Spreading and training in overloaded CDMA with low-complexity receivers
Satya Prakash Ponnaluri, T. Guess · 2005
This paper focusses on system design issues associated with unknown channel state information (CSI) in overloaded CDMA systems equipped with a multiuser linear minimum mean-squared error (MMSE) receiver. The received powers depend on the channel fading gains which are estimated using training sequences. Using the partial CSI obtained from training, we provide an algorithm for the design of spreading sequences in order to maximize the least signal to interference ratio (SIR) among all the users. The effect of training and estimation error on the performance of the receiver is analyzed with per-user ergodic capacity as a performance measure. Numerical results are provided to illustrate the superior performance of our system design when compared to designs based on generalized Welch-bound equality (WBE) sequences.