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Designing Mobile Backhaul Networks: The Road to Increased Capacity

Session bandwidth optimizers provide the additional bandwidth to service the growing number of subscribers – now & in the future

The rapid growth of smartphones, tablets and netbooks are forcing mobile service providers to consider how best to meet the growing demands for rich data services that are straining mobile network capacity and eroding profits. Because their networks were originally designed for the low bandwidth requirements of voice traffic, mobile service providers today have only a limited set of options for increasing capacity to accommodate data services. However, most of these options are expensive and often time-consuming to deploy, and include adding more leased lines, moving to fiber, increasing the microwave spectrum, and using Ethernet ring.

How can mobile service providers better design mobile backhaul networks to solve these issues? To answer this question, let's first dive into the many factors that shaped today's capacity requirements.

The Heart of the Issue
Service providers originally designed and built mobile backhaul networks for voice traffic. At the time, voice was the predominant service flowing through those networks and could be accommodated without too much difficulty and expense. But between 2005 and 2010, the situation changed. Voice average revenue per user (ARPU) began to decline, competition became intense among providers and bandwidth-hungry data services were introduced. Shortly thereafter, Apple's iPhone led the avalanche of smartphones that were designed to be the "gateway" to the Internet, and to the various streaming services that the Internet offered. This accelerated the development of 3G networks, and network designers had to scramble to keep up. The ever-increasing proliferation of these devices, and the data-hungry applications they use, placed heavy demands on these networks, creating the need for even more advanced networks to handle high-end services like video calling and mobile TV. Now, network designers are scrambling once again to build network solutions that alleviate these heavy demands on the network while providing an enhanced user experience.

How to Increase Backhaul Capacity
Increasing backhaul capacity is critical to alleviating demands on today's networks. Service providers and network designers have five options for increasing their backhaul capacity:

  • Add more leased capacity to existing copper or fiber lines
    Service providers can always lease more lines to help handle higher traffic, but leased-line charges can be extremely expensive - often the largest operational expense for service providers - eliminating this as a viable option for the long term.
  • Roll out fiber
    We're all dreaming of the day when we can lay down fiber everywhere without worrying about limits on bandwidth anymore. Again, the capital expenditure for this is monumental, and deployment takes a long time. In addition, laying fiber can be impractical and costly in both densely populated urban areas and sparse rural areas.
  • Increase microwave spectrum
    Upping microwave spectrum can increase bandwidth by about one-third, but creates two additional problems: (1) high cost from mandatory license fees and (2) occasionally scarce amounts of spectrum in certain parts of the world.
  • Upgrade the SDH microwave to Ethernet ring
    Upgrading the synchronous digital hierarchy (SDH) microwave to Ethernet ring can double capacity, but its 256 QAM modulation scheme works only in clear weather and over short distances. However, both capital and operational expenses are very high, and upgrades can take several months in urban areas.
  • Optimize streams in the backhaul segment
    Optimizing bandwidth for streams in the backhaul segment of existing mobile networks, such as Abis (2G) and Iub (3G) streams, can be an attractive option for scaling mobile backhaul capacity from both a cost and network bandwidth perspective. Optimizing the mobile backhaul segment can typically double the bandwidth capacity at a significantly lower capital and operational cost than the above options. Best of all, deployment typically takes only a few days.

Figure 1: Backhaul in the Mobile Network

Backhaul Optimization: Meeting Demand Without Breaking the Bank
The most direct and cost-effective way to meet network demands is through backhaul optimization. Network designers have built today's networks by adding to existing infrastructure in a piecemeal fashion. True 4G networks, with all-IP structure, will require massive capital investments to become a reality.

However in today's environment, service providers and network designers must do the best they can with available resources to meet increasing demand - without breaking the bank. Mobile backhaul bandwidth optimization helps relieve these two issues:

  • Timing: New features and services for mobile customers are being rolled out at an alarmingly high rate for designers. In just a few short years, consumers migrated from voice services to full-scale mobile broadband Internet. Now, technologies, like HD video calling, and various other forms of streaming high-resolution video are in high demand - with the next wave of new services just on the horizon.

The bottom line is that customers are adopting these new expanded services quickly and demand is increasing much more rapidly than many service providers can deliver them. Designers are left scrambling to upgrade networks as quickly as possible to handle these bandwidth-hungry services. Bandwidth optimization's rapid deployment addresses this time crunch directly.

  • Expenses: True 4G technology, with its all-IP packet switches and 1 Gb/s data rates, requires a massive additional capital expenditure. Very few service providers can afford to uproot their entire existing networks. Instead, the mobile backhaul segment provides the perfect opportunity to meet increased demand, improve network performance and reduce expenditures for upgrade - helping to keep profits on the rise.

How to Optimize Mobile Backhaul Networks
Session bandwidth optimizers (SBO-MBs) for mobile backhaul are an effective means to optimize the backhaul segment of a mobile network. In fact, in field trials, SBO-MBs actually doubled a mobile service provider's backhaul capacity.

Figure 2: Session Bandwidth Optimizer Optimizing Various Streams in the Backhaul Segment of a Mobile Network

An SBO-MB is a standalone system that optimizes bandwidth in the backhaul segments of both asynchronous transfer mode (ATM) and IP-based streams. Because SBO-MBs are based on units placed within the current physical backhaul segment, it is not as disruptive or costly as other alternatives for increasing bandwidth capacity.

SBO-MBs monitor and maintain the key performance indicators (KPI) by which mobile backhaul infrastructure performance are measured. These include delay, jitter, bit error rate, and availability. Following the suggested KPIs is critical to maintaining high subscriber quality of experience (QoE) and to meeting Service Level Agreements (SLAs) for voice and data services.

In addition, SBO-MBs leverage advanced bandwidth optimization, statistical multiplexing and grooming techniques that typically double the capacity on backhaul links - significantly increasing speed for the end user. Moreover, this method preserves the quality and integrity of the original data traffic. By combining sophisticated optimization with Quality of Service (QoS) protection techniques, these devices can provide CAPEX and OPEX savings for a mobile operator's backhaul segment while increasing backhaul capacity.

On the input end, an SBO-MB optimizes 2G, 3G, native IP, or pulse-code modulation (PCM) streams and transmits a combined optimized stream over time-division multiplexing (TDM) and/or Ethernet. On the other end of the backhaul segment at the radio network controller (RNC)/binary synchronous communications (BSC) site, a second SBO-MB receives the optimized stream, restores the original streams (2G, 3G, IP, or PCM), and provides them to the RNC, BSC, or other networks as appropriate.

Some of the additional functionality SBO-MBs provide includes:

  • Abis optimization for 2G networks
  • ATM and IP-based optimization for 3G networks
  • Auto detection of Abis and ATM-based streams
  • Pseudo-wire capability (TDM services over IP, SAToP, CESoPSN)
  • Timing over packets (TOPSync, IEEE1588v2, SyncE)

TOPSync is extremely important for timing synchronization between the base transceiver station (BTS)/Node B and the BTS/RNC when they are connected over a packet segment because the cell tower and the BSC/RNC need to be in close synchronization for correct intercell handoffs that eliminate dropped calls.

Along with optimizing mobile streams, an SBO-MB can optimize PCM streams from TDM networks and native IP streams (from an IP-PBX, for example).

SBO-MBs also have several additional benefits:

  • Wide range of deployment architectures: SBO-MBs support numerous network topologies, including Point-to-Point (PTP), Point-to-Multi-Point (PTMP), ring, drop-and-continue, and many others.
  • Data-offload configuration: SBO-MBs can use overlay to separate the 2G voice/data and 3G voice/signaling from the high-speed packet access (HSPA) data offload path.
  • Carrier-grade reliability in a small footprint: SBO-MBs provide carrier-grade reliability in a 1 RU chassis, unparalleled in the industry, for significant CAPEX savings.
  • Leading transmission standards: SBO-MBs support a variety of transmission technologies, including TDM, IP, and Ethernet. Support for multiprotocol label switching (MPLS) is planned.

A Glance into the Future
While we don't know specifically what the future holds, one thing that's clear is that consumers will continue to demand innovative and quality services. In order to keep up with this demand, service providers and network designers must cost-effectively increase network capacity while providing users with the high quality that is expected of today's applications and services.

Although there are several options for augmenting network capacity, session bandwidth optimizers provide the most cost-effective option for doing so on a mobile network by simply optimizing the backhaul segment. Session bandwidth optimizers deliver services that encourage customer retention as well as attract new customers but, more important, they provide the additional bandwidth to service this growing number of subscribers - now and in the future.

More Stories By Jim Machi

Jim Machi is Senior Vice President of Marketing for Dialogic Corporation, responsible for developing marketing strategy and driving marketing communications. He is also responsible for long term product planning and strategy for all Dialogic products. Dialogic develops open systems based voice, video and signalling products targeted for both the enterprise and service provider market segments.

Machi has been with Dialogic Corporation since 1998 where he was Director of Product Management, working to develop the company's IP telephony roadmap and strategy and then as Director of Product Management for its entire product line. He stayed with the Dialogic division after the Intel acquisition of Dialogic in 1999, with product management and marketing responsibility for the division’s products before the Dialogic assets were acquired by Eicon Networks in October, 2006, forming a new Dialogic.

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