JPH0343815B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention transmits data packets to which the address of the other station is attached by preceding a carrier signal with a duration corresponding to the priority of the data on a transmission path that commonly connects a plurality of terminal stations. Priority-added communication control that transmits signals from the plurality of terminal stations and communicates with each other, and also controls so that when simultaneous transmission of carrier signals occurs, data packets are transmitted with priority in the order of the duration of the carrier signals. Regarding the system, in particular, it is possible to reduce the delay in communication of higher priority by suppressing the interruption of other stations of lower priority prior to the retransmission of the carrier signal that was once stopped when simultaneous transmission occurs. be.

In general, a local communication line network that interconnects multiple terminal stations consisting of a large number of computers, terminal devices, etc. distributed within the same premises to utilize communication resources and improve communication performance. typically uses coaxial cable as a common transmission line,
As a communication control method to avoid contention between data packets sent to each other using the coaxial cable in common, the so-called CSMA method, which is a type of random access packet switching, is a carrier detection multiple access method. The so-called Ethernet type network, which has a distributed control configuration by adding a detection means, has the advantage of having a relatively simple communication control system configuration and high data transmission efficiency. , has been widely used as a highly reliable and scalable local data communications network.

Such conventional Ethernet-type networks are
It is configured as schematically shown in FIG. 1, and both ends of a coaxial cable 100 serving as a transmission path are matched and terminated by characteristic impedances 101 and 102, respectively, and a large number of terminal stations 109 each consisting of an electronic computer or a terminal device are provided. ,110,
111, etc. are the interface circuits 10, respectively.
6, 107, 108 etc. and taps 103, 10
4, 105 etc. in sequence, the coaxial cable 10
Each interface circuit 106, 107, 108, etc. collects information data from its own station into a data packet having a length within a predetermined length, and sends it from the destination station's address, etc. After adding a header section, the data is sent to the coaxial cable 100 in a broadcasting format. On the other hand, each terminal station 109, 110, 111, etc. identifies and selectively receives only the data packet to which its own address has been added, and imports it into its own station.
Communication between any two stations is realized. In a circuit network with such a configuration, there is no active component involved in the transmission line itself, so there is little risk that the effects of a failure occurring locally in the network will spread to the entire network. Therefore, in order to obtain high reliability and to avoid conflicts caused by simultaneous transmission of data packets, random access using the above-mentioned CSMA method, which is conventionally used in wireless lines, is used as described below. It was being done.

() When a request to send a data packet is made at any terminal station, first, the usage status of the transmission path 100 is checked, and if the transmission path 100 is in an empty state, that is, the carrier of the data packet sent from another station is not detected on the transmission path 100. In this case, the local station immediately starts sending data packets, and
When a carrier of a data packet transmitted from another station is detected on the transmission path 100, that is, when the transmission path 100 is in use by another station, data packets from the own station are not transmitted until the transmission path 100 becomes empty. The transmission of data packets from the local station is started when the transmission path 100 becomes vacant.

() The state of the transmission path 100 is monitored even after the transmission of data packets from the own station has started, and data packet collisions, that is, transmission of data packets being sent from the own station when data packets are being sent from other stations at the same time, are monitored. Always check to see if it has been compromised.

() If a collision of data packets due to simultaneous transmission from other stations is detected through the above-mentioned constant monitoring, the transmission of data packets from the local station is immediately stopped, and a random setting is set to avoid another collision. After the delay time has elapsed, the steps () and () described above are repeated.

Therefore, in a conventional Ethernet type network, the above process () reduces the time during which data packets damaged by collision occupy the transmission path 100 unnecessarily. Despite the fact that a large number of data packets are randomly transmitted upon access, a considerably high value has been obtained for the maximum usage efficiency of the transmission line, that is, the maximum throughput in the conventional Ethernet type network. However, when the transmission path is heavily loaded, with frequent requests for data packet transmission from each terminal station, collisions due to the simultaneous transmission of data packets as described above occur frequently. That is, the time required from when a transmission request is made to when it is received by the other station increases, and furthermore, the transmission delay time is distributed over a wide range.

In order to eliminate the drawbacks of the conventional Ethernet type network mentioned above, the present inventors first proposed the following.
Data packets are prioritized according to the importance of the information data they contain, and data packets containing information data that require immediacy are prioritized and communicated with a short communication delay time with a high priority. We have proposed a priority-added communication control method that can complete the process. This conventionally proposed priority-adding communication control system basically forms the above-mentioned Ethernet type network, but the mode of communication control to avoid collisions of data packets is
The configuration differs from the above-mentioned Ethernet type network as follows.

(1) Even if a preamble consisting of a carrier signal of a predetermined duration corresponding to the priority of the information data contained in the data packet is added and transmitted immediately before a data packet, and a collision between such preambles is detected, The transmission of the preamble is not stopped until the transmission of the carrier signal over a predetermined duration is completed.

(2) When a collision with a preamble from another station is no longer detected while the own station is transmitting a preamble consisting of a carrier signal of a predetermined duration,
Following the transmission of the preamble, a data packet is transmitted. However, if the transmission of a preamble from another station is still detected even after the transmission of a carrier signal of a predetermined duration from the own station, the transmission of the preamble from the other station is As soon as continued transmission is detected, transmission of the data packet following the preamble from the own station is stopped, and, similar to the process () in the conventional Ethernet type network described above, a random setting is made to avoid another collision. After the delay time has elapsed, data packet transmission from the local station is resumed starting from a predetermined preamble.

According to the above-mentioned algorithm in the conventionally proposed priority-added communication control system, if a collision occurs due to simultaneous transmission of data packets with different priorities, even if preambles are simultaneously transmitted from multiple terminal stations. However, among these multiple preambles, the data packet with the highest priority preceded by a preamble consisting of a carrier signal with the longest duration is the first to successfully complete the communication. Communication delay time for data packet transmission has been significantly reduced and improved compared to conventional Ethernet networks. However, even in such conventionally proposed priority-adding communication control systems, when requests for sending data packets with similar priority order occur frequently, data packets with similar priority order, and therefore carrier signals with the same duration length, are Collisions occur frequently due to the nearly simultaneous start of transmission, and the number of data packets with the same priority that restart transmission after a random delay time increases. Collisions will occur frequently, and the communication delay time of these data packets with the same priority will increase significantly, and there will be no significant difference in priority with other data packets with lower priorities, and the meaning of priority addition control will be lost. It had the disadvantage of being called out. Moreover, the tendency of such priority loss suddenly becomes noticeable when the proportion of data packets with high priorities exceeds half of the total data packets. Therefore, in order to ensure the effectiveness of priority addition control, For this purpose, it is necessary to reduce at least the proportion of data packets that are given high priority. For example, when a large number of requests are made to send data packets that require immediacy, such as voice packets on a telephone line, etc. However, the conventionally proposed priority-added communication control system still has the disadvantage of causing a major failure in this type of data packet transmission line.

An object of the present invention is to almost completely eliminate the above-mentioned conventional drawbacks, and to ensure that the effect of prioritizing data packets is obtained regardless of the traffic conditions on the data packet transmission line. By improving the signal processing algorithm when data packets collide with each other, the communication time delay for data packets containing high-priority information data with strict demands for immediacy, such as voice packets, has been reduced compared to conventional methods. It is an object of the present invention to provide a priority-added communication control method that can significantly reduce the amount of time required.

In other words, the priority added communication control method of the present invention is as follows:
A data packet with the address of the other station is sent out from each of the plurality of terminal stations, preceded by a carrier signal of a duration corresponding to the priority of the data, on a transmission line that commonly connects the plurality of terminal stations, and the terminal stations transmit data packets to each other. In a priority-added communication control system, the data packets are controlled to be transmitted with priority in the order of the duration of the carrier signals when simultaneous transmission of the carrier signals occurs. With regard to the simultaneous transmission of the carrier signals of the same priority, the transmission of the carrier signal of the same priority level is detected by detecting the almost simultaneous end of the transmission of the carrier signal from another station at the time of the end of the transmission of the carrier signal of a predetermined duration from the own station. For simultaneous transmission of the carrier signals, the carrier signals of new durations are successively preceded by new priority orders respectively set based on integers randomly selected from a predetermined group of integers. The data packets from the own station and the other station are respectively transmitted again, and the data packets from the own station are detected by detecting the continuous transmission of the carrier signal from the other station at the end of the transmission of the carrier signal of the predetermined duration of the own station. For simultaneous transmission of the carrier signals of high priority, following the completion of the priority transmission of the data packet from the other station, the carrier signal of the predetermined duration of the own station is preceded and the own station transmits the carrier signal of the predetermined duration. The present invention is characterized in that the data packet is transmitted again.

The invention will be explained in detail below by way of example embodiments with reference to the drawings.

However, the problem with the conventionally proposed priority-adding communication control method is that when data packets with the same priority collide with each other, the delay time is randomly set in the same manner for both of the colliding data packets. Since retransmission is performed after the lapse of time, another collision occurs repeatedly, and during the delay time for both, interrupt transmission of other data packets with lower priority is started, the transmission path is occupied, and it is difficult to transmit again. This increases the probability of collision occurrence, significantly increases communication delay time, and loses the significance of giving priority. In order to eliminate such conventional problems, in the priority-added communication control system of the present invention, when a collision occurs between data packets of the same priority or a higher priority, a collision is randomly performed as in the conventional system. By reallocating the priorities at the time of retransmission, assigning a new priority, and immediately retransmitting, the delay that was previously set after a collision can be avoided without having to retransmit after experiencing the set delay time. Suppresses interruptions caused by new signal transmissions from other stations with lower or the same priority that have occurred during the time,
By preventing the increase in communication delay time that occurred in the past,
This makes it possible to significantly reduce communication time delays compared to conventional methods. Therefore, in the communication control system of the present invention, it is possible to handle data packets under traffic conditions such as voice packets, which have strict requirements for immediacy, and in which there are frequent requests to transmit data packets that are transmitted in the same priority order. Even in this case, the effect of priority assignment control can be reliably achieved, and the delay in communication time of data packets having a high priority can be significantly reduced.

The configuration itself of the data packet transmission line according to the communication control system of the present invention, which provides such remarkable effects compared to the conventional system, is similar to the configuration of the conventional Ethernet type network shown in FIG. The structure of the data packet as a communication unit sent from the stations 109, 110, 111, etc. is as follows.
As in the conventionally proposed priority-addition communication control system, an example thereof is shown in FIG.
That is, in the data packet with the illustrated configuration, immediately before the data section 204 containing information data, there is a synchronization section 201 that contains a synchronization pattern for controlling synchronization of digital data and represents the start of the data packet, and a synchronization section 201 that represents the start end of the data packet. An address section 202 containing an address for identification and a control section 203 containing control information such as the type of information data, packet length, and order of information processing are sequentially preceded, and the so-called In the conventional Ethernet type network, the FCS section 205 containing a CRC code, that is, a periodic redundant signal for error detection is immediately followed, and the significant information of each section is decoded by each interface circuit 106, 107, 108, etc. However, in the priority added communication control system proposed conventionally and in accordance with the present invention, a preamble 200 consisting of a carrier signal that continues for a predetermined significant time without modulation is provided immediately before the significant information of each part. is further ahead. This preamble 200 not only informs other stations that the transmission line 100 is in use by the presence of an unmodulated carrier signal, but also indicates the priority of each data packet by its significant duration length. 0 is the lowest
According to the priority order, which is generally i as 0, 1, 2, etc., the maximum signal propagation time determined by the total length of the transmission line 100 made of coaxial cable is τ, and each interface circuit 106, 10
When the signal delay amount based on the time required for signal processing in 7, 108, etc. is γ, the duration of the unmodulated carrier signal in the preamble 200 P _i
is set by the following equation (1).

P _i = (2τ + γ) _i (1) Equation (1) indicates that the preamble 200 consisting of a carrier signal with a duration corresponding to the priority level i is sent from another station located at one end of the transmission path. Immediately before the preamble reaches another terminal station located at the other end of the transmission path 100, the other terminal station determines that the transmission path 100 is in an empty state and sends out the same priority or immediately below or immediately above priority. The elapsed time until the preamble 200 consisting of a carrier signal with a duration corresponding to the priority level reaches the terminal station with the priority level i, that is, the longest protection time ( The duration length of the carrier signal corresponding to the priority level i is set using 2τ+γ) as the unit duration time. In addition, in the priority-added communication control system proposed in the prior art and in accordance with the present invention, which is based on an Ethernet type network, the communication control method based on the significant control information of data packets with the configuration shown in FIG. 2 is similar to the conventional Ethernet type network. Communication control functions are distributed and assigned to the interface circuits of each terminal station, and there is no central station that manages the entire network, so as mentioned at the beginning, failures that occur at each terminal station The influence of this is localized only to the terminal station concerned, resulting in high reliability of data transmission.

Therefore, the communication control algorithm according to the present invention for a data packet configured by preceding the preamble 200 as described above follows the following procedure (a).
Construct sequentially through (b).

(a) When a data packet transmission request occurs, first, the usage status of the transmission line 100 is checked, and if the transmission line 100 is in an empty state, data packet transmission using the configuration shown in FIG. 2 is immediately started; however, if the transmission line 100 is already When the transmission line 100 is occupied by a data packet having the configuration shown in the second figure sent from another station, the sending of the data packet of the own station according to the configuration shown in the second figure is suspended until the transmission line 100 becomes empty, and the transmission line 100 is The transmission starts when the file becomes vacant.

(b) Even after the own station starts transmitting data packets with the configuration shown in FIG.
The state of the preamble 200 is monitored to check whether there is a collision with the preamble 200 sent from another station.

(c) When detecting the occurrence of a collision with the preamble 200 sent from another station while sending the preamble 200 from the local station, the sending of the data packet with the lowest priority, for example, 0, is immediately stopped. , the above steps (a) to (c) are repeated after a randomly set delay time has elapsed.

(d) For data packets with priority i where i≧1, after the start of transmission of the preamble 200, the carrier signal duration (2τ
+γ) Preamble 20 sent from another station every time
0, and if no collision with the preamble 200 sent from another station is detected by the time when the predetermined duration of the preamble 200 from the own station has elapsed, the Subsequently, the synchronization unit 201 starts sending out each part of significant information data. On the other hand, even when the predetermined duration of the preamble 200 from the own station has elapsed, that is, the duration Pi set by equation (1), if the transmission of the preamble 200 from another station is detected, at that point , the transmission of data packets from the own station using the configuration shown in the second figure is temporarily stopped, but instead of waiting for the elapse of a randomly set delay time as in the conventional system, An integer randomly selected from the group is set as a new rank i′, and a new duration P _i ′=(2τ+
γ) Preamble 2 consisting of the carrier signal of i′
00 in advance, the transmission of the new data packet of the configuration shown in the second figure is immediately resumed, and the above-described steps (a) to (d) are repeated.

Therefore, various methods can be considered as specific methods for setting the new priority order in step (d) above, but there are various methods that do not deviate significantly from the original priority order.
Moreover, it is preferable to adopt the following setting methods (A) to (C), which do not increase the duration of the preamble, which is so-called overhead and has no value as an information signal to be transmitted.

(A) Regardless of the initial priority order i, for example, a group of N consecutive integers 1, 2, ..., N
Randomly select one integer i′ from among them, and set a new duration corresponding to the new priority i′.
A preamble 200 consisting of a carrier signal P _i '=(2τ+γ)i' is preceded to newly construct the data packet shown in the second figure.

(B) New priority according to initial priority i
By changing the range of the integer group for selecting i′, there are N integer groups i, i+ for the initial priority i.
₁ , . The data packet shown in FIG. 2 is newly constructed by preceding the preamble 200.

(C) N integer groups (i+1)N+1, (i-1)N+2, ..., iN for the initial priority level i
Randomly select one integer from among them, and create a new duration P _i ′= corresponding to the new priority i′.
A preamble 200 consisting of a carrier signal of (2τ+γ)i' is preceded to newly construct the data packet shown in the second diagram.

Therefore, in the above setting method (A), there is no significant difference between the new priorities at the time of retransmission based on the initial priority. The preamble 200, which is essentially a redundant signal component, although it is unreasonable that a data packet with a higher priority may take priority over a data packet with an initial higher priority.
The degree of redundancy or overhead caused by the new setting of is the least.

In addition, in the above setting method (C), the hierarchical relationship of the initial priority is maintained in the same way in the new priority, and data packets with an initial lower priority have priority over data packets with an initial higher priority. Although this method is designed to ensure that such occurrences never occur, and the effect of giving priority can be reliably obtained, the degree of overhead caused by the preamble becomes large.

Furthermore, the setting method (B) described above is located between the above-mentioned setting methods (A) and (C) in both the degree of overhead caused by the preamble and the effect of adding priority, and data packets with the same priority are mutually Even if a new data packet with a lower priority interrupts and starts transmitting after both parties temporarily stop transmitting signals when a collision occurs, the subsequent data packet will not have priority over the data packet that restarted transmitting after the collision. In this way, a new priority order for retransmission is set.

Therefore, in the embodiment of the communication control system of the present invention described above, when data packets with the same priority collide with each other, reassigning new priorities to each packet and restarting signal transmission is as follows: Data packets with the lowest priority, for example, rank 0, are excluded, and only data packets with a higher priority than, for example, rank 1 are excluded, and the lowest priority is 0.
When a collision occurs between data packets with a priority of 0, signal transmission is resumed after a randomly set delay time elapses, as in conventional Ethernet networks. For data packets of all priority levels, when a collision occurs between data packets of the same priority level, a new priority level can be assigned to each packet and signal transmission can be restarted immediately without the elapse of a randomly set delay time. can. On the other hand, in order to check the free status of the transmission line, the protection time (2τ + γ) determined by the length of the transmission line is used as described above.
Since it is necessary to wait for the elapse of time to detect the start or end of the signal from the other station, it is necessary to start sending out a preamble from the own station before the data packet and avoid collision with a preamble that starts being sent from the other station at almost the same time. When the transmission of a preamble of a predetermined duration from the own station is completed in the detected state, even if the above-mentioned protection time (2τ + γ) has elapsed, the preamble being transmitted from another station is still detected. In this case, among the preambles from other stations that collide with the preamble from the local station, at least one has a higher priority than the data packet that is about to be sent from the local station, It can be determined that a preamble with a long duration exists. Therefore, if the duration of preamble transmission from another station is taken into consideration, taking into account the protection time (2τ+γ), the embodiment of the priority-added communication control system of the present invention can be further improved. That is, for example, the communication control method of the present invention can be implemented more effectively by the following aspects () to ().

() When a collision occurs due to the almost simultaneous start of transmission of a preamble from the local station and a preamble from another station, the transmission from the other station occurs at approximately the same time as the transmission of the preamble from the local station ends after the predetermined duration elapses. Only when the end of preamble transmission is detected, that is, when it is determined that the colliding partner station has the same priority as the local station.
After the transmission of the preamble is immediately resumed by reassigning the new priority as described above, and after the transmission of the preamble from the own station is completed due to the elapse of the predetermined duration time, even if the protection time (2τ + γ) has elapsed, Note that when the preamble transmission from another station continues, that is, when the colliding partner station has a higher priority than the own station, the above-mentioned new priority reassignment is not performed, and the transmission line becomes vacant. It waits for this condition to occur and then sends out its own preamble in the original priority order.

() This is similar to the embodiment () described above, except that only when it is found that the colliding partner station has the same priority as the local station, a new priority is reallocated and transmission of the preamble is immediately resumed. However, after the end of transmission due to the elapse of the predetermined duration time of the preamble from the local station, the protection time (2τ
+γ), if preamble transmission from another station continues, that is, if the colliding partner station has a higher priority than the own station, the above-mentioned new priority reallocation is performed. Instead, it waits until the transmission line is free, and after a randomly set delay time elapses, it transmits its own preamble based on its original priority, just as in conventional Ethernet networks. Send to.

() The above-described embodiments (), up to the point where, only when it is determined that the colliding partner station has the same priority as the local station, a new priority is reallocated and transmission of the preamble is immediately resumed.
Same as (), but after the preamble from the local station has finished transmitting after the predetermined duration time has elapsed,
Even after the protection time (2τ+γ) has elapsed, if preamble transmission from another station continues,
In other words, when there is a terminal station with a higher priority than the own station in the colliding partner station, the above-mentioned protection time is applied after detecting the end of sending data packets from the terminal station with a higher priority. After waiting for (2τ + γ) and confirming that the transmission path is free, the above-mentioned It reallocates a new priority and sends its own preamble.

When the communication control method of the present invention is implemented according to each of the above-mentioned aspects () to (), when signal transmission is restarted by reallocating new priorities after a collision, the data packets with the lower priority are assigned the highest priority. Therefore, it is possible to prevent communication control from being performed in an unreasonable manner, such as giving priority to a data packet that has a higher priority. Even if the priority-added communication control method becomes less effective, the effect of the priority-added communication control method is significantly reduced, and the effect of the priority-added communication control method of shortening the communication delay time in data packet transmission according to the priority order can be significantly increased. .

Next, a specific embodiment of data packet transmission for priority addition control according to the method of the present invention will be described with reference to FIGS. 3 and 4. FIG. 3 shows the state of the transmission path when three terminal stations 301, 302, and 303 simultaneously start transmitting data packets with priorities 0, 1, and 2, respectively.
Since the data packet 309 of No. 1 has a priority of 0, the data packet 309 at the time 304 after the signal propagation time 313 has elapsed.
At the same time as a collision with a preamble sent from another station is detected, transmission of data packets from the current station is stopped, and transmission of data packets is resumed after a randomly set delay time (not shown) has elapsed. In addition, the data packet 310 of the terminal station 302
has priority 1, so even if a collision with a preamble sent from another station is detected, the transmission of the current station's preamble is not immediately stopped, and the duration corresponding to the priority 1 assigned to that preamble ( 2τ
+γ), the collision with the preamble 306 sent from another station, actually the terminal station 303, continues, so the preamble 310 is sent at time 305 when the preamble duration time (2τ+γ) described above has elapsed. After completing the process and changing the priority order of the own station from the original rank 1 to the new rank L, the station continues to check the status of the transmission line and waits until the transmission line becomes vacant. Furthermore, the data packet of the terminal station 303 has priority 2, which is the highest among the three terminal stations, so the preamble 306 is
Although a collision with a preamble from another station is detected immediately after the start of transmission of the preamble 306, if the transmission of the preamble 306 is continued, the collision with the preamble 310 from the other station, actually the terminal station 302, is resolved at time 314. Since this is detected, at time 308 when preamble duration 2 (2τ+γ) corresponding to priority 2 has elapsed, the data packet 312 starts from the synchronization part 201, which is the first significant data in the data packet according to the configuration shown in the second figure. Starts transmission and completes data packet transmission from the local station. In this way, the terminal station 303 which has the highest priority among the three terminal stations
When the transmission of the data packet 312 from the terminal station 302 is completed, at time 315 when the protection time (2τ + γ) has elapsed from the completion, after confirming that the transmission path is free, the terminal station 302 transmits the new data packet that has been reallocated. The transmission of the preamble 307 with priority L is resumed, but since no collision with the transmission signal from another station occurs even after the preamble duration (2τ + γ) corresponding to the initial priority 1 has elapsed, at that point The transmission of the preamble 307 is discontinued, and the transmission of the data packet 311 is subsequently started, and data packet transmission from the highest terminal station 303 and the next highest terminal station 302 is completed. In this way, if the priorities assigned to the respective data packets are different between terminal stations where a collision of transmission signals has occurred, the data packets are transmitted in order of priority according to the minimum communication delay time. It will be completed efficiently.

On the other hand, in FIG.
This figure shows the state of the transmission path when transmissions of 06 and 406 start at the same time, that is, the mode of data packet transmission control according to the method of the present invention. , when the same duration elapses, for example, the duration corresponding to priority 1 (2τ+γ), the respective transmissions are simultaneously terminated, and the new priorities L ₁ , L ₂ and
After reallocating L ₃ and finishing sending the original preambles 404, 405, and 406,
At times 407, 408, and 409, after the protection time (2τ+γ) has elapsed and the transmission path is confirmed to be free, transmission of new preambles is restarted. Therefore, the above-mentioned new priority order L ₁ ,
For example, if L ₂ and L ₃ have a relationship of L ₁ < L ₃ < L ₂ , then terminal station 4, which has the highest priority among the three terminal stations,
For terminal stations 401 and 403 excluding 02, duration times L ₁ (2τ + γ) and L ₃ corresponding to new priorities L ₁ and L ₃ , respectively, are used.
Although each new preamble transmission ends when (2τ+γ) has elapsed, since new preamble transmission from the terminal station 402 is continuously detected, the end of the data packet transmission from the upper terminal station 402 is determined. stand by. Therefore, the priorities L ₁ ' and L ₃ ' are reallocated once again, taking into consideration the existence of other stations with the same priority levels that are on standby as well as the own station. On the other hand, in the upper terminal station 402, after the transmission of the new preamble is resumed, the duration time L ₃ (2τ+γ) of the new preamble from the terminal station 403, which has a higher priority among the lower terminal stations, has elapsed, and When a protection time (2τ+γ) has elapsed after collision with the signal transmitted from the terminal station 403 is no longer detected, the transmission of a new preamble 410 from the local station is terminated, and data packets are subsequently transmitted. The data packet transmission from the terminal station 402 which has received the highest priority through reallocation will be completed first. After the transmission of the data packet 411 from the terminal station 402 is completed and the protection time (2τ+γ) has elapsed, the free status of the transmission path is confirmed, and the above-mentioned reallocation is performed from the terminal stations 401 and 403. The new preambles are retransmitted almost simultaneously with new priorities L ₁ ′ and L ₃ ′, but
Assuming that the new priorities L ₁ ′ and L ₃ ′ are in the relationship L ₁ ′<L ₃ ′, the duration time L ₁ ′ (2τ+γ) and protection time (2τ+γ) of the new preamble from the lower terminal station 401 are ) has elapsed, the higher-order terminal station 403 stops sending the new preamble 412, and subsequently starts sending out the data packet 413. data packet transmission will be completed. After the collision with the upper terminal station 403 due to reallocation, the remaining terminal station 401 changes its priority order again and waits for the completion of the data packet transmission from the upper terminal station 403. After the transmission of the data packet 413 is completed, the protection time is elapsed. When (2τ+γ) has elapsed, transmission of the preamble 414 is resumed under the new priority L ₁ ″, but since no collision with another station is detected even after the protection time (2τ+γ) has elapsed, At that point, the transmission of the preamble 414 is discontinued, and the transmission of the data packet 415 is then started, and the data packet transmission from the lowest terminal station 401 due to the reallocation is also completed.

As explained above, according to the priority-added communication control system of the present invention, even if multiple collisions occur due to simultaneous transmission of data packets from multiple terminal stations having the same priority, the duration length of each preamble can be set to zero. Since signal transmission is restarted immediately after a deliberate change, the transmission of data packets can be efficiently completed one after another in accordance with the new reallocated priority order, with much shorter communication delay time than before. I can do it. Furthermore, even if data packet transmission from another lowest priority terminal station is interrupted during the signal processing period after a collision among such multiple terminal stations with the same priority, the data packets reallocated after the collision will be transmitted. Since the priority of the terminal station is always set to a higher priority than the lowest priority, when restarting signal transmission after waiting for a randomly set delay time to elapse, as in conventional Ethernet networks, for example. As shown in the figure, there is no risk of an increase in the communication delay time of data packet transmission due to interruptions caused by new signal transmission from other terminal stations, and priority addition control is possible even for data packet transmission from multiple terminal stations with the same priority. The effects of this can be clearly mentioned.

In order to clearly demonstrate the above-mentioned remarkable effects of the priority-added communication control system of the present invention, in the above-mentioned embodiment (), the priorities assigned to each terminal station are limited to only two types, 0 and 1. FIG. 5 shows a characteristic curve showing how the average communication delay time 503 of data packet transmission changes with respect to the throughput, that is, the usage efficiency 504, which was determined by the simulation conducted. Note that the simulation model described above assumes that the number of terminal stations with priority levels 0 and 1 is 100 each, and that each terminal station transmits a data packet of a fixed time length by so-called Poisson arrival. Also, when restarting signal transmission after waiting for a randomly set delay time to elapse, the average interval of the delay time is set to 0.25.
The average communication delay time 503 taken on the vertical axis is the result of simulating a data packet transmission period with a packet length of 5000, where N is the packet length and the number of new priorities to be reallocated is N = 10. It is shown normalized by the packet length.

In the group of communication delay time characteristic curves shown in FIG. 5, a curve 500 shows the communication delay time characteristic in the case of a conventional Ethernet type network in which no priority is given to each data packet, and a curve 501 shows the communication delay time characteristic in the case of a conventional Ethernet type network that does not give any priority to each data packet. The curve 5 shows the communication delay time characteristics for data packet transmission with priority 0 when priority addition control is performed according to the method.
02 shows the communication delay time characteristic for data packet transmission with priority 1 in the same case, and curve 505 shows the communication delay time characteristic for data packet transmission with priority 1 when priority addition control is performed using the conventional proposed method. It shows the characteristics. As is clear from comparing these characteristic curves, priority is given to data packet transmission from multiple terminal stations sharing the transmission path, and new priority is given when retransmitting after a collision. As a result, even in cases where data packets assigned priority 1 account for half of the traffic and priority addition control using the conventional proposed method would not be sufficiently effective, priority addition control using the method of the present invention can be applied. If the control is carried out, the communication delay time of data packet transmission assigned priority 1 can be suppressed to a sufficiently short value range even in the vicinity of the throughput saturation region 1, and moreover, the reaction of improving the transmission efficiency of such upper packets can be suppressed. It was confirmed that the deterioration in communication delay time characteristics for data packet transmissions assigned a lower priority of 0 could be kept to a slight degree.

Next, when applying the priority addition control method of the present invention to the data packet transmission circuit network having the configuration shown in FIG.
FIG. 6 shows an example of the configuration of the priority addition control circuit to be installed in the devices 107, 108, etc. In the illustrated circuit configuration, the control signal b introduced from the input terminal is
In order to indicate that the transmission line 100 is occupied by a data packet sent from a terminal station other than the own station, the carrier signal appearing on the transmission line 100 is captured via a hybrid circuit, and the carrier signal sent from the own station is captured. consists of a carrier signal detection output signal that is generated by canceling and canceling the carrier signal sent from the other station by the hybrid circuit so that only the carrier signal sent from the other station can be detected. It is used to detect the occurrence of a collision with the preamble sent from the station. When a data packet transmission request is made from the own station, the signal r applied from the input terminal to the set input terminal S of the flip-flop 600 becomes logic level 1, and the flip-flop 600
0 is set and a logic level 1 Q output is provided to one input terminal of AND gate 601. Therefore, when control signal b becomes logic level 1,
That is, when the transmission path 100 is occupied by a data packet from another station or a preamble from another station is being sent, the control signal b at logic level 1 is sequentially passed through the inverter 609 and the OR gate 610. Since the logic level 0 is applied to the other input terminal of the AND gate 601, the output of the AND gate 601 becomes a logic level 0, and the clock generation circuit 603 controlled by the AND output does not operate. The transmission of the continuous clock pulse train signal ck1 from the clock generation circuit 603 is suspended. On the contrary,
When the transmission line 100 becomes empty and the control signal b becomes a logic level 0, the output of the AND gate 601 becomes a logic level 1, and the clock generation circuit 603
is activated to send out a continuous clock pulse train signal ck1, and an external circuit (not shown) converts the continuous clock pulse train signal ck1 into a preamble 200.
is formed and sent to the transmission path 100. At the same time, the logic level 1 of the output of the ungate 601
The rise detection circuit 604 detects the rising edge, and the logic level 1 signal of the detection output is applied to the set input terminal S of the flip-flop 602, so the flip-flop 602 is set and its Q output becomes the logic level 1. Since the transmission path 100 becomes empty and the control signal b becomes logic level 0, the transmission of the preamble 200 is started as described above, and then the preamble 200 is transmitted almost simultaneously from the other station. Even when the preamble arrived and the control signal b becomes logic level 1 again, the clock generation circuit 603 continues to operate, and therefore the preamble 200 continues to be sent out. In addition, the clock generation circuit 60
The continuous clock pulse train signal ck1 from 3 is supplied to one input terminal of ungate 608, while the output of flip-flop 602, which is supplied to the other input terminal, is at logic level 0 in the above-mentioned set state. Therefore, the ungate 608 is closed, and the sending of the data packet sending clock signal ck2 from the ungate 608 is suspended. Furthermore, a continuous clock pulse train signal ck1 from the clock generation circuit 603
is also supplied to the counter 605 and counted, and the logic level 1 is formed every preamble duration time (2τ+γ) set equal to the signal transmission protection time of the transmission path 100, or when a preamble duration time of a predetermined length has elapsed. The counting force Q ₁ is supplied to one input terminal of AND gate 606 . Since the control signal b is supplied to the other input terminal of the AND gate 606 via the inverter 609, when the transmission line 100 is in an empty state where the control signal b becomes logic level 0, the AND gate 606
At the same time as the count output _Q1 of the counter 605 is applied, the output of the flip-flop 602 becomes logic level 1, and the flip-flop 602 whose AND output is applied to the reset input terminal R is reset, so its output becomes logic level 1, and the AND gate 608 is opened, and a clock signal ck2 for transmitting data packets is sent out, which is modulated by an information signal in an external circuit (not shown) to form data packets 201 to 205 with the configuration shown in the second diagram, and the transmission line 100
At the same time, the transmission of the preamble 200 formed from the continuous clock pulse train signal ck1 is stopped. On the other hand, the other count output Q ₂ of the counter 605 becomes logic level 1 when the preamble duration time of a predetermined length has elapsed, and the AND gate 6
07, and when the preamble 200 of the local station finishes sending out after a predetermined duration time, the preamble is sent to the other input terminal because the preamble sending from another higher-ranking station continues. If the control signal b has reached the logic level 1, it means that the collision with the upper terminal station is continuing, so the output of the AND gate 607 becomes the logic level 1, and the AND output is reset. Since the flip-flop 600 applied to the terminal is reset and its Q output becomes logic level 0,
The output of the AND gate 601 that supplies the Q output also becomes logic level 0, and the clock generation circuit 6
03 stops and enters a standby state waiting for the transmission line 100 to become vacant.

By the above-described operation of the priority addition control circuit having the configuration shown in FIG. The increase in the hardware amount of the terminal equipment due to the installation of the system is slight, and the economic efficiency of the conventional data packet transmission system is not impaired by applying the system of the present invention.

As is clear from the above description, according to the present invention, priority is given to data packet transmission from multiple terminal stations that commonly use a transmission path made of a coaxial cable according to the importance of information data, and data packets are mutually transmitted. When trying to reduce transmission delay time due to contention between packets and voice packets on telephone lines, where there is a strict requirement for immediacy, and where there is a large number of data packets with the same priority being transmitted, The effect of priority addition control can be reliably obtained, and the delay time due to competition in data packet transmission according to the priority order can be significantly reduced compared to the conventional method. Therefore, the priority-added communication control method of the present invention can not only achieve the above-mentioned remarkable effects when applied to the communication between computers or terminal devices in the same premises as mentioned at the beginning, but also It also has the advantage of being able to handle the transmission and exchange of various types of information, such as local telephone exchanges and image communications, in a single network, making it suitable for application to local networks such as office automation. This method is recognized as extremely promising as a communication control method.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a data packet transmission circuit network, FIG. 2 is a diagram showing an example of the configuration of a data packet 413 to which priority-added communication control is applied, and FIG. 3 is a diagram showing priority-added communication according to the method of the present invention. FIG. 4 is a time chart showing an example of the control mode; FIG. 4 is a time chart showing another example of the control mode; FIG. FIG. 6 is a block diagram showing a configuration example of a priority addition control circuit according to the present invention. 100... Transmission line, 101, 102... Characteristic impedance, 103, 104, 105... Tap, 106, 107, 108... Interface circuit, 109, 110, 111... Terminal device,
200...Preamble, 201...Synchronization section, 2
02...Address section, 203...Control section, 204
...Data Department, 205...FCS Department, 301,30
2,303...terminal station, 304,305,308,
314,315...time, 306,307,31
0...Preamble, 309, 311, 312...
...Data packet, 313...Signal propagation time, 4
01,402,403... terminal station, 404,40
5,406,410,412,414...Preamble, 407,408,409...Time, 41
1,413,415...Data packet, 50
0,501,502,505...Characteristic curve, 50
3...Average communication delay time, 504...Throughput, 600, 602...Flip-flop, 60
1,606,607,608...and gate,
603...Clock generation circuit, 604...Rise detection circuit, 605...Counter, 609...Inverter, 610...OR gate.

Claims (1)

[Scope of Claims] 1. A data packet with the address of the other station is transmitted to the plurality of terminal stations by preceding it with a carrier signal having a duration corresponding to the priority of the data on a transmission path that commonly connects the plurality of terminal stations. The same method in a priority-added communication control system, in which the data packets are sent out from each other to communicate with each other, and when simultaneous sending of the carrier signals occurs, the data packets are sent out with priority in the order of the duration of the carrier signals. Alternatively, regarding simultaneous transmission of the carrier signals with a higher priority than the local station, detection of substantially simultaneous completion of transmission of the carrier signal from the base station at the end of transmission of the carrier signal of a predetermined duration from the local station. Regarding simultaneous transmission of the carrier signals of the same priority detected by
The data packets of the local station and the other station are respectively sent out again with each carrier signal having a new duration being preceded in accordance with a new priority set based on an integer randomly selected from a predetermined group of integers. However, when the transmission of the carrier signal of a predetermined duration of the own station ends, the simultaneous transmission of the carrier signals with a higher priority than the own station is detected by detecting the continuous transmission of the carrier signal from another station. The priority transmission system is characterized in that, following the termination of the priority transmission of the data packet from the other station, the data packet of the own station is sent out again with the carrier signal of a predetermined duration of the own station preceded. Rights-added communication control method. 2. In the communication control system according to claim 1, the new priority ranges, which are respectively set based on integers randomly selected from the predetermined group of integers, are sequentially set according to the initial priority order. A priority-added communication control method characterized in that the priority is changed to . 3. In the communication control system according to claim 1 or 2, following the completion of preferential transmission of the data packet from the other station having a higher priority than the own station, the transmission of the data packet of the predetermined duration is 1. A priority-added communication control system characterized in that the data packet of the local station is sent out again with a carrier signal in advance. 4. In the communication control system according to claim 1 or 2, following the completion of the priority transmission of data packets from the other station that has a higher priority than the own station, the other station has the same priority as the own station. In preparation for the simultaneous retransmission of the carrier signals from other stations, the data packet of the local station is retransmitted with the carrier signal of the new duration corresponding to the new priority being preceded. Features a priority-added communication control method.