Focus: Solving The Backhaul Conundrum
by Richard Deasington, Senior Director, Vertical Markets, iDirect
After a decade of domination by GSM standard second generation (2G) mobile phone networks, the world has embraced third generation technology (3G). Two-G systems laid a broad foundation for extending voice communication to the vast majority of the worlds population. Yet 3G holds even greater promise, enabling mobile operators to deliver both voice and data connectivity to subscribers and greatly expand their revenue potential.
Specifically, 3G technology provides a more profitable path to serving rural subscribers in both developing and developed countries. For many of these customers, 3G service represents the most affordable access to high-speed Internet connectivity sometimes the only access. According to the International Telecommunication Union (ITU), only 15.8 percent of the population in developing countries has Internet access and only 22.5 percent have a computer. In the future, Internet access will primarily be through mobile devices, and this represents a significant opportunity for mobile operators. In fact, a new report by Cisco projects reveals that mobile data traffic will increase 26-fold worldwide by 2015, with the population of mobile-only Internet users surging from 14 million in 2010 to 788 million in 2015.
Whats stopping mobile operators from pursuing these opportunities? One key challenge is backhauling rural network traffic in a way that makes it affordable for mobile operators to extend their services. Fortunately, 3G operators can look to recent progress in the expansion of 2G into rural areas through satellite backhaul as a model for similar growth. Thanks to falling infrastructure costs, the transition to IP and advancements in satellite backhaul technology, mobile operators are primed to bring 3G to the rural market.
How 2G Operators Cracked the Rural Market Through Satellite Backhaul
Traditionally, mobile operators relied on a technology called SCPC (Single Channel Per Carrier) to backhaul 2G Base Transceiver Station (BTS) traffic. It was a simple solution, but was often operationally inefficient because the capacity of the satellite link between two modems had to be configured for peak usage which typically occurs for only a few hours on the busiest day of the year.
Since satellite bandwidth is the most expensive element in budgeting for a remote base station, the wasted capacity from SCPC made it a poor value proposition for connecting remote and rural locations (see Figure 1). With the development of satellite networks based on TDMA (Time Division Multiple Access) mobile operators were now able to centrally manage a single pool of bandwidth that is shared across many sites. This provided a more cost effective way to allocate bandwidth based on the real-time requirements of each BTS location.
Will Satellite Backhaul Work Over 3G?
As Mobile operators have increased their service offerings to include data they began to update their infrastructure from Time Division Multiplexed (TDM) links to IP-based solutions to take advantage of the efficiencies offered by IP.
This migration has also been supported by innovations in technology in the satellite market to support the increased requirements for data transport and to help make the business case work for 3G connectivity in remote and rural areas. For example, the move to the second generation of the Digital Video Broadcasting standard, or DVB-S2, has made TDMA networks dramatically faster and more efficient. Likewise, the development of Adaptive Coding and Modulation (ACM) has helped mobile operators address the long-standing challenge of rain fade.
Another innovation, introduced by iDirect, is the integration of TDMA and SCPC onto a single platform (see Figure 2 on the next page). For the majority of cellular sites, traffic is a variable, which is ideal for TDMA. However, in some circumstances, links must remain at a fairly constant capacity, which requires SCPC capability.
To handle both scenarios, the iDirect system can easily switch a standard Evolution series remote working in TDMA mode to operating as a SCPC terminal with a few clicks of a mouse. This flexibility allows operators to change remotes between SCPC and TDMA as often as they like, and also allows an operator to start with a very small variable throughput at a remote site and then switch to a dedicated connection when there is a business justification for SCPC.
The development of femtocell technology is a third key innovation supporting the deployment of 3G networks. Femtocell technology, which is significantly less expensive than macro-cell technology, is a game changer in developing nations because it clears a path for mobile operators to extend data service to rural markets where mobile Internet access is the norm.
Making the 3G Business Case for Satellite Backhaul
To demonstrate the business case for satellite backhaul, lets examine the typical capital and operating costs associated with satellite backhaul and the typical ROI a mobile operator can expect.
In a TDMA network, the satellite equipment costs include a hub system at a mobile switching center and the remote routers located at base station sites. While there are many variables, for a network of a few hundred sites we could estimate the total cost for both hub and remote equipment at $3,000 - $6,000 per site.
In a typical SCPC network, each remote operates individually without a centralized hub. This makes each remote site more expensive, but eliminates the cost of the central hub. However, because the cost of SCPC modems are typically around two or three times that of TDMA systems, once the cost of a TDMA hub has been amortized across as few as twenty sites, the capital cost for TDMA is lower.
Advancements in mobile infrastructure have also reduced the cost of deploying a small cell to act as an eNode B at remote and rural locations, which lower the costs compared to traditional macrocell deployments.
When using a TDMA satellite system, such as the iDirect Evolution system, the bandwidth cost is directly related to the peak requirement for IP bandwidth across the whole network. This can be derived from the individual 3G remote base station (Node B) busy hour traffic figures. With iDirect, users can easily calculate this figure by calculating the peak bandwidth (in Mbit/s) and the amount of satellite bandwidth (in MHz) to determine the amount of traffic that can be supported on the network.
By combining TDMA and SCPC on one network, iDirect further reduces operating costs by allowing a mobile operator to switch a router from TDMA mode to a dedicated SCPC link based on usage needs. This also reduces equipment and labor costs by eliminating the need to swap remote hardware and maintain dual networks.
Efficient 3G Backhaul A Reality
New developments in IP-based satellite systems make satellite the ideal medium to reach the remote and rural sites that are the key areas lacking 3G coverage. The combination of lower cost and highly efficient satellite backhaul with the new generation of highly economic 3G base stations makes the business case for rolling out 3G to remote and rural areas a clear winner.
To learn more about the advantages of IP-based satellite systems for 3G backhaul and to see sample business cases that highlight the cost savings and potential revenue gains of deploying 3G networks over VSAT, visit iDirect.net to download the full white paper upon which this article is based...
About the author
Richard Deasington has more than 25 years of experience in the telecommunications industry, holding senior level positions in R&D and Engineering working closely on voice, data and transmission network systems. In his current role as Senior Systems Engineer Richard is currently responsible for leading iDirects engineering and sales efforts for GSM backhaul solutions. Prior to joining iDirect, Richard held Managing Consultant position at PA Consulting Group and later Questus Ltd where he focused on mobile systems: GSM and 3G systems in particular. He has been involved in a large range of mobile related activities from architecting the worlds first shared 3G network to leading the design of a range of network planning tools. Richard has written several well-known books and published many articles on subjects ranging from 3G power amplifier efficiency to network sharing and push-to-talk. Richard holds a Bachelor of Science degree with Honors in Computer Science with Biology from the University of London.