User's Manual

TTPA will be:
With no TTPA:
NF
BTS1
= L + NF
T
With TTPA:
NF
BTS2
= NF
Rx
+ (L - 1)/G
Rx
+ (NF
T
-1)L/G
Rx
Hence, the sensitivity improvement will be NF
BTS1
- NF
BTS2
= S
G
.
The value of S
G
can also be calculated using the free Allgon LinkPlanner tool.
4. Now it is possible to calculate the gain setting of the TTPA Tx branch, G
PA
to
maximise cell coverage:
P
ub
+ S
G
= G
Tx
Please note that the two gain values are valid only if the original BTS output power
setting remains.
It is possible that the receiver sensitivity improvement is so large that there is not
enough Tx gain available to balance the link budget. Such a scenario is possible on
sites where the feeder loss is extremely high. In such cases the sensitivity gain, S
G
,
must be reduced to balance the maximum value of the TTPA Tx gain, G
Tx,max
and the
link balance value P
ub:
S
G
= G
Tx,max
- P
ub
S
G
is reduced by decreasing the value of the TTPA Rx gain, G
Rx
, in Friis’ formula.
5. Set the TTPA values of G
Tx
and G
Rx
through the APDU user interface.
6. To verify the new cell coverage and link balance, repeat step 1 above. If done
correctly the value of P
ub
should read very close to 0.
Appendix 2: System Configuration Examples
Configuration I
One duplexed antenna and one diversity receive antenna with duplex filter in BTS.
Power fed via single port Current Injectors.