UPTEC F11 030
Examensarbete 30 hp
2011
Error Control in Wireless Sensor
Networks
A Process Control Perspective
Oskar Eriksson
Teknisk- naturvetenskaplig fakultet
UTH-enheten
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Ångströmlaboratoriet
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Abstract
Error Control in Wireless Sensor Networks: A Process
Control Perspective
Oskar Eriksson
The use of wireless technology in the process industry is becoming increasingly
important to obtain fast deployment at low cost. However, poor channel quality often
leads to retransmissions, which are governed by Automatic Repeat Request (ARQ)
schemes. While ARQ is a simple and useful tool to alleviate packet errors, it has
considerable disadvantages: retransmissions lead to an increase in energy expenditure
and latency. The use of Forward Error Correction (FEC) however offers several
advantages. We consider a Hybrid-ARQ-Adaptive-FEC scheme (HAF) based on BCH
codes and Channel State Information. This scheme is evaluated on AWGN and fading
channels. It is shown that HAF offers significantly improved performance both in
terms of energy efficiency and latency, as compared to ARQ.
Sponsor: ABB, Corporate Research
ISSN: 1401-5757, UPTEC F11 030
Examinator: Tomas Nyberg
Ämnesgranskare: Anders Ahlén
Handledare: Erik Björnemo, Mikael Gidlund (ABB, Corporate Research)
Contents
1
Introduction ..................................................................................................................................... 1
1.1
Background .............................................................................................................................. 1
1.2
Problem Description ................................................................................................................ 1
1.3
Related Work ........................................................................................................................... 2
2
Theoretical Considerations .............................................................................................................. 2
2.1
WirelessHART .......................................................................................................................... 2
2.2
Error Control ............................................................................................................................ 4
2.2.1
Automatic Repeat Request (ARQ) ................................................................................... 4
2.2.2
Forward Error Correction (FEC) ....................................................................................... 4
2.2.3
Hybrid Automatic Repeat Request (HARQ) ..................................................................... 6
2.2.4
Error Control in WSNs ..................................................................................................... 6
2.3
Path Loss .................................................................................................................................. 7
2.4
Error Probability ...................................................................................................................... 7
2.4.1
Bit Error Probability ......................................................................................................... 7
2.4.2
Packet Error Probability ................................................................................................... 8
2.4.3
Code Word Error Probability ........................................................................................... 8
3
System model .................................................................................................................................. 9
3.1
Network Model ....................................................................................................................... 9
3.2
Path Loss Model .................................................................................................................... 10
3.3
Hybrid-ARQ-Adaptive-FEC scheme ........................................................................................ 10
4
Numerical Analysis ........................................................................................................................ 10
4.1
Latency Analysis .................................................................................................................... 11
4.2
Energy Consumption Analysis ............................................................................................... 12
5
Numerical Evaluation .................................................................................................................... 14
5.1
Energy Consumption ............................................................................................................. 15
5.2
Latency .................................................................................................................................. 18
5.3
Constraint on Latency ............................................................................................................ 20
5.4
Fading Channels..................................................................................................................... 22
6
Discussion and Conclusions ........................................................................................................... 25
Bibliography ........................................................................................................................................... 26
