Binary signature sets for increased user capacity on the downlink of CDMA systems

We compare the maximum achievable common Signal to Interference and Noise Ratio (SINR) target level kappa(max) in the downlink of various Code Division Multiple Access (CDMA) systems with binary sequence sets. We derive an upper bound to kappa(max) for binary systems with symbol-aligned users, and we compare this upper bound to the value of kappa(max) for Quasi-Orthogonal Sequences (QOS), Grassmannian signatures and binary Pados-Karystinos; signatures. Secondly, we turn our attention to systems where the (binary) signatures of the users are displaced with respect to each other. In this context we show that the value of kappa(max) of improved random O(rthogonal)CDMA/ OCDMA (O/O) can further be increased as compared to the original *improved O/O system (with square-root cosine rolloff pulses) by an appropriate choice of the chip pulse. In addition to this, improved O/O systems with fixed signature set can achieve values of that are as high as those in the improved random O/O system, while not having the drawback of a spread on Applying a steepest descent search to such a fixed improved O/O system, can result in a system with a binary signature set that has even higher values for kappa(max) well beyond the upper bound on Kmax for systems with aligned chip pulses.