JPH06101728B2 - Method of avoiding call collision of local network - Google Patents

Description

The present invention relates to a call collision avoidance method in a local network.

(Prior Art) Conventionally, as a technology in such a field, for example, Nikkei Electronics, (1981-7-6) Nikkei Tuna Hill P.
110-133, JP-A-59-91527, and JP-A-58-116834.
Some of them were described in the official gazette. The configuration will be described below with reference to the drawings.

FIG. 2 is a schematic configuration diagram showing a configuration example of a conventional local network. In FIG. 2, in the transmission line 1,
Multiple devices 2-1 such as computer devices and terminal devices
2-N is connected to the bus, and each of these devices 2-1 to 2-N
Data is exchanged between them.

One of the access methods of such a local network is carrier sense multiple access / colliction detection.
sion detection, hereinafter referred to as CSMA / CD).
This CSMA / CD method is used when, for example, the device 2-1 transmits a packet (a data unit in which data is divided into bit strings of a fixed length or less and control information such as an address of the receiving side is added to the packet). The presence or absence of transmission of the devices 2-2 to 2-N is detected, and transmission is performed on condition that there is no transmission. If there is a transmission collision with another device 2-2, the devices 2-1 and 2-
This is a method in which transmission of No. 2 is stopped, and retransmission is performed after waiting for an appropriate time (this is called backoff processing).

In the CSMA / CD system, transmission collision detection and backoff processing are indispensable conditions.

First, in order to detect a collision, a circuit shown in FIG. 3 has been conventionally used. FIG. 3 is a configuration block diagram of a device 2 shown in FIG. This device 2 includes a transmitter 3, a receiver 4,
A collision detection circuit 5 including an exclusive OR circuit (XOR circuit), a control circuit 6 including a central processing unit (hereinafter referred to as CPU), and the like are provided. The control circuit 6 exchanges transmission / reception data with the transmitter 3 and the receiver 4. If the transmission data of the control circuit 6 is started to be transmitted to the transmission line 1 via the transmitter 3 and only the own device 2 is transmitting, the detection output of the collision detection circuit 5 becomes "0", and if other devices If it has also transmitted, the detection output becomes "1". When the detection output becomes "1", the control circuit 6 stops the transmission of the transmission data and performs the backoff process.

Next, in the backoff processing, the time from the collision detection to the retransmission is defined as the slot time. The slot time is
In order to prevent collision at the time of retransmission, it is necessary to take different times between the retransmitting devices, and in the prior art, it is set by a random number.

In the software using the CPU etc. in the control circuit 6,
The following method is available as a method for easily obtaining a random number.

(1) Use the program counter value while the program is in progress.

(2) A random number generation counter is prepared in the control circuit 6.

Such a method is an effective method when each of the devices 2-1 to 2-N operates with different software, and is used as a general method.

(Problems to be solved by the invention) However, in the conventional method, like the housing complex management system, a housing information board having the same function is installed in each dwelling unit,
In a local network where many of these are connected to the same bus and monitored by a centralized monitoring board, when random numbers are generated in each house information board, those house information boards use the same software under the same conditions. Because it's working
There is a problem that the generated random numbers may have the same value, and collision cannot be avoided.

SUMMARY OF THE INVENTION The present invention provides a call collision avoidance method for a local network, which solves the problem that the above-mentioned conventional techniques have, in that transmission collision cannot be avoided.

(Means for Solving Problems) In order to solve the above problems, the present invention provides a plurality of devices having the same function, which are connected to a transmission line by a bus (for example, provided in each dwelling unit in an apartment management system). (For example, a house information board that is used) transmits and receives packets by the CSMA / CD method, for example, detects the presence or absence of transmission from other devices, and transmits on the condition that there is no transmission. , In a method of avoiding a call collision in a local network, in which transmission is stopped and a predetermined slot time is waited for and then retransmission is performed, in the case of a transmission collision between the respective devices, all or part of a unique address assigned to the devices And the transmission reference clock signal are multiplied to calculate the slot time, the retransmission order is determined using the slot time, and the retransmission is performed.

Here, a part of the unique address given to the device is changed for each retransmission, and the slot time is calculated,
The retransmission order may be determined.

(Operation) According to the present invention, since the call collision avoidance method is configured as described above, when a transmission collision occurs between the devices, all or part of the addresses individually assigned to the respective devices are multiplied. Then, the multiplier is multiplied by the transmission reference clock signal to calculate the slot time. Then, the retransmission order is determined based on the calculated slot time, and the retransmission after the transmission collision is performed accordingly. This makes it possible to avoid the collision accurately.

Here, if a part of the unique address given to the device is changed for each retransmission when the slot time is calculated, the call collision avoidance rate can be improved in a short slot time. Therefore, the above problems can be eliminated.

(Embodiment) FIG. 1 is a time chart for explaining a call collision avoidance method according to an embodiment of the present invention, and FIG. 4 is a configuration diagram of an apartment house management system.

A call collision avoidance method in the housing complex management system will be described below.

As shown in FIG. 4, the collective housing management system has a configuration in which a plurality of housing information boards 12-1 to 12-N, a shared entrance board 13 and a central monitoring board 14 are connected to a control bus 11. Eggplant The house information boards 12-1 to 12-N are installed in each dwelling unit and have a disaster prevention alarm function and an intercom function. The common entrance board 13 is installed in the common entrance and has an intercom function with each of the house information boards 12-1 to 12-N.
In addition, the central monitoring board 14 is installed in the control room, has a disaster warning function and an intercom function, and has a housing information board 12-1 to 12-12.
-Centrally monitor and control the N and the common entrance board 13. The housing information boards 12-1 to 12-N, the common entrance board 13, and the centralized monitoring board 14 each include a transceiver, a collision detection circuit, and a control circuit as shown in FIG. Send and receive packets to and from each other.

Here, a decimal 4-digit dwelling unit number is directly assigned to each of the housing information boards 12-1 to 12-N as a device address. Further, the shared entrance board 13 and the centralized monitoring board 14 are given unique device addresses.

Access to each device in the housing complex management system is performed by the CSMA / CD method as shown in FIG. Figure 1 shows
The horizontal axis indicates time, and the rectangle above the horizontal axis indicates that packets are being transmitted. Since only one packet can be sent on the control bus 11 at the same time, for example, each house information board 12-1, 12-2, 12
-3 packets must not overlap.

First, when the house information board 12-1 sends the packet A1, the signal on the control bus 11 is detected (sense), and another house information board 12 is detected.
If there is no transmission from -2,12-3, transmission starts immediately. This makes the transmission successful.

While the packet A1 is being transmitted, the housing information board 12-2 receives the packet B1.
When transmitting the packet, the house information board 12-2 detects a signal on the control bus 11, determines that the signal is in use, and waits for the end of transmission of the packet A1 to transmit the packet B1. Therefore, the packet
The transmission of B1 also succeeds.

However, during the transmission of packet B1, the housing information boards 12-1, 12-
When the transmission request is generated in 3, the transmission of the packets A2-1 and C1-1 is started after waiting for the transmission of the packet B1 to be ended, so that a call collision occurs.

Each of the housing information boards 12-1 and 12-3 detects a collision by a collision detection circuit (see reference numeral 5 in FIG. 3),
Transmission is stopped, slot times TA1 and TC1 are set respectively, and retransmission is performed after the slot time has elapsed. When the slot time TC1 is shorter than the slot time TA1, the house information board 12-3 first retransmits the packet C1-2. On the other hand, the housing information board 12-1 retransmits the packet A2-2 after waiting the transmission end of the packet C1-2 because the control bus 11 is already in use when the slot time TA1 ends and the retransmission is attempted. . As a result, the retransmission of the packets C1-2 and A2-2 is successful.

Next, a method of setting the slot times TA1 and TC1 will be described.

The slot time T is calculated using the cycle t of the transmission reference clock signal and the device address.

For example, in the case of slot time TA1, when using decimal four-digit (a3, a2, a1, a0) as address a of housing information board 12-1, TA1 = t × (a3, a2, a1, a0) Become. Here, if the transmission rate is 200 baud, the period t
Is 5 ms, the maximum value Tmax of the slot time TA1 is Tmax = 5 (ms) × 9999 = 49995 (ms). In this case, the slot time is too long and the transmission efficiency is poor.

Therefore, in this embodiment, the address (a3, a2, a
Use 2 digits out of 1, a0). Then, the slot time T1 at the first retransmission is T1 = t × (a1, a0). If a call collision occurs in the first retransmission, the combination of multipliers is changed and the slot time T2 for the second retransmission is T2 = t × (a2, a1). Similarly, the slot time T3 at the time of the third retransmission is set as T3 = t × (a3, a2). In this way, by changing the combination of multipliers and sequentially changing the slot time and performing retransmission, it is possible to reliably avoid a call collision.

FIG. 5 is a flowchart showing the call collision avoidance method as described above. For example, in FIG. 1, packet B1
If there is a transmission request from the housing information boards 12-1 and 12-3 during the transmission of (step 100), the line busy is managed in each of the housing information boards 12-1 and 12-3 (step 101), On condition that the line busy is off and the slot time has ended (step 102), 1-bit data is transmitted (step 103). When the collision between the packets A2-1 and C1-1 is detected (step 104), the process proceeds to the retransmission step 105, and the steps 101 to 104 are performed again. When retransmitting the packets C1 and C2, there is no collision, so the transmission ends (step
106), the transmission ends (step 107).

As described above, in the present embodiment, when a call collision occurs, the retransmission is performed using the slot time T obtained by multiplying the transmission reference clock signal by the device-specific address that is a multiplier thereof. It is possible to accurately avoid time call collisions. Moreover, since the transmission reference clock signal is used to calculate the slot time T, the multiplication is easy and the slot time T without timing deviation can be accurately obtained. Here, when the number of digits of the address is large and the slot time is long, the transmission efficiency can be improved by shortening the slot time by using a part of the address. At this time, if some combinations of the addresses are sequentially changed for each retransmission, call collision can be surely avoided. Therefore, as a whole, it is possible to expect access with good transmission efficiency and quick response.

In addition, in the above-mentioned embodiment, the housing complex management system that requires a low speed line and quick response is described, but it is needless to say that the present invention is not limited to this and can be applied as another local network access method. Absent.

(Effects of the Invention) As described in detail above, according to the present invention, the slot time is calculated by multiplying all or part of the unique address assigned to each device by the transmission reference clock signal, and calculating the slot time. Since the retransmission order is determined by using the slot time, it is possible to appropriately avoid the call collision at the time of retransmission as compared with the conventional method of setting the slot time by a random number. Moreover, since the slot time is calculated using the transmission reference clock signal, the multiplication is easy and the slot time with no timing deviation can be accurately obtained. Also,
When the number of digits of the address is large and the slot time is long, the transmission efficiency can be improved by using a part of the address to shorten the slot time. At this time, if some combinations of addresses are sequentially changed at the time of retransmission, call collision can be surely avoided. Therefore, it is possible to provide an access method which has good transmission efficiency and bus usage efficiency and is responsive.

[Brief description of drawings]

FIG. 1 is a time chart for explaining a call collision avoidance method according to an embodiment of the present invention, FIG. 2 is a configuration diagram of a conventional local network, FIG. 3 is a configuration block diagram of devices in FIG. FIG. 4 is a block diagram of an apartment house management system according to an embodiment of the present invention, and FIG. 5 is a flow chart at the time of transmission in FIG. 1 ... Transmission path, 2,2-1 to 2-N ... device, 3 ... transmitter, 4 ... receiver, 5 ... collision detection circuit, 6 ... control circuit, 11 ... control bus, 12-1 to 12-N ... Housing information board,
13 …… Common entrance board, 14 …… Centralized monitoring board.

Claims (3)

[Claims] 1. A plurality of devices having the same function, which are connected to a transmission line by a bus, detect the presence / absence of transmission of another device when transmitting / receiving a packet, and perform transmission on condition that there is no transmission,
In the case of a transmission collision between each device, in a method of avoiding a call collision of a local network in which transmission is stopped and waiting for a predetermined slot time, and then a retransmission is performed, in the case of a transmission collision between the respective devices, those devices are attached. All or part of the unique address is multiplied by the transmission reference clock signal to calculate the slot time, the retransmission order is determined by using the slot time, and the retransmission is performed. Collision avoidance method. 2. The local network according to claim 1, wherein a part of the unique address assigned to the device is changed in combination for each retransmission, the slot time is calculated, and the retransmission order is determined. Call collision avoidance method. 3. The method for avoiding a call collision of a local network according to claim 1 or 2, wherein the device is a housing information board provided for each dwelling unit in an apartment house management system.