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Reaching Out Via Satellite Backhauling

By | October 1, 2007

      The use of satellite links to backhaul cell phone and other handheld wireless device traffic enables service providers to reach more customers and gain new revenue streams. For developing countries in particular, this ability to quickly and seamlessly deploy cell phone infrastructure to previously unserved areas can be crucial for supporting and enhancing economic development.

      Backhauling via satellite is becoming more attractive thanks to satellite equipment vendors that offer reliable, affordable and flexible solutions which can readily extend the reach of existing cellular phone and wireless broadband networks. At the same time, the idea of using satellite links to meet the growing demand for new third- and even fourth-generation Internet Protocol (IP)-based services — known as 3G and 4G services — including mobile broadband and TV is gaining acceptance in hybrid networking circles.

      The focus primarily is on Global System for Mobile Communications (GSM) cell phone networks, which accounts for about 80 percent of worldwide cellular traffic, far ahead of code division multiple access (CDMA) at 14 percent and time division multiple access (TDMA) at 6 percent,  according to “GSM Cellular Backhaul: Extending the Edge of a GSM Network,” a June white paper from iDirect Technologies Inc. “While GSM is one of the most pervasive technologies in the metropolitan mobile communications market today, it is also the standard of choice in developing markets. As the edge of existing networks continue to press outward, satellite becomes the de facto solution to extend to more remote regions.”

      According to Claude Rousseau, senior analyst for NSR, lower satellite backhaul costs per GSM telephone call are being achieved via more efficient backhaul architectures using voice compression and silence suppression along with new interface optimization techniques linking the GSM network’s base station controller to any number of remote base transceiver stations. “Legacy single channel per carrier (SCPC) carriage growth is slowing, leaving room for new access technologies such as demand assigned multiple access to be used exclusively or overlaid on top of the base network transport architecture,” he says. “Technologies currently exist for satellites to support low density, low traffic network topologies with each [transceiver] handling less than 2 megabits per second.”

      Satellite also can facilitate the migration from a high-bandwidth application-agnostic service provisioning such as Internet trunking to much lower-bandwidth, application-aware scenarios, says Rousseau. “Moving mobile networks from asynchronous transfer mode and time division multiplexing to IP is gaining ground, and all types of backhaul solutions providers are adapting their wares to this new paradigm,” he says. “IP and LAN-to-LAN mesh architectures for GSM backhaul, for example, can enable local switching at the [transceiver]. There is also some implementation of two-tier backhaul architectures that lower satellites’ entry points via extensions with wireless backhaul technologies like local multichannel distribution system or fixed WiMax.”

      As operators seek more bandwidth at the cheapest price they can exert huge pressure on a backhaul solution that needs to address all the inefficiencies of cellular network communications. “It means finding solutions to greatly diminish high overhead in a communications’ protocol such as IP, which eats up megahertz of bandwidth,” says Rousseau. “Multipoint-to-multipoint systems in either IP or Ethernet format are also gaining ground. Nowadays, vendors are coming up with their own LAN-to-LAN systems, and more two-tier satellite-wireless backhaul architectures are designed to address varying daily and weekly traffic patterns and loads.”

      Serving The Unserved

      In January, ViaSat Inc. and Verso Technologies announced they had tested a satellite-based GSM backhaul system in Papua New Guinea, for Telikom PNG Ltd. The network combines ViaSat LinkStar satellite and Verso NetPerformer A-bis-over-IP optimizer software technology, and Telikom PNG plans to deploy 50 GSM-over-satellite remote sites. According to Moorthy Hariharan, CTO for ViaSat VSAT Networks, VSAT systems integrated with IP-based transceiver link optimizers like NetPerformer can offer competitive and efficient backhaul extensions for cellular networks. Besides packetizing network traffic — reducing bandwidth requirements by as much as 50 percent without affecting voice quality — and dynamically assigning bandwidth based on voice and signaling traffic volumes, this DVB-S2 solution uses ViaSat technology that includes advanced bandwidth allocation techniques to assign features that prioritize calls and data traffic. Verso NetPerformer ensures that legacy voice and data traffic can share the same network infrastructure along with traffic flowing from Wi-Fi and WiMax hotspots.

      “The level of aggregation and peak-to-average traffic variations in end points drive the design choices for backhaul,” says Hariharan. “The continuing evolution in mobile and wireless networking standards makes it extremely important that operators and service providers implement scalable, extensible and upgradable backhaul systems. Adopting packet-switched IP for transport makes upgrading the system for advanced services a lot easier as well.”

      In Nicaragua, Empresa Nicaraguense de Telecomunicaciones, a subsidiary of Mexico’s America Movil, added GSM satellite backhauling to its rural telephony network using Gilat’s SkyAbis solution, which is a demand assign multiple access-based solution. With a Gilat SkyEdge hub in place, Empresa Nicaraguense deployed SkyAbis on top of the SkyEdge system, which can dynamically adjust bandwidth depending on real-time requirements at each transceiver.

      According to Daniel Enns, senior vice president strategic marketing & business development for Comtech EF Data, successful satellite backhauling requires bandwidth-efficient and scalable solutions for cellular operators. “Cellular backhaul-enabled satellite modems are capable of delivering optimal performance and spectral utilization at multiple layers,” says Enns, who adds that this is about selecting the right combination of forward error correction, modulation formats and code rates in order to simultaneously optimize satellite transponder power and bandwidth.

      A combined Memotec and Comtech EF Data solution called AbisXtender includes an A-bis-over-IP optimization platform and bandwidth-efficient, IP-enabled modems. The solution can eliminate a GSM operator’s dependence upon fixed lines and generate cost savings in low-traffic zones such as remote transportation routes. “Space segment costs are typically the most significant operating expense for GSM service providers considering satellite-based services,” says Enns. “Satellite transmission backhaul costs can represent up to 40 percent of the total operating expense related to [transceiver] deployment. Therefore, careful satellite network design and selection of the right technologies have a direct impact on the viability and profitability of the service.”

      Migration Underway

      A migration is underway from static SCPC networks towards more flexible architectures rooted in IP, says Mick Gardina, iDirect’s director of vertical sales. This is due to the fact that cell operators are realizing they can save money by not overestimating bandwidth demand due to the lack of accurate forecasts of traffic levels via dedicated SCPC satellite links. “iDirect’s IP-based solution enables [transceivers] in multiple time zones to be dimensioned over a single network to reflect each regions different usage characteristics,” he says. “This ability insures all real-time bandwidth requirements are met while simultaneously reducing the overall network bandwidth requirements and operating costs.”

      Besides sustaining speed and quality, iDirect’s deterministic-TDMA solution consolidates satellite transponder capacity from multiple small pipes carrying dedicated traffic into a single, large pipe carrying IP traffic. “Network operators require management tools that are intuitive, easy to learn and can be understood by a business manager as well as a network engineer,” says Gardina. “By incorporating a native IP platform, iDirect’s GSM backhaul solution allows an initial deployment to be rapidly and transparently upgraded as the market develops, positioning operators to keep pace with the deployment of new technology.”

      Simplifying Solutions

      Mobile operators need to connect their remote transceiver nodes with regional controllers over a reliable connection while keeping costs in check, says Rick Sanford, director, space and intelligence at Cisco Systems Inc.’s Global Government Solutions group. This is not easy to do when technological advancements, demand for new services and competitive pressures require mobile operators to continuously expand their networks and increase bandwidth capacity at cell sites, thereby driving up operating expenses. “The development of Wi-Fi and the growth of WiMax hotspots will only increase the need for satellite backhaul,” he says. “The wireless market is quickly moving towards an all IP-based architecture, so there will be the opportunity with IP-over-satellite solutions to simplify architectures and solutions through reuse of existing terrestrial wireless technologies for the satellite backhaul market. … The use of IP technologies in transitioning away from channelized services will give greater flexibility for service performance and enhancements as well as growth,” says Sanford.

      There are numerous challenges that need to be addressed, says Sanford, including the fact that long procurement and deployment cycles often can conflict with a company’s operational needs and undermine efforts to actualize networks in a timely fashion. “The satellite technology environment traditionally does not have a history of taking innovations quickly to the marketplace,” he says, adding that embedded networks and technology architectures make it difficult to rapidly scale or re-configure pre-existing satellite backhaul infrastructures.

      Thailand’s Shin Satellite has been providing backhaul services using its IPStar satellite broadband solution, says Patompob Suwansiri, assistant vice president of IPStar. The new IPStar maXX, a transmission control protocol accelerator which can support up to 100 users through a single terminal, is ideal for IP backhauling, especially hybrid Wi-Fi and WiMax-enabled IP networks, says Suwansiri. Lao Telecom in Laos is using an IPStar IP backbone for a GSM/CDMA backhaul network carrying voice and data traffic for more than 100,000 customers.

      “In the areas of mobile telephony, many systems now are now IP-based, thus making the mobile hybrid solution more cost effective,” says Suwansiri. “Hybrid solutions are not technically difficult. The real challenge is to have the right cost structure that will enable a viable business model. It (also) is important that satellite providers have partners on the ground that take care of the implementation and maintenance of the system.”
      Cell phones make life easier, and satellite solution providers are demonstrating they can provide an easier and cost-effective pathway to enhanced revenue streams.

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