JPH02127835A - Radio line control system - Google Patents

Abstract

PURPOSE:To attain both the security of throughput and the improvement by quickening a transmission time of a synchronizing signal, revising a terminal group permitting communication when no incoming signal from a terminal equipment exists and suppressing the transmission of a signal by the terminal equipment when the received group number is not the group number belonging thereto. CONSTITUTION:When a reception antenna 29 receives an incoming signal 28, a central processing unit uses a receiver 30 to apply demodulation and frequency conversion, and a control CPU 34 of the central processing unit applies the discrimination of the presence of the incoming signal based on the result of detection of a preamble signal placed in front of the data signal. Then if no reception signal arrives even after a prescribed time or over, the transmission time of the next frame signal is quickened and the group of terminal equipments allowing the communication is revised. On the other hand, the terminal equipment side suppresses the signal transmission when the line assignment terminal group number included in a frame information signal is not the group number belonging to itself. Thus, the throughput is not reduced suddenly at a high traffic and the maximum throughput is increased.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides a system in which a plurality of terminal devices use a bidirectional communication line,
The present invention relates to a wireless line control method that allows efficient use of communication lines when a plurality of terminal devices attempt to randomly transmit burst signals in a communication method for communicating with a central processing unit.

[Conventional technology]

FIG. 1 is a diagram explaining the configuration of a conventional multiple access system, in which 1 is a medium heat processing device, 21 to 2 are terminal devices, 3 is a down line (central processing unit→terminal device), and 4 is a diagram explaining the configuration of a conventional multiple access system. represents the uplink (terminal device→central processing unit). .

In such a system, a large number of terminal devices 2-20 exist for one central processing unit 1, so if multiple terminal devices simultaneously transmit signals to the central processing unit 1, a collision between the signals may occur. occurs.

Therefore, conventionally, in order to reduce the occurrence of such collisions, when transmitting signals on the uplink, all signals are transmitted in synchronization with the synchronization signal on the downlink.
A method was used to reduce the collision rate between signals (hereinafter, such a method will be referred to as the slotted Aloha method).

FIG. 2 shows a time chart when a signal is successfully transmitted in the slotted Aloha method.

In the figure, 5 to 7 are when there is no transmission signal, 8.9 is when there is a transmission signal, 10 to 14 are frame signals (synchronization signals), and 15.16 is a reception confirmation signal for transmission signal 8.9 (center (processing device → terminal device).

Fig. 3 shows a time chart when signals collide, 17.18 is a transmission signal, 19 is a signal retransmitted from transmission signal 17, and 20 to 24 are frame signals (synchronization signals).
, 25 indicate a reception confirmation signal for the transmission signal 19.

The operation of the above conventional system will be explained below.

In FIG. 2, when the terminal device transmits the signal 8 in synchronization with the 7-rem signal 11, the central processing unit 1 transmits a reception confirmation signal 15 to the terminal device only when the signal is received without collision. do.

If the reception confirmation signal 15 from the central processing unit 1 cannot be received even after waiting for a certain period of time, the terminal device determines that there is a signal collision, delays the signal and resends it as shown in FIG. 3, 19. .

The throughput with respect to the signal occurrence rate in this system is shown in Fig. 7 (2). Compared to the case (Aloha system) in which the uplink is not slotted (2), the throughput characteristics are considerably improved, and the maximum throughput is twice as high.

[Problem to be solved by the invention]

In the slotted Aloha system as described above, by slotting the uplink, collisions between signals do not occur due to partial overlap, but rather due to transmission signals 17 and 18 shown in Figure 3.
The entire signal overlaps, like a collision. Therefore, since the conditions for signal collision are limited, it is possible to reduce the collision rate between signals.

However, in this slotted Aloha method, the eighth
As shown in the figure, the maximum throughput was at most 0.368, and there was a further drawback that the throughput deteriorated rapidly during high traffic.

Furthermore, if no signal is generated, one slot (signal length) becomes a waste of time, as shown in FIGS. 5-7. This proportion of wasted time is due to the low rate of signal occurrence.
The problem is that the longer the signal length, the larger the signal length, which leads to a decrease in line usage efficiency.

In view of these conventional problems, the present invention provides an additional function with a simple configuration to the slotted Aloha method, thereby ensuring a higher throughput than the slotted Aloha method and improving throughput in high traffic areas. The purpose of this research is to provide a wireless line control system that can achieve the following.

[Means to solve the problem]

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

That is, in the present invention, a central processing unit and a plurality of terminal devices are connected via a wireless communication line, the terminal devices are divided into a plurality of groups, and the central processing unit sends a synchronization signal to the downlink, A group of terminals that are capable of transmitting signals is announced on the downlink in synchronization with the synchronization signal of In a communication system in which signal transmission is precisely controlled, the central processing unit has a means for determining the presence or absence of an uplink signal from a terminal device, and a synchronization method for transmitting to the downlink when there is no upstream signal from the terminal device. A wireless line provided with a means for advancing the timing of signal transmission and a means for changing the terminal group to which communication is permitted, as well as a means for suppressing signal transmission when the group number received by the terminal device is not the group number to which the terminal device belongs. It is a control method.

[For production]

Figure plS4 is a flowchart showing the principle operation of the present invention, (&) indicates control in the central processing unit, (b) indicates control in the terminal device, and the parts indicated by 26 and 27 are the main points of the present invention. It shows behavior that is a characteristic feature.

That is, in the present invention, the central processing unit is
), when a received signal from a terminal device is waiting for a received signal and the received signal does not arrive even after waiting for a predetermined period of time, the next frame signal transmission time is brought forward and communication is permitted. change.

On the other hand, on the terminal equipment side, as shown in FIG. Deterrence and times Mi! ! 1. Wait until the current terminal group number becomes the group number to which it belongs, and then transmit the signal.

〔Example〕

FIG. 5 is a diagram showing an example of the configuration of a central processing unit according to an embodiment of the present invention, in which 28 is an upstream signal, 29 is a receiving antenna, 30 is a receiver, 31 is an audio filter section, and 32 is a Data filter section, 33 is a control line, 34 is a control CPU
, 35 is an upstream audio signal, 36 is a downstream signal, 37 is a control unit, 38 is a signal generation unit, 39 is a clock, 40 is an audio filter unit, 41 is a data filter unit, 42 is a transmitter,
43 is a synthesizer circuit, 44 is a transmitting antenna, 45 is a downstream signal, and 46 is a signal generation control section.

In the figure, an upstream signal 28 (for ease of explanation, consider the case of only data signals) is transmitted to the receiving antenna 28.
9, the receiver 30 demodulates and converts the frequency. The determination of the presence or absence of an upstream signal is made by the control CPU 34 of the central processing unit based on the detection result of the preamble signal preceded by the data signal.

In the case of the slotted Aloha system, the upstream signal is transmitted in synchronization with the frame signal, so the central processing unit can grasp the timing of upstream signal reception.

In other words, the transmission timing of the frame signal is controlled by the control line 33.
If the frame signal is being monitored, preamble detection can be started using frame signal transmission as an opportunity. Therefore, the reception level of the preamble signal is measured for a period of Δt after detection of the preamble signal is started, and if the reception level is equal to or higher than a certain specified value, it is determined that the preamble signal has been detected.

An output signal indicating the presence or absence of preamble detection is transmitted from the control CPU 34 to the signal generation control section 46. If there is a preamble signal, the next signal reception state is entered without changing the line assigned terminal group, but if there is no preamble signal 1, a signal indicating that the line assigned terminal group will be changed is controlled. Part 37
The signal is transmitted to the signal generating section 38 from there.

The line assigned terminal group number is announced by a 7-frame information signal,
The terminal device can recognize which terminal group the next slot belongs to by comparing it with the group number to which it belongs, which is stored in advance in the ROM.

The 7 frame information signal is a signal containing the line assigned terminal group number and the transmission time information of the next slot.

Times #X! The order of Fl may be in ascending order/descending order, etc., and in the embodiment of the present invention, the order is in ascending order as shown below.

FIG. 16 is a time chart showing an example of the operation of an embodiment of the present invention.

In the same figure, 52 to 58 are transmission signals, 59 to 64 are frame signals, 65.66 are 7 frame signals whose transmission timing is advanced, 67 to 74 are frame information signals, 75 to 80 are reception confirmation signals, and 81 .82 is a conventional 7-rem signal shown for comparison, 83 to 88 are slots whose time is 1+, and 8
9 to 93 indicate times when they are in other groups.

The operation of this embodiment will be explained below using the time chart of FIG.

Note that in the figure, ◯ marks indicate that a signal occurs between slots, and X marks indicate that a signal does not occur between slots.

The terminal device in which the call occurred between the slots with the signal 83 transmits the transmission signal 53 to the central processing unit in the next slot 84 in order to transmit the signal in synchronization with the next 7-frame signal. Only when the central processing unit can receive the transmission signal 53 without collision, the central processing unit transmits a reception confirmation signal 76 to the terminal device.

If the terminal device does not receive the reception confirmation signal even after waiting for a certain period of time, the terminal device assumes that a signal collision has occurred and retransmits the signal after a certain random time delay. This algorithm is the same as the conventional method.

Although there is a transmission signal 53 in slot 84, since no signal is generated when slot 84 is open, there is no reception signal in the central processing unit in the next slot. When the signal occurrence rate is low, there is a high probability that no signal will occur, resulting in a large number of wasted slots and a decrease in line efficiency. In particular, when the signal length is long, the line efficiency is further reduced because the time for one slot is long.

Therefore, in the present invention, paying attention to this point, when there is no received signal in the central processing unit, the transmission timing of the next frame signal is advanced by t, -Δt, and the line allocation terminal equipment group is changed.

For example, in FIG. 7, since no signal occurs in slot 84 and there is no transmission signal in the next slot, the transmission timing of the next frame signal is advanced by 1+-Δt, and the line assigned terminal group number is changed to 1. Change from group to group 2. Similarly, 2
The change of the terminal group to which the line is assigned from group 3 to group 3 and from group 3 to group 1 is performed when there is no signal from the group number terminal device.

The control to advance the transmission timing as described above is performed as follows.

That is, as described above, the output signal of the preamble signal detection circuit is transmitted from the control CPU 34 to the control section 37, but in addition to this, if there is a signal, the transmission period of the frame signal is not changed; If there is no signal, a control signal is transmitted from the control unit 37 to the clock 39 to advance the period of the clock 39 for signal generation in order to advance the transmission timing of the frame signal, and the frame signal whose transmission timing is advanced is transmitted. generated.

In the conventional method, the groups were changed at regular intervals, but
By using the method of the present invention, it is possible to preferentially allocate channels to areas with a large amount of traffic.

Hereinafter, simple mathematical formulas will be used to quantitatively illustrate the present invention.

The collision rate of the method according to the present invention is as follows: (i>When the line is assigned to the terminal device group to which it belongs, signals occur in a plurality of terminal devices and a collision occurs in the next slot.

(ii) When the line is not assigned to the terminal group to which they belong, signals are generated in a plurality of terminal devices, and the signals are transmitted all at once at the same time as the line is assigned to the terminal group to which they belong, causing a collision.

There are two possibilities.

If the probability that the line is assigned to another terminal group is P, then The signal collision rate is calculated using the following formula.

C=(1-P) exp (-λ't1) Pexρ
(−λ′t1)・・・・・・・・・・・・(1) Here, λ′=λ/m ・・・・・・・・・・・・
(2) t=(m-1)nt, +Δt...
... (3) P=t/(t+nt+) ""...
... (4).

Also, n is a function of the probability that the signal is continuous, and here, if the average value is used, n=exp(λ't+
) −exp (−人'm(Δ1 +1+) ) /(
(1-exp (-in'(m-1) t +) (1-e
xp (−人't+)))2・・・・・・・・・・・・
...... (5).

Therefore, the throughput is: 5=(1-C)λ tl ・・・・・・・・・・
... Find it using (6).

From equation (6), t+=50msec, Δt=25mS
In the case of ee, FIG. 7 shows the throughput characteristics when the group size is changed by several meters.

In the figure, ■ is the slotted Aloha method, ■ is the Aloha method, ■ is the method of the present invention (when m = 1), ■ is the method of the present invention (when m = 2), and ■ is the method of the present invention. (m=3
) is shown.

As shown in the figure, it can be seen that in the present invention, the larger the group size by several meters, the more distributed the traffic is, and as a result, the rapid decrease in throughput during high traffic can be prevented.

On the other hand, it can be seen that as the number of groups increases, the maximum throughput tends to decrease.

〔Effect of the invention〕

As explained above, according to the method of the present invention, the maximum throughput can be increased without a sudden decrease in throughput even in times of high traffic, and the advantage is that lines can be used effectively by reducing unnecessary empty slots. There is.

[Brief explanation of drawings]

Figure 1 is a diagram explaining the configuration of a conventional multiple access system;
3 is a time chart showing an example of the operation of the conventional slotted Aloha method, FIG. 4 is a flowchart showing the principle operation of the present invention, and FIG. 5 is an example of the configuration of an embodiment of the present invention. In the figure shown in FIG. 6, Section 6 is a time chart showing an example of the operation of an embodiment of the present invention, and Fig. In7 is a diagram showing an example of the throughput characteristics of the present invention. 1...Central processing unit, 21~2o
・・・・・・Terminal device, 3 ・・・・・・
Down line, 4...Up line, 5-7
・・・・・・When there is no transmission signal, 8.9
...... Transmission signal, 10-14 ...... Frame m+, is・16 ...... Reception confirmation signal, 17.18 ...... Transmission signal, 19 ... ...Retransmission number 17,
20~24... 7 frame signal,
25 ・・・・・・Reception confirmation signal, 26.2
7...Characteristic operation of the present invention, 2811819
．． Upstream signal, 29...Receiving antenna, 30...Receiver, 31.32
・・・・・・ Filter, 33 ・・・
...Preamble detection circuit, 34...
...Control CPU, 35 ...Uplink audio signal, 36 ...Downlink signal, 37
...control section, 38...signal generation section,
39... Clock, 40.
41... Filter, 42...
...Transmitter, 43 ...Synthesizer circuit, 44 ...Transmission antenna,
45...downlink signal, 46...signal generation control section, 52-58...transmission signal,
59-64... Frame signal,
65.66... Frame i whose transmission time has been advanced, 67-74... Frame information signal, 75-80... Receipt confirmation signal,
81.82...Conventional 7-frame signal, 3-88...Time slot, 89-93...Time in other groups

Claims (1)

[Claims] A central processing unit and a plurality of terminal devices are connected via a wireless communication line, the terminal devices are divided into a plurality of groups, and the central processing unit sends a synchronization signal to a downlink, A group of terminals that are capable of transmitting signals is announced on the downlink in synchronization with the synchronization signal of In a communication system that is controlled to transmit signals, the central processing unit has a means for determining the presence or absence of an uplink signal from a terminal device, and a means for determining the presence or absence of an uplink signal from a terminal device, and a means for determining the synchronization signal sent to the downlink when there is no upstream signal from the terminal device. It is characterized by providing a means for advancing the transmission timing and a means for changing the terminal group to which communication is permitted, as well as a means for suppressing signal transmission when the group number received by the terminal device is not the group number to which the terminal device belongs. Wireless line control method.