Cancellation and error correction for narrowband interference with spectral nulls codes and OFDM modulation

Distance Preserving Mappings (DPM) is a relatively new technique finding its way to a wide use in the coding field. New codes mapping convolutional code outputs onto spectral nulls codewords have the purpose of generating a code with a certain spectrum specification and error correction capabilities, which can be exploited by the Viterbi decoder. Combining this class of new codes with an OFDM modulation scheme is actually a tool to reduce Electromagnetic Compatibility Interference (EMC) in selected subbands or to cancel the narrowband interference (NBI) potentially caused by, amongst others, HF radio transmissions. Taking into consideration the fact that a narrowband noise source is almost similar to a modulated OFDM carrier, and also the periodicity of the nulls in our spectrum, we are able to cancel the narrowband signal and its sideband interferences without using traditional techniques of cancellation, which is based on filtering. Shaping our spectrum at the transmitter is a technique, which can be exploited at the receiver to suppress any narrowband signal interference, which is regarded as noise. We will present in this paper the technique of cancellation and the coding gain that can be obtained when comparing to the uncoded data.