Low-rate turbo-Hadamard coding approach for narrow-band interference suppression

We propose a low-rate turbo-Hadamard coding approach for narrow-band interference (NBI) suppression. The proposed approach can be viewed as the employment of a coded spread-spectrum signalling with time-varying spreading sequences and the NBI suppression is naturally achieved in iterative decoding. Compared with the traditional code-aided NBI suppression with direct-sequence spread-spectrum (DS-SS) signalling, the spreading sequences for the turbo-Hadamard coding approach are non-constant in time and determined from the columns of a Hadamard matrix subject to the low-rate coding rule. The low-rate turbo-Hadamard coding approach is sharply compared with the code-aided DS-SS approach with convolutional coding. With a spreading sequence of length 32, it is shown that the proposed turbo-Hadamard approach outperforms the code-aided DS-SS approach even when its transmission information rate is about 5 times higher than that of the coded-aided DS-SS approach.