Downlink impact of GSM900 on UMTS900 in co-sited case

This paper describes concretely the assessment of the GSM900 Base station transmission influence on UMTS900 Equipment receiver in coordinated deployment case according to some spectral masks in reception. This work is based on theoretical approaches which quantify the GSM interference level and shows the filter importance in coexistence issues between UMTS900 and GSM900. In order to minimize the GSM interference on UMTS system, the capacity loss and the coverage loss are evaluated and are analyzed according to the frequency separation between the two systems and the UMTS downlink network load. Thus, the feasibility of the carrier spacing depends strongly of quality of the reception filters and the acceptable capacity/coverage losses. Clearly according to our used filters, 2.6 MHz of separate carrier is possible but it could be risky to deploy UMTS900 below 2,6 MHz because the UMTS900 cell can be impacted by the existing GSM900 system.