Methods and apparatus for scanning radio frequency bands in wireless local area networks

• US 8,433,312 B2
• Filed: 10/23/2006
• Issued: 04/30/2013
• Est. Priority Date: 10/23/2006
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Blackberry Limited
• Inventors: Salomone, Leonardo, Montemurro, Michael Peter
• Primary Examiner(s): Nguyen, Simon
• Application Number:
  US11/552,022
• Publication Number:
  US 20080096501A1
• Time in Patent Office: 2,381 Days
• Field of Search: 455/335, 455/424, 455/425, 455/456.5, 455/456.6, 455/561, 455/550.1, 455/575.1, 455/432.1, 455/433, 455/434, 455/435.1, 455/435.3, 455/436, 455/437, 455/438, 455/440, 455/442, 455/447, 455/450, 455/453, 455/458, 455/464, 455/62, 455/63.3, 455/136, 455/140, 455/161.1, 455/161.2, 455/164.2, 455/166.2, 455/188.1, 370/347, 370/333, 370/329, 370/437, 370/331, 709/221, 709/225, 709/226
• US Class Current: 455/422.1
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 52/0219 where the power saving management affects multiple terminals
• CPC Class Codes: H04W 52/0229 where the received signal is a wanted signal
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Method and apparatus for scanning a radio frequency band in a mobile communication device without knowing regulatory information. A processor of the mobile communication device utilizes a wireless transceiver to scan the RF band using a passive scan operation on an RF channel having a passive scan status. During the passive scan operation, the processor attempts to decode an information frame on the RF channel. In response to successfully decoding an information frame, the processor changes the passive scan status of the RF channel to an active scan status, and causes an active scan operation to be performed on the RF channel having the active scan status. The scanning process may continue until the regulatory information for the RF band is received.

Claims

1. A method for use in scanning a radio frequency (RF) band for a mobile communication device which is enabled to communicate in accordance with IEEE 802.11 standards in compliance with regulatory requirements of a regulatory domain based on country information communicated in one or more IEEE 802.11 beacon frames, the method comprising:

scanning the RF band using passive scan operations on RF channels having a passive scan status, wherein a passive scan operation comprises monitoring an RF channel in attempt to decode an IEEE 802.11 beacon frame;

in response to successfully decoding, on the RF channel for the passive scan operation, an IEEE 802.11 information frame of a type that is different from an IEEE 802.11 beacon frame;

changing the passive scan status of the RF channel to an active scan status;

performing an active scan operation on the RF channel having the active scan status; and

wherein the acts of changing and performing are performed prior to receiving any country information which indicates the regulatory domain of operation.

2. The method of claim 1, further comprising:

in response to unsuccessfully decoding an IEEE 802.11 information frame on the RF channel for the passive scan operation, maintaining the passive scan status of the RF channel.

3. The method of claim 1, wherein the IEEE 802.11 information frame that is successfully decoded comprises one of an IEEE 802.11 data frame or an IEEE 802.11 control frame.

4. The method of claim 1, wherein the IEEE 802.11 information frame that is successfully decoded comprises an IEEE 802.11 information frame received from another mobile communication device.

5. The method of claim 1 wherein attempting to decode further comprises the further act of performing a decoding process with use of an error detection code.

6. The method of claim 1, wherein attempting to decode further comprises:

receiving a checksum of an information frame;

computing a checksum for the information frame; and

if the received checksum and the computed checksum match, then identifying that the IEEE 802.11 information frame of the type that is different from the IEEE 802.11 beacon frame is successfully decoded.

7. The method of claim 1, further comprising:

prior to scanning the RF band using passive scan operations on RF channels having the passive scan status, deeming the regulatory domain to be unknown in response to identifying an out-of-coverage condition for a predetermined time period.

8. The method of claim 1, further comprising:

repeating the acts of scanning and attempting to decode for one or more next RF channels of the RF band.

9. The method of claim 1, wherein the passive and active scan operations are performed in accordance with the IEEE 802.11 standards.

10. The method of claim 1, further comprising:

after changing the passive scan status on the RF channel to the active scan status;

receiving, in one or more IEEE 802.11 beacon frames, the country information; and

performing the scanning in accordance with the regulatory information.

11. The method of claim 1, which is performed by computer instructions configured for use in the mobile communication device.

12. A mobile communication device which is enabled to communicate in accordance with IEEE 802.11 standards in compliance with regulatory requirements of a regulatory domain based on country information communicated in one or more IEEE 802.11 beacon frames, the mobile communication device comprising:

one or more processors;

a radio frequency (RF) transceiver coupled to the one or more processors and configured for communications in an RF band;

a user interface which includes a display;

the one or more processors being configured to perform the following actions prior to receiving any country information which indicates the regulatory domain of operation;

cause scanning to be performed over the RF band, with use of the RF transceiver, using passive scan operations on RF channels having a passive scan status, wherein a passive scan operation comprises monitoring an RF channel in attempt to decode an IEEE 802.11 beacon frame;

for each passive scan operation on an RF channel of the RF band, attempt to decode an IEEE 802.11 information frame on the RF channel;

in response to successfully decoding, on the RF channel for the passive scan operation, an IEEE 802.11 information frame of a type that is different from an IEEE 802.11 beacon frame;

change the passive scan status of the RF channel to an active scan status; and

perform an active scan operation on the RF channel having the active scan status.

13. The mobile communication device of claim 12, wherein the one or more processors are further configured to:

in response to unsuccessfully decoding an IEEE 802.11 information frame on the RF channel for the passive scan operation, maintain the passive scan status of the RF channel.

14. The mobile communication device of claim 12, wherein the one or more processors are further configured to attempt to decode by performing a decoding process with use of an error detection code.

15. The mobile communication device of claim 12, wherein the one or more processors are further configured to attempt to decode by:

receiving a checksum of an information frame;

computing a checksum for the information frame; and

if the received checksum and the computed checksum match, identifying that the IEEE 802.11 information frame of the type that is different from the IEEE 802.11 beacon frame is successfully decoded.

16. The mobile communication device of claim 12, wherein the one or more processors are further configured to:

perform the active scan operation on the RF channel by;

causing a probe request to be transmitted on the RF channel; and

monitoring for a probe response in response to transmitting the probe request.

17. The mobile communication device of claim 12, wherein the one or more processors are further configured to:

repeat the actions of scanning and attempting to decode for one or more next RF channels of the RF band.

18. The mobile communication device of claim 12, wherein the passive and active scan operations are configured in accordance with the IEEE 802.11 standards.

19. The mobile communication device of claim 12, wherein the one or more processors are further configured to;

after changing the passive scan status on the RF channel to the active scan status;

receive, in the one or more IEEE 802.11 beacon frames, the country information; and

perform the scanning in accordance with the country information.

20. The mobile communication device of claim 12, wherein performing the active scan operation consumes less power in the mobile communication device than performing the passive scan operation.

21. The mobile communication device of claim 12, wherein the IEEE 802.11 information frame comprises one of an IEEE 802.11 data frame or an IEEE 802.11 control frame.

22. The mobile communication device of claim 12, wherein the IEEE 802.11 information frame that is successfully decoded comprises an IEEE 802.11 information frame received from another mobile communication device.