adopting the erika operating system to run real-time application in wsn real-time systems laboratory...

Adopting the ERIKA Operating System to run Real-Time Application in WSN

Real-Time Systems Laboratory

RETIS Lab

A. Romano G.Lipari P.Pagano M.Chitnis

Resaerch Area: RTOS

Motivations

There is an increasing interest in Wireless Sensor Networks in fields like industry, medicine, automotive and military.

Typical applications are:

• Surveillance• Medicine and health care• Vehicle traffic monitoring and control• Vibrational monitoring of building

2/11© 2007 Scuola Superiore Sant’Anna

Problems

For WSN Applications demanding real time constraints, it is essential to have a Real-Time Operating System which :

• provides Real-Time guarantees• supports WSN services

The most popular WSN Operating system is TinyOS that is well-known and widely-used.

Main features of tinyOS:

• FCFS Task scheduling• Event triggered• Component based

TinyOS is not suitable for Real-Time Multi-tasking applications 3/11

© 2007 Scuola Superiore Sant’Anna

Main Idea

The basic idea consists of adopting ERIKA Operating System and a network stack protocol for a wsn node.

• Porting of ERIKA to AVR ATmega128 hardware platform• Interfacing ATMEL IEEE 802.15.4 Stack protocol with RT

Kernel

Hardware Abstraction Layer

MCU Layer Board Layer

Kernel Layer

Application Layer

CPU Layer


Experimental setup (I)

The WSN node is composed by:– AVR ATmega128 microcontroller (8-bit CPU)– AT86RF230 transceiver

A star topology has been created:• 4 DEVICE nodes

– Make the association with the coordinator node– Send packets with CBR to the coordinator according to the

IEEE 802.15.4 standard• 1 COORDINATOR node

– Initializes the network– Associates all the devices requesting for association– Receive all packets arriving from the devices– Send all packets arrived through USB to the PC that collects

datas


Experimental setup (II)

AVR Atmel ATmega128

expansion board Atmel STK501

development board Atmel STK500

Atmel AT86RF230 Transceiver


Coordinator

Device 1

Device 2

Device 3

Device 4

Experimental setup (III)


Main results

In the coordinator node a task has been inserted with a variable execution length in order to simulate variable load.

In this way it’s possible to simulate the delay introduced by such node while receiving.

The delay has been simulated in two different scenario:• ERIKA with scheduling policy like tinyOS (all tasks

have the same priority)• ERIKA with a Fixed Priority scheduling policyIn the last scenario we have experimented a strong

decrease of delay confirming the results obtained by RTNS in a similar simulated scenario.


Experimental results


Conclusion and Outlook

The Porting of ERIKA for the hardware platform has been completed.

In ERIKA, an interface has been created to manage the services provided by the IEEE 802.15.4 network stack protocol.

Work in progress:

Add primitives related to the Internetworking OSI layer to provide other important services like routing.

Differentiate the HAL to transmit data frames using different radio transceivers.


Scuola Superiore Sant’Anna, CNR research area, Via Moruzzi 1, 56124 Pisa, Italy

E-mail: [email protected]

adopting the erika operating system to run real-time application in wsn real-time systems laboratory...

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