Coding Versus Spreading for Narrowband Interference Suppression

The use of active narrowband interference (NBI) suppression in direct-sequence spread-spectrum (DS-SS) communications has been extensively studied. In this paper, the authors address the problem of optimum coding–spreading tradeoff for NBI suppression. With maximum-likelihood (ML) decoding, the authors first derive upper bounds on the error probability of coded systems in the presence of a special class of NBI, namely, multitone interference with orthogonal signatures. By employing the well-developed bounding techniques, the authors show that there is no advantage in spreading, and hence, a low-rate full-coding approach is always preferred. Then, the authors propose a practical low-rate turbo-Hadamard coding approach, in which NBI suppression is naturally achieved through iterative decoding. The proposed turbo-Hadamard coding approach employs a kind of coded spread-spectrum signaling with time-varying spreading sequences, which is sharply compared with the code-aided DS-SS approach. With a spreading sequence of length 32 and a fixed bandwidth allocated for both approaches, it is shown through extensive simulations that the proposed turbo-Hadamard coding approach outperforms the code-aided DS-SS approach for three types of NBI, even when its transmission information rate is about five times higher than that of the code-aided DS-SS approach. The use of the proposed turbo-Hadmard coding approach in multipath fading channels is also discussed.


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  • Accession Number: 01597952
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 19 2016 3:57PM