Mobile-backhaul networks were never meant to handle the amount of traffic they currently carry. With traffic expected to skyrocket due to the massive influx of smart phones and the like, mobile operators are searching far and wide for solutions.

Laying miles of fiber would solve the issue, but break the bank. Some service providers will opt to optimize bandwidth, driving more traffic down the same pipe. Others may look to increase microwave spectrum or use Ethernet ring.

But what is ultimately going to give service providers the most bang for their buck? Furthermore, how are engineers going to be able to better design mobile-backhaul networks to solve these issues?

The Root Of The Problem

When service providers designed and built mobile-backhaul networks, voice was the predominant service flowing through those networks. Thus, it could be accommodated without too much difficulty and expense. The predominant backhaul link was T1/E1 lines and SONET/SDH STM-1.

Between 2005 and 2010, the situation changed radically. Voice average revenue per user (ARPU) began to decline, competition became intense among providers, and bandwidth-hungry data services were introduced. Not long after, Apple’s iPhone led the avalanche of smart phones designed to be the “gateway” to the Internet and to the various streaming services it offered.

These developments accelerated the push for 3G networks, causing network designers to scramble to keep pace. The ever-increasing proliferation of these devices and the data-intensive applications they use burdened these networks.

As a result, demands grew louder for even more advanced networks to handle high-end services such as 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 delivering an enhanced user experience.

Capacity-Boosting Options

To increase backhaul capacity, service providers and network designers can choose among five options:

  • Add more leased capacity to existing copper or fiber lines: Service providers can always lease more lines to help handle higher traffic. However, 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. Again, the capital expenditure for such a scenario is monumental, and deployment would take 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 it creates two problems: high cost from mandatory license fees, and 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 rings can double capacity, but its 256-state quadrature amplitude modulation (256-QAM) scheme works only in clear weather and over short distances. Once again, though, 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 (Fig. 1), such as Abis (2G) and Iub (3G) streams, offers an attractive option for scaling mobile-backhaul capacity from both a cost and network bandwidth perspective. Usually, it doubles the bandwidth capacity at significantly lower capital and operational cost than the above options. Best of all, deployment typically takes only a few days.

The Big Crunch

Network designers have built today’s networks by adding to existing infrastructure in piecemeal fashion. However, true 4G networks, with all-IP (Internet protocol) structure, will require massive capital investments to become a reality.

In the current environment, though, service providers and network designers must do the best they can with available resources to meet increasing demand—without breaking the bank. That’s where mobile-backhaul bandwidth optimization steps in, since it helps relieve two key issues:

  • The time crunch: New features and services for mobile customers are rolling out at an alarmingly high rate. 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. And, don’t look now, but the next wave of new services looms on the horizon.

    The bottom line is that ramped up adoption of, and demand for, new expanded services is surpassing service providers’ abilities to deliver them. This leaves designers in a perpetual frenzied state to upgrade services to meet bandwidth needs. Bandwidth optimization’s rapid deployment addresses this time crunch directly.
  • The expense crunch: Network designers and engineers everywhere rolled their eyes when service providers like Sprint and Verizon announced their 4G networks (with some derisively ascribing them the moniker “FauxG”). Although these new systems will increase speeds when deployed, the International Telecommunication Union doesn’t consider them to be “4G speed.”

    True 4G technology, with its all-IP packet switches and 1-Gbit/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.

Optimization Method

One effective strategy for optimizing mobile backhaul is to use session bandwidth optimizers (SBO-MBs). In fact, in field trials, SBO-MBs actually doubled a mobile service provider’s backhaul capacity (Fig. 2).

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, they’re not as disruptive or costly as other alternatives for increasing bandwidth capacity.

SBO-MBs monitor and maintain the key performance indicators (KPIs) that measure mobile-backhaul infrastructure performance. These include delay, jitter, bit error rate, and availability. Following the suggested KPIs is critical to maintaining high subscriber quality of experience (QoE) and 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, leading to significantly increased 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 save on capital expenditures and operational expenditures for a mobile operator’s backhaul segment while boosting backhaul capacity.

At 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. At the other end of the backhaul segment—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 delivers them to the RNC, BSC, or other networks as appropriate.

SBO-MBs also include 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), and 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’re connected over a packet segment. That’s because the cell tower and the BSC/RNC must 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 offer other benefits:

  • Wide range of deployment architectures: Support of numerous network topologies, including point-to-point (PTP), point-to-multi-point (PTMP), ring, drop-and-continue, and many others.
  • Data-offload configuration: Overlay can be used 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: Carrier-grade reliability comes in a 1 RU chassis, which leads to significant capital expenditure savings.
  • Leading transmission standards: Support of various transmission technologies, including TDM, IP, and Ethernet. Support for multiprotocol label switching (MPLS) is planned.

Looking Ahead

The mobile landscape has changed dramatically over the past five years, and burgeoning consumer demands for new services will continue that pattern. Service providers and network designers must respond quickly, and cost-effectively, to augment network capacity while maintaining a high quality of experience for end users (and ultimately gain a competitive advantage)

Session bandwidth optimizers make that possible. They provide a cost-effective option for increasing capacity on a mobile network by optimizing the backhaul segment. Not only do they offer services that encourage customer retention as well as attract new customers, but more importantly, they deliver the additional bandwidth to service this growing number of subscribers.