User Manual

DELTANODE FIBER DAS MANUAL
©DeltaNode Solutions 2012
31
Revision 12-03
Note: This is different from Friis
formula where the noise sources are
cascaded, here each noise
cointribution are just added in linear
and
then converted back to
decibels.
3
4,0
-5
-1
Total
4,1
Similar to a BTS own NF
This is similar to the BTS own noise figure which generally is 2-4 dB
depending on the system. This kind of desensitization then becomes a
tradeoff between coverage area in the uplink and the noise load on
the base station.
Adding noise from each parallel chain is then done through the
formula:


= 10 10 10


+ 10


+ + 10






NF is the noise figure for each chain
NL is the total noise load
G is the gain of the chain in total
When the sensitivity has been calculated it is time to make a proper link budget and find out if the
system will cover the expected areas.
Here are some examples on link budget calculations where you can insert the noise figure of the system.
These calculations are also included on the DAS calculator tool and link budgets for other systems should
also be included. CDMA can be calculated similarly to WCDMA if the gross data rates etc are corrected.
Example of GSM link budget
Linkbudget GSM with Fiber DAS
DOWNLINK
Output power DAS remote unit
30,0
dBm
Number of carriers
2,0
pcs
This gives the per carrier power
Power per carrier
27,0
dBm
Splitloss from RU port to last antenna
6,0
dB
Cable losses
4,0
dB
DAS antenna gain
3,0
dB
EIRP
20,0
dBm
MS Noise floor
-121,0
dB
MS NF
3,0
dB
MS C/I
12,0
dB
MS Fading margin
6,0
dB
10 dB for vehicle movements
Penetration loss
0,0
dB
Used for in vehicle (10 dB for car)
Antenna gain MS
1,0
dB
Body loss MS
5,0
dB
Required signal level
-96,0
dBm
Design target
Allowed path loss from antenna to MS
116,0
dB
Radiating cable coupling loss C95
70,0
dB
Only when using radiating cable
Loss per 100 m
4,0
dB
Only when using radiating cable
Maximum length of radiating cable
1149,5
m
UPLINK
Spectral noise floor of BTS
-121,0
dBm
Noise figure BTS
3,0
dB
C/I for BTS
9,0
dB
BTS original noise floor
-118,0
dBm
BTS original sensitivity
-109,0
dBm
Fading margin
6,0
dB