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By David Park, VP, Product Marketing, BelAir Networks
Introduction
It is reasonably estimated that backhaul accounts for one-fifth of the overall mobile network cost, and analysts expect this to increase dramatically – Infonetics estimates that the $16 billion that carriers spent on mobile backhaul link services in 2005 will double by 2009. In fact, with the arrival of 3G (and 4G), the requirement for closer cell site spacing will require even more backhaul, and it’s related expense. Increased support for data and multimedia services will also increase typical TDM (T1/E1) connections per site from 2-4 today to more than 12 in a few years – adding to the burden of backhaul costs.
In order to remain competitive, mobile operators must deliver a compelling ‘quad play’ of voice, video, data and mobility. For many mobile carriers, the highest service revenue opportunities are in dense city environments, which often present coverage challenges or deadzones. With the emergence of microcell and picocell network topologies, the use of mobile networks to deliver a full suite of broadband services into these urban markets is no longer constrained by technology limitations, access bandwidth, or coverage issues. The challenge lies in developing a compelling business case in which new revenues from broadband services aren’t consumed by the high cost of backhauling the traffic from an increased number of cells over T1/E1 leased lines.
Traditional point-to-point wireless solutions can provide an alternative to leased line backhaul. But these relatively expensive wireless backhaul approaches can only be applied to mobile backhaul across predominantly open areas and even then, they inherently lack resiliency. They are not effective in dense urban canyons where line of sight limitations and the need to collocate with mobile basestations dictate a pole- or building-mounted approach closer to ‘street level’. In fact, carrier-grade wireless mesh backhaul can address both the opportunities and challenges inherent in delivering broadband services in dense, customer-rich urban environments, at about one-fifth of the cost per link of traditional wireless solutions. Carrier-grade switched wireless mesh enables mobile operators to reduce their backhaul operating costs while achieving the required resiliency and capacity. These savings enable carriers to cost-effectively increase revenues through high-value broadband services while optimizing their cell coverage and controlling costs through re-use of valuable licensed spectrum.
Macrocell backhaul
Offering significant savings the traditional TI/E1 approach, switched wireless mesh can backhaul multiple macrocells and aggregate the traffic to a single wired location, as shown in Figure 1. While reducing the number and associated cost of leased lines, this approach increases the total capacity available at each cell site. Moreover, eliminating the need for wired backhaul at each cell location also reduces network design and installation costs.
With the capacity to carry both TDM and IP traffic, the solution solves legacy backhaul costs while accommodating future growth scenarios.
Figure 1: Wireless mesh backhaul aggregating macrocells to points of wired network connection.
Picocell Backhaul
One of the reasons small cells have not been deployed in great numbers has been the high operating expense (OPEX) and build costs of deploying fractional TDM circuits. Switched wireless mesh can be used to backhaul over 50 picocells, or as many as 25 microcells – aggregating the traffic to a single wired location, as shown in Figure 2. Operators now have a practical, cost-effective solution that enables easy deployment of more microcells and picocells in cities without increasing backhaul costs.
Figure 2: Switched wireless mesh backhaul aggregating picocells to a single point of wired network connection.
Integrated Circuit Emulation
Integrated Circuit Emulation Module (CEM) allows connection for up to 4 T1 or E1 circuits, as shown in Figure 3.
The CEM takes the TDM bits, including framing and alarms, and ‘packetizes’ them with a pseudo wire header to a standard format – draft-ietf-pwe3-cesopsn-07.txt. The packets are time stamped, using RFC3550 RTP, enabling the remote CEM to recover and regenerate the clock. The result is complete and seamless emulation of T1/E1 circuits over a low-latency IP connection.
The BelAir node maintains full T1/E1 bit, byte, frame and alarm continuity, as well as transporting and recovering clock to 3GPP specifications. The simultaneous IP and TDM capability provides support for both legacy and 3G basestations.
Figure 3: BelAir’s Integrated Circuit Emulation Module carries four T1/E1 lines over IP.
Low cost unlocks broadband revenues
Whether supporting picocell, microcell or macrocell deployments, a switched wireless mesh backhaul can deliver low cost mobile backhaul with carrier-grade resiliency on a multi-service architecture. In fact, wireless mesh backhaul delivers significant savings, as shown in Figure 4, strengthening the business case for new opportunities while reducing costs to make the existing business more profitable.
Figure 4: Example cost comparison of BelAir wireless mesh backhaul vs. traditional backhaul for a cluster of 5 cell sites.
In the above example, the BelAir switched mesh backhaul solution offers OPEX savings of 60% per month in year 1. Even when the capitalized cost of BelAir equipment is factored in, overall cost savings are nearly 40% year 1 and 50% by year 3.
“This innovative use of mesh technology is a technical advance that offers economic benefits for operators who are battling increasing transport costs. The BelAir solution is the first wireless mesh that delivers the timing and quality of service required for mobile backhaul across multiple hops. This mesh approach is attractive as a low cost technique for facilitating backhaul to micro and picocellular sites.” Philip Marshall, Vice President, Yankee Group
Benefits for mobile operators
Improved reliability
Switched mesh wireless architecture provides multiple data paths through the network and offers improved reliability over point-to-point wireless mesh. In the event of a link failure, traffic is automatically rerouted to the next best alternative path, ensuring uninterrupted transmission through a ‘self-healing’ wireless mesh network.
Carrier-grade performance
Each radio can transport 6 to 8 T1s for a total throughput of 25 Mbps. Consequently, a four-radio BelAir200 can transport 100 Mbps or 24 T1s of payload.
The Circuit Emulation Module (CEM) on the node includes advanced clock recovery algorithms that meet the timing requirements of the mobile base transceiver station (BTS). It connects directly to any standard CDMA, WiMAX, GSM or 3G cells without the need for customization or network changes
Low latency
Low latency is critical for delivering carrier-grade service. The patented switched mesh architecture discussed offers latency of less than 3 milliseconds per hop on a moderately loaded network, with little variability.
Quality of Service
This switched mesh architecture delivers carrier-grade QoS, enabling Service Level Agreements. BelAir’s sophisticated routing cores and radio modules feature advanced QoS tagging and classification capabilities with multiple queues on the wireless mesh backhaul and wireless access network, enabling operators to provide preferential bandwidth and latency characteristics to support voice, along with other traffic types, end-to-end throughout the network.
Flexibility
This wireless mesh architecture enables greater design flexibility by allowing operators to route traffic around obstacles and eliminating the requirement for line of sight between basestations and wired locations.
Fast time to market
Typical TDM circuits can take up to 90 to 180 days to implement, whereas wireless mesh circuits can be installed in hours. With wireless mesh backhaul, operators can take advantage of faster time to market in new and emerging broadband services opportunities.
Rugged outdoor equipment
Compact, easy to install, and built specifically for outdoor deployment, these carrier-grade nodes can be mounted directly on buildings or light poles, in parking lots or city streets and are designed to blend in with the physical infrastructure.
Greater resiliency
For macrocell, microcell and picocell deployments, carrier-grade wireless mesh backhaul provides greater resiliency than point-to-point topologies.
Multi-service architecture
BelAir’s wireless mesh solutions are built on the industry’s only multi-service architecture for wide-area wireless broadband deployments of Wi-Fi, WiMAX, and 3G Mobile networks. Supporting both access and backhaul, BelAir nodes deployed for mobile backhaul can also deliver VoIP over Wi-Fi, and hotzones of High-speed Internet access over the same wireless mesh.
Carrier-Grade solution
BelAir Networks switched mesh architecture is a key element in delivering greater bandwidth and higher performance. Leveraging standard carrier-grade router platforms, along with QoS tagging and classification capabilities, applications are able to be transported across the wireless mesh networks with little to no latency.
Carrier-grade resiliency provides for self-healing capabilities in the event of a link failure. Mission-critical applications are not affected during a link failure because they are rerouted to the next best alternative path, thus ensuring their transmission through the wireless mesh network.
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