Power saving function for wireless LANs: methods, system and program products
View Patent ↗A wireless data communication system has a first station or mobile unit is linked to a second station configured as an access unit to support packet communication, voice or data, where the voice packets are transmitted in the Continuously Aware Mode (CAM) mode while other packets are buffered by the access point and held until asked for by the first station when in a Power Saving-Poll (PSP) mode. A monitoring apparatus at the access point monitors all transmitted packets and sorts the packets to the mobile unit according to CAM or PSP mode. Voice packets are sent out immediately to the mobile unit. Other packets are stored at the access point. The packet arrival rate may vary during transmission and due to random packet delays introduced by propagation characteristic and processing apparatus. The packet arrival rate and delays are taken into account by the first station in an algorithm to determine and extend the normal safe period in which the station receiver may be powered off.
1. A wireless data communication system, comprising:
a first station including a transmitter and acting as an access point for supporting packet communication, wherein the first station is operable sort packets into continuous packets and power saving packets, and the transmitter is operable to transmit the continuous packets at predetermined intervals and buffer the power saving packets; and
a second station including a receiver for receiving data from the first station, the second station being operable to measure arrival times of the continuous packets and determine a safe period for removing power from the receiver between continuous packets based on the continuous packet arrival times, wherein the second station is further operable to send a poll signal to the first station to trigger the transmitter to transmit the buffered power saving packets.
2. The system of claim 1 , wherein the second station is operable to measure jitter associated with the continuous packet arrival times and determine the safe period based on the continuous packet arrival times and the measured jitter.
3. The system of claim 1 , wherein the second station is operable to place the receiver into a sleep mode and awaken the receiver based on the safe period to receive packets from the first station.
4. The system of claim 1 , wherein the second station is configured to operate in one of an enabled power saving state, a disabled power saving state, and a troubled power saving state.
5. The system of claim 4 , wherein the second station is operable to compare a packet arrival interval from a current packet to an expected packet arrival interval and determine the power saving state based on the comparison.
6. The system of claim 5 , wherein the second station is operable to designate a current interval as a good interval responsive to the difference between the current packet arrival interval and the expected packet arrival interval being less than a predetermined threshold and transition from the disabled power saving state to the troubled power saving state responsive to identifying a predetermined number of good intervals.
7. The system of claim 6 , wherein the second station is operable to reduce the safe period for removing power from the receiver responsive to operating in the troubled power saving state.
8. The system of claim 5 , wherein the second station is operable to transition from the enabled power saving state to the disabled power saving state responsive to the difference between the current packet arrival interval and the expected packet arrival interval exceeding a predetermined threshold.
9. The system of claim 1 , wherein the second station is operable to determine the safe period by subtracting a standard deviation of a predetermined number of previous packet arrival intervals from an expected packet arrival interval.
10. The system of claim 9 , wherein the second station is operable to incorporate a radio stabilization time into the safe period.
11. The system of claim 1 , wherein the continuous packets include voice packets.
12. A method for wireless data communication, comprising:
receiving continuous packets at a mobile unit from an access point at predetermined intervals;
measuring arrival times of the continuous packets;
determining a safe period for removing power from a receiver of the mobile unit between continuous packets based on the continuous packet arrival times; and
polling the access point to trigger transmission of buffered power saving packets.
13. The method of claim 12 , further comprising:
measuring jitter associated with the continuous packet arrival times; and
determining the safe period based on the continuous packet arrival times and the measured jitter.
14. The method of claim 12 , further comprising:
placing the receiver into a sleep mode; and
awakening the receiver from the sleep mode based upon the safe period to receive the continuous packets.
15. The method of claim 12 , further comprising operating the mobile unit in one of an enabled power saving state, a disabled power saving state, and a troubled power saving state.
16. The method of claim 15 , further comprising:
comparing a packet arrival interval from a current packet to an expected packet arrival interval; and
determining the power saving state based on the comparison.
17. The method of claim 16 , further comprising:
designating a current interval as a good interval responsive to the difference between the current packet arrival interval and the expected packet arrival interval being less than a predetermined threshold; and
transitioning from the disabled power saving state to the troubled power saving state responsive to identifying a predetermined number of good intervals.
18. The method of claim 17 , further comprising reducing the safe period for removing power from the receiver responsive to operating in the troubled power saving state.
19. The method of claim 16 , further comprising transitioning from the enabled power saving state to the disabled power saving state responsive to the difference between the current packet arrival interval and the expected packet arrival interval exceeding a predetermined threshold.
20. The method of claim 12 , wherein determining the safe period further comprises subtracting a standard deviation of a predetermined number of previous packet arrival intervals from an expected packet arrival interval.
21. The method of claim 20 , wherein determining the safe period further comprises incorporating a radio stabilization time into the safe period.
22. The method of claim 12 , wherein the continuous packets include voice packets.
23. A program storage device, encoded with instructions that, when executed by a computer system, perform a method for wireless data communication, comprising:
receiving continuous packets at a mobile unit from an access point at predetermined intervals;
measuring arrival times of the continuous packets;
determining a safe period for removing power from a receiver of the mobile unit between continuous packets based on the continuous packet arrival times; and
polling the access point to trigger transmission of buffered power saving packets.