User Manual

BRITECELL System Manual MN010-04 June 2003 Page 45 of 78
The company has a policy of continuous product development and improvement and we therefore
reserve the right to vary any information quoted without prior notice.
33.2. Uplink operation
The RF signal coming from the mobile through the TFA and TFL in the uplink
direction may not be an optimal level. When this is the case, the uplink attenuator
is used to prevent the BTS from being over driven.
34. Installation and cabling
34.1. TPR housing
The TFL-BSI is a modular plug-in card designed to be put in a 6 HE sub-rack (TPR
family).
The TFL-BSI interfaces with the BTS transmitter and receiver through N-female
connectors and with Britecell with SMA-female connectors.
The connection with the BTS may be direct, if the BTS’s transmitter and receiver
are separated, or through a circulator or a common path RF combiner (please refer
also to THYB section).
When the system is air interfaced through a repeater a common path RF combiner
is required in order to separate the uplink and downlink path.
The connection between TFL-BSI and Local Units may be direct or through a
combiner stage (please refer to TLC section) depending on the system’s
configuration.
35. Calculation of attenuation setting
35.1. Downlink
Calculation of Downlink TFL-BSI setting is made in order to supply Britecell Local
Unit with correct DL input power.
MaxBCDLNetbCCpouplerDirInputPOIDLBSI
PILILPA
__.om._@_
)(]dB[
−−−=
where:
P
@POI_Input
[dBm/c]= RF power level per carrier at POI input:
IL
Dir.Coupler
[dB]= Directional coupler insertion loss (if present);
IL
Comb.Net
. [dB]= Combining Network insertion loss;
P
DL_BC_Max
[dBm/c]= Max input power per carrier at Local Unit input.
35.2. Uplink
Calculation of Uplink TFL-BSI setting is made to meet BTS uplink blocking
requirements.
SMPILILPA
BlockingBTSNetbCCpouplerDirBlockingULLUblkULBSI
+−+−=
@.om.@___
)]([]dB[
where:
P
LU_UL@Blocking
[dBm]= Local Unit output power when Remote Unit is at blocking
level (3 dB C/N degradation);
P
BTS@Blocking
[dBm]= BTS receiver blocking level;
SM = Safe margin (typically 3 dB).