JP2002124898A - Satellite communication ground station - Google Patents

Abstract

(57) [Problem] In a communication device using a time diversity system, when a plurality of mobile stations with different delay times communicate with one ground station device, the mobile station and the ground station have the same delay time. When communication is performed from a mobile station with different delay times to a ground station, a time diversity communication device corresponding to each delay time is required for the ground station. SOLUTION: A delay time switching device 4 is provided in a ground station,
When the ground station is waiting for reception, the delay time of the delay unit 3a on the receiving side is periodically changed, and the delay time of the mobile station 1a or 1b is made equal to the delay time of the delay unit 3a of the ground station. Serving stations.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite communication ground station using a time diversity system.

[0002]

2. Description of the Related Art The time diversity system is periodically generated when, for example, a satellite communication device equipped with a helicopter transmits radio waves to information toward a satellite when radio waves are momentarily interrupted by a helicopter rotor. This is a method for dealing with transmission data loss.

First, when performing data transmission, a data frame having a certain time length is set and data is transmitted (normal data). Then, the normal data transmitted once after the fixed frame transmission is transmitted again (delayed data), the normal data and the delayed data are compared on the receiving side, and the data which is not lost is selected. Here, the loss due to the momentary interruption is assumed to occur periodically, so in order to prevent both the normal data and the delay data from being lost, set the delay time according to the momentary interruption. I do.

FIG. 3 is a conceptual diagram of a device configuration of a communication system using a conventional time diversity system. In FIG. 3, 100a and 100b are mobile stations having different delay times. 101a is a conventional communication device corresponding to the delay time of the mobile station 100a in the ground station, and 101b is a conventional communication device corresponding to the delay time of the mobile station 100b.
In the conventional example, when a plurality of mobile stations having different delay times communicate with a ground station, a communication device corresponding to the delay time of the mobile station has to be installed.

FIG. 4 is a block diagram showing the configuration of a ground station in a communication system using the conventional time diversity system. A receiver 102 receives a radio signal from a mobile station. 103a and 103b are delay units for delaying reception data and transmission data by a fixed number of frames. 1
Reference numeral 05 denotes a data selection unit that compares normal data from the receiver 102 and delayed data from the delay unit 103c to select data with no loss. Reference numeral 106 denotes a demodulation unit that demodulates the data sent from the data selection unit 105 to original data using an error correction code such as a Viterbi decoding method. Reference numeral 110 denotes a delay processing unit that performs a delay process for combining transmission data and delay data obtained by delaying the transmission data and sends the result to the transmitter 111. In the transmitter 111, the delay processing unit 1
10 is converted into a radio signal and transmitted to the mobile station.

Next, the operation will be described. First, in the case of reception, when data is transmitted from a mobile station set to a specific delay time, the data is received by the receiver 102 via an antenna. After frequency conversion in receiver 102, the data signal is output to both delay section 103a and data selection section 105. The data delayed by the delay time set by the delay unit 103a is stored in the data selection unit 105.
, And compares the normal data and the delayed data sent from the receiver, selects data with no loss, and outputs the data to the demodulation unit 106. The demodulation unit 106 corrects and demodulates an error in the data sent from the data selection unit 105. For error correction, error correction using a convolutional code in Viterbi decoding or the like is common.

At the time of transmission, one of the transmission data is output directly to delay processing section 110 and the other is output to delay section 103b. After the transmission data is delayed by the delay unit 103b to be delayed data, the delay data is output to the delay processing unit 110. The delay processing unit 110 delays the directly input transmission data and delay data by the delay time and outputs the same delay data by the delay time to the transmitter 111 based on the time diversity scheme. Convert to frequency and transmit to satellite.

FIG. 5A is a diagram showing transmission / reception timing when the delay time is set to one frame in the time diversity system. Reference numeral 21a denotes normal data without delay, and reference numeral 21b denotes delayed data obtained by delaying the normal data 21a. As shown in the figure, the data of the time diversity system is synthesized by alternately sending the normal data and the delay data. Reference numeral 22 denotes an instantaneous interruption that occurs periodically. A data frame whose timing overlaps with the periodically generated instantaneous interruption 22 suffers a loss. Therefore, as shown in FIG. 5B, the normal data 21a is compared with the delay data 21b, and the data which has not been lost when the data is selected is selected.

FIGS. 6A and 6B show the case where the delay is two frames. The number of data delay frames and the length of the data frame are determined by the length of the instantaneous interruption.

In FIGS. 5 (a) and 5 (b) and FIGS. 6 (a) and 6 (b), the occurrence of instantaneous interruption and the start of a data frame are simultaneous for the sake of simplicity of explanation. The transmission and reception of data can be performed at any timing.

[0011]

In a communication device using the time diversity system of the prior art, the mobile station and the ground station must set the same delay time, and the mobile station and the ground station need to set the same delay time. When communicating toward the ground station, there is a problem that a time diversity communication device corresponding to each delay time is required for the ground station.

Also, in the case where the delay time of the diversity system can be switched by a single communication device at the ground station in advance, communication is started after the delay time setting is changed at the ground station in advance. Therefore, there is a problem that transmission cannot be started from the mobile station side first.

[0013]

A satellite communication ground station according to the present invention is a satellite communication ground station that communicates with a plurality of mobile stations each having a different delay time using a time diversity system. Delay means for delaying the received signal from the mobile station by a fixed delay time, comparison and selection means for comparing the received signal with the delayed signal and selecting one of the signals that is not lost, and demodulating data from the selected signal The demodulation means, the delay time switching control means for periodically switching the delay time of the receiver during reception standby, and when the demodulation means of the receiver can demodulate the data, the switching control of the delay time switching control unit is stopped. The reception detection means for fixing the delay time at the time of stop, the mobile station determination means for determining the mobile station from the delay time when the switching control is stopped by the reception detection means, and the determination result of the mobile station determination means. Identifying the delay time at the time of transmission to the mobile station from those having a delay time setting unit for setting a delay time of the transmission signal of its own station.

A satellite communication ground station that communicates with a plurality of mobile stations each having a different delay time by using a time diversity system, wherein a satellite received signal from the mobile station is delayed by a fixed delay time. Delay means, comparison and selection means for comparing a received signal with the delayed signal and selecting one of the signals not missing, demodulation means for demodulating data from the selected signal, and the mobile station periodically during reception standby The delay time switching control means for switching the delay time of the reception signal from the mobile station and the delay time of the transmission signal of the own station, it was determined whether or not data could be demodulated from the signal selected by the demodulation means, and the data was demodulated. In this case, there is provided a reception detecting means for stopping the switching control of the delay time switching control unit and fixing the switching time to the delay time at the time of the stop.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a block diagram showing the configuration of a satellite communication ground station using a time diversity system according to Embodiment 1 of the present invention. In the figure, reference numerals 1a and 1b denote mobile stations having different delay times. 2 is a receiver, 3a and 3b are delay units for delaying reception and transmission signals, 4 is a delay time switching control unit for periodically switching the delay time of the delay unit 3a when the ground station is waiting for reception, and 5 is a receiver from the receiver 2. The data selector 6 compares the normal data with the delay data from the delay unit 3a and selects the data which is not missing. The data selector 6 corrects the input data from the data selector 5 by using a Viterbi decoding method or the like. The demodulator 7 demodulates the demodulator 6 when the ground station waits for reception.
Is a reception detection unit that detects that the demodulation of the signal has been successfully performed, stops the switching control of the delay time switching control unit 4 in that case, and fixes the delay time at the stop. Reference numeral 8 denotes a mobile station discrimination unit that specifies a mobile station from the fixed delay time and outputs the mobile station to the delay time selection unit 9. Reference numeral 10 denotes a delay processing unit that combines transmission data with the transmission-side normal data and the delay data from the delay unit 3b according to the time diversity scheme, and sequentially outputs the synthesized data to the transmitter 11.

Next, an operation during standby for reception, which is a feature of the first embodiment, will be described. When the ground station is waiting for reception, the delay time switching control unit 4 switches the delay time of the delay unit 3a on the receiving side. The receiver 2 that has received the transmission signal from the mobile station 1a or 1b converts the frequency of the signal and outputs the signal to the data selection unit 5 and the delay unit 3a. The delay unit 3 a delays the input data according to the delay time set by the delay time switching control unit 4 and outputs the delayed data to the data selection unit 5. The data selection unit 5 compares the data directly input from the receiver 2 with the delayed data from the delay unit 3a, selects data with no loss, and outputs it to the demodulation unit 6. The demodulation unit 6 performs error correction by a Viterbi decoding method or the like, demodulates data, and outputs the data to the reception detection unit 7.

If the delay time of the delay unit 3a does not match the delay time of the mobile station at the origin, the order of the data frames input from the data selection unit 5 to the demodulation unit 6 does not match. If the order of the data frames is not correct, demodulation cannot be performed. Therefore, the reception detection unit 7 determines whether the demodulation by the demodulation unit 6 has been performed without any problem. If the demodulation can be performed, the switching control of the delay time is stopped. Thus, a signal is output to the delay time switching control section 4.

As described above, the delay time of the mobile station is made equal to the delay time of the ground station, and after the coincidence, communication is performed by the ordinary time diversity system.

Further, in addition to outputting a stop signal to the delay time switching control unit 4, the reception detecting unit 7 outputs a detection result to the mobile station discriminating unit 8, and the mobile station discriminating unit 8 moves from the detected delay time. The station is determined, and the result of the determination is output to the delay time selection unit 9. The delay time selection unit 9 sets the delay time of the delay unit 3b on the transmission side according to the determined mobile station. As described above, the delay time on the transmission side is set, and transmission is performed to the mobile station.

If the start of data reception from the mobile station is a little earlier than the timing of switching the delay time while the ground station is waiting for reception, the first part of the received data is lost. In this case, retransmission of data or synchronization of data transmission of the mobile station and reception of the ground station may be performed before transmitting main data. When the communication with a certain mobile station is completed, the mobile station returns to the reception standby state in which the delay time is periodically changed.

Embodiment 2 FIG. 2 is a block diagram showing a configuration of a satellite communication ground station using a time diversity system according to Embodiment 2 of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals. In FIG. 2, under the control of the delay time switching control unit 4, not only the receiver 2 but also the transmitter 11 periodically switches the setting of the delay time and waits for transmission.

When data from the mobile station is received, the demodulation unit 6 can demodulate the received data when the delay time setting of the receiver 2 is the same as the delay time of the mobile station, as in the first embodiment. The result of demodulation is detected by the reception detection unit 9, and as a result of the detection, if demodulation can be performed, the delay time switching control of the delay time switching control unit 4 is stopped, and the delay of the reception and transmission delay units 3a and 3b is delayed. Fix time. After fixing, transmission and reception are performed by a normal time diversity system.

By adopting the above device configuration, there is no need to install the mobile station discriminating unit 8 and the delay time selecting unit 9 as compared with the first embodiment, and a ground station with a simpler device configuration and lower cost can be provided. obtain.

[0024]

As described above, according to the present invention, a time diversity satellite communication ground station is provided with a delay time switching controller, which switches the delay time of the delay unit on the receiving side when waiting for reception, so that the signal of the mobile station can be obtained. , The switching control is stopped, and the delay time of the delay unit is adjusted to the delay time of the mobile station, so that one ground station device can communicate with a plurality of mobile stations having different delay times. Serving stations.

In the time diversity type satellite communication ground station, a delay time switching controller is provided to switch the delay time of the reception side delay unit and the transmission side delay unit during reception standby to receive the mobile station signal. The switching control is stopped to adjust the delay time of the delay unit and the delay unit to the delay time of the mobile station, thereby enabling one ground station apparatus to communicate with a plurality of mobile stations having different delay times. Serving stations.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a device configuration of a satellite communication ground station using a time diversity scheme according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram illustrating a device configuration of a satellite communication ground station using a time diversity scheme according to Embodiment 2 of the present invention.

FIG. 3 is a conceptual diagram of a satellite communication system using a conventional time diversity system.

FIG. 4 is an apparatus configuration diagram of a satellite communication ground station using a conventional time diversity system.

FIG. 5A is a diagram illustrating a data frame configuration when a delay is set to one frame in a time diversity system,
(B) is a diagram comparing the normal data and the delay data when the delay is one frame.

FIG. 6A is a diagram illustrating a data frame configuration when a delay is set to two frames in a time diversity system,
(B) is a diagram comparing the normal data and the delay data when the delay is two frames.

[Explanation of symbols]

1 mobile station, 2 receiver, 3a receiving side delay section, 3b transmission side delay section, 4 delay time switching control section, 5 data selection section, 6 demodulation section, 7 reception detection section, 8 mobile station discrimination section, 9 Delay time selector,
10 delay processing unit, 11 transmitter, 21a normal data, 21b delay data, 22 momentary interruption,
100 Conventional time diversity mobile station, 101
Conventional time diversity communication apparatus, 102 conventional receiver, 103a conventional receiving-side delay unit, 1
03b Conventional transmission-side delay unit, 105 conventional data selection unit, 106 conventional demodulation unit, 110 conventional delay processing unit, 111 transmitter.

Claims (2)

[Claims] 1. A satellite communication ground station which communicates with a plurality of mobile stations each having a different delay time using a time diversity system, wherein data received from the mobile station is delayed by a predetermined time. Delay means for generating delay data, comparison / selection means for selecting one of the received data and the data which is not defective in the delay data, demodulation means for demodulating the selected data, and periodic reception during reception standby. Delay time switching control means for switching the delay time of the device, reception detection means for stopping the switching control of the delay time switching control section when the data can be demodulated by the demodulation means, and fixing the switching control to the delay time at the time of stoppage A mobile station discriminating means for discriminating the mobile station from the delay time when the switching control is stopped by the reception detecting means, and moving from the own station based on a discrimination result of the mobile station discriminating means. A satellite communication ground station comprising: a delay time setting means for specifying a delay time for transmission to a station and setting a delay time of transmission data of the own station. 2. A satellite communication ground station which communicates with a plurality of mobile stations each having a different delay time using a time diversity system, wherein a signal received from the mobile station is delayed by a predetermined time. Delay means for generating delay data, comparison and selection means for selecting any one of the received data and the data which is not lost, demodulation means for demodulating the selected data, and the delay means for periodically waiting during reception. Delay time switching control means for switching the delay time of the transmission signal of the own station while switching the delay time of the means, when data can be demodulated by the demodulation means, stop switching control of the delay time switching control unit, A satellite communication ground station, comprising: reception detection means for fixing a delay time at a stop.