  In this paper, we consider spatial-division multiple-access (SDMA) systems
with one base station with multiple antennae and a number of single antenna
mobiles under noisy limited CSIT feedback. We propose a robust noisy limited
feedback design for SDMA systems. The solution consists of a real-time robust
SDMA precoding, user selection and rate adaptation as well as an offline
feedback index assignment algorithm. The index assignment problem is cast into
a Traveling Sales Man problem (TSP). Based on the specific structure of the
feedback constellation and the precoder, we derive a low complex but
asymptotically optimal solution. Simulation results show that the proposed
framework has significant goodput gain compared to the traditional naive
designs under noisy limited feedback channel. Furthermore, we show that despite
the noisy feedback channel, the average SDMA system goodput grows with the
number of feedback bits in the interference limited regime while in noise
limited regime increases linearly with the number of transmit antenna and the
forward channel SNR.
