Time–frequency channel modeling and estimation of multi-carrier spread spectrum communication systems

Şenay, Seda; Akan, Aydın; Chaparro, Luıs F.

doi:10.1016/j.jfranklin.2005.04.016

Cited by 6 publications

(2 citation statements)

References 14 publications

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“…Time-frequency joint domain representation helps us to estimate frequency shift caused by Doppler's effect as well as time delay estimation [13], [14].…”

Section: B Gabor-division Spread Spectrummentioning

confidence: 99%

Markovian SS codes flatten the spectrum of UWB Gaussian pulse

Kohda

Jitsumatsu

Aihara

2011

2011 IEEE International Conference on Ultra-Wideband (ICUWB)

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Gabor-division (GD) code division multiple access (CDMA) communication, which can provide almost flat power spectrum, has been recently proposed. Using a UWB Gaussian pulse generator implemented by CMOS technology as a funda mental component generating a chip waveform, we apply the GD-CDMA system for UWB communications. Time-frequency two dimensional spread spectrum (SS) codes with Markovity are employed. How Markovian SS codes flatten the spectrum of the transmitted signal is explained.

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“…Time-frequency joint domain representation helps us to estimate frequency shift caused by Doppler's effect as well as time delay estimation [13], [14].…”

Section: B Gabor-division Spread Spectrummentioning

confidence: 99%

Markovian SS codes flatten the spectrum of UWB Gaussian pulse

Kohda

Jitsumatsu

Aihara

2011

2011 IEEE International Conference on Ultra-Wideband (ICUWB)

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“…From the above it is deduced that there is a significant advantage in using chirps as inputs for a LTV channel [21]. The chirp g(n), introduced in multi-carrier communications by [22], is such that its Fourier transform is g(ω), and it is orthogonal to circularly shifted chirps g(n − N 0 ).…”

Section: An Effective Delay and D Is A Complex Constant We Have Thatmentioning

confidence: 99%

An evolutionary time-frequency approach to multi-carrier wireless communications

2006

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This paper provides a time-frequency approach to modeling and estimating the communication channel, and to symbol transmission in multi-carrier wireless systems. The method is based on the evolutionary spectral theory of signals and systems. Multi-carrier systems, such as orthogonal frequency division multiplexing (OFMD) and multi-carrier spread spectrum (MCSS), are very efficient in fast fading channels. However, the basic pulse used in the modulation causes dispersion in time-frequency, complicating inter-symbol and inter-channel interferences. Our time-frequency approach deals separately with the channel modeling and estimation, and with the symbol transmission. Using the properties of the response of the channel to a linear chirp signal it is shown that the typical linear time-variant channel model, needed to characterize multi-path and Doppler, is simplified into a linear time-invariant model of minimal order. Time and Doppler shifts are represented by equivalent time-shifts, and are estimated in a blind fashion from the evolutionary kernel of the received signal. Thus, the linear chirp signal is used as a pilot sequence to characterize the channel. A coherent receiver uses such information to detect the sent symbols.A multi-user OFDM system is obtained using a linear chirp as the modulating signal for basic pulses shifted in time, and by choosing the instantaneous frequency of the linear chirp to be of unity slope for an optimal time-frequency lattice. This optimal lattice increases the transmission rate, diminishes the inter-symbol and inter-channel interference, and provides a new way of looking at OFDM. This approach is extended to MCSS. To illustrate the concepts, simulations, with different signal to noise ratios, are performed. The results are encouraging and worth of further investigation.

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