This paper presents a multi-directive antenna for point-to-multipoint line-of-sight (LOS) communications. Based on an Electromagnetic Crystal (EC) structure, the proposed antenna is able to provide several simultaneous directive beams in different directions at different frequencies. Thus by conveniently disposing the different communication points in the space and allowing them to communicate at different frequencies, a high performance network can be obtained by using a single antenna. To study the antenna performance, both theoretical analysis and numerical simulations are presented and validated by experimental results.

The Owl Positioning System (OwlPS) was originally designed as a general-purpose Wi-Fi-based indoor positioning system. It is also a tool to compare several positioning techniques from the same input data, and was used for this purpose in previous work. In this work, OwlPS is adapted to a very specific “indoor” environment, namely underground mine tunnels, which brings its own problematics in terms of radio signal propagation and therefore impacts positioning system design. Experiment were conducted at a formerly exploited gold mine, at 70 metres under ground level, across about 400 metres of drifts. Several scenarios were defined to mimic typical use cases.

A joint optimization of the decision feedback equalizer (DFE) filter weights and an erasure slicer is proposed in this letter. The feedback weights of the DFE are constrained with an accurate mean square error (MSE) model as the criterion. An erasure slicer is adopted to further decrease error propagation. Two consecutive 1-D optimizations are shown as good as that of a single 2-D optimization. Simulation results verify the performance improvements of the proposed scheme.

A technique is proposed to mitigate the DFE error propagation effect in high order modulation on highly time dispersive channels. Although the performance improvement is not large with the technique alone, it can offer some advantages in terms of the distribution of error burst length. It could be considered as a primitive channel coding. When combined with an outer RS code, the performance improves significantly. Preliminary results show that this method can achieve more than 1 dB SNR gain below 10-2BER to the conventional DFE of similar interleaving and channel coding scheme.

A technique on optimal decision feedback equalizer (DFE) soft feedback slicer design is proposed in this letter. A soft slicer of M-ary PAM is given as a function of the noise variance at the slicer input. The equalizer mean-square error (MSE), which includes the error propagation effect, is used as the criterion of the optimal soft slicer design. By incorporating the slicer characteristics into the MSE and the assumption of Gaussian noise distribution at the equalizer output, the optimal soft slicer is obtained by minimizing the MSE. Simulation results corroborate the effectiveness of the method.

Smart antenna systems have recently played a central role in removing narrowband multiple-access interference (MAI) in wireless communications. However, if these adaptive systems are proposed for wideband wireless communications the addition of some form of frequency compensation is required. The frequency compensation methods which have been examined are the spectral decomposition, focussing and interpolating techniques. Their performances are compared on the basis of the resulting array patterns. The three frequency compensation techniques are combined with the constant modulus algorithm (CMA) for the adjustment of adaptation weights. Simulation results showing the performance of the system with and without compensation are given and discussed.

This letter presents an efficient and accurate performance evaluation method for binary MC-CDMA systems with deterministic signature sequences. This method is based on a formulation of the characteristic function, and does not resort to any assumption on the statistical or spectral behavior of the interference. The accuracy of the Gaussian approximation method is also considered.

In order to explore design alternatives for point-to-multipoint high rate data transmission systems in various UHF and SHF bands, experimental measurements of radio propagation were made in urban and suburban areas. This paper reports on extensive continuous wave (CW) and wideband measurements performed at four carrier frequencies: 1.44275 GHz, 6.7 GHz, 14.72 GHz and 22.025 GHz. Measurements were carried out in the Montreal metropolitan and suburban areas with both transmitter and receiver stationary. The transmitter was located outside on the rooftop of a high rise building and the receiver inside another building. The receiver was then moved for each new set of measurements such that a whole room was covered in a grid-like fashion. Results from the temporal experiments show, that for the suburban area, the amplitude distributions are lognormal-distributed. The urban area presents more Ricean-distributed amplitude data. The data for the spatially-distributed case also showed that for the suburban and urban areas, the local means of the fluctuations are well described by a Nakagami distribution.

This paper reports on experimental results and their interpretations for an indoor extremely high frequency (EHF) multipath channel. It is intended to help in establishing design guidelines for indoor wireless communications systems using millimeter waves. It deals with measurements obtained for the narrow and wideband indoor radio channels at 37.2 GHz within a typical concrete building at Laval University. Two kinds of transmission antennas, omnidirectional and directional, are used to investigate the propagation characteristics for the indoor channel. Under line-of-sight (LOS) conditions, the distance-power law exponent is found to be lower than the free space condition with walls playing a major role on the sustaining of high level signals. Large- and smallscale variations extracted from the original data are shown to follow log-normal and Rice distributions, respectively. The observed wideband impulse response has delay spread extending over a range up to 40 ns and a maximum root mean square (rms) value of about 16 ns. Both amplitude and phase behaviors of the signals are available for a better understanding of the various effects.

In inverse synthetic aperture radar (ISAR) imaging, the target rotational motion with respect to the radar line of sight contributes to the imaging ability, whereas the translational motion must be compensated out. This paper presents a novel two-step approach to translational motion compensation using an adaptive range tracking method for range bin alignment and a recursive multiple-scatterer algorithm (RMSA) for signal phase compensation. The initial step of RMSA is equivalent to the dominant-scatterer algorithm (DSA). An error-compensating point source is then recursively synthesized from the selected range bins, where each contains a prominent scatterer. Since the clutter-induced phase errors are reduced by phase averaging, the image speckle noise can be reduced significantly. Experimental data processing for a commercial aircraft and computer simulations confirm the validity of the approach.

The various known methods intended for continuous analysis of uncorrelated source fields (MEM-AR, Capon, Borgiotti-Lagunas, Bienvenu-Schmidt) are shown to be based upon a unique conventional diagram, namely one of a spatial linear multiport filter followed by a variance estimator. This filter has K inputs corresponding to K sensors and a single output, and acts as a scalar product system. A fundamental property is then the possibility of having zero responses for the signals coming from K - 1 directions. Using the classical matched filter principle for minimization of undesirable signals (when looking in a given direction), a general class of data-adaptive spatial filters, from which all the above-mentioned methods can be derived with specific choices of parameters, is defined. These filters can be further submitted to normalizing constraints; two examples of this are discussed. This new interpretation leads to the consideration of the above-mentioned methods as special applications of the well-known adaptive array techniques to the estimation problem. Moreover, the asymptotic behaviors are examined when a noise subtraction technique based upon the reduction of the smallest cross-spectral matrix eigenvalue is applied. The convergence toward the Pisarenko solution is ascertained for the estimated directions of the sources, whereas it is not for their estimated intensities (except in the case of the Capon method). In the case of partially correlated sources, the above-mentioned methods are still valid for the localization of sources, but not for their intensities. Other appropriate techniques, such as those of Schmidt, Wax, Shan, and Kailath, must then be considered.