JPS61202541A - Random access system - Google Patents

Abstract

PURPOSE:To decrease collision probability of data with priority by specifying a assigned channel in response to the priority provided to the data from each communication station and setting many channel numbers possible for assignment as the priority is higher. CONSTITUTION:Data from earth stations 101-10n are assigned to any of plural time slots A line is provided with time slots N1, N2, N3 arranged in time series in succession to a reference burst D0 from a line control station 30. The data from each earth station are classified into groups A, B, C in the higher order of communication priority. Then the date belonging to the group A is assigned to any of the time slots N1, N2, N3, the data belonging to the group B is assigned to any of the N2, N3 and the data belonging to the group C is assigned only to the N3.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention provides a random communication system in which, for example, a plurality of communication stations randomly transmit data on time slots, and when there is a data collision, data is randomly retransmitted. Regarding access methods.

[Technical background of the invention and its problems]

When a large number of earth stations communicate via a satellite, there is a limit to the number of communication lines on the repeater installed on the satellite.
Communication channels need to be used efficiently.

Therefore, in satellite communication systems with a large number of earth stations with relatively low traffic, the demand assignment line control method, which sets up a line every time there is a line connection request, has recently attracted attention because of its high line utilization efficiency.

Among them, an earth station transmits data to random time slots in synchronization with a reference burst from a central control station.
The random access method, in which data is retransmitted to a time slot again after a random time interval when a collision with a signal from another earth station is detected, is used in satellite communication because it is easy to control. It is often used as an access method.

However, in the conventional random access method, data from each earth station is assigned to time slots completely randomly, so each data certainly has an equal probability of collision, but if there is data that you want to prioritize, There is a drawback that the collision probability is the same for data that should be prioritized and data that is not. Therefore, as the traffic increases, the probability of collision of priority data also increases, and this method cannot necessarily be said to be effective when communication of high-priority data is required, such as in broadcast communication, for example. .

[Purpose of the invention]

The present invention was made in view of these problems, and its purpose is to provide a highly flexible random access method that can significantly reduce the collision probability of data to be prioritized compared to the conventional method. There is a particular thing.

[Summary of the invention]

The present invention provides random access in which a communication line is divided into a plurality of channels, a plurality of communication stations randomly transmit data to the plurality of channels, and if there is a data collision, the data is randomly retransmitted. In the method, a priority is set for data from each communication station, channels that can be allocated are specified according to this priority, and the number of channels that can be allocated is set to be larger for data with a higher priority. It is characterized by

〔Effect of the invention〕

According to the present invention, a priority is set for each data, and the number of channels that can be allocated to data increases as the priority increases. This can be significantly reduced compared to that, and the average connection delay time of high-priority data can be shortened. As a result, by giving priority to urgent data, for example, it becomes possible to transmit and receive that data earlier than other data.

Moreover, according to the present invention, channels that can be allocated are simply specified according to the priority of data, and the ease of control, which is an advantage of the conventional random access method, is not impaired.

[Detailed description of the invention]

Hereinafter, details of the present invention will be explained with reference to embodiments shown in the drawings.

FIG. 1 is a diagram showing the configuration of a satellite communication system according to this embodiment. Here, a plurality of earth stations 101, io
2.-, Ions communicate with each other via the satellite 20, each earth station 101-10. Line control station 3
A random access method when transmitting line connection request data to 0 will be explained.

Data from each of the earth stations 10i to 10n is allocated to one of a plurality of time slots so that one frequency is time-divisionally shared on the line. In this example, as shown in FIG. 2, the line starts with a reference burst [)0 from the line control station 3G, followed by three chronologically arranged time slots N! , N2, and N:1.

Data sent from each earth station is classified into, for example, three groups depending on communication priority.

That is, each data is grouped into group A, which has the highest priority, group B, which has the next highest priority, and so on. Group C, the least advanced
are categorized. This classification is such that, for example, broadcast communication is given priority over individual communication. Each of these groups A
The data included in -C is allocated to the following time slots, for example.

That is, data belonging to group A is stored in time slot Nt.
, N2, and N3. Further, data belonging to group B is in time slot N2. N
It can be assigned to any one of 3. Furthermore, data belonging to group C can only be assigned a time slot to N3.

In such a system, as shown in FIG. 3(a), when data D1 is assigned to time slot N1 and data D2 is assigned to time slot N2, the lines belonging to each group A to C Consider the case where connection request data is sent. First, if the transmitted data [)3 is the data with the lowest priority belonging to group C, the only time slot that can be assigned is N3. However, since data D2 has already been assigned to time slot N3, data D2 is repeatedly retransmitted until time slot N3 becomes vacant. When data D4 belonging to group B is transmitted next, the assignable time slots are N2 and N3. However, since both of these time slots N2 and N:l are in use, the data D4 is repeatedly and randomly retransmitted until either time slot N2 or N3 becomes vacant. On the other hand, when data D5 belonging to group A with the highest priority is transmitted, the assignable time slots are N1 to N. Therefore, in this case, since the time slot N1 is vacant, the data D5 is allocated to this time slot, and the communication line of the earth station that sent this data D5 is secured.

For example, as shown in FIG. 6(b), if data D6 is currently assigned to time slot N3, data D7 belonging to group C will be in a waiting state, and data DB belonging to group B will be in the waiting state. In time slot N2,
Also, data D9 belonging to group A is in time slot N.
1 respectively.

In this way, according to the random access method according to this embodiment, the collision probability of urgent data can be increased compared to other data, and a highly flexible communication system can be established.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible. For example, in the above embodiment, the data is divided into three groups, but the number of groups and the time slot to which data belonging to each group is assigned are completely arbitrary.

In this case, there may be overlap in the time slots allocated between one group and another group. As for time slot allocation when there is no overlap, for example, a method of allocating a group of time slots of a certain length from the reference burst to one group, and allocating a group of time slots of the next length to another group is considered. It will be done.

Further, in the above embodiments, a time division multiple access system in which a plurality of channels are time slots has been described as an example, but the present invention can also be applied to a frequency division multiple access system. Further, the present invention is not particularly limited to wireless communication, but can also be applied to wired communication.

FIG. 2 is a diagram showing the time slot arrangement in the system, and FIG. 3 is a diagram for explaining the operation of the system.

101~ion...Earth station, 20...Satellite, 30.
...Line control station, N1-N3...Time slot, D
o...Reference burst, D1~Dyo...data.

Applicant's agent Patent attorney Takehiko Suzue 1st rj! G? PJ2 Diagram O Horn L-no'shi -1-1-111 3rd (a) n Do (b)

Claims (1)

[Claims] In the random access method, a communication line is divided into a plurality of channels, a plurality of communication stations randomly transmit data to the plurality of channels, and when there is a data collision, the data is randomly retransmitted. Random access characterized in that a priority is set for data from each communication station, channels that can be assigned are specified according to this priority, and the number of channels that can be assigned is set to be larger for data with a higher priority. method.