This paper investigates the sensitivity of several multiple-access techniqu
es to narrow-band interference. The analysis covers time-division multiple
access (TDMA), code-division multiple access (CDMA), and the more recently
introduced orthogonal frequency-division multiple access (OFDMA). The study
is carried out under the assumption that all considered multiple-access sy
stems occupy the same total bandwidth, and the bit rates of all active user
s are identical, A major finding of this study is that CDMA with pseudonois
e spreading sequences is more sensitive to narrow-hand interference than TD
MA. We point out that the signal-to-jammer power ratio at the decision devi
ce input is in fact identical for both multiple-access techniques, but the
amplitude distribution of the jammer term at the threshold detector input i
s more favorable to TDMA, which turns out to be more robust in terms of bit
-error rate. Another finding is that in terms of sensitivity to narrow-band
interference, orthogonal CDMA (OCDMA) is closer to OFDMA than to CDMA with
pseudonoise sequences, because the degradation is not the same for all use
rs. Finally, we discuss the relationship of OCDMA and OFDMA and highlight t
he superiority, in terms of capacity over the narrow-band interference chan
nel, of OFDMA to the other multiple-access techniques considered in this pa
per.