JPH0131736B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] Digital signals transmitted on the station side and the subscriber side are converted into burst signals by time division, and the burst signals are transmitted between the station side and the subscriber side using a two-wire transmission line. Regarding the burst transmission method in which transmission and reception are performed alternately between The purpose is to provide a burst transmission method that can perform burst transmission at the required transmission speed, while reducing the size, power consumption, and cost of subscriber equipment. In this burst transmission method, burst signals having a predetermined baud rate are transmitted and received between the two sides in a time-division manner, and when each burst signal is received, the burst signal is identified using a clock extracted from the received burst signal. For the burst signal sent from the subscriber side to the subscriber side, a low baud rate is selected so that the echo component caused by the influence of the transmission path ends between the clocks. For the burst signal sent to the subscriber side, a high baud rate is selected so that the echo component is applied to the clock, and a bridged tap equalizer is provided at the station side to remove the echo component. A burst transmission method characterized by obtaining a predetermined transmission speed as a whole without providing a bridged tap equalizer on the side.

[Industrial application field]

In the present invention, the digital signals transmitted on the station side and the subscriber side are converted into burst signals by time division, and the burst signals are transmitted using a two-wire transmission line.
The present invention relates to a burst transmission method in which transmission and reception are performed alternately between a station side and a subscriber, and particularly relates to a burst transmission method in which subscriber side equipment is miniaturized.

In recent years, in the field of communications, with the development of communication technology, there has been a demand for various devices to be made smaller and to have the same functionality, and the burst transmission method is no exception. There is a demand for devices to be smaller and to have comparable functionality.

[Conventional technology]

A conventional burst transmission method will be explained using FIGS. 1 to 3.

FIG. 1 is a diagram showing an example of a configuration of a conventional burst transmission method. In the figure, EX is the station side, A is the subscriber side, 1 and 7 are identification circuits, 2 and 6 are bridged tap equalizers, 3 and 8 are timing circuits, 4 and 5b are √AGC equalizers, 4a and 5
a is a transmission circuit, a and c are transmission data input terminals (hereinafter referred to as input terminals), b and d are reception data output terminals (hereinafter referred to as output terminals), and L is a transmission line.

FIG. 2 is an explanatory diagram of the operation of FIG. 1. Figure a
b is a transmission/reception burst signal on the station side, b is a transmission/reception burst signal on the subscriber side, S in the figure is a transmission burst signal, and R is a reception burst signal. Also,
T _BO and T _BD indicate the burst length of the burst signal.

FIG. 3 is a diagram showing one pulse of the received burst signal. In the figure, E indicates an echo component, and _T1 to _T7 indicate output clocks of the timing circuit.

First, the operation when the station side EX and subscriber A send out a burst signal will be explained. The transmitter circuit 4a of the station-side EX transmits the transmission data at the baud rate f from the input terminal a to the transmission line L as a burst signal in the form of S shown in FIG. 2a. The burst signal sent from the office side EX is received by the subscriber side A in the form R shown in FIG. 2b, that is, as a burst signal attenuated by the transmission line L. When the transmitting circuit 5 in the subscriber side A receives the burst signal from the station side EX, the transmitting circuit 5 at the baud rate f from the input terminal c is converted into a burst signal in the form of S shown in FIG. 2b. Send to transmission path L. Thereafter, this operation is repeated alternately on the station side and the subscriber side, and burst transmission is performed.

When looking at one pulse of the burst signal received at the station side EX and the subscriber side A mentioned above, it has an echo component E as shown in FIG. This is the first
Since the transmission line L in the figure has a bridged tap,
This is because the resulting echo component is added to each pulse of the burst signal. For this reason, the station side EX and the subscriber side A are provided with bridged tap equalizers 2 and 6, respectively, for removing this echo component. This is done to prevent the echo component from being identified when the identification circuit identifies the burst signal. The structure of this known bridged tap equalizer is shown in FIG.
The bridged tap equalizer reduces the echo components added to the burst signal due to the influence of the transmission path with taps to 1
The echo component is removed from the burst signal by creating an echo component by creating a shift from the previous burst signal using a delay line with taps and weighting it with each tap system.

Here, the operation after the station side EX and the subscriber side A receive the burst signal will be explained using the subscriber side A as an example. When the burst signal sent from the station-side EX is received by the √AGC equalizer 5b of subscriber A, the echo component of this burst signal is removed by the bridged tap equalizer 6, and then sent to the identification circuit 7. Output. Moreover, in the timing circuit 8,
A timing component is extracted from the burst signal and outputted to the identification circuit 7 as a baud rate clock. In the identification circuit 7, the signal obtained by equalizing the burst signal by the bridged tap equalizer 6 is processed according to the clock of the baud rate f from the timing circuit 8.
It is identified and output to output terminal d. That is, the identification circuit 7 identifies the signal from the bridged tap equalizer 6 (the signal obtained by removing the echo component E from one pulse of the burst signal shown in FIG. 3) at the identification points T ₁ to T ₇ shown in FIG. do.

In this way, in the conventional burst transmission system, a bridged tap equalizer is installed on the station side and the subscriber side in order to remove the echo component added to the received burst signal, and when the identification circuit is used for identification,
The echo component was not identified.

[Problem to be solved by the invention]

However, such conventional burst transmission methods have the following drawbacks. In other words, bridged tap equalizers were installed on each of the station and subscriber sides in order to remove echo components caused by bridged taps in the transmission path, so the configurations of the equipment on the station and subscriber sides became larger. The disadvantages are that it consumes a lot of power and is expensive.

The present invention eliminates such conventional drawbacks.
By eliminating the bridged tap equalizer on the subscriber side without sacrificing the conventional equalization function, the subscriber equipment can be made smaller, lower in power consumption, and lower in price.
An object of the present invention is to provide a burst transmission method that can perform burst transmission at a required transmission rate.

[Means to solve the problem]

In the present invention, in the burst signal sent from the station side EX to the subscriber side A, the echo component generated due to the influence of the transmission line L ends between each clock extracted from the burst signal received at the subscriber side A. Select a low baud rate that will On the other hand, for the burst signal sent from the subscriber side A to the office side A, a baud rate higher than the lower baud rate and at a level that provides a predetermined transmission speed as a whole is selected.

Further, a bridged tap equalizer 10 for removing echo components is provided on the station side EX. On the subscriber side A, no bridged tap equalizer is provided since the echo component is not identified by the clock.

[Effect]

As in the above means, by setting the baud rate of the burst signal sent from the station side EX to be lower than the baud rate of the burst signal sent from the subscriber side A so that the echo component ends between the timing components, the timing can be improved. The signal no longer has discernible echo components. This eliminates the need for a bridged tap equalizer on the subscriber side A.

〔Example〕

The burst transmission method of the present invention will be explained using FIGS. 4 to 6.

FIG. 4 is a diagram showing a configuration example of the burst transmission method of the present invention. In the figure, 9 and 14 are identification circuits, 10 is a bridged tap equalizer, 11b and 13b are √AGC equalizers, and 11a and 13a are
is a transmitting circuit, and 12 and 15 are timing circuits.

FIG. 5 is an explanatory diagram of the operation of FIG. 4, and FIG. 6 is a diagram showing one pulse of the received burst signal.

First, the operation when transmitting a burst signal from the station-side EX and subscriber A will be explained. The transmitting circuit 11 of the station-side EX transmits the transmission data at the baud rate f _B from the input terminal a to the transmission line L as a burst signal in the form of S shown in FIG. 5a. The burst signal sent from the station EX is received by the subscriber A in the form R shown in FIG. 5b, that is, as a burst signal attenuated by the transmission line L. And subscriber A,
When a burst signal is received from the station side EX, the transmission data at baud rate f _A from input terminal C is sent to the fifth terminal.
It is sent to the transmission line L as a burst signal in the shape of S shown in FIG. b. Thereafter, this operation is repeated alternately on the station side and the subscriber side to perform burst transmission.
Here, the relationship between the baud rates f _B and f _A of the sampling clocks used on the station side EX and the subscriber side A is f _A > f _B. However, f _A > f _B such that the echo component added to the burst signal is not sampled
There must be a relationship between In other words, the station side EX
The burst signal sent out from the terminal is sent out as a burst signal having a burst length _TBD as shown in FIG. Furthermore, the burst signal sent from the subscriber side A has a burst length T _BO as shown in FIG.
It is sent as a burst signal with . here,
The echo component of one pulse of the burst signal received by the station side EX and the subscriber side A is the same regardless of the transmission speed.

Next, the operations after receiving the burst signal on the station side EX and the subscriber side A will be explained. The pulse peak value of the burst signal sent from the station EX is equalized by the √AGC equalizer 13b of subscriber A, and this burst signal is output to the identification circuit 14. Also,
The timing circuit 15 extracts a timing component from the burst signal and outputs a clock at a baud rate f _B to the identification circuit 14. The identification circuit 14 transmits the burst signal to the timing circuit 1.
The baud rate f _B from 5 is identified according to the clock, and output to the output terminal d. That is, the identification circuit 14 identifies the burst signal at the identification points T ₁ to T ₄ shown in FIG. In this way, when the identification circuit 14 performs identification, the echo component E due to the bridged tap is buried between each identification point, so that the echo component is no longer identified as a signal.

Furthermore, since the station side EX has the bridged tap equalizer 10, it outputs a predetermined burst signal to the output terminal b by performing the operation described in the conventional example.

That is, the burst transmission system of the present invention transmits a burst signal that has a longer burst length than the burst length of the burst signal transmitted from the subscriber side, which is transmitted from the station side having a bridged tap equalizer. This is to prevent erroneous identification of the echo component of the burst signal received at the side.

The meaning of this system is as follows. Let me explain with an example. Now assume that 30KbPS bidirectional communication is required between the terminal station and the subscriber. It is also assumed that the transmission path is in a state where signals can be determined without being affected by echo up to 40 KbPS. The signal speed on the transmission line under this condition is 2×
30KbPS (60KbPS) or more is required, and the conventional system that uses the same signal speed (baud rate) in both directions requires a bridged tap equalizer for terminal stations and subscribers. The condition for realizing 30KbPS bidirectional transmission is to obtain an average speed of 60KbPS or more on the transmission path. For example, if transmission is performed at 80 KbPS from the subscriber to the station and 40 KbPS from the station to the subscriber, an average speed of (80+40) KbPS/2=60 KbPS will be obtained, and the specified transmission will be possible. Moreover, at 40 KbPS, the identification circuit does not sample the echo component and there is no need for bridged tap equalization, so the bridged tap equalizer can be removed from the subscriber circuit.

〔Effect of the invention〕

As described above in detail, according to the present invention, burst transmission can be performed at the required transmission speed, and the bridged tap equalizer can be provided only on the station side and omitted on the subscriber side. Therefore, on the subscriber side, it is possible to downsize the device, reduce power consumption, and lower the price.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the configuration of a conventional burst transmission system, FIG. 2 is an explanatory diagram of the operation of FIG. 1, FIGS. 3 to 6 are diagrams showing one pulse of a received burst signal, and FIG. The figure shows an example of the configuration of the burst transmission system of the present invention, FIG. 5 is an explanatory diagram of the operation of FIG.
This figure shows one pulse of a received burst signal in the present invention, and FIG. 7 shows the configuration of a bridged tap equalizer. In the figure, EX is the station side, A is the subscriber side, 1, 7, 9,
14 is an identification circuit, 2, 6, 10 are bridged tap equalizers, 3, 8, 12, 15 are timing circuits, 4b, 5b, 11b, 13b are √AGC equalizers, 4a, 5a, 11a, 13a are transmitters It is a circuit.

Claims (1)

[Claims] 1. A burst signal having a predetermined baud rate is transmitted and received between the station side EX and the subscriber side A in a time-division manner, and when each burst signal is received, a clock extracted from the received burst signal is transmitted and received between the station side EX and the subscriber side A. Therefore, in the burst transmission method that identifies the burst signal, in the burst signal sent from the station side EX to the subscriber side A, the echo component caused by the influence of the transmission line L is terminated between the clocks. On the other hand, for the burst signal sent from the subscriber side A to the station EX, a high baud rate such that the echo component is applied to the clock is selected, and for the station EX A burst transmission system characterized in that a bridged tap equalizer 10 for removing the echo component is provided, while the subscriber side A is not provided with a bridged tap equalizer to obtain a predetermined transmission speed as a whole.