Frequency interference analysis between UMTS and CDMA 2000 in 2.1 GHz frequency band

As a natural limited resources, the radio frequency spectrum should be managed and used as efficiently as possible. The Government as regulator has a responsibility to manage and regulate the spectrum to prevent interference. One example of the many problems in Indonesia that must be solved is the spectrum in 2.1 MHz frequency band for 3G services. The CDMA 2000 and UMTS system occupy adjacent band and that very potential to cause interference each other. The CDMA 2000 downlink channel which is separated by only 3.125 MHz guard band, have the potential to interfere the UMTS uplink channel. It is especially in the last channel with a center frequency of 1977.5 MHz. In this paper we evaluate an interference that occur between the two system by computer simulation and experimentally measurement. We propose three methods to cope with this problem, namely spectrum segmentation with sufficient separation band, geographical separation, and additional filters on the BTS. Antenna spatial isolation method is also used so that both systems can operate co-location in which the level of the interference is acceptable. With the arrangement of the antenna vertically by 1,1 meters separation, the additional attenuation of 15.2 dB can be obtained to reduce interference.