User's Manual

Initial FlexWave Prism System Setup

FlexWave Prism Element Management System 7.1 User Manual Page 85

CONFIGURE HOST FORWARD GAIN

NOTE: Digital power measurements are inaccurate when ALC is active.

Follow these steps to set the Forward Gain value for the Host DART.

1 Determine what the Host DART Forward Gain should be. Use a signal generator

and spectrum analyzer to measure the uplink attenuation from the Host to the

BTS, and the FWD power at the Host from the BTS to determine unloaded

power level.

The Host DART expects signal levels from -25 to +5 dBm. If the fully loaded signal

is +5 dBm, then the DART forward gain should be set to 0 dB, if the fully loaded

signal is -25 dBm, then the DART Forward Gain should be set to 31 dB. The

equation is:

DART Forward Gain = 5 - fully Loaded Base Station Signal

CAUTION! If you are setting up the system when no calls are going through, you must allow

headroom for a fully loaded forward path. For CDMA protocols, the difference from

unloaded to fully loaded is typically 8dB, so if the unloaded signal is -15dBm, then the

fully loaded input would be -7 dBm and the Host Forward Gain should be set to 5-(-7) = 12

dB.



The same rules applies for GSM carriers, except that the unloaded to loaded is

determined by the equation 10*log10(# RF Channels). So if there are 4 GSM RF Channels,

then the loaded forward path is 6 dB above unloaded.



If sufficient headroom is not present, then the LPA can be over-powered causing a Loss

Of Service.

CAUTION! When configured correctly, the Host DART Forward input can handle peaks of 14dB above

the BTS signal level. For example, if the fully loaded CDMA carrier is -25dBm, then peaks

up to -11 dBm can be handled (CDMA peak to average is typically 10-12 dB). If the peaks

exceed the 14 dB of headroom, then Automatic Level Control (ALC) will occur to prevent

over-driving the A/D Converter.

NOTE: In the EMS GUI, the reverse path gain range for Classic DARTs is 5 to 36 dB, which

indicates actual reverse path system gain. If you set this gain through the SNMP SET

commands, then the gain range is 0 to 31 dB, which maps to the actual GUI/system

reverse path gain range of 5 to 36 dB.