Sea clutter simulation

Includes bibliograpical references.This dissertation presents the results of a study, the aim of which was the prediction of sea clutter characteristics including the temporal properties of the return signals as observed by a maritime surveillance radar system. The compound K distribution model used to generate clutter amplitude statistic enables the simulation of sea clutter with a good level of approximation to real radar data and this model forms the basis for the simulation of sea clutter amplitude statistic in this dissertation. Using this distribution, a sea clutter simulator is designed to generate correlated K distributed random variates from a predefined correlation function using the method by Ward and Tough [1 ]. Results from the sea clutter simulator shows that the simulated correlated random variates fit the theoretical K distribution PDF. Experimental sea clutter measurements were carried out using an experimental netted radar system. This was done at Scarborough Cape Town. Result obtained from the monostatic node is presented. This shows the amplitude statistics of the clutter as well as the temporal variation of the Doppler spectrum. Conclusions are drawn based on this results and suggestions made for further work

Generation of correlated Rayleigh fading channels for accurate simulationof promising wireless communication systems

In this paper, a generalized method is proposed for the accurate simulation of equal/ unequal power correlated Rayleigh fading channels to overcome the shortcomings of existing methods. Spatial and spectral correlations are also considered in this technique for different transmission conditions. It employs successive coloring for the inphase and quadrature components of successive signals using real correlation vector of successive signal envelopes rather than complex covariance matrix of the Gaussian signals which is utilized in conventional methods. Any number of fading signals with any desired correlations of successive envelope pairs in the interval [0, 1] can be generated with high accuracy. Moreover, factorization of the desired covariance matrix is avoided to overcome the shortcomings and high computational complexity of conventional methods. Extensive simulations of different representative scenarios demonstrate the effectiveness of the proposedtechnique. The simplicity and accuracy of this method will help the researchers to study and simulate the impact of fading correlation on the performance evaluation of various multi-antenna and multicarrier communication systems. Moreover, it enables the engineers for efficient design and deployment of new schemes for feasible wireless application

A Generalized Algorithm for the Generation of Correlated Rayleigh Fading Envelopes

Although generation of correlated Rayleigh fading envelopes has been intensively considered in the literature, all conventional methods have their own shortcomings, which seriously impede their applicability. In this paper, a very general, straightforward algorithm for generation of an arbitrary number of Rayleigh envelopes with any desired, equal or unequal power, in wireless channels either with or without Doppler frequency shifts, is proposed. The proposed algorithm can be applied in case of spatial correlation, such as with antenna arrays in Multiple Input Multiple Output (MIMO) systems, or spectral correlation between the random processes like in Orthogonal Frequency Division Multiplexing (OFDM) systems. It can also be used for generating correlated Rayleigh fading envelopes in either discrete-time instants or a real-time scenario. Besides being more generalized, our proposed algorithm is more precise, while overcoming all shortcomings of the conventional methods

A comparative study of Rayleigh fading wireless channel simulators

Computer simulation is now increasingly being used for design and performance evaluation of communication systems. When simulating a mobile wireless channel for communication systems, it is usually assumed that the fading process is a random variate with Rayleigh distribution. The random variates of the fading process should also have other properties, like autocorrelation, spectrum, etc. At present, there are a number of methods to generate the Rayleigh fading process, some of them quite recently proposed. Due to the use of different Rayleigh fading generators, different simulations of the same communication system yield different results. Three methods, viz., the Jakes method, the IDFT method and the filtering WGN method, have been studied, simulated and compared based on the Rayleigh fading process' properties. Various communication systems have been simulated using the Rayleigh fading generators and the difference in the results, if any, have been analyzed. The research studies the different Rayleigh fading generators and compares them using the properties of the Rayleigh fading channel. It is found that the IDFT method and the filtering WGN method generate processes that have properties very close to the ideal Rayleigh fading process

Reconfigurable OFDM Tx/Rx for multi-purpose physical layers over fast Heterogenous Systems

Los objetivos principales en este proyecto son los análisis matemáticos y prácticos de diferentes generadores de variables Rayleigh, estimadores de canal y estrategias para su implementación de una manera reconfigurable a través de Simulink y FPGA. La diferentes técnicas para generar variables Rayleigh usadas en este proyecto son las siguientes: la suma de sinusoides, la técnica de Smith y el método de Bealieu-Young. El primero se base en la suma de exponenciales complejas mientras los otros dos se basan en la IDFT. De todos estos métodos vemos que el método de Bealieu-Young tiene la mínima complejidad para la misma precisión que los otros métodos. En consecuencia ha sido el escogido para ser implementado en la FPGA Cuando hablamos de estimadores de canal se han considerado dos enfoques diferentes. El primero consiste en introducir los pilotos de manera uniforme a lo largo de la trama, mientras el otro introduce los pilotos al principio de la trama. A la hora de estimar la trama dos estrategias han sido analizadas: el estimador de canal promedio y el estimador de canal por interpolación lineal. La técnica de promediado se puede considerar como un filtro paso bajo. En este caso el estimador por promediado es capaz de eliminar la frecuencias altas que son introducidas por el ruido. Por el contrario el estimador por interpolación lineal, ofrece los mejores resultados cuando el ruido es bajo. En ambos casos hemos calculado la potencia de error en el proceso de estimación. Los resultados prácticos y teóricos obtenidos a través de Matlab y Simulink concuerdan a la perfección. En un escenario co-simulado la FPGA trabaja con Matlab. Los resultados nos dicen que el sistema se ve limitado por el cable que conecta ambos sistemas. Por lo que es crucial para aprovechar al máximo la potencia de la FPGA que el sistema si integre por completo dentro de la FPGA y si no es posible usar conexiones de alta velocidad. English: The main goals of this project are the study from a mathematical and practical point of views of different correlated Rayleigh fading generator, linear channel generator estimators, and strategies for implementing them in a reconfigurable way by means of Simulink and FPGA. Thus it is not necessary to remap again the FPGA for different configurations of the channel estimation. The techniques of correlated Rayleigh fading that has been analysed under this project are the next: the sum of sines, the Smith technique and Bealieu-Young method. The first one consists on a sum of exponentials whereas the others two algorithms are based on decompositions based on IDFT. From all these methods we show that the Bealieu-Young channel generation requires a lower complexity for the same accuracy. Consequently, this method of channel estimation is the technique that has been implemented into the FPGA. Regarding to the channel estimation process two different approaches has been considered. The first one consists on spreading the pilots uniformly along the frames, whereas the other one places the pilots at the beginning of the frames. Next, in order to estimate the channel two strategies have been analysed: the averaging channel estimator and the linear interpolation technique. The averaging strategy can be considered as a low pas filter. So, it offers the best results when there channel is flat and the noise is high. In this case, the averaging filter is able to remove the high frequencies that introduce the noise signal. On the contrary, the linear interpolator gives the best performance when the noise level is small. Moreover, it allows a degree of mobility, which limits the distance between the pilots. In both cases we have computed the theoretical error power of the channel estimators. The practical results from Matlab and Simulink perfectly match with the theoretical ones. In a co-simulation environment the FPGA works with Matlab. The results show that the speed of the simulation is limited by the wire that connects the FPGA and Matlab. So, it is crucial for a hardware accelerator to try to integrate the full system into the FPGA and if it is not possible to use high-speed links between the FPGA and Matlab

A simulation model for HF channels that are characterized by Nakagami m-fading, m<1

Experimental results have indicated that the Nakagami (1960) m-distribution with the fading parameter m in the range 0.5<m<1 can be used to model the fading characteristic of a HF channel when its fading is more severe than Rayleigh fading. In this paper, we propose a mathematical model for simulating a HF channel that is characterized by m-fading, m<1. The procedure for implementation is given. Numerical results demonstrate that statistical properties of the samples generated from the proposed model are close to the required ones.published_or_final_versio