On quasi-orthogonal signatures for CDMA systems

R.W. Heath, T. Strohmer, A.J. Paulraj
2006 IEEE Transactions on Information Theory  
Sum capacity optimal signatures in synchronous code-division multiple-access (CDMA) systems are functions of the codebook length as well as the number of active users. A new signature set must be assigned every time the number of active users changes. This correspondence considers signature sets that are less sensitive to changes in the number of active users. Equiangular signature sequences are proven to solve a certain max-min signal-to-intererference-plus-noise problem, which results from
more » ... ir interference invariance. Unions of orthonormal bases have subsets that come close to satisfying the Welch bound. Bounds on the maximum number of bases with minimum maximum correlation are derived and a new construction algorithm is provided. Connections are made between these signature design problems, Grassmannian line packing, frame theory, and algebraic geometry. Index Terms-Code-division multiple-access (CDMA) systems, Walsh sequences.
doi:10.1109/tit.2005.864469 fatcat:a5lbidvlavfrra7ycohm7cdjpq