Apparatus and method for using multiple communication paths in a wireless LAN

• US 5,768,531 A
• Filed: 03/27/1995
• Issued: 06/16/1998
• Est. Priority Date: 03/27/1995
• Status: Expired due to Term

• Current Assignee: Toshiba Corporation
• Original Assignee: Toshiba Corporation
• Inventors: Lin, Isabel Y.
• Primary Examiner(s): Harvey, Jack B.
• Assistant Examiner(s): Myers, Paul R.
• Application Number:
  US08/411,205
• Time in Patent Office: 1,177 Days
• Field of Search: 395/200.01, 395/200.02, 395/200.13, 395/200.72, 395/200.68-200.74, 340/825.03, 340/825.72, 370/54, 370/94.1, 370/95.1, 370/93, 370/16, 370/312, 370/349, 370/401, 379/221, 379/273, 375/202
• US Class Current: 709/242
• CPC Class Codes: H04W 28/14 using intermediate storage
• CPC Class Codes: H04W 76/10 Connection setup
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 92/18 between terminal devices

Abstract

An apparatus and method for reducing bottlenecks in a wireless communication system by allowing messages to be directly transmitted between wireless stations in certain circumstances instead of transmitting such messages through a centralized access point (AP) computer. Each AP computer maintains a connection list reflecting which stations are currently "connected" by wireless link to the AP by virtue of their being in its service area. As wireless stations move into and out of the service area for a particular AP, the AP updates this list, and any changes to the list are broadcast to all wireless stations in the service area. Thus, all stations (and the AP) have a current list of stations in the area. Each wireless station may periodically transmit a "keep alive" message to the AP, and thus the AP can determine which stations are in its area by noting which stations send such messages. Before transmitting a message, the transmitting station checks its copy of the connection list to determine whether the destination station is in the same service area or not. If it is in the same service area and the communication link with it is good, then the message is directly transmitted to the destination station. Otherwise, the message is transmitted to the AP for further relay to the destination station.

Claims

1. A method for transmitting a message between a first wireless station and a second wireless station, said first wireless station being in wireless communication with a first access point (AP) computer, the method comprising the steps of:

(1) storing in said first AP computer a connection list indicating whether said second wireless station is currently in communication with said first AP computer;

(2) broadcasting said connection list from said first AP computer;

(3) receiving and storing said connection list in said first wireless station;

(4) determining in said first wireless station, prior to transmitting said message, whether said second wireless station is currently in communication with said first AP computer by referencing said connection list stored in said step (3);

(5) responsive to a determination in said step (4) that said second wireless station is currently in communication with said first AP computer, transmitting said message directly from said first wireless station to said second wireless station; and

(6) responsive to a determination in said step (4) that said second wireless station is not currently in communication with said first AP computer, transmitting said message from said first wireless station to said first AP computer for subsequent transmission to said second wireless station.

2. The method of claim 1, further comprising the step of transmitting said message from said first AP computer along a backbone LAN to a second AP computer.

3. The method of claim 2, further comprising the step of receiving said message at said second AP computer and transmitting said message to said second wireless station.

4. The method of claim 1, further comprising the step of repeating step (2) on a periodic basis.

5. The method of claim 1, further comprising the step of transmitting a "keep alive" message between said first wireless station and said first AP computer, wherein step (1) comprises the step of updating said connection list in said first AP computer on the basis of failing to receive said "keep alive" message within a predetermined time period.

6. The method of claim 1, wherein step (1) comprises the step of deleting said second wireless station from said connection list stored in said first AP computer when no successful message communication with said second wireless station has occurred within a predetermined time period.

7. The method of claim 1, further comprising the step of updating said connection list stored in said first AP computer in response to receiving a "connect" message from said second wireless station.

8. The method of claim 1, wherein steps (5) and (6) each comprise the step of using an International Standards Organization (ISO) compliant layered message protocol.

9. The method of claim 1, further comprising the step of, in said first wireless station, updating a quality-of-service indicator for the second wireless station and, responsive to a determination that the quality-of-service indicator has fallen below a predetermined threshold, updating said connection list stored in said first wireless station.

10. The method of claim 9, wherein step (5) comprises the step of, prior to transmitting said message, determining whether peer-to-peer communication with said second wireless station is possible on the basis of a "peer-to-peer" indicator maintained in said first wireless station as a function of said quality-of-service indicator.

11. A machine for transmitting a message between a first wireless station and a second wireless station, said first wireless station comprising means for wirelessly communicating with a first access point (AP) computer, the machine comprising:

means for storing in said first AP computer a connection list indicating whether said second wireless station is currently in communication with said first AP computer;

means for broadcasting said connection list from said first AP computer;

means for receiving and storing said broadcasted connection list in said first wireless station;

means for, from said first wireless station, determining whether said second wireless station is currently in communication with said first AP computer by referencing said connection list stored in said first wireless station;

means for, responsive to a determination that said second wireless station is currently in communication with said first AP computer, transmitting said message directly from said first wireless station to said second wireless station; and

, responsive to a determination that said second wireless station is not currently in communication with said first AP computer, transmitting said message from said first wireless station to said first AP computer for subsequent transmission to said second wireless station.

12. The machine of claim 11, further comprising means for transmitting said message from said first AP computer along a backbone LAN to a second AP computer.

13. The machine of claim 12, further comprising means for receiving said message at said second AP computer and transmitting said message to said second wireless station.

14. The machine of claim 11, further comprising means for repeating said broadcast of said connection list on a periodic basis.

15. The machine of claim 11, further comprising:

means for transmitting a "keep alive" message between said first wireless station and said first AP computer; and

means for updating said connection list in said first AP computer on the basis of failing to receive said "keep alive" message within a predetermined time period.

16. The machine of claim 11, further comprising means for deleting said second wireless station from said connection list maintained in said first AP computer when no successful message communication with said second wireless station has occurred within a predetermined time period.

17. The machine of claim 11, further comprising means for updating said connection list stored in said first AP computer in response to receiving a "connect" message from said second wireless station.

18. The machine of claim 11, wherein said means for transmitting is implemented in an ISO compliant layered message protocol.

19. The machine of claim 11, further comprising means for, in said first wireless station, updating a quality-of-service indicator for the second wireless station and, responsive to a determination that the quality-of-service indicator has fallen below a predetermined threshold, updating said connection list stored in said first wireless station.

20. The machine of claim 19, wherein said means for transmitting determines, prior to transmitting said message, whether peer-to-peer communication with said second wireless station is possible on the basis of a "peer-to-peer" indicator maintained in said first wireless station as a function of said quality-of-service indicator.

21. An access point (AP) computer, comprising:

a data structure comprising a plurality of entries each including a wireless station address field and an activity flag;

a connection list broadcast function for broadcasting wireless station address data in said data structure to one of more wireless stations;

a second data structure comprising a plurality of entries each including a wireless station address field;

means for receiving said wireless station address data broadcasted from said AP computer and storing said wireless station address data extracted from said data structure into said second data structure; and

means for transmitting said message to said AP computer instead of to another wireless station when an address of said another wireless station is not among said wireless station address data contained in said plurality of entries in said second data structure.

22. A wireless station for communicating with a access pint (AP) computer and with a second wireless station, comprising:

a data structure comprising a plurality of entries each including a wireless station address;

a connection list update function which receives a connection list from said AP computer, extracts addresses therefrom, and stores said extracted addresses into said data structure; and

a transmit determination function, coupled to said data structure, for receiving a request to transmit a message to a second wireless station, searching said addresses extracted from said connection list received from said AP computer and stored in said data structure for an address corresponding to said second wireless station, and, responsive to a determination that said corresponding address is included in said data among those extracted and stored addresses, causing said message to be transmitted directly to said second wireless station.

23. The wireless station of claim 22, wherein said transmit determination function causes said message to be transmitted to said AP computer when said corresponding address is not included in said data structure.

24. The wireless station of claim 23, wherein said transmit determination function further determines, prior to said direct transmission to said second wireless station, whether said corresponding address has a communication path flag set to a value indicating that a "peer-to-peer" path is to be used and, responsive to said value indicating a "peer-to-peer" path, causing said direct transmission to said second wireless station.

25. The wireless station of claim 22, further comprising:

a "keep alive" timer; and

a "keep alive" handler, responsive to an expiration of said "keep alive" timer, for transmitting a "keep alive" message to said AP computer for the purpose of maintaining an entry for said wireless station in said connection list of said AP computer.

26. The wireless station of claim 22, wherein each entry in said data structure further includes a quality-of-service indicator, said wireless station further comprising means for updating said quality-of-service indicator in response to direct communications with said second wireless station.

27. The wireless station of claim 26, wherein in response to said quality-of-service indicator falling below a predetermined threshold, said means for updating sets a value in said data structure indicating that a "peer-to-peer" path is not to be used.

28. The wireless station of claim 22, wherein said transmit determination function is implemented in a media access layer of an ISO-compliant message protocol.

29. A wireless station for communicating with an access point (AP) computer and with a plurality of other wireless stations in communication with said AP computer, comprising:

a computer including a memory for storing a plurality of wireless station addresses of said wireless stations in communication with said AP computer and a plurality of indicators each indicating wether direct communication with a corresponding one of the other wireless stations is possible; and

a transmit determination function which, prior to transmitting a message to a selected station chosen from one of the plurality of other wireless stations, searches the memory for a wireless station address corresponding to the selected station, and, responsive to locating the corresponding address in the memory, checks one of the plurality of indicators to determine whether direct communication with the selected station is possible and, responsive to a determination that direct communication is possible, transmits the message directly to the selected stations and, responsive to a determination that direct communication is not possible, transmits the message to the AP computer.

30. The wireless station of claim 29, further comprising a memory update function which receives one or more wireless station addresses from the AP computer and stores them into the memory.

31. The wireless station of claim 29, further comprising a quality-of-service update function which, on the basis of repeatedly unsuccessful direct transmissions to one of the other wireless stations, changes one of the plurality of indicators in the memory to indicate that direct communication with that one wireless station is not possible.

32. The wireless station of claim 31, further comprising a receive function which, upon receiving a message from one of the plurality of other wireless stations, causes a corresponding quality of service indicator in the memory to be updated.

33. The wireless station of claim 32, wherein the receive function, in response to determining that the corresponding quality of service indicator has exceeded a threshold, changes one of the plurality of indicators in the memory to indicate that direct communication is possible.

34. The wireless station of claim 29, wherein the memory comprises a plurality of aging counters each associated with one of the plurality of wireless station addresses, wherein the transmit determination function causes one of the aging counters to be updated and, responsive to a determination that the aging counter has expired for a particular address, changes one of the plurality of indicators to indicate that direct communication with one of the other wireless stations corresponding to that particular address is possible.

35. The wireless station of claim 29, further comprising:

a "keep alive" timer; and

a "keep alive" handler, responsive to an expiration of the "keep alive" timer, for transmitting a "keep alive" message to the AP computer for the purpose of maintaining an entry in a connection list stored in the AP computer.

36. The wireless station of claim 29, wherein the transmit determination function is implemented in a media access layer of an ISO-compliant message protocol.

37. A system comprising the wireless station of claim 29 and an AP computer which is coupled to a wired LAN.

38. A method for transmitting messages from a first wireless station to a second wireless station in a network having a router, comprising the steps of:

determining in said router that said first and second wireless stations are in communication with said router;

storing respective addresses of said first and second wireless stations in a router memory of said router;

broadcasting said respective addresses from said router memory to said first and second wireless stations;

storing said second wireless station address in a first wireless station memory of said first wireless station;

transmitting a message directly from said first wireless station to said second wireless station responsively to said second wireless station address being in said first wireless station memory, whereby said route is bypassed.

39. A method as in claim 38, wherein said step of transmitting includes transmitting said message responsively to a quality of direct communication between said first and second wireless stations.

40. A network, comprising:

first and other wireless stations;

an access point (AP) computer;

said first wireless station having a memory holding a data structure having records, each record having a single address field;

said first wireless station having a controller programmed to enter address data, contained in a transmission of said address data from said AP computer to said first wireless station, into said address fields;

said controller being further programmed to transmit information from said first wireless station to a selected one of said other wireless stations only when an address of said selected one of said other wireless stations is contained in said address data contained in said transmission from said AP computer to said first wireless station.

41. A method for reducing bottlenecks in an access point (AP) computer in wireless communication with a group of wireless stations, comprising the steps of

(1) providing a capability for said wireless stations to communicate directly with each other, thereby bypassing said AP computer;

(2) determining in one of said wireless stations whether another of said wireless stations is in communication with said AP computer;

(3) determining in said one of said wireless stations whether direct communication between said one of said wireless stations and said another of said wireless stations is possible;

(4) transmitting a message directly between said one of said wireless stations and said another of said wireless stations only when said another of said wireless stations is determined, in step (4), to be in communication with said AP computer.

42. A method as in claim 41, wherein said step of determining whether another of said wireless stations is in communication with said AP computer includes periodically receiving in said one of said wireless stations addresses of said wireless stations in communication with said AP computer broadcast from said AP computer.