15 feb 2001property of r struzak1 radio link fundamentals coverage (selected issues) prof. ryszard...

15 Feb 2001 Property of R Struzak 1

Radio Link FundamentalsCoverage (Selected Issues)

Prof. Ryszard Struzak [email protected]

United Nations Educational, Scientific and Cultural Organization & International Atomic Energy Agency The Abdus Salam International Centre for Theoretical Physics

Strada Costiera 11, 34014 Trieste-Miramare, Italy, tel. +39 40 2240111, fax +39 40 224163, www.ictp.trieste.itSchool on Data and Multimedia Communications Using Terrestrial and Satellite Radio Links, 12 February - 2 March 2001

[email protected] | www.ictp.trieste.it/~radionet/2001_school/Timetable.html

http://www.ictp.trieste.it/





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• Note: These materials may be used for study, research, and education in not-for-profit applications. If you link to or cite these materials, please credit the author, Ryszard Struzak. These materials may not be published, copied to or issued from another Web server without the author's express permission. Copyright © 2001 Ryszard Struzak. All commercial rights are reserved. If you have comments or suggestions, please contact the author at [email protected].


Summary Slide

• Potential Coverage

• Potential Interference

• Actual Coverage

• Coverage Loss

• Antenna Directivity


Radio Link and Interferer

T Rc

I

Ds

Di


Simplest Scenario

• The transmitter (T), receiver (Rc), and interferer (I) are– isotropic, – at fixed positions,– operating

• at the same time• at the same

frequency

X

Z

Y

AI

Rc

T

Ds Di


Propagation Model

• Free-space

2

4

DPP dtransmittereceived


Normal Operation Conditions

• Minimum quality assured (e.g. BER)• The signal power (Ps) available at the

receiver should be Prmin or greater– White, isotropic noise

• The minimum signal-to-interference power ratio at the receiver input (SIR) should be SIRmin or greater– Other noise


Potential Coverage

• No interference from other transmitters/ sources of radio waves

• White, isotropic noise exists!

• Criterion: S/N or Prmin


Potential Coverage

• Sphere centred at the transmitter (0, 0, 0)R

trn

s

PP

Rmin4

T


Potential Coverage (cont)

• With no interferer, communication is possible if the receiver is located on the surface of, or inside, the potential coverage sphere– At the surface of the sphere Ps = Psmin– Inside the sphere Ps > Psmin

• Outside the sphere no communication is possible because Ps < Psmin


Potential Interference

• A single interferer

• Isotropic white noise ignored

• Criterion: S/I


Potential Interference 2

Dt

Di

P

PSIR

i

t

minSIRP

PQ

i

t

minSIRQ

P

P

i

t


Potential Interference (cont.1)

• If SIR = SIRmin then

2

2

minmin

Di

DtQ

Dt

DiSIRQSIR



0)(

)(

)(

222222

222

2222

2222

2222

zyAxQzyx

QzyAx

zyx

D

D

zyAxD

zyxD

i

t

i

t



Q

AQQAzy

Q

QAxQ

Q

AQAQQAxQAzyxQ

QzQyQAQAxQxzyx

1)1()1(

12))(1(

2

22222

2

22222222

2222222


Potential Interference (cont. 4)

2

222

2

)1(1

1

Q

QAzy

Q

AQx

Q



1

1

2222

Q

AQRi

Q

QAB

RizyBx



B Ri

A

T

I

Z

Y

X


Interference Cone, Q > 1

Z

Y

XT

Interferer inside the sphere


Interference Cone (cont.)

Q>1

Z

Y

XT

B

/2

dRi 22

)2/cos(

RiBd

Bd

22)2/cos(

RiB

B


Interference Cone, Q < 1

I

X

Wanted transmitter inside the sphere


Transmitter Domination (Q > 1)

• The interferer is inside the sphere; the transmitter is outside – SIR = SIRmin at the surface of the sphere– SIR < SIRmin inside the sphere– SIR > SIRmin outside the sphere

• The receiver must be outside the sphere for normal operation

• Note: The sphere is on the right side of plane x = (A/2)


The Balance (Q = 1)

• The sphere degenerates into plane x = A/2 that creates two half-spaces

• The transmitter is on the left half-space where SIR > SIRmin

• The interferer is on the right half-space where SIR < SIRmin

• The receiver must be on the left side of the plane x = A/2 for normal operation


Interferer Dominance (Q < 1)

• The interferer is outside the sphere; the transmitter is inside (jamming)– SIR = SIRmin at the surface of the sphere– SIR > SIRmin inside the sphere– SIR < SIRmin outside the sphere

• The receiver must be inside the sphere for normal operation

• Note: The sphere is on the left side of plane x = (A/2)


Actual Coverage: Q>1

As long as d > 0, the actual and the potential coverage regions coincide. No coverage loss.

d = B – (Rs + Ri)

Sphere of potential coverage

Sphere of potential interference


Actual Coverage: Q>1 (cont)

Coverage lost

Potential Interference Sphere

Potential Coverage Sphere

Z = 0


Actual Coverage: Q>1 (cont.2)

Coverage lost



Z = 0

Actual Coverage Region


Actual Coverage: Q<1



Actual Coverage Region

Z = 0

Lost coverage


Coverage loss

• Coverage Loss = = Potential Coverage – Actual coverage – Volume, – Surface, – Population, etc

• Relative Coverage Loss = % of the potential coverage lost


Coverage loss (cont)

If Q>1 and if the whole sphere of potential interference is contained within the sphere of potential coverage, then

Relative Coverage Loss (Volume) = = (Ri/Rs)3

Relative Coverage Loss (Equatorial plane) = = (Ri/Rs)2


Summary

• With isotropic transmitter, receiver and interferer, the coverage depends on:

• Transmitter power Pt

• Weighted ratio of the transmitter power to interferer power Q = P/(Pi SIR)

Continued


Summary (cont)

• Distance between the transmitter and interferer, A.

• If the number of transmitters over a given area increases, the distance between them decreases


Antenna Directivity

• Directive antenna can eliminate (or attenuate) radiation coming from a limited number of discrete interferers

• It cannot eliminate isotropic noise


Antenna Directivity

• Receiving antenna gain = G within apical angle and is null elsewhere


Directive Antenna Effectiveness

Effective Limiting case Not effective

TTT

I I I


Relations between angles

T I

Receiver

R

R

R

h

2

2

22

22


Effectiveness Circle

T I

Receiver

R Rh

A

cot2

cos

sin2A

Rh

AR


Effectiveness on a Plane

T

T I

2

2

2

sin

2sin

2

)2sin(2

A

R

Surface

Rc


3D Effectiveness

`

B

R

hX

Y

Z

• Vectors h and R lie in plane z = ay

• The plane turns around axis OX

• The tip of vector h encircles point B

• The tip of vector R encircles the tip of vector h

O


3D Effectiveness (cont. 1)

• Parametric equation

sincos

coscos

sin

Rhz

Rhy

RBx



R

x

R

x

hRhRhzy

RBxx

*1sin1cos

*sin

coscos2)cos(

sin*

2

22222



2222222

22222

22

2222

*2*

**2

*1

*12

RxRhhzyx

xRxRhh

R

xR

R

xhRhzx



322222

2

3

42

arcsin1arcsin2

hRhRh

R

hhR

Volume



Cross-section in plane x = B

Cross-section in plane z = ay

(h + R)

2R


Propagation Model

• Different propagation mechanism for the wanted and the interfering signals

• Variability and random factors

• Probabilistic approach

15 feb 2001property of r struzak1 radio link fundamentals coverage (selected issues) prof. ryszard...

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