Methods and apparatus to manage power consumption in wireless local area network devices

• US 8,045,576 B2
• Filed: 10/14/2008
• Issued: 10/25/2011
• Est. Priority Date: 10/14/2008
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Tsfaty, Yossi, Baum, Avraham, Zaks, Artur
• Primary Examiner(s): Mui; Gary
• Assistant Examiner(s): Samuel; Dewanda
• Application Number:
  US12/251,079
• Publication Number:
  US 20100091657A1
• Time in Patent Office: 1,106 Days
• Field of Search: 370/241, 370/338, 370/350, 370/329, 370/311, 370/341, 370/346, 370/330, 370/458
• US Class Current: 370/458
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 52/0248 dependent on the time of the day, e.g. according to expected transmission activity
• CPC Class Codes: H04W 52/0296 switching to a backup power supply
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Methods and apparatus to manage power consumption in wireless devices are disclosed. A disclosed example apparatus comprises performing a first received signal strength indicator (RSSI) scan to determine a beacon interval and a first beacon time for a wireless channel, calculating a second beacon time for the wireless channel based on the beacon interval and the first beacon time, and performing a second RSSI scan for the wireless channel during a time interval that includes the calculated second beacon time. In some examples, the wireless channel is a wireless channel that was previously identified as active, is a wireless channel that previously had the highest received power level, and/or is selected from a list of popular or frequently used channels. Additionally or alternatively, when a wireless channel with sufficient signal level is identified, scanning for additional channels is not performed.

Claims

1. A method comprising:

performing a first received signal strength indicator (RSSI) scan to determine a beacon interval and a first beacon time for a wireless channel;

calculating a second beacon time for the wireless channel based on the beacon interval and the first beacon time; and

performing a second RSSI scan for the wireless channel during a time interval that includes the calculated second beacon time.

2. A method as defined in claim 1, further comprising determining a length of the time interval to accommodate a clock rate difference between a first clock associated with a wireless receiver module and a second clock associated with an access point associated with the wireless channel.

3. A method as defined in claim 1, further comprising determining a length of the time interval to accommodate an error in the calculation of the second beacon time.

4. A method as defined in claim 1, wherein a length of the time interval is less than about 4 milliseconds.

5. A method as defined in claim 1, wherein calculating the second beacon time comprises:

determining a number of beacon intervals since the first beacon time;

multiplying the number of beacon intervals and the beacon interval to form an elapsed time estimate;

computing the second beacon time based on the elapsed time estimate.

6. A method as defined in claim 5, wherein computing the second beacon time comprises computing a sum of the elapsed time estimate and the first beacon time.

7. A method as defined in claim 5, further comprising using a local clock to estimate the number of beacon intervals since the first beacon time.

8. A method as defined in claim 1, disabling a packet demodulator of the wireless receiver module while performing the second RSSI scan.

9. A method as defined in claim 1, further comprising re-enabling a wireless receiver module to perform a third RSSI scan to determine a third beacon time for the wireless receiver.

10. A method as defined in claim 1, wherein the second RSSI scan is performed assuming the same access point is associated with the wireless channel during the first and second time intervals.

11. A method as defined in claim 1, further comprising determining a length of the time interval based on a power consumption of a wireless receiver module.

12. An apparatus comprising:

a wireless receiver to perform received signal strength indicator (RSSI) scans;

a receiver controller to enable the wireless receiver during a first time interval to perform a first RSSI scan for a wireless channel to determine a beacon interval and a first beacon time for the wireless channel, and to enable the wireless receiver during a second time interval that includes a calculated second beacon time to perform a second RSSI scan for the wireless channel to determine an RSSI value associated with the wireless channel; and

a beacon time calculator to calculate the second beacon time based on the first beacon time and the beacon interval.

13. An apparatus as defined in claim 12, further comprising a demodulator controller to enable a demodulator of the wireless receiver during the first time interval and not enable the demodulator during the second time interval.

14. An apparatus as defined in claim 12, wherein the beacon time calculator is to determine a length of the second time interval to accommodate a clock rate difference between a first clock associated with a wireless receiver module and a second clock associated with an access point associated with the wireless channel.

15. An apparatus as defined in claim 12, wherein the wireless receiver is to determine the RSSI value without determining whether the same access point is associated with the wireless channel during the first and second time intervals.

16. An apparatus as defined in claim 12, wherein the wireless receiver is implemented in accordance with a standard from the Institute of Electrical and Electronics Engineer (IEEE) 802.1 1x family of standards.

17. An article of manufacture storing machine accessible instructions which, when executed, cause a machine to:

perform a first received signal strength indicator (RSSI) scan to determine a beacon interval and a first beacon time for a wireless channel;

calculate a second beacon time for the wireless channel based on the beacon interval and the first beacon time; and

perform a second RSSI scan for the wireless channel during a time interval that includes the calculated second beacon time.

18. An article of manufacture as defined in claim 17, wherein the machine accessible instructions, when executed, cause the machine to determine a length of the time interval to accommodate a clock rate difference between a first clock associated with a wireless receiver module and a second clock associated with an access point associated with the wireless channel.

19. An article of manufacture as defined in claim 17, wherein the machine accessible instructions, when executed, cause the machine to calculate the second beacon time by:

determining a number of beacon intervals since the first beacon time;

multiplying the number of beacon intervals and the beacon interval to form an elapsed time estimate;

computing the second beacon time based on the elapsed time estimate.

20. An article of manufacture as defined in claim 17, wherein the machine accessible instructions, when executed, cause the machine to disable a packet demodulator of a wireless receiver module while performing the second RSSI scan.