Frequency Assignment

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Frequency Assignment

• WRAP efficiently supports assignment of frequencies and polarisations to stations and networks

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• All services

• Manual assignment

• Automatic assignment

• Simplex

• Duplex

• Consider or exclude existing assignments

• Ordinary or orthogonal polarisation

Assignment margin

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D e f i n e d a s t h e m i n i m u m o f t h e f o l l o w i n g t h r e e e x p r e s s i o n s :

S

I

S

IP M

c a l c u l a t e d r e q u i r e d

( 1 )

f o r t h e m a r k e d s t a t i o n a n d P M i s a u s e r d e f i n e d p r o t e c t i o n m a r g i n

PMSS ysensitivitca lcula ted ( 2 )

f o r t h e m a r k e d s t a t i o n a n d P M i s a u s e r d e f i n e d p r o t e c t i o n m a r g i n

m i nS

I

S

IP M

c a l c u l a t e d r e q u i r e d

( 3 )

f o r a l l s t a t i o n s w h e r e I i s t h e i n t e r f e r e n c e p o w e r r a d i a t e d f r o m t h e m a r k e d s t a t i o n a n d P M i s a u s e r d e f i n e d p r o t e c t i o n m a r g i n .

In some cases a fourth expression is also used. This expression handles the absolute level of the interference signal

calculatedthreshold II (4)

where Ithreshold is a user defined maximum level of the interference signal and Icalculated is the interference power on adjacent channels.

Links

• Links– Both the stations forming the link are tested

for• received signal-to-interference• received signal• transmitted interference

• Digital links– The expressions are modified according to

• S/I => max (T/I)• S=> max (T)

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Area coverage

• For area coverage services 8 interference cases are tested:– Base 1 transmitter to base 2 mobile– Base 2 mobile to base 1 receiver– Base 2 transmitter to base 1 mobile– Base 1 mobile to base 2 receiver– Base 1 transmitter to base 2 receiver– Base 2 transmitter to base 1 receiver– Base 1 mobile to base 2 mobile– Base 2 mobile to base 1 mobile

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Area coverage

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Area coverage services

Base 1 Base 2

Mobile 1 Mobile 2

RX level = Maximum (Sensitivity, Level at service area limit)

Automatic assignmentGenetic algorithm

• Optimises the assignment based on– Minimum bandwidth: Smallest separation between

highest and lowest frequency– Few frequencies: Minimum number of frequencies in the

assignment– Interference: Minimum interference– Prioritised interference: Minimum interference on

prioritised frequencies– Collocation interference: Minimum interference due to

harmonics, intermodulation etc

• The different criteria are weighted• This method gives a random assignment.

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Automatic assignmentSequential algorithm

• Sort stations: – Smallest last– Generalised smallest last– Random

• Assignment:– Sequential as priority list– Station with smallest number of available

frequencies• Assign frequencies:

– First acceptable frequency from either band edge

– First acceptable that has been assigned to most stations

• This method gives a deterministic assignment.

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Automatic assignment settings

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Sequential method Genetic method

Manual assignment

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• The negative of the assignment margin is presented in a graphical display.– Red: Assignment margin negative, i.e. the

calculated signal-to-interference ratio is too small, or the wanted signal is too small or the station interferes with another station

– Blue: Already used by the station to be assigned

– Yellow: Free to assign

Network assignment

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• All stations in networks are assumed to communicate with each other

• Stations within a network do not interfere with each other (only one transmission at a time)

• Display of margin diagram either– Network orientated: Situation for the worst link in the

network– Station orientated: Situation for each marked station.

• Main frequency and Reserve frequency can be assigned. The minimum separation between main/reserve can be defined.

• Genetic algorithm with minimum interference strategy, or the sequential algorithm can be used

Polarisation assignment

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• Wanted and interfering signal levels are calculated both for the ordinary and the orthogonal polarisation

• Cross-polarisation discrimination of antennas and propagation medium are considered

• Priorities:– First: Attempt to assign orthogonal polarisation on same

frequency– Second: Attempt assign same polarisation on adjacent

frequency– Third: Attempt to assign orthogonal polarisation on adjacent

frequency.

• Polarisation properties of selected allotment are considered

Frequency allotment

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• Frequencies to be used by the assignment tool are picked from a frequency allotment (channelling plan)

• The allotment is defined by – Frequencies in the list– Duplex distance (if applicable)– Polarisation of frequencies

• Allotments are prepared in the Allotment tool.