JPS59131241A - Transmission system of carrier detection data - Google Patents

Abstract

PURPOSE:To prevent an interruption of data transmission due to an intervention of another terminal during the communication between terminals, by transmitting continuously a dummy pattern after a transmission signal until a fixed interval of time elapses after the transmission signal is transmitted through a transmission terminal and then an answer signal arrives. CONSTITUTION:A terminal 12 gives a call and sends a transmission packet 21 to a terminal 13, and the packet 21 is detected for the answer signal of the terminal 13. During this period, a dummy pattern 24 is continuously transmitted. The terminal 13 also transmits the pattern 24 until the transmitted answer signal is detected. Thus a communication signal always exists on a transmission line during a session since the transmission of dummy pattern is discontinued after the answer signal is confirmed. This avoids an interruption of data transmission owing to an intervention of another terminal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a contention control method for a network called a broadband network of a local area network, and in particular a C3MA
(Carrier 5ense Multiple A
ccess (carrier detection) data transmission system.

[Description of prior art]

In local area networks, it is common practice to have each terminal perform various network functions such as switching functions. As a distributed processing network like this,
CSMA/CD (CarrierSense
Multiple Access/Golli
A baseband network based on a detection algorithm is well known. This C3MA
/In the Heath Hand network using the CD algorithm,
Collision of transmitted signals occurs when multiple terminals start transmitting at the same time, but this collision can be easily detected by all terminals on the network. However, in broadband networks, compared to baseband networks, the difference in the level of the transmitted signals due to the difference in distance between terminals is large, and the collision detector traps signals with high levels, so collision detection is difficult. becomes difficult. Therefore, in a broadband network, the C3MA algorithm is used, although the efficiency of line use with respect to the traffic of the transmitted signal is slightly inferior compared to the case where collision detection is performed.

Conventionally, communication between terminals using the C3MA algorithm in a broadband network is as follows.

That is, a plurality of terminals are connected to a communication cable such as a coaxial cable or a pair cable, and this communication cable is used as a bidirectional transmission line by frequency band division. Furthermore, each terminal is equipped with a detector that detects the presence or absence of a signal in the receiving band or the transmitting/receiving band on this bidirectional transmission path. When communicating between terminals, each terminal shares and uses this bidirectional transmission path. The calling terminal first assembles the outgoing signal into packets of a certain length. Next, as soon as the detector detects that no signal exists on the transmission path, the packet is sent out. When a signal exists on the transmission path, it waits until the signal no longer exists before transmitting it.

According to this method, when a plurality of packets are conversationally exchanged between transmitting and receiving terminals, there is a time when no signal is present on the transmission path between the transmitted packet and the received packet. If another terminal starts transmitting at this time and monopolizes the transmission path, one session is interrupted, and therefore the time spent on one session becomes longer. Such a time delay may be disadvantageous in terms of network performance.

In other words, this is the case with a circuit-switched signaling channel using FDMA (Frequency Division Multiple Access) in a broadband network. In addition, this reference document is Information Network 7) Work Study Group Materials 15-82-28 Sabado et al. ``A Study of Broadband Local Area Networks.''

[Purpose of the invention]

The present invention solves the above-mentioned drawbacks and the conventional C3
It is an object of the present invention to provide a carrier wave detection data transmission system that can eliminate division of one session and prevent an increase in communication time by only slightly changing the formers 1, 1 of transmission signals of an MA algorithm.

[Features of the invention]

The present invention configures a bidirectional transmission path by dividing a coaxial cable or bare cable into frequency bands, connects a plurality of terminals to the cable, and shares the transmission path for communication between the terminals. In a network in which each terminal is equipped with a detector that detects the presence or absence of a signal in the reception band, or a signal in the transmission band and reception band, and each terminal can transmit only when it detects the absence of a signal,
The present invention is characterized in that the transmitting terminal continues to transmit the dummy pattern in succession to the transmitted signal even after transmitting the transmitted signal until a certain period of time has elapsed since the response signal from the other terminal began to arrive.

[Explanation based on examples]

Embodiments according to the present invention will be described below based on the drawings.

FIG. 1 is a block diagram of the first embodiment of the present invention, showing the simplest broadband local area network model.

In FIG. 1, the coaxial cable 14 has two terminals 12.
．． 13 is connected, and the frequency converter 11 is also connected. Although not shown, this coaxial cable 1
A large number of other terminals are connected to the terminal 4, and communication using the C3MA data transmission method is performed between each terminal. Each terminal then sends out a signal in a packet format as shown in FIG. The sending bucket 21 in FIG. 2 includes a synchronization pattern 22 called a preamble and an information pin I/23 sent out for exchanging communication data.
and a dummy pattern 24, which is a feature of the present invention.

Note that the signals sent from the terminal 12 are distinguished by the subscript 12, and the signals sent from the terminal 13 are distinguished by the subscript 13.

To explain the operation of this first embodiment method, now the terminal 12
Assume that the terminal 13 calls the terminal 13 and sends out the sending packet 21□2. The terminal 12 receives this sending packet 2
112, the dummy pattern 2412 was continued to be sent, and it was confirmed that the synchronization pattern 2213 of the response signal from the terminal 13 had arrived. Afterwards, sending out the dummy pattern 2412 is stopped.

On the other hand, the terminal 13 also uses the dummy pattern 24 of the response signal until it is confirmed that the response signal from the terminal 12 has arrived in response to the response signal sent from the own station.
13 continues to be sent, and after confirmation, stops sending. Thereafter, they communicate with each other using the same procedure.

According to such a procedure, the end of the dummy pattern 24 of one terminal overlaps the beginning of the synchronization pattern of the other terminal on the transmission path, and during one session, the communication signal is not transmitted on the transmission path. exists without interruption. Therefore, even if the C3MA algorithm is used, it is possible to perform communication without the transmission path being taken by another terminal (that is, without being interrupted during one session by the intervention of another terminal).

Dummy pattern 24 in the format of the sending packet 21
To add , use the following method. In other words, since it has been conventional practice to attach a pattern indicating the end of a bucket to the end of a packet, it is possible to change the pattern or focus number of the pattern indicating the end of this packet to make it a dummy pattern, or to change the pattern indicating the end of this packet. This can be easily realized by adding a dummy pattern after the pattern indicating the end.

FIG. 3 is a block diagram of the process according to the embodiment shown in FIG. 2 of the present invention, and illustrates the case of circuit-switched signaling transmission in a broadband local area network.゛In Figure 3, coaxial cable 3
6 is connected to an exchange 31 and terminals 32 to 35, and each terminal is connected to C3 in the bucket format shown in FIG.
It is configured to perform MA data communication.

Next, the operation of this second embodiment system will be explained.

When the terminal 32 wants to communicate with the terminal 33, the terminal 32 calls the exchange 31 and communicates with the terminal 3 via the exchange 31.
A method is adopted in which a communication pulse is set between 3 and 3.

In such a case, when one connection request is made to the exchange 3I, the exchange can be simplified by completely processing that one call before accepting the next connection request. Therefore, it is necessary to control the generation of connection requests so that the exchange only needs to process one connection request at any time.

Assume now that the terminal 32, after confirming that no signal exists on the transmission path, issues a connection request to the exchange ta31. The packet and software format 7 at this time are the same as those shown in FIG.
The time chart of packet transmission during the three periods is as shown in FIG.

In FIG. 4, the sending Pakeso I 2132 sent from the terminal 32 at time t1 consists of a preamble 2232, an information pick I 2332, and a dummy pattern 2432.
This sending packet 2132 arrives at the exchange 31 at time t2 after a certain delay time has elapsed. exchange 31 terminal 32
While the dummy pattern 2432 continues to be input, the received bucket is sent out as a sending packet 2131 to the terminal 33 via the coaxial cable 34.

While the dummy pattern 2431 of the sending packet 2131 is being sent on the coaxial cable 36, the terminal 32 sends out the next sending packet I.2+32'.

Now, the length of the preamble 2232.2231.2232' is preamble length - synchronization pull-in time at the exchange or terminal + (propagation delay time between the farthest terminal and the exchange) x 2 + guard time T1, T2, T3, and dummy Pattern 2432.2431.2432'
The length of is the dummy pattern length - processing time at the exchange or terminal T4
, T5, T6 + (propagation delay time between the farthest terminal and the exchange) x 2 ten guard times T1, T2, T3. Here, the guard time refers to the time during which the preamble length and the dummy pattern overlap. When the preamble length and dummy pattern length are set in this manner, as shown in FIG. 4, there is no possibility that the signal will be lost on the transmission path, that is, at the reception input time t2 of the exchange 31.

Therefore, by using the conventional C3MA/CD algorithm as is, when a connection request is made from one terminal, the transmission path will not be taken by another terminal until the connection procedure is completed. It is possible to exclusively allocate a transmission path to a terminal requesting connection and a terminal requesting connection.

〔Effect of the invention〕

As described above, according to the present invention, one session of communication between terminals is not interrupted by intervention of another terminal, and the time required for communication can be shortened.

Furthermore, since the connection caused by a single call is no longer interrupted midway, the configuration of the exchange can be simplified. Moreover, since the present invention can be implemented by only making some changes to the conventional packet format, it is only necessary to make some changes to the configuration of the conventional device, which is economical.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a system according to a first embodiment of the present invention. FIG. 2 is a diagram showing a transmission packet format. FIG. 3 is a block diagram of a system according to a second embodiment of the present invention. FIG. 4 is a time chart of packets sent between the exchange and the terminal. 11...Frequency converter, 12.13.32.33.3
4.35...Terminal, 14.3G...Coaxial cable,
21... Sending packet 7), 22... Preamble, 2
3... Information bit, 24... Dummy pattern, 31
···switch. Patent applicant NEC Corporation Representative Patent attorney Takaaki Ide 1 Figure 1 Ara 2 Mouth

Claims (1)

[Claims] (ll) A plurality of terminals are connected to a communication cable, and this communication cable is made into a bidirectional transmission path by frequency band division and is shared by each of the terminals, and communication between these terminals is , each terminal starts transmitting when a detector for detecting the presence or absence of a communication signal provided in each terminal detects that no communication signal exists on the bidirectional transmission path. Carrier detection data transmission system configured as follows: The transmission signal transmitted from each transmitting terminal is configured such that a dummy pattern is added after the information bit, and this dummy pattern is used to transmit signals until the communication by the transmitting terminal ends. A carrier wave detection data transmission method characterized by being configured to be transmitted continuously during blank time. (2) Each transmitting terminal transmits a dummy pattern after sending a transmission signal until a response signal from the other terminal is detected. The general transmission detection data transmission method according to claim 1i, characterized in that the transmission path is monopolized by continuous transmission. (3) The dummy pattern length is set to a specified value. The carrier wave detection data transmission system according to claim 1, characterized in that the carrier wave detection data transmission system is configured to exclusively occupy a transmission path by increasing the length of the carrier wave.