52 research outputs found
Communications over fading channels with partial channel information : performance and design criteria
The effects of system parameters upon the performance are quantified under the assumption that some statistical information of the wireless fading channels is available. These results are useful in determining the optimal design of system parameters. Suboptimal receivers are designed for systems that are constrained in terms of implementation complexity.
The achievable rates are investigated for a wireless communication system when neither the transmitter nor the receiver has prior knowledge of the channel state information (CSI). Quantitative results are provided for independent and identically distributed (i.i.d.) Gaussian signals. A simple, low-duty-cycle signaling scheme is proposed to improve the information rates for low signal-to-noise ratio (SNR), and the optimal duty cycle is expressed as a function of the fading rate and SNR. It is demonstrated that the resource allocations and duty cycles developed for Gaussian signals can also be applied to systems using other signaling formats.
The average SNR and outage probabilities are examined for amplify-and-forward cooperative relaying schemes in Rayleigh fading channels. Simple power allocation strategies are determined by using knowledge of the mean strengths of the channels.
Suboptimal algorithms are proposed for cases that optimal receivers are difficult to implement. For systems with multiple transmit antennas, an iterative method is used to avoid the inversion of a data-dependent matrix in decision-directed channel estimation. When CSI is not available, two noncoherent detection algorithms are formulated based on the generalized likelihood ratio test (GLRT). Numerical results are presented to demonstrate the use of GLRT-based detectors in systems with cooperative diversity
Some fundamental issues in receiver design and performance analysis for wireless communication
Ph.DDOCTOR OF PHILOSOPH
Performance Evaluation and Simulation of M-Ary Quadrature Amplitude Modulation Schemes with VisSim/Comm Software
M-ary modulation schemes are considered one of widely used digital modulation in practice because of its high efficiency in power and bandwidth. Therefore, this necessity the need to study and evaluate the performance of M-ary schemes using simulation techniques. In this paper, the performance of M-ary modulations schemes M-ary quadrature amplitude modulation (QAM) is considered. Because of its efficiency in power and bandwidth, M-ary QAM (M-QAM) is one of the widely used modulation techniques in practice. Therefore, a need for studying and evaluating the performance of QAM modulation schemes is an important task for designers. In this paper, M-QAM modulation schemes for even number of bits per symbol (16, 62, and 256-QAM) and an odd number of bits per symbol (32- and 128-QAM), over Additive White Gaussian Noise channel, are studied. A VisSim/Comm simulation[1] model for M-QAM is designed. Theoretical and simulation results for bit error ratio (BER) performance of QAM modulation schemes are obtained using VisSim/Comm software. The results are evaluated and compared
Advanced data communication techniques for sub-sea applications
This thesis details research carried out in the through-water data communication field.
An overview of the phenomena that prohibit acoustic communication in long-range
shallow-water channels is constructed. Background research found that robust
communications has not been achieved using single receiver reception in this
environment. This work investigates the modulation technique itself and aims to
improve on existing schemes (that have been applied to this environment). This is
achieved with innovative techniques, based on multiple-frequency-shift-keying
(MFSK) and space-frequency-shift-keying (SFSK). A number of industrial specified
restrictions are placed on this work, including bandwidth restriction. Novel ways of
intrinsically transmitting synchronisation information are therefore implemented. The
development of appropriate systems is covered with general and platform specific
implementation strategies being covered. A single modulation scheme (the three-chip four-frequency-shift-keying, 3C4FSK, scheme) has been put forward for consideration in any future research. Practical lab-based tests and the mathematical analysis is
detailed. Conclusions recommend further funding of long-range shallow sea-water
trails of the 3C4FSK scheme and for the industrial scope of this work to allow
investigation into multiple receiver systems that allow spatial processing of the signal
as these schemes have been shown lately to have potential in long-range channels
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