Wireless LAN device and communication mode switching method

• US 20070140191A1
• Filed: 03/31/2006
• Published: 06/21/2007
• Est. Priority Date: 12/16/2005
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Kojima, Yuji
• Granted Patent: US 7,966,036 B2
• Time in Patent Office: Days
• US Class Current: 370/338
• CPC Class Codes: H04W 76/23 Manipulation of direct-mode connections
• CPC Class Codes: H04W 8/005 Discovery of network devices, e.g. terminals
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks
• CPC Class Codes: H04W 88/08 Access point devices
• CPC Class Codes: H04W 88/12 Access point controller devices

Abstract

A wireless LAN device for lessening failure in switching from infrastructure mode to ad-hoc mode. A radio wave coverage storage stores coverage information about coverage of radio waves amongst access points. A terminal information storage stores terminal information about terminals associated with the access points. A packet receiver receives, via the access points, a packet transmitted from any of the terminals in infrastructure mode. An access point acquisition unit looks up the terminal information storage, based on terminal information about originating and destination terminals contained in the packet, to identify access points with which the terminals are associated. A radio wave coverage decision unit looks up the radio wave coverage storage to determine whether the identified access points are within each other'"'"'s coverage of radio waves. A communication mode switch switches the communication mode of the originating and destination terminals to ad-hoc mode in accordance with the determination result.

Claims

1. A wireless LAN device for controlling a plurality of access points, comprising:

radio wave coverage storage means for storing radio wave coverage information about coverage of radio waves amongst the access points;

terminal information storage means for storing terminal information about terminals associated with the individual access points;

packet receiver means for receiving, via the access points, a packet transmitted from any of the terminals in infrastructure mode;

access point acquisition means for looking up the terminal information storage means, based on terminal information about an originating terminal and a destination terminal contained in the packet, to identify an access point with which the originating terminal is associated and an access point with which the destination terminal is associated;

radio wave coverage decision means for looking up the radio wave coverage storage means, to determine whether or not the access points with which the originating terminal and the destination terminal are respectively associated are within each other'"'"'s coverage of radio waves; and

communication mode switch means for switching mode of communication between the originating terminal and the destination terminal to ad-hoc mode in accordance with a result of the determination by the radio wave coverage decision means.

2. The wireless LAN device according to claim 1, wherein the communication mode switch means causes the packet transmitted in the infrastructure mode to be included in one of ad-hoc mode switching instruction packets to be transmitted to the originating and destination terminals.

3. The wireless LAN device according to claim 2, wherein the communication mode switch means establishes a tunnel with each of the access points and encapsulates the packet into the ad-hoc mode switching instruction packet in a manner such that a sequence number of the packet is retained.

4. The wireless LAN device according to claim 1, wherein, if failure information indicating that communication in the ad-hoc mode has failed is received from the originating or destination terminal after the mode of communication is switched to the ad-hoc mode, the communication mode switch means switches the mode of communication between the originating and destination terminals to the infrastructure mode.

5. The wireless LAN device according to claim 1, further comprising failure information storage means for storing the terminal information about the originating and destination terminals which failed in communication in the ad-hoc mode,

wherein the communication mode switch means prevents the mode of communication between the originating and destination terminals registered in the failure information storage means from being switched to the ad-hoc mode.

6. The wireless LAN device according to claim 5, wherein the failure information storage means deletes the terminal information about the originating and destination terminals after a lapse of a predetermined time period.

7. The wireless LAN device according to claim 1, further comprising packet storage means for storing the packet transmitted in the infrastructure mode.

8. The wireless LAN device according to claim 7, further comprising radio wave non-coverage information receiver means for receiving, from the terminals, radio wave non-coverage information which is indicative of non-coverage of radio waves between the terminals and which is generated based on RTS/CTS frames exchanged between the terminals and the access points;

and

radio wave non-coverage information storage means for storing the radio wave non-coverage information,

wherein the packet storage means does not store the packet transmitted between the originating and destination terminals registered in the radio wave non-coverage information storage means.

9. The wireless LAN device according to claim 1, wherein the radio wave coverage information stored in the radio wave coverage storage means is generated through auto-calibration of the access points.

10. A communication mode switching method for a wireless LAN device which is adapted to control a plurality of access points, comprising the steps of:

receiving, via the access points, a packet transmitted from any of terminals in infrastructure mode;

looking up terminal information storage means storing terminal information about the terminals associated with the individual access points, based on terminal information about an originating terminal and a destination terminal contained in the packet, to identify an access point with which the originating terminal is associated and an access point with which the destination terminal is associated;

looking up radio wave coverage storage means storing radio wave coverage information about coverage of radio waves amongst the access points, to determine whether or not the access points with which the originating terminal and the destination terminal are respectively associated are within each other'"'"'s coverage of radio waves; and

switching mode of communication between the originating terminal and the destination terminal to ad-hoc mode in accordance with a result of the determination.