Block precoding for MUI/ISI-resilient generalized multicarrier CDMA with multirate capabilities

Potential increase in capacity along with the need to provide multimedia se rvices and cope with multiuser interference (MUI) and intersymbol interfere nce (ISI) arising due to wireless multipath propagation, motivate well mult irate wideband code-division multiple-access (CDMA) systems. Unlike most ex isting continuous-time symbol-periodic and multipath-free studies, the pres ent paper develops an all-digital block-precoded filter-bank framework capa ble of encompassing single- or multirate transceivers for asynchronous or q uasi-synchronous CDMA transmissions through multipath channels. Thanks to s ymbol blocking and through appropriate design of user codes, the resulting generalized multicarrier (GMC) CDMA system not only subsumes known multicar rier CDMA variants, but also equips them with flexible multirate capabiliti es. It is computationally simple, and guarantees symbol recovery regardless of the (possibly unknown) FIR multipath channels in both downlink and upli nk setups. Simulations corroborate that the novel GMC-CDMA system outperfor ms existing multirate alternatives in the presence of asynchronism and mult ipath, and illustrate the feasibility of recovering blindly multirate trans missions received through unknown frequency-selective channels in the uplin k. Performance of GMC-CDMA system in UNITS channels is also simulated and c ompared with existing multirate schemes.