The paper discusses the performance of a MIMO-extended UMTS-FDD downlink with a 2x2 and a 4x4 antenna configuration. An analytical expression for the average signal to interference ratio (SIR) of a space-time (ST) RAKE receiver in an interference dominated environment is derived. Simulations are used to assess the BER performance with the number of concurrent users as a parameter. The results are compared to a single antenna link with equivalent data rate. In addition to that, a linear zero forcing (ZF) and an MMSE MIMO equalizer receiver is evaluated and compared to the ST-RAKE. It is shown that both methods can successfully mitigate the significant performance Imitation due to self interference (SI) and multiple access interference (MAI).