Ultra-Wideband Channel Model for Intra-Vehicular Wireless

Sensor Networks

C. Umit BasElectrical and Electronics Engineering , Koc University

History of In-Vehicle Networking

Early days of automotive electronicsEach new function implemented as a stand-alone ECU, subsystem containing a microcontroller and a set of sensors and actuators

Data exchanged between point-to-point links

sensor sensor

ECU

Body Control Module

ECU

History of In-Vehicle Networking

In the 1990sIncrease in the number of wires and connectors caused weight, cost, complexity and reliability problems

Developments in the wired communication networks

sensor

ECU

sensoractuat

orsensor

ECUECU

Body Control Module

History of In-Vehicle Networking

In the 1990sIncrease in the number of wires and connectors caused weight, cost, complexity and reliability problems

Developments in the wired communication networks

Multiplexing communication of ECUs over a shared link called bus

sensor

ECU

sensoractuat

orsensor

ECUECU

Body Control Module

History of In-Vehicle Networking

TodayIncreases in number of sensors as electronic systems in vehicles are replacing purely mechanical and hydraulic systems causes weight, cost, complexity and reliability problems due to wiring

Advances in low power wireless networks and local computing

sensor

ECU

sensoractuat

orsensor

ECUECU

Body Control Module

sensor sensor

sensor

sensor

sensorsensor

ECU

sensor

History of In-Vehicle Networking

TodayIncreases in number of sensors as electronic systems in vehicles are replacing purely mechanical and hydraulic systems causes weight, cost, complexity and reliability problems due to wiring

Advances in low power wireless networks and local computing

Intra-Vehicular Wireless Sensor Networks (IVWSN)

sensor

ECU

sensoractuat

orsensor

ECUECU

Body Control Module

sensor sensor

sensor

sensor

sensorsensorsensor

Motivation for Intra-Vehicular Wireless Sensor

NetworksProvide savings in

Part cost

Cost of assembly, repair and maintenance

Fuel consumption

Decreases cost of change/inflexibilityCabling connectivity has little design flexibility and upgrades

Enable new sensor technologies to be integrated into vehicles

E.g. tire pressure monitoring systems, intelligent tire

Replace current sensors not functioning well enough due to cabling.

IVWSN: Distinguishing Characteristics

Tight interaction with control systemsSensor data used in the real-time control of mechanical parts in different domains of the vehicles

Very high reliabilitySame level of reliability as the wired equivalent

Energy efficiencyRemove wiring harnesses for both power and data

HeterogeneityWide spectrum for data generation rate of sensors in different domains

Harsh environmentLarge number of metal reflectors, a lot of vibrations, extreme temperatures

Short distanceMaximum distance in the range 5m-25m

What is UWB?

Transmission from an antenna for which the emitted signal bandwidth exceeds the lesser of 500MHz and 20% of the center frequency.

Motivation for Ultra-Wideband

Vehicle control systems requireVery high reliability,

Strict delay guarantee.

UWB providesResistance to multipath fading,

Resistance to power loss due to lack of line of sight,

Resistance to interference,

Robust performance at high data rate with very low transmit power.

Wireless Channel Measurements

Building a detailed model for IVWSN requiresClassifying the vehicle into different parts of similar propagation characteristics

Collecting multiple measurements at various locations belonging to the same class

engine

beneath chassis

passenger compartment

trunk

Literature Review

Measurement Setup

Agilent 8719ES Vector Network Analyzer

3.1 GHz to 10.6 GHz using 1601 points

Measurement Locations

18 transmitter locations & 1 receiver location

At each location 9 antenna positions on 3x3 square grids with 5 cm spacing

Totally 81*18 measurement points

Data Processing

Large & Small Scale Fading Statistics

Large-Scale Statistics81 measurements at each location averaged to obtain the small-scale averaged PDP (SSA-PDP)

Large-scale statistics derived by using 18 SSA-PDP

Small-Scale StatisticsVariations of 81 Local PDP around SSA-PDP used to derive small-scale statistics

Large Scale Statistics

Modeled by using small scale averaged power delay profiles (SSA-PDP) for 18 locations

Path Loss Model

   

General Shape of Impulse Response

Modified Saleh-Valenzuela Model

cluster amplitude

ray decay rate

inter-arrival time of clusters

Small Scale Statistics

Characterized by fitting amplitude values of 81 local PDP to alternative distributions

Distribution of Amplitudes for Delay Bins

σ of Lognormal Distributions

σ is independent of time

σ of Lognormal Distributions

means of σ have no trivial relation with distance

σ of Lognormal Distributions

Small scale fading of different delays is not correlated

Susceptibility of Large-Scale Statistics

Susceptibility of Small-Scale Statistics

Regeneration of Statistical Channel Model

Model Validation – Qualitative Comparison

Measured Power Delay Profiles Simulated Power Delay Profiles

Model Validation – Quantitative Comparision

Conclusions

Intra-vehicular wireless sensor networksProvide cost reduction

Enable new sensor technologies to be integrated in vehicles

Channel characteristics beneath the chassisLarge scale statistics: path loss, power variation,

General shape of impulse response: modified Saleh-Valenzuela model

Small scale statistics

Proposed model validated with both qualitative and quantitative comparisons

Publications

C. U. Bas and S. C. Ergen, “Ultra-Wideband Channel Model for Intra-Vehicular Wireless Sensor Networks Beneath the Chassis: From Statistical Model to Simulations”, IEEE Transactions on Vehicular Technology, vol. 62, no. 1, pp. 14-25, January 2013. [pdf | link]

U. Demir, C. U. Bas and S. C. Ergen, "Engine Compartment UWB Channel Model for Intra-Vehicular Wireless Sensor Networks", IEEE Transactions on Vehicular Technology, vol. 63, no. 6, pp. 2497-2505, July 2014. [pdf | link]

C. U. Bas and S. C. Ergen, “Ultra-Wideband Channel Model for Intra-Vehicular Wireless Sensor Networks”, IEEE WCNC, April 2012. [pdf | link]

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Thank You!

QUESTIONS?

Umit Bas: cbas@ku.edu.tr

Wireless Networks Laboratory: http://wnl.ku.edu.tr