JPH027735A - 2-wire full duplex communication system - Google Patents

Abstract

PURPOSE:To attain full duplex communication where transmission and reception use the same band by adopting the orthogonal modulation system for the 2-wire data transmission. CONSTITUTION:The Y axis of a transmission signal is modulated when the reception signal is modulated to its X axis and the X axis of the transmission signal is modulated when the Y axis of the reception signal is modulated and the result is sent to an opposite party by utilizing the property that the signals of X and Y axes of orthogonal modulation are not interfered with each other in the base band transmission using a local cable or the modem transmission using a 2-wire public network. That is, a pilot signal is sent mutually to lock the modulation timing in the transmission and reception, thereby sending phase information. Since the transmission/reception signal is extracted without interference, the interference of the transmission/reception is avoided by using the same band.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a total
The present invention relates to a two-wire full-duplex communication system that enables heavy data transmission.

[Conventional technology]

Traditionally, full-duplex data transmission over a two-wire public network is performed using a frequency band division method or an echo canceller method. Incidentally, as the data speed increases, a wider band becomes necessary, and the echo canceller method has become mainstream for data transmission of 4800 b/s or more. As such conventional technology, data of 9600 b/s,
CCITT as full duplex communication via two-wire public network
There is Rec, V, 32.

[Problem to be solved by the invention]

Data transmission using the conventional echo canceller method described above has the drawbacks of being technically difficult and requiring a large circuit scale. Another disadvantage is that as data speeds increase, a wide band is required.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate such drawbacks and provide a full-duplex communication system in which transmission and reception do not interfere with each other while using the same band.

[Means to solve the problem]

The present invention is a ZvA full-duplex communication system using an orthogonal modulation method that performs full-duplex data transmission with the other party, in which the received signal from the other party is modulated in the X-axis direction of the orthogonal modulation. When the signal is modulated on the Y axis, the signal to be sent to the other party is modulated on the Y axis, and when the received signal is on the Y axis, the signal is modulated on the Utilizes the property that axial signals do not interfere with each other, and transmits and
By matching the reception modulation timing, the transmission and reception signals can be extracted without interference.

〔Example〕

Next, an embodiment of the present invention will be described using, as an example, a case in which full-duplex data transmission at 9600 b/s is carried out through a two-wire public network. This embodiment is used alone or in combination with a conventional echo canceller scheme for two-wire full-duplex data transmission.

When transmitting and receiving data with the other party, the transmitted modulated signal is modulated every 1/2400 seconds in the X-axis direction of quadrature modulation, and is modulated every 1/2400 seconds in the Y-axis direction with respect to the modulation period, that is, the baud rate interval T. It has a delay of T/2 (1/4800 seconds) in the modulation of the X axis and is modulated every <1/2400 seconds.

Using this modulated signal, the other party alternately transmits a signal modulated in the X-axis direction and a signal modulated in the Y-axis direction of quadrature modulation. When such a signal is received, the received signal x (t) is x (t) = Σ C1・ψ
, (t). Note that g (t) is the impulse response of the Nyquist filter, fo is the carrier frequency, and C0
is a function that gives data points.

Here, x (t) = Σ C,・g (t - mT)
A signal represented by CO32πfot and sin 2πfot are received, but when the received signal is modulated in the X-axis direction, the transmitted signal is modulated in the Y-axis direction, and when the received signal is in the Y-axis direction, the transmitted signal is is modulated on the X-axis and sent to the other party.

At this time, if the component obtained by shifting the component ψ1(t) of the transmitted signal by T/2 compared to the received signal is ψ,' (t), then the following equation is obtained.

By transmitting such signals to the other party, mutual interference can be prevented. Note that in order to match the modulation timings of transmission and reception at this time as described above, timing information is mutually sent using pilot signals.

As described above, according to this embodiment, the property that the signals in the X-axis and Y-axis directions of quadrature modulation do not interfere with each other is achieved in baseband transmission using a modem using a 2'g public network or a local cable. By using this and matching the modulation timing of transmission and reception, that is, by sending pilot signals to each other in order to lock the modulation timing between transmission and reception,
By transmitting phase information, transmitted and received signals can be extracted without interference.

〔Effect of the invention〕

As explained above, the present invention has the effect of enabling full-duplex communication using the same band for transmission and reception by introducing an orthogonal modulation method to two-wire data transmission.

Claims (1)

[Claims] (1) A two-wire full-duplex communication method using orthogonal modulation that performs full-duplex data transmission with the other party, in which the received signal from the other party is modulated in the X-axis direction of the orthogonal modulation. When there is a remote control, the signal to be sent to the other party is modulated on the Y axis, and
When the received signal is on the Y axis, the transmitted signal is modulated on the A two-wire full-duplex communication system characterized by the ability to extract transmitted and received signals without interference by combining them.