satellite modem technologies

There are several areas for Satellite industries ; satellite manufacturing, launch vehicle to lift-up satellite, satellite service to use satellite, and ground equipments to handle transferring data. At the early phase of satellite industries satellite and launch vehicle manufacturing were concentrated due to military and government use, however, satellite service and ground equipments have been important with dramatic growth of satellite applications and the increasing usage of broadband service. Satellite service has been commercially expanded owing to its advantages of large coverage and the huge amount of data transport. Early mission of reconnaissnce and observation has now being shifted to GPS applications, voice communication and broadcast and finally to mobile communication, data transfer, and internet. Wide spread of internet use has changed communication environments from voice transfer to data transfer which needs the usage of satellite. Dial-up modem was enough for text-oriented service for early internet users, however, multimedia service for audio and video data transfer has become necessary with wide use of internet. To provide these services, xDSL using telephone line and cable modem using cable network has been used and fast expanded. However, these methods have not only advantages of high speed data rate and two way data transport but also disadvantages of necessity for installing network, restriction of service area, and difficulties for data broadcast. Early satellite internet service used satellite for down-link data transfer and general dial-up modem for up-link data transfer, but it has been changing to use satellite for both up-link and down-link data transfer. There has realized a method to use satellite as the gateway over LAN network for the specific area. Therefore, it has become necessary to develop various service contents and relating ground equipments to realize multiple services using satellite. Market trend of satellite industries, satellite service areas, various ground equipments, and broadband service market are described in the chapter 2, functions of the satellite modem, development trend, technologies, and future technologies

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