Efficient Energy Management Protocol for Target Tracking Sensor Networks

X. Du, F. LinDepartment of Computer Science

North Dakota State UniversityFargo, ND 58105

USA

9th IFIP/IEEE International Symposium on Integrated Network Management9th IFIP/IEEE International Symposium on Integrated Network Management (IM), 2005(IM), 2005

Chien-Ku Lai

Outline

Introduction Network Model The Sensor Network Energy Management

Protocol The Routing Protocol Performance Evaluation Conclusions

Introduction- Wireless Sensor Networks

Many low-power, low-cost small sensors distributed over a vast field

to obtain fine-grained, high-precision sensing data typically powered by batteries usually scattered densely and statically

Introduction- Wireless Sensor Networks (cont.)

A source A sensor node detecting a target and generating

data to report the conditions of the target

A sink An end user or a base station that collects data fr

om the sources

Introduction (cont.)

Most existing researches focus on issues in Network layer Media access control layer Physical layer

Application layer protocols for sensor networks remain a largely unexplored region

Network Model

Network Model

Cella: side lengtha = rr = sensing range

R: transmission rangeR/r 2≧

Network Model- Assumptions

1. Sensor nodes are static, and each sensor node is aware of its own location

SNEM protocol does not require very accurate node locations

2. For most cells, there is at least one sensor node in each cell

The Sensor Network Energy Management Protoc

ol (SNEM)

1. About target tracking

2. Concepts

3. Details

4. Power balance

The Sensor Network Energy Management Protocol (SNEM)

Where is the energy spent The main task of a sensor node is to

detect events perform quick local data processing transmit the data

Power consumption domains Sensing Communication Data processing

SNEM mainly considers how to save energy in communication domain

The Sensor Network Energy Management Protocol (cont.)

Node idle listening consumes 50–100% of the energy required for receiving Stemm and Katz

idle:receive:send ratios are 1:1.05:1.4 The Digitan 2 Mbps Wireless LAN module

idle:receive:send ratios is 1:2:2.5

The idea of SNEM let nodes that do not perform sensing task go to sl

eep

SNEM- About target tracking

Tracking is an important and widely-used application for wireless sensor networks Military

to detect and track enemy troops and tanks Civilian life

to track the movement of wild animals

SNEM- About target tracking (cont.)

In target tracking applications the interesting events happen infrequently with lo

ng intervals of inactivity

Most sensor nodes can go to sleep during the inactivity period only a small number of nodes stay alert to detect t

he presence of the target

SNEM

SNEM is particularly designed for target tracking sensor networks

The scheme lets most sensors go to sleep while only the sens

ors near the moving target keep active saves energy for sensor nodes

while at the same time keeps tracking the moving target and sends the target information to the sink

SNEM (cont.)

The network operations have two stages The watching stage

no target is present in the field The tracking stage

sensor nodes track the moving target

SNEM- Concepts

Moving target

Relay cellTN: Target Neighbor cell

TN

TN

SNEM- Details

Each sensor node stores two state variables Cell status

indicating the status of the cell Active time

the time to keep the node active

Relay Point (RP) the active node in a relay cell

SNEM- Details (cont.)

Sleeping nodes periodically awake after every ta second depends on

the size of the cell – a the maximum speed of the target - vt

a/vt

SNEM- Details (cont.)

When the status of a cell changes from relay to TN the RP will periodically broadcast a cell status upd

ate message to all nodes in the cell for every tb seconds

When a sleeping node awake it will keep active for tb seconds

The broadcast will repeat for times

SNEM- Details (cont.)

When the cell status becomes to relay nodes will broadcast a Relay Point (RP) message

to other nodes in the same cell with a delay

The remaining energy

Random back off time

SNEM- Details (cont.)

If the target moves very fast the Target Neighbor cells include the cells two ste

p (or even several steps)

Then the sensor sleep time ta can be set as 2a/vt

SNEM- Power balance

When the current RP (say A) uses about 1/3 of its energy A will include its remaining energy and a retiring

indication in a broadcast message when another node B is awake and finds out it

has more remaining energy than A, it will send a take-over message to A

The Routing Protocol

The Routing Protocol

Several routing protocols have been developed for sensor networks Directed Diffusion Leach Mesh

Do not work well with SNEM only one node in each relay cell is active

The Routing Protocol (cont.)

A routing protocol is needed jointly considers the node sleeping scheme in the

application layer and data dissemination in network layer

The Routing Protocol (cont.)

Routing cells cells are in the direction from source to

destination

The Routing Protocol (cont.)

A: source

B: destination

The Routing Protocol (cont.)

Contention-based mechanism with RTS/CTS is used in MAC layer

Nodes in TN send a CTS packet with a delay

Performance Evaluation

1. Performance under Different Node Density2. Different Source-Sink Distances3. The Delay Performance4. Resilience to Sensor Node Failures5. Tracking Performance

Performance Evaluation- Parameters

Simulator : QualNet The underlying MAC : 802.11 DCF Sinks : 4 Sensor Nodes : 900 Deployment : Random Area : 300m x 300m Simulation time : 600s Transmission range : 40m Sensing range : 20m Cells : 15 x 15 = 225 The probability of node failure : 0.1

Performance under Different Node Density- Delivery Ratio

Performance under Different Node Density- Energy Consumption

Different Source-Sink Distances

- Delivery Ratio

Different Source-Sink Distances

- Energy Consumption

The Delay Performance

- Average delay

Resilience to Sensor Node Failures- Delivery ratio

Resilience to Sensor Node Failures - Energy consumption

Tracking Performance- Target tracking quality

Conclusions

Conclusions

Sensor Network Energy Management protocol (SNEM) is a novel energy management protocol for target tracking

sensor networks exploits the features of target tracking applications and

sensor networks allows sensor nodes that are far away from targets go to

sleep save lots of energy while guarantee the accurate tracking

and timely delivery Cell Relay routing protocol

integrates very well with SNEM

Conclusions (cont.)

SNEM scheme performs much better than another energy saving scheme – PEAS a popular routing protocol – Directed Diffusion

SNEM saves significant amount of energy achieves high quality tracking and high delivery ra

tio

Question?

Thank you.Thank you.