Power-efficient data reception in a communication system with variable delay

• US 20060083168A1
• Filed: 10/20/2004
• Published: 04/20/2006
• Est. Priority Date: 10/20/2004
• Status: Active Grant

• Current Assignee: Rajat Prakash
• Original Assignee: Rajat Prakash
• Inventors: Prakash, Rajat
• Granted Patent: US 7,898,954 B2
• Time in Patent Office: Days
• US Class Current: 370/230
• CPC Class Codes: H04L 1/205 jitter monitoring
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 52/0232 according to average transmission signal activity
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

To conserve power, a terminal operates in a “power save” mode in which the terminal is in a “doze” state when there is a low probability of receiving an incoming packet and in an “awake” state when an incoming packet is expected. In the doze state, the terminal powers down as much circuitry as possible. The terminal transitions between states based on an “ON” window. The window size and placement are determined based on statistics of packet arrival times. The terminal enters the awake state at the start of the ON window, turns on the receiver, and monitors for an incoming packet. The terminal turns off the receiver after receiving the packet, updates the statistics of the arrival times, and computes the window size and placement for the next incoming packet. The terminal may selectively enable or disable the power save mode based on jitter in the arrival times.

Claims

1. A method of receiving data packets via a communication network, comprising:

determining an arrival time of each data packet in a first plurality of data packets received via the communication network;

determining a start time at which to start monitoring for a next data packet from the communication network based on arrival times of the first plurality of data packets; and

monitoring for the next data packet starting at the start time.

2. The method of claim 1, wherein the data packets are expected to be received at regular time intervals but encounter variable delay during transmission.

3. The method of claim 1, wherein the data packets are for a voice call.

4. The method of claim 1, further comprising:

powering down receiver circuitry prior to the start time.

5. The method of claim 1, further comprising:

determining a window size based on the arrival times of the first plurality of data packets, and wherein the start time is determined based on the window size and an expected arrival time for the next data packet.

6. The method of claim 1, further comprising:

determining a time offset for each data packet in the first plurality of data packets based on an arrival time of the data packet and an arrival time of a preceding data packet, the time offset for each data packet being indicative of error between actual arrival time for the data packet and expected arrival time for the data packet; and

determining a window size based on time offsets for the first plurality of data packets, and wherein the start time is determined based on the window size and an expected arrival time for the next data packet.

7. The method of claim 6, wherein the window size is determined as:

Win_size=Min_size+max(d[0],

     0)+ . . . +max(d[Num_—

pac−

1],

     0),

where

Min_size is a minimum window size;

Num_pac is number of data packets used to compute the window size;

d[x] is a time offset for data packet x;

max (a, b) gives a maximum of arguments a and b; and

Win_size is the window size.

8. The method of claim 6, wherein the start time is determined as:

T_start=T₀+T_int−

Win_size,

where

T₀ is an arrival time of a current data packet that is received most recently via the communication network;

T_int is the expected arrival time for the next data packet relative to the arrival time of the current data packet;

Win_size is the window size; and

T_start is the start time.

9. The method of claim 1, wherein the window size is determined based on statistics of the arrival times of the first plurality of data packets.

10. The method of claim 1, wherein the window size is determined based on standard deviation of time offsets for the first plurality of data packets, the time offset for each data packet being indicative of error between actual arrival time for the data packet and expected arrival time for the data packet.

11. The method of claim 1, further comprising:

determining jitter in arrival times of a second plurality of data packets received via the communication network, and wherein the monitoring for the next data packet starts at the start time if the jitter is below a threshold.

12. The method of claim 1, wherein the communication network is an IEEE 802.11 wireless network.

13. An apparatus operable to receive data packets via a communication network, comprising:

a controller operative to determine an arrival time of each data packet in a first plurality of data packets received via the communication network and to determine a start time at which to start monitoring for a next data packet from the communication network based on arrival times of the first plurality of data packets; and

a receiver unit operative to monitor for the next data packet starting at the start time.

14. The apparatus of claim 13, wherein the data packets are expected to be received at regular time intervals but encounter variable delay during transmission.

15. The apparatus of claim 13, wherein the controller is further operative to

determine a time offset for each data packet in the first plurality of data packets based on an arrival time of the data packet and an arrival time of a preceding data packet, the time offset for each data packet being indicative of error between actual arrival time for the data packet and expected arrival time for the data packet,

determine a window size based on time offsets for the first plurality of data packets, and

determine the start time based on the window size and an expected arrival time for the next data packet.

16. The apparatus of claim 13, wherein the controller is further operative to determine jitter in arrival times of a second plurality of data packets received via the communication network, and wherein the receiver unit is operative to monitor for the next data packet starting at the start time if the jitter is below a threshold.

17. A terminal comprising the apparatus of claim 13.

18. An apparatus operable to receive data packets via a communication network, comprising:

means for determining an arrival time of each data packet in a first plurality of data packets received via the communication network;

means for determining a start time at which to start monitoring for a next data packet from the communication network based on arrival times of the first plurality of data packets; and

means for monitoring for the next data packet starting at the start time.

19. The apparatus of claim 18, further comprising:

means for determining a time offset for each data packet in the first plurality of data packets based on an arrival time of the data packet and an arrival time of a preceding data packet, the time offset for each data packet being indicative of error between actual arrival time for the data packet and expected arrival time for the data packet; and

means for determining a window size based on time offsets for the first plurality of data packets, and wherein the start time is determined based on the window size and an expected arrival time for the next data packet.

20. The apparatus of claim 18, further comprising:

means for determining jitter in arrival times of a second plurality of data packets received via the communication network, and wherein the monitoring for the next data packet starts at the start time if the jitter is below a threshold.

21. A processor readable media for storing instructions operable in a wireless device to:

determine an arrival time of each data packet in a first plurality of data packets received via the communication network;

determine a start time at which to start monitoring for a next data packet from the communication network based on arrival times of the first plurality of data packets; and

initiate monitoring for the next data packet starting at the start time.

22. A method of receiving data packets via a communication network, comprising:

selecting a first mode or a second mode to monitor for a next data packet from the communication network;

if the first mode is selected, determining a start time at which to start monitoring for the next data packet based on arrival times of a first plurality of data packets received via the communication network, and monitoring for the next data packet starting at the start time; and

if the second mode is selected, monitoring for the next data packet starting from a current data packet received most recently via the communication network.

23. The method of claim 22, further comprising:

determining jitter in arrival times of a second plurality of data packets received via the communication network, and wherein the first or second mode is selected based on the jitter.

24. The method of claim 23, further comprising:

transitioning from the first mode to the second mode if the jitter exceeds a high threshold; and

transitioning from the second mode to the first mode if the jitter falls below a low threshold.

25. The method of claim 23, wherein the jitter is determined as a maximum of absolute values for time offsets for the second plurality of data packets, and wherein the time offset for each data packet is indicative of error between actual arrival time for the data packet and expected arrival time for the data packet.

26. The method of claim 23, wherein the jitter is determined based on mean square of time offsets for the second plurality of data packets, and wherein time offset for each data packet is indicative of error between actual arrival time for the data packet and expected arrival time for the data packet

27. An apparatus operable to receive data packets via a communication network, comprising:

a controller operative to select a first mode or a second mode to monitor for a next data packet from the communication network and, if the first mode is selected, determine a start time at which to start monitoring for the next data packet based on arrival times of a first plurality of data packets received via the communication network; and

a receiver unit operative to monitor for the next data packet starting at the start time, if the first mode is selected, and starting from a current data packet received most recently via the communication network, if the second mode is selected.

28. The apparatus of claim 27, wherein the controller is further operative to

determine jitter in arrival times of a second plurality of data packets received via the communication network, and wherein the first or second mode is selected based on the jitter.

29. An apparatus operable to receive data packets via a communication network, comprising:

means for selecting a first mode or a second mode to monitor for a next data packet from the communication network;

means for, if the first mode is selected, determining a start time at which to start monitoring for the next data packet based on arrival times of a first plurality of data packets received via the communication network; and

means for monitoring for the next data packet starting at the start time, if the first mode is selected, and starting from a current data packet received most recently via the communication network, if the first mode is selected.

30. The apparatus of claim 29, further comprising:

means for determining jitter in arrival times of a second plurality of data packets received via the communication network, and wherein the first or second mode is selected based on the jitter.