Digital multi-carrier spread-spectrum for resistance against jamming and multipath

All-digital single-user Multi-Carrier Spread Spectrum (MC-SS) transceivers are studied in this paper and compared with Direct-Sequence Spread-Spectrum (DS-SS) systems under different scenarios. Closed-form bit error rate (BER) expressions are derived for sub-optimum matched filter and optimum minimum mean-square error reception in the presence of additive white Gaussian noise (AWGN) and Narrow-Band Interference (NBI). Although digital MC-SS turns out to outperform DS-SS, the difference is not as pronounced as in their analog counterparts. Closed-form BER expressions are also obtained for MC-SS and DS-SS transmissions propagating through frequency-selective multipath fading channels, and optimality is established for MC-SS when the channel taps are independent identically distributed (i.i.d.). But when the channel taps are non-i.i.d., MC-SS is shown to exhibit near-optimal behavior at high SNR and to outperform DS-SS even though their difference diminishes as the spreading factor increases and proper spreading codes are chosen for DS-SS. Finally, BER performance is carried out for MC-SS and DS-SS in the joint presence of multipath fading and NBI. Simulated BER evaluation illustrates the advantages of MC-SS over DS-SS in the presence of multipath and corroborates its robustness against AWGN and NBI.