Mobile Backhaul Evolving with Small Cells and New Challenges

13 Apr
Mobile backhaul has always been a critical contributor to overall mobile network performance. Key performance metrics such as throughput, latency, and jitter have obviously always been important however, early generation backhaul network performance was often more deterministic. In the past, the backhaul network service, while still based on IP/Ethernet, was delivered over what was effectively a private line with guaranteed throughput and performance.  Furthermore, traffic patterns were also more deterministic – all traffic originated at the macrocell and was transported back to a central location such as a mobile switching center (MSC) where its performance could be relatively easily assessed. Backhaul bandwidth upgrades were performed on a more predictive basis. First generation mobile backhaul networks services the backhaul network could be more or less set and forgotten.

Today, backhaul networks must be more flexible: higher bandwidth, easily upgraded and evolvable, and more cost effective. Carrier Ethernet has become the dominant technology in Service Provider networks, providing both reliability and availability, evolving from best-effort technology found in local area networks to support network fault and performance monitoring capability. Service Providers require a comprehensive set of Operations Administration and Maintenance (OAM) tools. IEEE 802.1ag and ITU-T Y.1731 standards define these Service OAM tools that follow the service path and monitor the entire Ethernet service from end-to-end. With Service OAM, Service Providers can receive and offer service level agreement (SLA) assurances and reduce operating costs associated with manual network fault monitoring, truck rolls, and labor-intensive performance measurements.

Small Cells Introduce Added Complexity

Newer mobile technologies, namely LTE, drive the need for additional network capacity. Small cells address this need but increase backhaul network capacity. Small Cells introduce additional endpoints, deeper in the network closer to subscribers, and which backhaul networks need to be activated, monitored, optimized and assured. The current service activation and performance monitoring methodologies developed for macrocell networks now needs to scale to support the needs of small cell backhaul; however the processes themselves must become even more automated. It is no longer economically practical for operators to only deploy field technicians to perform tests and validate backhaul network performance. In addition, there is a resulting need by mobile operators to audit the ongoing performance of backhaul services to ensure performance guarantees are met. This is both to ensure optimal network performance but also to seek remuneration from backhaul providers in the event of SLA violations.

Small cell backhaul introduces additional layers of aggregation in the backhaul network, creating “hub-and-spoke” topologies, often resulting in performance visibility blindspots within the network. Traffic is backhauled from outdoor small cells (“spokes”) to an aggregation point (“hub”, often located at an existing macrocell) where it is combined with backhaul traffic from other spokes, and backhauled to another aggregation point typically in the mobile core, like a MSC location. Blindspots impact the ability to segment, monitor, and test services between the aggregation point (at the core) and the hub, and between the hub and the spokes. Blindspots result when the Hub networking equipment, typically a Cell Site Router (CSR), do not support standard OAM and maintenance endpoint (MEP) and maintenance Intermediate point (MIP) capabilities.

JDSU mobile backhaul fig.4


To download the full, 5-page article, visit theTNMO website.


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