Diversity and channel estimation using time-varying signals and time-frequency techniques

Research output: Contribution to journalArticlepeer-review

32 Scopus citations


We propose the use of time-varying (TV) signaling in modulation schemes to provide multiuser detection and multipath diversity in TV wireless channels. Specifically, we design an orthogonal linear chirp modulation scheme that is based on assigning different users with optimally designed parameters in order to reduce multiple-access interference. We also derive conditions on the parameters of the modulation signals to achieve multi-path diversity. Furthermore, we propose the use of TV pilot signals with nonlinear instantaneous frequency and matched time-frequency (TF) techniques to estimate fast-fading channels with unknown state information. The proposed algorithm simplifies to the estimation of the parameters of multiple linear chirps, which we perform using the modified matching pursuit decomposition. We compare our estimation method with the use of pilot signals with linear instantaneous frequency, which we implement using the reassigned spectrogram. The proposed modulation scheme is applied to a frequency-hopped code-division multiple-access system for which we demonstrate improved performance when compared with frequency-shift-keying (FSK) modulation due to the designed multipath diversity and low multiple-access interference. Our simulations also demonstrate the increased estimation performance when pilot signals with nonlinear structures are used instead of linear structured ones to estimate TV channel parameters.

Original languageEnglish (US)
Pages (from-to)3400-3413
Number of pages14
JournalIEEE Transactions on Signal Processing
Issue number9
StatePublished - Sep 2006


  • Linear chirp
  • Modulation scheme
  • Multiple-access interference
  • Time-frequency analysis
  • Time-varying channel
  • Waveform design

ASJC Scopus subject areas

  • Signal Processing
  • Electrical and Electronic Engineering


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