JPS6167347A - Scrambling system of dispersed type communication channel - Google Patents

Abstract

PURPOSE:To surely a channel with less numbers of procedures and packets, by multiply addressing an inhibit packet prior to other packets, when a channel being used exists in a multiply addressed module. CONSTITUTION:When a communication request is made, a calling module 2 sends a communication requesting packet 21 addressed to a called module 3 to a bus 1. The called module 3 selects a communication channel which is judged to be a vacant channel by the module 3 itself and transmits a channel use declaring packet 22. The other modules 4-6 judge whether or not the channel designated by the declaring packet 22 is used. When it seems that interruption is made to a channel being used by one module, the module transmits an inhibit packet 23 prior to other packets. The called module 3 again starts vacant channel retrieval upon receiving the inhibit packet 23.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a distributed communication channel contention system in which all modules perform communication channel management rules in a distributed manner.

<Prior Art> In a local area network such as a home bus system, there are a plurality of communication channels, and it has been proposed that the contention and management of these channels be performed using a control channel.

Control channels are slow and handle only short-term control signals (device on/off, operation requests, responses, commands, stops, etc.). A communication channel is a high-speed signal that cannot be sent on a control channel.

Handles large amounts of information, such as voice and audio.

Used for transmitting video and other high-speed data.

There are broadly two methods for managing contention for communication channels. One type is called a centralized system, in which communication channels are managed by a single management module (such as a central home computer). This has the advantage that communication channel management for each module is unnecessary or very simple. The second type is called the distributed type, in which all modules manage the communication channel in a distributed manner.In the distributed type, there is no need for a management module that requires high reliability, and at least one pair of calling module and one receiving module are used. If the call module is alive, communication is possible between them.

By the way, when transmitting data using any one of multiple communication channels, it does not mean that each module can use any channel at will, but it must claim the right to use that channel in some way. death,
It is necessary to secure it.

The system according to the present invention performs the above series of link operations in a distributed manner by transmitting packets on a control channel,
After the link is established, data can be freely sent and received through the secured communication channel, and the communication channel can be used independently. In, Japanese Patent Application No. 59-54777 (Patent Application No. 2 dated March 21, 1980, title of the invention "Data Transmission System"), Japanese Patent Application No. 1983
No. 9-64407 (patent application 1 dated March 30, 1980, title of invention "data transmission system") and patent application No. 112/1982
No. 738 (patent application 1 dated May 31, 1980, title of invention "Broadband channel competition system"), 3
We proposed two methods.

<Objective of the Invention> The present invention is different from any of the three methods described above, and can be expected to utilize channels more effectively and secure channels with fewer procedures and packets.

A feature of the present invention is that, as a method for selecting channels to be used, each module registers the channels to be used in memory each time it receives a broadcast notification for consultation about channel usage, and registers the channels to be used by itself. If you want to do this, you can select an empty channel from memory in advance, so-called history.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a diagram showing an example of a system configuration to which this method is applied. In the figure, 1 is the transmission line that makes up the network (bus). For example, in a home bus system, it is noteworthy that the coaxial cable of the TV common listening line is used, which has broadband transmission characteristics and does not require wiring work. . In this case, a frequency division method is appropriate as a multiplex transmission technique. Then, a baseband in a low frequency range is assigned as a control channel, and a broadband in a high frequency range is assigned to each communication channel.

However, as a transmission medium, wireless media such as weak radio waves and infrared rays, wired media such as coaxial cables, twisted pair wires, and optical fiber cables are also possible, and if each module can access multiple channels, Frequency division (FDM).

Either time division (TDM), space division (having communication lines equal to the number of channels), etc. may be used.

2 to 6 are modules connected to the network (bus) 1 in a multi-lock manner. FIG. 3 shows an example of the configuration as a transmitting station, and FIG. 4 shows an example of the configuration as a receiving station. Figures 3 and 4 use a frequency division method consisting of baseband and broadband, and each module 2 to 6
may have both such transmitting and receiving functions, or may have either one of the functions.

In FIGS. 3 and 4, reference numeral 11 is a control unit for controlling transmission, and has a memory function for storing channel usage status. Reference numeral 12 denotes a baseband transmitter for transmitting packets, which performs appropriate line contention such as C8MA/CD when transmitting packets. 13 is a baseband receiver for receiving packets. 14 (FIG. 3) is a modulation transmitter for transmitting high-speed data on a set channel, and 15 (FIG. 4) is a demodulation receiver for receiving high-speed data on the same channel.

FIG. 1 shows a flowchart explaining the operation, and FIG. 5 shows a time chart explaining an example of packet transmission. To simplify the explanation, it is assumed that module 2 is the calling module on the side that requested a call, module 3 is the called module on the side that requested the call, and modules 4 to 6 are other modules.

When a communication request occurs, the calling module 2 first sends a communication request packet 21 addressed to the called module 3 to the network (bus) 1 via the baseband transmitter 12 . When the called module 3 receives the packet 21 via its baseband receiving section 13, it decodes the packet data since it is addressed to itself. The other modules 4 to 6 are not addressed to you, so they are either skipped or ignored even if they are decoded.

The called module 3 decodes the packet data and determines whether it can respond or not. If no response is possible, do nothing. or Do Not Disturb (NAC) if necessary.
Send the packet back. If the response is possible, the channel use declaration packet 22 is sent to all modules, including communication channels that the control unit 11 determines to be empty, by looking at the memory contents in the control unit 11. When the message packet 22 is received, the other modules 4 to 6 determine whether or not the channel that was previously used and is currently in use is not currently in use for some reason. In the unlikely event that
When a channel in use by itself is about to be interrupted, the corresponding module sends out a prohibition packet 23 with priority over other packets.

This prohibition packet 23 is also a relay packet addressed to all modules. If the channel is not currently in use, the channel usage status table (memory contents of the control unit 11) is updated.

When the called module 3 receives the prohibition packet 23, it searches for an empty channel again by referring to the table. If there is an empty channel, channel usage speculation is performed again using the relay packet 22. If there is no empty channel, nothing will be done.

The calling module 2 that requested the communication sends the broadcast Daigon packet 2.
2, and if a prohibition packet 23 does not follow within a predetermined period of time, communication via that channel becomes possible. The channel used by the called module is usable, and calls and communications (high-speed data transmission via a broadband channel) are performed via the modulation transmitter 14 and demodulator receiver 15 of the other party.

The termination packet 24 is sent to the calling module 2. It can be sent from any of the called modules 3, and when it is sent or received, the channel is released and communication is terminated. This end packet 24 is also a broadcast packet addressed to all modules, and when the other modules 4 to 6 receive the end packet 24 by broadcast, they update the channel usage status table to the original state.

FIG. 6 shows the timing when two packets are transmitted successively.

In the figure, 40 is a packet from a certain module, and 41 is a packet from another module that has been instructed to start transmission during the T2 period. ζThis indicates that the next packet 41 will not be sent until at least T, 1% period after the previous packet 40 ends. Furthermore, even after the T1 period, depending on the type of module and the type of signal, αTO (number of connections where α≧0)
Only later can the packet 41 be sent out.

If two or more modules issue a command to start transmitting within the T2 period, those packets will start transmitting almost simultaneously after time 1o, so at that time both packets 7)
The question is how much α is. If α is different, the packet with the smaller α can be sent first, and the packet with the larger α has to wait for transmission again. A collision occurs when α is the same. That is, α is a factor that determines the priority of packets in bus contention, and the smaller α is, the higher the priority is. T1 is a period provided to completely separate packets.

After receiving the declaration packet 22, it must be sent out with priority over other packets. There is a possibility that priority transmission packets, text packets, and other packets unrelated to the series of operations will interrupt, which will impede channel contention operations. The highest priority is α=0 in Figure 6.
This is a packet sent immediately after time T. However, this time T1 is simply a time for distinguishing between packets, and making it too large will only allow the baseband to judge whether it is in use or not. In the unlikely event that the packet dies during use, the prohibited packet 2 will be given priority over other packets.
In addition, in the called module 3, channel 23 appears frequently, it takes time to acquire the channel, and the usage efficiency of the control channel decreases due to an increase in the number of packets (other (increases the possibility that valid packets will be left waiting)
There is a drawback.

Assuming that the probability of using one channel is Pl, if the channel selection of the called module 3 is performed at random, the probability that a prohibition packet will be issued is Pl. On the other hand,
Assuming that the table is referenced and the probability that this table is erroneously left unused is P2, the probability that a prohibited packet will be issued is P1×P2. P2 is when the table is not normal due to a runaway, or just after powering on only that module, and 0 <P2 <:
It is expressed as pl<1. That is, P+ ×P2 <p
If the called module 3 searches for an empty channel in advance by referring to a table as in the method of the present invention, the occurrence of prohibited packets can be suppressed as much as possible, and the above-mentioned drawbacks can be eliminated. It is very effective.

By the way, in the above-mentioned Japanese Patent Application No. 59-64407, the applicant proposed a system in which the calling module 2 side selects a channel to be used and sends a packet containing this channel as data to all modules. In this case, only when a non-permission response is not received within a predetermined time, it is assumed that the right to use the channel has been acquired, and a communication link with the desired called module 3 is established.

However, in the system of this application, one channel that employs the above-mentioned history storage type module is placed in a bundled state. On the other hand, when the called module 3 sends the channel message as in the present invention, it starts when the called module 3 responds to the communication request from the calling module 2.

That is, in the system of the present invention, the channel is not in a bundled state during the time from when a call is made to when a call is answered, and the channel can be used effectively during this time.

For example, when the called party responds to a call, the time it takes is relatively short if it is automatic, but if it is a telephone that calls the other party with a bell or the like and waits until the user responds, it takes a very long time. Sometimes it takes a long time. The present invention can operate efficiently even in the latter type of use.

Module 2 When f[llI declares the use of a channel, it has to be released, which is wasteful; the number of steps and packets increases.

If you make a declaration and do not receive a disapproval response within the specified time,
Assuming that the right to use the channel has been obtained, a communication link with the desired called module 3 is established. However, at this point, either there is no response to the called call, or the calling module 2 must make a new channel abandonment declaration.

In the method of the present invention, the called module 2 declares the use of the relaxed channel only when it is possible to make calls and communicate. If call/communication is not possible, do nothing or cancel NA at the first step when the called module 2 requests communication.
This is done by returning C. In other words, the method of the present invention can reduce the number of channel packets. However, after the call ends, the termination method is the same.

<Effects of the Invention> As described above, according to the present invention, it is possible to provide a useful distributed communication channel contention method in which channels can be used effectively and channels can be reliably secured with fewer procedures and packets.

[Brief explanation of drawings]

FIG. 1 is a 70-chart explaining the operation of an embodiment of the present invention, FIG. 2 is a diagram showing an example of a system configuration, FIG. 3 is a transmitting station configuration diagram, FIG. 4 is a receiving station configuration diagram, and FIG. The figure is a time chart illustrating an example of packet transmission, and FIG. 6 is a tie chart illustrating an example of priority transmission of packets. Tonenote work (path), 2 to 6 ・Module usage command bucket, 23...Prohibited packet. Agent Patent attorney Aihiko Fukushi (and 2 others) (4-stage presentation) (7-screen presentation) (34-J) WE1 Leap, Figure 2, Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. In a device in which communication channels are managed in a distributed manner by all modules by sending and receiving packets on a control channel, when there is a communication request from a calling module, if the called module is able to respond, By broadcasting, it declares the use of a channel that it determines to be an empty channel based on history storage, and if the channel is in use in the broadcasted module, it broadcasts a prohibited packet in priority to other packets. A distributed communication channel contention method characterized by: