JPH0622343B2 - Multiple access method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a multiple access system in which a plurality of terminal devices communicate with a central processing unit using one bidirectional communication line. The present invention relates to a control method capable of efficiently using a communication line when trying to randomly transmit.

[Prior Art] Conventionally, a control system of this type will be described. For example, in a mobile communication system such as a car phone, a common wireless line (a plurality of terminal devices (mobile stations) and a central processing unit (base station) are used). It is connected by two frequencies (uplink and downlink), and the central processing unit controls the downlink of the terminal device in the downlink, thereby preventing multiple use of the uplink by multiple terminal devices. ing.

Figure 1 is a diagram illustrating a multiple access system with such common bidirectional communication line, 1 a central processing unit, 2 ₁
Each of _2n represents a terminal device. Also, 3 is a downlink transmitted from the central processing unit 1 to the plurality of terminal devices 2 ₁ to 2 _{n at} a common frequency, and 4 is a plurality of terminal devices 2 ₁ to 2 _n from the central processing unit 1. , Represents an uplink transmitted on a common frequency.

FIG. 2 is a time chart, where 5 is an upstream signal and 6 is a transmission permission signal transmitted on the downlink.

As shown in FIG. 2, the terminal device transmits the uplink signal only when it receives the transmission permission signal on the downlink. On the other hand, the central processing unit suspends transmission of the downlink transmission permission signal while receiving the uplink signal on the uplink. By transmitting and receiving such a signal, it is possible to prevent a plurality of terminal devices from simultaneously transmitting an uplink signal and causing a signal collision on the uplink. Further, the transmission permission signal is generally a repetition of a short pattern signal or a tone signal, and the terminal device can identify the transmission permission signal in an extremely short time.

Next, in the conventional multiple access method, a case where signals other than the transmission permission signal are transmitted on the downlink will be described.

FIG. 3 is a time chart of signals in the conventional system, where 5 is an upstream signal, 6 is a transmission permission signal, and 7 is a downlink signal other than the transmission permission signal.

FIG. 4 is a block diagram of a downlink signal generator of the central processing unit in the conventional system, in which 8 is a transmission permission signal generator, 9 is a downlink signal input, 10 is an uplink usage state signal,
Reference numeral 11 represents a signal selection circuit, and 12 represents an output section to the transmitter.

Conventionally, the signal selection circuit 11 shown in FIG. 4 allows the transmission permission signal generator 8 if the upstream line use state signal 10 is not used.
The transmission permission signal constantly transmitted from the relay station is relayed to the output unit 12 to the transmitter, and if it is in use, the relay is not performed. Further, when a downlink signal is input, the downlink signal input 9 is relayed to the output unit 12 to the transmitter regardless of the usage state of the uplink. Therefore, as shown in FIG. 3, when a downlink signal is generated when the uplink is not used, the transmission of the transmission permission signal is interrupted and the downlink signal is transmitted.

[Problems to be Solved by the Invention] In the above-described conventional method, during transmission of a downlink signal,
Even if the uplink is unused, the transmission permission signal is not transmitted, so that there is a drawback that all the terminal devices cannot transmit the uplink signal.

It is an object of the present invention to eliminate the drawback of the prior art in which the transmission permission signal is interrupted by the downlink signal regardless of the usage state of the uplink, and to provide a multiple access system with good uplink utilization efficiency.

[Means for Solving the Problems] The present invention achieves the above object by the means described in the scope of claims, wherein the central processing unit transmits the downlink signal when the uplink is in use. In addition, the central processing unit is provided with a buffer memory for temporarily accumulating a downlink signal, and the transmission of the downlink signal waits until a certain time elapses after the uplink is in use or a downlink signal is generated. It is different from technology.

[Embodiment] FIGS. 5 and 6 are views for explaining the first embodiment of the present invention. FIG. 5 is a signal time chart, and FIG. 6 is a signal generation of a downlink of a central processing unit. It is a block diagram of a part.

In this embodiment, as shown in FIG.
5 is provided, the downlink signal is accumulated in the buffer memory 14 even if the downlink signal 13 is generated during transmission of the transmission permission signal as shown in FIG. 5, and the signal selection circuit 11 is in use by the uplink. At that time, the downlink signal is read from the buffer memory 14 and relayed to the output unit 12 to the transmitter.

By such a method, it is possible to prevent an invalid stop of the transmission permission signal due to the downlink signal by transmitting the downlink signal only when the uplink is in use and the transmission permission signal is stopped. It becomes possible to raise.

FIG. 7 is a diagram for explaining the second embodiment of the present invention,
FIG. 3 is a block diagram of a signal generator of the downlink of the central processing unit.

In this embodiment, a timer 15 is provided in addition to the first embodiment. This timer measures the passage of time after the downlink signal is accumulated in the buffer memory, and when it exceeds a certain time, it instructs the signal selection circuit to interrupt the transmission enable signal even if it is being transmitted. And transmit the downlink signal.

By such a method, the transmission interval of the upstream signal is large,
When the waiting time until the downlink signal is transmitted is too long, the efficiency that the waiting time can be limited to a fixed time is obtained. Further, when the upstream signal is frequently transmitted, the transmission of the downstream signal due to the limitation of the waiting time hardly occurs. Therefore, the effect of improving the utilization efficiency equivalent to that of the upstream line shown in the first embodiment is sufficient. Can be obtained.

[Effects of the Invention] As described above, according to the method of the present invention, the transmission of the downlink signal is delayed until the transmission of the downlink signal is waited for until the transmission permission signal stops until the uplink is in use. There is an advantage that it is possible to prevent an invalid stop and improve the utilization efficiency of the uplink.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a multiple access system using a common bidirectional communication line, FIGS. 2 and 3 are time charts of signals in a conventional system, and FIG. 4 is a signal of a downlink in a conventional central processing unit. FIG. 5 is a block diagram of a generator, FIG. 5 is a time chart of a signal when the present invention is embodied, and FIG. 6 is a block diagram of a signal generator of a downlink in the central processing unit of the first embodiment of the present invention. FIG. 7 is a block diagram of a downlink signal generator in the central processing unit of the second embodiment of the present invention. 1 ...... central processing _unit, 2 1 to 2 _n ...... terminals, 3 ......
Downlink line, 4 ... uplink line, 5 ... uplink signal, 6 ... transmission permission signal, 7 ... downlink signal other than transmission permission signal, 8 ...
… Transmission permission signal generator, 9 …… Down signal input, 10 ……
Uplink usage status signal, 11 ... Signal selection circuit, 12 ...
… Output part to transmitter, 13… Generation of downlink signal, 14…
… Buffer memory, 15… Timer

Claims (2)

[Claims] 1. A plurality of terminals are connected to a central control unit through a common bidirectional communication line, and the central control unit transmits downlink information and a transmission permission signal to each terminal unit, In the communication system configured to prevent the collision of signals from a plurality of terminal devices by transmitting the upstream information to the central control device only when the transmission permission signal is detected, the central control device transmits When there is downlink information to be transmitted, the downlink information is transmitted during the time period when the uplink information is transmitted from the terminal device, and the transmission permission signal is transmitted during the time period when the uplink information is not transmitted from the terminal device. Multiple access method characterized by transmitting. 2. A plurality of terminals are connected to a central control unit through a common bidirectional communication line, and the central control unit transmits downlink information and a transmission permission signal to each terminal unit, In the communication system configured to prevent the collision of signals from a plurality of terminal devices by transmitting the upstream information to the central control device only when the transmission permission signal is detected, the central control device transmits When there is downlink information to be transmitted, the downlink information is transmitted during the time period when the uplink information is transmitted from the terminal device, and the transmission permission signal is transmitted during the time period when the uplink information is not transmitted from the terminal device. If the downlink information to be transmitted is not transmitted from the terminal device even after a certain period of time has elapsed after the downlink information to be transmitted is generated, the transmission permission signal being transmitted is interrupted and the downlink information is transmitted. Can send Multiple access scheme, wherein.