Power saving function for wireless LANS: methods, system and program products

• US 20030086443A1
• Filed: 11/07/2001
• Published: 05/08/2003
• Est. Priority Date: 11/07/2001
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Beach, Robert
• Granted Patent: US 7,126,945 B2
• Time in Patent Office: Days
• US Class Current: 370/516
• CPC Class Codes: H04L 47/24 Traffic characterised by specific attributes, e.g. priority or QoS
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

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.

Claims

1. A wireless data communications system having extended power off capability comprising:

(a) a first station linked to a second station which serves as an access point (AP) to support packet communication, voice or data;

(b) monitoring apparatus at the access point (AP) which sorts packets according to a Continuously Aware Mode (CAM) or Power Saving Model (PSM) mode; and

(c) measuring apparatus at the first station which receives the CAM packets and measures CAM packet arrival time for determining a safe period for turning off the receiver between CAM packets based upon an expected arrival time of the CAM packets.

2. The system of claim 1 further comprising:

(d) transmitting apparatus which transmits immediately CAM packets to the first station while non-voice packets are buffered by the access point (AP) and held until requested by the first station when in a Power Saving Poll (PSP) mode.

3. The system of claim 1 wherein the measuring apparatus further comprises:

(e) “

jitter”

measuring apparatus which measure “

jitter”

associated with packet arrival intervals.

4. The system of claim 1 further comprising:

(f) “

sleep’

apparatus responsive to the measuring apparatus which awakens the first station for receiving packets based upon the safe period.

5. The system of claim 1 wherein the access point and the first mobile unit operate under the IEEE 802.11 standard.

6. The system of claim 1 further comprising:

(g) first station comparing apparatus which compares the ith actual packet arrival time [A (i)] to expected packet arrival time (P).

7. The system of claim 6 further comprising:

(h) first station determining apparatus which determines the state of the PSP mode as “

0”

or disable or “

1”

, enabled but in trouble, or “

2”

, enabled.

8. The system of claim 7 further comprising:

(i) first station processing apparatus which operates when AI (i) does not approach P and waits for the next packet if the PSP state is 0 or waits for the next packet if the PSP mode is “

1”

with no good packet intervals and reduces the “

Power Off”

time by a slight amount when the PSP mode is 2 or enabled.

9. The system of claim 8 further comprising:

(j) first station measuring apparatus which determines an extended “

Power Off”

time between packets as [P−

Standard Deviation of Consecutive Packet Arrival Time AI (i, i+1, i+2) Receiver Stabilizing Time after “

Power On”

] when in the “

0”

mode and AI (i) approaches P or if the PSP mode is “

1”

or “

2“

waiting for the arrival of the next packet whereupon the “

Power Off”

mode is extended beyond normal “

Power Off”

time due to the periodic nature of the voice traffic.

10. A method for extended “

Power Off”

period for a wireless communication system comprising;

(a) waiting for packet arrival at a mobile unit in the wireless communication system;

(b) comparing actual packet time {AI(i)] versus P or expected packet arrival time;

(c) determining the status of a PSP mode as “

0”

or enabled;

“

1”

or in trouble, or “

2”

enable;

(d) returning to Step b, if AI (i) does not approach P and the PSP mode is 0 or 1, and reducing the Power Off time, if the PSP mode is 2;

(e) determining the PSP mode if AI (I) approximates P;

(f) returning to Step a, if the PSP mode is 1 or 2; and

(g) calculating an extended Power Off time.

11. The method of claim 10 further comprising the step of:

(i) reducing the “

Power Off”

time by a slight amount when the PSP mode is 2 or enabled when AI (i) does not approach P and waits for the next packet if the PSP state is 0 or waits for the next packet if the PSP mode is “

1”

with no good packet intervals.

12. The method of claim 111 further comprising the step of:

(h) waiting for the arrival of the next packet AI (i) which approaches P or if the PSP mode is “

1”

or “

2”

.

13. The method of claim 12 wherein the actual packet arrival time [AI (i)]=Current Arrival Time (CT)−

Last Packet Arrival Time (LT) and LT=CT.

14. The method of claim 13 wherein the extended Power Off Time is [P−

Standard Deviation (AI (i), AI (i−

1), AI (i−

2)−

Receiver Start Up Time (RSU)] when the PSP is 0, whereby an extended Power Off time is achieved by the periodic nature of the packet arriva time.

15. A medium, executable in a computer system, for extended “

Power Off”

period for a wireless communication system comprising;

(a) program instruction for waiting for packet arrival at a mobile unit in the wireless communication system;

(b) program instruction for comparing actual packet time {AI(i)] versus P or expected packet arrival time;

(c) program instruction for determining the status of a PSP mode as “

0”

or enabled;

“

1”

or in trouble, or “

2”

enable;

(d) program instruction for returning to Step b, if AI (i) does not approach P and the PSP mode is 0 or 1, and reducing the Power Off time, if the PSP mode is 2;

(e) program instruction for determining the PSP mode if AI (I) approximates P;

(f) program instruction for returning to Step a, if the PSP mode is 1 or 2; and

(g) program instruction for calculating an extended Power Off time.

16. The medium of claim 15 further comprising the step of:

(h) program instruction for reducing the “

Power Off”

time by a slight amount when the PSP mode is 2 or enabled when AI (i) does not approach P and waits for the next packet if the PSP state is 0 or waits for the next packet if the PSP mode is “

1”

with no good packet intervals.

17. The medium of claim 16 further comprising the step of:

(i) program instruction for waiting for the arrival of the next packet AI (i) which approaches P or if the PSP mode is “

1”

or “

2”

18. The medium of claim 17 wherein the actual packet arrival time [AI (i)]=Current Arrival Time (CT)−

Last Packet Arrival Time (LT) and LT=CT.

19. The medium of claim 18 wherein the extended Power Off Time is [P—

Standard Deviation (AI (i), AI (i−

1), AI (i−

2)−

Receiver Start Up Time (RSU)] when the PSP is 0, whereby an extended Power Off time is achieved by the periodic nature of the packet arrival time.