In order to backhaul voice and data through the same channel, operators are upgrading their existing infrastructure and implementing new technologies in the backbone network. Telecom traffic can be backhauled through several different mediums including microwave, satellite, DSL lines and Wi-Fi, depending on the purpose of deployment. The basic requirement is to develop backhaul infrastructure which is flexible, reliable, scalable and cost effective, and helps in ensuring quality of service and operational efficiency. It should be able to support both legacy and IP services as well as future technology requirements.

A look at some of the existing and emerging backhaul options for operators…

Copper platform

Two decades ago, copper was the most effective and probably the only transmission channel used by operators for backhauling traffic. However, the introduction of wireless technologies and increased adoption of mobile services have rendered this platform ineffective in recent years. Limited capacity and high costs have resulted in phasing out of copper technology by most operators, who have now shifted to microwave and fibre platforms for backhauling voice and data traffic.

Microwave technologies

Currently, microwave backhaul is used at about 80 per cent of cell sites in India, primarily due to the challenges associated with wireline backhaul deployments. An operator needs to acquire a frequency spectrum licence for establishing a microwave backhaul system. Less expensive equipment and ease of installation are some factors which have made it a preferred platform for backhauling 2G traffic.

The introduction of 3G/4G services coupled with the rising adoption of smartphones, however, has resulted in huge volumes of data traffic flowing through operator networks, which is putting pressure on their existing backhaul infrastructure. For instance, industry estimates show that 3G deployments by operators require backhaul capacities in the range of 12 Mbps to 30 Mbps per base transceiver station (BTS), which is three to four times higher than the capacity requirement for 2G deployments. These requirements will increase further as operators deploy long term evolution (LTE) technology, which has a peak capacity of 50-100 Mbps per cell site.

Consequently, there have been advancements in mobile infrastructure to make it workable for backhauling high speed next-generation traffic. Microwave equipment vendors offer advanced all-packet backhaul solutions that ensure efficient spectrum utilisation. Improvements such as multichannel link aggregation, header compression, co-channel dual polarisation and adaptive coding and modulation are making microwave transmission systems a near-ideal backhaul solution for LTE networks.

Further, microwave is a more flexible medium as compared to other backhaul platforms such as fibre. Once placed in the ground, fibre is static while microwave equipment can be moved quickly to a new route, especially if a transmission route becomes redundant. Microwave equipment can be easily reconfigured to change capacity, radio signal strength and other characteristics to meet dynamic backhaul requirements. Vendors have also developed solutions that ensure availability even in transient fading conditions, guarding the links against inclement weather and other interferences.

Satellite backhaul

With saturation in urban markets, operators are banking on rural customers to drive future growth. The use of satellite technology, especially VSAT, is growing rapidly as it enables operators to backhaul voice and data traffic to remote and rural areas. It is an effective cellular backhaul solution for areas where the use of traditional terrestrial means such as fibre, cable or microwave is very difficult.

Besides backhauling mobile BTSs in remote regions, telecom operators are increasingly using satellite backhaul for connecting banks, automated teller machines, e-governance, e-learning, stock trading, internet/intranet services, etc. For instance, Bharti Airtel uses satellite to provide connectivity and value-added services to its customers, as well as to deliver time division multiplex/TDMA technology in Ku-band and provide single -channel-per-carrier services in C-band.

Deploying VSAT technology which has IP at the core improves the scalability of the network and allows efficient transport of voice and data services to and from remote locations. IP-TDMA-based satellite backhaul has proven to be very useful in areas where traditional satellite technologies are either an expensive option or are not very bandwidth efficient.

Sharing of satellite services is also increasing as the cost of expanding reach in rural regions is pooled. Advancements in satellite technologies have allowed operators to share bandwidth between multiple BTS locations and facilitated integration with the core of the network.

Fibre solutions

Fibre is the optimum platform for backhauling, given its reliability, scalability, huge bandwidth capacity and long-term operational benefits. Further, fibre needs to be deployed only once and upgrades to higher bit rates can be achieved by simply changing transceivers at the terminal site. For instance, a fibre link which was originally installed to support a bandwidth of 100 Mbps can be easily reconfigured to 10 Gbps. In contrast, this transition to higher bit rates for microwave backhaul is difficult as it requires a completely new set of point-to-point or point-to-multipoint equipment for every upgrade.

While fibre clearly has advantages over wireless solutions in several aspects, its deployment is not economically and operationally viable in most scenarios. First, it is a very expensive option as it involves high installation/operational costs due to trenching, right-of-way charges, leasing, etc. Further, operators in India have reported several instances of cable theft and cable cuts, which add to the maintenance and repair costs.

Small cell solutions

The number of small cell deployments in India would increase as operator networks are clogged by the increasing data traffic flow. Small cell backhaul, therefore, will emerge as a key segment within the backhaul market in the future.

Small cell solutions can be used for capacity upgradation at enterprises/hotspots in cities, residential conglomerations or to serve not-spots in remote rural areas. While fibre/copper or high capacity micro/milli wave solutions can be used in an urban environment, satellite is a preferred choice for remote regions where deploying fibre/microwave solutions is challenging. The total cost of ownership, efficiency and performance are the three main criteria which determine the viability of a small cell backhaul solution. Globally, operators are deploying a mix of backhaul solutions depending on capacity, functionality and reliability constraints.

Industry analysts believe that backhaul complexity and challenges will be more severe in the case of outdoor picocell and microcell deployment as compared to an enterprises/hotspot scenario where complementary platforms such as DSL and fibre are generally available. Self-organising network technologies are likely to play an important role in backhaul deployments in the country.

Conclusion

As advanced access technologies such as 3G/4G achieve mass adoption in the future, providing complementary high capacity backhaul support will become crucial. While operators may have a preference for one backhaul technology over another, no single platform will independently meet all their requirements. Arriving at the right mix or hybrid of technologies/platforms for providing backhaul will be imperative from both a cost and business optimisation perspective in the future.

Going forward, capex- and opex- strained Indian operators are likely to undertake large-scale upgradation of their existing microwave backhaul systems. However, fiberising a significant part of backhaul, at least in urban areas, will become a technology choice that not many operators will be able to avoid.