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  3. The Flying Phone Box A surprise for air travelers The strides made in satellite-communications technology in recent year

The Flying Phone Box A surprise for air travelers The strides made in satellite-communications technology in recent year

admin2013-06-17  39
问题                            The Flying Phone Box
    A surprise for air travelers
    The strides made in satellite-communications technology in recent years are at last yielding benefits for air travelers, particularly executives who need to keep in touch with their offices. Five airlines— three of them based in the Asia-Pacific region—have recently equipped aircraft to offer outbound (向外的)telephone calls to anywhere in the world using a new satellite system. And in the not-too-distant future, businessmen will be able to send faxes in flight, too.
    Air Canada, Qantas of Australia, United Airlines of the US and Japan Air Lines have at least one satellite-communication aircraft apiece. Hong Kong’s Cathay Pacific Airways is also about to offer the service and several other airlines are expected to follow. The calls, dialed directly and charged to a credit card, will cost about US $ 9 ～ 10 per minute.
    The earlier flying phones
    Phone communications from aircraft are not entirely new. For some time, telephones have been available to passengers on US internal flights, for example, and on private jets.
    But these systems have used cellular phones operating on very high frequency radio links. These systems—the same links that keep pilots in touch with flight controllers—have either limited range or low quality and reliability, particularly over vast oceans such as the Pacific. By contrast, the new satellite service will provide clear links instantly to destinations around the world.
    Technological obstacles
    Several technological problems had to be resolved before the service could be introduced. One was to define an effective technical standard, Airinc 741, that guarantees compatibility among different manufacturers’ avionics systems—essential if the service was to be truly global.
    Another was to make reliable antennas(天线) small enough and light enough to mount on aircraft of different types. And a third was to perfect voice-coding algorithms(规则系统), which tell machinery how to break down voice signals into digital signals for transmission at the standard rate of 9,600 bits a second.
    A further drawback, for any type of call routed by satellite, is an uncomfortable time lag between words being spoken and received. Because of the distance that signals have to travel, there is a delay of about a quarter of a second. With airborne calls, there is the potential for a double delay as signals arriving via satellite at a ground station are passed on via another satellite to their destination.
    To avoid this problem, ground stations have been equipped to identify calls from aircraft and route them to coaxial or fibre-optic cables for the second lag of their journey. Surface links, though long, are still considerably shorter than the 72,000-km round-trip into space. Most calls will therefore not suffer the double delay.
    The International Maritime Satellite Organization (Inmarsat) approved the initial sitcom system for commercial service last November ’after two years of trials. Besides the handful of aircraft operated by the five major carriers who have signed on to the system, about two dozen company jets have fitted with the necessary equipment.
    A new technology
    The technology has three components: antennas and associated equipment on board planes, communications satellites, and ground stations.
    In the course of development, antennas have lust both their dish shape and several kilograms. Even so, antenna and avionics weigh as much as two occupied scats. One obstacle to further weight savings, however, is that lighter antennas are more easily confused by the plethora(过多) of satellites now circling the Earth.
    The satellites themselves are provided by Inmarsat, a London-based cooperative of 64 nations. One operational satellite and several ’back-ups cover each of three zones the Atlantic Ocean (East), the Pacific, and the Indian Ocean. A fourth zone, Atlantic Ocean (West), will go into action later this year.
    Ground stations
    Three consortiums(国际财团) are competing for airlines’ business by setting up ground stations to accept calls bounced off Inmarsat satellites and channel them into telephone networks.
    Skyphone, comprising British Telecom International, Norwegian Telecom and Singapore Telecom, has worldwide coverage through stations at Goonhilly, England; Elk, Norway; and Singapore. US satellite corporation Comsat has joined up with Japan’s international operator, KDD, with ground stations in Yamaguchi, Japan, and Southbury and Santa Paula, on the US East and West Coasts.
    In addition, the Societe Internationale de Telecommunications Aeronautique, a cooperative owned by airlines, has combined with Teleglobe Canada; France Telecom and OTC of Australia to create Satellite Aircom, with ground stations in Perth, Australia; Aussaguel, France; Weir, Canada; and Niles Canyon, US.
    Advantages and prospects
    According to Hans Karisen, Inmarsat’s marketing manager for aeronautical (航空的) services, the prospects for aircraft-satellite communications look particularly bright in the booming Asia-Pacific air travel market. Around the region, aircraft are flying full and carriers are better able to afford the roughly US $ 500,000 Cost of equipping each airliner. But many carriers will order the equipment only for new aircraft rather than take existing ones out of service for lengthy modifications.
    Satellite communications will also help improve flight efficiency. A system of voice and data links is already operating between aircraft and their operations centres which, for example, enables crews to obtain permission to change altitudes at the optimum time for fuel efficiency.
    Crews can also call ahead for maintenance; an aircraft with a vibrating engine, for example, can be met on arrival by engineers who have already obtained computerized data on its behaviour. These communications, however, like most existing airborne telephones, mostly use radio links; in the future they, too, will be transferred to the satellite system.
    The instant nature of the air-to-ground communications will also improve navigation, by allowing continuous reporting of aircraft positions. Indeed, a study by the International Civil Aviation Organization indicates that the technology could provide benefits worth between US $ 5 ～ 6 billion annually in fuel efficiency, faster repair turn-arounds and improved traffic flows through airports.
    For the fidgety (坐立不安的) executive, meanwhile, air travel need no longer mean a communications black-out. And some airlines are already developing data terminals that will permit passengers to change hotel and car-hire reservations, or contact their banks and brokers.
Ground stations have been set up in order to avoid the problem of double time lag.
选项 A、Y
B、N
C、NG
答案A
解析
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