JP2000106564A - Information transmission device and information transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the information transmission device and the information transmission system where congestion of information can be avoided while suppressing deterioration in the information transmission capability of the system. SOLUTION: A network interface section 11 of the information transmission device 1 has a collision detection section 21 and a collision counter section 22 and stops transmission of information when detecting collision of its own information with other information on a transmission line 3 after starting transmission of its own information to the transmission line 3 but continues transmission of the information when detecting no collision. The collision counter section 22 calculates number of times of collision nCOL per unit time. The number of times of collision nCOL is used for a parameter representing a degree of congestion of the transmission line 3. In the case that the number of times of collision nCOL is a prescribed number of times of collision nREF or over, an MPEG encoder 12 is controlled so that its output data rate is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a CSMA / CD.
(Carrier Sense Multiple Access / Collision Detectio
The present invention relates to an information transmission device for transmitting information in a method n) and an information transmission system including a plurality of such information transmission devices.

[0002]

2. Description of the Related Art In an information transmission system of the CSMA / CD system, when a plurality of information transmission devices constituting the system transmit information almost simultaneously, collision of information occurs.
Occurs, each information transmitting device detects whether or not the transmitted information collides with the information on the transmission line. If a collision occurs, the information transmitting device retransmits the information after the waiting time TWAIT. Here, the waiting time TWAIT is set to a value randomly selected from values that increase exponentially with respect to the number of retransmissions nRT in order to avoid the same collision from repeating.

The number N of retransmissions includes a maximum number of transmissions N
MAX is defined, and when N> NMAX, the information is discarded, and retransmission is not performed beyond the maximum transmission number NMAX. With such a mechanism, when information is congested on the transmission path, the amount of information transmitted on the transmission path is limited.

[0004]

However, in this system, since information cannot be transmitted at all during a collision, the information transmission capacity of the entire information transmission system is considerably reduced from the maximum capacity. There was a disadvantage.

The present invention has been made in view of this point, and provides an information transmission apparatus and an information transmission system capable of avoiding information congestion while suppressing a decrease in the information transmission capability of the system. The purpose is to:

[0006]

According to a first aspect of the present invention, there is provided an information processing apparatus, comprising: a transmission line connected to at least one information receiving apparatus; and transmitting information on the transmission line. A collision detecting means for detecting the presence or absence of a collision with the information on the transmission line when the collision occurs, stopping the transmission of the information when the collision occurs, and continuing the transmission of the information when the collision does not occur In the information transmitting device, a congestion degree detecting means for detecting a parameter indicating the degree of congestion of the transmission path, and a unit time for transmitting on the transmission path when the congestion degree is determined to be a predetermined level or more based on the parameter indicating the congestion degree. Control means for controlling so as to reduce the amount of information per hit.

According to a second aspect of the present invention, in the information transmitting apparatus according to the first aspect, the congestion degree detecting means counts the number of collisions per unit time detected by the collision detecting means. And detecting the number of collisions per unit time as a parameter indicating the congestion degree.

According to a third aspect of the present invention, in the information transmitting apparatus according to the first aspect, when the collision is detected by the collision detecting means, the transmission of the information is stopped.
Retransmission means for retransmitting the stopped information, wherein the congestion degree detecting means comprises retransmission counting means for counting the number of retransmissions per unit time by the retransmission means, and The number of times is detected as a parameter indicating the congestion degree.

According to a fourth aspect of the present invention, in the information transmitting apparatus according to the first aspect, the congestion degree detecting means includes an information amount measuring means for measuring an information amount per unit time flowing on the transmission path. , The amount of information per unit time is detected as a parameter indicating the congestion degree.

According to a fifth aspect of the present invention, in the information transmission system in which at least one information receiving device and a plurality of information transmitting devices are connected via one transmission path, the plurality of information transmitting devices include: When the transmission of information on the transmission path is started, the apparatus has collision detection means for detecting the presence or absence of a collision with the information on the transmission path.When the collision occurs, the transmission of the information is stopped, and the collision occurs. If not, the information is transmitted to another device by continuing to transmit the information, and at least one information transmitting device includes a congestion degree detecting unit that detects a parameter indicating the congestion degree of the transmission path, The information transmitting apparatus not having the congestion degree detecting means transmits a parameter indicating the congestion degree from the information transmitting apparatus having the congestion degree detecting means through communication via the transmission path. And acquiring control means for controlling the amount of information per unit time to be transmitted on the transmission path when the congestion degree is determined to be equal to or more than a predetermined value by a parameter indicating the obtained congestion degree. Features.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are diagrams showing a configuration of an information transmission system including an information transmitting device and an information receiving device according to an embodiment of the present invention. The system comprises a plurality of information transmitting devices 1 and one or more information receiving devices 2
And a transmission path (bus) 3 for interconnecting them, and information is transmitted via the transmission path 3 by the CSMA / CD method.

The information transmitting device 1 is connected to a transmission line 3,
A network interface unit 11 for controlling information transmission via the transmission path 3; and a moving picture experer (MPEG) for input video and audio signals.
t Group) standard, and an MPEG encoder 12 that performs encoding in accordance with the standard, and a CPU (Centra
l Processing Unit) 13, a memory 14 for storing data and programs being processed, and a bus 15 for interconnecting these components and transmitting data and control information.

The digital data encoded by the MPEG encoder 12 is transmitted to a bus 15 under the control of the CPU 13.
After being stored in the memory 14 via the interface and adding various headers, the data is supplied to the network interface unit 11. The network interface unit 11 transmits the input data to the information receiving device 2 via the transmission line 3 by the information transmission process of FIG.

The network interface unit 11
A collision detection unit 21 for detecting the presence or absence of a collision with the information on the transmission line 3 when the transmission of the information on the transmission line 3 is started, and a collision counting unit for counting the number of collisions per unit time And a retransmission counting unit 23 as a retransmission counting unit that counts the number of retransmissions performed per unit time performed on information in which a collision has occurred,
An information amount measuring unit 24 is provided as information amount measuring means for measuring an information amount per unit time flowing on the transmission path 3.

When the information transmitting apparatus 1 starts transmitting information, the collision detecting unit 21 detects that a collision has occurred when the transmitted information does not match the information on the transmission path 3. Specifically, the collision counting unit 22 calculates the number N of collisions occurring during the period TTR during which information transmission processing is being executed.
COL is counted, and the number of collisions (collision frequency) nCOL is calculated by converting the number of collisions NCOL per unit time. Further, the retransmission counting unit 23 specifically counts the number of retransmissions NRT executed during the period TTR during which the information transmission processing is being executed, and converts the number of retransmissions NRT into the number of retransmissions per unit time ( Retransmission frequency) nRT is calculated. Further, the information amount measuring unit 24 constantly monitors information flowing on the transmission path 3 and counts the number of packets NP transmitted within a certain time TC.
KT or the number of bytes NBYT is counted, and the value NPKT is calculated.
Or information amount IB obtained by converting NBYT per unit time
Calculate US.

The information receiving device 2 is connected to the transmission line 3,
A network interface unit 31 for controlling the reception of information via the transmission path 3; an MPEG decoder 32 for decoding digital data output from the network interface unit 31 into original video and audio signals; The system includes a CPU 33 for performing control, a memory 34 for storing data and programs being processed, and a bus 35 for interconnecting these components and transmitting data and control information. The information receiving device 2
The digital data stored in the packet received via the transmission path 3 is decoded into the original video signal and audio signal, and these signals are output to the display device 4.

FIG. 2 is a flowchart of the information transmission process executed by the network interface unit 11 of the information transmission device 1.

First, in step S11, it is determined whether or not the bus is in the idle state, that is, whether or not there is no information flowing on the transmission path 3. If not, the process waits until the idle state is reached. When it is determined that the vehicle is in the idle state, it is determined whether or not the number of collisions nCOL per unit time calculated by the collision counter 22 is equal to or greater than a predetermined number of collisions nREF (step S12). And nCOL
If <nREF, control is performed such that the average output data rate DR (bits / second) of the MPEG encoder 12 becomes the first value DR1 (step S13), and nCO
When L ≧ nREF, control is performed such that the average output data rate DR of the MPEG encoder 12 becomes a second value DR2 smaller than the first value DR1 (Step S).
14). Such control for reducing the output data rate DR is performed by deleting coefficients corresponding to high-frequency components obtained by, for example, transform coding performed by the MPEG encoder 12.

In the following step S15, transmission of a packet is started, and it is determined whether or not a collision has occurred on the transmission line 3 (step S16). If no collision occurs, the transmission of the packet is continued (step S30), and the transmission processing ends. On the other hand, when a collision occurs, transmission of information is immediately stopped (step S17), the retransmission counter CRT is incremented by "1" (step S18), and whether the value of the retransmission counter CRT exceeds the maximum number of retransmissions CRTMAX is determined. Is determined (step S19). Here, the retransmission counter CRT has been reset to "0" at the start of this processing.

If CRT≤CRTMMAX, the waiting time TWAIT is set according to the value of the retransmission counter CRT (step S20). Specifically, the retransmission counter C
One value is randomly selected from a plurality of predetermined values equal to or less than an exponentially increasing value as the value of RT increases, and is set as a waiting time TWAIT. This is performed to reduce the possibility of collision occurring again during retransmission.

In step S21, the process waits until the waiting time TWAIT elapses, and returns to step S11 when the waiting time TWAIT elapses. If the value of the retransmission counter CRT exceeds the maximum number of retransmissions CRTMAX in step S19, the packet subjected to the transmission processing at that time is discarded, and that fact is notified to the CPU 13 (step S40).

In this embodiment, when the transmission line 3 is congested (the amount of information flowing through the transmission line 3 is large), the number of collisions nCOL per unit time is increased, and Adopted as a parameter indicating the degree of congestion of the transmission line 3, and when nCOL ≧ nREF and the congestion degree is determined to be equal to or more than a predetermined value, the information amount (data rate) per unit time to be transmitted on the transmission line 3 is reduced. With this configuration, it is possible to avoid congestion of information in the transmission path 3 while suppressing a decrease in the information transmission capability of the information transmission system.

The present invention is not limited to the embodiment described above, and various modifications are possible. For example, in the process of FIG. 2, as a parameter indicating the degree of congestion of the transmission path 3,
Although the number of collisions nCOL per unit time is used, the number of retransmissions nRT per unit time may be used.
In this case, when the number of retransmissions nRT per unit time is equal to or greater than the predetermined number of retransmissions, control is performed so as to reduce the amount of information (data rate) per unit time transmitted on the transmission path 3.

The number of collisions per unit time nCOL
Alternatively, instead of the number of retransmissions nRT, the information amount IBUS per unit time measured by the information amount measuring unit 24 may be used as a parameter indicating the degree of congestion of the transmission path 3. In this case, the information amount I per unit time
When the BUS is equal to or larger than the predetermined information amount, control is performed so that the information amount (data rate) per unit time transmitted on the transmission path 3 is reduced.

As shown in FIG. 4A, the information transmitting apparatus 1a which does not include any one of the collision counting unit 22, the retransmission counting unit 23, and the information amount measuring unit 24, which constitutes the congestion degree detecting means, includes Information sending device 1 having degree detecting means
In an information transmission system including both (FIG. 1) (for example, a system as shown in FIG. 1B), the information transmission device 1a communicates via the transmission line 3 to transmit the information transmission device 1a.
Indicates the congestion degree of the transmission path 3 (the number of collisions n
COL, the number of retransmissions nRT, or the information amount IBUS), and when the congestion degree of the transmission line 3 is determined to be equal to or more than a predetermined value based on the acquired parameters, the amount of information transmitted to the transmission line 3 per unit time is reduced. It is desirable to control it. Here, the information sending devices 1 and 1a
(ManagementInformation Base),
When the information transmitting device 1a requests a parameter indicating the degree of congestion via the transmission path 3 to the information transmitting device 1 and transmits the parameter from the information transmitting device 1 to the information transmitting device 1a, an SNMP (Simple) Network Management Pr
otocl). SNMP is TC
P / IP (Transmission Control Protocol / Internet P
(rotocol) is a component of the protocol suite, and is a protocol in which five types of messages for extracting variable values and the like are defined. The MIB is a combination of variables that can be handled by each device constituting the system, and is based on a plurality of information bases such as a standard MIB specified as a part of SNMP and a company MIB uniquely defined by a manufacturer. It is configured.

In the above-described embodiment, the information transmitting device 1 includes all of the collision counting unit 22, the retransmission counting unit 23, and the information amount measuring unit 24. However, the present invention is not limited to this. , A retransmission counting unit 23 and an information amount measuring unit 24.

Further, in the above-described embodiment, the information transmission system including the information transmitting apparatus having only the information transmitting function and the information receiving apparatus having only the information receiving function has been described.
As shown in FIG. 4C, an information transmission / reception device 5 having an information transmission function and an information reception function, and an information transmission system including a plurality of information transmission / reception devices 5 may be configured.

[0028]

As described above in detail, according to the present invention, a parameter indicating the degree of congestion of a transmission path is detected, and when the congestion degree of the transmission path is determined to be equal to or more than a predetermined value based on the parameter indicating the degree of congestion, Since control is performed so as to reduce the amount of information per unit time transmitted on the transmission path, it is possible to avoid information congestion while suppressing a decrease in the information transmission capability of the information transmission system.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a main part of an information transmission system including an information transmission device according to an embodiment of the present invention.

FIG. 2 is a flowchart of an information transmission process executed in the information transmission device of FIG. 1;

FIG. 3 is a block diagram illustrating an overall configuration example of an information transmission system according to an embodiment of the present invention.

FIG. 4 is a diagram showing a modification of the embodiment shown in FIGS.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 information transmission device 3 transmission line 11 network interface unit (control means) 21 collision detection unit (collision detection unit) 22 collision counting unit (collision counting unit) 23 retransmission counting unit (retransmission counting unit) 24 information amount measurement unit (information amount) Measuring means)

Claims (5)

[Claims] 1. Collision detecting means connected to a transmission line to which at least one information receiving device is connected, and detecting the presence or absence of collision with information on the transmission line when starting transmission of information on the transmission line. An information transmitting apparatus for stopping transmission of information when the collision occurs and continuing to transmit information when the collision does not occur, wherein a congestion degree for detecting a parameter indicating the congestion degree of the transmission line is provided. Detecting means, and control means for controlling so as to reduce the amount of information per unit time transmitted on the transmission path when the congestion degree is determined to be equal to or more than a predetermined value based on the parameter indicating the congestion degree. Information transmission device. 2. The congestion degree detecting means includes collision counting means for counting the number of collisions per unit time detected by the collision detecting means, and the number of collisions per unit time is used as a parameter indicating the congestion degree. The information transmitting apparatus according to claim 1, wherein the information is transmitted. 3. When a collision is detected by the collision detecting means, the information processing apparatus further comprises: retransmission means for stopping transmission of the information and retransmitting the stopped information; And a retransmission counting unit for counting the number of retransmissions per unit time by the output unit, and detecting the number of retransmissions per unit time as a parameter indicating the congestion degree.
An information transmission device according to claim 1. 4. The congestion degree detecting means includes an information amount measuring means for measuring an information amount per unit time flowing on the transmission path, and detects the information amount per unit time as a parameter indicating the congestion degree. 2. The information transmitting apparatus according to claim 1, wherein: 5. An information transmission system in which at least one information receiving device and a plurality of information transmitting devices are connected via one transmission line, wherein the plurality of information transmitting devices transmit information on the transmission line. Has a collision detecting means for detecting the presence or absence of a collision with the information on the transmission line when the collision is started, and when the collision occurs, the transmission of the information is stopped, and when the collision does not occur, the transmission of the information is stopped. At least one information transmitting device includes a congestion degree detecting unit that detects a parameter indicating a congestion degree of the transmission path, and includes the congestion degree detecting unit. Information sending devices that do not
From the information sending device provided with the congestion degree detecting means,
The parameter indicating the congestion degree is obtained by communication via the transmission path, and when the congestion degree is determined to be equal to or more than a predetermined value based on the obtained parameter indicating the congestion degree, information per unit time to be transmitted on the transmission path. Control means for controlling the amount to be reduced.