Sensor Network with Mobile Access: Sensor Network with Mobile Access: An Experimental TestbedAn Experimental Testbed

Adaptive Communications and Signal Processing GroupAdaptive Communications and Signal Processing Group

School of Electrical & Computer EngineeringSchool of Electrical & Computer Engineering

Cornell UniversityCornell University

Ithaca, NY 14853Ithaca, NY 14853

Sensor Network with Mobile AccessSensor Network with Mobile Access

Minimal Low Power SensorsMinimal Low Power Sensors– Sensing, storing, deliveringSensing, storing, delivering– Local sensor communicationsLocal sensor communications– Opportunistic multiaccess to Opportunistic multiaccess to

mobile access pointsmobile access points

Powerful Mobile Access PointsPowerful Mobile Access Points– Data collection and transportData collection and transport– Network managementNetwork management

Opportunistic ALOHAOpportunistic ALOHA

Sensor NetworksSensor Networks– Random deploymentRandom deployment– Large number of nodesLarge number of nodes– Limited battery => mobile APLimited battery => mobile AP– AP-initiated uplink => AP-initiated uplink =>

Probabilistic TX, Probabilistic TX,

Use of channel stateUse of channel state

=> => Opportunistic ALOHAOpportunistic ALOHA

Acoustic SENMA TestbedAcoustic SENMA Testbed

Feasibility in Real EnvironmentFeasibility in Real Environment– Verification of the SENMA architectureVerification of the SENMA architecture– Manageable dimension Manageable dimension – Preliminary step to full RF systemPreliminary step to full RF system

Performance EvaluationPerformance Evaluation– MAC protocol: ALOHA vs. Opportunistic-ALOHAMAC protocol: ALOHA vs. Opportunistic-ALOHA– Target detectionTarget detection

System ConfigurationSystem Configuration

Indoor Acoustic CharacteristicsIndoor Acoustic Characteristics

• Free field (< 5 ft) & Free field (< 5 ft) & inverse square lawinverse square law

• Reverberant field: Reverberant field: reflection, diffusion, reflection, diffusion, diffractiondiffraction

• Sound absorbing Sound absorbing treatment treatment

Opportunistic Multiaccess Opportunistic Multiaccess

• Synchronization/Channel EstimationSynchronization/Channel Estimation• Opportunistic Uplink TransmissionOpportunistic Uplink Transmission

Required FunctionsRequired Functions

Sensor Block DiagramSensor Block Diagram

State Machine

Sound SensingPower

(Ext., Battery)

NCOBeacon Detector

RSSI

TX Analog RX Analog

Uplink AccessProtocol

ALTERA PLD

DAC

EPROM

MIC

O-ALOHA ImplementationO-ALOHA Implementation

EPROM(Threshold

Table)

RandomNumber

Generator

-+

BeaconSignal

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TX Decision

Quant-izer

RSSI Address

Mobile AccessMobile Access Point Point

MATLAB TCP client WLAN AP

TCP server

Control

INTERNET

O- ALOHA

Mobile Access Control PanelMobile Access Control Panel

Demo Clip 1Demo Clip 1

Target trajectory findingTarget trajectory finding 1.1. Data collection with no targetData collection with no target

2.2. Appearance of target Appearance of target

3.3. Detection by sensorsDetection by sensors

4.4. New data collectionNew data collection

Related Research IssuesRelated Research IssuesFundamental Research Fundamental Research

– Scalability of large scale random sensor networksScalability of large scale random sensor networks– Energy constrained sensor communications and networkingEnergy constrained sensor communications and networking– Detection, estimation, imaging in large random sampled Detection, estimation, imaging in large random sampled

sensor fieldsensor field– Energy constrained sensors, devices, and computing.Energy constrained sensors, devices, and computing.

Potential Applications Potential Applications – Monitoring: water, air, forest, home, etc.Monitoring: water, air, forest, home, etc.– National security: explosive/narcotic detection National security: explosive/narcotic detection

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