Iterative EM Based LDPC CDMA Receiver under Time Varying Interference

Abstract

The authors of this paper proposed an iterative expectation-maximization (EM) channel estimation based on a low-density parity-check (LDPC) code-division multiple access receiver in their previous work. The receiver algorithm could efficiently estimate both channel coefficients and noise power spectral density (PSD). However, their previous work considered only a single user channel environment, so they tested only for a constant noise PSD. In the current paper, we extend the single user to a more realistic multiuser environment for the testing of a time-varying interference plus noise PSD estimation. Also our proposed adaptive PSD estimation scheme will be compared with a conventional system in which a constant PSD is assumed. It will show that the proposed iterative EM scheme can provide accurate interference plus noise PSD estimates to the LDPC decoder.