Explain about NMT & NTT Systems
2. Explain about NMT & NTT Systems.
NTT:
Nippon Telegraph and Telephone Corporation (NTT) developed an 800-MHz land mobile telephone system and put it into service in the Tokyo area in 1979. The general system operation is similar to the AMPS system. It accesses approximately 40,000 subscribers in 500 cities. It covers 75 percent of all Japanese cities, 25 percent of inhabitable areas, and 60 percent of the population. In Japan, 9 automobile switching centers (ASCs), 51 mobile control stations (MCSs), 465 mobile base stations (MBSs), and 39,000 mobile subscriber stations (MSSs) were in operation as of February 1985.
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| Japanese mobile telephone service network configuration |
The Japanese mobile telephone service network configuration is shown in Fig.2. In the metropolitan Tokyo area, about 30,000 subscribers are being served. The 1985 system operated over a spectrum of 30 MHz. The total number of channels was 600, and the channel bandwidth was 25 kHz. This system comprised an automobile switching centre (ASC), a mobile control station (MCS), a mobile base station (MBS), and a mobile subscriber station (MSS). At present there is no competitive situation set up by the government. However, the Japanese Ministry of Post and Telecommunication (MFT) is considering providing a dual competitive situation similar to that in the United States.
NMT:
Nordic System: This system was built mostly by Scandinavian countries (Denmark, Norway, Sweden, and Finland) in cooperation with Saudi Arabia and Spain and is called the NMT network. It is currently a 450-MHz system. But an 800-MHz System will be implemented soon since the frequency transparent concept as the AURORA 800 system is used to convert the 450-MHz system to the 800-MHz System. The total bandwidth is 10 MHz, which has 200 channels with a bandwidth of 25 kHz per channel. This system does have hand off and roaming capabilities. It also uses repeaters to increase the coverage in a low traffic area. The total number of subscribers is around 100,000.
