User's Manual

Uniwave

User Manual

The desired maximum noise level at the BTS is known from the MNO (3G typically -104 dBm, 4G

typically -114 dBm)

Therefore, a simple calculation can be made calculate the POI attenuation needed to match the DAS

UL noise level to required level at the BTS

Noise power (noise floor) = KTB + NF + gain of the DAS - POI attenuation

Where

K= Boltzmann’s constant= 1.380 x 10

-23

J/K

T = temperature in Kelvin

B = bandwidth in Hz

“POI Attenuation” is the total loss in the POI including cables to the BTS and all attenuators

and other losses

e.g. a WCDMA channel is 3.88 MHz, therefore the thermal noise in the channel is -108.1 dBm

27.5 dB noise from 1-8-64 system,

25 dB system gain

-108.1+27.5+25 = -55.6 dBm

50 dB POI UL attenuation

-55.6 - 50 = -105.6 dBm

The uplink gain of the DAS is internally configured to mirror the downlink values, modified by the UL/DL

balance setting on the Hub GUI. Under normal circumstances, selecting a lower gain than the maximum

of 25dB will simply add more attenuation into the service module. This has no impact on the noise

figure, and is equivalent to adding attenuation in the POI. Noise figure is impacted, however, if the RU

applies AGC protection due to an excessive interferer. It may be necessary to re-site the Rx antenna if

there are persistent high measured background RF levels.

The UL noise floor from the Active DAS could also be measured at the POI input using the correct

system bandwidth and the UL POI attenuation calculated from that value.

Comparing calculated Noise floor against that measured will also confirm that no other issues are

causing a higher than expect noise floor output from the DAS

Calculated using Empirical Formula: NF= 14 + 10 x LOG (SQRT(qty of RUs)) + 10 x LOG (SQRT(qty of SHs))

Data Table of ORU/SH combinations number of ORU/SH --->

Noise Figure 1 2 3 4 5 6 7 8

number of SH ---> 1 14.0 15.5 16.4 17.0 17.5 17.9 18.2 18.5

2 17.0 18.5 19.4 20.0 20.5 20.9 21.2 21.5

3 18.8 20.3 21.2 21.8 22.3 22.7 23.0 23.3

4 20.0 21.5 22.4 23.0 23.5 23.9 24.2 24.5

5 21.0 22.5 23.4 24.0 24.5 24.9 25.2 25.5

6 21.8 23.3 24.2 24.8 25.3 25.7 26.0 26.3

7 22.5 24.0 24.8 25.5 25.9 26.3 26.7 27.0

8 23.0 24.5 25.4 26.0 26.5 26.9 27.3 27.5