JPH0616599B2 - Initial synchronization method of TDMA communication method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a TDMA (Time Division Mul-tiple Access) satellite communication system, and particularly to establishing transmission burst synchronization of general stations participating in the system. For the initial synchronization method for.

[Conventional technology]

Generally, the TDMA satellite communication system is composed of at least one reference station and a plurality of general stations. The reference station periodically transmits a reference burst signal that serves as a reference for synchronization of the entire system. First, each general station first synchronizes to this burst signal, then synchronizes to this burst signal (burst synchronization), and after burst synchronization is completed, each data burst is allocated to the time slot assigned to each general station. Communication between stations is performed by transmitting signals.

Burst synchronization in each general station includes an open loop method and a closed loop method, but the present invention is premised on a closed loop burst period. Further, there are an open loop method and a closed loop method for the initial synchronization of the burst synchronization by the closed loop, but the present invention is premised on the initial synchronization by the open loop.

In the above-mentioned closed-loop synchronization, in each general station, the time difference between the reception timing of the reference burst signal and the transmission timing of the burst signal transmitted by the own station (timing at which the transmission burst signal of the own station is received by the own station) is measured. Then, the transmission burst timing synchronization is executed in each general station by controlling the transmission timing of the transmission burst signal of its own station so that the error resulting from this result becomes zero. According to this method, it is necessary to detect the time difference between the reception timing of the reference burst signal and the transmission timing of the burst signal transmitted by the own station.
This time difference cannot be known when the burst signal of the own station has not yet been transmitted. Therefore, it is necessary to obtain the timing for transmitting the burst signal of the own station by some method, and the operation performed for this purpose is the initial synchronization.

In the initial synchronization, the approximate transmission timing of the burst signal of the local station is obtained, and based on this, the burst signal for initial synchronization is transmitted toward the center of the time slot for initial synchronization allocated on the TDMA frame. Start by doing.

The open loop initial synchronization according to the present invention is a method of predicting a rough transmission timing for initial synchronization from the trajectory data of a communication satellite, a distance measurement result at a reference station, and the like, and starting the initial synchronization.

Conventionally, this type of open loop initial synchronization includes methods called sequential initial synchronization and parallel initial synchronization.

In the sequential initial synchronization, a time slot for initial synchronization is provided on the TDMA frame as a common time slot for each general station, and the initial synchronization of each general station is performed one station at a time.

On the other hand, in parallel initial synchronization, the time slot for initial synchronization is TD.
It is a method that is provided individually for each general station on the MA frame, and the initial synchronization of each general station is executed independently and in parallel.

[Problems to be solved by the invention]

However, when there are a large number of general stations participating in the system, in the above-described conventional sequential initial synchronization, the initial synchronization is executed one station at a time, so it takes time to execute the initial synchronization of all general stations. It has the drawback of being too much. Also, in parallel initial synchronization, if an attempt is made to individually assign a time slot for initial synchronization to all general stations, it is not possible to assign a time slot of a sufficient length to execute initial synchronization to all general stations. There are drawbacks.

[Means for Solving the Problem] In order to solve the above-mentioned drawbacks, the initial synchronization method of the TDMA communication method of the present invention uses a first initial synchronization time slot that can be commonly used by all general stations participating in the system. And a second initial synchronization time slot that is individually allocated to a small number of general stations and can be used exclusively by a small number of general stations, on the TDMA frame. Completion /
Means for monitoring the incomplete state, determining which general station of each general station should use the first and second time slots from the result of this monitoring and the operating state of the system, and sending a command And receiving a command is characterized in that it has means for performing an initial synchronization procedure for establishing transmission burst synchronization.

〔Example〕

FIG. 1 shows an embodiment of a TDMA frame format used for initial synchronization of the TDMA communication system according to the present invention. In the figure, R is a time slot for the reference burst signal, S ₁ ,
S ₂ , ..., S _n (n is the number of general stations) is a time slot for burst synchronization in a steady state after each general station completes initial synchronization. SAW is a time slot for successive initial synchronization, PAW
₁ , PAW ₂ , ... PAWi are parallel initial synchronization time slots. Also, the parallel initial synchronization time slots PAW ₁ and PA
W ₂ , ..., PAWi is also used as time slots D ₁ , D ₂ , ..., D _r for data burst signal transmission, and PAW ₁ is D ₁
, And D ₂ , PAW ₂ is used for D ₃ and D ₄ , and PAW _{3 and} below are used as well. Here, PAW ₁ cannot be used as a time slot for initial synchronization of general station 1 or 2 when either general station 1 or 2 is used for transmitting a data burst signal.

In addition, normally, the time slots S ₁ , S for burst synchronization are
The sequence of ₂ , ..., S _{n and} the sequence of the time slots D ₁ , D _2, ... D _n for transmitting the data burst are rare in one-to-one correspondence in this sequence, but this sequence will be omitted for the sake of simplicity. It is assumed that there is a one-to-one correspondence in order. That is, the station transmitting the burst signal S ₁ (general station 1) is the data burst D ₁
Station that transmits a burst signal S ₂ (general station 2)
Sends a data burst D ₂ , and so on.

FIG. 2 is a block diagram of an embodiment of the general station transmission synchronization control unit on the reference station side according to the present invention. In the figure, the reception state monitoring circuit 1 knows which general station has completed the initial synchronization from the burst signal 11 (signal 11) transmitted from the received general station, and uses the result as a signal 12 for initial synchronization. Output to the selection circuit 2. In the initial synchronization selection circuit 2, a general station requiring initial synchronization is selected based on the information indicating which general station is to be started up in the signal 12 and the TDMA communication system control information signal 13 (signal 13) output from the network controller. On the other hand, it is selected whether or not the sequential initial synchronization performs the parallel initial synchronization (a selection example will be described later), and the result is output to the general station transmission synchronization control circuit 3 as a signal 14. Based on the TDMA communication system control signal 13 (signal 13) and the signal 14 output from the network controller, the general station transmission synchronization control circuit 3 makes a final decision for each general station.
An instruction for sequential synchronization or parallel synchronization and other general station transmission synchronization control information are output as a signal 15. This signal 1
5 is inserted in the reference burst signal and transmitted to each general station.

FIG. 3 is an example of a transmission synchronization control unit for explaining initial synchronization on the general station side.

The initial synchronization procedure in the general station will be described with reference to this figure.

1) First, the reception timing signal 24 of the reference burst signal
With the (signal 24) as a reference, the transmission TDMA frame counter circuit 6 generates the transmission TDMA frame timing of the general station.

2) Next, the local station transmission synchronization control circuit 4 performs parallel / parallel operation according to the transmission synchronization control information signal 15 (signal 15) from the reference station.
Determine which initial synchronization to perform sequentially. As a result, the burst signal generation circuit 7 of the local station receives the signal 26.
Entered in. This circuit 7 is based on the counter output signal 28 (signal 28) from the transmission TDMA frame counter circuit, and is an area for executing the initial synchronization inputted by the signal 26 (parallel initial synchronization time slot / sequential initial synchronization time slot). ), The burst signal 29 for initial synchronization of the general station is sent toward the center of the line.

3) On the other hand, the result of determination as to which of the parallel / sequential initial synchronization is executed is also input to the local station burst signal position error detection circuit 5 via the signal 25. This circuit 5 has signal 2
5, it is possible to know the regular time difference between the initial burst signal of the local station and the reference burst signal. Further, the own station burst signal position error detection circuit 5 receives the reception timing signal 23 (signal 23) of the initial synchronization burst signal of the own station received by returning the satellite and the reception timing signal 24 (signal 24) of the reference burst signal. ) And the time difference between. By comparing the measured time difference with the above-mentioned normal time difference, the position error of the burst signal for initial synchronization of the own station from the normal position in the TDMA frame can be known, and the error information signal 27 (signal 27) is obtained. Sent through TD
Notify the MA frame counter circuit 6.

4) The circuit 6 corrects the transmission TDMA frame timing in the general station according to the signal 27.

5) The circuit 7 sends out the burst signal 29 for initial synchronization of its own station based on the counter output corrected in 4).

6) By repeating steps 1) to 3), the position error of the burst signal for initial synchronization of the own station may adversely affect the TDMA frame (for example, collide with the time slot for burst signal of another station). If the value does not reach the limit, the initial synchronization ends.

The system shown in FIG. 3 is also used for steady synchronization after the initial synchronization is established.

Next, an example of selecting the initial synchronization method in the general station will be described with reference to FIGS. 1 and 2.

First, the case where the initial synchronization of all general stations is started from now on will be described. The general station (transmission synchronization) controller 3 of the reference station receives the signals D and E from the general stations 1, 3, 5, and 5.
7: Output a parallel initial synchronization command to 2n-1
A command for sequentially executing initial synchronization is output to the general station 2.
(Here, it is assumed that the commands for sequentially executing the initial synchronization are sequentially output from the one with the smallest station number.) Each general station that has received the above command executes the initial synchronization as described above, and when it finishes, its own station Time slot S for synchronization burst signal
_A burst signal for synchronization is transmitted to the position of _i .

The reference station receives the synchronization burst signal and monitors it to monitor the end / non-end of the initial synchronization of each general station.

For example, if the synchronization burst signals of the general stations 5 and 7 can be detected, it is determined that the initial synchronization of the general stations 5 and 7 has ended, and the general stations 6 and 8 are instructed to execute parallel initial synchronization. Output. Further, if the synchronization burst signal of the general station 2 can be detected, it is determined that the initial synchronization of the general station 2 is completed, and the general station 4 is sequentially issued with an instruction for executing initial synchronization.

By executing such a procedure, the initial synchronization of the general stations is sequentially executed.

Next, the data burst signal causes time slot D
₁ and D ₃ are already in regular use, general station 2,
A case in which the initial synchronization is executed by 4 and 5 will be described.

The reference station outputs a command for sequential initial synchronization execution to the general station 2 and a parallel initial synchronization execution command for the general station 5. The general station 2 which has received the above-mentioned command executes the initial synchronization as described above, and when completed, transmits the synchronization burst signal to the position of the synchronization burst signal time slot S ₂ of its own station. At the reference station, the synchronization burst signal is detected at the position of S ₂ , and it is determined that the initial synchronization of the general station 2 is completed, and the general station 4 is sequentially instructed to execute the initial synchronization.

By performing such a procedure, general stations 2, 4,
An initial synchronization of 5 is performed.

〔The invention's effect〕

According to the present invention as described above, it is possible to realize an initial synchronization method that effectively uses a TDMA frame.

[Brief description of drawings]

FIG. 1 shows an embodiment of a TDMA frame format used in the initial synchronization system of the TDMA communication system according to the present invention, and FIG. 2 shows general station transmission synchronization on the reference station side of the initial synchronization system of the TDMA communication system according to the present invention. FIG. 3 is a block configuration diagram of an embodiment of the control unit, and FIG. 3 is a block configuration diagram of an embodiment of the transmission synchronization control unit of the own station on the general station side. 1 ... Reception state monitoring circuit, 2 ... Initial synchronization selection circuit, 3
…… General station transmission synchronization control circuit, 4 …… Self station transmission synchronization control circuit, 5 …… Self station burst signal position error detection circuit, 6 ...
… Transmit TDMA frame counter circuit, 7 …… Local station burst signal generation circuit.

Claims (1)

[Claims] 1. A first initial synchronization time slot that can be commonly used by all general stations participating in the system, and a small number of general station units are individually allocated, and a small number of general station units can be used exclusively. A second initial synchronization time slot is provided on the TDMA frame; the reference station monitors the initial synchronization completion / incompletion status of each general station, and based on this monitoring result and the system operation status, A general station for determining which of the first and second time slots is to be used by which general station and transmitting a command; the general station receiving the command is for establishing transmission burst synchronization. An initial synchronization method of the TDMA communication method, characterized in that it has means for executing an initial synchronization procedure.