A. Introduction
Code Division Multiple Access (CDMA) is an alternative to frequency and time division multiple access (FDMA and TDMA). CDMA has become the standard for the Universal Mobile Telecommunication Systems (UMTS) and American cellular systems [1]. Also, optical CDMA systems have become an alternative multiple access for fiber optics and optical wireless systems [2]–[4]. The reasons, to name a few, are its simplicity, high loading factor,
The number of users divided by the spreading gain .
and soft hand-off. In this paper, we will discuss some open issues related to uncoded synchronous CDMA systems of any size with finite input alphabet and matrix elements from arbitrary given alphabet (finite or infinite). The channel is modeled with real/complex additive noise with arbitrary distribution.