Multiplex communications – Generalized orthogonal or special mathematical techniques – Quadrature carriers
Reexamination Certificate
1997-08-22
2001-10-02
Nguyen, Chau (Department: 2663)
Multiplex communications
Generalized orthogonal or special mathematical techniques
Quadrature carriers
C370S527000, C370S537000, C375S222000
Reexamination Certificate
active
06298036
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transmission system wherein information carried by at least one analog signal and a data signal are multiplexed and transmitted. The present invention relates, in particular, to a multiplex transmission system wherein information carried by at least one analog signal including, for example, a voice signal and facsimile signal is multiplexed with a data signal and transmitted through an analog transmission (telephone) line of two wires or four wires.
2. Description of the Related Art
Recently, various types of signals including telephone (voice) signals, facsimile signals, data signals, and image data signals are multiplexed and transmitted in digital transmission systems. However, analog transmission lines are still mainly used in the presently equipped networks except basic transmission lines since it takes a long time for the digital transmission lines to prevail, and the running costs of the digital transmission lines are relatively high. Therefore, data signals are modulated by modems and transmitted through analog transmission lines, and then analog voice signals cannot be transmitted through the same analog transmission line as the analog transmission line through which the data signals modulated by modems are transmitted at the same time. Thus, development of a technique whereby various types of signals including telephone (voice) signals, facsimile signals, data signals, and image data signals can be multiplexed and transmitted in an analog transmission line, is required.
FIG. 1
is a diagram illustrating a transmission system connected between a main office
1000
and a branch office
1200
, between the main office
1000
and a plurality of sub-branch offices
116
-
1
to
116
-n, and between the branch office
1200
and a plurality of other sub-branch offices
116
-
1
′ to
116
-n′. The main office
1000
and the branch office
1200
are connected by a digital transmission line
1400
through which digital multiplex signals are transmitted, where telephone (voice) signals, facsimile signals, data signals, and image data signals are multiplexed into the respective multiplex signals. However, taking the high running cost of the digital transmission lines into consideration, the main office
1000
and the plurality of subbranch offices
116
-
1
′ to
116
-n are connected by a plurality of analog transmission lines
121
-
1
to
121
-n and
122
-
1
to
122
-n, where a plurality of data signals are modulated by modems
120
-
1
to
120
-n and transmitted through the analog transmission lines
121
-
1
to
121
-n, and the analog voice signals are transmitted through the analog transmission lines
122
-
1
to
122
-n. Similarly, the branch office
1200
and the plurality of sub-branch offices
116
-
1
′ to
116
-n′ are connected by a plurality of analog transmission lines
121
-
1
′ to
121
-n′ and
122
-
1
′ to
122
-n′, where a plurality of data signals are modulated by modems
120
-
1
′ to
120
-n′ and transmitted through the analog transmission lines
121
-
1
′ to
121
-n′, and the analog voice signals are transmitted through the analog transmission lines
122
-
1
′ to
122
-n′. Since transmission of data signals and transmission of analog signals are often carried out concurrently, the analog transmission lines
121
-
1
to
121
-n and
122
-
1
to
122
-n are separately used for transmitting the data signals and for transmitting the analog voice signals, respectively, between the main office
1000
and the plurality of sub-branch offices
116
-
1
to
116
-n. Similarly, the analog transmission lines
1211
′ to
121
-n′ and
122
-
1
′ to
122
-n′ are separately used for transmitting the data signals and for transmitting the analog voice signals, respectively, between the branch office
1200
and the plurality of sub-branch offices
116
-
1
′ to
116
-n′. The transmission system of
FIG. 1
has a drawback that a great number of transmission lines must be subscribed to, and therefore, the cost for the subscription and equipment for the great number of transmission lines is great.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a multiplex transmission system wherein information carried by at least one analog signal and a data signal are multiplexed and transmitted through a single analog transmission line.
A second object of the present invention is to provide a multiplex transmission system wherein information carried by more than one analog signal is multiplexed and transmitted through a single analog transmission line.
According to the first aspect of the present invention, there is provided a transmission system comprises a transmitter, a receiver, and an analog transmission line; the transmitter including a data signal point generation unit for receiving a serial digital data signal, and generating a first vector base band signal in a vector signal space, based on a block series of samples of the received serial digital data signal, wherein the generated data signal point is one of a plurality of predetermined data signal points in the vector signal space, a base band transformation unit for receiving an analog voice or facsimile signal in the form of a passband signal, and transforming the analog voice or facsimile signal into a second vector base band signal; a vector signal superimposing unit for superimposing a plurality of vector components of the second vector base band signal on a plurality of vector components of the first vector base band signal, component by component to generate a superimposed vector base band signal, and a modulation unit for modulating the superimposed vector base band signal to generate an analog modulated signal to be transmitted through the analog transmission line; the receiver including a demodulator unit for receiving the analog modulated signal transmitted through the analog transmission line, and demodulating the analog modulated signal to regenerate the superimposed vector base band signal, a decision unit for receiving the regenerated superimposed vector base band signal, and determining as to which one of the plurality of predetermined data signal points in the vector signal space the regenerated superimposed vector base band signal corresponds (is nearest), to regenerate the first vector base band signal, a vector signal subtracter unit for receiving the regenerated superimposed vector base band signal and the regenerated first vector base band signal, and subtracting a plurality of vector components of the first vector base band signal from a plurality of vector components of the superimposed vector base band signal, component by component, to regenerate the respective vector components of the second base band signal, a code transformation unit for receiving the first vector base band signal, and transforming the first vector base band signal to regenerate the serial digital data signal, and a passband transformation unit for receiving the regenerated second base band signal, and transforming the regenerated second base band signal to regenerate the analog voice or facsimile signal in the form of the passband signal.
According to all the aspects and embodiments of the present invention, the analog signal inputted into the transmitter may be any kind of analog signal, and may not be a passband signal. When the analog signal input into the transmitter is not a passband signal, the base band transformation unit transforms the analog signal to the base band signal, and the passband transformation unit in the receiver transforms the regenerated base band signal to the analog signal which is inputted into the transmitter.
According to a second aspect of the present invention, in addition to the system of the first aspect of the present invention, the demodulator unit may comprise an equalizer unit for equalizing the analog modulated signal after demodulating to regenerate the superimpos
Kaku Takashi
Kawada Noboru
Okita Ryoji
Fujitsu Limited
Helfgott & Karas P.C.
Nguyen Chau
Nguyen Phuongchau Ba
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