An Energy-Aware Medium-Access-Control Protocol with Frequent

Sleeps for Wireless Sensor Networks

Christopher K. Nguyen And Anup Kumar

Mobile Information Networks & Distributed Systems LabDepartment of Computer Engineering & Computer Science

University of Louisville

IEEE Symposium on Computers and Communications (ISCC 2005)

Speaker: Yung-Ling Yu

Outline

• Introduction

• TEA-MAC protocol design– Simplified version of 802.11 MAC frames– Radio modes and sensor states– The complete TEA-MAC scheme

• Evaluations and simulation results

• Conclusion

Introduction

• WSN require that the energy consumption in sensors should be as low as possible

• Saving energy always compromises the utilization and performance of WSN

• The Throughput and Energy-Aware MAC(TEA-MAC) focuses on – High throughput utilization of WSN– Ensuring low consumption of energy

Introduction

• The proposed protocol has two main contributions– Wake up as soon as a communication is requested

• Because just-in-time wake-ups reduce latency

– Sleep as soon as it becomes idle• Because instant sleeps reduce consumption of energy

TEA-MAC protocol design

• The proposed scheme alleviate– Idle listening– Control-packet overhead– Overhearing

• Using two main issues– Frequent sleeps

• Minimize idle listening

• Reduce overhearing

– Short sleeps• Maximize the throughput by reducing latency

Simplified version of 802.11 MAC frames

• For WSN, the prevalent communication is broadcast

• The overhead problem grows significant when the broadcast data propagate

• The shaded regions create unnecessary overhead – Every node is the recipient of the transmission

Simplified version of 802.11 MAC frames

• From inspection of the 802.11 data frame– The wastage percentage is

• (4*6)/(2+2+6+6+6+2+6+2312+4) = 1.02 %

• From inspection of

the 802.11 control frame– The wastage percentage is

1.for RTS

(2*6)/(2+2+6+6+4) = 60%

2.for CTS or ACK

6 / (2+2+6+4) = 42.86%

Radio modes and sensor states

• Three radio modes– Sleep– Receive– Transmit

Radio modes and sensor states

• Two sensor states– Sleep– Awake

The complete TEA-MAC scheme

The complete TEA-MAC scheme

The complete TEA-MAC scheme

Evaluations and simulation results

• Simulator– SENSE(Sensor Network Simulation and Emulator)

• 500 sensor nodes• Communication types

– Broadcast, multicast, and unicast mixed– Broadcast and unicast intervals were set at 5s and 1

0s, respectively

• The power– Transmission 1.6W– Reception 1.2W– Idle listen 1.15W

Evaluations and simulation results

Evaluations and simulation results

Conclusion

• TEA-MAC is a practical approach for two reasons– First, sensors are inexpensive

• It is not cost-ineffective to deploy sensors in great numbers

– Second, Technological advances provide sensors with much longer life

• The problem of energy consumption will eventually be less significant