PLANNING OF BROADCASTING SERVICES

Philip LavenDirector, Technical DepartmentEuropean Broadcasting Union

(based on a presentation by Terry O’Leary, EBU)

ITU-EBU Workshop, Sofia 8 June 2004

COMPARING ANALOGUE & DIGITAL

Conventional VHF/FM (narrow band)

S/N 30 - 40 dB

PR 30 - 50 dB

% time 99

% location 50

Rx antenna 10 m (fixed)

SFN NO

Network gain NO

Digital T-DAB (wide band)

S/N 10 - 15 dB

PR 10 - 15 dB

% time 99

% location 99

Rx antenna 1.5m (mobile)

SFN YES

Network gain YES

∆∆∆∆dB

- 20

- 20

+ 13

+ 10

- 6

BROADCASTING

Getting information

from ‘A’ to ‘B’

A BPropagation

PROPAGATION (A to B)

(Feeder loss)

Free space loss: ∝ 1/d2

Path loss: terrain, clutter, diffraction, …

Received field strength is a function

of path, antenna heights, distance, location, time, ...

E (dB µV/m)

d (km)

free space

PROPAGATION PREDICTION

1 0 2 0 5 0 1 0 0 01 0 0 2 0 0 4 0 0 6 0 0 8 0 0

9 0

8 0

7 0

6 0

5 0

4 0

3 0

2

1 0

0

– 1 0

– 2 0

– 3 0

– 4 0

– 5 0

Field strength (dB µµµµV/m) for 1 kW e.r.p.

dB µµµµV/m

Logarithmic scale Linear scaleDistance (km)

Frequency: 30-250 MHz (Bands I, II and III); land; 50 % of the time;50 % of the locations; h2 = 10 m; ∆h = 50 m

Free space

h1 = 600 mh1 = 300 m

h1 = 1200 m

0

h1 = 37.5 mh1 = 75 mh1 = 150 m

Coverage: 50 % time

30-250 MHZ

land50% time

50 % location

Rx h 10m

STATISTICS

Why important?- rapid failure characteristics of digital systems

EXAMPLE:Analogue (‘gradual degradation’)

Grade 4 → Grade 3 > 10 dB

Digital (‘catastrophic degradation’)

Grade 4 → Grade 1 ∼ 2 dB

TIME STATISTICS

• SEASONAL VARIATION

• STANDARD DEVIATION ( σ )A FUNCTION OF DISTANCE ( range 0 — ∼ 7 dB)

r2r1

E

TIMESEASON 1 SEASON 2 SEASON 1

1 %

50 %

r1

r2

}}}} σσσσ1

σσσσ2

TIME STATISTICS

E

time

W

I

W - I99 % time

level

1 % time level

PROPAGATION PREDICTION

90

80

70

60

50

40

30

20

10

-10

-20

-30

-40

-5010 20 10050 1000800600400

Field strength (dB µµµµV/m) for 1 kW e.r.p.

dB µµµµV/m

h1 = 1200 mh1 = 600 mh1 = 300 m

h1 = 750 mh1 = 37.5 m

h1 = 150 m

0

300200

Logarithmic scale Linear scale

Distance (km)

Frequency: 30-250 MHz; Bands I, II, III; Land; 1 % time;50 % of the locations; h2 = 10 m; ∆h = 50 m

Free space

Interference: 1 % time

50 % time

LOCATION DISTRIBUTION

LOG-NORMAL DISTRIBUTION

σ is a measure of the ‘deviation’

(σ = 5.5 dB for T-DAB)

Number (relative occurrence)

Em1( r1 )Eref

1 %

r1

13 dB

m1 = Eref + 13

σ

PROPAGATION PREDICTION

1 0 2 0 5 0 1 0 0 01 0 0 2 0 0 4 0 0 6 0 0 8 0 0

9 0

8 0

7 0

6 0

5 0

4 0

3 0

2 0

1 0

0

- 1 0

- 2 0

- 3 0

- 4 0

- 5 0

h 1 = 1 2 0 0 m

d B µµµµ V / m

L o g a r i t h m i c s c a l e L i n e a r s c a l eD i s t a n c e ( k m )

F r e q u e n c y : 3 0 - 2 5 0 M H z ; B a n d s I , I I , I I I ; L a n d ; 5 0 % t i m e ; 5 0 % o f t h e l o c a t i o n s ; h 2 = 1 0 m ; ∆ h = 5 0 m

F r e e s p a c e

h 1 = 6 0 0 m h 1 = 3 0 0 m

h 1 = 7 5 m h 1 = 3 7 . 5 m

h 1 = 1 5 0 m

9 0

8 0

7 0

6 0

5 0

4 0

3 0

2 0

1 0

- 1 0

- 2 0

- 3 0

- 4 0

- 5 01 0 2 0 1 0 05 0 1 0 0 0 8 0 06 0 04 0 0

d B µµµµ V / m

h 1 = 1 2 0 0 m

h 1 = 6 0 0 mh 1 = 3 0 0 m

h 1 = 7 5 0 mh 1 = 3 7 . 5 m

h 1 = 1 5 0 m

0

3 0 02 0 0

L o g a r i t h m i c s c a l e L i n e a r s c a l e

D i s t a n c e ( k m )

F r e q u e n c y : 3 0 - 2 5 0 M H z ; B a n d s I , I I , I I I ; L a n d ; 1 % t i m e ; 5 0 % o f t h e l o c a t i o n s ; h 2 = 1 0 m ; ∆ h = 5 0 m

F r e e s p a c e

WANTED SIGNAL50 % timeh1 = 150 mERP = 10 kW = 10 dBkWdistance = 20 kmEw = 64 + 10 = 74 dB

UNWANTED SIGNAL1 % timeh1 = 600 mERP = 20 kW = 13 dBkWdistance = 200 kmEi = 29 + 13 = 42 dB

EXAMPLES

50 % 1 %

PROPAGATION PREDICTION

RECEIVED FIELD STRENGTH IS A FUNCTION OF:

• DISTANCE

• EFFECTIVE TX ANTENNA HEIGHT

• RADIATION PATTERN

• RX ANTENNA HEIGHT

• % LOCATION

• % TIME

• INTERPOLATION FOR INTERMEDIATE VALUES

• TYPE OF PATH: LAND, WARM SEA, COLD SEA

STATISTICS

ANALOGUE PLANNING

Gradual degradation

50 % location probability

99 % time probability

Fixed reception

10 m rx antenna height

DIGITAL PLANNING

Rapid degradation

90 - 99 % location probability

99 % time probability

Mobile reception

1.5 m rx antenna height

Propagation Prediction Curves50 % time wanted ; 1-10 % time unwanted

50 % location wanted and unwanted

Log-normal distribution

MINIMUM WANTED FS

⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔

V/mLocation Correction Factor ( 95% ) 9 dB

Min Median PFD (50% time 50% location) - 94.8 dBW/m2

Min Median Equivalent Field Strength 51 dB µµµµV/m

Frequency 500 MHz

Noise - 128.2 dBW

Allowance for Man Made Noise 0 dB

Minimum C/N required 14 dB

Feeder Loss 5 dB

Rx Antenna Gain 12 dB

Effective Antenna Aperture - 5.4 dBm2

Min Power Flux Density (PFD) at Rx - 103.8 dBW/m2

Min Equivalent Field Strength 42 dB µµµµ

MINIMUM MEDIAN FIELD STRENGTH FOR PLANNING

Frequency Band Band IV Minimum Equiv. Field Strength 42 dB µµµµV/m Antenna Height Gain (10 →→→→ 1.5 m) + 10 dB Corr. Factor (50 % →→→→ 99 % locations ) + 13 dB Minimum Median Field Strength 65 dB

‘MEDIAN’ means we can use 50 % location curves (i.e., corrections are already “built in”)

⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔⇔

MAIN TRANSMITTER PARAMETERS

• ERP

• site

• heff

• antenna pattern

• polarisation

MAIN TRANSMITTER PARAMETERS

EFFECTIVE ANTENNA HEIGHT: heff

antenna

Dist. from Tx0 km 3 km 15 km

average ground level

heff

MAIN TRANSMITTER PARAMETERS

e.r.p.: Power supplied to the antenna times thegain relative to a half-wave dipole.

GAINreference: half-wave dipole

½-wave dipole ½-wave dipolevertical plane horizontal plane

RELATIONSHIP: ERP vs. heff

d

For acceptable reception

- the wanted field strength must equal or exceed

Eref , and

- the unwanted field strength must not exceed

Eref - PR.

R Di

d

Eu

E

km

R

Eref

E

kmDi

Eref -PR

E

km

D = Di + Rwanted unwanted

RELATIONSHIP: ERP vs. heff

For acceptable reception

- wanted field strength must equal or exceed

Eref ,and

- the unwanted field strength must not exceed

Eref - PR.

R Di

D = Di + R

Example: R = 35, Di = 60 km

erp (dB kW)

heff (m)

Wanted (50 %) 35 km

(Eref = 58 dBµµµµV/m)

Interference (1 %)60 km

(Eref – PR = 48 dBµµµµV/m)

14 75 m ( 14 + 44 = ) 58 ( 14 + 41 = ) 55

0 300 ( 0 + 58 = ) 58 (0 + 48 = ) 48

Increase ���� 58 – 44 = 14 48 – 41 = 7

R

Eu

FS

km

50 % time

Di

Eu-PR

FS

km

1 % time

MAIN TRANSMITTER PARAMETERS

mobile/portable ���� vertical (near ground reflections)

���� horizontal (wooded absorption)

���� vertical (TV often horizontal, gives ∼∼∼∼ 16 dB protection to TV)

���� vertical (car antennas ∼∼∼∼ vertical)

Polarisation

MAIN TRANSMITTER PARAMETERS

MAXIMUM e.r.p.

ANTENNA PATTERNAttenuation with respect to MAX e.r.p.

½-wave dipole Tx antennahorizontal plane

15 dB

5 dB 3 dB

0 dB

PRINCIPLES OF FREQUENCY PLANNING

E

kmd

Eu R

For acceptable reception the wanted field strength must equal or exceed Eref

R Di

E

kmR

Eref

E

kmDi

Eref - PRD = Di + R

COVERAGE ?

EXAMPLE:• R = 40 km• ERP = 0 dB; 10 dB• Eref = 58 dB• ATT. = 0 dB; 3 dB

a) 55 + 0 - 0 = 55 < 58 PROBLEM !!

b) 55 + 10 - 3 = 62 ≥≥≥≥ 58 NO PROBLEM

E(R) + ERP - ATT. ≥≥≥≥ Eref

E

kmDi

Ei

1.0 kW 75 m

R

E

kmR

Ew

50 % time55

1.0 kW

75 m

INTERFERENCE ?

EXAMPLE:• Di = 150 km• ERP = 20 dB• PR = 10 dB• Eref = 58 dB• ATT. = 0 dB, 10 dB

a) 32 + 20 - 0 + 10 = 62 ≥≥≥≥ 58 PROBLEM!!

b) 32 + 20 - 10 + 10 = 52 < 58 NO PROBLEM

E(Di) + ERP - ATT. + PR < Eref

Di

100 kW 1200 m

E

kmR

EwE

kmDi

Ei

1 % time32

100 kW

1200 m