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An Integrated approach to developing sensor network solutions. Presented by Richie John Thomas 08/27/04. Introduction. Paper on the development work on sensor networks at Computer and Network Architecture Lab. Of the Swedish Institute of Computer Science System core

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An integrated approach to developing sensor network solutions

An Integrated approach to developing sensor network solutions

Presented by

Richie John Thomas

08/27/04


Introduction
Introduction solutions

  • Paper on the development work on sensor networks at Computer and Network Architecture Lab. Of the Swedish Institute of Computer Science

  • System core

    • ESB Sensor Hardware running the Contiki OS

    • Contiki emulation/simulation enviornment for development


  • Communication Stack solutions

    • Adaptive energy efficient MAC

    • TCP/IP layer optimized for resource constrained devices – allows system to be connected to internet system


Hardware platform
Hardware Platform solutions

  • ESB (Embedded sensor board)

    • Texas Instruments MSP 430 low power micro controller

    • RF monolithics TR 1001 single chip RF transceiver

    • Collection of sensors

      • Light- visible light

      • Passive infra red-movement

      • Temperature

      • Vibration-movement of sensor board

      • Microphone-ambient noise level

      • Infra red sender and receiver


  • MSP 430 has 60 kb flash ROM and 2kb RAM solutions

  • 32 kb EEPROM provides addl. Persistent sec. storage

  • RF transceiver operates at 868 MHz and supports rates upto 115.2 kbps

  • Board has two external Connectors

    • RS 232 port – for communication with PC

    • JTAG interface – code downloading and debugging


  • MSP 430 for low power appln. solutions

  • Provides sleep modes awakened by interrupts from internal timers or sensors

  • Supports selective rewriting of internal flash ROM

  • TR 1001 RF transceiver

    • Baseband transmission with either amplitude shift keying or on-off keying

    • Provides half duplex bit level access to physical radio medium


  • Higher level mechanisms (MAC protocol processing, data encoding, time multiplexing) should be done in s/w

  • Transceiver connected to one of MSP 430 UART-Bit shifting in h/w rather than s/w

  • UART causes interrupt only after full 8 bit received as against MICA motes where interrupt for each incoming bit


The embedded sensor board
The embedded sensor board encoding, time multiplexing) should be done in s/w


The contiki os
The Contiki OS encoding, time multiplexing) should be done in s/w

  • Flexible- allows individual programs and services to be dynamically loaded and unloaded in a running system.

  • Based on event based concurrency model

  • But also provides preemptive multithreading

  • Event based systems have lower resource requirements and well suited for sensor networks




Mac layer
MAC Layer process under different PC OS

  • Plays key role in energy efficiency and quality of service

  • MAC layer under development

    • Energy efficient TDMA-like structure overlaid on CSMA based collision avoidance protocol

    • Asynchronous – Meet requirements on size, complexity and cost and deployment in extreme environment with variable h/w stability


  • Lightweight process under different PC OS

  • No traffic overhead- foregoing synchronization

  • Scalable for multihop sensor n/w-no centralized coordination used

  • Provide good best effort QoS

  • Energy efficiency

    • Asynchronous power save protocol

    • Based on the observation if node awake for just over half of the time is awake interval will overlap with that of each of its neighbors

    • Nodes can determine available transmission window of neighbors

    • Node sleeps when no transmission


  • Flow adaptation process under different PC OS

    • Phase adjustment used to increase effective capacity of a region and reduce latency

    • Node adjust its phase to avoid sending data when there are high levels of contention or interference

    • Sequence of nodes forming a path can adjust their phase to minimize intra path interference


Tcp ip for sensor networks
TCP/IP for Sensor Networks process under different PC OS

  • This requirement for network management, calibration, diagnostics, debugging

  • Possible to connect network directly to Internet

  • Sensor data is transmitted using UDP/IP but for administrative tasks reliable unicast connections required


  • TCP/ IP used process under different PC OS

  • Individual nodes can be addressed and necessary reprogramming of sensors performed

  • Also for debugging and diagnostic tasks requiring reliable connectivity to a specific sensor

  • uIP has been developed with size of few kb and few hundred bytes of RAM – not only on ESB but variety of 8 and 16 bit processors


  • Spatial IP addressing process under different PC OS

    • Each node uses its spatial location to construct its IP address

    • The spatial IP address only denotes the location and not single identifiable node

    • If node replaced new node given same IP address as replaced node

    • Nodes aware of their spatial location neither require central server or communication between nodes for address assignment


  • Distributed TCP Caching process under different PC OS

    • Packet loss result in heavy overhead due to TCP end to end ack. and retransmission scheme

    • Poor performance in energy consumption and throughput

    • DTC cache TCP segments in network and perform local retransmissions

    • Nodes are allowed to cache only one segment

    • Nodes attempt to identify and cache segments not received by next hop


  • The segment lost i.e. for which no ack. has been received is locked in cache

  • DTC has to respond to lost packets more quickly to avoid end-to-end transmissions

  • DTC uses ordinary TCP mechanisms to detect packet loss

  • Analytical and simulation results indicate that DTC increases TCP performance

  • DTC currently being implemented in ESB nodes using Contiki simulator


Applications
Applications

  • Building security

    • Unwarranted motion in the secured building notified via GSM and security personnel logs into the building network to obtain status

    • Two functions for sensor nodes- motion detectors and backbone nodes

    • Motion detectors in rooms and backbone nodes along corridor

    • Motion detectors has direct comm. path with at least one backbone node and each backbone node had contact with one other backbone node


  • One backbone node equipped with external interface device

  • Alarm from motion detector to its backbone node and from there to its back bone node

  • Eventually all backbone nodes have info. abt. entire state of network

  • Security team with mobile backbone node to scan the information

  • Uses spatial IP addressing but mobile backbone node has fixed IP address from another n/w to differentiate it from other backbone nodes


  • Marine monitoring

    • Used to study water temp. and salinity

    • Sensors attached to a buoy takes measurements at known depths

    • These connected as fixed network as communication expensive

    • Above waterline on the buoy is a full function ESB

    • These collect data from fixed n/w below and transfer over wireless interface to gateway node

    • From here by GPRS to marine sciences center



  • HVAC Monitoring for reprogramming, debugging and monitoring

    • Explore feasibility of instrumenting a residential complex to improve the efficiency of its HVAC

    • Temperature and vibration sensors of ESB are used

    • IP based sensor accommodated into the Ethernet of the energy control room


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