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  • Research Article
  • Open Access

Nonstationary Interference Excision in Time-Frequency Domain Using Adaptive Hierarchical Lapped Orthogonal Transform for Direct Sequence Spread Spectrum Communications

EURASIP Journal on Advances in Signal Processing20032003:579378

Received: 22 November 2002

Published: 20 November 2003


An adaptive hierarchical lapped orthogonal transform (HLOT) exciser is proposed for tracking, localizing, and rejecting the nonstationary interference in direct sequence spread spectrum (DSSS) communications. The method is based on HLOT. It utilizes a fast dynamic programming algorithm to search for the best basis, which matches the interference structure best, in a library of lapped orthogonal bases. The adaptive HLOT differs from conventional block transform and the more advanced modulated lapped transform (MLT) in that the former produces arbitrary time-frequency tiling, which can be adapted to the signal structure, while the latter yields fixed tilings. The time-frequency tiling of the adaptive HLOT can be time varying, so it is also able to track the variations of the signal time-frequency structure. Simulation results show that the proposed exciser brings significant performance improvement in the presence of nonstationary time-localized interference with or without instantaneous frequency (IF) information compared with the existing block transform domain excisers. Also, the proposed exciser is effective in suppressing narrowband interference and combined narrowband and time-localized impulsive interference.


  • nonstationary interference excision
  • adaptive hierarchical lapped orthogonal transform
  • hierarchical binary tree
  • best basis selection
  • dynamic programming algorithm

Authors’ Affiliations

Department of Electronics Engineering, Shanghai Jiao Tong University, Shanghai, China
College of Information Engineering, Dalian Maritime University, Liaoning, China


© Copyright © 2003 Hindawi Publishing Corporation 2003