JPS58129840A - Satellite communication system - Google Patents

Abstract

PURPOSE:To reduce the number of time slots necessary for a reservation signal, by securing time slots for data transmission by the reservation signal and then transmitting a data signal by using the time slots. CONSTITUTION:All terminal stations are grouped in (m) groups in such >=2 ways that each terminal station belongs to one group and each group contains nearly the same number of terminal stations. One time slot for a reservation signal is assigned to each group and inquiry polling for inquiring of stations whether terminal there is data to be transmitted or not is carried out, group by group, e.g. 1, 2- groups at every time with regard to all groups of the kinds.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a satellite communication system in which terminal stations on the earth communicate data between each other via a space station installed in outer space, and in particular, the present invention relates to a satellite communication system in which terminal stations on the earth communicate data with each other via a space station installed in outer space. The requirements for the reservation signal when using a method in which data communication is performed between terminal stations by first securing a time slot for data transmission using a reservation signal and then transmitting a data signal using that time slot. This is intended to reduce the number of slots.

A feature of satellite data communication is that it has a large transmission capacity, so it can be used jointly by many terminal stations on the ground. In the future, it may become commercially viable if a large number of terminal stations share use. In satellite data communications, data communication between terminal stations is carried out via a space station over a transmission channel, but in this case, if multiple terminal stations transmit data at the same time, mutual data interference may occur. A so-called data collision occurs, in which the correct data does not reach the desired partner station due to mutual interference. To deal with this, the time axis is divided into time slots (small pieces), and these time slots are further divided into time slots for reserved signals and time slots for data signals, and the reserved time slots are used first. Then, have each terminal station reserve how many time slots it needs to transmit data signals, prepare the reserved number of data signal time slots for that terminal station, and The terminal station transmits the data signal using the prepared data signal time slot. Furthermore, if each terminal station transmits a reservation signal every time a data signal that it wants to transmit occurs, a collision of reservation signals will occur. The conventional method was to allocate one to each.

However, in the conventional method described above, as the number of terminal stations on the ground side that share the satellite increases, the same number of time slots for reservation signals are also required, which reduces data transmission processing capacity and reduces the amount of time required for one terminal to use the satellite. In this case, the problem arises that the data transmission waiting time becomes long. Furthermore, considering the actual communication status, the data generation rate is not so high;
Even if one reservation signal time slot is provided for each terminal station, most of the time slots are expected to be wasted.

SUMMARY OF THE INVENTION An object of the present invention is to provide a satellite communication system that can solve the above-mentioned problems in the prior art, reduce the number of time slots allocated to reservation signals, and improve data communication processing capacity.

A feature of the present invention is that, in order to achieve the above object, all terminal stations are divided into multiple groups such that each terminal station belongs to one group and each group includes approximately the same number of terminal stations. Create at least two types of grouping to be divided, and perform polling to check whether there is data to be transmitted to the terminal station on a group-by-group basis, with one time slot allocated to the reservation signal per group. For each type, the process is performed sequentially for all groups within that type.

The present invention will be explained below with reference to the drawings.

FIG. 1 is an explanatory diagram of a signal control state during satellite data communication. In Figure 1, S is one station in space, T1 to TN are N terminal stations on earth, and polling is performed to check whether there is data to be transmitted to each terminal station. For management purposes, a control station C common to N terminal stations T1 to TN is installed on the earth. The control station C includes a circuit unit C1 that manages polling, and a circuit that manages the allocation of time slots for data transmission to the terminal station T that has responded to the polling (where i is any number from 1 to N). Part C2
and a circuit section C3 that controls signal processing in these circuit sections C1 and C2. In addition, each terminal station T1~
TN has a circuit section TR that outputs a response to polling.
1 to TRN, circuit units Ts1 to TsN that transmit data signals to other terminal stations using assigned data transmission time slots, and signal processing in these circuit units TR1 to TRN and T81 to TsN. Circuit section T.

1 to TON are provided, respectively.

In such a configuration, conventionally each terminal station T1 to TN
One reserved signal time slot is allocated for each terminal station, and the control station C is predetermined for each terminal station, regardless of whether there is a data signal to be transmitted. A method was adopted in which polling was performed for each station in order and responses were obtained. However, as mentioned above, this conventional method is wasteful.

Therefore, in the present invention, as shown in an example in FIG. 2, N terminal stations are divided into multiple groups, each group includes approximately the same number of terminal stations, and each A time slot for reservation signals is allocated and group polling as described below is performed. Furthermore, create at least two types of groupings, and first perform group polling on each group based on the first type of grouping, and then perform group polling on each group based on the second type of grouping. Perform group polling on the group. Group polling is continued in the same manner, and when all types of polling are completed, one cycle of polling is completed. In Figure 2, the number of groups is m,
This is the case where the number of types is 2. Since the number of groups is m, there must be approximately N/m terminal stations in the group.

1 means grouping according to the first type, and 2 means grouping according to the second type. The first type 1 is
It is divided into m groups of al, a2, a3, . . . a, and each group 131 to 8m includes approximately N/m terminal stations. The second type 2 is bl, b2,
It is divided into m groups b6, . . . bm, and each group b1 to bIll includes approximately N/m terminal stations. Then, each terminal station has group a1.
~am must be included in one of the groups, and must be included in any one of the blNbm groups. For example, in group polling, for the first type 1, a1 → a2 → a6...
・→am, and after completing these m group pollings, move on to the next second type 2, b1→b2→
It goes in the order of b6...→bm, and one cycle of polling work is completed. Therefore, the number of times of group polling in the case of FIG. 2 is 2×m times within one cycle. In response to this group polling, a terminal station belonging to the group issues a reservation signal if it has a data signal that it wants to transmit.

If there is only one terminal station in the group that outputs a reservation signal, the reservation signal is accepted, a time slot for data transmission is assigned, and data transmission becomes possible.

A terminal station that has finished transmitting data does not issue a reservation signal until the next data it wants to transmit occurs. In the above case, if there are two or more terminal stations outputting reservation signals in the same group, the reservation signals will collide. However, if the grouping according to the first type 1 and the grouping according to the second type 2 are made to have different combinations of terminal stations included in the groups, the reservation signal can be processed by group polling for the first type 1. Even if a collision occurs, during group polling for the second type 2, the number of terminal stations that output reservation signals will be the same as for the first type 1, except for the terminal station that newly generated 1 data. By group polling, the reservation signal is reduced by the number of terminal stations that are received, and the probability of reservation signal collision occurring is also reduced.

This will be explained in more detail using Tables 1 and 2. In other words, reservation signal collisions occur because two or more terminal stations in the same group are outputting reservation signals, but if the type of grouping is
It is clear from the specific examples in Tables 1 and 2 that the probability of occurrence of collision of reservation signals is reduced by setting the number of reservation signals to be equal to or greater than the number of types.

In Table 1, 100 terminal stations from T to T99 (x and y are O, and the general term is expressed as Txy, where both are 1-digit decimal numbers) are represented by X in Table 1. -X, and y in Table 2. -y, into 10 groups. In each group, for example, group X...terminal station T. O""09 group x1...Terminal station T10" T19 group y...Terminal station T.8~T, 8 group y・
...Terminal station T. 9 to T999, each of which includes 10 terminal stations.

1. The terminal station that has the data you want to send must be
, I learned T02, T12, T20, T29, °゛°,
T71, T88, T, 7. Group polling is performed in the order of Xo-+x1→... in Table 1, then y in Table 2.
It is performed in the order of o-+y1→... Group X. By group polling for terminal station T. A reservation signal is returned from 2. By group polling for group x1, a reservation signal is returned from terminal station T12.

Similarly, group polling for groups x7, x8, and X results in terminal stations T71, T88, and T9, respectively.
A reservation signal is returned from 7. However, in the example shown in Table 1, two terminal stations T2o and T29 output reservation signals due to group polling for group x2, so a collision of reservation signals occurs. Since a time slot for data transmission is assigned to a terminal station that has successfully received a reservation signal, it does not output a reservation signal for group polling according to grouping CYo-yq) in Table 2 below. During group polling according to Table 2, the terminal stations outputting reservation signals are T2o and T2. There are only two,
group y. By group polling for group y, terminal station T2 outputs a reservation signal, and by group polling for group y, terminal station T2. outputs a reservation signal, and a time slot for data transmission is assigned to each.

As shown in the examples in Tables 1 and 2, by using two types of grouping, 10 group polls for each type, 20 group polls in total, can cause reservation signal collisions. It becomes possible to normally receive the reservation signal without causing any error. In this case, since one reservation signal time slot is assigned to each group polling, a total of 20 reservation signal time slots may be sufficient. In contrast, in the conventional method, a time slot for reserved signals is allocated to each terminal station and polling is performed for each terminal station, so there are a total of 10
Zero reservation signal time slots must be prepared.

In the examples in Tables 1 and 2, we have described the case where there are two types of grouping, the number of groups is 10, and each group is divided into groups such that 10 terminal stations are included. There is no need to limit the number to 10,
For example, the number of groups may be 5, and each group may be divided into 20 terminal stations, or other various numbers of groups may be used.

In addition, as shown in Fig. 6, there are six types of grouping, the number of groups is r, and each group has N/r.
It is also possible to divide all N terminal stations into groups so as to include each terminal station (fraction is rounded up), and perform group polling a total of 6×r times.

In the example of Tables 1 and 2, to group 100 terminal stations, assuming that the number of types is 6, the number of groups in each type is 10, and the number of terminal stations in each group is 10, 1st
The type of grouping may be performed according to Table 1, the second type of grouping may be performed according to Table 2, and the sixth type of grouping may be performed, for example, according to Table 6 below.

Table 6 In this way, by increasing the number of types from two to three while keeping the number of groups in each type at 10, the number of group polling increases from 20 to 60, but As the number of combinations of terminals increases, the probability that two or more terminal stations in the combination will output a reservation signal becomes smaller.

That is, by increasing the number of types, the probability of collision of reservation signals becomes smaller.

As explained above, according to the present invention, a group polling method is adopted and all terminal stations are divided into groups, compared to the conventional method in which each terminal station is assigned one reserved signal time slot. Moreover, by using at least two types of grouping, it is possible to significantly reduce the number of time slots for reservation signals while reducing the probability of reservation signal collisions, which allows data to be divided into at least two types. Transmission processing capacity can be improved

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a signal control state in satellite data communication, and FIGS. 2 and 6 are explanatory diagrams of grouping of terminal stations in the present invention. Explanation of symbols 1.2.6... Grouping by first type, second type, and sixth type, respectively T1 to TN... Terminal station C... Control station S... Space station recovery Representative Patent Attorney Junnosuke Nakamura

Claims (1)

[Claims] A space station installed in outer space is used by multiple terminal stations on Earth to transmit data using time-divided time slots. First, a time slot for data transmission is reserved using a reservation signal. In a satellite communication system that performs data communication between stations by transmitting signals, multiple groups are used so that each terminal station belongs to one group, and each group has approximately the same number of terminal stations. Create at least two types of grouping to divide all terminal stations, poll the terminal stations to check whether there is data they want to send, and assign one time slot to each group for reservation signals. A satellite communication system characterized in that a single group performs each of the above types sequentially to all groups within that type.