Adaptive power management methods and systems for wireless networks

• US 8,014,369 B2
• Filed: 12/18/2006
• Issued: 09/06/2011
• Est. Priority Date: 05/29/2006
• Status: Active Grant

• Current Assignee: Institute For Information Industry
• Original Assignee: Institute For Information Industry
• Inventors: Chou, Zi-Tsan
• Primary Examiner(s): Hu; Jinsong
• Assistant Examiner(s): Nealon; William
• Application Number:
  US11/640,196
• Publication Number:
  US 20070275748A1
• Time in Patent Office: 1,723 Days
• Field of Search: 370/311, 370/318, 370/338
• US Class Current: 370/338
• CPC Class Codes: H04W 52/265 taking into account the quality of service QoS
• CPC Class Codes: H04W 52/343 taking into account loading or congestion level

Abstract

Adaptive power management methods and systems for a first station and a second station in a wireless network. Each station operating in the power-saving (PS) mode adaptively determines a “listen interval” (LI) according to residual power state, quality-of-service requirements, or other considerations. The LI is composed of a “normal beacon interval” (NBI) followed by the combination of “beacon-window-only beacon intervals” (BBIs) and “sleep beacon intervals” (SBIs). The LI value is one or a prime number which is larger than two, and the positions of the NBI and BBIs in an LI form a cyclic difference set. Each station broadcasts a beacon frame comprising at least information about “the remaining number of BIs (RBI)” within a beacon window. Once the first station correctly receives the beacon frame from the second station, the first station predicts the awake/sleep schedule of the second station, and transmits data frames to the second station at the NBI of the second station.

Claims

1. An adaptive power management method for use in a first station and a second station in an ad hoc wireless local area network, in which the second station enters an NBI (Normal Beacon Interval) every certain number of BIs (Beacon Intervals) for power saving and data reception, where the certain number of consecutive BIs is called an LI (Listen Interval), comprising:

determining the length of LI (in units of BI) which is one or a prime number that is larger than two, wherein the BIs in the LI are denoted as 0th, 1st, 2nd, . . . , and (n−

1)th BIs, respectively, where n is the value of LI, and setting the 0th BI in the LI as the NBI, wherein the NBI comprises an AW (ATIM Window) comprising a BW (Beacon Window), where a station transmits its beacon frame within the BW, transmits and receives ATIM frames within the AW, returns an ATIM ACK (acknowledgement) to a specific station transmitting the ATIM frame and remains awake after the AW ends to wait for the reception of data frames when receiving an ATIM frame within the AW, and returns a data ACK if a data frame is received;

determining the number of BBIs (Beacon-Window-Only Beacon Intervals) and determining the positions of the NBI and BBIs in the LI to form a cyclic difference set, in which each of the BBIs comprises a BW (Beacon Window), and the second station broadcasts a beacon frame within the BW of every BBI, and enters a doze state in the BBI after the end of the BW, the beacon frame comprises a station identification and an RBI (Remaining number of BIs) representing the remaining number of BIs between the BBI and the NBI, wherein the beacon frame is transmitted in the BBI; and

the first station receiving the beacon frame from the second station in the ad hoc wireless local area network, recording the RBI corresponding to the second station, predicting the NBI of the second station according to the RBI, and transmitting a data frame to the second station at the NBI of the second station in the ad hoc wireless local area network.

2. The method of claim 1 further comprising the second station resetting the LI value according to residual power state after the LI ends.

3. The method of claim 1 further comprising the second station transmitting the beacon frame comprising the LI value to the first station.

4. The method of claim 1 further comprising:

the first station reducing the RBI corresponding to the second station in a neighbor station table by 1 if one of the BI passes; and

setting the RBI as the value of LI minus 1 if the RBI equals −

1.

5. The method of claim 1 further comprising the first station deleting data corresponding to the second station if no other beacon frame is received from the second station in a predetermined interval.

6. The method of claim 1 further comprising the second station determining the number of SBIs (Sleep Beacon Intervals), in which the second station enters a doze state in the SBIs.

7. The method of claim 6 wherein the number of the BBIs and the SBIs equals the LI value minus 1.

8. The method of claim 1 wherein the NBI comprises an AW (ATIM Window) comprising a BW (Beacon Window), and the second station transmits the beacon frame within the BW of the NBI.

9. The method of claim 8 further comprising:

the first station transmitting an ATIM frame to the second station within the AW of the NBI of the second station;

the second station transmitting an ATIM ACK to the first station in response to the ATIM frame;

the first station transmitting the data frame to the second station within the NBI after the AW ends; and

the second station transmitting a data ACK to the first station after receiving the data frame.

10. An adaptive power management system for an ad hoc wireless local area network, comprising:

a second station entering an NBI (Normal Beacon Interval) every certain number of BIs (Beacon Intervals) for power saving and data reception, where the certain number of consecutive BIs is called an LI (Listen Interval), determining the length of LI (in units of BI) which is one or a prime number that is larger than two, wherein the BIs in the LI are denoted as 0th, 1st, 2nd, . . . , and (n−

1)th BIs, respectively, where n is the value of LI, and setting the 0th BI in the LI as the NBI, wherein the NBI comprises an AW (ATIM Window) comprising a BW (Beacon Window), where a station transmits and receives beacon frames its beacon frame within the BW, transmits and receives ATIM frames within the AW, returns an ATIM ACK (acknowledgement) to a specific station transmitting the ATIM frame and remains awake after the AW ends to wait for the reception of data frames when receiving an ATIM frame within the AW, and returns a data ACK if a data frame is received;

determining the number of BBIs (Beacon-Window-Only Beacon Intervals) and determining the positions of the NBI and BBIs in the LI to form a cyclic difference set, in which each of the BBIs comprises a BW (Beacon Window), and the second station broadcasts a beacon frame within the BW of every BBI, and enters a doze state in the BBI after the end of the BW, the beacon frame comprises a station identification and an RBI (Remaining number of BIs) representing the remaining number of BIs between the BBI and the NBI, wherein the beacon frame is transmitted in the BBI; and

a first station receiving the beacon frame from the second station in the ad hoc wireless local area network, recording the RBI corresponding to the second station, predicting the NBI of the second station according to the RBI, and transmitting a data frame to the second station at the NBI of the second station in the ad hoc wireless local area network.

11. The system of claim 10 wherein the second station further resets the LI value according to residual power state after the LI ends.

12. The system of claim 10 wherein the second station further transmits the beacon frame comprising the LI value to the first station.

13. The system of claim 10 wherein first station further deletes data corresponding to the second station if no other beacon frame is received from the second station in a predetermined interval.

14. The system of claim 10 wherein the second station further determines the number of SBIs (Sleep Beacon Intervals), in which the second station enters a doze state in the SBIs.

15. The system of claim 14 wherein the number of the BBIs and the SBIs equals the LI value minus 1.

16. The system of claim 10 wherein the NBI comprises an AW (ATIM Window) comprising a BW (Beacon Window), and the second station transmits the beacon frame within the BW of the NBI.

17. The system of claim 16 wherein the first station further transmits an ATIM frame to the second station within the AW of the NBI of the second station, the second station transmits an ATIM ACK to the first station in response to the ATIM frame, the first station transmits the data frame to the second station within the NBI after the AW ends, and the second station transmits a data ACK to the first station after receiving the data frame.