2-hop Scheme for Data Collection in Wireless Sensor Networks · Data collection is one of the important tasks in a WSN • Data collection is usually performed in Data Gathering Cycle

2-hop Scheme for

Data Collection in

Wireless Sensor Networks ◎VUONG An Hong

TAN Yasuo

LIM Azman Osman

School of Information Science

Japan Advanced Institute of Science and Technology (JAIST)

IPSJ SIG Mobile Computing and Ubiquitous Communications (MBL)

Okinawa, Japan

21 - 22 May 2012

Presentation Outline

1. Introduction

2. Research Motivation

3. Research Problem: Energy Consumption Imbalance

4. Related Work

5. Research Objective

6. Proposed Scheme: 2-hop Scheme

7. Analysis and Evaluation of Proposed Scheme

7.1 Chain Networks

7.2 Binary Tree Networks

7.3 Random Networks

8. Concluding Remarks

26 July 2012 VUONG An Hong 2/20

1. Introduction

Data collection is one of the important tasks in a WSN

• Data collection is usually performed in Data Gathering Cycle (DGC) in which all

sensors wake up, generate one packet and send to the sink

• Wireless sensor network (WSN)

consists of many sensors and one sink

• Applications

• Environmental (habitat

monitoring, fire detection)

• Health (monitoring patients’

physiological data)

• All sensors use radio signal to send

their sensed data to the sink

• Process of sending the sensed data to

the sink is called data collection


2. Research Motivation

• In practical, sensors in such network use small batteries and are expected to

operate for a long time

• Replacing or recharging the batteries of the sensors is impractical after they have

been deployed

Prolonging the network lifetime is an important consideration while

designing or deploying a WSN


Sink

Level 1

Level 2

Level L

…

Imbalance energy consumption

throughout the network

Problem

Sensors at level 1 & level 2 consumes

plenty of energy so their batteries drain

very fast

Packet Packet

Packet Packet

Packet Packet

Definition: the time until one sensor

runs out of battery

Network lifetime becomes short

Causes

3. Research Problem


4. Related Work

Routing

• Li et al. selected

minimum-energy routing

paths for transmitting

packet

Network lifetime

improvement

Energy balancing

• Zhang et al. exploited

the energy tradeoff

between direct

transmission and hop-to-

hop transmission to

balance energy

consumption of all

sensors in the network

• Our research

Sleep mode

• Ma et al. proposed

contiguous link scheduling

sleep-management

scheme to turn off radio

circuit to avoid idle

listening


5. Research Objective

• Increasing the network lifetime of WSN by balancing the energy

consumption of each sensor throughout the network


Si receives packets

from Si+1 and forwards

all to Si-1

SL-1 SL S1 Sink SL-1 SL S1 Sink

𝒑L

𝟏 − 𝒑L

Si forwards a packet to Si-1 with

probability pi or sends it directly

to the sink with probability 1 – pi

H2H scheme

(Conventional scheme)

Direct scheme

(Zhang et al.)

2-hop scheme

(Proposed scheme)

SL-1 SL S1

𝒑L SL-2

Sink

𝟏 − 𝒑L

Si forwards a packet to Si-1 with

probability pi or sends it to Si-2

with probability 1 – pi

Disadvantage

Direct scheme requires plenty of

energy

• If sensors too far from the

sink, direct scheme may be

impossible

We propose

Advantage over Direct scheme

2-hop transmission requires less

energy than Direct transmission

6. Proposed Scheme


7. Analysis and Evaluation

Chain Network Binary Tree Network Random Network

• Optimal transmission probability values of 𝑝𝑖 for each

sensor

• Theoretical calculation how much network lifetime is

increased with 2-hop scheme compared to that with

H2H scheme

• Numerical simulation on

how much network

lifetime could be

increased with 2-hop

scheme


7.1 Chain Network


Optimal values of 𝒑𝒊 • We found optimal transmission probability

values, 𝑝𝑖 for a chain network of

• 8 sensors

• 9 sensors

• 10 sensors

• 11 sensors

Level Li

Tra

nsm

issio

n p

robabili

ty

8-sensor WSN

9-sensor WSN

11-sensor WSN

10-sensor WSN

• Number of data packets transmitted by

sensors far from the sink are smaller

than those near the sink

• In order to balance energy

consumption, sensors far from the sink

tend to send a packet in 2-hop

transmission


7.1 Chain Network

How much network lifetime is increased?

Level Li

Tra

nsm

issio

n p

rob

ab

ility

Assigning

optimal

probabilities

for the

sensors

Energy consumption of each level of

sensor in one DGC


sensor in one DGC

Level Li

Energ

y C

onsum

ption (

mJ)

Level Li

Energ

y C

onsum

ption (

mJ)

S5 S7 S8 S1 S6

Sink

H2H scheme 2-hop scheme

S5 S7 S8 S1

𝒑8

S6 Sink

𝒑7 𝒑6 𝒑5 𝒑1 …

2-hop scheme

hop-to-hop scheme

Level Li

Energ

y C

onsum

ption (

mJ)


sensor in one DGC

For optimal probabilities, the

expected energy consumption

of all sensors is balanced



At initial, assuming the initial battery level

for all sensors is 30J, the total number of

DGCs until one sensor dies:

• H2H scheme: 996 (=30𝐽

30.1𝑚𝐽)

• 2-hop scheme: 1010 (=30𝐽

29.7𝑚𝐽)

Network lifetime can be increased about

1.41% (=1010

996)

7.1 Chain Network

Tra

nsm

issio

n p

rob

ab

ility

2-hop scheme

H2H scheme

Level Li

En

erg

y C

on

su

mp

tio

n (

mJ)


sensor in one DGC In one DGC

• H2H scheme: sensor at level 1

consumes more energy than the others

(30.1mJ)

• 2-hop scheme: with optimal 𝑝𝑖, energy

consumption of all sensors are balanced

(29.7mJ)




7.2 Binary Tree Network

• Sensors in same level i are

completely identical; therefore, we

can assume that all sensors in the

same level have same value of 𝑝𝑖

• Energy consumption is already

balanced for all sensors in the

same level

We find optimal values of 𝑝𝑖 to

balance energy consumption of

sensors in different levels

Binary tree network analysis

Sink

Level 1

Level 2

Level L



Binary tree network with 6 levels of

sensors

• Energy consumption could be

balanced for the first 4 levels

(assigning p5 = p6 = 0.9)



(assigning p4 = p5 = p6 = 0.9)



(assigning p3 = p4 = p5 = p6 = 0.9)

Optimal values of 𝒑𝒊

Level Li

Energ

y C

onsum

ption (

mJ)

H2H scheme

p3 = p4 = p5 = p6 = 0.9

p5 = p6 = 0.9

p4 = p5 = p6 = 0.9

Minimum expected energy consumption

→ Maximum expected network lifetime


sensor in one DGC




At initial, assuming the initial battery

level for all sensors is 30J, the total

number of DGCs until one sensor

dies:

• H2H scheme: 126 (=30𝐽

240𝑚𝐽)

• 2-hop scheme: 142 (=30𝐽

210𝑚𝐽)

Network lifetime can be increased

about 12.7% (=142

126)

In one DGC

• H2H scheme: sensor at level 1

consumes more energy than others

(about 240 mJ)

• 2-hop scheme: maximum energy

consumption (about 210 mJ)


Level Li

Energ

y C

onsum

ption (

mJ)

H2H scheme

p5 = p6 = 0.9


sensor in one DGC




Simulation scenario


7.3 Random Network

Network coverage is 100 m × 100 m

• We examine the

performance of 2-hop

scheme and H2H

scheme

• We construct a network

simulator using C++

programming

• In this WSN, the

hardware specification

is assumed as

IEEE802.15.4

• Tree topology is built

using tree-based routing

(TBR) protocol


Simulation parameters and settings


7.3 Random Network

Network configuration

Number of sensors 100

Position of sensor Randomly distributed

Number of sinks 1

Position of sink In the middle of the network coverage

Sensor configuration

Initial battery level 30 J

H2H transmission range 20 m

2-hop transmission range 30 m

Energy to receive one packet 0.0512 mJ

Energy to transmit one packet in H2H transmission 3.7147 mJ

Energy to transmit one packet in 2-hop transmission 15.1945 mJ

Transmission probability of each sensor Pre-assigned before deployment

General configuration

Data gathering cycle 10 s

Number of simulation topologies 20


7.3 Random Network

2-hop scheme

Transmission Probability of each sensor

Avera

ge N

etw

ork

Lifetim

e (

s)

H2H scheme

Simulation result

Average network lifetime

can be increased by

16.8% @ p = 0.76 with

2-hop scheme compared

to the H2H scheme



• We proposed the 2-hop scheme to increase network lifetime in this research

• 2-hop scheme can operate in large-scale networks where direct scheme cannot be

well-deployed

• Evaluation results

• Chain network with 8 sensors, theoretical results show that 2-hop scheme

increases network lifetime at most 1.41%

• Binary tree network of 6 levels, theoretical results show that network lifetime can

be increased by 12.7%

• In random network, using a computer simulation the average network lifetime

can be increased up to 16.8% when the optimal transmission probability is 0.76

• Future works

• Short-term: we will examine the performance of 2-hop scheme in terms of

latency

• Long-term: we will further evaluate the network lifetime performance of 2-hop

scheme when the initial battery level of each sensor is different

8. Concluding Remarks


Thank you for your attention!

VUONG An Hong

[email protected]


Documents

2-hop Scheme for Data Collection in Wireless Sensor Networks · Data collection is one of the important tasks in a WSN • Data collection is usually performed in Data Gathering Cycle