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GSM OVER SATELLITE SOLUTION FOR CRUISE SHIPS
An option is to see if the ferry is equipped with a satellite telephone. But these services tend to be expensive and do not solve the problem of being accessible via your own cell phone number. Increasingly, therefore, a Base Transceiver Station has become a permanent fixture on cruise ships and ferries. A BTS, connected to a cellular operator’s land-based Base Station Controller over a satellite link, enables passengers to use their regular GSM telephones while at sea. But given the expense of leasing satellite bandwidth, this alternative cannot serve a large number of simultaneous users either. So how can ship operators ensure that every passenger who wants or needs GSM service coverage will be able to afford it? Maritime Communications Partner AS, a Norwegian-based provider of onboard cell phone connectivity to cruise ships and ferries that provides global coverage through leading suppliers of maritime satellite services, has come up with an ideal solution. MCP has deployed GSM A-bis optimization gateways from RAD Data Communications to reduce costs by saving on satellite bandwidth. MCP’s BSC, located at its headquarters in the Norwegian coastal town of Grimstad, is connected over IP satellite modems to BTSs installed on a fleet of Danish-owned cruise ships that each year transport approximately 1.8 million passengers and 200,000 cars on eight routes traversing the North Sea between Denmark, Sweden, Norway, Holland, and Great Britain. MCP connected RAD’s Vmux-400 at both ends of those satellite links. The Vmux-400 is a standalone device that enables cellular operators to lower backhaul costs across the Radio Access Network by optimizing A-bis (BTS-to-BSC) bandwidth by a factor of up to 3:1. This significantly reduces operating expenses in applications in which cellular backhaul traffic has to be routed over satellites because terrestrial telecom infrastructure is unavailable. Eliminates Inefficiencies“RAD’s Vmux-400 A-bis and A-ter optimization gateway is the ideal product solution in this type of situation,” notes Toby Korall, Senior Product Line Manager at RAD. “Interoperable with equipment from other major vendors, the Vmux-400 ensures that satellite links are utilized as efficiently as possible, eliminating inefficiencies by not transmitting idle and silent frames,” he continues. “In this way, the Vmux-400 can reduce satellite, microwave or wireline bandwidth by 50 percent and more, enabling service providers to offer their customers a more attractive complete solution.” Unique Clock Regeneration Enables Backhaul over Packet Switched NetworksA unique feature incorporated into the Vmux-400 provides reliable regeneration of very accurate and sensitive 2.048 MHz TDM-based clocks for synchronized network operation between the BSC and each ship’s BTS. This enables the use of packet-switched networks, and, in this case, the IP satellite modems on-board the ships, for the transport of cellular voice traffic. The BTS on-board each ship includes two radio transceivers. Each radio receiver includes one time slot for signaling and SMS messaging and three time slots for voice and data. By dynamically supporting different speech codecs, RAD’s Vmux-400 allows up to twelve simultaneous calls using the higher-quality Full Rate codec when demand is low and up to 24 simultaneous calls using the Half Rate codec when demand peaks, doubling the number of cellular calls that are made to and from a ship at any one time. “RAD’s development of the Vmux-400 enables us to offer mobile services over an IP network with optimal bandwidth usage,” concludes Roar Walderhaug, MCP’s Chief Technology Officer. “The Vmux-400 operates very satisfactorily and has proven its high stability and robustness.”
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