Broadcast

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Broadcast

• Calculations for – FM sound broadcasting– Analogue television– T-DAB digital sound– DVB-T, ISDB-T, ATSC digital television

• Performs interference calculations and frequency assignment

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Broadcast

• Based on international recommendations:– ITU BS.412-9 Planning standards for terrestrial FM

sound broadcasting at VHF– ITU BT.655-6 Radio-frequency protection ratios for AM

vestigial side band terrestrial television systems interfered with by unwanted analogue vision signals and their associated sound signals

– EBU BPN 003, Technical bases for T-DAB services network planning and compatibility with existing broadcasting services

– ITU-R BT.1368-3, Planning criteria for digital terrestrial television services in the VHF/UHF bands

– and several others…

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Basic concepts (1)• Important parameters:

– Protection ratio, PR [dB]The required difference in dB between the level of the wanted signal and the level of the interfering signal to achieve the required quality of reception

– Usable field strength, Eu [dBV/m]The required field strength of a wanted signal to achieve the required quality of reception, considering multiple interfering signals and their corresponding protection ratios

– Nuisance field strength, En [dBV/m]The equivalent required field strength of a wanted signal to achieve the required quality of reception, considering a single interfering signal and its corresponding protection ratio

– Interferer field strength, Ei [dBV/m]The field strength of a single interfering signal

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Basic concepts (2)

• Nuisance field strength, En [dBV/m]:

En = Ei + PR

• Usable field strength, Eu [dBV/m]:

Eu = Sum [En]

• Selectable summation methods (“Sum” above):

– Power-sum

– Log-normal

– k-LNM (Log-normal with a coefficient k)

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Settings

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Interference evaluationFM sound, analogue TV

• Protection ratios for FM Sound– Transmitter spectrum properties and receiver selectivity– Protection at transmitter frequency +/- 10.7 MHz (local

oscillator frequency of receivers)

• Protection ratios for analogue TV– Transmitter spectrum properties and receiver selectivity– Protection at transmitter frequency +/- receiver

intermediate frequency (+ or - as applicable for system type)

– Protection at transmitter frequency +/- 2 x receiver IF (image, + or - as applicable for system type)

– Non-controlled, Non-precision, Precision offset

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Interference evaluationT-DAB, digital TV

• Protection ratios for T-DAB– Transmitter spectrum properties and receiver selectivity

• Protection ratios for digital TV– Transmitter spectrum properties and receiver selectivity

• Constructive signal summation in single-frequency networks (SFN) is considered for the wanted signal

• Interference calculations within SFN’s consider guard times, useful signal duration and propagation delays

• Receiver synchronises to strongest signal in SFN

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System types

• FM Sound– Mono, stereo– Frequency deviation: ±50 kHz, ±75 kHz

• Analogue television– Video: B, G, M, D, D1, H, I, K, K1, L– Colour: Monochrome, PAL, SECAM, NTSC– Sound: Mono, Analogue multisound, Digital multisound– Offset: Non-controlled, Non-precision, Precision

• T-DAB• Digital television

– DVB-T– ISDB-T– ATSC

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Test points

• Test points are placed automatically at– The edge of the service area in the direction of the interferer,

as close to the interfering station as possible– For no service area: The point where the wanted transmitter

generates the minimum usable field strength– The minimum distance between a test point and interfering

transmitters can be defined

• Test points can be placed manually in the map• Parameters evaluated at each test point:

– Individual nuisance field from each interferer, En = Ei + PR

– Usable field strength, Eu = Sum [En]

– Wanted signal field strength, Ew

– Margin, M = Ew – Eu

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Statistical considerations• Propagation models should be used with

settings to give the median location statistics value and the desired time statistics value

• Median values are presented for– Nuisance field, En

– Usable field strength, Eu

– Wanted signal field strength, Ew

• The Margin, M, value considers the selected probability of interference– M = Ew – Eu

– M has a log-normal distribution with parameters• Median: M50% = Ew50% - Eu50%

• Standard deviation, S: S2 = (Sw)2 + (Su)2

– A frequency is assignable if M 0 for selected probability

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Test points (automatic)

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Interference result

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Nuisance field, Margin in FQA

• Worst interfering stationThe largest nuisance field against the marked station among all contributing interferers in the test point with the lowest margin, the station generating this value and the margin at that test point.

• Worst interfered stationThe largest nuisance field from the marked station at that of its test points with the lowest margin, the station being subjected to this field and the margin at that test point.

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Nuisance field, Margin in FQA(TV frequency offset)

• Nuisance fields, margins and the margin diagram in the Frequency Assignment tab show the current situation (existing assignments) for the frequencies indicated as “Used”.

• Other frequencies show the most favourable offset assignment in the non-precision and precision offset cases.

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Frequency assignment (TV)

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Example of results for non-precision offset (TV)