Terminal capable of substituting for control station

Abstract

A terminal of the present invention comprises a control frame detection portion of detecting a control frame issued from a control station, a control frame memory portion of storing control information contained in the control frame, a substitute frame issuance determination portion of determining to issue a substitute frame when the control frame is not detected until a predetermined first time period is elapsed, and a substitute frame issuance portion of creating a frame which is the same as or equivalent to the control frame, as the substitute frame, based on the control information stored in the control frame memory portion when the substitute frame issuance determination portion determine to issue the substitute frame, and issuing the created substitute frame.

Description

TECHNICAL FIELD

[0001] The present invention relates to a terminal whose opportunity to access a communication medium is controlled by a control station, and more particularly, to a terminal capable of substituting for a control station. BACKGROUND ART

[0002] A communication system which utilizes media having a problem with communication quality is provided with a control station for controlling media access of other station(s) in order to utilize media as efficiently as possible. The other station is regarded as a controlled station, i.e., the control station and the controlled station have a master-slave relationship. In this manner, a central control type communication system protocol which can improve the efficiency of the entire communication system has been developed.

[0003] When such a protocol is applied to a wireless LAN, a power line communication system and the like, the efficiency of media access in the communication system is significantly influenced by communication qu...

Examples

first embodiment

[0060]FIG. 1 is a diagram schematically showing a structure of a whole communication system 1 according to a first embodiment of the present invention. The communication system 1 comprises a control station and a controlled station which is under a control of the control station. In FIG. 1, a terminal A is a control station which issues a signal for controlling an opportunity of media access by a terminal which participates in the communication system 1 (hereinafter referred to as a control frame). Terminals B, C and D are controlled stations. The control frame is also called a beacon. Note that the number of terminals in the present invention is not limited to that which is shown in FIG. 1. The terminals may be communicated with one another via wireless communication, wired communication or high-speed power line communication. A network to which the terminals are connected is not particularly limited.

[0061] The control station A periodically issues a control frame containing contr...

second embodiment

[0087] A terminal according to a second embodiment of the present invention is assumed to function both as a control station and as a controlled station. A terminal which tries to newly participate in a communication system determines whether to operate as a control station or as a controlled station before participating in the communication system.

[0088]FIG. 6 is a diagram showing a portion of a communication system 2 of the second embodiment. As shown in FIG. 6, the communication system 2 of the second embodiment is provided with a security management device 2a. The security management device 2a authenticates a terminal 200 which tries to participate in a communication system and manages a cryptographic key for a link between terminals or a cryptographic key for a whole communication system. Note that the security management device 2a may be provided in a control station which issues a control frame.

[0089] A user interface station 2c which has a user interface which imparts a ce...

third embodiment

[0141] A whole structure of a communication system according to a third embodiment of the present invention is similar to that of the first embodiment, and therefore, FIG. 1 is referenced. In the third embodiment, each terminal starts up either as a control station or as a controlled station. Note that the communication system may include a terminal which starts up only as a control station and a terminal which starts up only as a controlled station.

[0142] A hardware structure of a terminal of the third embodiment is similar to that of the first embodiment, and therefore, FIG. 3 is referenced.

[0143]FIG. 15 is a block diagram showing a functional structure of a terminal 300 of the third embodiment when executing a substitution control program. In FIG. 15, the terminal 300 comprises a frame transmission / reception portion 310, an operating mode management portion 320, a controlled station mode portion 330, and a control station mode portion 340.

[0144] The frame transmission / receptio...

TECHNICAL FIELD

[0001] The present invention relates to a terminal whose opportunity to access a communication medium is controlled by a control station, and more particularly, to a terminal capable of substituting for a control station. BACKGROUND ART

[0002] A communication system which utilizes media having a problem with communication quality is provided with a control station for controlling media access of other station(s) in order to utilize media as efficiently as possible. The other station is regarded as a controlled station, i.e., the control station and the controlled station have a master-slave relationship. In this manner, a central control type communication system protocol which can improve the efficiency of the entire communication system has been developed.

[0003] When such a protocol is applied to a wireless LAN, a power line communication system and the like, the efficiency of media access in the communication system is significantly influenced by communication qu...

Examples

first embodiment

[0060]FIG. 1 is a diagram schematically showing a structure of a whole communication system 1 according to a first embodiment of the present invention. The communication system 1 comprises a control station and a controlled station which is under a control of the control station. In FIG. 1, a terminal A is a control station which issues a signal for controlling an opportunity of media access by a terminal which participates in the communication system 1 (hereinafter referred to as a control frame). Terminals B, C and D are controlled stations. The control frame is also called a beacon. Note that the number of terminals in the present invention is not limited to that which is shown in FIG. 1. The terminals may be communicated with one another via wireless communication, wired communication or high-speed power line communication. A network to which the terminals are connected is not particularly limited.

[0061] The control station A periodically issues a control frame containing contr...

second embodiment

[0087] A terminal according to a second embodiment of the present invention is assumed to function both as a control station and as a controlled station. A terminal which tries to newly participate in a communication system determines whether to operate as a control station or as a controlled station before participating in the communication system.

[0088]FIG. 6 is a diagram showing a portion of a communication system 2 of the second embodiment. As shown in FIG. 6, the communication system 2 of the second embodiment is provided with a security management device 2a. The security management device 2a authenticates a terminal 200 which tries to participate in a communication system and manages a cryptographic key for a link between terminals or a cryptographic key for a whole communication system. Note that the security management device 2a may be provided in a control station which issues a control frame.

[0089] A user interface station 2c which has a user interface which imparts a ce...

third embodiment

[0141] A whole structure of a communication system according to a third embodiment of the present invention is similar to that of the first embodiment, and therefore, FIG. 1 is referenced. In the third embodiment, each terminal starts up either as a control station or as a controlled station. Note that the communication system may include a terminal which starts up only as a control station and a terminal which starts up only as a controlled station.

[0142] A hardware structure of a terminal of the third embodiment is similar to that of the first embodiment, and therefore, FIG. 3 is referenced.

[0143]FIG. 15 is a block diagram showing a functional structure of a terminal 300 of the third embodiment when executing a substitution control program. In FIG. 15, the terminal 300 comprises a frame transmission / reception portion 310, an operating mode management portion 320, a controlled station mode portion 330, and a control station mode portion 340.

[0144] The frame transmission / receptio...

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