Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
1998-11-17
2001-07-03
Maung, Nay (Department: 2744)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S502000, C455S067700, C455S067700, C375S260000, C370S208000, C370S478000
Reexamination Certificate
active
06256508
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a simultaneous broadcasting system of broadcasting radio waves from a wide area broadcasting and local area broadcastings simultaneously, and transmitter and receivers for transmitting and receiving radio wave based on the simultaneous broadcasting system.
2. Description of the Prior Art
FIG. 1
is a diagram showing broadcasting radio wave zones as broadcasting areas transmitted from each broadcasting stations. The broadcasting area are overlapped as designated by slant lines. In
FIG.1
, the reference character A designates a broadcasting station for broadcasting over wide area, and the reference characters B, C, D, E, F, and G denote local broadcasting stations for local areas. The reference characters a, b, c, d, e, f, and g indicate radio wave broadcasting zones of radio waves transmitted from the wide area broadcasting station and the local area broadcasting stations. These broadcasting radio wave zones are overlapped to each other in adjacent areas designated by the slant lines shown in FIG.
1
.
FIG. 2
is a diagram showing the possible allocation map in a conventional broadcasting frequency bandwidth for the wide area broadcasting station A and the local area broadcasting stations B, C, D, E, F, and G. In
FIG. 2
, the reference character fA designates the broadcasting frequency bandwidth of 6 MHz of each channel allocated for the wide area broadcasting station A. Each of the reference characters fB, fC, . . . , and fG denotes the broadcasting frequency bandwidth of 6 MHz of each channel allocated for each of the local area broadcasting stations B, C, . . . , and G.
Next, a description will be given of the conventional broadcasting system.
The wide area broadcasting station A uses the broadcasting frequency bandwidth fA and transmits a wide area broadcasting program into the radio wave zone a. The local area broadcasting stations B, C, D, E, F, and G receive the wide area broadcasting program from the wide area broadcasting station A through video information transmission service line, for example, and transmits local area broadcasting programs in addition to the received wide area broadcasting programs into each of the broadcasting radio wave zones b, c, d, e, f, and g by using each of the broadcasting frequency bandwidths fB, fC, fD, fE, fF, and fG, respectively.
In order to avoid occurrence of radio wave interference from adjacent areas, namely, in order to eliminate ghost caused when the wide area broadcasting station A and the local area broadcasting stations B to G transmit programs simultaneously, as shown in
FIG. 2
, it is required to allocate a different 6 MHz frequency bandwidth per broadcasting station. The case shown in
FIG. 2
requires the wide broadcasting frequency bandwidth of 42 MHz.
FIG. 3
is a diagram showing the allocation map in a conventional frequency bandwidth based on the method Orthogonal Frequency Division Multiplexing (OFDM). The OFDM method has been used for Digital Audio Broadcasting (DAB) service in Europe from 1996 and also adopted as a standard method of a next generation television broadcasting service by using terrestrial radio wave (VHF/UHF). This standard method is a digital modulation method to be also used for digital television broadcasting service in Japan.
The OFDM method is a multi carrier transmission method in which broadcasting signals to be transmitted are divided into a plurality of carrier waves. For example, as shown in
FIG. 3
, it is widely known that this OFDM method prevents occurrence of radio wave interference such as ghost so long as a same broadcasting program is transmitted even if the wide area broadcasting and local area broadcasting use the same channel of 6 MHz bandwidth.
On the other hand, there is a requirement to broadcast different particular programs such as particular local area commercial, election information, and the like in each local broadcasting station in addition to programs for the wide area broadcasting. When local area broadcasting stations use one channel simultaneously for different particular programs based on the OFDM method, broadcasting radio wave interference occurs in adjacent areas designated by the slant lines shown in
FIG. 1
because the radio frequency spectrum of broadcasting signals transmitted from each local area broadcasting station is different to each other.
Because the conventional simultaneous broadcasting system has the configuration described above, it must be required to different frequency bandwidth for each broadcasting station, as shown in
FIG. 2
, in order to avoid occurrence of radio frequency interference. This causes to require a wide frequency bandwidth as a whole for the wide area broadcasting station and the local area broadcasting stations.
Furthermore, when the wide area broadcasting station broadcasts a wide area program and the local area broadcasting stations broadcast particular local area programs by using one broadcasting channel simultaneously, the radio frequency interference occurs in adjacent areas because broadcasting programs are different to each other.
There is a prior art technique “Japanese laid-open publication number JP-A-7/154350, Multi-broadcasting system and device therefor” relating to the present invention. This prior art technique can not broadcast different sub broadcastings in local area broadcasting stations since sub-broadcasting programs are transmitted only when local area information added to sub-broadcasting information multiplied with wide area broadcasting information by the broadcasting station as a transmitter is equal to particular local area information set in receivers.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is, with due consideration to the drawbacks of the conventional technique, to provide a simultaneous broadcasting system, a broadcasting transmitter, and a broadcasting receiver therefor. Further, the present invention is capable of avoiding occurrence of interference of broadcasting radio wave signals in adjacent areas even if each of broadcasting stations broadcasts different programs for wide area broadcasting and local area broadcastings by using a same broadcasting channel.
In accordance with a preferred embodiment of the present invention, a simultaneous broadcasting system in which a plurality of broadcasting stations broadcast a same program as a wide area broadcasting and each of said broadcasting stations broadcasts a different program as a local area broadcasting by using one broadcasting channel, simultaneously, comprises dividing a frequency bandwidth of said broadcasting channel into a first frequency bandwidth for said wide area broadcasting and a second frequency bandwidth for said local area broadcasting, and modulating signals of said same program for said wide area broadcasting in said first frequency bandwidth based on an Orthogonal Frequency Division Multiplex (OFDM) method, and signals of said different program in said second frequency bandwidth based on a Spread Spectrum (SS) method by using different spreading codes corresponding to said local area broadcasting stations.
In the simultaneous broadcasting system as another preferred embodiment of the present invention, said second frequency bandwidth for said local area broadcasting is used for data transmission transmitted from each of said plurality of broadcasting stations.
In the simultaneous broadcasting system as another preferred embodiment of the present invention, a different spreading code is allocated for each user contracted with each station of said plurality of broadcasting stations, and said second frequency bandwidth for said local area broadcasting is used for a down link in a two-way communication between said each broadcasting and said each user.
In the simultaneous broadcasting system as another preferred embodiment of the present invention, a broadcasting area of each of at least one or more said broadcasting stations is divided into a plurality of sectors, and each broadcasting station broadcast
Abe Masanori
Koyama Atsumi
Mori Masashi
Nakagawa Masao
Oguchi Masashi
Burns Doane , Swecker, Mathis LLP
Davis Temica M.
Maung Nay
Mitsubishi Denki & Kabushiki Kaisha
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