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

• US 7,898,954 B2
• Filed: 10/20/2004
• Issued: 03/01/2011
• Est. Priority Date: 10/20/2004
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Prakash, Rajat
• Primary Examiner(s): Pham; Chi H
• Assistant Examiner(s): Faroul; Farah
• Application Number:
  US10/969,155
• Publication Number:
  US 20060083168A1
• Time in Patent Office: 2,323 Days
• Field of Search: 370/230, 370/237, 370/238, 370/252, 455/355
• US Class Current: 370/235
• 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:

powering down a receiver circuitry prior to a window start time;

determining an arrival time for a first data packet received, from a plurality of data packets received, via the communication network;

determining the time difference, if any, between the first data packet arrival time and a second received data packet arrival time;

determining a variable window size for a window of time during which the receiver circuitry is to be powered-on based on the time difference between the first and second data packet arrival times, wherein the window of time begins at the window start time, wherein the variable window size varies in order to accommodate arrival time jitter; and

powering on the receiver circuitry for the duration of the window of time according to the window 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:

determining a time offset based on the time difference between the first and second data packet arrival times and an expected time interval between the packets.

5. The method of claim 4, wherein the variable window size is determined as:

Win_size=Min_size+max(d[0],0)+ . . . +max(d[Num_—

pac−

1],0),

where

Mm 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 variable window size.

6. The method of claim 4, wherein the window 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 variable window size; and

T_start is the window start time.

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

8. The method of claim 1, wherein the variable window size is determined based on standard deviation of the time difference between the first and second data packet arrival times.

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

10. An apparatus configured to receive data packets via a communication network, comprising:

a controller configured to power down a receiver circuitry prior to a window start time, to determine an arrival time for a first data packet received, from a plurality of data packets received, via the communication network, configured to determine the time difference, if any, between the first data packet arrival time and a second received data packet arrival time, configured to determine a variable window size for a window of time during which the receiver circuitry is to be powered-on based on the time difference between the first and second data packet arrival times, wherein the window of time begins at the window start time, wherein the variable window size varies in order to accommodate arrival time jitter, and configured to

power on the receiver circuitry for the duration of the window of time according to the window start time.

11. The apparatus of claim 10, wherein the data packets are expected to be received at regular time intervals but encounter variable delay during transmission.

12. The apparatus of claim 10, wherein the controller is further configured to

determine a time offset based on the time difference between the first and second data packet arrival times and an expected time interval between the packets;

and

wherein the window start time is determined as;

T_start=T₀=T_int−

Win_size,

where

T_o 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 variable window size; and

T_start is the window start time.

13. A terminal for receiving data packets via a communication network, comprising:

a controller configured to power down a receiver circuitry prior to a window start time, configured to determine an arrival time for a first data packet received, from a plurality of data packets received, via the communication network, configured to determine the time difference, if any, between the first data packet arrival time and a second received data packet arrival time, configured to determine a variable window size for a window of time during which the receiver circuitry is to be powered-on based on the time difference between the first and second data packet arrival times, wherein the window of time begins at the window start time, wherein the variable window size varies in order to accommodate arrival time jitter, and configured to power on the receiver circuitry for the duration of the window of time according to the window start time.

14. An apparatus configured to receive data packets via a communication network, comprising:

means for powering down a receiver circuitry prior to a window start time;

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

means for determining the time difference, if any, between the first data packet arrival time and a second received data packet arrival time;

means for determining a variable window size for a window of time during which the receiver circuitry is to be powered-on based on the time difference between the first and second data packet arrival times, wherein the window of time begins at the window start time, wherein the variable window size varies in order to accommodate arrival time jitter; and

means for powering on the receiver circuitry for the duration of the window of time according to the window start time.

15. The apparatus of claim 14, further comprising:

means for determining a time offset based on the time difference between the first and second data packet arrival times and an expected time interval between the packets,

wherein the window 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 variable window size; and

T_start is the window start time.

16. An integrated circuit, comprising:

circuitry configured to;

power down a receiver circuitry prior to a start time;

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

determine jitter in arrival times of a second plurality of data packets received via the communication network;

determine a variable window size for a window of time during which the receiver circuitry is to be powered-on based on the jitter, wherein the window of time begins at the start time, wherein the variable window size varies in order to accommodate arrival time jitter; and

initiate powering on the receiver circuitry for the duration of the window of time according to the start time in order to monitor for the next data packet starting at the start time, wherein the monitoring for the next data packet starts at the start time if the jitter is below a threshold.

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

determining jitter in arrival times of a first and second plurality of data packets received via the communication network;

selecting a power save mode or an always on mode to monitor for a next data packet from the communication network with receiver circuitry, wherein the mode is selected based on the jitter;

if the power save mode is selected, determining a start time at which to start monitoring for the next data packet with the receiver circuitry based on the arrival times of the first and second data packets received via the communication network, and monitoring for the next data packet starting at the start time, wherein the start time is equal to an arrival time of a current data packet that is received most recently via the communication network plus the expected arrival time for the next data packet relative to the arrival time of the current data packet minus a variable window size for a window of time during which the receiver circuitry is to be powered-on; and

if the always on mode is selected, monitoring for the next data packet with the receiver circuitry starting from a current data packet received most recently via the communication network.

18. The method of claim 17, further comprising:

transitioning from the power save mode to the always on mode if the jitter exceeds a high threshold; and

transitioning from the always on mode to the power save mode if the jitter falls below a low threshold.

19. The method of claim 17, 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.

20. The method of claim 17, 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.

21. An apparatus configured to receive data packets via a communication network, comprising:

a controller configured to determine jitter in arrival times of a second plurality of data packets received via the communication network, configured to select a power save mode or a always on mode to monitor for a next data packet from the communication network, wherein the power save mode or the always on mode is selected based on the jitter, and, if the power save mode is selected, configured to 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, wherein the start time is equal to an arrival time of a current data packet that is received most recently via the communication network plus the expected arrival time for the next data packet relative to the arrival time of the current data packet minus a variable window size for a window of time during which a receiver unit is to be powered-on; and

the receiver unit configured to monitor for the next data packet starting at the start time, if the power save mode is selected, and starting from a current data packet received most recently via the communication network, if the always on mode is selected.

22. An apparatus configured to receive data packets via a communication network, comprising:

means for determining jitter in arrival times of a second plurality of data packets received via the communication network;

means for selecting a power save mode or a always on mode to monitor for a next data packet from the communication network, wherein the power save or always on mode is selected based on the jitter;

means for, if the power save 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, wherein the start time is equal to an arrival time of a current data packet that is received most recently via the communication network plus the expected arrival time for the next data packet relative to the arrival time of the current data packet minus a variable window size for a window of time during which receiver circuitry is to be powered-on; and

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

23. A computer-readable medium, comprising storage memory having software instructions stored thereon, the software being executable by a processor, the software instructions, comprising:

instructions for causing a processor to power down a receiver circuitry prior to a window start time;

instructions for causing a processor to determine an arrival time of each data packet in a first plurality of data packets received via the communication network;

instructions for causing a processor 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;

instructions for causing a processor to determine jitter in arrival times of a second plurality of data packets received via the communication network; and

instructions for causing a processor to monitor for the next data packet starting at the start time, wherein the monitoring for the next data packet starts at the start time if the jitter is below a threshold;

determining an arrival time for a first data packet received, from a plurality of data packets received, via the communication network;

determining the time difference, if any, between the first data packet arrival time and a second received data packet arrival time;

determining a variable window size for a window of time during which the receiver circuitry is to be powered-on based on the time difference between the first and second data packet arrival times, wherein the window of time begins at the window start time, wherein the variable window size varies in order to accommodate arrival time jitter; and

powering on the receiver circuitry for the duration of the window of time according to the window start time.

24. A computer-readable medium, comprising storage memory having software instructions stored thereon, the software being executable by a processor, the software instructions, comprising:

instructions for causing a processor to determine jitter in arrival times of a second plurality of data packets received via the communication network;

instructions for causing a processor to select a power save mode or an always on mode to monitor for a next data packet from the communication network, wherein the power save or always on mode is selected based on the jitter;

if the power save mode is selected, instructions for causing a processor to 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, wherein the start time is equal to an arrival time of a current data packet that is received most recently via the communication network plus the expected arrival time for the next data packet relative to the arrival time of the current data packet minus a variable window size for a window of time during which receiver circuitry is to be powered-on; and

if the always on mode is selected, instructions for causing a processor to monitor for the next data packet starting from a current data packet received most recently via the communication network.