Suppression of multiuser interference (MUI) and mitigation of multipath effects constitute major challenges in the design of third-generation wireless mobile systems. Most wide-band and multicarrier uplink code-division multiple-access (CDMA) schemes suppress MUI statistically in the presence of unknown multipath. For fading resistance, they all rely on transmit- or receive-diversity and multichannel equalization based on bandwidth-consuming training sequences or self-recovering techniques at the receiver end. Either way, they impose restrictive and difficult to check conditions on the finite-impulse response channel nulls. Relying on block-symbol spreading, we design a mutually-orthogonal usercode-receiver (AMOUR) system for quasi-synchronous blind CDMA that eliminates MUI deterministically and mitigates fading regardless of the unknown multipath and the adopted signal constellation. AMOUR converts a multiuser CDMA system into parallel single-user systems regardless of multipath and guarantees identifiability of users' symbols without restrictive conditions on channel nulls in both blind and nonblind setups. An alternative AMOUR design called Vandermonde-Lagrange AMOUR is derived to add flexibility in the code assignment procedure. Analytic evaluation and preliminary simulations reveal the generality, flexibility, and superior performance of AMOUR over competing alternatives.
Bibliographical noteFunding Information:
Paper approved by M. Brandt-Pearce, the Editor for Modulation and Signal Design of the IEEE Communications Society. Manuscript received February 17, 1999; revised December 30, 1999 and March 29, 2000. This work was supported by the National Science Foundation under CCR Grant 98-05350 and by the Army Research Laboratory under Grant DAAL01-98-Q-0648. This paper was presented in part at the International Conference on ASSP, Phoenix, AZ, March 1999, and in part at GLOBECOM, Rio de Janeiro, Brazil, December 1999.