A glimpse into crosshaul engineering

Mobile backhaul refers to the section of the telecom network that transports cellular traffic from base stations at cell towers to the nearest traffic switching center. While multiple backhaul options are available, with the arrival of 5G, mobile operators are gravitating towards optical fiber. 5G imposes additional demands in terms of connection bandwidth. This has been met through a ‘crosshaul’ architecture that integrates fronthaul and backhaul.

The integrated and unified management of the transport network resources follows the Software Defined Networking (SDN) principles. The architecture is defined by the Open Networking Foundation (ONF) and adopts Network Function Virtualization (NFV). They are also aligned with the ETSI Management and Orchestration (MANO) architecture as a means to offer a subset of the services of network, cloud and storage.

The intention is to leverage state-of-the-art SDN/NFV architectures and enhance them so as to maximize the compatibility and integration of the system design with the existing standard frameworks. The controller plane, namely the 5G-Crosshaul Control Infrastructure (XCI), is composed of a hierarchy of network and cloud controllers, together with orchestration and management entities for Virtual Network Functions (VNFs).

The XCI is layered as follows. The first layer, NFV management and orchestration, includes the ETSI NFV MANO components such as the NFV orchestrator (NFVO), multiple VNF managers (VNFM), and the 5G-Crosshaul VIM extension referred to as the Virtual Infrastructure Manager and Planner (VIMaP). The second layer corresponds to the controller layer, composed of the network, computing, and storage controllers.

The tools over which these services can be provided include the VNF templates that are handled by an NFV Orchestrator (NFVO), and also the APIs through which it is possible to interact and control the physical and virtual resources of the infrastructure. The different cases are named according to the clients to which the services are offered: Over-the-Top (OTT), Mobile Virtual Network Operator (MVNO) and Mobile Network Operator (MNO).

Multi-Tenancy is a desired feature by 5G-Crosshaul to enable a generalized, flexible sharing of 5G-Crosshaul infrastructures among multiple network operators or service providers. A coherent management of multi-tenancy is required horizontally, unifying the concepts of infrastructure virtualization and multi-tenancy in all involved segments and resources. For this purpose, the Multi-Tenancy Application (MTA) is needed.

The Resource Management Application (RMA) takes care of optimizing 5G-Crosshaul resources in a centralized and automated fashion, in order to promptly react to network changes to meet the requirements of different client applications. The RMA relies on the XCI controllers for the actual provision and allocation of resources.

The main goal of Mobility Management Application (MMA) is to provide mobility management for scenarios such as vehicle mobility use cases and also to optimize traffic offloading for media distribution like Content Delivery Networks (CDN), TV Broadcasting.

The Virtual Infrastructure Manager and Planning application (VIMaP) is now logically part of the 5G-Crosshaul XCI and resides at the lowest level of the application hierarchy. It extends the ETSI/NFV Virtual Infrastructure Manager (VIM) by offering additional services and by implementing logic and policies for the optimal allocation and placement of resources.

The Energy Management and Monitoring application (EMMA) is an infrastructure-related application of the 5G-Crosshaul system. It aims at monitoring energy parameters of fronthaul and backhaul elements, estimating energy consumption and triggering reactions to optimize the energy footprint of the virtual network.

The Content Delivery Network Management Application (CDNMA) is an OTT application of 5G-Crosshaul related to the distribution of media content. Content distribution, especially video traffic, is expected to be the dominant contributor to the mobile data traffic demand.

The TV Broadcast Application (TVBA) aims to provide a solution for TV broadcasting & multicasting services utilizing the 5G-Crosshaul architecture, running as an OTT service. A TV broadcasting service is offered starting from the content of a live-source, which is processed till it is transcoded to the format required and introduced into the 5G-Crosshaul network.

The application layer is divided into two sub-layers. The higher sub-layer includes OTT applications, namely CDNMA, MMA and TVBA, which collaborate with one another and interact with lower sub-layer applications through their Southbound Interface. The lower sub-layer includes network-related applications: RMA, EMMA and MTA.

The Virtual Infrastructure Provider (VIP) instantiates its XCI, fully compliant with the ETSI NFV architecture. The recursion is possible thanks to the coordination of applications MTA, VIMaP and RMA. The VIMaP acts as an ETSI NFV VIM with planning features.

Glow’s role

Here at Glow, we help with 5G-Crosshaul engineering by focusing on providing end-to-end services to build 5G networks around the globe. We believe in being an active player in field support, one of the most critical components of a network buildout.

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