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adaptive array suppressing intersymbol interference based on frequency spectrum in OFDM system

ELECTRONICS AND COMMUNICATIONS IN JAPAN PART I-COMMUNICATIONS 2005年第10期88卷 35-44页

作者： Higuchi, K Sasaoka, H Doshisha Univ Kyotanabe 6100394 Japan

The adaptive array is an effective measure in OFDM systems against intersymbol interference caused by delayed waves outside of the guard intervals. In this paper, we studied a technique that suppresses only delayed waves outside of the guard intervals and not delayed waves in the guard intervals by examining the temporal changes in the amplitude spectrum of the received OFDM signal caused by intersymbol interference. This technique is applicable if the signal points of the modulation of each subcarrier have a constant amplitude, and can be implemented by a relatively simple circuit because control is possible without the need for a known reference signal and estimation of the transmission path. Here, we proposed a method that compares in the time domain because the configuration is simpler. We also proposed a method that emphasizes the error portions with respect to a reference signal and improves the convergence speed as a measure against the slower convergence speed due to the interference components included in the standard signal. The simulation results verified the effective operation of the proposed method in a static multipath environment and a Rayleigh fading environment assumed in mobile communications. © 2005 Wiley Periodicals, Inc.

关键词： OFDM adaptive array frequency spectrum blind control

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THE DIFFERENTIAL CMA adaptive array ANTENNA USING AN EIGEN-BEAMSPACE SYSTEM

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IEICE TRANSACTIONS ON COMMUNICATIONS 1995年第11期E78B卷 1480-1488页

作者： NISHIMORI, K KIKUMA, N INAGAKI, N Nagoya Inst of Technology Nagoya-shi Japan

This paper addresses approaches to enhancement of performance of the CMA (Constant Modulus Algorithm) adaptive array antenna in multipath environments that characterize the mobile radio communications. The cost function of the CMA reveals that it has an AGC (Automatic Gain Control) procedure of holding the array output voltage at a constant value. Therefore, if the output voltage by the initial weights is different from the object value, then the CMA may suffer from slow convergence because suppression of the multipath waves is delayed by the AGC behavior. Our objective is to improve the convergence characteristics by adopting the differential CMA for the adaptive array algorithm. First, the basic performance of the differential CMA is clarified via computer simulation. Next, the differential CMA is incorporated into the eigen-beamspace system in which the eigenvectors of the correlation matrix of array inputs are used in the BFN (Beam Forming Network). This BFN creates the optimum orthogonal multibeams for radio environments and works helpfully as a preprocessor of the differential CMA. The computer simulation results have demonstrated that the differential CMA with the eigen-beamspace system has much better convergence characteristics than the conventional CMA with the element space system. Furthermore, a modified algorithm is introduced which gives the stable array output voltages after convergence, and it is confirmed that the algorithm can carry out more successful adaptation even if the radio environments are changed abruptly.

关键词： adaptive array DIFFERENTIAL CMA EIGEN-BEAMSPACE SYSTEM MOBILE COMMUNICATION MARQUARDT METHOD STEEPEST DESCENT METHOD

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Novel DOA estimation method for HA adaptive array applicable to TDMA mobile satellite communication systems

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IEICE TRANSACTIONS ON COMMUNICATIONS 1998年第7期E81B卷 1535-1541页

作者： Kamiya, Y Nomoto, S Kobayashi, H KDD R&D Labs Radio Commun Lab Kamifukuoka Saitama 3568502 Japan Mie Univ Tsu Mie 5148507 Japan

The applications of adaptive arrays based on the digital beam forming technique are receiving wide attention. However, the adaptive control algorithm of the array antennas under TDMA systems is not well considered even though it requires particular consideration due to its intermittent bursts. In this paper, first, we propose a novel DOA (Direction of Arrival) estimation method which is suitable for TDMA bursts. Second, the HA (Howells-Applebaum) adaptive array based on the proposed DOA estimation method will be constructed for the terminals in the mobile communication systems using non-geostationary satellites. Then the performance of the DOA estimation method and the HA adaptive array will be examined through computer simulations and experiments.

关键词： adaptive array Howells-Applebaum TDMA DOA estimation digital beamforming

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A CMA adaptive array antenna system with a single receiver using time-division multiplexing

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IEICE TRANSACTIONS ON COMMUNICATIONS 2001年第6期E84B卷 1637-1646页

作者： Moriyama, E Kamio, Y Hamaguchi, K Furukawa, H Independent Adm Inst Commun Res Lab Yokosuka Kanagawa 2390847 Japan Natl Police Agcy Tokyo 1008974 Japan

We describe a simplified receiver structure having several receiving antennas (i.e., an adaptive array antenna system) and using time-division-multiplexing (TDM) signal processing. Three simplified receiver structures were investigated for use in the antenna system. To confirm the feasibility of using a TDM receiver, both a TDM receiver and a conventional adaptive array receiver were constructed for testing. In our proposed system, several repetitions of the constant modulus algorithm (CMA) are used to reduce co-channel interference (CCI). The frame format used for both receivers was the same as that of the personal handy phone system in Japan. The laboratory testing was done using a fading simulator to enable measurement of the bit error rate. The results are very promising and show the feasibility of the TDM receiver.

关键词： constant nodulus algorithm adaptive array cochannel interference time-division multiplexing

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Performance analysis of subband adaptive array in multipath fading environment

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IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES 2002年第8期E85A卷 1798-1806页

作者： Tran, XN Taniguchi, T Karasawa, Y Univ Electrocommun Dept Elect Engn Chofu Tokyo 1828585 Japan

Subband adaptive array (SBAA) has been realised as a promising method to perform space-time signal processing in mobile communications. Recently, several schemes of SBAA have been introduced. However, theoretical analysis of SBAA performance has been only limited to case of SBAA without using decimation. In this paper, we introduce a novel method to analyse the performance of SBAA using critical sampling with localised feedback scheme. We first provide a detailed analysis of the SBAA performance in the case of single path and multipath fading environment. The simulation results are then presented to verify the proposed method.

关键词： subband processing adaptive array space-time processing multipath fading mobile communications

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Performance and configuration of M-CMA (modified constant modulus algorithm) adaptive array using polyphase filters

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ELECTRONICS AND COMMUNICATIONS IN JAPAN PART I-COMMUNICATIONS 2002年第12期85卷 53-64页

作者： Denno, S Ohira, T ATR Adapt Commun Res Labs Kyoto 6190288 Japan

As a way to realize an adaptive array of small size, low cost, and low power consumption, there exists a configuration method combining analog signal processing and digital signal processing. M-CMA has been proposed as a control algorithm for such an approach. However, when this approach is applied to an actual communication system, there arises the problem that the narrow-band filter in the receiver prevents M-CMA from converging to the desired solution. In this paper, in order to effectively operate an M-CMA adaptive array in the presence of a narrow-band filter, a configuration is proposed in which polyphase filters are used as narrow-band filters. Its superior interference suppression capability is confirmed by a theoretical analysis and computer simulation. (C) 2002 Wiley Periodicals, Inc.

关键词： adaptive array blind algorithm perturbation polyphase filter

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A novel adaptive array utilizing frequency characteristics of multi-carrier signals

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IEICE TRANSACTIONS ON COMMUNICATIONS 2000年第2期E83B卷 371-379页

作者： Fujimoto, M Nishikawa, K Shibata, T Kikuma, N Inagaki, N Toyota Cent Res & Dev Labs Inc Aichi 4801192 Japan Nagoya Inst Technol Nagoya Aichi 4668555 Japan

A novel algorithm for an adaptive array that is suitable for a multi-carrier transmission will be proposed in this paper. In an adaptive array, signals received by antenna elements are weighted and combined together. In the proposed algorithm, distortion of a spectrum of the combined signal is detected and weight coefficients for each antenna element are controlled so that the spectrum of the combined signal becomes hat. Concept of the proposed algorithm can be interpreted as the CMA which is applied to signals sampled in the frequency domain. Furthermore, a configuration of the adaptive array will be shown. Signals separated in a receiver of the multi-carrier transmission are utilized to detect the distortion of the signal spectrum. By adopting the proposed configuration, the spectrum of the multi-carrier signal can be easily detected. In order to investigate the performance of the proposed adaptive array, computer simulation has been carried out. Numerical results show that;1) A desired wave is captured well even if an interference wave is narrow band signal and is stronger than the desired wave. 2) Suppression performance for a co-channel interference wave depends on both a symbol timing and SIR of arrival waves. If the symbol timing of the interference wave greatly differs from the timing of FFT window of the receiver, the desired wave can be captured even if the co-channel interference wave is stronger more than 10 dB compared with the desired wave. The conventional CMA adaptive array has a serious problem that the narrow band interference wave is captured when it is stronger than the desired wave. On the other hand, it is extremely rare that the proposed adaptive array captures the narrow band interference wave. Therefore, it can be said that the proposed adaptive array is a robust system compared with the conventional system.

关键词： adaptive array mobile communication multicarrier CMA

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Signal space whitening MLSE with a multibeam adaptive array

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IEICE TRANSACTIONS ON COMMUNICATIONS 2003年第9期E86B卷 2592-2599页

作者： Hanaki, A Ohgane, T Ogawa, Y Hokkaido Univ Grad Sch Engn Sapporo Hokkaido 0608628 Japan

Cochannel interference and multipath propagation reduce the performance of mobile communication systems. Multi-input MLSE with whitening processing can mitigate the influence of the interference and provide path diversity gain. In conventional considerations, however, the required complexity rapidly rises with the number of array elements. In this paper, we propose multi-input MLSE that whitens error signals in the signal space by using a multibeam adaptive array. This scheme can reduce the computational load of multi-input MLSE than the conventional type when using a large-element array. The results of an analysis show that the proposed type is equivalent to conventional one in the sense of the metric and provides less computational complexity.

关键词： adaptive array interference suppression maximum likelihood sequence estimation spatial-temporal equalization

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MMSE adaptive array suppressing only multipath waves with delay times beyond the guard interval for fixed reception in OFDM systems

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ELECTRONICS AND COMMUNICATIONS IN JAPAN PART I-COMMUNICATIONS 2004年第9期87卷 1-8页

作者： Hori, S Kikuma, N Inagaki, N Kojima Press Ind Co Ltd Antenna Engn Dept Aichi 4700207 Japan Nagoya Inst Technol Fac Engn Nagoya Aichi 4668555 Japan Nanzan Univ Fac Math Sci & Informat Engn Dept Informat & Telecommun Engn Seto 4890863 Japan

It is known that OFDM transmission systems give better performance than single-carrier systems in a multipath environment. However, the communication quality degrades rapidly when the delayed wave arrives beyond the guard interval. In order to solve this problem, various systems that try to suppress the undesired wave by using an adaptive array have been proposed. This paper considers fixed reception and investigates an MMSE adaptive array for OFDM that does not suppress waves arriving within the guard interval, only waves arriving beyond the guard interval. More precisely, the SMI optimization method is proposed in which a window function is used to extract only the wave components beyond the guard interval. In order to demonstrate the effectiveness of the proposed system, an evaluation is made by computer simulation. It is shown that the system operates well as an MMSE adaptive array in a fixed reception environment, exhibiting high suppression power for delayed waves beyond the guard interval. (C) 2004 Wiley Periodicals, Inc.

关键词： OFDM adaptive array guard interval MMSE fixed reception

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A study of a blind multiple beam adaptive array

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IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES 1998年第6期E81A卷 1270-1275页

作者： Song, S Choi, Y Aizawa, K Hatori, M Univ Tokyo Fac Engn Tokyo 1138654 Japan

In land mobile communication, CMA (Constant Modulus Algorithm) has been studied to reduce multipath fading effect. By this method, the transmitted power is not used efficiently since all the multipath components have the same information. To make use of received power efficiently, we propose a Blind Multiple Beam adaptive array. It has the following three Feature points. First, we use CMA which can reduce the multipath fading effect to some extent without training signal. Second, LMS algorithm which can capture the multipath components which are separated from the reference signal by some extent. Third, we use FDF (Fractional Delay Filter) and TED (Timing Error Detector) loop which can detect and compensate fractional delay. As a result of utilizing the multipath components which is suppressed by CMA, the proposed technique achieves better performance than CMA adaptive array.

关键词： adaptive array CMA LMS multibeam array multipath fading

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