Channel scanning

• US 8,553,617 B1
• Filed: 12/01/2010
• Issued: 10/08/2013
• Est. Priority Date: 12/01/2010
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Shmidt, Dmitry
• Primary Examiner(s): Ly, Anh-Vu
• Assistant Examiner(s): LOPEZ-VARGAS, GUSTAVO E
• Application Number:
  US12/957,778
• Time in Patent Office: 1,042 Days
• Field of Search: 455/434, 455/456.1, 455/450.1, 455/457, 455/160.1, 370/254, 370/256, 370/328, 370/434, 370/433, 370/252, 370/310, 370/312, 370/28, 370/389, 370/392
• US Class Current: 370/328
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 4/021 Services related to particular areas, e.g. point of interest [POI] services, venue services or geofences
• CPC Class Codes: H04W 4/20 Services signaling; Auxiliary data signalling, i.e. transmitting data via a non-traffic channel
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for channel scanning. In one aspect, a method includes, while maintaining an association with a first access point on a first channel during first, second, and third consecutive time slices: (i) monitoring, by a client device, a single second channel during the first time slice and the third time slice, and (ii) monitoring, by the client device, the first channel during the second time slice; receiving a beacon from a second access point during the first time slice or the third time slice; and determining a property of the client device or the second access point using the beacon, without using the beacon to determine whether to establish an association with the second access point.

Claims

1. A computer-implemented method comprising:

switching a transceiver of a client device between (i) a first channel, through which a logical connection between the client device and a first access point is established, and (ii) a second channel, through which a second access point broadcasts beacons, wherein a logical connection is not established between the client device and the second access point;

receiving a beacon over the second channel from the second access point while maintaining the logical connection between the client device and the first access point, and without establishing a logical connection between the client device and the second access point; and

determining a property of the client device or the second access point using the beacon received over the second channel from the second access point while maintaining the logical connection between the client device and the first access point, and without establishing a logical connection between the client device and the second access point.

2. The computer-implemented method of claim 1, wherein switching the transceiver of the client device comprises alternating, in a series of multiple consecutive time periods, between monitoring the first channel with the transceiver during one of the consecutive time periods and monitoring the second channel with the transceiver during another of the consecutive time periods.

3. The computer-implemented method of claim 2, wherein monitoring the second channel with the transceiver comprises monitoring the second channel for time periods having a duration different from a duration of time periods in which the first channel is monitored.

4. The computer-implemented method of claim 3, wherein monitoring the second channel comprises monitoring the second channel for time periods having a duration longer than the duration of time periods in which the first channel is monitored.

5. The computer-implemented method of claim 4, wherein monitoring the second channel comprises monitoring the second channel for time periods having a duration at least twice the duration of time periods in which the first channel is monitored.

6. The computer-implemented method of claim 4, wherein monitoring the second channel comprises monitoring the second channel for time periods having a duration approximately five times the duration of time periods in which the first channel is monitored.

7. The computer-implemented method of claim 2, wherein data is exchanged between the client device and the first access point while monitoring the first channel with the transceiver.

8. The computer-implemented method of claim 2, wherein monitoring the second channel with the transceiver comprises monitoring the second channel in time periods that each have each have a duration greater than a beacon transmission interval of the first access point.

9. The computer-implemented method of claim 8, wherein monitoring the second channel with the transceiver comprises monitoring the second channel in time periods that each have each have a duration less than an association timeout interval of the first access point.

10. The computer-implemented method of claim 1, further comprising:

extracting information from the received beacon;

receiving a query;

transmitting the extracted information and the query to a server system over a network; and

receiving a web page generated by the server system using the extracted information and the query.

21. The method of claim 1, wherein switching the transceiver comprises switching the transceiver of the client device between (i) the first channel, through which a bi-directional logical connection between the client device and the first access point has been established, and (ii) the second channel, through which the second access point broadcasts beacons, wherein a bi-directional logical connection has not been established between the client device and the second access point;

wherein receiving the beacon comprises receiving the beacon over the second channel from the second access point while maintaining the bi-directional logical connection between the client device and the first access point, and without establishing a bi-directional logical connection between the client device and the second access point; and

determining the property of the client device or the second access point comprises determining the property of the client device or the second access point using the beacon received over the second channel from the second access point while maintaining the bi-directional logical connection between the client device and the first access point, and without establishing a bi-directional logical connection between the client device and the second access point.

22. The method of claim 1, wherein switching the transceiver comprises switching the transceiver of the client device between (i) the first channel, through which an IEEE 802.11 association between the client device and the first access point is currently active, the IEEE 802.11 association providing the client device bi-directional data transfer over a network through the first access point, and (ii) the second channel, through which the second access point broadcasts beacons, wherein a 802.11 association has not been established between the client device and the second access point;

wherein receiving the beacon comprises receiving the beacon over the second channel from the second access point while maintaining the IEEE 802.11 association active between the client device and the first access point, and without establishing an IEEE 802.11 association between the client device and the second access point; and

determining the property of the client device or the second access point comprises determining the property of the client device or the second access point using the beacon received over the second channel from the second access point while maintaining the IEEE 802.11 association active between the client device and the first access point, and without establishing an IEEE 802.11 association between the client device and the second access point.

23. The method of claim 1, further comprising, before receiving the beacon over the second channel from the second access point, repeatedly alternating between (i) monitoring the first channel with the transceiver of the client device, and (ii) monitoring the second channel with the transceiver, wherein the logical connection between the client device and the first access point is maintained while monitoring the first channel and monitoring the second channel.

24. The method of claim 23, further comprising, while repeatedly alternating between (i) monitoring the first channel with the transceiver of the client device, and (ii) monitoring the second channel with the transceiver, transmitting data from the client device to the first access point at an interval less than a connection timeout interval of the first access point to maintain the logical connection between the client device and the first access point.

11. A computer-readable storage device storing a computer program, the program comprising instructions that when executed by one or more computers cause the one or more computers to perform operations comprising:

switching a transceiver of a client device between (i) a first channel, through which a logical connection between the client device and a first access point is established, and (ii) a second channel, through which a second access point broadcasts beacons, wherein a logical connection is not established between the client device and the second access point;

receiving a beacon over the second channel from the second access point while maintaining the logical connection between the client device and the first access point, and without establishing a logical connection between the client device and the second access point; and

determining a property of the client device or the second access point using the beacon received over the second channel from the second access point while maintaining the logical connection between the client device and the first access point, and without establishing a logical connection between the client device and the second access point.

12. The computer-readable storage device of claim 11, wherein switching the transceiver of the client device comprises alternating, in a series of multiple consecutive time periods, between monitoring the first channel with the transceiver during one of the consecutive time periods and monitoring the second channel with the transceiver during another of the consecutive time periods.

13. The computer-readable storage device of claim 12, wherein monitoring the second channel with the transceiver comprises monitoring the second channel for time periods having a duration different from a duration of time periods in which the first channel is monitored.

14. The computer-readable storage device of claim 13, wherein monitoring the second channel comprises monitoring the second channel for time periods having a duration longer than the duration of time periods in which the first channel is monitored.

15. The computer-readable storage device of claim 14, wherein monitoring the second channel comprises monitoring the second channel for time periods having a duration at least twice the duration of time periods in which the first channel is monitored.

16. A system comprising:

one or more processors; and

a computer-readable storage device coupled to the one or more processors having instructions stored thereon which, when executed by the one or more processors, cause the one or more processors to perform operations comprising;

switching a transceiver of a client device between (i) a first channel, through which a logical connection between the client device and a first access point is established, and (ii) a second channel, through which a second access point broadcasts beacons, wherein a logical connection is not established between the client device and the second access point;

receiving a beacon over the second channel from the second access point while maintaining the logical connection between the client device and the first access point, and without establishing a logical connection between the client device and the second access point; and

determining a property of the client device or the second access point using the beacon received over the second channel from the second access point while maintaining the logical connection between the client device and the first access point, and without establishing a logical connection between the client device and the second access point.

17. The system of claim 16, wherein switching the transceiver of the client device comprises alternating, in a series of multiple consecutive time periods, between monitoring the first channel with the transceiver during one of the consecutive time periods and monitoring the second channel with the transceiver during another of the consecutive time periods.

18. The system of claim 17, wherein monitoring the second channel with the transceiver comprises monitoring the second channel for time periods having a duration different from a duration of time periods in which the first channel is monitored.

19. The system of claim 18, wherein monitoring the second channel comprises monitoring the second channel for time periods having a duration longer than the duration of time periods in which the first channel is monitored.

20. The system of claim 19, wherein monitoring the second channel comprises monitoring the second channel for time periods having a duration at least twice the duration of time periods in which the first channel is monitored.