A Biologically-Inspired Approach to Designing

Wireless Sensor Networks

Matthew Britton, Venus Shum, Lionel Sacks and Hamed Haddadi

The University College London, London ,UK

EWSN’04

OUTLINE

• Introduction• System Requirements• KOS• Hardware Environment• Performance Analysis• Conclusion

INTRODRCTION

• Biological Automata have a number of desirable characteristics such as：• scalability • robustness• simplicity • self-organization

• There are significant advantages in treating some classes of sensor networks as Biological automata–like system

INTRODRCTION (cont.)

• Biological Automata• Self-organise and self-op

timise• System adapt to dynami

c environments• Neighbor to neighbor int

eraction• Iterative–like process• Change slow to spread t

hrough the network

agent

INTRODRCTION(cont.)

• Application to sensor network• To limit communication to short range

• Avoid the centralize algorithm (power mangement)

• Scalability• For environmental monitoring the size of the spatial field

of interest will not be unknown in design phase

• Simplicity of mangement• Self-organising and self-optimised (robust)

• Dynamic environment and requirment• In environmental monitoring various temporal phases of

operation

INTRODRCTION(cont.)

• Iterative application• Quality of their result• Operation become simple and predictable

• For relatively high-latency requirement system

INTRODRCTION(cont.)

• Goal-• Decentralised management• Self-organisation and autonomy• Robustness to topological change• Limited processing power of individual nodes• Power control for individual nodes• Adaptation to dynamic environments and changing

roles

System Requirements

• Coordination (distributed algorithm)• Nodes within the same area interact and

understand the phenomenon• Representative node coordinate other nodes

action (save energy )•“Horizontal” Layers of network function upon a network of nodes

•“Vertical” tasks within one of these node

System Requirements(cont.)

• Data transport protocol• Gossip-protocol

• Like Flooding protocol

• Periodically exchange state to neighbor

A B

DBEF

GDE

Select a peer

Exchange viewCFG

C

System Requirements(cont.)

• Power management• Cluster, avoid multihop radio communication

• High integrity operation• System can adapt to failures, corrupted data or im

precision’s in parameters and still function sufficiently (Fault tolerance)

KOS Features

• Modularity of application design• Simple execution model

• single-tasking ,run to completion model

• Highly communication oriented (messaging interface)

• Power awareness• Adaptive scheduling

• Simple processing load control• Adjust the execution periods of iterative app

KOS Structure

• The kOS is divided into objects and methods.• Task execution is performed by specifying objects, m

ethods and execution times

Main routine

Object

Object

Method

Method

Method

Library routine#1

Library routine#2

KOS Structure (cont.)•The KOS functional abstraction

KOS Operation

• Task scheduling• Sleep/activity/sleep cycle • Schedule object manage transitions

• Messaging handling• SAD (SECOAS APP Message Protocol)• SAM (SECOAS Data Message Protocol)

• Robustness of operation

Task scheduling

Sleep

High priority scheduler

Low priority scheduler

High priority ISR

Low priority ISR

High priority interrupt

High priority interrupt

Low priority interrupt

Return to low priority ISR

Boot

Kos reset command

WDT time-outstart

Task scheduling Concept(cont.)

Sleep

Hardware RF Sensor UART

Ready Queue

High priority scheduler

ISRLow priority scheduler

ISR

Task

Run Preemption

Timer

run to completion

SchedulerTaskTask

Task scheduling(cont.)

• The biological automaton characteristic of iteration to design application

• Scheduler can control the period of its execution.• Reduce power consumption when the node’s battery

power is low.• KOS use an off-line analysis to gauge the duty cycle of each

object’s iteration

Message handling

• The message object is scheduled periodically after radio and sensor interface message are received

• SAM is used by objects for intra- and inter-node communication (between application)

• SAD is used between application and sensor module• Using message-handling services and gossip

protocol disseminate information around network (policies or application parameters)

Message handling(cont.)

A

B

C

D

Gossip protocol

Periodically exchange state to neighbor

Message handling(cont.)

Radio Receive Buffer

Sensor TransmitBuffer

Radio Transmit Buffer

Sensor ReceiveBuffer

Radio module

ApplicationsSensor Module

SAM SAM

SAMSAM

SAM

SAD

SAD

SAD

SAD

•Data flow intra-node between application, radio module and sensor module

Robustness of operation

• Reboot itself in an attempt to bypass any intermittent problems• WDT

• Application will operate given unknown radio connectivity conditions• If information is unavailable for short periods of

time, this simply halts the iterative process for that time period

• Application will load-controlled by the scheduler• Change periodicity of these application

Hardware Environment

• MCU:• PIC18F452(8-bit 4MHz)

• 32K FLASH

• 1.5KRAM

• 200 bytes EEPROM• Sensor module• Radio module• LCD display

Performance Analysis

• Power usage

Performance Analysis(cont.)

• CPU duty cycle•4MHz operates at 1 million instructions per second

Performance Analysis(cont.)

• Memory usage

Conclusion

• Treat wireless sensor networks like biological automata

• Beneficial features ： scalability , robustness, self-organisation

• Support distributed Application