Sensitivity degradation and antenna isolation analyses for a multi-operator global systems for mobile communication base transceiver stations
In other to mitigate challenges associated with the expansion of Global System for Mobile Communication (GSM) systems, infrastructure sharing have been proposed and adopted by some GSM operators. When infrastructure sharing is done, there is the possibility of degradation of quality of service due to Electromagnetic Compatibility issues, interference between operators, sensitivity degradation, increasing noise floor, antenna isolation requirement issue. This paper analyses the sensitivity degradation and the effects of spatial separation on antenna isolation requirement of Base Transceiver Station (BTS) receiver for a multi-operator mobile cellular systems. The data used were extracted from standards of organisation like European Telecommunications Standards Institute (ETSI) standards and others. Antenna dimension were obtained from physical observations of BTS site. By comparison with identified metrics in the standards, we verified that the number of operators that can share infrastructure is limited by the allowable sensitivity degradation. It was noted that an antenna isolation of 70dB can be achieved for GSM 900 band antennas and when GSM 1800 band antennas are used, 90dB antenna isolation is achievable greater than the minimum recommendation of 30dB.
Keywords: Antenna isolation, base station, BTS, GSM, infrastructure sharing, receiver sensitivity, sensitivity degradation