JP3087688B2 - Line control method and reference station to which it is applied - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line control system suitable for use in, for example, slotted Aloha communication, and to a reference station and a slave station to which the line control system is applied.

[0002]

2. Description of the Related Art Conventionally, when a plurality of slave stations transmit a message to a reference station by sharing a communication line, a slotted Aloha line control system is used. This means that the slot timing is transmitted on the downlink from the reference station to all slave stations,
In this method, a slave station having a message burst-transmits a message to a reference station on the uplink in accordance with the slot timing.

In this method, when a message is generated in a plurality of slave stations at the same time, the slave stations attempt burst transmission at the same time according to the slot timing from the reference station. Collision prevents the reference station from receiving the message correctly. As a result, these slave stations are forced to retransmit the message after a certain period (each slave station determines each time with a pseudo random number or the like). Also, if there are many slave stations transmitting simultaneously, the uplink is congested, and it is difficult for messages from the slave stations to reach the reference station.

[0004] In order to improve this point, the following methods have conventionally been proposed. (1) Slave reservation is made from a slave station to a reference station to exclusively use slots, thereby suppressing transmission signal collisions and improving transmission efficiency.
No. 81645).

(2) A signal collision is detected at the reference station, and retransmission is instructed only to the corresponding child station, thereby suppressing transmission signal collision at the time of retransmission and improving transmission efficiency. -244794).

[0006]

However, the prior art has the following problems. That is, the first problem is that the above-mentioned conventional method (1) based on slot reservation is not effective under the situation where the uplink is congested. The reason is that even in a situation where the uplink is congested, even a slot reservation request message is difficult to reach the reference station, and slot reservation is difficult. Second
The problem with (2) is that the conventional method of detecting a signal collision in the reference station of (2) requires an expensive reference station.
The reason is that it is necessary to provide a signal collision detection circuit for detecting a signal collision and specifying a colliding slot in the reference station.

[0007] The third problem is that even if a child station has an urgent message, it is difficult to transmit it with priority. The reason is that it does not have a priority control function related to uplink access. The present invention has been made in view of such a problem, and an object of the present invention is to improve transmission efficiency by reducing line congestion, and to provide a line control system capable of transmitting urgent messages with priority. Is to provide.

[0008]

According to a first aspect of the present invention, there is provided a line control system for controlling communication in a common uplink and downlink connecting a reference station and a plurality of slave stations, wherein the reference station is Transmitting a signal indicating slot timing and an uplink priority level indicating the degree of congestion of the uplink to the plurality of slave stations via the downlink , each of the slave stations having the uplink priority level And the message priority level assigned to the message to be transmitted, and only when the message priority level is equal to or higher than the uplink priority level, according to the slot timing, transmits the message to the reference station via the uplink. while, if the message priority level is lower than the uplink priority level, the value of the message priority level If the message priority level is lower than the uplink priority level and the message is not transmitted, the value of the number of message retransmissions is increased, and a signal indicating the number of message retransmissions when transmitting the message. Also sent at the same time ,
The reference station may increase or decrease the uplink priority level based on the number of retransmissions of the message transmitted from the slave station. In addition, the reference station may increase the value of the uplink priority level based on the number of message retransmissions, and then decrease the value of the uplink priority level after a predetermined time has elapsed. A reference station to which the line control method according to claim 3 is applied is a reference station connected to a plurality of slave stations via a common uplink and downlink, and indicates a slot timing and a degree of congestion of the uplink. Transmitting means for transmitting a signal indicating a line priority level to the plurality of slave stations via the downlink , indicating a message transmitted from the slave station and a message retransmission count indicating the number of times the message has been retransmitted. It is characterized by comprising receiving means for receiving a signal, and control means for increasing or decreasing the uplink priority level based on the number of message retransmissions.

[0009]

[0010]

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing a line network to which a line control system according to an embodiment of the present invention is applied. In this figure, the reference station 1 has slave stations 4, 5, 6
The reference station 1 broadcasts to the slave stations 4, 5, and 6 via the downlink 2,
On the other hand, slave stations 4, 5, and 6 are configured to transmit to reference station 1 via uplink 3 only when transmission is necessary.
The downlink 2 and the uplink 3 may be any one of a wired communication line, a wireless communication line, a satellite communication line, and an optical transmission communication line.
Alternatively, it is a communication line configured by mixing these.

FIG. 2 is a time chart showing downlink and uplink signal frames for explaining the channel control system of one embodiment.

As shown in FIG. 2, the reference station 1 broadcasts "slot timing", "uplink priority level", and "downlink information" to the slave stations 4, 5, and 6 in a downlink 2 signal frame. I do. On the other hand, each time a message to be transmitted to the reference station 1 occurs, each of the slave stations 4, 5, and 6 sets a “message priority level” for the message according to the type (degree of urgency, etc.) It waits for a notification of “slot timing” and “uplink priority level” from the reference station 1. When the slave stations 4, 5, and 6 receive the notification, the values of the "uplink priority level" from the reference station and the "message priority level"
Are compared, and only when the value of the “message priority level” is equal to or higher than the “uplink priority level”, the “message” and its “number of message retransmissions” are compared with the “slot timing” in the uplink 3 signal frame. To the reference station 1.

Thereafter, when the slave stations 4, 5, and 6 wait for a response from the reference station 1, there is no response from the reference station 1, or when the transmission to the reference station 1 is suspended because the "message priority level" is low, The value of “the number of message retransmissions” is increased by 1 and the value of the “message priority level” is increased in accordance with the “number of message retransmissions” so that the next “slot timing” and “uplink priority level” from the reference station 1
Wait for the notification, and when those notifications are received, retransmission is attempted in a similar manner.

When an emergency message is generated, the slave stations 4, 5, and 6 set the message priority level to a high priority level according to the type of emergency, and can transmit the message to the reference station 1 preferentially. The slave stations 4, 5, and 6 receive and decode the "downlink information" from the reference station 1, and extract a message from the reference station 1 addressed to the own station.

Further, the reference station 1 receives and decodes the signal frames of the uplink 3 from the slave stations 4, 5, and 6 and decodes them.
From the message and the number of message retransmissions. Then, the “uplink priority level” is controlled to increase or decrease in accordance with the “number of message retransmissions”, and is reflected in broadcast transmission to the slave stations 4, 5, and 6 in the future.

FIGS. 3 and 4 are flow charts for explaining the operation of the line control system according to the embodiment.
5 is a flowchart for explaining the operation of the reference station 1. First, in step S1, the uplink priority level is set to an initial value L0 and the time counted by the timed timer is set to an initial value T0, and the time counting of the timed timer is started. Next, in step S2, it is determined whether or not a signal frame has been received from the slave stations 4, 5, and 6. If it has been received, the process proceeds to step S3, and if not, the process proceeds to step S5.

In step S3, the slave station 4, which has received the signal,
The signal frames from 5 and 6 are received and decoded, and the uplink priority level Ln corresponding to the number of message retransmissions (tentatively N) is the current uplink priority level (tentatively L).
It is determined whether it is greater than. As a result, if Ln is larger than L, the process proceeds to step S4, and if Ln is less than L, the process proceeds to step S5. In step S4, the current uplink priority level is set and updated to Ln according to the message retransmission count N. Thereafter, the processing proceeds to step S8.

On the other hand, in step S5, it is determined whether or not the time-out timer has timed out (that is, the time measurement has been completed).
If no time-out has occurred, the process returns to step S2 to wait for reception of a signal frame from each of the slave stations 4, 5, and 6. In step S6, it is determined whether or not the uplink priority level L is greater than the initial value L0. If the uplink priority level L is greater than the initial value L0, the process proceeds to step S7 and the current uplink priority level L is set to one. Step S after subtracting
Then, if the uplink priority level L is equal to the initial value L0, the process directly proceeds to step S8.

In step S8, the uplink priority level L
, The time of the timed timer is set to T, and the time is restarted. Thereafter, the process returns to step S2 and waits for reception of a signal frame from slave stations 4, 5, and 6.

Next, FIG. 4 is a flowchart for explaining the operation of the slave stations 4, 5, and 6. First, step S
In step 11, the system waits for the occurrence of a message. When a message occurs, the process proceeds to step S12, and the message priority level is initialized to M0 according to the type of the message. This initial value M0 does not need to be the same value for all messages, and can be changed as appropriate, for example, according to the urgency of the message. Next, in step S13, the number of message retransmissions is initialized to zero.

In step S14, reception of a signal frame from the reference station 1 is waited, and if a signal frame is received, the process proceeds to step S15. In step S15, it is determined whether or not the value of the message priority level is equal to or more than the value of the uplink priority level obtained by receiving and decoding the signal frame.
Then, if it is smaller than the value of the uplink priority level, the process proceeds to step S18.

In step S16, a message and the number of message retransmissions of this message are transmitted to the reference station with reference to the slot timing from the reference station 1. In step S17, it is determined whether or not there is a response indicating that a message or the like has been received from the slave station within a predetermined time as a result of decoding the reception of the signal frame from the reference station. as a result,
If there is a response, the process returns to step S11 and waits for generation of a message again. On the other hand, if there is no response within the fixed time, the process proceeds to step S18.

In step S18, the value of the number of message retransmissions is increased by one. In step S19, it is determined whether or not the number of message retransmissions is equal to or greater than a predetermined number. If the number is equal to or greater than the predetermined number, the message is abandoned and the processing of the flowchart in FIG. 4 is started again. On the other hand, if the number has not reached the predetermined number, the process proceeds to step S20, and the message priority level is set to Mn according to the number N of message retransmissions. Then, in step S21, according to the number N of message retransmissions, the process waits for a certain time (time determined each time by a pseudo random number or the like), and proceeds to step S14.

In the above description of the operation, the uplink priority levels are L0 <L1 <L2 <... And the message priority levels are M0 <M1 <M2 <. Therefore, in the line control method of the present embodiment, the reference station 1 detects the degree of line congestion from the “number of message retransmissions” received from the slave stations 4, 5, and 6, thereby controlling the “uplink priority level” to increase or decrease. Then, since the broadcast is notified to all the slave stations 4, 5, and 6, the congestion of the uplink can be detected without requiring the signal collision detection circuit in the reference station 1 as in the related art. On the other hand, the slave stations 4, 5, and 6 transmit only when they have a message with a higher priority than the notified "uplink priority level", so that uplink congestion can be reduced and transmission efficiency can be improved.

The slave stations 4, 5, and 6 transmit the reference station 1 after transmission.
If no response is received or the message priority level is low, and the transmission is postponed, increase the number of message retransmissions and increase the message priority level accordingly. Therefore, the degree of congestion of the uplink can be reflected on the reference station, and the staying message can be transmitted preferentially, and furthermore, the urgent message can be transmitted preferentially by providing a high “message priority level”.

Note that, in the present embodiment, the present invention is not limited to this, and can be applied to ones suitable for applying the present invention.

Since the present invention is configured as described above, the following effects can be obtained. That is, since the reference station controls the uplink priority level according to the congestion of the uplink, each slave station performs transmission control according to the priority level of the message when transmitting, so that signal collision on the uplink can be reduced. Thus, congestion on the uplink can be reduced and transmission efficiency can be improved. In addition, the slave station sets the message priority level according to the type of the message, and sets the high priority to the urgent message, so that the slave station can transmit the urgent message with priority.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit network to which a circuit control method according to an embodiment of the present invention is applied.

FIG. 2 is a time chart showing signal frames on a downlink and an uplink for explaining a circuit control method according to an embodiment.

FIG. 3 is a flowchart for explaining an operation of a reference station in the circuit control method according to one embodiment.

FIG. 4 is a flowchart for explaining the operation of a slave station in the circuit control method according to one embodiment.

[Explanation of symbols]

 1 Reference station 2 Downlink 3 Uplink 4,5,6 Slave station

Claims (3)

(57) [Claims] 1. A line control system for controlling communication in a common uplink and downlink connecting a reference station and a plurality of slave stations, wherein the reference station indicates a slot timing and a degree of congestion of the uplink. a signal representing the priority level, before
Transmitting to the plurality of slave stations via the downlink , each of the slave stations compares the uplink priority level with a message priority level assigned to a message to be transmitted, and the message priority level is Only according to the slot timing when the uplink priority level or higher, while transmitting the message to the reference station via the uplink ,
If the message priority level is lower than the uplink priority level, increase the value of the message priority level.If the message priority level is lower than the uplink priority level and the message is not transmitted, the message The value of the number of retransmissions is increased, and when transmitting the message, a signal indicating the number of message retransmissions is also transmitted at the same time , and the reference station performs the uplink based on the number of message retransmissions transmitted from the slave station. A line control method characterized by increasing and decreasing the line priority level. Wherein said reference station according to claim wherein after increasing the value of the uplink priority level, characterized in that to reduce the value of the uplink priority level after a predetermined time has elapsed based on the message number of retransmissions 1. The line control method according to 1 . 3. A reference station connected to a plurality of slave stations via a common uplink and downlink, and transmits a signal indicating slot timing and an uplink priority level indicating the degree of congestion of the uplink to the downlink. Transmitting means for transmitting to the plurality of slave stations via a line ; receiving means for receiving a message transmitted from the slave station and a signal indicating the number of message retransmissions indicating the number of times the message has been retransmitted; and the message retransmission. Control means for increasing or decreasing the uplink priority level based on the number of times.