Diversity Multiplexing Tradeoff in Multiple Antenna Multiple Access Channels with Partial CSIT

We derive a lower bound on the diversity-multiplexing tradeoff for multiple antenna multiple access channels using temporal power control (PC). We quantify the substantial improvements in diversity gains with finite rate feedback over schemes that use no feedback, even when users have asymmetric diversity and rate requirements. For small multiplexing gains, all users in the MAC achieve their single user performance as if each receives B distinct bits of feedback. We also show that for a SISO MAC with finite rate feedback, the diversity orders with PC and with opportunistic user selection are the same at all multiplexing gains.