Coding and Modulation for Code-Division Multiple Accessing*
James L. Massey · 1999
: It is argued that the "rightful purpose" of a CDMA modulation system is to create a good channel for the coding system. This viewpoint leads to a precise formulation of energy efficiency and a novel formulation of bandwidth occupancy as normalized Shannon bandwidth. Various modulation/coding architectures are formulated and compared. It is shown that it is possible to design systems in such a way that the burden of separating and detecting the users' information sequences is divided between the demodulator and the decoders with resulting reduced complexity but with no penalty in either energy efficiency or bandwidth occupancy. 1 Introduction Before one begins to study modulation systems and coding systems in detail for code-division multiple accessing (or for any other kind of communications for that matter), it is well to reflect on what the purposes of these two systems are. As self-evident as this admonition may seem, we must remark that our experience shows that it is heeded mor...