User Manual

MBF, Multi Band Repeater

PRODUCT DESCRIPTION AND USER'S MANUAL

It must also be kept in mind that the OMU might have separated input/output ports for each band (UL/DL)

while the interface with the BTS may well be duplex. In that case some duplexing network must be provided

to allow these to be brought together. If there is more than one operator’s BTS per band the loss of any

combining network and any equipment room cabling also becomes part of the overall attenuation required to

reach the correct interface level in each frequency band.

The illustration on the next page shows a more complicated arrangement where the same three BTSs feed

multiple MBF repeaters (up to 6 is possible using the standard splitter card which fits the OMU rack). In this

case an OMU per frequency band is shown. The internal splitter has an insertion loss of 14 or 16dB

depending on frequency band. This loss is again a contribution to the overall attenuation which must be

provided between BTS and the input ports of the UFO-M for the correct operational levels to be achieved.

The interface levels must be modified to maintain the same composite power if a greater number of carriers is

to be applied from the BTS.

The DL POI / OMU Adjustment must be made considering the fully loaded condition – e.g. a BTS capacity

of 8 carriers must include a back off of 6dB compared to the 2 carrier level and -11dBm/carrier is then the

correct UFO-M drive level for GSM 900. The same rule for back off applies in other bands.

Note that a UMTS BTS at idle (no traffic) will be radiating only a pilot – approx -10dB compared to the

average power when it is in traffic. See also section about UMTS Signal Measurement below.

5.1.4 Repeater Downlink Optical Link Adjustment (OLA)

The optical link between the UFO-M of the OMU and the UFO-S in the repeater is equipped with a calibrated

pilot tone transmitter/receiver which enables compensation for the loss of the optical fibre plant between

them.

The OLA procedure requires a computer running Axell RMC software and an RS232 connection to the LMT

Port of the repeater controller.

Start the RMC and login to the repeater as described in the appropriate section of the handbook. Click on the

Actions tab on top of the RMC screen. A drop down list will appear where a command will be found to

execute the optical link adjustment for each UFO-S module that is fitted to the repeater. Click the command

for the desired optical link and following a short delay (2-3 secs) an information screen will be shown

describing the result of the automatic setup process.

This procedure is described in the OMU Manual section 4.10.

5.1.5 Downlink Repeater Gain Adjustment

When the DL POI levels and the repeater optical links have both been set up as described in the foregoing the

MBF repeater set at maximum gain should produce a composite signal level at the output connector of

+37dBm for GSM900 and 1800 and +39dBm for UMTS.

The RMC provides sub screens for each band where the downlink power from UFO-S optical receiver /input

to the DL radio board and the composite output power level from the MCPA can be viewed.

The power amplifier for each frequency band can be enabled /disabled and the preset DL attenuation in the

radio board for each band can be adjusted. A saturation status indicator (red/green) shows whether the radio

board ALC is in operation. This indicator should be green. A red indication indicates overdrive the cause of

which should be investigated and rectified.

In each band the DL output power per carrier should be measured using a spectrum analyzer. Allowing for

the maximum DL carrier quantity in each band the composite level per band under full loading should be

calculated to ensure it does not exceed the rated maximum otherwise ALC will be in operation when traffic

levels are high. See also section about UMTS Signal Measurement below.