Post on 30-Dec-2015
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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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.