User Manual

RFCommissioning
42
Noise load on Radio Base Station
Thesystemwillinevitable addsomenoisetothereceiver.Properlysetupthenoisefigureinasystemlikethiswillbe
betterthan3dB.However,ifthegainissetuppoorly(notenoughgainintheremote,toomuchgaininthehead‐
end)itispossibletocr
eateaverybadnoisefigure.InordertoavoidthistheFiber‐DASCalculatorshouldbeusedto
calculatethenoisefigureofthesystemintheuplink.
Ifyo
uhavenotfamiliarizedyourselfwiththeFiber‐DASCalculatorthenIsuggestyoudosobeforemovingoninthis
manual.ThefiguresintheFiber‐DAScalculatorrelatestothe settingsofallstepsinthechain.Byusingthecalculator
youcanfigureoutthepropersettingsonceyoukno
wthefiberlossbetweentheRemoteUnitandtheMaster Unit.
Letusa
ssumeyourhavearrivedataNoiseFigureNFof3dBforthischain.Howeveryoursystemmaycontainmore
remotes,perhapsconnectedlikethis:
Figure 20

















!





 

Multiple RU Connection Diagram
Nowthenoiseloadcanbecalculatedbyaddingthenoisecontributionfromeachstepofthechain.Belowisan
exampleofnoisefiguresfromeachoftheremotes:
Table 46
Chain NF Gain Noise Load
RU1
RU2
RU3
RU4
SumofNoiseLoad
BaseStation
Fiber‐DA
SNoiseLoad
TotalNo
iseintoBTS
Desensitization
Noise Load
ThereisasheetintheFiber‐DAScalculatorthatletsyouaddyourfiguresandthatwillcalculateitforyou.
2.8 0.0 2.8
3.2 1.0 4.2
3.8 -2.0 1.8
2.6 -1.0 1.6
8.7
4.0
8.0
9.5
-5.5