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The Long-Term Evolution broadband will become the dominant technology for the next generation of communication systems. Its performances in terms of capacity and error rate are studying for rural and urban environment. However, even if this is a special case, tunnel environment is often encountered. The objective of this paper is to predict the error rate by using software simulating the proposed LTE data processing and by introducing, in this software, channel transfer functions measured in tunnels. Among all possible transmission modes, emphasis is on the transmit diversity schemes. After a brief description of the channel characteristics and of the simulation process, improvement brought by the possible configurations of transmit diversity is studied, the frequency band being around 3.4 GHz.

In this paper, a 4 x 4 indoor multiple-input multiple-output (MIMO) measurement campaign at a frequency of 2.45 GHz is presented. The main contribution of this work is the analysis of the impact of radio-wave polarization in MIMO systems operating at a typical indoor scenario through the calculation--from the measurements carried out-of a great deal of parameters such as the mean path loss, the cross polarization discrimination (XPD), and the RMS delay spread, which are all essential to estimate the performance of real MIMO systems. In this sense, some path loss models--which have been adjusted according to the measurements-are given, taking into account polarization, attenuation through walls, and the effect of T-junctions existing in the considered indoor scenario. Moreover, additional parameters such as the K-factor and statistical distribution, as well as spatial parameters, are discussed. Index Terms--Correlation, delay spread, indoor, measurements, multiple-input multiple-output (MIMO), path loss, polarization, propagation.

A modified hybrid uniform theory of diffraction-physical optics formulation for the analysis of the multiple diffraction caused by an array of cylinders, assuming spherical-wave incidence, is hereby presented. The solution, validated with numerical data from technical literature, is mathematically less complex and computationally more efficient--particularly for a large number of cylinders--than other existing methods, due to the fact that high-order diffraction terms (slope diffraction) are not considered, without such lack of terms barely entailing any loss in accuracy. Results can be applied in radiowave propagation analysis when multiple diffraction over rounded obstacles has to be considered. Index Terms--Multiple diffraction, radiowave propagation.

A hybrid uniform theory of diffraction (UTD)--physical optics (PO) formulation for the analysis of the multiple diffraction which takes place in urban environments where a cylindrical hill, either smooth or with buildings located on its surface, causes shadowing of the transmitter from the receiver (a non-line-of-sight situation) is presented, thus furthering a previous study published by the authors, in which the hill is modeled as a wedge. The mentioned UTD-PO solution, which is validated by numerical results from technical literature, is of a good computational efficiency, while at the same time increasing the versatility over other methods for the analysis of the same scenarios, since the presented hybrid formulation allows for the study of the above-mentioned environment when the urban area consists of a small number of buildings. Index Terms--Mobile radio systems, multiple diffraction, radiowave propagation.

Two microcellular environments, which are the regular and chaflane street corners, are compared using a ray-launching engine based on the uniform theory of diffraction and geometric optics. This paper includes a study on the signal-to-noise ratio (SNR), K factor, correlation, and multiple-input multiple-output capacity. Two situations, which are the line-of-sight (LOS) and the non-LoS (NLoS), are distinguished and studied separately. In NLoS, the influence of the SNR is higher than the effect of the correlation. However, in LoS, the SNR is comparable in both environments, and correlation determines capacity. Index Terms--Correlation, K factor, MIMO capacity, multiple-input multiple-output (MIMO), regular and chaflane street corners.

Channel sounding techniques are used to investigate and compare two micro-cellular environments: regular and chaflane street corners, at four different frequencies using a network analyzer. Parameters are extracted from the power delay profile, which is obtained us the inverse Fourier of the measured frequency response. It is shown that, for line of sight (LoS), delay spread (DS) decreases 10 ns in regular corners and 5 ns in chaflane when frequency varies from 450 to 2400 MHz. For non line of sight (NLoS), RMS DS is around 60 ns in both environments. Frequency correlation is higher in chaflanes than in regular street corners and correlation decreases when the distance in frequency increases. Tapped delay line models are obtained at each frequency in each environment for LoS and NLoS. Finally, for LoS, the coherence bandwidth is bigger in chaflanes than in regular street corners, and it is also observed that it grows as frequency increases. However, for NLoS, the bandwidth remains steady around 4 MHz. Index Terms--Chaflane and regular street comer, coherence bandwidth, delay spread (DS), microcell.

The wide-band complex transfer function and propagation characteristics in a small passageway tunnel for nonline-of-sight are studied in this paper. A two-dimensional wide-band model based on the uniform theory of diffraction (UTD) and geometric optics (GO) is implemented and a network analyzer is used to perform measurements. In order to obtain the power delay profile, a correction factor is used, which adjusts the deviation caused by the windowing and zero padding performed in frequency domain. The UTD model predicts quite well the averaged path loss, power delay profile, root-mean-square (rms) delay spread and coherence bandwidth, even when the curved tunnel is approximated to two straight lines. Furthermore, it is shown that the position of the transmitter is crucial in the performance of the system: the path loss slope and rms delay spread are increased when the inclination of the transmitter is increased. In all cases, the rms delay spread is lower than 40 ns, where the coherence bandwidth decreases to 20 MHz. This parameter is proposed to estimate the excitation zone inside a tunnel. Index Terms--Coherence bandwidth, delay spread, propagation, tunnel environments, wide-band complex transfer function.