rf path loss in the vicinity of steller sea lion haulouts alexander lau masc graduate student...

RF Path Loss in the Vicinity of Steller Sea Lion Haulouts

Alexander Lau

MASc graduate student

Electrical & Computer Engineering

Project Background

• Previous microwave transmission work has been done on buildings and trees but none has been done in a very remote rocky environment

• This research trip to the Queen Charlottes has produced some RF path loss data at haulout sites

• We are using 2.4 and 5.25 GHz due to patch antenna size restrictions and these frequencies are readily available.

Definitions

Link budget: compilation of all the factors that reduce the transmitted power from an antenna of

a transmitter such as the environment in which the signal propagates.

Coverage: the total area where a signal is present.

Overview

• Objective

• Protocol

• Equipment used

• Results

• Future studies

Objective

• To characterize RF path loss at 2.4 GHz and 5.25 GHz at typical haulouts in support of future link budget and coverage studies

• To look for signal interference at 2.4 GHz and 5.25 GHz

Protocol

1. Arrive at the haulout, unpack and set up the test equipment. Place receiver near highest point.

2. Record 2 to 4 signal strength measurements (dBm) at 2.4 and 5.25 GHz, bearing angle, GPS position, inclination angle, and distance between receiver and transmitter at various elevations in ~2m increments.

Constraints

Approximately 30 mins per site, and max. 200 data points.

Portable and battery-powered equipment.

Equipment Used

• XL Microwave 2261 Analyze-R Wideband Receiver - 6 hrs. operating time, 3 hours recharge - light weight (<7 lbs.)- bandwidth is 2 MHz- sensitivity is -100 dBm - 4 selectable frequency bands: 2.400–2.484 GHz,

5.150–5.250 GHz, 5.150–5.250 GHz, 5.725– 5.875 GHz

Equipment Used (cont.)

• XL Microwave 2230 Survey-R Transmitter

- 4–5 hrs. operating time, 3 hours recharge

- 2 tuneable frequency bands: 2.400–2.483 GHz &

5.150–5.999 GHz with 1 MHz resolution

- power output is 10 dBm (0.01 watts)• Geo Explorer XT 128 MB (GPS)• Contour XLRic (laser gun)

Microwave Propagation Fundamentals

• Free-space loss is the attenuation of a signal due to spreading of the electromagnetic wave.

Equation for Free-space loss:

Attenuation(dB) = 92.467 + 20log10(fGHz) + 20log10(Dkm)

Where: fGHz = frequency in GHz

Dkm = distance between antennas in km

Microwave Propagation Fundamentals (cont.)

• Total Path Loss is the sum of the gain of both antennas minus the free space loss and any additional loss such as water vapor, mist, fog, rainfall and Fresnel reflection loss

• Fresnel loss is a multi-path reflection loss due to reflective surfaces such as water, buildings and mountain peaks in the Fresnel zone

• Fading are losses encountered during abnormal propagation conditions such as irregularities and fluctuations in atmospheric temperature, humidity and pressure.

Microwave Propagation Fundamentals (cont.)

• 3 traditional radiation fields exist in free space as a result of the radiated power of an antenna:Near-field – the region closest to the antenna and for which the reactive field dominates over the radiative fields.Fresnel zone – the region between near-field and far-field and for which the radiation fields dominate and angular field distribution depends on distance from the antenna.Far-field – the region where radiation pattern is independent of distance.

Results

Haulout sites :

• McInnes Rocks • Steele Rocks • Warrior Rocks • Langara Rocks

McInnes Rocks

McInnes

Island

Insert Picture

Insert Picture

Signal Strength vs. Distance when Base Station at 1.555 m(Ascending McInnes Rock)

-120

-100

-80

-60

-40

-20

0

0 5 10 15 20 25

Distance (m)

Sign

al S

tren

gth

(dBm

)

2.4 GHz

2.4 GHz Free Space

5.25 GHz

5.25 GHz Free-space

Behind Rock Behind Rock

Steele Rocks

Steele Rocks

Signal Strength vs. Distance when Base Station at 1.555m(Ascending Steele Rock)

-120

-100

-80

-60

-40

-20

0

0 10 20 30 40 50

Distance (m)

Sig

nal

Str

en

gth

(d

Bm

)

2.4 GHz

2.4 GHz Free-space

Behind Rock

Signal Strength vs. Distance when Base Station at 1.555m(Descending Steele Rock)

-120

-100

-80

-60

-40

-20

0

0 5 10 15 20 25 30 35 40 45 50

Distance (m)

Sig

nal S

tren

gth

(dB

m)

5.25 GHz

5.25 GHz Free-space

Behind Rock

Warrior Rocks

Warrior

Rocks

Insert Picture

Insert Picture

Signal Strength vs. Distance when Base Station at 0 m(Ascending Warrior Rocks)

-120

-100

-80

-60

-40

-20

0

0 5 10 15 20

Distance (m)

Sign

al S

tren

gth

(dBm

)

2.4 GHz2.4 GHz Free-space5.25 GHz5.25 GHz Free-space

Behind RockBehind Rock

Signal Strength vs. Distance when Base Station at 1.555 m(Ascending Warrior Rocks)

-120

-100

-80

-60

-40

-20

0

0 5 10 15 20

Distance (m)

Sign

al S

tren

gth

(dBm

)

2.4 GHz2.4 GHz Free-space5.25 GHz5.25 GHz Free-space

Behind RockBehind Rock

Signal Strength vs. Distance when Base Station at 0 m(Descending Warrior Rocks)

-120

-100

-80

-60

-40

-20

0

0 5 10 15 20 25 30

Distance (m)

Sign

al S

tren

gth

(dBm

)

2.4 GHz2.4 GHz Free-space5.25 GHz5.25 GHz Free-space

Line of Sight

Out of Sight

Signal Strength vs. Distance when Base Station at 1.555 m(Descending Warrior Rocks)

-120

-100

-80

-60

-40

-20

0

0 5 10 15 20 25 30

Distance (m)

Sign

al S

tren

gth

(dBm

)

2.4 GHz2.4 GHz Free-space5.25 GHz5.25 GHz Free-space

Line of Sight Out of Sight

Langara Rocks

Langara

Rocks

Insert Picture

Insert Picture

Signal Strength vs. Distance when Base Station at 0 m(Ascending Langara Rocks)

-120

-100

-80

-60

-40

-20

0

0 5 10 15 20 25

Distance (m)

Sign

al S

treng

th (d

Bm)

2.4 GHz

2.4 GHz Free-space

5.25 GHz

5.25 GHz Free-space

Behind RockBehind Rock

Out of View

Peak above Receiver

Peak below Receiver

Signal Strength vs. Distance when Base Station at 1.555 m(Ascending Langara Rocks)

-120

-100

-80

-60

-40

-20

0

0 5 10 15 20 25

Distance (m)

Sign

al S

treng

th (d

Bm)

2.4 GHz Raw Measurement

2.4 GHz Theoretical

5.25 GHz Raw Measurement

5.25 GHz Theoretical

Behind Rock

Behind Rock

Peak above Receiver

Peak below Receiver

Excess Path Loss due to Shadowing when Base Station at 0m

-20

-10

0

10

20

30

40

50

60

-80 -70 -60 -50 -40 -30 -20 -10 0

Depression Angle (degrees)

Exce

ss p

ath

loss

(dBm

)

2.4 GHz

5.25 GHz

Conclusion

Future Studies

• Attend future research trips and devote more time on field measurements

References

• Telecommunication Transmission Handbook, Third Edition by R. L. Freeman (1991)

• Practical Communication Antennas with Wireless Applications by L. Setian (1998)

• Antenna Theory and Design, Second Edition by W. L. Stutzman and G. A. Theile (1997)

• British Columbia topo50 Vol. 2 and 3 by SoftMap (2001)

Acknowledgements

• North Pacific Marine Mammal Consortium

• Dr. Andrew Trites

• Dr. Royann Petrell

• Dr. Dave Michelson

• Dr. William G. Dunford

Questions?