I. Broadcasting service for cellular phone in Japan, past, present and future.
For the mobile carrier, the two way communication to an individual cellular user has been assumed to be a basis for their business activities. This basic idea has not changed though data in addition to the voice becomes the main service. However, the content with large volume of data, such as movies and drama by the two way communication for an individual user becomes big burden for the mobile carrier even if the cellular phone user bears expensive communication fee. This doesn't change in Super the Third generation (3.5 generations) and the 4th generation of CDMA.
Therefore, it is preferable that the movies and the musical programs, etc. use the transmission simultaneously (broadcasting). As a result, the service can be offered to the cellular phone user at a low price and the mobile carrier can use a valuable frequency band more effectively.
Considering these advantages, it can be said that the mobile carrier will add the broadcasting service as an important part in their cellular service in the future.
As for broadcasting service for the cellular phone, it can be divided into the three categories. The one that has already been executed, the one that execution in the near future is expected, the one examined as possibility in the future.
The one that has already been executed
1. Analog TV
The program is broadcast by using the TV electric wave from the TV tower, received with the TV tuner built into the cellular phone, and displayed on a cellular phone. The program is the same content as analog terrestrial TV, and has the weak point to which the reception is not steady.
2. Broadcasting service by mobile carrier using the second generation technology
Use of second generation of cellular phone technology, the frequency band allocated to the cellular phone entrepreneur is divided into the frequency for the two way communication and the frequency for the transmission simultaneously.
The mobile carrier broadcasts their programs by using the frequency for the transmission simultaneously. The electric wave of the cellular phone is used, received with the antenna of the cellular phone and programs displayed on the cellular phone. The TV tuner is unnecessary. Program is transmitted by using the frequency for the transmission differing in each base station. (Cell Broadcasting)
The one that execution in the near future is expected
1. Digital television
The TV program is broadcast by using the TV electric wave from the TV tower, received with the TV tuner built into the cellular phone and displayed on the cellular phone. The program is the same content as digital terrestrial TV. The receptions are steadier than analog TV.
2. Broadcasting service by mobile carrier
Super the third generation technology is used. The frequency band allocated to the cellular phone entrepreneur shall be divided into the frequency for the two way communication and the frequency for the transmission simultaneously, and common one frequency to each base station is used both for transmission simultaneously and for two way communication.
When mobile carriers use a common one frequency to each base station, it is technically possible to divide one frequency into many slots and use them for two way communication and transmission simultaneously in the same frequency. However, to a large amount of data transmissions such as movies and the musical programs, a lot of frequencies shall be used at the same timing. The frequency used to transmit simultaneously (broadcasting) will most possibly be allocated to a specific band and used only for broadcasting.
The one examined as possibility in the future
1. Broadcasting service by mobile carrier
The broadcasting service by the cellular phone entrepreneur using super the third generation, mobile carriers seem finalized technological examination and are making schedule in execution preparation.
The frequency band allocated to the cellular phone entrepreneur shall be divided into the frequency for the two way communication and the frequency for the transmission simultaneously, and common one frequency to each base station is used both for transmission simultaneously and for two way communication.
2. Mobile broadcasting using satellite
The broadcasting service for a mobile special receiver from satellite has started already. While the service for cellular phone is assumed as the possibility in the future.
3. Transmission to CDMA cellular phone by cellular phone broadcasting service entrepreneur
Firstly, the frequency assignment for CDMA cellular phone broadcaster shall be granted by the authority which seems very difficult in Japan. The frequency band of CDMA broadcaster is used only for broadcasting. CDMA cellular phone broadcaster transmits programs to the CDMA cellular phone.
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