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Rain attenuation prediction models for link analysis are essential for satellite communications. The diurnal variations of the rain attenuation statistics are valuable for the effective system designs. In this work, a simple prediction model for diurnal rain attenuation statistics with its conversion scale is proposed. The method of calculating an approximated optimal constant conversion scale was...
In two-cell scenarios with half-duplex relays, the number of diversity branches provided by the relays is sufficient to suppress one interfering signal. However, the same diversity branches are not enough to suppress two interfering signals in three-cell systems. To cope with such a problem, this paper proposes joint interference suppression and multiuser detection for the three-cell wireless relay...
In order to cope with severe interference in heterogeneous networks, this paper proposes a semi-blind interference cancellation scheme, which does not require multiple receive antennas or knowledge about training sequences of the interfering signals. The proposed scheme performs a suboptimal joint channel estimation and signal detection (JCESD) based on a quantized channel approach in order to semi-blindly...
To cope with interference in three-cell multiple relay systems, this paper proposes schemes that detect two users' signals while linearly suppressing one remaining user's signal. The proposed schemes do not require channel state information (CSI) feedback and can drastically reduce the computational complexity compared to the maximum likelihood detection (MLD), which is the optimal signal detection...
This paper presents the comparison between the calculated and measured radiation patterns of a two by two patch antenna array with three different element spacings. The optimum element spacing for a specific grating lobe level is obtained by the proposed optimization process. The optimization goal is to obtain narrowest steering beams with a desirable grating lobe level. The lager element spacing...
This article presents a prototype of educational mobile robotic platform based on MicroPython library system, which enables robot control with Python language programming. Moreover, this robotic platform supports a visual programming environment called Blockly to develop a program, which is very simple and similar to an intuitive jigsaw puzzle. Both Python and Blockly are simple coding tools for first-time...
The authors have been researching large capacity transmission technology using a 4×4 multiple-input multiple-output (MIMO) system to develop Super Hi-Vision (SHV) wireless cameras. As the number of transmitting antennas increases, such as in a 4×4 MIMO system, the complexity of signal detection by maximum likelihood detection (MLD), which is the best technique to achieve a low bit error rate (BER),...
This paper presents a spacing optimization procedure for 2 by 2 steerable arrays. The optimization goal is to obtain narrowest steering beams without grating lobes for all steering angles in two dimensions. The radiation pattern of a single antenna, element pattern, is used for setting a limit of steering angles. Expressions for the array factor are derived and used with an element pattern to obtain...
This paper discusses spectrum allocation vision from market and technology trend. We focus on spectrum usage mainly below 3GHz, which is widely used and congested. There are large rooms of improvement in efficiency on already allocated spectrum. Main concepts of improvement come from introduction of common technology among various spectrum licenses as much as possible, and introduction of common operators...
Recent demand for capacity increase in mobile communications urges the development of both multiple- input multiple-output (MIMO) and small cells. However, overlapping coverage areas between neighboring small cells results in interference-limited networks, where the capacity of the network is severely degraded without superior intercell interference management (IIM) techniques. As one of the superior...
OFDM transmission schemes are adopted in the integrated services digital broadcasting-terrestrial (ISDB-T), the downlink of long term evolution (LTE), etc. In most cases, there are not many delayed paths in the propagation environments, i.e., the wireless channels are likely to be sparse. In addition, when the receiver moves rapidly, the accuracy of channel estimation deteriorates significantly. In...
In this paper, an adaptive codebook precoding scheme is proposed for time-varying multiple-input multiple-output (MIMO) channels with feedback delay. The proposed scheme updates its codebook on the basis of the spherical cap codebook (SCC) approach. In contrast with the conventional radius calculation for SCC, the proposed scheme does not need additional feedback of the cap radius or offline radius...
Applications of millimeter-wave (mm-wave) to high mobility wireless communication scenarios such as high speed trains (HSTs) have been discussed. In the HST scenarios, not only phase noise but also Doppler shift should be considered. In previous works, our proposed iterative phase noise compensation method was evaluated with a dynamic channel model with high Doppler shift. The efficacy of the iterative...
This paper proposes a new spatial and temporal (S/T) pre-equalization technique for time-division-duplex (TDD) mobile multimedia communication systems. Base station (B S) employs an adaptive array antenna (AAA) and an adaptive decision feedback equalizer (DFE) for up-link signal reception. The weight vectors for the up-link AAA and DFE are also used for pre-equalization of signal to be transmitted...
In this paper, we concern with a Cognitive radar operating in an environment with multiple interested targets. It is an intelligent parameter estimation system that the transmitted signal depends on the input signal. The mean-square error of the estimated parameters is derived in the Cram´er-Rao Lower Bound that represent the performance of the system. To improve the ability to find a new target when...
Rain attenuation statistics for an average year in Nonthaburi, Thailand, in 2013-2014, are presented. Particularly, two statistics were calculated from the raw and preprocessed power-level data of the Ku-band beacon signal received at the Thaicom earth station. These statistics were compared with the ITU-R prediction models in 1999 and 2007-2013. The results show that preprocessing is necessary to...
An iterative receiver, proposed in our previous works, employs decision directed phase noise compensation (DD-PNC) and decision directed channel estimation (DDCE), and thus can effectively reduce the effects of phase noise on millimeter-wave (mm-wave) orthogonal frequency division multiplexing (OFDM) systems. When the iterative receiver is applied to mm-wave communications between fixed points and...
Our recent study demonstrated that an iterative max-sum-rate (MSR) precoder with MMSE initialization gives an excellent sum-rate performance in downlink multi-user MIMO systems. As the number of transmit antennas increases, two crucial remarks were made: (1) its performance approaches the dirty-paper coding upper-bound and (2) the one-step iteration gives a decent performance. In this paper first,...
This paper proposes interference suppression schemes by linear combining for wireless multiuser relay communications. Interference from base stations and relays in neighboring cells degrades bit error rate (BER) performance of mobile stations (MSs) near cell boundaries. To suppress such interference for half-duplex relay systems, the proposed methods linearly combine received signals of the first...
As a signal detection method for multiple-input multiple-output (MIMO) communications, this paper proposes multi-stream constrained search (MSCS) that achieves very good trade-off between computational complexity and bit error rate (BER) performance. The proposed method sets a minimum mean-squared error (MMSE) detection result to the starting point. From this point, MSCS searches for signal candidates...
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