UMTS900 Co-Existence with GSM900

UMTS was initially deployed in Europe and in Asia using new spectrum at around 2 GHz. The deployment at 2 GHz frequency requires fairly high site density making it challenging to match existing GSM900 coverage with the same sites. Now also UMTS can take benefit of the better signal propagation at 900 MHz since 3GPP has defined UMTS specifications for 900 MHz and UMTS900 products are entering the market during 2007. The target of UMTS900 is to bring UMTS coverage to new areas with less base station sites and to improve the indoor coverage in the existing UMTS coverage area. This paper shows that UMTS900 can reduce the required number of base station sites by 60% and improve the indoor data rates by more than 50% compared to UMTS2100. When UMTS900 is deployed with co-sited GSM900, the required spectrum for UMTS carrier is 4.2 MHz or equivalently 21 GSM carriers. This 4.2 MHz spectrum corresponds to the carrier spacing of 2.2 MHz between UMTS carrier and closest GSM carrier. The feasibility of 2.2-MHz carrier spacing is verified by GSM power level measurements in a live network combined with the commercial UMTS base station blocking measurements.