METHOD FOR IMPROVING ENERGY EFFICIENCY IN WIRELESS MESH NETWORK

• US 20100157827A1
• Filed: 08/04/2009
• Published: 06/24/2010
• Est. Priority Date: 12/18/2008
• Status: Active Grant

• Current Assignee: Ajou University Industry Cooperation Foundation
• Original Assignee: Ajou University Industry Cooperation Foundation, Electronics and Telecommunications Research Institute
• Inventors: KO, Young Bae, MOON, Young Bag, LEE, Sung Hee, YOO, Seung Mok, PARK, Sang Joon
• Granted Patent: US 8,085,745 B2
• Time in Patent Office: Days
• US Class Current: 370/252
• CPC Class Codes: H04L 43/0852 Delays
• CPC Class Codes: H04W 40/10 based on available power or energy
• CPC Class Codes: H04W 40/24 Connectivity information management, e.g. connectivity discovery or connectivity update
• CPC Class Codes: H04W 40/244 using a network of reference devices, e.g. beaconing
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method for effectively using power resource in a wireless mesh network is disclosed to select and change a level of a power saving mode according to terminal and network situations to increase the duration of the network'"'"'s existence as well as improve the power consumption of each mesh terminal. After active mesh terminals that are to perform a data relay function and super-saving mesh terminals that are not to perform the data relay function are selected in consideration of a network topology at certain periods, the level of a power saving mode of the mesh terminals selected as the super-saving mesh terminals is higher than that of the mesh terminals selected as the active mesh terminals. And then, a routing path in a tree form is formed along the mesh terminals selected as the active mesh terminals to transmit data.

Claims

1. A method for using power resource in a wireless mesh network, the method comprising:

a role discriminating step of discriminating mesh terminals into active mesh terminals that are to perform a data relay function and super-saving mesh terminals that are not to perform a data relay function in consideration of a network topology;

a power saving mode setting step of setting power saving modes such that a power saving mode of the mesh terminals selected as the super-saving mesh terminals is higher than that of the mesh terminals selected as the active mesh terminals;

a routing path generating step of generating a routing path in a tree form along the mesh terminals selected as the active mesh terminals; and

a data transmission step of transferring data along the generated routing path while the mesh terminals are in an active state,

wherein the respective steps are repeatedly performed at every certain period.

2. The method of claim 1, wherein the super-saving mesh terminals are selected such that they are positioned at a single hop distance from one or more active mesh terminals.

3. The method of claim 1, wherein, while the super-saving mesh terminals are in an active state, a maximum backoff time duration of the mesh terminals selected as the active mesh terminals is set to be longer than that of the mesh terminals selected as the super-saving mesh terminals to give priority of accessing radio resources to the super-saving mesh terminals.

4. The method of claim 1, wherein the role discriminating step comprises:

periodically transmitting, by each mesh terminal, its single hop neighbor information and a metric value for selection of an active mesh terminal to a root terminal;

constructing, by the root terminal, network topology information based on information received from each mesh terminal;

selecting, by the root terminal, an active mesh terminal based on the constructed network topology information; and

providing, by the root terminal, active mesh terminal selection information to every mesh terminal.

5. The method of claim 4, wherein the metric value is defined by the sum of the amount of residual power resource of each mesh terminal, a ratio of the terminals participating as the active mesh terminals, and link average quality with neighboring terminals.

6. The method of claim 5, wherein the metric value is calculated by equation shown below:

7. The method of claim 4, wherein the selecting of the active mesh terminals comprises:

defining a set S_A of terminals selected as active mesh terminals, a set S_C of mesh terminals connected to the root terminal by the active mesh terminals, and a set S_D of terminals which are not yet connected to the root terminal;

including the root terminal in the set S_A and moving every single hop neighboring terminal of the root terminal from the set S_D to the set S_C;

selecting a terminal having one or more neighboring terminals included in the set S_D and having the highest metric value, as an active mesh terminal from the terminals included in the set S_C; and

moving the terminal selected as the active mesh terminal to the set S_A and moving all the single hop neighboring terminals of the terminal selected as the active mesh terminal from the set S_D to the set S_C;

repeatedly performing selecting the active mesh terminal until such time as the set S_D becomes a null set; and

when the set S_D becomes a null set, selecting an additional active mesh terminal from the terminals included in the set S_C to distribute a routing path.

8. The method of claim 4, wherein, in providing by the root terminal the active mesh terminal selection information to every mesh terminal, the active mesh terminal selection information is included in a route announcement packet and transmitted to every mesh terminal.

9. The method of claim 1, further comprising:

a power saving mode changing step of changing, by each mesh terminal, its level of the power saving mode according to the amount of generated data while data is being transferred along the generated routing path.

10. The method of claim 9, wherein the power saving mode changing step comprises:

measuring, by the mesh terminal, a queuing delay time of a data packet;

calculating an exponentially weighted moving average (EMA) based on the measured queuing delay time;

comparing the calculated EMA with one or more pre-set threshold values; and

changing the power saving mode of the mesh terminal to a higher or lower level according to the comparison result.

11. The method of claim 10, wherein the queuing delay time is a time difference between a point when the data packet comes in a packet queue of the mesh terminal and a point when the data packet comes out of the packet queue but is not yet transmitted to a different mesh terminal.

12. The method of claim 10, wherein the EMA value is calculated by equation shown below:

EMA_cur=EMA_prev+α

S(QsDelay_cur−

EMA_prev)

wherein EMA_prev is a previously calculated EMA, QsDelay_cur is a queuing delay time of a current packet, and ‘

α

’

is a parameter for determining how many pieces of the latest data are to be reflected (