JPH03270432A - Local area network - Google Patents

Abstract

PURPOSE:To transmit data while selectively using a bus corresponding to the kind of a signal by connecting all nodes with the bus according to the protocol of a line scrambling system and the bus according to a time dividing system. CONSTITUTION:All nodes 4 are connected to a bus 1 according to the protocol of the line scrambling system and a bus 2 according to the time dividing system. In the bus of the time dividing system, even when transmission requirement is present from the plural nodes 4, a transmittable period at a prescribed short cycle can be presented to those nodes 4. Therefore, the signal such as a sound signal or a moving image signal, etc., requiring real time property can be transmitted as well. Thus, the signal can be transmitted while selectively using the bus corresponding to the kind of the signal such as transmitting the data signal requiring no real time property by using the bus of the lien scrambling system or transmitting the sound signal or the moving image signal, etc., to required the real time property by using the bus of the time dividing system.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to working with data signals, audio signals, and video signals.

[Conventional technology]

Generally, in a communication network, it is determined what kind of transmission control procedure (hereinafter referred to as "protocol") is to be used when transmitting and receiving signals. Typical protocols employed in conventional local area networks include the line contention method. Figure 4 shows a line contention type local area network. In FIG. 4, l is a bus and 4 is a node. The bus 1 is composed of coaxial cables, twisted bare cables, and the like. Node 4 is
These include computers, workstations, terminals, etc. To transmit from node 4, a packet is sent to bus I with the address of node 4 to which information is to be transmitted. Although the packet is transmitted to nodes 4 other than the destination, reception processing is performed only at the node 4 specified by the above address. In order to perform the above-mentioned transmission, it is first necessary to reserve bus 1 for exclusive use. This is because, if signals from a plurality of nodes 4 were sent to the bus 1 at the same time, the signals would be mixed together and none of the signals would be present. In local area networks based on line contention, this bus 1 is secured on a first-come, first-served basis. That is,
In order to secure the line, each node 4 competes for the line. Once you win the battle and secure the line, you can start transmitting for the first time. C3D as a line contention protocol? l/CD
(Carrier 5ense Multiple A
ccess / Co11isionDetectjio
n), and a specific example of a local area network built using it is ``Ethernet'' by Xerox Corporation in the United States. According to this method, the bus I is used without wasting time, so it is suitable for communication of data signals. Furthermore, this method has the advantage that the network can be easily expanded or reduced because nodes can be added or removed without requiring troublesome modifications to other parts.

[Invention tries to solve! l! ! 11 (Problem) However, the conventional local area network described above has a problem in that it is not possible to transmit audio signals and video signals without problems. (Description of the Problem) In recent years, there has been a demand for so-called multimedia local area networks that can transmit not only data signals but also audio and video signals. As mentioned above, contention local area networks are suitable for transmitting data signals. However, it cannot be said to be suitable for transmitting audio signals or video signals for the following reasons. Once audio and video signals start being transmitted,
Unless at least a predetermined amount of signal (such as several kilobits) is sent before a predetermined short period of time has elapsed, the audio and video will not be smooth. That is, after the start of transmission, real-time performance is required in which signals can be continuously sent without interruption so that the movement of audio and video does not become unnatural. However, in local area networks based on line contention, even if transmission begins, the bus may be taken over by another node midway through, and it is not known when the bus will be regained, so real-time performance cannot be guaranteed. Not done. Therefore, the transmission of audio signals and video signals may be hindered. The present invention aims to solve such problems. [Means for Solving the Problems] In order to solve the above problems, the local area
The network follows a contention protocol1.
one line contention bus, one or more time division buses that follow a time division protocol, and a bus control device provided corresponding to each of the time division busses and connected to all of the buses. and a plurality of nodes connected to all of the buses, and transmission using the time division bus is performed by sending a transmission request to the bus control device through the line contention bus. did.

[For production]

In the present invention, all nodes are connected to a bus that follows a contention type protocol and a bus that follows a time division type protocol. In a time-division bus, even if there are transmission requests from a plurality of nodes, it is possible to provide these nodes with a transmission possible period at a predetermined short period. Therefore, even signals that require real-time performance, such as audio signals and video signals, can be transmitted. Therefore, data signals that do not require real-time performance are transmitted using a line contention bus, and audio and video signals that require real-time performance are transmitted using a time-division bus. Accordingly, it is possible to use different buses for transmission. As a result, in the local area network of the present invention, it becomes possible to transmit not only data signals that do not require real-time performance, but also signals that require real-time performance without any problems.

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. (First Embodiment) FIG. 1 shows a local system according to the first embodiment of the present invention.
Shows an area network. In FIG. 1, ■ is a bus that follows a line contention protocol, 2 is a bus that follows a time division protocol, 4 is a node, and 5 is a bus control device. The bus control device 5 is a device that controls the use of the bus 2, and uses a slot generator, for example. Bus 1.
2 can be constructed from a coaxial cable or a twisted wire pair. Each node 4 and bus controller 5 is connected to both buses 1.2. In the present invention, the line contention type bus 1 is mainly used for transmitting data signals, and the time division type bus 2 is used mainly for transmitting audio signals and video signals, which are signals that require real-time performance. Transmission using the line contention type bus 1 is performed in the same manner as in the conventional example shown in FIG. 4, so a description thereof will be omitted. In the time division method, time is divided into fixed short periods called time slots, which are periodically allocated to nodes 4 that have issued transmission requests. Node 4 can only transmit during the time slots assigned to it. The bus control bag f5 issues a signal to control which node 4 is assigned a particular time slot. FIG. 5 is a diagram illustrating time slots in the time division system. In FIG. 6, 7 is a bus control signal, 8 is a node signal, and T is a time slot. The bus control device 5 generates one bus control signal 7 for each time slot. Each bus control signal 7 includes a message specifying a particular node 4. All nodes 4 receive this bus control signal 7, but
Only the node 4 specified in the message is allowed to transmit within that timeslot time. The signal transmitted from node 4 is node signal 8. Therefore, since each node 4 can send out signals one after another in a short cycle, real-time transmission can be achieved. If the node 4 wishes to transmit using the time-sharing bus 2 as described above, it transmits the request to the bus control device 5 through the bus 1. That is, the transmission of the transmission request is
This is done after acquiring the right to use Bus 1. Upon receiving the transmission request, the bus control device 5 issues a bus control signal 7 containing a message permitting the node 4 to transmit. This allows the node 4 to transmit audio signals and video signals. In the bus 2, once transmission starts, time slots continue to be allocated at predetermined short intervals until the transmission ends, so real-time transmission is maintained. If another node 4 sends a transmission request to the bus controller 5 while the node 4 using the bus 2 is transmitting, the time slot not currently being used for transmission is used by the new node 4. assigned to. Therefore, it is possible to transmit from multiple nodes 4 simultaneously. Next, specific examples of time slots will be explained. If τ is the time required for a signal to propagate round-trip across the entire bus (i.e., the signal's "maximum round-trip propagation delay time J"), τ is determined by the thickness of the bus network (no matter how large the network is) (For example, τ is also large), but in order to be able to send meaningful signals during the period of ■ timeslots, it is necessary to set the time slot length T to be sufficiently larger than τ.For example, , when τ = 50 μsec, T -5001 sec, etc. If Tm2O3 μsec, one second is divided into 2000 time slots.The first node making the transmission request has 20 time slots, 50 slots are assigned to the second node, and so on.Which time slot is assigned to the second node is determined by
Indicated by bus control signal 7. Time division bus 2 clock rate is 100Mbps
(bit per 5econd), duration 50
If the time available for transmitting information in a 0 μsec time slot is 300 μsec, a 30,000-bit signal can be transmitted during one time slot (100xlO' x 300 xlO-' = 30,00
0). Therefore, a node to which 20 time slots are allocated per second can transmit signals at a speed of 600 Kbps, and can maintain sufficient real-time performance. 2
If zero time slots are distributed and distributed at equal intervals within one second, audio or moving images will be transmitted smoothly. (Second Embodiment) FIG. 2 shows a local system according to a second embodiment of the present invention.
FIG. 2 is a diagram showing an area network. The symbols correspond to those in FIG. 1, 3 is a bus, and 6 is a bus control device. The bus 3, like the bus 2 in FIG. 1, is a bus that follows a time division protocol. The bus control device 6 controls the bus 3
For example, a slot generator is used. In this embodiment, one more bus is added in order to increase the transmission capacity using a time-division bus. All nodes 4 and bus controllers 5.6 are connected to bus 1.
2.3. When a transmission request is made using a time division bus, the transmission request is transmitted from each node 4 to the bus control devices f5 and f6 via the line contention bus 1. A rule is established between the bus control devices W5 and W6 as to which one receives the reception first, and the bus on which the reception is applied is used. For example, one bus control device 5 may be set to accept the reception first, and when the corresponding bus 2 has reached its full capacity, the other bus control device 6 may accept the reception. I can do it. Furthermore, it may be determined in advance which bus control device will first accept a transmission request from which node. Even in this case, when one bus reaches its full capacity, the other bus is used. (Third Embodiment) FIG. 3 shows a local system according to a third embodiment of the present invention.
FIG. 2 is a diagram showing an area network. The symbols correspond to those in FIG. And 9 is a star coupler. This embodiment is applied to a star-type network using optical communication, and two star couplers 9 correspond to buses 1.2 in FIG. 1, respectively.

【Effect of the invention】

As described above, in the local area network of the present invention, all nodes are connected to a bus that follows a line contention protocol and a bus that follows a time division protocol. In a time-division bus, even if there are transmission requests from a plurality of nodes, it is possible to provide these nodes with a transmission possible period at a predetermined short period. Therefore, even signals that require real-time performance, such as audio signals and video signals, can be transmitted. Therefore, in the local area network of the present invention, data signals that do not require real-time performance are transmitted using a line contention bus, and audio and video signals that require real-time performance are transmitted using a time-sharing bus. When transmitting signals, it is possible to use different buses depending on the type of signal. As a result, in addition to data signals that do not require real-time performance, it has become possible to transmit signals that require real-time performance without any problems. 5.6 is a hash control device, 7 is a slot generator signal, 8 is a node signal, and 9 is a star coupler.

Claims (1)

[Claims] One line contention bus that follows a line contention protocol, one or more time division buses that follow a time division protocol, and all of the buses provided corresponding to each of the time division buses. a bus controller connected to the bus controller, and a plurality of nodes connected to all the buses, the transmission using the time-sharing bus includes a bus control device connected to the bus controller, and transmitting a transmission request through the contention bus. A local area network characterized by transmitting information to a device.