On the Limitation of Generalized Welch Bound Equality Signals under Linear MMSE Detection

摘要

This paper characterizes the performancernlimitation of the well-acclaimed generalized Welchboundrnequality (WBE) signals under linear minimumrnmean-squared error (MMSE) detection. We prove thatrnwhen users in an overloaded finite-size CDMA systemrnare allocated such signals, the bit error rate (BER) of atrnleast one user "floors". If in addition all users are receivedrnwith equal energy, we prove that the BER of everyrnuser "floors". Numerical examples illustrate that thernerror floor is typically high, even for mildly overloadedrnsystems.