User Manual

DELTANODE FIBER DAS MANUAL
©DeltaNode Solutions 2012
42
Revision 12-03
to reflect this. In general we should lower our so that we desensitize the BTS only about 3 dB. This value
is a good compromise and similar to adding a second antenna to the same receiver port (which is kind of
what we are doing with the Fiber-DAS).
Here are the new values:
Chain NF Gain Noise Load
RU 1 2,8 -5,0 -2,2
RU 2 3,2 -5,0 -1,8
RU 3 3,8 -5,0 -1,2
RU 4 2,6 -5,0 -2,4
4,1
Base station 4,0
Fiber-DAS noise load 4,1
Total noise into BTS 7,1
Desensitization -3,1
Sum of noise load
As you can see we should set the system up with a net gain of about -5 dB. Going back to the settings we
had before which was:
System part Gain [dB] Accumulated [dB]
Remote Unit
40 40
Fiber -10 30
FOI Gain 20 50
POI Loss
-35 15
BIU Gain 0 15
Coupler loss -15 0
We only need to change the BIU setting using the attenuators in the BIU to lower the gain with 5 dB. This
will accomplish what we need to do and the uplink should then be commissioned.
6.1.2 Practical approach
Now that we know what we should have we can easily set the system up. You need a spectrum analyzer
to do this and it is easiest to connect it into the BIU port. Remember that when you measure here, the
signal should also go through the BTS coupler before it reaches the base station receiver port. Therefore
you should expect to read a value that is
Your expected gain + the loss in your coupler
If you want a net gain of -5 dB and you have a 15 dB coupler, you should read a net gain of +10 on the
BIU port. This is now what we are going to use in the following example.