7.5 Noise Control
Noise control is important, especially in cascaded systems with multiple amplifiers and interconnecting cable. Gains have to be adjusted according to noise figures and losses of all the individual system components in order to optimize the performance of the whole system, end to end.
7.5.1 Noise Load on Base Stations
When an amplifier or an active DAS injects a noise power signal on the uplink port of the base station, it may potentially cause problems that will affect the performance of the base station. The main issue is that the injected noise will desensitize the receiver in the base station, limiting the performance of the uplink. This issue needs special attention in applications where an active DAS is connected to a macro cell, or if the base station is also serving a passive DAS. In these applications we need to insure that we configure the active part of the DAS with regards to gain and attenuation to minimize the effect of the uplink degradation. To select the correct UL attenuation in order to minimize the noise power, refer to Chapter 10. Furthermore, the raised noise floor has additional side effects for GSM and UMTS systems.
7.5.2 Noise and GSM Base Stations
Injected Noise Might give Interference Alarms
GSM base stations will monitor the noise level in idle mode time slots to estimate any potential interference problems from mobiles in traffic using the same frequency, in nearby or distant cells, PIM products, etc. This enables the base station to ...