JPH01215143A - Communication system - Google Patents

Abstract

PURPOSE:To cope with the state from high to low traffic by varying the range of search in response to the state of traffic. CONSTITUTION:A traffic monitor section 18 receives all reception signal received by an antenna section 20 via a reception section 12, checks the traffic state on a channel based on the reception signal to generate a control parameter. The parameter is a value being a division of the number of collision slots during an object period by the number of operating slots during the object period, for example. Based on the parameter, the search section 15 adjusts the number of slots in a storage section 153. Thus, the state of traffic from low to high traffic is coped with flexibly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a communication system in which a plurality of stations use a time division multiplexing method to share one communication line.

, [Prior Art] In the conventional time division multiple access (TDMA) system, all stations sharing a communication line (channel) are allotted their own time slots (time 5lots), and each station uses the corresponding time slot. There are fixed allocation TDMA systems in which data is sent in slots, and random access TDMA systems in which a transmitting station independently determines the time slot in which it should transmit data.

[Problem to be solved by the invention]

In the conventional fixed assignment TDMA system described above, each station is assigned its own time slot, so each station can reliably transmit data at regular intervals. However, since it is necessary to wait until the allocated time slot arrives, high throughput can be obtained during high traffic, but the number of empty time slots increases during low traffic, resulting in poor transmission efficiency. on the other hand,
In the random access TDMA system, each station selects its own transmission timing and sends out data, so unlike the fixed allocation TDMA system, there is no waiting time, but on the other hand, data from other stations may collide with data on the channel. , there is a risk that the data will not reach the destination station and the channel will be wasted, so it is advantageous when traffic is low, but
At times of high traffic, throughput decreases due to the effects of collisions.

[Means to solve the problem]

The method of the present invention is a communication method in which communication is performed between a plurality of communication stations individually assigned a plurality of time slots on one communication line, in which each of the plurality of communication stations has a range to be searched. a search range value storage means for storing a search range value indicated by the search range value; a first time slot on the communication line at the current time; and a second time slot that arrives after the first time slot by the number of times the search range corresponds to the first time slot. determining means for determining whether or not the time slot assigned to the own station arrives during the period in which the time slot assigned to the own station arrives in response to the occurrence of data within the own station; When the time slot is detected, the data is sent onto the communication line in this time slot, and when the arrival of the time slot assigned to the local station is not detected, the data is transmitted without waiting for the arrival of the time slot assigned to the local station. data transmitting means for transmitting the data onto the communication line;
and updating means for monitoring the traffic state of the communication line and updating the search range value stored in the storage means based on the traffic state.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings. FIG. 2 shows a configuration example of a satellite communication network among various communication networks to which the present invention can be applied. In this network, a plurality of ground stations 1 communicate via one satellite station 2, and referring to each FIG. a TDMA control section 10 having a random transmission section 13, a fixed allocation waiting section 14, a table search section 15, a transmission buffer section 16, a retransmission control section 17, a traffic monitoring section 18, and a reception buffer section. 19 and antenna part 2
It consists of 0.

When data occurs within the station, this data is stored in the transmission buffer section 16 and the length of this data is detected.

At this time, if the data length exceeds the length that can be accommodated in one time slot, this data is transferred to the retransmission control unit 1.
On the other hand, if the number does not exceed the limit, it is sent to the table search unit 15, where it is determined whether random transmission or fixed allocation transmission should be performed.

FIG. 3 shows an allocation table 15 included in the search section 15.
1. A pointer storage section 152 that stores the current time slot number and a search width storage section 153 that stores the number of slots to be searched are shown. Here, one frame is divided into 13 time slots from the 1st to the 13th, and the 1st to 13th time slots are allocated to 13 stations A to M, respectively. Assume that the frames are continuous. Table 151 defines the allocation relationship between such time slot numbers and each station. When the table search unit 15 receives the transmission data, it learns the current time slot number from the storage unit 152 and the number of slots to be searched from the storage unit 153, and if the slot number of its own station is within the search range. Check whether it exists or not. For example, if the contents of storage units 152 and 153 are 6 and 4, respectively, the search range will be slot numbers 6 to 10.

If there is a slot number assigned to the local station within this search range, it is determined that the transmission data should be fixedly assigned and sent, and if there is not, it is determined that the transmission data should be randomly sent. The number of slots to be searched stored in the storage section 153 is updated based on the control parameters from the monitoring section 18.

That is, the traffic monitoring section 18 receives all received signals received by the antenna section 20 via the receiving section 12, examines the traffic state on the channel based on these received signals, and generates control parameters. For example, this parameter can be used to calculate the number of collision slots (slots in which data of one station collides with data of another station on the channel) during the period of interest, and the number of slots used (slots in which one station collides with data of another station on the channel) during the period of interest. It is the value divided by the number of slots used without colliding with the data of Based on this parameter, the search unit 15 adjusts the number of slots in the storage unit 153. This adjustment is done, for example, with the aim of ensuring that the parameter value does not exceed 1. In other words, when the parameter value exceeds 1, the number of slots in the storage unit 153 is increased to reduce collisions. Adjust accordingly.

Furthermore, if the number of channels to be searched is varied in different ways for each round, it is possible to prioritize access to channels for each station. If the number of slots to be searched is set to 0, random transmission will always be performed, and if the number of slots to be searched is selected to be equal to the total number of slots included in one frame length, fixed allocation transmission will always be performed.

Next, an example of access according to the method of the present invention will be explained with reference to FIG. On the satellite channel, there are 1
A plurality of frames each consisting of three time slots are consecutive. It is assumed that each station has a table with the same contents as table 151 in FIG. FIG. 4 shows an example of access at ground station F when the propagation delay from the ground station to the satellite station is about two time slots. Assume that data occurs at time t1 in station F, where the number of slots to be searched stored in the storage unit 153 of the search unit 15 is 4. At this time, the content of the storage unit 152 of station F is 7, indicating that the time slot g at the current time, that is, time t1, is the seventh time slot. Therefore, the search range of the table 151 is slot numbers ■ to ■. Table 1 shows that the slots with slot numbers 7 to 11 are assigned to stations G to K, and do not include the slot number ■ assigned to own station F.
51, the search section 15 sends the data to the random sending section 13, which sends this data out from the antenna section 20 onto the channel in the next time slot h.

Next, assume that data occurs at time t2. At this time,
The content of the storage unit 152 of station F is 3, indicating that time slot C at the current time, ie, time t, is the third time slot. Therefore, table 1
The search range of 51 is slot numbers ■ to ■. Own station F
Since the slot number ■ assigned to
4, and the allocation waiting unit 14 waits until the sixth time slot f and sends the data to this time slot f.

Next, the case where data collision occurs on the channel will be explained with reference to FIG. At station F, time ts(
When data occurs in time slot) C), the table 151 in station F is checked, and it is found that the slot f assigned to own station F is included within the search range, and the data is transmitted on the channel by waiting until time slot) f. Send to.

On the other hand, at station B, time 14 (time slot e)
When data is generated, the table 151 in station B is checked, and it is found that time slot b with slot number ■ assigned to station B is not included in the search range. next time slot) f
and send it out on the channel.

As a result, the data of station B and station F is transferred to time slot) f
This collision is detected by the satellite station, and the satellite station notifies stations B and F of this fact. Upon receiving this notification, the monitoring units 18 of stations B and F instruct the retransmission control unit 17 to send the same data as the above-described collision data stored in the retransmission control unit 17 to the allocation waiting unit 14. As described above, the data sent to the allocation waiting section 14 is sent out on the channel after waiting until the time slot of the own station. In this way,
At the very least, make sure that collisions between the same stations do not occur again. Thereafter, these stations transmit data on the channel using fixed allocation transmission until all the data in the transmission buffer unit 16 is exhausted.

〔Effect of the invention〕

As described above, the present invention is capable of flexibly responding to low traffic conditions to high traffic conditions by varying the search range according to the traffic condition, and is capable of handling fixed allocation T.
This has the effect of realizing communication that takes advantage of the advantages of the DMA system and the random access TDMA system.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing an example of the configuration of a network to which the present invention can be applied, and FIG.
The figure shows the details of the table in the search section 15, and FIGS. 4 and 5 are diagrams for explaining the operation of this embodiment. 1...Ground station, 2...Satellite station, 10.
...TDMA control section, 11... Transmission section,
12... Receiving unit, 13... Random sending unit, 14... Fixed allocation waiting unit, 15...
...Table search section, 16... Transmission buffer section, 17... Retransmission control section, 18...
...Traffic monitoring section, 19...Reception buffer section, 20...Antenna section, 151...
・Table, 152°153...Storage part. Agent Patent Attorney Uchihara Oto 4 Q Nitzuka. , 4 holes

Claims (1)

[Claims] In a communication system in which communication is performed between a plurality of communication stations each individually assigned a plurality of time slots on one communication line, each of the plurality of communication stations determines a range to be searched. a search range value storage means for storing a search range value indicated by the search range value; a first time slot on the communication line at the current time; and a second time slot that arrives after the first time slot by the amount of the search range value; determining means for determining whether or not the time slot assigned to the own station arrives during the period in which the time slot assigned to the own station arrives in response to the occurrence of data within the own station; When the time slot is detected, the data is sent onto the communication line in this time slot, and on the other hand, when the arrival of the time slot assigned to the own station is not detected, the data is sent to the communication line without waiting for the arrival of the time slot assigned to the own station. a data sending means for sending out on a communication line;
A communication system characterized by comprising: updating means for monitoring the traffic state of the communication line and updating the search range value stored in the storage means based on the traffic state.