Narrowband interference rejection in OFDM via carrier interferometry spreading codes

Orthogonal frequency-division multiplexing (OFDM) has gained a great deal of attention lately and is considered as a strong candidate for many next-generation wireless communication systems. However, OFDM (in its current implementation) does not demonstrate robustness to narrowband interference. In our earlier work, we showed how carrier interferometry (CI) spreading codes may be applied to spread OFDM symbols over all N subcarriers - this allows OFDM to exploit frequency diversity and improve performance (without loss in throughput). In this paper, we show that, by spreading OFDM symbols over all N subcarriers via CI spreading codes, the resulting carrier interferometry OFDM (CI/OFDM) system is also capable of suppressing narrowband interference. Simulation results for OFDM, coded OFDM (COFDM), CI/OFDM, and coded CI/OFDM over additive white Gaussian noise and multipath fading channels confirm CI/OFDM's robustness to narrowband interference.