JPH02279030A - Access control system for satellite communication system of travelling object - Google Patents

Abstract

PURPOSE:To attain access control without stopping the transmission of access information and to simplify the control of a mobile station by controlling an SS(spread spectrum) synchronizing code of a mobile station at a mobile station. CONSTITUTION:When a mobile station 30 makes communication, a line controller 30 of the mobile station 30 uses a line controller 14 of a stationary station 10 to switch the SS synchronizing code of the mobile station 30 set for a common control channel into a communication channel SS synchronizing code sent from a stationary station based on the access information obtained through the common control channel. Then the mobile station 30 makes communication with a satellite 1 via a communication channel MODEM 32. When the communication is finished, the line controller 33 of the mobile station 30 returns the communication channel SS synchronizing code of the mobile station 30 to the SS synchronizing code of the common control channel MODEM 13 of the stationary station 10 to obtain the access information again from the stationary station 10. Thus, the mobile station 30 attains the reception of the access information and the communication with the control of the code only, and since the stationary station 10 is provided with the control channel MODEMs 12, 13, the control is simplified.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an access method for a mobile satellite communication system, and in particular to a spread spectrum sharing method (SSMA).
This paper relates to an access control method for a mobile satellite communication system in a star configuration network using

[Conventional technology]

Mobile satellite communication systems include fixed stations and mobile stations that transmit information via satellites with accessible lines. In such a mobile satellite communication system, the network configuration may be in a star configuration.

In this case, if the number of lines that can simultaneously access the satellite's transponder is smaller than the number of mobile stations, saturation of the transponder becomes a problem. In a star configuration, the mobile station cannot perform access control unless it receives information about the line usage status from the fixed station. In particular, in access control in a star configuration network using SSMA, access availability, SS (spread spectrum)
The fixed station needs to report information such as code settings and SS code synchronization to each mobile station.

A first method for performing such access control is to provide a dedicated control channel in addition to the communication channel to report control information from the fixed station to the mobile station.

Furthermore, as a second method for realizing these without providing a dedicated control channel, there is an access control method that has already been proposed. In this case, the mobile station's line controller sequentially changes the SS code of the mobile station's modulator and demodulator to perform control to search for an empty channel that is not used for communication. and,
The fixed station line controller uses this free channel to send access information to the mobile station, and when the transmission is stopped, the access control system allows the mobile station to connect.

[Problem to be solved by the invention]

Among the conventional access control methods described above, the first method reduces the number of usable communication channels by providing a dedicated control channel, and requires the mobile station to have a control channel modem in addition to a communication channel modem. There is a drawback.

Furthermore, in the second method, control for searching for an empty channel by sequentially changing the SS code of the mobile station's line controller is complicated, and the scale of the mobile station becomes large. The drawback is that when the fixed station's line controller grants connection to the mobile station, the transmission of access information from that modem is stopped and the transmission of access information is transferred to another modem, resulting in complicated control. be.

An object of the present invention is to provide an access control method for a mobile satellite communication system that can eliminate such drawbacks, simplify the control of mobile stations, and perform access control without stopping the transmission of access information. .

[Means to solve the problem]

The present invention provides an access control method for a mobile satellite communication system in which a fixed station in a star configuration network and a plurality of mobile stations communicate via accessible satellite communication, wherein the fixed station communicates with a satellite line. a modulation and demodulation unit for a communication channel; a modulation and demodulation unit for a common control channel that provides satellite line access information to an empty satellite line; and a line control unit that provides access information, and the fixed station receives the access information from the fixed station when the code of the modulation and demodulation unit for the common control channel is set, and a mobile station modulation/demodulation unit that communicates with a satellite line when a code is set; and a mobile station line control unit that sets the code of the fixed station modulation/demodulation unit to the mobile station modulation/demodulation unit. It is characterized by

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

The access control method of this mobile satellite communication system consists of a satellite 1 equipped with an accessible line, a fixed station 10 that provides information on the usage status of the satellite line, and information from the fixed station 10 via the satellite 1. Mobile stations 20 to 40 for communication
It is equipped with

These mobile stations M1, fixed station 10, and mobile stations 20 to 40 form a star configuration network using SSMA. Note that in this embodiment, the number of accessible satellite lines in the network is smaller than the number of mobile stations.

The fixed station 10 includes an antenna 11, a modem 12, 13, and a line controller 14.

The mobile station 30 includes an antenna 31, a modem 32, and a line controller 33. The same applies to mobile station 20.40.

In such an access control system for a mobile satellite communication system, the fixed station modem 12 is a communication channel modem that transmits information with the antenna 11. The number of modulators 12 is the same as the number of accessible satellite lines.

The modulator/demodulator 13 is a modulator/demodulator for a common control channel that transmits information with the antenna 11 .

The line controller 14 is a line controller for a fixed station, which is connected to the communication channel modem 12 and the common control channel modem 13.

The modulator/demodulator 32 of the mobile station 30 is a modulator/demodulator for a communication channel that transmits information with the antenna 31 .

The line controller 32 is a mobile station line controller connected to the communication channel modem 32.

Next, the operation of this embodiment will be explained.

When there are two or more free channels on the satellite line, for example when the mobile station 30 does not communicate, the mobile station 300 line controller 3
3 sets the SS synchronization code of the communication modem 32 of the mobile station 30 to the SS synchronization code of the common control channel modem 13 of the fixed station 10. On the other hand, the fixed station 100 line controller 14 sends access information using an empty channel. That is, the line controller 14 of the fixed station 10
An empty channel is used as a common control channel, and access information is sent to the satellite l via a modulator/demodulator 13 for the common control channel. Mobile station 30 receives access information from satellite 1. The received access information is input to the line controller 33 via the communication channel modem 32.

Next, when the mobile station 30 performs communication, the line controller 33 of the mobile station 30 uses the access information for the common control channel based on the access information obtained from the line controller 14 of the fixed station 10 through the common control channel. The previously set SS synchronization code of the mobile station 30 is switched to the SS synchronization code for the communication channel sent from the fixed station. The mobile station 30 then communicates with the satellite via the communication channel modem 32. When the communication ends, the line controller 33 of the mobile station 30
The communication channel SS synchronization code is returned to the SS synchronization code of the common control channel modulator 13 of the fixed station 10.

As a result, the mobile station 30 obtains access information from the fixed station 10 again.

By the way, there is one free channel that is not used for communication.
For example, when a communication request is issued from the mobile station 30, the line controller 14 of the fixed station 10 sends information indicating that the mobile station with which it is not communicating is inaccessible through the common control channel. The line controller 14 of the fixed station 10 then sends the access information to the requesting mobile station 30. The mobile stations that are not communicating know that there are no more accessible satellite lines and wait until the mobile station 30 that is communicating ends the communication.

In this way, in this embodiment, by controlling the mobile station's SS synchronization code, the mobile station can have a dedicated control channel in addition to the communication channel, and can have only a device that controls the SS synchronization code. It is possible to avoid having a control modem and to simplify the control of the mobile station's line controller.

In addition, by having a common control channel modem in the fixed station, the control of the line controller of the fixed station can be simplified.
It waits to send access information only when there is one free channel, and does not stop sending access information at other times (access control is possible).

(Effects of the Invention) As explained above, according to the present invention, the mobile station does not require a control modem because the modulation and demodulation unit can receive and communicate access information only by controlling the code.
Since the fixed station is equipped with a modulation/demodulation section for control channels, it has the effect of simplifying control.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. lO・・・Fixed station 11, 31... antenna 12, 13.32...modulator/demodulator 14, 33...Line controller 20-40...mobile station

Claims (1)

[Claims] (1) In an access control method for a mobile satellite communication system in which a fixed station in a star configuration network and a plurality of mobile stations communicate via accessible satellite communication, the fixed station performs communication with a satellite line. a modulation/demodulation unit for a channel; a modulation/demodulation unit for a common control channel that provides satellite line access information to an empty satellite line; and a modulation/demodulation unit for a common control channel that controls communication between the respective modulation/demodulation units and accesses the modulation/demodulation unit for the common control channel. and a line control unit that provides information, and the fixed station receives access information from the fixed station when the code of the modulation and demodulation unit for the common control channel is set, and A mobile station modem unit that communicates with a satellite line when a code is set; and a mobile station line control unit that sets the code of the fixed station modem unit to the mobile station modem unit. An access method for a mobile satellite communication system characterized by: