ICC 2007, 27th JuneDavid Tacconi

Supporting the Sink Mobility: a case study for WSN

D.Tacconi, I.Carreras, D.Miorandi, I.Chlamtac,

CREATE-NET research centre, Trento, Italy

http://forum.toronews.net/viewtopic.php?t=240511&postdays=0&postorder=asc&start=0

F.Chiti, R.Fantacci

DET department, University of Florence

ICC 2007, 27th JuneDavid Tacconi

Overview

Traditional application of WSNsWhy WSN with a Mobile Sink?Examples and ApplicationsProposed Scenario and System ArchitectureSimulation ResultsFuture Work and Conclusions

ICC 2007, 27th JuneDavid Tacconi

WSN: Traditional Monitoring Physical phenomenon to be monitored:

Microclimate monitoring Red tree forest monitoring:

Unique forests of sequoia and red trees Very specific climate: 70% of H2O cycle much

upper than ground level Humidity monitoring

Fixed Sink, remote connection for data collection and analysis

ICC 2007, 27th JuneDavid Tacconi

Mobile Sensors and Data Mules Implementations

Animals habits monitoring Tree fogs, Switzerland Zebra, Kenya Migration and behavior Wild horses, USA Migration and

behavior

Fixed collection points, mobile nodes acting as data mules

ICC 2007, 27th JuneDavid Tacconi

WSN with a Mobile SinkWSN can be queried by car passing byIntelligent Transportation System:

Application enhanced by WSN disposed along the road, running on handheld or GPS devices

ICC 2007, 27th JuneDavid Tacconi

Ice Detection on mountain roads Sensor nodes inserted

in the road to sense: Temperature

Humidity

Multihop communication among nodes on and along the road

Car computer system can in advance alert the driver of an incoming iced part of the road

Very simple application, increased safety for drivers

ICC 2007, 27th JuneDavid Tacconi

Parking lot searching

Free Parking!

ICC 2007, 27th JuneDavid Tacconi

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System Architecture Sensor Nodes (SN)

Sensing a quantity as temperature or parking lot status (free/occupied)

Wireless capabilities Position aware (through GPS, distributed

localization, position stored) Vice Sink nodes (VS)

Nodes disposed along the road No battery limitation Not connected among them in principle

Mobile Sink (MS) A car passing by on the road Connected with one VS at the time GPS enabled

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Pos=(Lat, Long)

+Pos=(Lat, Long)

ICC 2007, 27th JuneDavid Tacconi

Geographic Query Forwarding MS injects a query packet to the closest VS:

Containing MS mobility information, i.e. position, speed and direction (derived by GPS)

Indicating the target region with centre coordinates and the maximum radius of interest

Query forwarding: The VS starts a Greedy geographic routing toward target

region, by selecting the closest SN to the destination The previous step is performed by each SN Once the target region is reached, localized flooding strategy

performed by node closer to target region centre The node closest to the centre, prepares Reply packet toward

expected MS position

ICC 2007, 27th JuneDavid Tacconi

Adaptive Geographic Forwarding Reply forwarding

Same greedy geographic routing toward the MS expected position

The position is adapted step by step according to original MS mobility information

Once a VS is reached the replay packet is:Delivered to MS, if it is in radio rangeStored for a given amount of time, waiting for the MS to

pass byForwarded toward the next VS, following MS mobility if

it has not passed by

ICC 2007, 27th JuneDavid Tacconi

MS and Geographic Routing Is there a parking lot on

that part of the town?Free/Occupied

ICC 2007, 27th JuneDavid Tacconi

Simulation area: 1000x600 m²

1 Mobile Sink (MS) moving with random speed among Vmin and Vmax: Vmin = [10÷20] m/s Vmax = [20÷35] m/s

Nvs Vice Sinks (VSs) are equally spaced and always disconnected among them: Nvs = [2÷20]

NxM Sensor Nodes (SNs) are disposed along a grid and connected to 4 neighbors, with communication radius R=25m: N = 40 M = [1÷25]

Simulation set up (Omnet++)

ICC 2007, 27th JuneDavid Tacconi

Results 1/2 Latency of packets vs. Number of Sensors (N=40, M= [1÷25]), Nvs=10,

Packet Delivery Ratio (PDR)>90%

ICC 2007, 27th JuneDavid Tacconi

Results 2/2 Latency of packets vs. Number of Vice Sinks (Nvs=[2÷20]), N=40, M= 25,

Packet Delivery Ratio (PDR)>90%

ICC 2007, 27th JuneDavid Tacconi

Results evaluation Latency remains tolerable while increasing mobility and

number of SNs: Proposed adaptive geographic routing is scalable Latency is mainly due to the number of hops for packet

delivering Increasing mobility results in a smaller Packet Delivery Ratio

(PDR), but always above 90%

Are disconnections from the network a problem for packet delivering and latency? In simulations, the MS always experiences disconnections

from Nvs=2 to Nvs=20 Delay decreases with increased Nvs (less time to look for the

MS along the road) Starting from 10 VSs delay do not increase anymore and PDR

is always above 90%

ICC 2007, 27th JuneDavid Tacconi

Conclusions and Future Work Design of a System Architecture to support Mobile

Sink querying a WSN Adaptive geographic routing for packet forwarding Routing technique supports MS disconnection

from the network due to mobility Next steps:

Different topologiesNumber of MS>1More complex mobility patternsMobility management strategiesEnergy consumption evaluationEnergy aware techniques

ICC 2007, 27th JuneDavid Tacconi

Thanks!

David Tacconi

Research staff member in Pervasive Computing area at CREATE-NET research centre

Ph.D. candidate at the University of Florence

david.tacconi@create-net.org

www.create-net.org/~dtacconi