Power-saving method for wireless sensor network

• US 7,447,526 B2
• Filed: 10/28/2005
• Issued: 11/04/2008
• Est. Priority Date: 10/28/2005
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd., Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: Samsung Electronics Co. Ltd., Board of Regents of the University of Texas System (University of Texas System)
• Inventors: Kim, Jung-Ho, Choi, Young-Gon, Kim, Jae-Hoon, Lee, Ji-Hoon, Arapostathis, Ari, Kim, Young-Sang
• Primary Examiner(s): Urban; Edward
• Assistant Examiner(s): CHOW, CHARLES CHIANG
• Application Number:
  US11/260,686
• Publication Number:
  US 20070099678A1
• Time in Patent Office: 1,103 Days
• Field of Search: 455/574, 455/343.1, 455/424, 455/425, 455/456.5, 455/456.6, 455/456.2, 455/67.11, 455/500, 455/343.2, 455/343.5, 455/550.1, 455/561, 455/575.1, 455/127.5, 455/343.4, 340/539.1, 340/870.01, 375/340, 375/341, 375/316, 375/285, 370/336, 370/347, 370/310, 370/476, 370/338, 370/311, 370/318, 379/58, 379/59, 379/61, 379/55.1, 379/56.1, 379370-37602, 379/433.06, 379/433.07, 379/368
• US Class Current: 455/574
• CPC Class Codes: H04W 52/028 switching on or off only a part of the equipment circuit blocks
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A power saving method of the present invention is provide for a wireless sensor network including a plurality of sensor nodes each transiting between a power saving mode and a transmit/receive mode, determines whether or not there is no transmit or receive data, enters the power saving mode if there is no transmit or receive data, and controls power consumption on the basis of signal-to-noise ratios in the power saving mode. In the power saving method of the present invention, it is possible to minimize the power consumption regardless of nodes density and without an adverse effect on the connectivity of the network, since the sojourn times of the sleep and idle states are determined adaptive to the interference level from neighboring nodes.

Claims

1. A power saving method for a wireless sensor network including a plurality of sensor nodes each managing power consumption, comprising:

detecting transition from a first state to a second state;

calculating a sojourn time of the second state on the basis of a difference between an average signal-to-interference ratio and a marginal signal-to-interference ratio;

determining whether or not the sojourn time is expired; and

transiting to the first state if the sojourn time is expired.

2. The method of claim 1, wherein the sojourn time is calculated as following formula:

$T~U<br><br>\left(1,\mathrm{\alpha <br><br>}<br><br>\frac{<br><br>S_e-\mathrm{\Delta <br><br>}<br><br><br><br>S_e<br><br>}{T_O<br><br>\mathrm{\Delta <br><br>}<br><br><br><br>S_e}\right),$

where U(·

) is a uniform random function,

$S_e;<br><br>=\frac{\mathrm{Cumulative}<br><br><br><br>\mathrm{SIR}<br><br><br><br>\mathrm{of}<br><br><br><br><br><br>a<br><br><br><br>\mathrm{node}}{T_O},$

$\mathrm{\Delta <br><br>}<br><br><br><br>S_e;<br><br>=\frac{\mathrm{Increment}<br><br><br><br>\mathrm{in}<br><br><br><br>\mathrm{SIR}<br><br><br><br>\mathrm{of}<br><br><br><br>N<br><br><br><br>\mathrm{samples}}{T_N},$

wherein S_e denotes the average signal-to-interference ratio, Δ

S_e denotes the marginal signal-to-interference ratio, T_O is the total operating time of a node, α

ε

R₊ is gain to adjust time, and T_N denotes the time duration of N samples.

3. The method of claim 1, wherein the first state is idle state for listening to the wireless medium and the second state is a sleep state for minimizing the power consumption.

4. The method of claim 3, wherein the sojourn time of the sleep state is calculated as following formula:

$T_S~U<br><br>\left(1,{\mathrm{\alpha <br><br>}}_S<br><br>\frac{<br><br>S_e-\mathrm{\Delta <br><br>}<br><br><br><br>S_e<br><br>}{T_O<br><br>\mathrm{\Delta <br><br>}<br><br><br><br>S_e}\right),$

where U(·

) is a uniform random function,

$S_e;<br><br>=\frac{\mathrm{Cumulative}<br><br><br><br>\mathrm{SIR}<br><br><br><br>\mathrm{of}<br><br><br><br>a<br><br><br><br>\mathrm{node}}{T_O},$

$\mathrm{\Delta <br><br>}<br><br><br><br>S_e;<br><br>=\frac{\mathrm{Increment}<br><br><br><br>\mathrm{in}<br><br><br><br>\mathrm{SIR}<br><br><br><br>\mathrm{of}<br><br><br><br>N<br><br><br><br>\mathrm{samples}}{T_N},$

wherein S_e denotes the average signal-to-interference ratio, Δ

S_e denotes the marginal signal-to-interference ratio, T_O is the total operating time of a node, α

_Sε

R₊ is gain to adjust time, and T_N denotes the time duration of N samples.

5. The method of claim 1, wherein the first state is a sleep state for minimizing the power consumption and the second state is an idle state for listening to the wireless medium.

6. The method of claim 5, wherein the sojourn time of the idle state is calculated as following formula:

$T_I~U\left(1,{\mathrm{\alpha <br><br>}}_I<br><br>\frac{<br><br>S_e-\mathrm{\Delta <br><br>}<br><br><br><br>S_e<br><br>}{T_O<br><br>S_e}\right),$

where U(·

) is a uniform random function,

$S_e;<br><br>=\frac{\mathrm{Cumulative}<br><br><br><br>\mathrm{SIR}<br><br><br><br>\mathrm{of}<br><br><br><br>a<br><br><br><br>\mathrm{node}}{T_O},<br><br>\mathrm{\Delta <br><br>}<br><br><br><br>S_e;<br><br>=\frac{\mathrm{Increment}<br><br><br><br>\mathrm{in}<br><br><br><br>\mathrm{SIR}<br><br><br><br>\mathrm{of}<br><br><br><br>N<br><br><br><br>\mathrm{samples}}{T_N},$

wherein S_e denotes the average signal-to-interference ratio, Δ

S_e denotes the marginal signal-to-interference ratio, T_O is the total operating time of a node, α

_Iε

R₊ is gain to adjust time, and T_N denotes the time duration of N samples.

7. A power saving method for a wireless sensor network including a plurality of sensor nodes each transiting between a power saving mode and a transmit/receive mode, comprising:

determining whether or not there is no transmit or receive data;

entering the power saving mode if there is no transmit or receive data; and

controlling power consumption on the basis of signal-to-noise ratio, wherein the power saving mode includes an idle state for listening to the wireless medium and a sleep state for minimizing power consumption,

and the step of controlling the power consumption includes;

detecting transition between the idle state and the sleep state;

determining whether or not the transition is from idle state to the sleep state;

calculating a first sojourn time of the sleep state on the basis of a difference between an average signal-to-interference ratio and a marginal signal-to-interference ratio upon transiting to the sleep state;

determining whether or not the first sojourn time is expired; and

returning to the idle state if the first sojourn time is expired.

8. The method of claim 7, wherein the step of controlling the power consumption further includes:

calculating a second sojourn time of the idle state upon transiting to the idle state;

determining whether or not the second sojourn time is expired; and

returning to the sleep state if the second sojourn time is expired.

9. The method of claim 7, wherein the first and second sojourn times are calculated as following formulas:

$T_I~U\left(1,{\mathrm{\alpha <br><br>}}_I<br><br>\frac{<br><br>S_e-\mathrm{\Delta <br><br>}<br><br><br><br>S_e<br><br>}{T_O<br><br>\mathrm{\Delta <br><br>}<br><br><br><br>S_e}\right),<br><br>T_S~U\left(1,{\mathrm{\alpha <br><br>}}_S<br><br>\frac{<br><br>S_e-\mathrm{\Delta <br><br>}<br><br><br><br>S_e<br><br>}{T_O<br><br>\mathrm{\Delta <br><br>}<br><br><br><br>S_e}\right),$

where U(·

) is a uniform random function, α

_I,α

_Sε

R₊ are gains to adjust time,

$S_e;<br><br>=\frac{\mathrm{Cumulative}<br><br><br><br>\mathrm{SIR}<br><br><br><br>\mathrm{of}<br><br><br><br>a<br><br><br><br>\mathrm{node}}{T_O},<br><br>\mathrm{\Delta <br><br>}<br><br><br><br>S_e;<br><br>=\frac{\mathrm{Increment}<br><br><br><br>\mathrm{in}<br><br><br><br>\mathrm{SIR}<br><br><br><br>\mathrm{of}<br><br><br><br>N<br><br><br><br>\mathrm{samples}}{T_N},$

wherein S_e denotes the average signal-to-interference ratio, Δ

S_e denotes the marginal signal-to-interference ratio, T_O is the total operating time of a node, and T_N denotes the time duration of N samples.