This paper provides a new robust guaranteed cost controller design method for discrete parameter uncertain time delay systems. The result shows much tighter bound of guaranteed cost than that of existing paper. In order to get the optimal (minimum) value of guaranteed cost, an optimization problem is given by linear matrix inequality (LMI) technique. Also, the parameter uncertain systems with time delays in both state and control input are considered.

An uplink synchronised CDMA system through transmission timing control at mobile users has been proposed to improve the uplink capacity. This Letter mathematically investigates its capacity, considering perfect fast TPC and two antenna diversity reception in a single cell environment and compares it with that of a conventional CDMA system.

In two- or more-dimensional systems where the components of the sample data are strongly correlated, it is not proper to divide the input space into several subspaces without considering the correlation. In this paper, we propose the usage of the method of principal component in order to uncorrelate and remove any redundancy from the input space of the adaptive neuro-fuzzy inference system (ANFIS). This leads to an effective partition of the input space to the fuzzy model and significantly reduces the modeling error. A computer simulation for two frequently used benchmark problems shows that ANFIS with the uncorrelation process performs better than the original ANFIS under the same conditions.

The diffraction of a plane electromagnetic wave by an impedance wedge whose boundary is described in terms of the skew coordinate systems is treated by using the Wiener-Hopf technique. The problem is formulated in terms of the simultaneous Wiener-Hopf equations, which are then solved by using a factorization and decomposition procedure and introducing appropriate functions to satisfy the edge condition. The exact solution is expressed through the Maliuzhinets functions. By deforming the integration path of the Fourier inverse transform, which expresses the scattered field, the expressions of the reflected field, diffracted field and the surface wave are obtained. The numerical examples for these fields are given and the characteristics of the surface wave are discussed.

As the capacity of a personal computer and workstation increases rapidly, many electromagnetic simulators solving antenna problems are widely used. In this paper, the IE3D electromagnetic simulator, which is a commercial software product, is applied to the analysis of handset antennas in the vicinity of the human body. Firstly, basic characteristics of popular handset antennas such as whip and planar inverted-F antennas are obtained by the IE3D electromagnetic simulator and calculated results are compared with measured results quoted from the referenced paper. Secondly, on the basis of newly considered design concept for a handset antenna, a loop antenna system for the handset, which we have proposed in order to reduce the influence of human body, is taken as an example of a balance-fed antenna and is analyzed theoretically and experimentally including the influence of the human body. In a result, calculated results by the IE3D electromagnetic simulator are in good agreement with measured results and it is confirmed that the simulator is very effective in analyzing the handset antenna in the vicinity of the human body.

In this paper, we present a dynamic output feedback controller design technique for robust decentralized stabilization of uncertain large-scale systems with time-delay in the subsystem interconnections. Based on Lyapunov second method, a sufficient condition for the stability, is derived in terms of three linear matrix inequalities (LMI). The solutions of the LMIs can be easily obtained using efficient convex optimization techniques. A numerical example is given to illustrate the proposed method.

In this paper, we report on our recent work in designing and developing an optical waveguide and optical integrated circuit for optical BFN in adaptive multibeam array antenna. We introduce a new integrated Ti:LiNbO3 waveguide and prove that it is able to yield large birefringence and birefringence dispersion. We present a new technique using a microwave-modulated optical wave to measure the birefringence in integrated Ti:LiNbO3 optical waveguides. The measuring results show that the new waveguide has a birefringence of 0.08 and birefringence dispersion of 0.05 µm-1 at optical wavelength of 1.55 µm. When the new Ti:LiNbO3 is applied to form a integrated optical waveguide array in optical beamforming network, it is shown that microwave phase shifts within the range of [-180, +180] is achieved by tuning the optical wavelength 10 nm around 1.55 µm.

Precise and quick multi-beam forming including null control will be one of the key technologies for the future satellite communication systems utilizing SDMA (Space Division Multiple Access) and DOA (Direction of Arrival) estimation. In order to realize the precise multi-beam forming, calibration procedure is indispensable since there are several unavoidable factors that degrade the multi-beam patterns of the array. Particularly amplitude and phase imbalance between RF circuits needs to be calibrated frequently and quickly when the array system exists in changeable environment since the imbalance easily occurs due to thermal characteristics of each RF circuit. This paper proposes a simple and high-speed remote calibration scheme compensating for amplitude and phase imbalance among RF circuits of a transmitting adaptive array antenna onboard satellite. This calibration is conducted at a remote station such as a gateway station on the ground in the satellite communication system, by utilizing the received signal including the temporally multiplexed orthogonal codes transmitted from the array antenna onboard satellite. Since the calibration factors for all the antenna elements can be simultaneously obtained by the parallel digital signal processing, calibration time can be drastically reduced. The accuracy of this calibration is estimated by simulation. Simulation results show that the amplitude imbalance among RF circuits can be suppressed within the range from -0.5 dB to +0.25 dB for the initial imbalance ranging from -2 dB to +3.5 dB, phase imbalance can be suppressed within the range of -3 deg. to +3 deg. for the initial imbalance ranging from -120 or +180 deg. by this method. The amplitude and phase deviations among the elements can be suppressed within 0.36 dB and 2.5 degrees, respectively, in 80% of probability. Simulation results also show that this calibration method is valid under the relatively bad carrier-to-noise conditions such as -10 dB at the receiver. Good improvement of the multi-beam patterns by this calibration is shown under the low carrier-to-noise ratio condition.

In code division multiple access (CDMA) systems with adaptive antennas, the direction of terminals must be considered when controlling new call admission. This paper proposes a data access control algorithm based on estimated signal-to-interference-plus-noise ratio (SINR) at the output of adaptive antennas. The algorithm estimates SINR for new data call using a response vector of the request packet to determine acceptance or blocking of the new data call. Numerical results show that the combination of transmission technology of adaptive antennas and proposed data access control can effectively increase the capacity of CDMA systems.

This paper compares the path detection probability for Rake combining and the BER performance of packet transmission with the length of TPKT = 10 (20) msec using the coherent adaptive antenna array diversity (CAAAD) receiver with those using a multi-beam receiver employing fixed antenna weights both with four antennas in a multipath fading channel in the W-CDMA reverse link. Laboratory experimental results elucidate that the required average received signal energy per bit-to-background noise spectrum density (Eb/N0) at the detection probability of 90% of at least one path and of two paths for the fading maximum Doppler frequency of fD = 5 (80) Hz using a multi-beam receiver with the number of beams equal to NBeam = 12 was decreased by approximately 1.0 (1.0) dB and 2.0 (2.0) dB, respectively, compared to that using the CAAAD receiver with the step size of µ= 10-2 for the average received SIR of the desired user of -12 dB in a 2-path Rayleigh fading channel with average equal power in a 5-user environment. We also found that the required average received Eb/N0 at the average BER of 10-3 using the multi-beam receiver was decreased by approximately 5.0 (2.5) dB compared to that of the CAAAD receiver with µ= 10-2, and the loss of the required average received Eb/N0 compared to that of CAAAD with sufficiently converged receiver antenna weights was approximately 2.0 (1.0) dB for TPKT = 10 (20) msec when the average received SIR = -12 dB in a 5-user environment.

Conventional adaptive array antenna processing must access signals on all of the array antenna elements. However, because the low-cost electronically steerable passive array radiator (ESPAR) antenna only has a single-port output, all of the signals on the antenna elements cannot be observed. In this paper, a technique for adaptively controlling the loaded reactances on the passive radiators, thus forming both beam and nulls, is presented for the ESPAR antenna. The adaptive algorithm is based on the steepest gradient theory, where the reactances are sequentially perturbed to determine the gradient vector. Simulations show that the ESPAR antenna can be adaptive. The statistical performance of the output SIR of the ESPAR antenna is also given.

The worldwide availability of the Industrial Scientific and Medical (ISM) bands has prompted the proposal of several communication systems for indoor application at the 2.4 and 5 GHz bands. Although adaptive array antennas have been thoroughly investigated for various outdoor scenarios, their application to indoor communications has been overlooked. Experimental results indicating that conventional array antenna techniques exhibit poor performance when implemented indoors have recently been published. An important peculiarity of the indoor channel is the coexistence of both near-field and far-field propagating waves. Therefore, algorithms that can indifferently cope with both near-field and far-field wavefronts for source location and beamforming are desirable. In this paper, the following are presented. First, a mathematical analysis of the performance of array antennas in the indoor environment is taken up. Second, a new, simple, cost-effective and statistically coherent scheme, the Adaptive Sampling algorithm, is proposed for location estimation of sources anywhere from near field to far field. It is shown that the proposed algorithm achieves ubiquitous source location, allowing for symmetric uplink/downlink beamforming with seamless performance. Finally, the performance of the proposed Adaptively Sampled Array Antenna is performance analyzed via computer simulations under the specifications of the IEEE802.11b DS Wireless Local Area Network (W-LAN).

This paper proposes a beam and null simultaneous steering Space-Time Equalizer (S/T-Equalizer). The proposed S/T-Equalizer performs separated S/T-signal processing in order to reduce computational complexity to a practical level. For spatial signal processing, a new Adaptive Array Antenna algorithm is used that combines the beam and null steering concepts. For temporal signal processing, a conventional delayed decision feedback sequence estimation equalizer may be used. The proposed S/T-Equalizer was prototyped, and a series of field tests was conducted using a 5 GHz frequency band to evaluate transmission performances of the proposed system. Results show that the proposed S/T-Equalizer can reduce inter-symbol interference effects while maintaining reasonable signal strength, thereby improving BER performance.

This paper proposes a novel adaptive array configuration that reduces high-power co-channel interference (CCI) by utilizing the difference in arrival times between CCI and the desired signal in asynchronous TDD systems. The proposed adaptive array extracts only the CCI and employs pre-null steering for only the CCI by utilizing the fact that only the CCI arrives during the guard time in asynchronous TDD systems. Since the proposed adaptive array enables us to apply the Minimum Mean Square Error (MMSE) algorithm through synchronization with the desired signal using the output signal obtained by pre-null steering, high quality transmission can be achieved even in the presence of high-power CCI. Moreover, based on measurements using a fading simulator and field data, an adaptive array testbed exemplifying the proposed configuration is presented to show the reduction in the high-power CCI.

In this paper, we present a new transmit diversity scheme with power control by using two transmit antennas in which the power control unit is added to adaptively suit the channel fading variation. Compared to the transmit diversity scheme (STD, one space time coding scheme) proposed by Alamouti and the traditional maximal ratio combining (MRC) diversity scheme employed at the receiver, simulation results indicate that the new scheme has considerable performance gain. We also discuss the effects of the imperfect channel parameter estimation on the performance of the system. Simulation results show that the new system is more robust to the estimation error of channel fading parameters than the STD. As the signal to noise ratio is relatively high, the diversity scheme with power control is more sensitive to the channel estimation error compared to the MRC. But when the channel estimation accuracy is relatively high, the diversity scheme with power control still has better performance than the ideal MRC as the BER is about 1 10-3.

Optimum antenna sub-set selection in MIMO systems is an attractive cost reducing technique. In this paper we develop an optimal antenna sub-set selection technique to be used in conjunction with space-time block codes over a MIMO link to optimize link error performance over a fading channel. We study the case when antenna sub-set selection is applied either at the transmitter or the receiver. We provide analytical results for substantial improvement in average SNR and outage capacity when antenna sub-set selection is used. Simulation results that verify our analytical prediction are also presented.

The number of studies on adaptive antennas has greately increased in resent years in Japan. Most of these studies have sought to enhance the capacity and suppress multipath signals in wireless mobile communications. Adaptive antennas are expected to play an important role in future mobile radio systems. In this paper, we review the history and trends of adaptive antenna studies in Japan. We describe typical adaptive processing algorithms and contributions by Japanese researchers. We then introduce some applications of adaptive antennas for mobile communications. Furthermore, we discuss multi-dimensional signal processing, which is an extended version of the adaptive antenna.

In wideband direct sequence code division multiple access (W-CDMA), employing an adaptive antenna array is a very promising technique to reduce severe multiple access interference (MAI) especially from high rate users. This paper proposes a fast and accurate two-step beam tracking algorithm implemented in a pilot symbol-assisted coherent adaptive antenna array diversity (CAAAD) receiver and evaluates its performance both by computer simulation and laboratory experiments. In the proposed scheme, the receiver antenna weights are updated by using both the signal-to-interference power ratio (SIR) measurements employing multiple sets of antenna weights (MSAW) and an adaptive algorithm based on the minimum mean square error (MMSE) criterion, in which other sets except for a original set of antenna weights are simply generated by a original set. Computer simulation results show that antenna weights of a four-antenna CAAAD receiver using the proposed beam tracking algorithm tracks changes in the direction of arrival (DOA) of the desired user at up to 34.3 degrees/sec, which corresponds to 215 km/h at 100 m from a base station. We also confirm based on the experiments in a radio anechoic room that the generated antenna weights track the DOA changes up to 12.3 degrees/sec.

This paper proposes a receiver antenna weight-updating algorithm using I/Q-code multiplexed pilot and decision feedback data symbols after channel decoding for both reference signal generation of the mean squared error (MSE) calculation and channel estimation (also for Rake combining) in the coherent adaptive antenna array diversity (CAAAD) receiver and investigates its performance, in order to decrease further the transmit power of a mobie station, thereby increasing system capacity in the wideband direct sequence code division multiple access (W-CDMA) reverse link. Experimental results show that the required transmit Eb/N0 for the average BER of 10-3 with the CAAAD receiver using pilot and decision feedback data symbols after channel decoding both for reference signal generation and for channel estimation can be decreased by approximately 0.8 dB compared to when using only pilot symbols with convolutional coding or turbo coding, when the ratio of the target Eb/I0 for fast transmit power control of the desired to interfering users is Δ Eb/I0 = -12 dB. The results also elucidate that the required transmit Eb/N0 at the average BER of 10-6 with turbo coding using the proposed decision feedback antenna weight-updating and channel estimation is smaller by approximately 0.5 dB than that using convolutional coding when the channel interleaving length is 20 msec for Δ Eb/I0 = -12 dB.

A knowledge gap between network operators and system developers in Network Management System (NMS) construction has widened. This has been caused by an expansion of supported business processes and increasingly sophisticated network management functions. This gap makes system development costly and time consuming. Function development, led by operators, is a promising solution to the problems caused by the gap. This type of development should not require an operator to know how to develop NMS. Standard objects may be used to meet this requirement and save time and the cost of NMS construction. However, they are not sufficient to design functions supporting some tasks that are for providing custom services. In this paper, we propose a partial extension package, composed of several object classes. This package is attached to the standard objects to design a custom function. Information processing in a new function can be added, and easily modified, using this package. This package specifies states that invoke the information processing. It also includes objects that add new data without changing standard objects. It makes use of several design patterns in order to weaken coupling to the standard objects. We have applied this package to two programs. One plans maintenance tasks schedules, the other sets threshold values for quality of service. We made use of software metrics to measure their performance in terms of flexibility. The results show that the proposed package continues to make it possible to reuse the standard objects, and makes it easy to modify the behavior of a new function.