A generalized frequency-hopping (GFH) orthogonal frequency-division multipl
e-access (OFDMA) system is developed in this paper as a structured long cod
e direct-sequence code-division multiple-access (DS-CDMA) system in order t
o bridge frequency-hopped multicarrier transmissions with long code DS-CDMA
. Through judicious code design, multiuser interference is eliminated deter
ministically in the presence of unknown frequency-selective multipath chann
els. Thanks to frequency-hopping, no single user suffers from consistent fa
ding effects and constellation-irrespective channel identifiability is guar
anteed regardless of channel nulls, A host of blind channel estimation algo
rithms are developed trading off complexity with performance. Two important
variants, corresponding to slow- and fast-hopping, are also addressed with
the latter offering symbol recovery guarantees. Performance analysis and s
imulation results illustrate the merits of GFH-OFDMA relative to convention
al OFDMA and long code DS-CDMA with pseudorandom noise codes and RAKE recep
tion.