User Manual

DELTANODE FIBER DAS MANUAL
©DeltaNode Solutions 2012
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Revision 12-03
The above illustration shows two BIU cards interfacing with two Radio Base Stations. In this case they
could be a 900 GSM station and one 1800 GSM station as an example. It could in fact be any combination
of service and frequency band such as LTE-900 or WCDMA 850.
Each BIU has a combined UL/DL port towards the base station and on the other side there are separate
UL/DL ports. The BIU has an uplink amplifier and a downlink attenuator that can be set. The signals are
then connected to the POI:s 4 coupling fields to it’s common ports. The signal is then split onto 8 ports in
the downlink and combined from 8 ports in the uplink. From the POI there are then patches to each FOI
card in the frame (8 in this illustration per uplink and downlink) and the 900 and 1800 signal are kept
separate until the FOI.
It is not necessary to keep them separated; they could be combined for a common uplink and downlink.
However, doing so means that you have fewer options in adjusting the signal levels with the gain block
and attenuators, in each RF chain.
3.4 Multiple operators
The same way as multiple bands and services can be connected to the Master Unit it is also possible to
connect several operators. In fact this is one of the key strengths of a Fiber-DAS system because it is
access technology agnostic. This means that it is possible within the same band to mix different access
technologies – if care is taken to avoid problems when mixing GSM and CDMA in the same system
because of the very slow and unsophisticated power regulation in the GSM uplink.
When designing such a system, care should be taken to place the antennas to avoid any users getting too
close and causing the Remote Unit to go into limit mode.
3.4.1 Base station interface
It is recommended that each operator operates their own BIU because otherwise the settings of the BIU
may affect more than one system or service. This way depending on the settings of the individual Base
Station the BIU can be adapted properly to get the most out of the system.
3.4.2 Remote Unit
Multiple operators can share one remote unit. Doing so means that consideration should be given to the
number of carriers from each operator, so that they can fulfill their respective link budgets. If the
operators have a large number of carriers, such as for some GSM operators who easily have 6, 8 even 12
carriers it would be better to split them up on separate amplifiers in the Remote Unit or even separate
units altogether.
3.4.3 FOI
The FOI can be shared among the operators. It is recommended to see to that the downlink signal levels
are similar so that they share the available bandwidth of the laser properly. Similarly in the uplink
3.4.4 POI
When combining multiple operators it is often useful to combine all the operators’ uplinks and split all
the downlinks on a per-band basis. This means that if you have more than one FOI in the system you
should likely need to use another one plus a hybrid combiner/splitter.