20071016 Petrioli CEOS

†Department of Computer Science – University of Rome “Sapienza” – Italy: 

†Department of Computer Science – University of Rome “Sapienza” – Italy Precision agriculture via Sensor Networks Un. Of Rome “La Sapienza” Chiara Petrioli† Security Lab, Sapienza Innovazione, Sapienza Un. of Rome CEOS-WGISS meeting Monaco, 16/10/07

Slide2: 

WSNs are wireless ad-hoc multi-hop self-organizing networks made of tiny sensor nodes cooperating to monitor the environment Wireless Sensor Networks

Slide3: 

Application of Interest: Frascati Living Lab Objective Extending the SCU functionalities by a distributed wireless system for monitoring environmental parameters (e.g. temperature, humidity, light ...) on the vineyard Tmote SKY devices by Moteiv corporation TinyOS 2.x Distributed vs centralized monitoring Minimal infrastructure Wireless communication Ad-hoc network Mesh topology Devices are battery powered energy constraints energy efficient protocols and algorithms Integration with the Special Communication Unit (SCU) acting as the sink of the WSN SCU (WLAB) Serial GIS (ESA) (Un. of Rome)

Sensor nodes platforms: 

Sensor nodes platforms ALBA, IRIS protocol stacks Implementations on TmoteSky, EYES v2.0 platforms Texas Instruments Mps430 micro-controller, 16-bit RISC CPU, 8 Mhz, 10Kb RAM, 48Kb ROM, fast wakeup (< 6us), integrated 12-bit ADC/DCA converter, expansion SPI bus. Light, temperature on board sensors. EyesIFXv2: radio chip TDA5250, 868Mhz, FSK modulation, datarate 64Kbps, on board 512Kb serial EEPROM

TmoteSky Energy model: 

TmoteSky Energy model CC2420 Modules Transceiver states Energy model

Nodes awake-asleep schedule: 

Nodes awake-asleep schedule At the end of every sleeping cycle it randomly picks a real number ta in [0,T(1-d)] (d is the duty cycle). In the following sleeping cycle the node will sleep for the first ta seconds, will then wake up for T*d seconds, and go to sleep again till the end of the sleeping cycle.

EYES IFXv2 Energy model: 

EYES IFXv2 Energy model Transceiver states Energy model

Sensor Netwoks – prototypes solutions available: 

Sensor Netwoks – prototypes solutions available What is currently available Development, optimization and implementation of two general purpose protocol stacks for sensor networks Features: Awake-asleep schedule, MAC, geographic routing, load balancing Copes with dead-ends Resilient to localization errors, adapts to network dynamics Features: Awake-asleep schedule, MAC, Hop count based routing, cost-based relay selection Integrates interest dissemination and convergecasting

Slide9: 

IRIS-Interest Dissemination Say that an estimation procedure lasts r rounds Let ki be the number of active neighbors at the i-th round which have not been counted before After r rounds the probability that the number of sampled active neighbors k1, k2, …,kr if the number of neighbors is n and the duty cycle is d is given by: n is the number of neighbors and: Neighborhood size estimation Interest Dissemination Each node receiving an interest tosses a coin with probability p it rebroadcast the interest to all its neighbors with probability (1-p) it picks c of its neighbors randomly and send the interest to them p=0.2 and c=4 is a proper parameter setting (all intended destinations reached)

Slide10: 

IRIS-Convergecasting During the interest dissemination nodes discover their distance in hops from the sink (Hop Count or HC) If a node h hops from the sink has a packet to transmit it selects a relay among awake neighbors which are h or h-1 hops from the sink Each node has associated a cost The cost can reflect residual energy, congestion level of the traversed nodes, links reliability, nodes capability to aggregate packets The way the relay is selected aims at minimizing the cost to advance of one level Relay selection criteria MAC operations CSMA like, simple, implementable on real prototypes Mechanisms to allow nodes to exploit all information available to go to sleep as much as possible

ALBA-Adaptive Load Balancing Algorithm: 

ALBA-Adaptive Load Balancing Algorithm The relay selection works in phases Selection of the best QPI Awaking nodes can participate Selection of the best GPI Performed if more than one node with the same QPI was found Nodes awaking in the middle of a GPI contention cannot participate

Rainbow: Coping with Dead-Ends: 

Rainbow: Coping with Dead-Ends

Size, cost, network lifetime: 

Size, cost, network lifetime Sensors for outdoor environments available Miniaturized sensors available Easy and inexpensive housing in plastic boxes of standard sensors possible The technology is there, costs already limited (70 euros each), can decrease to a few euros in case of massive deployment Challenge is network lifetime: if d=0.1 current prototypes last around 3-4 months with a 4 battery packs Prototypal transceivers are being deployed which reduces energy consumption to 1/5 wrt ZigBee transceivers The network could normally operate at a lower duty cycle switching on to a higher duty cycle only when there is traffic to transmit Protocols can exploit application features, saving energy (switching the transceiver ON only when needed) TmoteINVENT TmoteMINI