TY - JOUR
T1 - Diversity and channel estimation using time-varying signals and time-frequency techniques
AU - Shen, Hao
AU - Papandreou-Suppappola, Antonia
N1 - Funding Information:
Manuscript received September 28, 2004; revised September 15, 2005. The associate editor coordinating the review of this manuscript and approving it for publication was Dr. Chong-Yung Chi. This material is based upon work supported by the National Science Foundation CAREER Grant CCR-0134002 and by the Department of Defense, administered by the Air Force Office of Scientific Research, Grant No. AFOSR FA9550-05-1-0443.
PY - 2006/9
Y1 - 2006/9
N2 - 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.
AB - 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.
KW - Linear chirp
KW - Modulation scheme
KW - Multiple-access interference
KW - Time-frequency analysis
KW - Time-varying channel
KW - Waveform design
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U2 - 10.1109/TSP.2006.877665
DO - 10.1109/TSP.2006.877665
M3 - Article
AN - SCOPUS:33947183738
SN - 1053-587X
VL - 54
SP - 3400
EP - 3413
JO - IEEE Transactions on Signal Processing
JF - IEEE Transactions on Signal Processing
IS - 9
ER -