 reference point for the LMF to send location requests to the GMLC in such scenarios, and a specific privacy check exemption for the MWAB-UE when its positioning is performed to locate a different Target UE.
In Release 17, the key enhancement for the Mobile gNB with Wireless Access Backhauling (MWAB) function was the introduction of specific support for Location Services (LCS) when a MWAB is involved. This required new procedures, such as allowing the LMF to use the MWAB's own location, velocity, and measurement timing to accurately estimate a target UE's position, and defining a privacy check exemption for the MWAB-UE when its location is requested solely for locating another target UE. The release also established the NL10 reference point for the LMF to send location requests to the GMLC in these MWAB-involved scenarios.
- Fix of encoding errors in 5GS mobile identity IE TS 24.501CR2597
In Release 18, the MWAB (Mobile gNB with Wireless Access Backhauling) function introduced specific support for location services, including the new 5GC-MT-LR procedure involving a Mobile Base Station Relay. Enhancements defined procedures for the LMF to obtain the location, velocity, and timing data of the moving MWAB itself to accurately estimate a target UE's position, utilizing interfaces like NL10 for LMF to GMLC communication. The release also specified a privacy check exemption for the MWAB-UE when its location is being determined solely to aid in locating another target UE.
- Support of Mobile Base Station Relay for Location Service TS 23.273CR0240
- Update of the Location Services involving Mobile Base Station Relay TS 23.273CR0339
- Introduction of Mobile Base Station Relay TS 23.501CR3813
- Equivalent SNPN usage for mobile identity selection TS 24.501CR4840
- Support of 5GC-MT-LR procedure involving Mobile Base Station Relay TS 29.515CR0120
- Support of location service involving Mobile Base Station Relay TS 29.572CR0177
+ 4 more changes
In Release 19, the specifications introduced comprehensive support for the Mobile gNB with Wireless Access Backhauling (MWAB) function, significantly enhancing location services for UEs served by a moving MWAB. Key new capabilities include dedicated procedures for LCS involving MWABs, where the LMF can now derive a UE's location by factoring in the MWAB's own location, velocity, and measurement timing to improve accuracy. Additionally, the release defined specific privacy check exemptions for MWAB-UEs when their positioning is used to locate another target UE and introduced the new NL10 reference point between the LMF and GMLC to support these MT-LR procedures.
- LCS with MWAB support TS 23.273CR0546
- General Support for MWAB involved positioning TS 23.273CR0547
- MWAB configuration TS 23.501CR5467
- Mobility of UEs served by MWAB TS 23.501CR5469
- MWAB definitions and abbreviations TS 23.501CR5521
- Support for Location Service Support of UEs served by MWAB TS 23.501CR5544
+ 37 more changes
In Release 20, the MWAB function introduced enhanced location services to accurately determine the position of a UE when connected to a moving MWAB. This included new procedures where the LMF uses the MWAB's own location, velocity, and the timing of its positioning measurements to estimate the UE's location, and a specific privacy check exemption for the MWAB-UE when its location is needed for another target UE. Additionally, support for an Ethernet type of BH PDU Session for MWAB was standardized.
- Support of Ethernet type of BH PDU Session for MWAB TS 23.501CR6330
Explore further
Broader topics and technologies where MWAB plays a role.
Defining Specifications
3GPP specifications that define or reference MWAB, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.273 vj50 | 5G Location Services Stage 2 Architecture | Rel-19 |
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |
| TS 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TS 24.501 vj50 | 5G NAS Protocols Specification | Rel-19 |
| TS 29.515 vj50 | Ngmlc Service Based Interface Protocol | Rel-19 |
| TS 29.572 vj50 | Nlmf Service Based Interface Stage 3 | Rel-19 |