JP2685853B2 - Multiple access control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a communication system in which a plurality of terminal devices use a bidirectional communication line to communicate with a central processing unit, and the uplink traffic is equal to or higher than a reference value. The present invention relates to a multiple access control method capable of efficiently controlling congestion with respect to a terminal device when it becomes.

[Conventional technology]

Figure 1 is a diagram showing an example of a configuration of a multiple access scheme in a wireless communication system, 1 a central processing unit, 2 ₁ to 2n each terminal device, 3 downlink (central processing unit → terminal) Reference numeral 4 denotes an uplink (terminal device → central processing unit).

In the system as shown in FIG. _1, since there are a large number of terminal devices 21 to 2n for one central processing unit 1, when a plurality of terminal devices simultaneously transmit signals to the central processing unit 1. , A collision between signals occurs.

Therefore, in the conventional wireless communication, the following method has been adopted in order to reduce these collisions.

(I) A skyline control method in which the central processing unit monitors the usage state of the uplink and, when it is in use, restricts transmission to each terminal device using the downlink.

(Ii) In order to reduce the collision rate by preventing partial overlap of signals, when transmitting signals from the terminal device to the central processing unit, all signal transmission should be synchronized with the downlink synchronization signal. Method to perform (hereinafter also referred to as slotted aloha method).

FIG. 2 is a time chart in the case of the former sky line control method, where 5 and 6 are signals, 7, 9 and 11 are sky line patterns, and 8 and 10 are
Indicates a prohibition pattern.

FIG. 3 is a time chart of the latter slotted aloha system, where 12 and 13 are transmission signals, 14 is a frame signal, and 1
5 indicates a signal length, and 16 indicates a frame signal transmission cycle.

In the skyline control method, the terminal device is programmed so that it can transmit the transmission signals 5 and 6 to the uplink only when it can receive a specific pattern signal (skyline signal) 7, 9 and 11 on the downlink. Has been done. Upon detecting the signals 5 and 6 from the terminal device, the central processing unit immediately stops the down line signal 7, 9 and 11 and transmits the prohibition signal 8 and 10 to transmit signals from other terminal devices. Deter.

Further, in the slotted aloha system, as shown in FIG. 3, when the terminal side performs signal transmission, signal transmission is performed in synchronization with the downlink frame signal. The transmission cycle 16 of the frame signal is optimally equal to the signal length 15.

On the other hand, the congestion regulation adopted in, for example, a car telephone system can be roughly classified into a radio system congestion regulation and a control system congestion regulation.

 FIG. 9 shows an example of the system configuration of the car telephone system.

In the figure, 35 is an outgoing call control channel, 36 is an incoming call control channel, 37 is an outgoing call control transceiver, 38 is an incoming call control transceiver, 39 is a wireless base station, 40 is a wireless line control station, 41 is a wireless system, and 42 is The control system is shown.

In such a car telephone system, conventionally, in order to prevent collision between signals, a skyline control system is used.Congestion regulation in this case is caused by congestion due to an emergency situation such as a disaster that causes uplink traffic to When the standard value is exceeded, only public subscribers will be able to communicate,
Two types of general skyline signals and emergency skyline signals are provided for skyline signals (skyline patterns 7, 9, 11 in FIG. 2), and when necessary,
It adopted a method of switching to an emergency skyline signal and allowing only outgoing calls from highly public subscribers.

[Problems to be solved by the invention]

A method of providing congestion control by providing a general skyline signal and an emergency skyline signal as described above is effective in terms of wireless system congestion control and control system congestion control, but is a highly public subscriber. Since it is less than a few percent for all subscribers, congestion control is performed more than necessary, so it cannot be said to be an appropriate control method, and signals from general subscribers concentrate when the emergency skyline signal congestion is released. Since there is a possibility of congestion again, there is a problem that it cannot be said to be an effective congestion regulation in system operation.

In addition, as a congestion mitigation measure at the time of congestion, which is slightly different from the congestion regulation, there is a method of grouping terminal devices. This is, for example, an algorithm that groups terminal devices at the time of congestion, announces a terminal group capable of signal transmission with a downlink signal, and allows only the corresponding terminal device to transmit a signal, and achieves call decentralization. It is a method that can.

However, this method is also effective as a countermeasure against congestion in the wireless system, but there is a problem that it cannot be applied to the congestion regulation of the control system because the load of the control system increases because the processing amount for control increases. It was

Furthermore, in the slotted aloha method, because the method that does not perform skyline control, it is not possible to provide general skyline signals and emergency skyline signals, and not only the wireless system congestion regulation but also the control system congestion regulation There was a problem that there was no effective means to implement it.

In view of the above conventional problems, the present invention aims to provide a wireless line control system that efficiently regulates congestion in a multiple access system that performs signal transmission in synchronization with a downlink frame signal. There is.

[Means for solving the problem]

According to the present invention, the above-mentioned object is achieved by the means described in the claims.

That is, according to the present invention, a central processing unit and a plurality of terminal units are connected by a common bidirectional communication line, and the central processing unit sends a frame synchronization signal to a downlink from the central processing unit to the terminal unit. In a communication system in which a signal is transmitted in a time slot having a slot width synchronized with the downlink frame synchronization signal when transmitting a signal from the terminal device to the central processing unit in the uplink, Means for monitoring the traffic of the, the means for transmitting the frame synchronization signal to the downlink at a predetermined cycle, and when it is detected that the traffic of the uplink exceeds a predetermined reference value, This is a multiple access control system provided with means for controlling to change the transmission cycle to the downlink.

[Action]

FIG. 4 is a flow chart showing the algorithm of the present invention, and 17 and 18 show the characteristic operation of the present invention.

That is, the present invention monitors the uplink traffic by the central processing unit, and changes the transmission period of the frame signal to regulate the congestion when the traffic exceeds the reference value.

〔Example〕

FIG. 5 is a diagram showing an example of the configuration of a central processing unit for carrying out the present invention in a wireless communication system, where 19 is a receiver, 20 is a signal processing device, 21 is a traffic monitoring device, and 22 is a signal. A generation control unit, 23 is a signal generation unit, 24 is a transmitter, 25 is a receiving antenna, and 26 is a transmitting antenna.

In the figure, a signal indicating that the transmission period of a frame synchronization signal (hereinafter also simply referred to as a frame signal) is changed is transmitted from the traffic monitoring device 21 in which the traffic exceeds the reference value, to the signal generation unit 23 accordingly. A signal is generated by changing the transmission cycle of the frame signal.

The terminal device transmits a signal in a time slot of a frame synchronized with the frame signal. Therefore, if the transmission cycle of the frame signal changes, its slot width changes.

The fact that congestion can be regulated by changing the transmission period of frame signals will be described below.

FIG. 6 is a diagram showing the maximum throughput (hereinafter, also referred to as system capacity) characteristics after changing the slot width in the slotted Aloha system, where 27, 28 and 29 have a slot width T of 0.5T ₀ , T _0, 2T ₀ (T ₀ is the signal length) indicates the maximum throughput corresponding to.

The maximum value of the maximum throughput is that the slot width T is the signal length.
We can get 0.368 when it is equal to T ₀ , which is the slot width normally used in the slotted Aloha system.

Further, it can be seen that the system capacity changes only by slightly changing the slot width T from the signal length T ₀ , and in particular, the system capacity is sharply reduced only by making it slightly smaller than the signal length T ₀ . When congestion control is performed in the skyline control method, signal transmission from the terminal device was not possible, but in this method, transmission from the terminal side is not suppressed (unlike skyline control).

Then, by shifting the slot width T from T ₀ , the collision rate of signals increases, and the amount of signals that can be received by the central processing unit decreases. And this is because the collision rate between the signals increases, and as a result, the signals do not reach the central processing unit, so that the number of signals processed by the central processing unit also decreases, so that the congestion control of the control system is also performed. Become.

The present invention utilizes this to restrict congestion by changing the slot width when the uplink traffic becomes larger than the reference value.

For example, when the traffic becomes larger than the standard value, the system capacity is reduced by changing the slot width from 28 to 27 or 29, and the effect of congestion regulation becomes about 50%. As a result, it can be seen that the congestion regulation rate can be arbitrarily changed.

FIG. 7 is a diagram showing the throughput characteristics when the slot width is changed, where 30 shows the characteristics when T = T ₀ , 31 shows the characteristics when T = 0.5T ₀ , and 32 shows the characteristics when T = 2T ₀ .

Further, FIG. 8 is a diagram showing the effect of the present invention (ratio of congestion regulation) when the slot width is changed, and 33 is T = 0.5T.
₀ and 34 indicate the case of T = 2T ₀ .

For example, in order to enforce congestion control when the signal occurrence rate reaches 15 (packet / sec), the slot width is changed from T ₀ to 0.5T.
_By setting ₀ or 2T ₀ , the effect of congestion regulation is T = 0.
It can be seen that it is about 70% when 5T ₀ , and about 50% when T = 2T ₀ .

〔The invention's effect〕

As described above, according to the present invention, in the slotted aloha system, not only the congestion control of the wireless system but also the congestion control can be efficiently performed to prevent the overload of the control system.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a configuration of a multiple access system in a wireless communication system, FIG. 2 is a time chart of a sky line control system, and FIG.
FIG. 4 is a time chart of the slotted aloha system, FIG. 4 is a flow chart showing an algorithm of the present invention, FIG. 5 is a diagram showing an example of the configuration of a central processing unit for implementing the present invention in a wireless communication system, and FIG. FIG. 7 shows the maximum throughput characteristics when the slot width is changed in the slotted aloha system, FIG. 7 is the throughput characteristics when the slot width is changed, and FIG. 8 is the slot width. FIG. 9 is a diagram showing an effect of the present invention at the time, and FIG. 9 is a diagram showing an example of a system configuration of a car telephone system. 1 ...... central processing unit, 2 ₁ to 2n ...... terminal, 3 ...... downlink, 4 ...... uplink, 5,6 ...... signal, 7, 9, 11 ...... empty line pattern, 8, 10 ... ... Prohibition pattern, 12, 13 ... Transmission signal, 14 ... Frame signal, 15 ... Signal length, 16 ... Frame signal transmission cycle, 17,18 ... Characteristic operation of the present invention, 19
...... Receiver, 20 …… Signal processing device, 21 …… Traffic monitoring device, 22 …… Signal generation control unit, 23 …… Signal generation unit, 24
...... Transmitter, 25 …… Reception antenna, 26 …… Transmission antenna, 27 …… Maximum throughput when T = 0.5T ₀ , 28 ……
Maximum throughput when T = T ₀ , 29 ... Maximum throughput when T = 2T ₀ , 30 ... Throughput characteristic when T = 0.5T ₀ , 31 ... Throughput characteristic when T = T ₀ , 32 ……
Throughput characteristics when T = 2T ₀ , 33 ... T = 0.5T ₀ effect, 34 ... T = 2T ₀ effect, 35 ... outgoing control channel, 36 ... incoming control channel, 37 …… Transmission control transceiver, 38 …… Incoming control transceiver, 39 …… Wireless base station, 40
...... Wireless line control station, 41 ...... Wireless system, 42 ...... Control system

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area H04L 11/00 310B

Claims (1)

(57) [Claims] 1. A central processing unit and a plurality of terminal units are connected by a common bidirectional communication line, the central processing unit sends a frame synchronization signal to a downlink line from the central processing unit to the terminal unit, and the terminal unit is In a communication method in which a signal is transmitted by a time slot having a slot width synchronized with the downlink frame synchronization signal when transmitting a signal from the terminal device to the central processing unit on the uplink, the central processing unit A means for monitoring traffic, a means for sending a frame synchronization signal to the downlink at a predetermined cycle, and a means for sending the downlink of the frame synchronization signal when it detects that the uplink traffic exceeds a predetermined reference value. A multiple access control method, characterized in that it is provided with means for controlling so as to change the transmission cycle to the line.