A high efficiency feedforward power amplifier (FFPA) with a series diode linearizer for cellular base stations is presented. In order to achieve the highest overall efficiency of an FFPA, an improved pre-distortion diode linearizer has been used and the bias condition of the main amplifier has been optimized. The optimum bias condition has been derived from the overall efficiency analysis of the FFPA with a pre-distortion linearizer. From measured overall performances of the FFPA, efficiency enhancement of the series diode linearizer has been verified. The developed FFPA achieved the efficiency of 10% and output power of 45.6 dBm at 10 MHz offset Adjacent Channel leakage Power Ratio (ACPR) -50 dBc under Wide-band Code-Division Multiple-Access (W-CDMA) modulated 2 carriers signal. This design method can be also used to optimize the source and load impedances condition of the main amplifier FET.

A novel compact T/R (Transmit/Receive) switching circuit for wideband T/R modules has been proposed. It employs quadrature couplers and gate-and-drain-driven HPAs to remove circulators or T/R switches from a conventional T/R module, and T/R switching is made with controlling biasing conditions of the FETs in HPAs. Furthermore, an optimum biasing condition and design of output matching circuit of the HPA have been studied to reduce loss in RX-mode, and the validity of the method has been confirmed by measurements.

Deep submicron technology calls for new design techniques, in which wire and gate delays are accounted to have equal or nearly equal effect on circuit behavior. Asynchronous speed-independent (SI) circuits, whose behavior is only robust to gate delay variations, may be too optimistic. On the other hand, building circuits totally delay-insensitive (DI), for both gates and wires, is impractical because of the lack of effective synthesis methods. The paper presents a new approach for synthesis of globally DI and locally SI circuits. The method, working in two possible design scenarios, either starts from a behavioral specification called Signal Transition Graph (STG) or from the SI implementation of the STG specification. The method locally modifies the initial model in such a way that the resultant behavior of the system does not depend on delays in the input wires. This guarantees delay-insensitivity of the system-environment interface. The suggested approach was successfully tested on a set of benchmarks. Experimental results show that DI interfacing is realized with a relatively moderate cost in area and speed (costs about 40% area penalty and 20% speed penalty).

In this paper, a VLSI architecture for lifting-based discrete wavelet transform (LDWT) is presented. Our architecture folds the computations of all resolution levels into the same low-pass and high-pass units to achieve higher hardware utilization. Due to the regular and flexible structure of the design, its area is independent of the length of the 1-D input sequence, and its latency is independent of the number of resolution levels. For the computations of analysis process of N-sample 1-D 3-level LDWT, our design takes about N clock cycles and requires 2 multipliers, 4 adders, and 22 registers. It is fabricated with TSMC 0.35-µm cell library and has a die size of 1.21.2 mm2. The power dissipation of the chip is about 0.4 W at the clock rate of 80 MHz.

An efficient method for calculating impedance matrix elements is proposed for analysis of microstrip structures with an arbitrary substrate thickness. Closed-form Green's functions are derived by applying the GPOF method to the remaining function after the extraction of the contributions of the surface wave pole, source dipole itself, and quasi-static (i.e.real images) from a spectral domain Green's function. When closed-form Green's functions are used in conjunction with rooftop-pulse subsectional basis functions and the razor testing function in an MoM with an MPIE formulation, the integrals appearing in the calculation procedure of the diagonal matrix elements are of two types. The first is x0n [e^(-jk0(x02 + y02 +a2)1/2)/(x02 + y02 +a2)1/2)]dx0dy0 (where n=0, 1) for the contribution of both the source dipole itself or real images where a=0 and complex images where a=complex constant, while the other is x0n H0(2)(kρp (x02 + y02)1/2)dx0dy0 for the contribution of the surface wave pole where kρp is a real pole due to the surface wave. Adopting a polar coordinate for the integral for both cases of n=0 and n=1 and performing analytical integrations for n=1 with respect to the variable x0 for both types not only removes the singularities but also drastically reduces the evaluation time for the numerical integration. In addition, the above numerical efficiency is also retained for the off-diagonal elements. To validate the proposed method, several numerical examples are presented.

In this paper, we propose a medium access control (MAC) protocol for multimedia code division multiple access (CDMA) communications. In the proposed protocol, a base station (BS) estimates the instantaneous number of simultaneously transmitted packets in the future slots with exploiting a stochastic property of traffic. In order to carry out this estimation, we employ an adaptive algorithm. We evaluate the performance of the proposed protocol by comparing that with two different cases. One is no estimation case and the other is perfect estimation case. From these results, we clarify the advantage of the proposed MAC protocol.

This paper presents circuit models for the description of the frequency-dependent behavior of coils for horizontal deflection in CRTs. This enables CRT circuit designers to use circuit simulation programs to predict the high-frequency behavior of the interaction between the deflection coils and the drive circuit. An overview is given of the major phenomena that occur in CRT deflection coils at various frequencies. Models are presented for the dissipative, the capacitive, and the resonant behavior in successive frequency intervals. With these models, phenomena such as power dissipation and ringing can not only be related to design parameters, but can also be calculated from impedance characteristics which are relatively easy to measure.

Various niching methods have been developed to maintain the population diversity. The feature of these methods is to prevent the proliferation of similar individuals in the niche (subpopulation) based on the similarity measure. This paper demonstrates that they are effective to avoid premature convergence in a case where only one global optimum in multimodal functions is searched. The performance of major niching methods in such a case is investigated and compared by experiments using seven benchmark functions. The niching methods tested in this paper are deterministic crowding, probabilistic crowding, restricted tournament selection, clearing procedure and diversity-control-oriented genetic algorithm (DCGA). According to the experiment, each method shows a fairly good global-optimum-searching capability. However, no method can completely avoid premature convergence in all functions. In addition, no method shows a better searching capability than the other methods in all functions.

The locally optimum rank detector achieves a simpler detector structure when reference observations, in addition to regular observations, are available. Without reference observations, we have to use the sign statistics of regular observations, and using the sign statistics results in a complex detector structure. Instead, more computations are necessary to deal with additional reference observations.

An efficient algorithm is proposed for finding all dc solutions of piecewise-linear (PWL) circuits. This algorithm is based on a powerful test (termed the LP test) for nonexistence of a solution to a system of PWL equations in a given region using the dual simplex method. The proposed algorithm also uses a special technique that decreases the number of regions on which the LP test is performed. By numerical examples, it is shown that the proposed algorithm could find all solutions of large scale problems, including those where the number of variables is 500 and the number of linear regions is 10500, in practical computation time.

It is very important to accurately and effectively track the movement of each mobile terminal in the personal communications networks. Accordingly, various dynamic location update schemes reflecting the mobile terminal's moving pattern are proposed in the literature. Important schemes include time-based, movement-based, distance-based, and direction-based location update schemes. In this paper, we intend to improve the performance of the movement-based location update scheme which is simple to implement and shows good performance. The proposed location update scheme reflects each mobile terminal's movement characteristics and reduces the number of unnecessary location updates. The performance of the proposed scheme is evaluated and compared with the previously proposed movement-based location update scheme through simulation. The proposed location update scheme requires three memory elements to maintain the movement history in the mobile terminal. The simulation results show that the location management cost is significantly reduced especially for the case with small call-to-mobility ratio by minimizing the unnecessary location updates intrinsic in the movement-based location update scheme.

The objective of this paper is to generate a wideband and temporal response from three-dimensional conducting structures. This is accomplished through the use of a hybrid method that involves generation of early time and low frequency information. These two are mutually complementary and contain all the necessary information for a sufficient record length. Utilizing orthogonal polynomials, time domain signal of scattering electromagnetic field could be expressed in an efficient way as well as the corresponding frequency domain responses. The available data is simultaneously extrapolated in both domains. Computational load for electromagnetic analysis, the Method of Moment (MOM), can be significantly reduced.

A performance comparison is developed between a chaotic communication system and a spread spectrum system with similar features in terms of bandwidth and transceiver structure but based on more conventional Gold sequences. Comparison is made in the presence of noise and multipath contributions which degrade the channel quality. It is shown that, because of its more favourable correlation properties, the chaotic scheme exhibits lower error rates, at a parity of the bandwidth expansion factor. The same favourable correlation properties are also used to explain and show, through a numerical example, the benefits of chaotic segments in a multi-user environment.

To obtain a high throughput for transmission control protocol (TCP) connections over the wireless links, we previously proposed a novel transmission power control method for code division multiple access (CDMA) packet communication systems. By using this transmission power control method, we developed a transmission power control method and a packet multiplexing method to transmit constant bit rate (CBR) and TCP packets over CDMA wireless systems. Our methods can guarantee the quality of service (QoS) for CBR connections and utilize bandwidth effectively without modifying the TCP protocol or using slot assignments. Evaluation of our methods by computer simulation showed that the proposed methods provide a near-maximum throughput and guarantee the packet loss ratio of CBR connections regardless of the number of connections.

A number of schemes have been proposed for communication using chaos over the past years. Regardless of the exact modulation method used, the transmitted signal must go through a physical channel which undesirably introduces distortion to the signal and adds noise to it. The problem is particularly serious when coherent-based demodulation is used because the necessary process of chaos synchronization is difficult to implement in practice. This paper addresses the channel distortion problem and proposes a technique for channel equalization in chaos-based communication systems. The proposed equalization is realized by a modified recurrent neural network (RNN) incorporating a specific training (equalizing) algorithm. Computer simulations are used to demonstrate the performance of the proposed equalizer in chaos-based communication systems. The Henon map and Chua's circuit are used to generate chaotic signals. It is shown that the proposed RNN-based equalizer outperforms conventional equalizers.

Let us introduce n ( 2) mappings fi (i=1,2,,n) defined on complete linear metric spaces (Xi-1, ρ) (i=1,2,,n), respectively, and let fi:Xi-1 Xi be completely continuous on bounded convex closed subsets Xi-1(0) Xi-1, (i=1,2,,n 0), such that fi(Xi-1(0)) Xi(0). Moreover, let us introduce n set-valued mappings Fi : Xi-1 Xi (Xi)(the family of all non-empty closed compact subsets of Xi), (i=1,2,,n 0). Here, we have a fixed point theorem on the successively recurrent system of set-valued mapping equations: xi Fi(xi-1, fi(xi-1)), (i=1,2,,n 0). This theorem can be applied immediately to analysis of the availability of system of circular networks of channels undergone by uncertain fluctuations and to evaluation of the tolerability of behaviors of those systems. In this paper, mathematical situation and detailed proof are discussed, about this theorem.

This letter presents a new approach for obtaining the expected waiting time for packets under the drop-head (also called a drop-from-front) scheme for buffer management. The results show that the drop-head scheme is more effective in reducing queueing delays than the drop-tail scheme.

The radar cross section (RCS) of a dielectric-coated cylindrical cavity was measured and the measurements were compared with those calculated according to the iterative physical optics (IPO). The IPO analysis used the equivalent-impedance boundary condition (EIBC) based on transmission-line theory which takes into account the thickness of the coating. It was consequently found that this condition is much more effective than the ordinary-impedance boundary condition based on the intrinsic impedance of the material.

As we move toward the transition to the IPv6 next generation network environment, it is necessary to realize heterogeneous communications between IPv6 and IPv4 terminals without sacrificing any convenience or frameworks of current communication methods. Mechanisms that satisfy such requirements are called translators. This paper categorizes various translator mechanisms and clarifies their characteristics. As a result of analyses, this paper proposes a SOCKS-based IPv6/IPv4 Translator, and describes its design and implementation. Compared with other translator mechanisms, the SOCKS-based translator have small constraints and good characteristics. For example, it can integrate DNS name resolving procedures, which is an important mechanism for the transition. The translator has already been implemented and it has been proved that it can support typical communication services such as telnet, ftp, http, mail without any problems.

The paper deals with the estimation method of system equations of dynamic behavior of an input-pricing mechanism by using the Genetic Programming (GP) and its applications. The scheme is similar to recent noise reduction method in noisy speech which is based on the adaptive digital signal processing for system identification and subtraction estimated noise. We consider the dynamic behavior of an input-pricing mechanism for a service facility in which heterogeneous self-optimizing customers base their future join/balk decisions on their previous experiences of congestion. In the GP, the system equations are represented by parse trees and the performance (fitness) of each individual is defined as the inversion of the root mean square error between the observed data and the output of the system equation. By selecting a pair of individuals having higher fitness, the crossover operation is applied to generate new individuals. The string used for the GP is extended to treat the rational form of system functions. The condition for the Li-Yorke chaos is exploited to ensure the chaoticity of the approximated functions. In our control, since the system equations are estimated, we only need to change the input incrementally so that the system moves to the stable region. By assuming the targeted dynamic system f(x(t)) with input u(t)=0 is estimated by using the GP (denoted (x(t))), then we impose the input u(t) so that xf= (t+1)=(x(t))+u(t) where xf is the fixed point. Then, the next state x(t+1) of targeted dynamic system f(x(t)) is replaced by x(t+1)+u(t). We extend ordinary control method based on the GP by imposing the input u(t) so that the deviation from the targeted level xL becomes small enough after the control. The approximation and control method are applied to the chaotic dynamics generating various time series based on several queuing models and real world data. Using the GP, the control of chaos is straightforward, and we show some example of stabilizing the price expectation in the service queue.