Shinichi Miyamoto

Performance analysis of QAM systems under class A impulsive noise environment

This paper describes the performance of QAM (quadrature amplitude modulation) systems under impulsive noise environment. In the analysis, we employ, as a model of the impulsive noise, Middletons (1977) model labeled class A. First, the statistical characteristics of the in-phase and quadrature components of the impulsive noise are investigated, and it is proved that, in contrast to Gaussian noise, these components are dependent especially for the impulsive noise with small impulsive indices. Next, with consideration of the dependence between the in-phase and quadrature components of the noise, the performance of QAM systems with the conventional receiver designed for Gaussian noise is analyzed. The numerical results show that the performance is much worse than that achieved under Gaussian noise. Moreover, we show the design of the maximum likelihood receiver for class A impulsive noise and the great performance improvement by this receiver is confirmed. >

Effect of microwave oven interference on the performance of digital radio communications systems

We investigate the effects of microwave ovens interference on the performance of digital radio communications systems (PDC, PHS, ISM-band (2.45 GHz) wireless LAN). At first, we experimentally measure the interference radiated from microwave ovens and discuss the statistical characteristics of interference. Then, by using the measurements results, the effects of interference on the performance of /spl pi//4-shift QDPSK and DS/CDMA systems are evaluated. Numerical results conclude that the performance of digital radio communication systems are significantly degraded by the effect of interference. Moreover, we propose a new TDMA channel assignment method for microwave oven interference and investigate the performance improvement achieved by proposed channel assignment.

A study on modeling of microwave oven interference and optimum reception

The performance of digital radio communication systems is much degraded by the effect of microwave oven interference; therefore, in order to obtain a good error performance under microwave oven interference environment, digital radio communication systems should be designed for this environment. In this paper, using Middletons canonical class-A impulsive noise model, the authors propose a statistical model of microwave oven interference and discuss the performance improvement achieved by an optimum reception based on this statistical model. As a result, the first order statistic of microwave oven interference can he modeled by class-A impulsive radio noise, and a great performance improvement is obtained by using the optimum receiver designed against microwave oven interference with sample interleave scheme.

Statistical model of microwave oven interference and optimum reception

Microwave oven interference seriously degrades the performance of digital radio communication systems, therefore, in order to obtain a good error performance under a microwave oven interference environment, the digital radio communication systems should be newly designed for this environment. In this paper, using the Middletons (1977) canonical class-A impulsive noise model, we propose a statistical model of microwave oven interference and discuss the performance improvement achieved by optimum reception based on this statistical model. Numerical results conclude that the first order statistics of microwave oven interference can be modeled by class-A impulsive radio noise, and a great performance improvement is obtained by using the optimum receiver designed against microwave oven interference with the introduction of the sample interleave scheme.

Receiver design using the dependence between quadrature components of impulsive radio noise

A new BPSK receiver based on the statistical characteristics of impulsive radio noise is proposed. First, the statistical characteristics of impulsive radio noise are investigated, and it is proved that the quadrature components of impulsive noise are dependent. Next, with the consideration of the dependence between these components, a new BPSK receiver designed for impulsive noise is proposed, and it is shown that a great performance improvement is achieved by using this receiver. Moreover, the impulsive noise emitted from a microwave oven is experimentally measured, and the performance of this proposed receiver under the microwave oven noise environment is evaluated.

Novel DCF-based multi-user MAC protocol and dynamic resource allocation for OFDMA WLAN systems

To enhance the throughput of wireless local area networks (WLANs) while satisfying the quality of service (QoS) requirements, this paper proposes a novel DCF-based multi-user MAC protocol employing orthogonal frequency division multiple access (OFDMA) scheme. In the proposed protocol, an access point (AP) acts as a master to organize all the stations within the basic service set (BSS) and reserves the radio resource by the conventional distributed coordination function (DCF). In the resource reservation period, the AP performs a flexible access control utilizing the fine-grained resource block and the opportunistic scheduling based on the QoS requirements and the channel condition of each station. With the objective to increase the spectrum efficiency as well as to satisfy the QoS requirements, this paper also proposes a dynamic resource allocation algorithm. Numerical results confirm that the proposed multi-user MAC protocol ensures the QoS requirement with a high probability and enhances the throughput performance.

Optimum detection and design of TCM signals under impulsive noise environment

The optimum detection and the design of trellis-coded modulation (TCM) signals under an impulsive noise environment are investigated. The optimum TCM receiver designed for impulsive noise is proposed, and it is shown that the TCM signals achieve better performance than the uncoded ones. Computer simulation shows that this optimum receiver, which is simple and easy to realize, gives a coding gain from several decibels up to several tens of decibels and that the performance improvement achieved by increasing the number of states of the convolutional codes is greater than that achieved under Gaussian noise. Moreover, from the capacity of the impulsive noise channel with phase modulated signals, it is shown that it is possible to achieve an improvement in performance by using the optimum TCM signal design methods, which are based on the statistical characteristics of the noise.<<ETX>>

A study of the effect of microwave oven interference on the performance of digital radio communications systems

With increasing use of wireless communication systems and electronic equipment using high-frequency devices, a poor electromagnetic environment for wireless communication systems is expected. This paper discusses the microwave oven, which is a widely used ISM apparatus. The effect of the interference waves generated by a microwave oven on the bit error characteristics of various wireless communication systems (PDC, PHS, ISM band wireless LAN) is studied. First, based on the measured interference waves generated from various microwave ovens, the statistical nature of the interference waves is discussed. It is found that a high level interference wave with periodicity is generated from microwave ovens and that the level and duration of the interference wave increase as the oscillation frequency of the magnetron is approached. Next, the bit error rates of π/4 shift QDPSK and DS/CDMA systems are simulated on a computer. It is found that the bit error rate is changed substantially by the effect of the interference wave. Further, for the case where the TDMA system is used as a multiple access system, a channel assignment method based on the periodicity of the interference wave is proposed. It is clear that the bit error rate can be improved significantly by using the proposed channel assignment method.

Spectrum Loading Type Dynamic Spectrum Allocation Technique for Cognitive Radio Systems

This paper proposes a spectrum loading type dynamic spectrum control technique for broadband cognitive radio systems. In the proposed scheme, based on the detection of available spot-wise spectra, discrete spectrum components of a framed symbol sequence are mapped onto the spot-wise spectra. Two spectrum mapping schemes are proposed; single-RF scheme in which available spot-wise spectra are located so close that the entire spot-wise spectra can be covered by an FFT/IFFT with a reasonable number of FFT points, and multi-RF scheme in which the spot-wise spectra are located far away so that the entire spectra cannot be covered by an FFT/IFFT processor. Computer simulation confirms that the proposed scheme is effective in utilizing spot-wise spectra. Moreover, the proposed scheme is confirmed to be effective in enhancement of co-channel and inter-symbol interference immunity when the number of opportunistically available spot-wise spectra is increased.

Performance of 2.4GHz-band wireless LAN system using orthogonal frequency division multiplexing scheme under microwave oven noise environment

GHz-band wireless LAN system based on IEEE 802.11g standard has been taking a great attention as it provides the attractive features such as low cost and high speed transmis- sion rate up to 54 Mbps using Orthogonal Frequency Division Multiplexing (OFDM) transmission scheme. However, 2.4GHz radio frequency band is also used for Industrial, Scientifi ca nd Medical (ISM) devices, and the man-made noise leaked from ISM devices will degrade the performance of 2.4GHz-band wireless LAN system. In this paper, we investigate the performances of 2.4GHz-band Wireless LAN system based on IEEE 802.11g standard (IEEE 802.11g WLAN system) under microwave oven noise environment. Numerical results show that the performances of IEEE 802.11g WLAN system are much degraded by the influence of man-made noise emitted from microwave oven. I. INTRODUCTION