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Energy-Efficient and Reliable Medium Access in Sensor Networks

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Energy-Efficient and Reliable Medium Access in Sensor Networks Presenter: Dr. Younghwan Yoo Department of Computer Science University of Cincinnati – PowerPoint PPT presentation

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Title: Energy-Efficient and Reliable Medium Access in Sensor Networks


1
Energy-Efficient and Reliable Medium Access in
Sensor Networks
Presenter Dr. Younghwan Yoo
Department of Computer Science University of
Cincinnati ymomo_at_ececs.uc.edu
  • Authors Vivek Jain, Ratnabali Biswas and Dharma
    P. Agrawal

Department of Computer Science University of
Cincinnati jainvk, biswasr, dpa_at_ececs.uc.edu
2
Outline
  • Wireless Sensor Network
  • Reliable Sensor MAC
  • Hidden Node Problem
  • Energy Efficient Sensor MAC
  • Protocol Design
  • Performance Evaluation
  • Summary
  • Future Work

3
Wireless Sensor Network (WSN)
  • Usually a set of small immobile nodes referred as
    motes
  • Generally static topology
  • Cheap alternative to monitor inaccessible or
    inhospitable terrains
  • Applications
  • Medical Applications wireless bio-sensors
  • Nuclear and chemical plants
  • Environmental monitoring
  • Industrial Automation
  • Ocean monitoring
  • Battlefields

4
Reliable Sensor MAC
Node receives more than one packet at same time
Leads to packet loss due to buffer overflow
Wastes energy listening to idle channel
Collision
Congestion
Transmission Rate Control
Idle Listening
Good Reliable MAC
Hidden Node
Overhearing
Latency
Wastes energy receiving packets for other nodes
Control Overhead
Error Recovery
Carrier-sense, backoff, transmission,
propagation, processing, queuing
Recover packets corrupted at physical layer
Wastes energy transmitting control packets
5
Hidden Node Problem
A
B
C
D
Data
  • Hidden node problem exists between every other
    pair nodes along a route
  • RTS/CTS packets constitute large overhead
  • Transmission rate control mechanism employed

Random Backoff
Data
Random Backoff
Data
Data
Collision
6
Efficient-Efficient Sensor MAC
Energy-Efficient MAC
Adaptive Duty Cycling
Wakeup On-Demand
Overemitting Node transmits when receiver not
ready for reception
Reduces Throughput Increases Latency
7
E2RMAC - Design
  • Two radio solution
  • A Main radio for actual data transmission/receptio
    n
  • A low power pico radio to detect and transmit
    busy tones
  • CSMA/CA based
  • Skip Backoff mechanism Intermediate receiving
    node skips random backoff after successful
    reception
  • Implicit/Explicit Ack
  • Transmission rate control After receiving
    implicit Ack refrain from transmitting for
    2?communication_duration
  • Adaptive retransmission attempts

Retransmission Attempts Tx_Attempts
, where pe is packet error rate
Protocol for always-on requirement, e.g.
automotive, telematics
8
E2RMAC Basic Operation
A
B
C
D
Wakeup
Random Backoff
Filter
Processing Delay
Data
Propagation and Processing Delays
Wakeup
Backoff Skipped
Filter
Implicit Ack
Data
Wakeup
Transmission Backoff (2xCommunication_Duration
Random_Duration)
Filter
Data
Wakeup
Explicit Ack
9
E2RMAC Handling False Wakeups
Set ReceiveTimer 2xCommunication_Duration
Set ReceiveTimer 2xCommunication_Duration
X
Z
Y
A
C
B
Wakeup
Wakeup
Filter
Data
Filter
Data
Set ReceiveTimer Communication_Duration
Set ReceiveTimer Communication_Duration
10
E2RMAC Simulation Parameters
Parameter Value
Packet size 77 bytes
Filter/CTS size 19 bytes
RTS size 27 bytes
Ack size 11 bytes
Transmission rate 250 kbps
slotTime 1200 µs
TSIFS 200 µs
CWmin 1
CWmax 4
Tx_Attempts 5
Psensing PTx PRx 41 mW
Psleep 0.015 mW
PTx_on PTx_off 35 mW
TTx_on 580 µs
Pwakeup_sensing Pwakeup_Tx Pwakeup_Rx 0.015 mW
11
Performance Evaluation Linear Topology
  • All schemes are equally reliable
  • Latency of E2RMAC is higher than RMAC due to
    latency involved in transmitting filter packets
    and switching on/off the main radio
  • STEM and E2RMAC are the only energy efficient
    protocols

pe0.4
12
Performance Evaluation 8-hop Linear Topology
  • PDR of RTS-CTS based protocols is higher than
    E2RMAC as it alleviates the hidden terminal
    problem

pe0.4
13
Performance Evaluation
  • Transmission of control messages by STEM leads to
    better PDR, poor latency and more energy
    consumption
  • Due to adaptive retransmissions, E2RMAC tries to
    deliver old packets first, leading to buffer
    overflow at source nodes and thus dropping newly
    generated packet ? less PDR when pe0.4

14
Performance Evaluation
  • E2RMAC consumes less energy by avoiding control
    overhead, and false wakeup

Energy expended by the common intermediate node
Energy Expended by the route nodes
15
Performance Evaluation
  • E2RMAC and STEM protocol have comparable
    performances. We can conclude that transmission
    rate control and other optimizations successfully
    mitigates the hidden terminal problem

16
Summary E2RMAC
  • Best suited for dual radio architecture
  • Energy savings largely depends on power
    consumption of low-power pico radio
  • Minimizing energy consumption
  • Minimum control messages
  • Implicit Ack by wakeup radio
  • Timers to avoid false wakeup
  • Ensuring reliability
  • Adaptive retransmission attempts
  • Implicit/explicit Ack
  • Transmission rate control
  • Minimizing latency
  • Skip backoff mechanism
  • Minimum control overhead

17
Future Work
  • Energy Consumption Analysis for the proposed and
    existing protocols
  • To be energy-efficient than single radio solution
    (no sleep cycles), preliminary results suggests
    that pico-radio should consume less than
  • 25 of Main radio power for E2RMAC
  • 17 of Main radio power for STEM-T

? 8 improvement over STEM-T
18
Thank You!!! For further queries, please contact
the authors
19
  • Backup Slides

20
Energy Consumption Analysis
21
RMAC Design
A
B
C
D
  • CSMA/CA based
  • Intermediate receiving node skips random backoff
    after successful reception
  • Implicit Ack
  • After receiving implicit Ack refrain from
    transmitting for transmission backoff duration
    2?communication_duration

Data
Processing Delay
Propagation and Processing Delays
Backoff Skipped
Data
Implicit Ack
Transmission Backoff
Data
Random Backoff
Ack
Explicit Ack
Data
22
RMAC Performance Evaluation
  • Linear topology, Packet arrival rate 5 and 10
    pkts/sec respectively
  • Ack-based schemes have better PDR
  • MultiPath and MultiPacket schemes have constant
    latency per hop as no retransmissions are
    involved at any node

pe0.2
23
RMAC Performance Evaluation
  • Even at higher packet error rate, RMAC delivers
    more than 80 of packets
  • Also, latency per hop of RMAC is less than its
    Ack-based counterpart

pe0.4
24
RMAC Performance Evaluation
  • RMAC and CSMA-Ack schemes are compared for 6-hop
    linear topology by varying pe from 0 to 0.6
  • RMAC performs better than CSMA-Ack in all
    scenarios

25
RMAC Performance Evaluation
  • Two 6-hop routes intersecting at the center node
  • At pe0.6, RMAC uses slightly more retransmission
    attempts than CSMA-ACK but delivers more packets
    with same latency
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