Analyzing interference between CDMA850 and WCDMA900

This paper presents the interference study between CDMA850 and WCDMA900 in Malaysia. Both Frequency Division Duplex (FDD) systems are adjacent to one another spectrally without definite guard band and their coexistence becomes an issue when they are on reverse duplex. The WCDMA900 sites have claimed interference from CDMA850 Base Station transmitter. An affected site in Klang Valley is chosen to present the real case of interference between the two systems. A scheduled field test involving the closing of CDMA850 carrier is performed to investigate the main cause of interference. It is established that receiver blocking and/or receive intermodulation contributes the most to the WCDMA900 uplink interference for the selected site. A deterministic approach is then used to further analyze the minimum physical separation required to avoid receiver blocking and receive intermodulation. Additional filtering at the victim side is then recommended among the mitigation techniques to minimize the interference.