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This paper deals with some important statistical properties of the channel capacity of multiple-input-multiple-output (MIMO) systems with orthogonal space-time block code (OSTBC) transmission. We assume that all the subchannels are uncorrelated. For OSTBC-MIMO systems, exact closed-form expressions are derived for the probability density function (PDF), the cumulative distribution function (CDF), the level-crossing rate (LCR), and the average duration of fades (ADF) of the channel capacity. Furthermore, it will be shown that these exact closed-form expressions can be used to characterize the channel capacity of single-input-multiple-output (SIMO) and multiple-input-single-output (MISO) systems. In addition, a Gaussian approximation to the exact LCR of the capacity of OSTBC-MIMO systems is derived. The correctness of the derived closed-form expressions and the approximation is confirmed by simulations. Index Terms--Average duration of fades (ADF), channel capacity, cumulative distribution function (CDF), level-crossing rate (LCR), orthogonal space-time block code (OSTBC)-multiple-input-multiple-output (MIMO) systems, probability density function (PDF), Rayleigh fading channels.

For the simulation of practical frequency-diversity wireless communication systems, such as frequency-hopping systems, multicarrier code-division multiple-access systems, and orthogonal frequency-division multiplexing systems, it is often desirable to produce multiple Rayleigh fading processes with given frequency correlation properties. In this paper, a novel stochastic wide-sense stationary sum-of-sinusoids channel simulator is proposed to emulate frequency-correlated wideband fading channels, where the frequency correlation properties are controlled by only adjusting the constant phases. Closed-form expressions are provided for all the parameters of the simulation model. This enables us to investigate analytically the overall correlation properties (not only the correlation coefficients) of the simulated processes with respect to both time separation and frequency separation. It is shown that the wideband channel simulator will be reduced to a narrowband Rayleigh fading-channel simulator by removing the frequency selectivity. Furthermore, the COST 207 typical-urban and rural-area channels are applied to evaluate the performance of the resulting wideband and narrowband channel simulators, respectively. The correlation properties of the simulation models approach the desired ones of the underlying reference models as the number of exponential functions tends to infinity, while very good approximations are achieved with the chosen limited number of exponential functions. Index Terms--Frequency correlation, Rayleigh fading channels, statistics, stochastic sum-of-sinusoids channel simulators, wideband fading channels.

We consider the problem of creating signal constellations for trellis-coded unitary space-time communication links, where neither the transmitter nor the receiver knows the fading gains of the channel. Our study includes constellation-design techniques for trellis-coded schemes with and without parallel paths, which allows us to find a tradeoff between low complexity and high performance. We present a new formulation of the constellation design problem for trellis-coded unitary space-time modulation (TCUSTM) schemes. The two key differences in our approach against those of other authors are that we not only combine the constellation design and mapping by set partitioning into one step, but we also use directly the Chernoff bound of the pairwise error probability as a design metric. By novelly employing a theorem for the Clarke subdifferential of the sum of the k largest singular values of the unitary matrix, we also present a numerical optimization procedure for finding signal constellations resulting in high-performance communications systems. To demonstrate the advantages of our new design method, we report the best constellations found for TCUSTM systems. Simulation results show that these constellations achieve a 1-dB coding gain at a bit-error rate of [10.sup.-4] against usually used constellations. Index Terms--Constellation design, multiple antennas, non-coherent communications, trellis-coded modulation (TCM).

In this paper, study of the second order statistics of the Nakagami-Hoyt fading channel model (Nakagami-q model) is considered. Expressions for the level crossing rate (LCR) as well as the average duration of fades (ADF) are derived. It is shown that the obtained analytical quantities best fit the corresponding measurement data for an equivalent mobile satellite channel in the case of an environment with heavy shadowing. This leads to the conclusion that the Nakagami-q model is applicable to realistic mobile communication channels. A simple and efficient deterministic simulation model based on the Rice's sum of sinusoids, which enables the emulation of the fading envelope of the Nakagami-q model with the desired statistics, is also described. A very good agreement is obtained between the simulated, analytical, and experimental statistics. Index Terms--Deterministic channel modeling, fading channels, Nakagami-Hoyt channel, Nakagami-q model, second order statistics.

In this paper, five fundamental methods are proposed to model the multipath power-delay profile of frequency-selective indoor and outdoor wireless channels. Three of them are new, and the other two are well known, but their performance, however, has not been studied in detail up until now. All procedures are universally valid so that they can be applied to any specified or measured multipath power-delay profile. The performance of the proposed methods is investigated with respect to important characteristic quantifies such as the frequency correlation function (FCF), average delay, and delay spread. The method found to perform best is the so-called [L.sup.p]-norm method (LPNM). This procedure is applied to measurement data of multipath power-delay profiles collected in different propagation environments. It is shown that the realization complexity of tapped-delay line-based simulation models for fading channels can be reduced considerably by using the LPNM. This is a great advantage for the development and specification of channel models for future wireless systems. Index Terms--Deterministic channel modeling, mobile radio channels, multipath channels, multipath power-delay profile, tapped-delay line model.

The level-crossing rate, average duration of fades and cumulative distribution of deterministic simulation models for Rice fading channels were analyzed. Exact and simple approximative formulas were derived for these parameters. Various procedures for the design of the parameters of the deterministic simulation model were used to present the numerical results for the derived formulas. The results of comparisons with simulation models are also presented.

This paper deals with the statistical characterization of a stochastic process which is a product of a Rice and lognormal process. Thereby, we consider the more general case where the two Gaussian noise processes describing the Rice process are correlated. The resulting process will be named as extended Suzuki process, which can be used as a suitable statistical model for describing the fading behavior of large classes of frequency nonselective land mobile satellite channels. In particular, the statistical properties [e.g., probability density function (pdf) of amplitude and phase, level-crossing rate, and average duration of fades] of the Rice process with cross-correlated components as well as of the proposed extended Suzuki process are investigated. Moreover, all statistical model parameters are optimized numerically to fit the cumulative distribution function and the level-crossing rate of the underlying analytical model to measured data collected in different environments. Finally, an efficient simulation model is presented which is in excellent conformity with the proposed analytical model. Index Terms - Average duration of fades, extended Suzuki process, fading channel simulation, frequency nonselective land mobile satellite channels, level-crossing rate, statistics.

In satellite to mobile communications, there is generally, in addition to the diffuse multipath component, a strong line-of-sight (LOS) component present. The spectral and statistical properties of both components are influenced by shadowing caused by obstacles such as trees, houses, or small buildings. In this paper, an analytical model for a land mobile satellite channel is analyzed that takes into consideration various kinds of shadowing situations. For the LOS component, it is assumed that, first, the received frequency shows a Doppler shift. Second, the amplitude variations coincide with a lognormal distribution. Moreover, it is also assumed that shadowing influences the diffuse scattered component, with the consequence that its Doppler power spectrum gets an asymmetrical shape. The resulting spectral and statistical properties of the analytical model are investigated. Exact solutions for the probability density function (pdf) of the amplitude and phase are given, and approximative solutions for the level-crossing rate (LCR) and average duration of fades (ADF's) are derived. Finally, an efficient deterministic simulation model is presented that enables the implementation of the proposed analytical model on a digital computer. Index Terms - Fading channel modeling, fading channel simulation, land mobile satellite channel, nonfrequency-selective fading, statistics.

Rice's sum of sinusoids can be used for an efficient approximation of colored Gaussian noise processes and is therefore of great importance to the software and hardware realization of mobile fading channel models. Although several methods can be found in the literature for the computation of the parameters characterizing a proper set of sinusoids, only less is reported about the statistical properties of the resulting (deterministic) simulation model. This is the topic of the present paper, whereby not only the simulation model's amplitude and phase probability density function (pdf) will be investigated, but also higher order statistics [e.g., level-crossing rate (lcr) and average duration of fades (adf's)]. It will be shown that due to the deterministic nature of the simulation model, analytical expressions for the pdf of amplitude and phase, autocorrelation function (acf), cross-correlation function (ccf), lcr, and adf's can be derived. We also propose a new procedure for the determination of an optimal set of sinusoids, i.e., the method results for a given number of sinusoids in an optimal approximation of Gaussian, Rayleigh, and Rice processes with given Doppler power spectral density (psd) properties. It will be shown that the new method can easily be applied to the approximation of various other kinds of distribution functions, such as the Nakagami and Weibull distributions. Moreover, a quasi-optimal parameter computation method is presented. Index Terms - Deterministic simulation models, nonfrequency-selective fading channels, Rician channels, statistics.

What terrestrial and satellite land mobile radio channels have in common is that they are usually assumed to be nonfrequency selective. For such fading channels, a highly flexible analytical model is presented. Our model takes into account short-term fading with superimposed long-term lognormal variations of the local mean value of the received signal. It is assumed that the introduced complex stochastical process, which is used for modeling the short-term fading behavior, has a Doppler power spectral density with an asymmetrical shape. Closed solutions are presented showing the influence of asymmetrical Doppler power spectral density shapes on the statistical properties of the proposed channel model. A numerical optimization procedure is shown for the optimization of the model parameters in order to fit the statistics of the analytical model [amplitude probability density function (pdf), level-crossing rate (LCR), and average duration of fades (ADF)] to measurement results of an equivalent land mobile satellite channel for light and heavy shadowing environments. Finally, from the analytical model, an efficient simulation model is derived that enables the simulation of such realistic land mobile satellite channel scenarios on a digital computer. Index Terms - Average duration of fades, extended Suzuki process, level-crossing rate, nonfrequency-selective fading.

We present a novel computer simulation model for a land mobile radio channel. The underlying channel model takes for granted non-frequency-selective fading but considers the effects caused by shadowing. For such a channel model we design a simulation model that is based on an efficient approximation of filtered white Gaussian noise processes by finite sums of properly weighted sinusoids with uniformly distributed phases. In all, four completely different methods for the computation of the coefficients of the simulation model will be introduced. Furthermore, the performance of each procedure will be investigated on the basis of two quality criteria. All the presented methods have in common that the resulting simulation model has a completely determined fading behavior for all time. Therefore, the simulation model can be interpreted as a deterministic model that approximates stochastic processes such as Rayleigh, log-normal, and Suzuki processes.