Multiplex communications – Communication over free space – Repeater
Reexamination Certificate
2000-09-18
2004-09-14
Duong, Frank (Department: 2666)
Multiplex communications
Communication over free space
Repeater
C370S335000, C370S342000, C370S441000
Reexamination Certificate
active
06791955
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-337403, filed Nov. 29, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to code division multiplex (CDM) transmission systems and receivers used in such systems, and more particularly, the invention relates to a technology for synchronization and recovery of a plurality of multiplexed transmission data streams.
As widely known, in the code division multiplex transmission technology, a plurality of transmission data streams are spread frequency modulated with a spread code unique to each data stream, and those modulated signals are transmitted after multiplexed over the same carrier frequency. In such a code division multiplex transmission technique, signals modulated only by a specific spread code known to the receiving side are transmitted after being multiplexed over the same carrier frequency as that used for other spread frequency modulated signals, so that the synchronization of the spread code on the receiving side becomes easy.
In general, transmission data streams multiplexed with a spread code are subject to error correction coding and interleaving. The values of such parameters as the coding rate for error correction and interleaving length can be changed in each transmission data stream.
The convolution code and block code are used for error correction; convolution interleaving and block interleaving are used for interleaving. If the transmitting side sets selectively a punctured code for convolution coding, block code, convolution interleaving and block interleaving, the receiving side needs to synchronize the blocks and delay depth. For this purpose, synchronization words are inserted in each transmission data stream upon transmission and the data streams are synchronized by detecting these synchronization words at receiving terminals.
BRIEF SUMMARY OF THE INVENTION
Although it is possible to change parameter values such as the coding rate for error correction and the interleaving length for each transmission data stream in the code division multiplex transmission mode, there is a problem that the receiving side has to continue a complex process of changing parameter values until it succeeds in receiving correct signals if the receiving side does not know the parameter values set for each data stream beforehand. As a result, it takes time to get correct signals on the receiving side.
Further, as described above, synchronization words should be inserted in the data stream for the synchronization of error correction codes and interleaving. Since different synchronization words are inserted in each transmission data stream, the detection of the synchronization word must be repeated each time the current transmission data stream is switched to another data stream. Then, a significant amount of time is consumed in this switching process.
Also in the code division multiplex transmission mode, the receiving terminal receives only one transmission data stream at a time, neglecting the other data streams. Therefore, if common information should be received in all the receiving terminals, all the transmission data streams have to carry the same information.
The present invention has been provided to solve above described problems. Its primary object is, therefore, to provide a system for code division multiplex transmission that allows the receiving side to receive correct data from an arbitrary transmission data stream in a short time even if the receiving side does not know the parameter values set for data reception in each transmission data stream.
The second object of the present invention is to provide a system for code division multiplex transmission that does not need to repeat the detection of synchronization words even if the current transmission data stream is switched to another when each transmission data stream is subject to error correction coding and interleaving and the insertion of synchronization words are necessary for parameter synchronization.
The third object of the present invention is to provide a system for code division multiplex transmission that allows all or specific receiving terminals to receive common information without incorporating the common information in all the transmission data streams even if the receiving terminals are receiving different transmission data streams.
The code division multiplex transmission system according to the present invention has the following characteristic configurations to solve the above problems.
(1) The system for transporting the spread frequency modulated signals of a plurality of transmission data streams by code division multiplexing, comprising:
a synchronization signal processing unit that generates spread frequency modulated signals as synchronization signals by time division multiplexing the signals for synchronizing spread code prepared for an easy synchronization of spread code on the receiving side and the information related to the structure or synchronization of each of the plurality of transmission data streams and by a spread frequency modulation using a spread code known to the receiving side; and
a code division multiplexing unit that generates transmission signals by code division multiplexing the spread frequency modulated signals as synchronization signals obtained in the synchronization signal processing unit over the spread frequency modulated signals of each of the plurality of transmission data streams.
(2) The code division multiplex transmission system based on the configuration of (1), wherein, the synchronization signal processing unit comprises:
a time division multiplexing unit that time division multiplexes the signals for synchronizing spread code prepared for an easy synchronization of spread code on the receiving side and the information related to the structure or synchronization of each of the plurality of transmission data streams; and
a spread frequency modulating unit that generates spread frequency modulated signals as synchronization signals by spread frequency modulating the time division multiplexed signals obtained in the time division multiplexing unit using a spread code known to the receiving side.
(3) The code division multiplex transmission system based on the configuration of (1), wherein, the synchronization signal processing unit comprises:
a first spread frequency modulating unit that spread frequency modulates the signals for synchronizing spread code prepared for an easy synchronization of spread code on the receiving side and the information related to the synchronization of each of a plurality of transmission data streams by the use of a spread code known to the receiving side;
a second spread frequency modulating unit that spread frequency modulates the information related to the structure of each of a plurality of transmission data streams by the use of a spread code known to the receiving side; and
a time division multiplexing unit that time division multiplexes the spread frequency modulated signals obtained in the first and second spread frequency modulating units.
(4) The code division multiplex transmission system based on the configuration of (1), wherein, the information related to the structure of the transmission data streams includes at least the parameter information about the coding rate of the error correction code for each of the plurality of transmission data streams.
(5) The code division multiplex transmission system based on the configuration of (1), wherein, the information related to the structure of the transmission data streams includes at least the parameter information about the interleave length for each of the plurality of transmission data streams.
(6) The code division multiplex transmission system based on the configuration of (1), wherein, the information related to the synchronization of the transmission data streams includes at least synchronization words required for the synchroni
Hirakawa Shuji
Kikuchi Hideo
Serizawa Mutsumu
Watanabe Eiichi
Yokoi Tokihiko
Duong Frank
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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