In communication systems transmitting data through unknown fading channels, traditional detection techniques are based on channel estimation (e.g., by using pilot signals), and then treating the estimates as perfect in a minimum distance detector. In this thesis, we derive and investigate an optimal detector that does not estimate the channel explicitly but jointly processes the received pilot ...

Motivated by unique atmospheric scattering properties of optical waves at petahertz frequencies, we present a novel maximal selective transmit diversity scheme based on the selection maximum irradiance path with continuous waveform detector employed for wireless communications. The proposed is designed to significantly improve performance non-line-of-sight (NLOS) link in turbulence-induced fadi...

Orthogonal frequency division multiplexing (OFDM) provides an effective and low complexity means of eliminating intersymbol interference for transmission over frequency selective fading channels. This technique has received a lot of interest in mobile communication research as the radio channel is usually frequency selective and time variant. In OFDM system, modulation may be coherent or differ...

Orthogonal multicode direct sequence code division multiple access (DS-CDMA) has a flexibility in offering various data rate services. However, in a frequency-selective fading channel, the bit error rate (BER) performance is severely degraded since othogonality among spreading codes is partially lost. In this paper, we apply frequency-domain equalization and antenna diversity combining, used in...

In direct sequence code division multiple access (DSCDMA), variable rate transmission can be realized by simply changing the spreading factor SF for the given chip rate. In a frequency-selective fading channel, the transmission performance can be improved by using rake combining. However, when a very low SF is used for achieving a high transmission rate, error floor is produced due to insuffici...

This paper explores antenna diversity issues for Orthogonal Frequency Division Multiplexing (OFDM) in frequency flat and selective fading environment using three combining methods – maximal ratio combining (MRC), equal gain combining (EGC), and selection combining (SC). For OFDM, diversity combining can be done on individual subcarriers (narrowband combining) or on the entire OFDM symbol (wideb...

We consider a system where an agent (Alice) aims at transmitting a message to a second agent (Bob), while keeping a third agent (Eve) in the dark, by using physical layer techniques. For a transmission over frequency non selective block fading channels, we assume that Alice perfectly knows the channel with respect to Bob, but she has only a statistical knowledge of the channel with respect to E...

Estimating a channel that is subject to frequency selective Rayleigh fading is a challenging problem in an orthogonal frequency division multiplexing (OFDM) system. In this paper we propose an enhanced channel estimation algorithm that combines the EM-based algorithms proposed previously and a Least Squares polynomial fitting (LSPF) approach. The combined algorithm can efficiently estimate the ...

This paper presents the root-mean-squared tracking error performance analysis of a class of coherent digital delay-locked loops for multicode direct sequence spread spectrum signals in bandlimited correlated Rayleigh fading channels. In the transmit side, multiple independent PSK-modulated data streams in the in-phase and qudrature phase branches are spread by short mutually orthogonal codes be...

In this paper we consider the detection of Multi-Carrier-Code Division Multiple Access (MCCDMA) signals in frequency selective fading channels using partial channel equalization. By partially compensating for the fading channel amplitude we can reduce the multi-user interference without considerably enhancing the additive noise level. As a result the MC-CDMA scheme can exploit the frequency div...