An Energy-Efficient and Low-Latency Routing Protocol for Wireless Sensor Networks

Antonio G. Ruzzelli, Richard Tynan and G.M.P. O’HareAdaptive Information Cluster, Smart Media Institute

Department of Computer ScienceUniversity College Dublin

Proceedings of the 2005 Systems Communications (ICW’05)Proceedings of the 2005 Systems Communications (ICW’05)

Chien-Ku Lai

Outline

Introduction Related Work Scheduling in Merlin Experimentation and Results Conclusions and Future Work

Introduction- Wireless Sensor Networks (WSNs)

Components:One or more base-stationsMany sensor nodes

Constraints on sensor nodes:EnergyStorage capacitiesData processing

Introduction- Wireless Sensor Networks (WSNs) (cont.)

Applications: Ecosystem monitoring Emergency operation Intelligence detection of ambient conditions Intrusion detection Localization of objects or animals Medical monitoring Structural monitoring Surveillance

Introduction- Wireless Sensor Networks (WSNs) (cont.)

Major form of energy wastage: Idle listeningCollisionTransmissions overheadOverhearing

Introduction- about this paper

MERLIN is presentedMac Energy efficient, Routing and Localizatio

n INtegratedCombination of TDMA and CSMA

Related Work

SMACTMAC DMAC

SMAC

Uses a coordinated adaptive sleeping mechanism

The main drawbacks:Latency

RTS/CTS mechanism

The increase of energy consumption when some nodes join the network

TMAC

An improvement to the SMAC protocol Uses an overhearing mechanism RTS/CTS collisions are very high Latency is still present

DMAC

Incorporates a data gathering tree to reduce the latency

The main drawback: It is suitable only for unidirectional

communication flow to a single gateway

Scheduling in Merlin

Scheduling in Merlin

The purpose of MERLIN scheduling is to allocate time-zone slots

Nodes in the same time-zone use the same slot to transmit

The timing of the slots prevents most collisions

Scheduling in Merlin

V-table

X-table

Scheduling in Merlin- V-scheduling

1 2 3 4 5 6 7 8 9

Gateway

Scheduling in Merlin- X-scheduling

1 2 3 4 5 6 7 8 9

Gateway

Experimentation and Results

1. Network setup time2. Network lifetime3. Latency of messages

Simulation environment

OmNet++ EYES WSNs testbed Number slot /frame = 4 DataRate = 115200 bits/sec Contention period = 30ms DataSize = 16+8 Bytes (data + 3 bytes pre

amble + starting code)

Simulation environment (cont.)

Nodes with the same colors are in the same zone (same hop count number)

Network setup time

Network lifetime

Latency of messages (1/4)

X-scheduling

V-scheduling

Latency of messages (2/4)

X-scheduling

V-scheduling

Latency of messages (3/4)

X-scheduling

V-scheduling

Latency of messages (4/4)

X-scheduling

V-scheduling

Latency of messages- Comparison

Conclusions and Future Work

Conclusions

The absence of handshake mechanisms like RTS/CTS can considerably reduce the latency of messages

Idle listening is reduced by the TDMA approach

CSMA technique increases the scalability

Conclusions (cont.)

X scheduling is suitable for applications in which latency is

a tighter constraint V-scheduling

performs better than the X-scheduling in terms of percentage of collisions and network lifetime

Future Work

Perform more experimentation to compare MERLIN scheduling with other WSN protocols

Clarify the impact of our design decisions with mobile nodes

Questions?

Thank you.Thank you.