Broadband Gear Report Feature for January 18, 2008

Delivering Best-in-Class Wireless Backhaul Over Cable Networks

By Scott Sumner, Accedian Networks

The expense of scaling existing TDM leased lines for rapidly emerging 3G, 4G/WiMAX services is compelling wireless operators to seek lower cost backhaul alternatives for the 200,000+ base stations covering the U.S. MSOs operating fiber-rich, high-bandwidth networks optimized for real-time service delivery are uniquely positioned to rapidly move into the wireless backhaul market.

Recent studies by SNL Kagan and GeoResults pegged wireless revenue at $164B USD in 2007 -- more than 40% of U.S. telecom spending. Backhaul will account for $10B of this revenue in 2008, increasing to more than $16B in 2009 as mobile data services grow 14% annually over the next 10 years.

By adapting their existing infrastructure for backhaul, cable operators can benefit from the explosive growth of wireless while building the means and expertise to introduce mobile services of their own.

Wireless Backhaul Performance Requirements

While legacy 2G cell networks employ legacy T1 backhaul links, emerging high-speed data networks require highly scalable, low-cost Ethernet connectivity. A recent poll of the world's top 20 mobile operators by the Synergy Research Group surveyed their backhaul requirements for 2010. Carrier Ethernet was the favored technology with more than 90% of operators selecting it for its operations and maintenance (OAM), performance and TDM circuit emulation, backed by Metro Ethernet Forum (MEF) specifications.

The report summarized wireless backhaul performance requirements for 2010 as:

20-100 Mbps Committed Information Rate (CIR) - bandwidth scalability

50-500 Mbps Excess Information Rate (EIR) - burst capability

Less than 3-5ms latency (one-way)

Less than 1-3ms jitter (one-way)

Up to eight unique service classes (CoS) for voice, Internet and video applications

Sub-50 ms Ethernet Virtual Circuit (EVC) recovery time

Between 99.99%-99.999% network availability

Ninety percent of wireless operators say they will monitor these performance metrics on leased backhaul networks to ensure they are working as promised. Wireless providers know that service quality is critical. The Yankee Group recently reported that 40% of customer churn is caused by poor reliability and voice quality.

Deploying the Right Broadband Gear

There are two components to adapting cable networks for backhaul: 1) installing Carrier Ethernet gear, and 2) making sure it works. Choosing the right network elements depends to a large extent on the network an operator has in place and the services it plans to deliver.

Carrier Ethernet is a natural fit with cable networks. A 2007 report by Iometrix showed that the best performing Ethernet private line and LAN (E-Line/ELAN) services were offered by U.S. MSOs.

However, wireless backhaul is significantly more demanding than business applications, and the second step - monitoring and maintaining the network - is critical. With performance defined in service level agreements (SLAs), troubleshooting with truck rolls just isn't enough.

Helping MSOs meet the challenge, service assurance solutions provide early warning of performance issues. Real-time monitoring information helps to quickly restore a faltering service, often before SLAs are breached. Having performance monitoring in place during and after deployment means MSOs can optimize their networks and then operate them with confidence.

Low-Cost WDM

In the white paper, "Low Cost WDM (LCWDM) System," Aurora Networks discusses how the company focused efforts on overcoming the limitations of CWDM technology, and to that end developed a technology that enables Aurora's transmitters to provide low-cost forward node segmentation tools for fiber links and node service areas as far away as 30 km, with six to eight forward wavelengths on a single fiber. Download it here.

SDV - Cost-Effective VOD

The significance of VOD means that it must be a reliable, high-quality service with low latency and jitter and no packet loss -- even as tens of thousands of video streams are transported from the headend to distribution hubs. In this VOD application note, which you can find here, Ciena describes a cost-effective build out that minimizes the use of fiber assets and enables switching of content from any server at the headend to any service group QAM resource at any hub.

Key Requirements for Service Assurance

A key part of service assurance is demarcation - an operator's ability to define the boundaries between its network and those of its customers. One popular approach is to deploy Ethernet network interface devices (NIDs) that serve as both a test head and an inline demarcation point at the edges of the network. By measuring performance as traffic passes through the NID, MSOs have a clear end-to-end view of their network that excludes impairments introduced by the wireless operator's core network or base station equipment. In a wireless backhaul application, a NID is installed at each base station and at the handoff to the wireless provider's network.

NIDs are inexpensive and capable, and that's a combination that allows operators to establish real-time performance monitoring without expensive test probes, portable test equipment or technician dispatches. A server automates tests and collects monitoring data from each NID to ensure that backhaul links meet SLA performance criteria, and provides real-time notification of performance failures and degradation.

To provide wireless backhaul-grade service assurance, NIDs should measure:

CIR, EIR and packet loss from real customer traffic

One-way latency and jitter to microsecond accuracy without expensive GPS equipment

CoS on different EVCs or VLANs to validate multi-service performance

Network availability and loss of service

To ensure they are not "part of the problem," NIDs should perform measurements and provide demarcation without introducing delay or jitter, and feature automatic failover protection. To permit rapid problem resolution, loopback testing and standard OAM functionality are essential.

The ability to cost-effectively monitor and maintain wireless backhaul networks is key to providing the carrier-grade that service mobile operators demand. Demarcation-based service assurance solutions provide cost-effective end-to-end coverage, allowing cable operators to capitalize on the rapid growth of mobile services while positioning themselves to deploy wireless services of their own.

Scott Sumner, M.Eng, is VP of marketing at Accedian Networks (www.accedian.com).