User's Manual

characterisation already exists and that the BTS is balanced from a link budget point
of view. If this is the case, skip step 1 in General link budget characterisation, step by
step below and continue to step 2 or 3.
General link budget characterisation, step by step
1. Measure site link balance
2. Measure site feeder loss
3. Calculate theoretical maximum TTPA sensitivity gain
4. Add link balance and sensitivity gain to decide TTPA Tx gain
5. Set TTPA Tx and Rx gain
6. Measure site link balance to verify gain settings
1. To characterise the actual link budget in a cell, specific equipment is needed. This
can be provided by the infrastructure supplier or the net planner. In general, a vehicle
mounted channel monitor is needed, together with the BTS channel monitor.
The quality can be characterised by many different parameters and the choice should
not affect the results. Below, RBER (Residual Bit Error Rate) have been used. A
common quality setting is that the RBER should be <2%.
Place a call from a place well within the area covered by the BTS and slowly move
towards the cell border while monitoring the call quality at both terminal and BTS.
When RBER=2% for either the down link (monitored in the vehicle) or the up link
(monitored in the BTS), stop the vehicle.
If the up link is limiting, i.e. RBER=2% is monitored in the BTS:
The terminal should now be transmitting at its full power. Note the output power of
the BTS, P
0
. Decrease the BTS output power step by step until RBER=2% is
monitored in the vehicle. Note the output power of the BTS, P
1
. The unbalance is
given by:
P
1
- P
0
= P
ub
(P
ub
should be <0)
If the down link is limiting, i.e. RBER=2% is monitored in the vehicle:
The BTS should now be transmitting at its full power. Note the output power of the
terminal, P
0
. Decrease the terminal output power step by step until RBER=2% is
monitored in the BTS. Note the output power of the terminal, P
1
. The unbalance is
given by:
P
0
- P
1
= P
ub
(P
ub
should be >0)
2. Meassure the feeder length and use the manufacturers typical loss per meter data to
decide the site feeder loss, L (any other method will do as long as a value for the
feeder loss is present….).
3. The LNA in the TTPA will significantly improve the BTS sensitivity. How much is
easily calculated by using Friis’ formula. Input parameters are, apart from TTPA Rx
gain (G
Rx
) and noise figure (NF
Rx
), site feeder loss, L, and BTS transceiver input
noise figure, NF
T
. The total system noise figure before and after deployment of the