Lagrange/Vandermonde MUI eliminating user codes for quasi-synchronous CDMAin unknown multipath

A family of codes for low-complexing quasi-synchronous code division multip le access (CDMA) systems Is developed in order to eliminate multiuser inter ference (MUI) completely in the presence of unknown and even rapidly varyin g multipath, Judiciously designed precomputable symbol periodic user codes, which we term Lagrange or Vandermonde, and the corresponding linear receiv ers offer a generalization of orthogonal frequency division multiplexing (O FDM), which are especially valuable when deep-fading, carrier frequency err ors, and Doppler effects are present. The flexibility inherent to the desig ned transceivers is exploited to derive transmission strategies that cope w ith major impairments of wireless CDMA channels, The symbol-periodic code d esign is also generalized to include the class of aperiodic spreading and o rthogonal multirate codes for variable bit rate users. Performance analysis and simulations results illustrate the advantages of the proposed scheme o ver competing alternatives.