9 Mar 2007

UBC – IEEE Workshop on Future Communications Systems

1

UWB Radiowave Propagation within the Passenger Cabin of a

Boeing 737-200 AircraftJames Chuang, Ni Xin, Howard Huang, Simon Chiu, and David G. Michelson

jimc|davem@ece.ubc.ca

9 Mar 2007 2

I. Introduction• Studies of wireless aboard aircraft have been conducted by:

– German Aerospace Centre (DLR) and the European Union’s WirelessCabin project

– Old Dominion University and NASA– Qualcomm and Boeing

• These have emphasized:– Studies and field trials for existing technologies,– Measurement of RF coverage using client devices,– Simulation of aircraft interiors using RF coverage tools, – Characterization of the wideband channel response.

Past Work and Its Limitations• UWB holds great promise for facilitating,

– deployment of high data rate multimedia and network access services.

– operations and maintenance through deployment of sensor networks and precise positioning system.

• Past efforts to develop measurement-based models for UWB propagation channels have focused on residential, office, outdoor and industrial environments

• No previous published work concerning the UWB propagation channel within aircraft passenger cabin or the effect of human presence within such environments.

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Where do we fit in?

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Conventional Environments

Aircraft Environment

ConventionalWireless Systems

UWBUBCRSL

IEEE 802.15.3a/4a

Many Organizations

DLR & EUNASA & Boeing

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Objectives• Characterize large-scale aspects of UWB propagation within

the passenger cabin of an aircraft:– Distance and frequency dependence of path loss.– Time dispersion

• RMS delay spread• Parameters of the AR-FD channel model.

– The effect of human presence.• Prepare for the next step: characterization of the detailed

structure of the UWB channel impulse response.

Outline• Section II – Measurement Approach

– Point-to-Multipoint and Peer-to-Peer Configurations• Section III – UWB Channel Sounder

– Implementation, Settings and Configuration– Data Collection, Receiver Sampling Strategy

• Section IV – Results– Distance and Frequency Dependence of Path Loss– Time Dispersion Parameters and AR-FD Channel

Modeling• Section V – Conclusions

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II. Measurement Approach

• The main cabin of a Boeing 737-200 is:• 21 m in length,• 3.54 m in width,• 2.2 m in height.

• We have considered both point-to-multipoint and peer-to-peer wireless system configurations.

Point-to-Multipoint Configuration

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• Transmitting antenna (access point) on the ceiling

• Receiving antenna (user terminals) placed at headrest, armrest and footrest levels.

RX ANTENNA

Peer-to-Peer Configuration

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• Transmitting antenna (user terminal) placed at headrest, armrest and footrest levels

• Receiving antenna (user terminal) placed at headrest, armrest and footrest levels.

RX ANTENNA TX ANTENNA

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III. UWB Channel Sounder

LNAPA

MeasurementReceiver

Laptop

~

RB

Control Signals

Source

Reflections from objects in the environment

Display/ Controller

Transmitting Antenna

VNA

Receiving Antenna

Implementation• An Agilent E8362B vector network analyzer (VNA) was

used to collect complex frequency response of the channel throughout the aircraft.

• Two UWB biconical antennas, Electro-metrics 6865, were used as both the transmitter and receiver.

• Two 15 m long LMR-400 UltraFlex coaxial cables were used to connect the antennas to the VNA.

• Calibration is done up to the antenna connectors.• Both the antennas and the channel are treated as the device

under test by the VNA.

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Configuration and Settings

VNA SettingsStart Frequency 3 GHzStop Frequency 10.6 GHzFrequency Steps 6401Transmit Power 5 dBmIF Bandwidth 3 kHzSweep Time 2 secTime Resolution 132 psec

EM-6865 UWB Biconical Antenna

Agilent E8362B PNA

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Data Collection• Point-to-multipoint configuration

• Tx antenna• near the cabin ceiling.• at 3 locations throughout the cabin.

• Rx antenna • at headrest, armrest, footrest.• at over 50 locations throughout the cabin.

• Redundancies in the data base allowed us to check the consistency of our results.

• At 3 transmitter locations,• At over 50 receiver locations.

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Receiver Sampling StrategyAisle

Row 2

Row 3

Row 4

Row 5

Row 6

Row 7

Row 8

Row 9

Row 10

Row 11

Row 12

Row 13

Row 14

Row 15

Row 16

Row 17

Row 18

Row 19

Row 20

Row 21

Row 22

Passengers

12

4

3

1

11

10

98

7

65

19

16

1514

13

1817

22

2120

ABCDEFTx LocationPoint-to-Multipoint

2

23 24

Aisle

Row 2

Row 3

Row 4

Row 5

Row 6

Row 7

Row 8

Row 9

Row 10

Row 11

Row 12

Row 13

Row 14

Row 15

Row 16

Row 17

Row 18

Row 19

Row 20

Row 21

Row 22

12

4

3

1

11

10

98

7

65

19

16

1514

13

1817

ABCDEF

Tx LocationPoint-to-Multipoint

2

Aisle

Row 2

Row 3

Row 4

Row 5

Row 6

Row 7

Row 8

Row 9

Row 10

Row 11

Row 12

Row 13

Row 14

Row 15

Row 16

Row 17

Row 18

Row 19

Row 20

Row 21

Row 22

2

ABCDEF

Tx LocationPoint-to-Multipoint

1 3

4 5 6

7 8 9

10 11 12

13 14 15

16 17 18

19 20 21

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IV. Results• We processed our measurement database to characterize large-

scale aspects of UWB propagation within the passenger cabin of an aircraft:– Distance and frequency dependence of path loss.– Time dispersion

• RMS delay spread• Parameters of the AR-FD channel model.

– The effect of human presence.

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Distance & Frequency Dependence of Path Loss• We estimated the parameters of the IEEE 802.15.4a UWB

path loss model:

where d and f are distance and frequency, respectively, d0and fc are the reference distance and frequency, n and κ are the distance and frequency exponent, and k is a constant.

• The distance and frequency are assumed to be independent of each other.

( )2

0

,n

pc

d fG d f kd f

κ− −⎛ ⎞ ⎛ ⎞

= ⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠

Distance Dependent Path Loss• We averaged path gain across the entire frequency response

and fit the results to the power law path loss equation

in dB scale

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( ) ( ) 2

1

1 ,M

ii

PL d H f dM =

= ∑

( ) 0 100

10 logdBdPL d PL n Xd σ

⎛ ⎞= + +⎜ ⎟

⎝ ⎠

Path Gain with No Passengers

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100 101-70

-65

-60

-55

-50

Distance [m]

Pat

h G

ain

[dB

]Headrest

Armrest

Footrest

Path Gain with Passengers in Every Other Seat

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100

101

-70

-65

-60

-55

-50

Distance [m]

Path

Gai

n [d

B]

Headrest

Armrest

Footrest

Path Gain with Passengers in Every Seat

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100

101

-70

-65

-60

-55

-50

Distance [m]

Path

Gai

n [d

B]

Headrest

Armrest

Footrest

Distance Dependent Path Loss Parameters

Passenger Density

Mounting Point

Path loss exponent,n

1-m Intercept(dBm)

Location variabilityσ (dB)

Headrest 2.1 -40.0 5.0Armrest 2.2 -42.6 5.1

No Passengers

Footrest 2.2 -45.1 4.7Headrest 2.4 -39.7 5.3Armrest 2.5 -43.1 5.2

Passengers in every other seats

Footrest 1.9* -49.1* 3.8*Headrest 2.6 -39.9 4.0Armrest 2.5 -46.0 3.9

Passengers in every seat

Footrest 1.7* -50.9* 2.4*

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* only measured in aisle seats

Frequency Dependent Path Loss

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( )PL f f κ−∝

4 6 8 10-90

-80

-70

-60

-50

-40

-30

Frequency [GHz]

Pat

h G

ain

[dB

]

κ(d) with Receiver at Headrest

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2 4 6 8 10 12 14-1.5

-1

-0.5

0

0.5

1

1.5

Distance [m]

kapp

a

κ(d) with Receiver at Armrest

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2 4 6 8 10 12 14-1.5

-1

-0.5

0

0.5

1

1.5

Distance [m]

kapp

a

κ(d) with Receiver at Footrest

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2 4 6 8 10 12 14-1.5

-1

-0.5

0

0.5

1

1.5

Distance [m]

kapp

a

Time Dispersion Parameters• Power Delay Profile

• RMS delay spread

• The ratio of power in the LOS and scattered components

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( )

( )

2k k

kRMS

kk

P

P

τ ττ

τ=∑∑

( )

( )LOS k

LOS k

SCAT SCAT kk

PPP P

τ

τ=∑∑

( ) ( ) 2k k k

kP aτ δ τ τ= −∑

CDF of RMS Delay Spread

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5 10 15 20 25 300.0

0.2

0.4

0.6

0.8

1.0

RMS Delay Spread [ns]

Cum

ulat

ive

prob

abili

ty

HeadrestArmrestFootrest

CDF of the Ratio of Power in the LOS and Scattered Components

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0 1 2 3 4 50.0

0.2

0.4

0.6

0.8

1.0

PLOS/PSCAT

Cum

ulat

ive

prob

abili

ty

HeadrestArmrestFootrest

Autoregressive Frequency Domain Channel Model

• The Difference Equation,

• The Poles,

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1

ˆ ˆ( , ; ) ( , ; ) ( , ; )p

k i k i ki

H f t x a H f t x U f t x−=

+ =∑

( )( )1

1

1

1k

ii

G zp z−

=

=−∏

AR-FD Model – Pole Distribution for Receiver at Headrest

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-1.0 -0.5 0.0 0.5 1.0-1.0

-0.5

0.0

0.5

1.0

Real Part

Imag

inar

y Pa

rt

all seatsoccupied

50% of seatsoccupied

emptyaircraft

AR-FD Model – Pole Distribution for Receiver at Armrest

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-1.0 -0.5 0 0.5 1-1.0

-0.5

0.0

0.5

1.0

Real Part

Imag

inar

y Pa

rt

all seats occupied

50% of seatsoccupied

empty aircraft

AR-FD Model - Pole Distribution for Receiver at Footrest

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-1.0 -0.5 0.0 0.5 1.0-1.0

-0.5

0.0

0.5

1.0

Real Part

Imag

inar

y Pa

rt

all seats occupied

50% of seatsoccupied

emptyaircraft

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V. Conclusions• We characterized the large-scale aspect of UWB propagation

in point-to-multipoint configuration within the passenger cabin of a mid-size airliner.

• These results include:– Distance and frequency dependence of path loss,– Time dispersion parameters,

• RMS delay spread• PLOS/PSCAT

• Parameters of the AR-FD channel model– The effect of human presence.

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Conclusions - 2• The results will assist those:

– planning UWB deployment and field trials in aircraft,– wishing to verify the results of eletromagnetic simulations

of aircraft interiors,– wishing to simulate UWB aircraft systems with realistic

channels.

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Future Work• Peer-to-peer configuration• Going beyond the passenger cabin, e.g., cargo holds, wings,

cockpit, etc.• Characterization of channel impulse response • Small-scale fading parameters.

Acknowledgements• We are grateful to the management and staff of the BCIT

Aerospace Technology Campus at Vancouver International Airport for providing us with access to their Boeing 737-200 aircraft during the course of this study.

• We thank Ivan Chan, Alex Lee, Chris Pang, Cecilia Yeung, Chad Woodworth, and especially Shahzad Bashir for their considerable assistance during the data collection phase of this study.

• This work was supported by Bell Canada’s University Laboratories R&D Program, Nokia Canada, and the Natural Sciences and Engineering Research Council of Canada.

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References1. N.R. Diaz and M. Holzbock, “Aircraft cabin propagation for multimedia

communications,” Proc. EMPS 2002, 25-26 Sep. 2002.2. C.P. Niebla, “Coverage and capacity planning for aircraft in-cabin wireless

heterogeneous network,” Proc. IEEE VTC 2003-Fall, 6-9 Oct. 2003, pp. 1658-1662.

3. G.A. Berit, H. Hachem, J. Forrester, P. Guckian, K.P. Kirchoff, B.J. Donham, “RF propagation characteristics of in-cabin CDMA mobile phone networks,”Digital Avionics Systems Conference, 30 Oct. – 3 Nov. 2005, pp. 9.C.5-1---9.C.5-12.

4. N.R. Diaz and J.E.J. Esquitino, “Wideband channel characterization for wireless communication inside a short haul aircraft,” Proc. IEEE VTC 2004 Spring, 17-19 May 2004, pp. 223-228.

5. A.F. Molisch, “Ultrawideband propagation channels: Theory, measurement, and modeling,” IEEE Trans. Veh. Technol., vol. 54, no. 5, Sep. 2005, pp. 1528-1545.

References (cont.)6. A.F. Molisch, et al., “A comprehensive standardized model for ultrawideband

propagation channels,” IEEE Trans. Antennas Propag., vol. 54, no. 11, Nov. 2006, pp. 3151-3165.

7. T.B. Welch, et al., “The effects of the human body on UWB signal propagation in an indoor environment,” IEEE J. Sel. Areas Commun., vol. 20, no. 9, Dec. 2002, pp. 1778-1782.

8. S.J. Howard and K. Pahlavan, “Autoregressive modeling of wide-band indoor propagation,” IEEE Trans. Commun., vol. 40, no. 9, Sep. 1992, pp. 1540-1552.

9. S.S. Ghassemzadeh, R. Jana, C.W. Rice, W. Turin, and V. Tarokh, “Measurement and modeling of an ultra-wide bandwidth indoor channel,” IEEE Trans. Commun., vol. 52, no. 10, Oct. 2004, pp. 1786-1796.

10. N. Xin, and D. G. Michelson, “Frequency domain analysis of the IEEE 802.15.4a standard channel models,” Proc. IEEE WCNC 2007, 11-15 Mar. 2007.

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