Interference characteristics analysis of mixed services in wideband CDMA UMTS

In this paper, we analyse the MAI (multiple access interference) characteristics of mixed services (voice, circuit data, and packet data) in UMTS FDD-WCDMA mode. According to the various traffic and the system parameters [ETSI], the combinations of service (voice only, voice/circuit data, voice/packet data, and voice/circuit/packet data) represent different MAI characteristics. Their long-term (average) and short-term (instantaneous) MAI variation show different characteristics as well. In this paper, we compare the MAI of mixed services in relation to the Gaussian random variable. When we use the voice and packet data service, the MAI is not the same as the Gaussian random variable but as the packet users increase, the MAI distribution approaches that of Gaussian. In addition, the voice and packet data service represents a short-term MAI variation. As the UMTS WCDMA is interference limited (Gilhousen, et al. 1991), accurate MAI evaluation for each service becomes a critical factor for the system dimensioning and capacity evaluation.