Oversaturating synchronous CDMA systems on the signature per user basis

A strategy for oversaturating synchronous CDMA systems, i.e. increasing the number of users as compared to orthogonal signaling, is proposed. The strategy is based on dividing the global signal space into orthogonal subspaces and supplementing subspaces with extra signatures. Nonorthogonal signatures in subspaces are optimally constructed. Minimum Euclidean distances are found and the tradeoff among capacity, energy efficiency and receiver complexity is discussed.