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When an adaptive array antenna is used in cellular and other mobile communication base stations for the purpose of improving SINR, the array antenna itself sometimes falls into a fading valley, resulting in failure to obtain an adequate improvement effect. While this problem can be solved by increasing the aperture length of the array antenna, simply increasing the aperture length alone increases the number of antenna elements, so that a large-scale adaptive array antenna becomes required, leading to the problem of failure of the weighting to track changes in the environment during fast fading. In this paper, we try to solve the first issue by making the element spacing nonuniformly aligned, reducing the number of elements. For the second issue, the weighting is divided into two layers, resolving the problem through both use of MMSE to eliminate interference and use of EGC for diversity combining. In a slow fading environment, however, favorable characteristics can be obtained when the entire weighting is controlled by MMSE. In this paper, we estimate the fading speed by the amount of envelope fluctuation in the desired signal after elimination of interference by the initial layer MMSE, and propose during slow fading the use of MMSE batch control, and during fast fading a control that incorporates both MMSE and EGC diversity combining. Finally, we use a computer simulation to evaluate the validity. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(12): 13–21, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20397 [ABSTRACT FROM AUTHOR]

The paper discusses flight-path planning for an aircraft flying at low altitude while avoiding terrain crashes,. In a past study, several algorithms based on exploratory procedures have been proposed; however, they do not generatye practical path that take into account aircraft practical pathe that take into account aircraft inertia. This paper proposes a new algorithm to generate a flight path taking account of the aircraft's inertia; this algorithm does not generate the flight path directly, but determines the aircraft's staring acceleration at every point along the way and then generates the flight path based on the steering acceleration. This algorithm extracts feature perimeters repreenting a relation between the aircraft and the terrain, determines steering acceleration by fuzzy reasoning using the feature parameters, and updates state variables of the aircraft. Furthermore, this paper also proposes a learning algorithm to design the membership values in the fuzzy resoning from reference flights since it is difficult to optimize them by trial and error. The flight-path planning by the proposed algorithm is corporate with that bested on the exploratory procedure. The learning algorithm of the membership values is validated through computer simulations. [ABSTRACT FROM AUTHOR]

The control of the cell contention is a technical problem in the input queueing ATM cross-connect switch. This paper considers this problem and proposes a scheduling control method which dynamically assigns the cell transmission time. A construction of the distributed scheduling circuit also is proposed based on Batcher's sorting network. The proposed method processes the cells in the order of their arrivals, as in the conventional three-phase algorithm but has an advantage in that the throughput can he increased by approximately 26 percent without increasing the number of control processes per cell. Mother merit is that multirate ports can directly be contained in the switch. In this paper, the approximate model for the proposed method is constructed, and the mean delay and the cell loss probability are calculated theoretically. The actual operating performance is evaluated by a computer simulation. By combining the proposed method with the conventional self-routing spatial switch, a distributed switching circuit can he constructed as a whole, which is useful in developing an economical large- capacity ATM cross-connect switch. [ABSTRACT FROM AUTHOR]

This paper considers the highly efficient coding of the gray-level image. The extrapolative prediction-discrete sine transform scheme, which was previously proposed by the authors for the case of one-dimensional coding, is extended to the case of two-dimensional coding. In the proposed method, the image is partitioned into square blocks. The correlations among blocks are eliminated by applying the two-dimensional extrapolative prediction for each block from the restored boundary pixel. The correlations the block is eliminated by applying the orthogonal transformation to the prediction errors. In this paper, the correlation function of the image is assumed as the isotropic exponential function, and a two-dimensional extrapolative prediction method is derived, which can be realized as a simple manipulation. The transformation of the prediction errors is performed by the variable-separation type two-dimensional extrapolative prediction-discrete sine transform, where the one-dimensional extrapolative prediction-discrete sine transform is applied to rows and columns. Then the rate-distortion characteristic is calculated, indicating that the proposed method is useful. It is shown that the proposed method with 4 × 4 block size has almost the same coding efficiency as the discrete cosine transform coding with 16 × 16 block size. A computer simulation was made for the actual image, leading to a result validating the theoretical estimation. The proposed method requires less computation per pixel, compared with the discrete cosine transform coding. The method is especially useful from the viewpoint of hardware implementation, since the block size is as small as 1/16. [ABSTRACT FROM AUTHOR]

In this paper, a layered network that interconnects a distributed queue subnetwork with another distributed queue bridge network is considered. As slot control scheme in this network, a loopback retransmission scheme preventing slot discarding and an adaptive node load control function are proposed. In the communication within the subnetwork, no transmitted slot is discarded during processing. However, it is necessary to consider protection against discarding due to buffer overflow in the bridge of the distributed queue bridge network interconnecting the subnetworks. In order to prevent reduction of slot use efficiency caused by discarding in the bridge, it is desirable to eliminate discarding. Also, in order to prevent discarding of slots arriving at the bridge from the subnetworks, slot transmission at each node must be controlled. In this paper, in order to prevent slot discarding caused by buffer overflow of the bridge, a method is proposed for loopback retransmission of the slot on the bridge network or subnetwork. It is shown that discarding can be eliminated. Also, the effectiveness of the method is confirmed by computer simulation. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(11): 35–45, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20267 [ABSTRACT FROM AUTHOR]

In multicast delivery in a network environment with various bandwidth limitations, it is effective to apply the layered multicast technique, which realizes delivery at a reception rate matched to each receiver, although the rate is set discretely. This paper assumes a multimedia session such as a multichannel broadcast or a video conference, composed of multiple streams. In such an application, it is desirable from the viewpoint of efficient use of bandwidth that not only should the streams be transmitted with stable quality, but that the rate should be assigned according to requests, such as attention to the speaker. However, it is difficult to achieve the above goal by directly applying the conventional layered multicast rate control technique, since each stream controls the rate independently. From such a viewpoint, this paper presents a session level mechanism covering multiple layered streams. A multiple streams controller (MSC) is introduced into each receiver, and each MSC autonomously controls the reception rate with interstream coordination in the session. The MSC monitors the reception state of the multiple streams simultaneously and estimates the bandwidth information on the bottleneck link and the set of transiting streams, based on the detected congestion data. Based on the estimation, the learning efficiency of the reception rate is improved and rate assignment control over the streams is applied. An evaluation is performed by computer simulation, and it is shown that the reception quality of the stream is improved by applying the proposed method, and that the reception rate can be coordinated among the streams. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(8): 18–31, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20142 [ABSTRACT FROM AUTHOR]

In reliable multicast, the same information is transmitted to specified receiving nodes while maintaining reliability, with the information rate aligned to the receiving node with the lowest throughput by end-to-end control. However, the consideration of the receiving node with the lowest throughput produces the problem that other receiving nodes belonging to the same multicast group are limited to a considerably lower throughput than their own reception limits. This is a problem inherent to multicast communications, where the receiving nodes generally differ in congestion status. This fairness problem for receiving nodes is called intrasession fairness. In reliable multicast, it is impossible to realize intrasession fairness by using only end-to-end control. The purpose of this paper is to realize intrasession fairness by a scheme in which servers independently apply congestion control to the downlink by placing servers in the network and providing network support. The proposed scheme is evaluated by simulation. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(2): 61–70, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10125 [ABSTRACT FROM AUTHOR]

It is well known that a large spike error and a bias error occur in the monopulse angle measurement process (of height estimation due to sea surface reflection or road surface reflection) when height estimation of a low-altitude target is carried out with an air traffic control radar or a tracking radar with a monopulse antenna. In this paper, a target height estimation method is proposed that can seek the estimation object with only one parameter of the target height, even if fading prevention by frequency hopping and a subarray configuration of the array antenna based on the maximum likelihood estimation method is used. By means of computer simulation, the S/N dependence and equivalent earth radius error dependence of the target height estimation error are evaluated when the conventional ΣΔ monopulse method, the maximum likelihood estimation method without frequency hopping for four subarrays, and the proposed maximum likelihood estimation method with frequency hopping are used. Even though the evaluation is within the limited conditions, it is confirmed that the proposed method can estimate the target height while fading prevention is attempted in a multipath environment. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(11): 39–48, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10208 [ABSTRACT FROM AUTHOR]

This paper considers the application of optical wireless communications to mobile communications. We consider an optical mobile communications system using cycle emission cells and allowing a reduction of the shadowing effect, which is a problem in optical wireless communications. The proposed system uses multiple transmitters with cycle emissions (DTCE). By varying the number of transmitters, the error rate performance is compared via computer simulation. It is anticipated in particular that when the proposed method is applied to mobile communications, multiple transmitters will be placed in the service area, and the distance between the transmitters and the synchronization among the transmitters will greatly affect the error rate performance. The performance is calculated by varying these parameters via computer simulation, and the results are evaluated. Furthermore, the result is compared to other models which have been proposed in order to reduce the shadowing effect, and the effectiveness of the DTCE system regarding optical wireless mobile communications is demonstrated. [ABSTRACT FROM AUTHOR]

Recent research has shown that long-range dependence is found not only in network traffic volume, but also in the propagation delay time of packets. The round-trip propagation time of packets, which is known as the round-trip time (RTT), is one of the most important parameters for determining TCP performance. The ability to understand its characteristics can contribute to an improvement in TCP performance. Therefore, in this paper, to determine the impact of the long-range dependence of the RTT on TCP performance, the authors looked at the two congestion control phases known as congestion avoidance and slow start in TCP window control and used computer simulations to evaluate performance. First, the evaluation related to the impact on the congestion avoidance phase showed that higher long-range dependence and larger transfer files caused greater variability in the file transfer completion time. Next, the evaluation related to the impact on the slow start phase, which evaluated the impact of the long-range dependence of the RTT on the TCP retransmission timeout (RTO), showed that higher long-range dependence causes unnecessary timeouts, which end up causing the resending of packets that have not actually been lost, to occur more frequently. The authors also performed investigations for mitigating the impact of the long-range dependence of the RTT and made a number of modifications to the existing RTO estimation algorithm to show that TCP performance can be improved. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(6): 52–60, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10073 [ABSTRACT FROM AUTHOR]

In this paper, we discuss techniques for transmitting signals over the same frequency by synchronizing multiple base stations in order to achieve both high communication quality and excellent spectral efficiency in broadcast (P-MP: Point to Multipoint) communication (single-frequency, multistation simultaneous transmission). Specifically, in this paper, we propose a communication technique that uses the concept of transmission diversity and converts beat interference to intersymbol interference to suppress beat interference, which becomes a problem in single-frequency, multistation simultaneous transmission. The proposed technique features (1) controlling the transmit timing or waveform of the signal transmitted from each base station, and (2) using an adaptive equalizer to compensate for intersymbol interference produced during transmission. Finally, we assume a high-speed Rayleigh fading environment in addition to a beat interference environment in computer simulations and demonstrate the effectiveness of the proposed technique when maximum likelihood sequence estimation based on per-survivor processing is adopted. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(6): 12–21, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10167 [ABSTRACT FROM AUTHOR]

When tracking radar is used for tracking a low-altitude target, fading due to multipath propagation consisting of the direct wave and the waves reflected from the sea surface (or the ground) is generated so that tracking becomes difficult. In this paper, as a remedy to this problem, a space-frequency maximum-ratio combining method is proposed that combines frequency hopping with an array antenna. In order to reduce the size of the transmission and reception system, and also to reduce the computational overhead for maximum-ratio combining, a subarray configuration is used for the array antenna and the maximum-ratio combining is applied to the subarray. By means of computer simulation, the effects of the space-frequency maximum-ratio combining in the full DBF and in the subarray configuration are compared. It is confirmed that a power level higher than that in free space can be obtained by the proposed method under the constraint of a distance of 5000 to 40,000 m for a target at an altitude of 100 m (constant) by letting the frequency hopping range be 20%. It is also confirmed that the diversity gain degradation due to the subarray configuration is small. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(5): 75–85, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10143 [ABSTRACT FROM AUTHOR]

Ad hoc networks have excellent capabilities for data transmission in an environment with an incomplete communications infrastructure, and in mobility and portability of terminals. Routing protocols between terminals in an ad hoc network can be broadly divided into location-aware routing, based on location information on the terminals, and non-location-aware routing, which is not based on location information. In the former, routing can be made accurate and easy by effectively utilizing location information. Hitherto, the use of the global positioning system (GPS) has been most often treated as the means of acquiring terminal location information. However, in location estimation by GPS, electromagnetic waves from multiple location estimation satellites must be received, and the method cannot be applied effectively in an environment in which that condition is not satisfied. This paper proposes the following method of location estimation. Fixed access points whose absolute locations are already known are placed in the network. Then, by using self-organizing maps (SOM), the mutual location information among the terminals is organized, and the location of the home terminal is successively inferred. The feasibility and accuracy of estimation in the proposed method are examined by a computer simulation. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(4): 73–81, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10098 [ABSTRACT FROM AUTHOR]

Research and development have been carried out extensively on the MUSIC and ESPRIT algorithms, based on the eigenfunction expansion of the correlation matrix, for high-resolution direction-of-arrival estimation using array antennas. A factor hindering the best performance of these high-resolution algorithms in real array antennas is nonuniformity of the element patterns caused by element coupling in an array configuration. In this paper, it is assumed that the array antenna is operated in a single mode and that the initial deviations of the transmitted amplitude and phase of the feed system and errors such as interelement coupling can be represented by a single coupling matrix with complex elements. Under such assumptions, this paper proposes a method for compensating the error of the center of rotation of the rotating table on which the device under test for calibration data measurement is installed, and estimates the coupling matrix. By computer simulation in the case of a receiving array antenna, it is found that the coordinates of the rotating center and the coupling coefficient can be estimated and that received signals with the initial deviation and interelement coupling compensated can be obtained by multiplying by the inverse of the coupling matrix estimated for the received signals. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(3): 59–73, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10126 [ABSTRACT FROM AUTHOR]

This paper proposes a method which reduces the peak-to-mean power ratio (PMPR) of the multicarrier modulation signal by providing a subcarrier for peak power reduction outside the information band. The proposed method includes the addition of a redundant signal, that is, parity carrier, in order to reduce the peak power of the multicarrier signal when its envelope exceeds a given threshold. The parity carrier for peak power reduction is placed outside the band of the multicarrier signal and can be easily removed in the receiver. It is shown by a computer simulation that when two carriers for peak power reduction are added to the multicarrier signal with eight carriers, the PMPR after the peak power reduction approaches 4.7 dB. It is also shown for the case in which the power amplifier has little nonlinearity that an outband spectrum density of -50 dB can be achieved by applying the proposed method for a back-off of 4.7 dB. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 85(8): 34–46, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1116 [ABSTRACT FROM AUTHOR]

In reservation radio packet transmission protocols, non-collision packet reservation multiple access (NC-PRMA) is known to be able to transmit packets without any collision and to attain higher throughput than packet reservation multiple access (PRMA). However, so far only NC-PRMA in voice-only traffic has been studied. In this paper we evaluate NC-PRMA in integrated voice and data traffic. First, considering data terminals, we formulate an equilibrium point analysis by guaranteeing the number of slots for data packet transmission in one frame. The number is decided according to the number of terminals. Next, we evaluate the throughput and the voice packet dropping probability by theoretical analysis and computer simulation. It is shown that in integrated voice and data traffic NC-PRMA attains better throughput and voice packet dropping probability than PRMA. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 84(12): 13–21, 2001 [ABSTRACT FROM AUTHOR]

CMA adaptive arrays operate well and have an excellent unwanted wave suppression capability if the desired signal has a constant envelope characteristic. Therefore, their application to mobile communication is expected. However, although no prior knowledge of the reference signal is required in CMA, it is not possible to predict which signal is acquired if other arriving waves have constant envelope characteristics. Therefore, there is a possibility that an interference wave arriving from a completely separate source may be acquired in error. Therefore, in order to constantly guarantee the communication quality, the acquisition characteristic for the desired wave needs to be improved. As a plan for improvement, this paper sets a constraint to protect the desired wave by means of the cyclostationary properties of the modulated signal and proposes a correlation constrained CMA adaptive array based on incorporation of this constraint into CMA. The acquisition characteristics of the desired wave and the unwanted wave suppression capability are studied by means of a computer simulation, and the effectiveness of the proposed system is confirmed. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 84(4): 48–56, 2001 [ABSTRACT FROM AUTHOR]

An efficient scheme for establishing a multicast route in packet networks is constructing a tree-shaped path in which multicast packets are replicated at specific branching nodes, called “copy nodes,” by the packet copy function and are forwarded to downstream nodes. This scheme leads to the efficient usage of network resources, but needs multicast routing control. To realize rapid multicast routing, it is suitable and realistic to restrict the number of copy nodes in calculating the multicast route. However, even in this approach we need to adequately select a limit on the number of copy nodes which satisfies the conditions of both priority for multicasting and geographical distribution. In this paper, a new copy-node allocation algorithm is proposed. This heuristic algorithm makes some “copy node functions” move on the network map sequentially according to attraction and repulsion determined by several conditions and finally makes them converge on the switching nodes suitable as copy nodes. In addition, the performance of this algorithm is evaluated by a computer simulation. This algorithm is applicable to various other server assignment problems. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 83(1): 87–96, 2000 [ABSTRACT FROM AUTHOR]

This paper discusses a method in which a wave source is visualized by electromagnetic wave holography by scanning the receiver antenna on a plane. The method presented in this paper does not use the Fresnel approximation or the Fraunhofer approximation, and there is no constraint on the distance between the measuring plane and the object of observation. By partitioning the object of observation, the method can be applied, even if the object of observation is larger than the hologram measuring plane. The two-dimensional fast Fourier transform is introduced to each of the partitioned planes, so that the speed of the numerical integration is improved. To improve the accuracy of the intensity of the reconstructed image, the directivity of the receiving antenna is considered. For observation of the leaked electromagnetic wave in a real system, a hologram observation system is proposed in which some variation of the observation frequency can be tolerated. Using the proposed observation system, the radiation from a dipole antenna is observed, and a computer simulation is performed. These results show that the resolution is improved and that a wider range of observation is realized than in the conventional method. Lastly, as an application example, the leaked electromagnetic waves from a metal cabinet are observed on a 57 cm × 57 cm plane at a distance of 200 cm, and a visualized result for 285 cm × 285 cm is presented. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(8): 52–60, 1999 [ABSTRACT FROM AUTHOR]

Backpressure control is one of several effective traffic control schemes for ATM-LAN. Comparing an input queuing switch with an output queuing switch, backpressure control in a congested input queuing switch has the ability to selectively control the output port of the front stage of the input queuing switch. This paper compares an input queuing switch with an output queuing switch for single and multiple stage configurations by using a computer simulation. The output queuing switch controls all the output ports of the front switch. The input queuing switch, however, can selectively control the congested output port of the front switch. This paper evaluates and compares the performance of the switches for burst traffic. © 1998 Scripta Technica. Electron Comm Jpn Pt 1, 81(7): 38–46, 1998 [ABSTRACT FROM AUTHOR]

This paper consider the performance of traffic capacity and handover frequency in a DS/CDMA system under imperfect handover. The effect experienced when the number of base stations observed by the personal station is restricted is estimated. Furthermore, the effect of handover hysteresis also is considered. Simulation models are presented which can evaluate the traffic capacity and the handover frequency under these imperfections. System performance is evaluated by computer simulations using these models. It is found that if the number of observed base stations is 3 and the standard deviation of short-distance medium value variance is 6 dB, the reverse-link traffic capacity is reduced to about 90 percent and the forward-link traffic capacity is reduced to about 85 percent, while the handover frequency is about 90 percent of the frequency of the short-distance medium value variance. It is found also that if the handover hysteresis is 4 dB and σ is 6 dB, the reverse-link traffic capacity is reduced by about 10 percent while the handover frequency is about 10 percent of the frequency of the short distance medium value variance. [ABSTRACT FROM AUTHOR]

This paper proposes a high-accuracy positioning service for terrestrial mobile communication systems which employs the global positioning system (GPS) with the differential method (DGPS). The proposed system provides a high-accuracy navigation service to land-based mobile communication users. The proposed system also provides a comprehensive vehicle control service to the transportation companies when both forward and return links are available in the terrestrial-based mobile communication systems. This paper also assesses the performance of the DGPS method by computer simulations and a field experiment in an urban area to identify the viability of the proposed system under an actual environment. The relationship between average hinging time rate and the average visible number of satellites in various operating environments also is investigated. [ABSTRACT FROM AUTHOR]

This paper discusses the multipath allocation problem in the communication network and proposes a multipath allocation algorithm suited to the distributed environment. The multipath allocation problem is a problem where multiple paths arc to be allocated without a conflict. This problem has been difficult to solve in the distributed environment since relations among various routes must be considered. The algorithm proposed in this paper solves this point by realizing the asynchronous path search. In this paper, the basic characteristics of the proposed algorithm are described through the comparison between the proposed and the traditional algorithms for the case of serial computation under the centralized control. Then the proposed algorithm is applied to several kinds of distributed cooperative multiagent models, and it is demonstrated that the proposed model can easily be applied to the distributed environment. A simulation is executed actually using several workstations, and it is shown that the proposed algorithm is desirable as a solution method for the multipath allocation problem m the distributed environment. [ABSTRACT FROM AUTHOR]

Multipath fading is a (actor degrading the communication quality in mobile communications. It has been reported that an adaptive array antenna can enable elimination of the effect of delayed signals by an appropriate control of the radiation pattern. In this paper, it is recognized that an optimum weight of the array antenna can be computed if the direction of arrival and the signal to-noise ratio of the received signal are known. By using the spatial frequency derived by the discrete Fourier transform (DFT) of the received signal which is spatially sampled by the array antenna, an algorithm is proposed in which the directions of arrival and the signal-to-noise (SN) ratio of the desired and interference waves are estimated and an optimum weight coefficient of the antenna is computed. This algorithm is different from those in the conventional adaptive digital filter algorithms such as the LMS algorithm. It requires no reference signal and can follow quickly changes in the communication channel. Further, a method is proposed to improve the estimation accuracy of the direction of arrival and the SN ratio with a limited number of elements by using the property of the DFT. To confirm the principle of the proposed algorithm, the basic characteristics are evaluated by computer simulation. [ABSTRACT FROM AUTHOR]

This paper investigates an adaptive equalizer with career frequency offset compensation for digital mobile radio transmission over several tens kbit/s. The performance of conventional adaptive equalizers for mobile radio severely degrades for receiving signals having carrier frequency offset which is mused by local oscillator frequency offset due to misadjustment, temperature dependence, and aging. Carrier frequency offset compensation for TDMA burst signaling requires both accurate and short-time measurements. However, both requirements have a trade-off relationship and must be optimized. This paper proposes the carrier-acquisition-during-training (CAT) algorithm for transmissions allowing a training signal. First, two basic configurations and their equivalence are discussed. Next, computer simulations and real-time experiments with one-chip DSP show the effectiveness of CAT by demonstrating training convergence, optimum parameter characteristics, and average BER performance under two-path selective fading with one-symbol delay difference and independent Rayleigh components. [ABSTRACT FROM AUTHOR]

Strong international effort has been made toward the realization of a B-ISDN based on ATM techniques. This paper proposes self-healing techniques for enhancing ATM network reliability. Self-healing is defined here as failed path restoration with distributed control mechanism by using cross-connects. First, the characteristics of virtual paths (VPs) are compared with those of digital paths in STM networks. It is clarified that VP benefits can be exploited for network restoration upon failure. Two high-speed self-healing algorithms that make the best use of VP characteristics are then proposed for restoring single-link failures. A technique for multiple-link failure restoration also is proposed. Finally, restoration performance is evaluated by computer simulation. It is confirmed that the proposed algorithm enables faster restoration than that possible using the existing algorithm for STM networks. [ABSTRACT FROM AUTHOR]

As the local area network (L.AN) becomes popular, LAN systems which cover wider areas and which resolve traffic concentration in the system are going to be needed. This paper analyzes a system which consists of a token ring LAN as the main network to which some CSMA/CD-LANs are connected with bridges. Such a system is called the "compound LAN system" in this paper. The optimum condition of this system due to the performance evaluation of the compound LAN system is shown by comparison with the throughput of each LAN. The results of analysis are confined by computer simulations. Moreover, the optimized scheme condition is confirmed by using the power function evaluation for the system. [ABSTRACT FROM AUTHOR]

As a technique for constructing the switch fabric in the ATM (asynchronous transfer mode) communication system, the self-routing switching network has been proposed where the buffered Banyan network is used as the distribution network as well as the routing network. The features of this kind of switch are that it is of a distributed structure, being suited to the modular construction, the large capacity system can easily be realized, and the performance is stable for diversified traffic. On the other hand, it has a problem in that the order of the transmitted information (cells) is not preserved. This paper proposes anew a switch construction with time stamps attached to the cells. The cell sequence is preserved by controlling the sequence of the time stamps, and the system can be controlled in a distributed way. The feature of the method is that the cell sequence is preserved while maintaining the self-routing property of the traditional multistage buffered switch. Also, the principle and the optimal construction are described. Basic system parameters such as the required wurd length for the time stamp signal are determined. The delay characteristics of the proposed system for various kinds of traffic are evaluated by a computer simulation. [ABSTRACT FROM AUTHOR]

The satellite-fed millimeter-wave personal communication system that is described requires a satellite with a multi-beam antenna in order to guarantee the required link availability in point-to-point communications between numerous widely distributed small Earth stations. The usual method of antenna beam allocation requires high beam power in the downlink, giving rise to realizability problems due to limitations on the output power of the millimeter-wave transmitter. This paper proposes an approach to optimizing the allocation of downlink antenna beams in which the beams are assigned to service areas that are chosen with reference to population distribution, rainfall attenuation in the millimeter-wave region, and constraints on beam power. A computer simulation based on nationwide rainfall attenuation and population distribution data indicates that the proposed approach is more effective than with the usual beam allocation method. The equipment configuration of the satellite is described. [ABSTRACT FROM AUTHOR]

Newtonm's method is well known for finding the fixed point of the Poincaré mapping for steady-state analysis of nonlinear oscillatory circuits. However, in particle, quadratic convergence of this method is not ensured due to the discretization error of the numerical integration and the errors of the approximate solutions for nonlinear equations which are solved at each time-step of the numerical integration. This paper proposes a new method for the steady-state analysis of nonlinear nonautonomous and autonomous systems which takes account of the numerical integration error stated above. In this method, the system of equations which includes a Poincaré mapping is discretized and reexpressed is a system of finite difference equations to which an iterative decomposition method is applied. Although this approach is essentially equivalent to the environment Newton method based on the Poincaré mapping, it has the advantages that the Jacobian matrix can always be computed exactly for an arbitrary time-steplength and that the local quadratic convergence of the algorithm is guaranteed. Considering these advantages, this paper also proposes a strategy to improve the computational efficiency of the algorithm in which initially, a large time step is used to find a rough solution which is then used as the starting value in the subsequent Newton iteration. Numerical examples are given to verify the relevant theorems and to show the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Satellite communications is suitable for multicast communications which can achieve one-to-many delivery because it can broadcast to multiple receiving stations over a wide area. However, packet retransmission is inefficient for satellite communications because of its large delay and bit error rate. In order to avoid packet retransmission, FEC (forward error correction) exploiting error correcting codes have been put to practical use in satellite multicasting. Tornado-type codes are well known as a kind of error correcting codes suitable for multicasting. Tornado-type codes are encoded and decoded in packets. As a result, they are effective for combatting packet losses by buffer overflow or congestion control. Furthermore, their coding and decoding have low time complexity. On the other hand, the bit errors in the packet are processed as a packet loss in decoding because the Tornado-type codes are decoded packet-wise. In this paper, we propose an effective decoding method for bit errors in the packets for Tornado-type codes. We show by computer simulation that the proposed method is effective in bit error environments. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(10): 57– 66, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20361 [ABSTRACT FROM AUTHOR]

Deflection routing is considered as a method to avoid packet collisions in an optical packet switching system. Deflection routing is a method of avoiding collision by link substitution, in which the colliding packet is sent to an idle link. Thus, the load on the congested part of the network is distributed and the bandwidth can be utilized effectively. When excessively frequent deflections are performed, however, the load on the whole network is increased, which produces an adverse effect. Another problem is that sequence errors can occur in the same flow due to differences of transmission delay, since packets are sent to different routes. From these points of view, this paper proposes a deflection control method which can remedy the above problems, and applies the proposed method to an optical packet switching system. In the proposed control method, class separation is performed with respect to sequence error, and deflection is permitted to packets of nonpriority class. This improves performance by large-scale grouping. In order to alleviate the increase in load on the whole network, a control algorithm which can deal with changes of the link utilization and the number of traversed hops is devised. The effectiveness of the approach is shown by computer simulation. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(9): 67– 77, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20312 [ABSTRACT FROM AUTHOR]

This paper investigates an intervehicle communication method as a safe driving support system for intersection collision avoidance warnings. In this kind of system, realization of highly reliable communications in the physical layer is an absolute requirement. As a result, we propose a new MIMO-STBC (Space-Time Block Coding) method based on intersection propagation channel characteristics. MIMO transmission characteristics are determined by the propagation channel characteristics. First, we use a ray-tracing method simulation to clarify the propagation channel conditions, and then model the intersection propagation channel. We use the characteristics of this propagation channel to propose a MIMO-STBC method that utilizes decision feedback channel estimation, and verify the effectiveness of the proposed method in computer simulations. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(9): 1–15, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20400 [ABSTRACT FROM AUTHOR]

A generalized mode vector that simultaneously uses the differential coefficient component of the mode vector has been proposed for estimating the direction of arrival of incident waves having angular spread. In this paper, the authors first examined this generalized mode vector and proposed a gradient-type MUSIC algorithm that uses the differential coefficient component of the mode vector independently for estimating the direction of arrival. Then they used a computer simulation in which the waves having angular spread were considered to be a group of scattered waves to compare this algorithm with regard to the performance for estimating the direction of arrival with an integral-type MUSIC algorithm that uses simple integration, which they proposed separately. To improve the estimation precision degradation that occurs when the signal correlation is low among scattered waves that exist within the angular spread when using the integral-type MUSIC algorithm, the authors proposed a combined-type MUSIC algorithm that incorporated the gradient-type MUSIC algorithm in the integral-type MUSIC algorithm and used this to examine the performance for estimating the direction of arrival and angular spread again. The results of the comparison of the gradient-type MUSIC algorithm and integral-type MUSIC algorithm confirmed that the two algorithms have conflicting properties related to the signal correlation among scattered waves that exist within the angular spread. Also, the investigation related to the combined-type MUSIC algorithm indicated that estimation precision degradation that occurs when the signal correlation is low among scattered waves when using the integral-type MUSIC algorithm was reduced as expected. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(6): 53– 64, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20208 [ABSTRACT FROM AUTHOR]

Cellular mobile communications require the detection of received levels at mobile stations so that the positions of the mobile stations can be detected. Given that paths can be isolated in the broadband DS-CDMA method, the technique generally used is RAKE reception, and improvements in detection accuracy due to the path diversity effect can be expected. This paper discusses the application to the DS-CDMA technique of a method in which the average reception power is estimated from N reception levels (the true value) obtained by sampling at a certain time interval ΔT in a mobile communication environment in which the reception voltage changes dynamically as the mobile unit runs. First, we perform a theoretical analysis of the detection accuracy of the received level in a general reception model that simultaneously takes both antenna diversity and path diversity into consideration, and then we demonstrate the plausibility of the theoretical analysis by means of computer simulations. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(2): 58–71, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20217 [ABSTRACT FROM AUTHOR]

In forward-looking radars such as automotive radars, it is necessary to suppress the reflected undesirable signal (clutter) from such objects as the ground surface (especially hills), guard rails, and buildings, in order to detect moving targets ahead. When using a pulse-Doppler filter (PDF), which is the conventional method for clutter suppression, separation is difficult when the velocity of the target relative to the clutter is small. In this paper, as a high performance clutter suppression method for such low-velocity targets, we propose element-localized Doppler space time adaptive processing (ELD-STAP), which includes a PDF in the preprocessing, and which uses an array antenna. In the proposed ELD-STAP, only the PDF output corresponding to the Doppler frequency breadth of the clutter, predicted from the speed of the vehicle on which it is mounted, is selected for applying STAP, and hence the dimension of the data vector, which is the greatest difficulty in the application of STAP, can be reduced. By reducing the dimension of the data vector, not only the computation load, but also the number of cells that must be referenced to estimate the clutter correlation matrix (called secondary cells), can be reduced. Computer simulation reveals that the proposed ELD-STAP yields an improvement factor better than that provided by the combination of PDF and multibeam forming (MBF). © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(1): 77–89, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20221 [ABSTRACT FROM AUTHOR]

MUSIC superresolution algorithm can estimate the DOAs (directions of arrival) of multiple waves closing less than the beam width. However, the MUSIC algorithm is usually applied to a DBF (digital beam forming) array antenna, and it was difficult to apply the method to scanning beam radar, which has simpler structure and lower cost than DBF radar. This paper proposes a MUSIC DOA estimation algorithm intended to improve DOA estimation performance by separating mixed signals in a scanning beam radar. In this paper, we assume a scanning beam radar transmitting and receiving FMCW modulated waves, which are often used for modulation. The principle of the proposed method is described. The accuracy and resolution of DOA estimation by the proposed estimation method are evaluated by computer simulation, and it is verified that a resolution 5 times as great as that of the conventional method can be achieved. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(10): 24–33, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20289 [ABSTRACT FROM AUTHOR]

To implement a one-cell reuse time division multiple access (TDMA) system using orthogonal frequency division multiplexing-based adaptive modulation scheme (OFDM AMS) and multilevel transmit power control (MTPC), co-channel interference [intercell interference (ICI)] from adjacent cells that varies dynamically on the frequency axis must be fed back very accurately to the transmitting station. Therefore, in this paper, we propose an ICI feedback technology in one-cell reuse TDMA with OFDM AMS/MTPC. First, the interference power of each subchannel is estimated by calculating the vector error which is the difference between the reference symbol on the receiving side and the received symbol. Next, instead of a digital signal method capable of expanding the amount of information, analog quadrature amplitude modulation (QAM) is adopted in order to feed back the errors with high accuracy. In addition, code division multiplexing (CDM) is adopted in order to improve the robustness to multipaths. Furthermore, to reduce the amount of feedback information, we adopt a method where the estimated interference noise power is formed into blocks by multiple adjacent subcarriers, and only the average of the block is set as the notification target, and interference power information less than some constant value is not notified. The evaluation results of the characteristics of the proposed method by a computer simulation verified that the interference noise power can be estimated very accurately and can accurately notify by using a notification frame with optimized power distribution. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(7): 11–23, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20281 [ABSTRACT FROM AUTHOR]

It is proposed to use the minimum product distance as the design criterion for a space-time trellis code (STTC) in a fast fading environment. Reference 1 discusses the minimum product distance for all error event paths. Reference 2, on the other hand, discusses the minimum product distance for the minimal error event path. This paper shows, as the first step, that by itself, the minimum product distance for the minimal error event path is not sufficient to evaluate correctly the frame error rate performance of STTC. Then it is shown that the minimum product distance for the error event paths that affect the error rate under consideration is fairly effective as a design criterion. It is further proposed to use the product distance distribution and the average trace of code word distance matrix for the minimal event path as design criteria for the STTC. A computer simulation demonstrates that the proposed design criterion is more effective than the conventional design criterion. A computer search based on the proposed design criterion shows that an STTC that achieves a better frame error rate performance than the conventional STTC can be discovered. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(11): 54–64, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20181 [ABSTRACT FROM AUTHOR]

The method of frame synchronization in which the acquisition time is drastically reduced by using multi-component code is well known. There is a danger in this method, however, that large acquisition delays may occur in a low C/N environment due to errors of the partial correlation values. The purpose of this paper is to apply a multi-component code to acquisition in an effort to improve the performance of TDMA systems. The operation of the proposed acquisition method and the acquisition time performance in a low C/N environment are evaluated by experiment, theoretical analysis, and computer simulation and guidelines for acquisition system design to achieve fast and stable operation are proposed. The S/N value at the correlator output required for realizing the desired performance is determined. It is also shown here that performance can be improved greatly by providing a correlation detector with hysteresis. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(5): 50–66, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20157 [ABSTRACT FROM AUTHOR]

In this paper, we propose a single inductor type resonant AC link snubber as a technique for introducing soft-switching PWM technology into three-phase voltage source inverters and explain its circuit operation. We then explain the suitability of instantaneous space voltage vector sinewave modulation compared to sinewave-triangle wave relative modulation as the sinewave modulation technique of the soft-switching inverter introducing this resonant AC link snubber, and propose a time sharing pulse pattern based on the operating principle of this resonant AC link snubber. Furthermore, we discuss the limits on the widths of the pulses that can be output when the time sharing pulse output method is used and the soft-switching inverter performs sinewave modulation, and the need to correct narrow output pulse widths; describe in detail the relationship between the generation principle of the correction pulse pattern and the waveform distortion; and illustrate the simulation results when the minimum pulse width is corrected. Finally, we propose a new time sharing pulse pattern that does not need the minimum pulse width correction by using the time sharing pulse pattern feature for the resonant AC link inverter and demonstrate its effectiveness from the simulation results for this output pulse pattern. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(2): 34–40, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20144 [ABSTRACT FROM AUTHOR]

This paper presents a broadband inverted F antenna realized by adding a wire element and describes a method for its design based on the operating principle. This inverted F antenna has a configuration with a wire element attached at the middle of the wire element already connected at the feed point. Broadband operation is made possible by a new method in which a parallel resonance antenna is combined with the wire inverted F antenna, which is a series resonance antenna. A design method is proposed in which matching at each resonant frequency is independently adjusted by means of these two different resonances. Its effectiveness is demonstrated by experiments and by a simulation by NEC2. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(11): 11–20, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10215 [ABSTRACT FROM AUTHOR]

We propose a new quantization method for received synthetic aperture radar (SAR) signals and a quantizer design technique. This method divides the received signal into bandlimited signals by using orthogonal wavelet transforms and quantizes each bandlimited signal by a different quantizer. Employing this method, not only is there a reduction in the computational load for image reconstruction by the SAR fast approximate reconstruction proposed previously by the authors, but the accuracy of the reconstructed image is substantially improved when there are few quantization bits of the received signal, particularly in image reconstruction by the correlation method. In this paper, we design a quantizer for bandlimited signals and demonstrate the effectiveness of the proposed method by computer simulations of image reconstruction. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(9): 54–63, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10182 [ABSTRACT FROM AUTHOR]

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. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(9): 1–8, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10221 [ABSTRACT FROM AUTHOR]

Rapid advances in recent device technologies continue to create ubiquitous computing environments that have wireless devices everywhere in the surroundings. Positioning devices such as the Global Positioning System (GPS) and pseudolite continue to decrease in price and wireless devices containing them can determine the location of the device itself. Given this background, providing services based on the location information of a device group, in other words, location-aware services, is currently an active topic. The location-aware services being widely researched today provide guide systems to users. A typical service is Intelligent Transport Systems (ITS). However, these services are not available in an environment where special positioning devices cannot be used, and the user must switch to another service. Existing services have the drawback of architectures that are greatly affected by the user's environment. Thus, in this paper, we propose seamless location-aware services that will improve on these conventional services. We present the problems of using existing methods as the routing protocol, which is an element technology of these services; propose and evaluate a method better suited to these services; and verify its effects by a computer simulation. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(4): 26–34, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10138 [ABSTRACT FROM AUTHOR]

In mobile ad hoc networks, performance is degraded by link breakage due to node mobility and packet collision due to network congestion. Therefore, it is very attractive to investigate routing protocols which use a routing metric to discover long-lived routes or to disperse network congestion instead of using hopwise shortest routes. In this paper, we examine three route selection schemes in a routing protocol which uses the link expiration time as a routing criterion. Furthermore, we present the Busy Node Avoidance Routing (BNAR) protocol that employs a busy rate representing the nodal load as a new route selection metric. Computer simulation results show the fundamental performance and effectiveness of routes based on the link state and node state. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(2): 68–78, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10137 [ABSTRACT FROM AUTHOR]

Use of dipole antennas for portable wireless transceivers has been attempted. In order to realize this application, it is necessary to add a matching network and a balun or a folded configuration. Hence, integration is found difficult. In this paper, a T-type monopole antenna with a parallel resonance mode is proposed. It is shown by simulation and measurement with a 2-GHz handset model that this antenna does not require any balun, is capable of self-matching, and can suppress unwanted radiation from the case as for a dipole antenna. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(2): 28–36, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10157 [ABSTRACT FROM AUTHOR]

In ATM (asynchronous transfer mode) we propose a VOQ (virtual output queuing) switch in which the same number of buffers as the number of output ports are provided in each input port, serving as an input-buffered switch to avoid HoL (head of line) blocking. In addition, in order to handle the recent increase of IP traffic, the IP-PIM (IP-parallel iterative matching) scheme is proposed as the scheduling scheme for the VOQ switch using variable-length packets. However, the IP-PIM scheme has the problem that the queue lengths in other buffers are increased, since cells belonging to the same packet are always handled continuously, which degrades the packet loss probability. Consequently, this paper proposes a scheduling scheme with active buffer priority in which the buffer receiving the cells belonging to the packet under consideration is defined as the active buffer and is given priority. In the proposed scheme, the queue length is reduced by giving the priority to the active buffer, and efficient switching is realized. The packet loss probability and the average packet delay are evaluated by computer simulation. It is found that the proposed scheme can greatly improve the packet loss probability compared to the conventional scheme, with degradation of the average packet delay by approximately 20 slots. It is also shown that a satisfactory loss probability is realized even if the buffer size is small, and that good expandability with regard to the switch size is achieved. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(2): 79–90, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10120 [ABSTRACT FROM AUTHOR]

An important problem of the adaptive array antenna proposed previously in regard to its installation is the increased equipment size. This is because the adaptive array antenna requires as many RF circuits as the number of antenna elements. In this paper, in the case where there is an input in one system, we study an adaptive array antenna with sequential processing (AAA-SP) in which the MMSE (minimum mean square error) criterion is used to control array weights by means of sequential processing of sampled signal data. Since there is only one input system in this case, it is found that the SINR is degraded due to reduction of correlation among elements if the conventional MMSE criterion is used as the adaptive control algorithm. Hence, in order to improve the deterioration of the SINR, a tapped-delay-line adaptive array antenna with sequential processing (TDL-AAA-SP) is proposed in which oversampling and a TDL-AAA are combined. It is theoretically proven that the TDL-AAA-SP improves the SINR by recovering from reduction of correlation by means of correlation on the time axis. A computer simulation demonstrates that the proposed scheme is effective. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(2): 59–67, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10142 [ABSTRACT FROM AUTHOR]

An orthogonal frequency division multiplexing (OFDM) transmission system is known to exhibit superior performance compared to a single carrier system in a multipath environment. However, the communication quality degrades severely because of delayed waves exceeding the guard interval and the Doppler shift. To solve this problem, various systems have been proposed that use an adaptive array to suppress undesired signals. In this paper, we propose a system that uses the same signal in the guard interval inserted at the head and the guard interval at the tail of the OFDM effective symbol in an OFDM transmission system and operates a minimum mean square error (MMSE) adaptive array. To clearly show the effectiveness of the proposed system, we analyzed the basic performance by a computer simulation. These results demonstrated excellent operation as an MMSE adaptive array and superior undesired signal suppression. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(10): 1–9, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10121 [ABSTRACT FROM AUTHOR]