JPH0362057B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for requesting call frequency assigned multiple access (Demand Assigned Multiple Access≡
DAMA) method.

In recent years, there has been an increase in the construction of telephone networks using satellites, but most of them are based on the pre-assignment method, in which lines are fixedly assigned, or the International Telecommunications Satellite Organization (Intelsat) uses a multi-channel network with 50 to 60 stations. Spade System (Single
Channel por Carrier PCM Multiple Access
Demand Assignment Equipment) is common. In the future, as satellites become more powerful, plans for a telephone network in depopulated areas in which many small ground stations will be interconnected via the same satellite are likely to be realized. In such a situation, it is necessary to efficiently process calls from hundreds or thousands of small traffic stations using an economical system. That is, there is an urgent need for a multiple access system based on inexpensive equipment that can be accommodated in each small ground station.

In order to meet such demands, the purpose of the present invention is to propose a multiple access system in which the multiple access function is distributed to each ground station using inexpensive equipment centered around a central station equipped with a simple line monitoring function. It is in.

This invention sends an idle line signal from the central station to a downlink available for communication, indicating the line on which a call request signal should be sent to the desired station, and also indicating the line to which all slave stations waiting for reception should receive the signal. In the suggested multiple access scheme, all desired stations are pre-ordered,
Using a call signal selector that randomly selects N types of call signals each time, each selected call signal is sent to an uplink that corresponds to the downlink; the central station that receives the group of call signals, Immediately stops transmitting the idle line signal; sends the call signal group received in place of the idle line signal as an acknowledgment signal through the downlink; each station receiving the acknowledgment signal receives the call signal of its own choice. by an acknowledge signal decoder that verifies whether the call signal is the highest among the received acknowledge signals;
It continues to send call signals only when its own call signal is at the highest level; otherwise, it immediately stops sending call signals; the desiring station that continues to send call signals continues to send call connection information. By sending
The present invention provides a multiple access system characterized by preventing multiple acquisition of idle lines.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows the transponder frequency arrangement for a telephone line using a satellite. In a wireless telephone line, two channels (upper and lower) form a pair to form a telephone line. In the diagram, 1000 and 100
0', 1001 and 1001', 1002 and 100
2' and 1003 and 1003' are each a pair,
It consists of 4 telephone lines. For convenience, the former of each pair is defined as a downlink, and the latter is defined as an uplink. Conventionally,
In order to perform connection processing for each line, a control line is provided in addition to these call lines, and each ground station performs connection control via the control line. In this case, it is necessary to equip all stations with a transmitter/receiver dedicated to the control line, and the processing capacity of the central station that mediates control signals becomes considerably large.

The invention therefore proposes multiple access without using any such dedicated control lines. The prerequisite connection procedures are shown in FIGS. 2 to 5 below.

First, the central station monitors only the line usage status within the satellite transponder, and if an idle line exists, it sends an idle line signal to the downlink. In Figure 2, 100 is the central station, 101 is the communication desired station, and 1
010 indicates a blank line signal. Next, as shown in FIG. 3, the station desiring to make a call receives the empty line signal 1010, learns of the existence of an empty line on which it can talk, and transmits the call signal 1010.
11 is sent to the central office through the uplink.

Next, as shown in Fig. 4, the central station receives a call signal from the station 101 requesting a call and learns that this empty line will be used for calls, so it takes care to prevent subsequent stations from sending out call signals. and stop the blank signal.

Next, as shown in FIG. 5, the central office sends out the received call signal as it is as an acknowledgment signal instead of a blank line signal. Since the receiving station is intercepting the same idle line, it will respond only if the line connection information from the desired station is addressed to its own station.

Now, let us consider a case where the station desiring to talk issues a call signal to multiple stations at the same time. Figure 6 shows this situation. In this case, if the two ground stations 101 and 102 transmit call signals 1011 and 1012 at the same time, the central station will send them back as they are, so each station will send the call signals 1011' and 1011 as acknowledgment signals.
It can be seen that two waves of 2' were received at the same time, resulting in double capture. In such a case, it is necessary to decide which station will finally be allowed to use this empty line.

The main purpose of the present invention is to prevent this multiple acquisition. FIG. 7 shows the arrangement of call signals used by each station. The call signal consists of two groups of 20 waves, and one call signal is transmitted in parallel with two waves, one wave each from the upper and lower groups. In the figure, waves 90, 80,
70-20, 10,00 is upper group 10 wave, wave 9,
8,7 to 1,0 respectively indicate the lower group 10 waves. As a result, each call signal is transmitted from 99 to 99 by parallel transmission of two waves.
This constitutes a group of 100 ordered signals up to 00.

FIG. 8 shows a block diagram of an apparatus for randomly selecting each call signal from the N pre-ordered call signals described above. In the figure, reference numerals 201 and 202 indicate call signal-like oscillators for 10 waves in each of the upper and lower groups, and 300 indicates a call signal selector that randomly selects one wave in each of the upper and lower groups.

FIG. 9 shows a block diagram of an acknowledge signal decoder that determines whether its own call signal is the highest among the received acknowledge signals. In the diagram, 4001 and 400
2 is a signal detection group of 10 waves in each upper and lower group, each including bandpass filters 401, 402,...410 and a detector 42.
1,422,...430. 500
is a determination circuit that determines whether its own call signal is the highest level from the output obtained from the signal detector group.

In this case, the probability that two stations will select the same call signal is still 0.01, but there is a considerable time lag between the time when the central tail sends out a blank signal and the time when each ground station captures it. As expected, the residual double acquisition rate of 0.01 can be said to be a sufficiently small value considering the low probability that several stations will send out call signals at the same time.

Regarding the embodiment of N types of call signals, this application uses 20 different frequency signals, but N types of other call signals are used.
It is also conceivable to have a random delay and set the priority order on a first-come, first-served basis for satellite return.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a transponder frequency arrangement for a satellite telephone line. 2 to 6 are diagrams for explaining the connection procedure of the blank line signal sending type. FIG. 7 is a diagram showing an embodiment of N types of call signals of the present invention. FIG. 8 is a block diagram of the main element of the present invention, a call signal selector. FIG. 9 is a block diagram of the acknowledge signal decoder, which is the main element of the present invention.

Claims (1)

[Claims] 1 A multiple access system in which the central station sends out a vacant line signal to the available downlink vacant line, indicating the line on which a call request signal should be sent to the desired station, and also indicating the line on which all slave stations waiting for reception should receive the signal. In this case, all stations desiring a call use a call signal selector that randomly selects N types of call signals ordered in advance each time, and sends each selected call signal to the upstream line corresponding to the downlink line. When the central station receives the call signal group, it immediately stops transmitting the idle signal; it sends out the call signal group received in place of the idle line signal as an acknowledge signal through the downlink; the acknowledge signal; Each station that receives the call signal uses an acknowledgment signal decoder that verifies whether the call signal it has selected is at the highest level among the received acknowledge signals, and only when its own call signal is at the highest level, the station accepts the call. Continue to send the signal; otherwise immediately stop sending the call signal; the desired station that continues to send the call signal will continue to send call connection information to prevent multiple capture of idle lines. A multiple access method characterized by: