This paper proposes an automatic dispersion equalization system using extracted clock power monitoring in order to facilitate the field installation of high-speed time-division multiplexed (TDM) systems over existing fiber cables. The proposed scheme adjusts the dispersion of a variable-dispersion equalizer so as to maximize the extracted clock power level. This scheme has a simple configuration, needs no communication channel between the transmitter and the receiver, and is sensitive to parameters such as initial chirping and fiber input power. The clock power dependence on the fiber dispersion is theoretically analyzed assuming that the return-to-zero (RZ) format is used and that pulse broadening is small compared to the bit duration. We show that the clock power is maximized when the dispersion-induced waveform distortion is minimized. Numerical simulations show that the proposed scheme is effective with the non-return-to-zero (NRZ) format and for the case that the optimum total dispersion deviates from zero due to initial and/or self-phase modulation (SPM)-induced chirping. The operation of the proposed automatic equalization system is experimentally confirmed in 20-Gbit/s transmission using both RZ and NRZ formats. Moreover, a 40-Gbit/s transmission experiment over 200 km of dispersion-shifted fiber (DSF) is successfully demonstrated using the proposed equalization scheme.

In this paper, we present a design for an optical video transmission system employing a super wide-band FM modulation scheme. We focus on the design of optical transmitters and receivers, especially a wide-band electrical-to-optical converter and optical-to-electrical converter. With this system, it is important to develop optical and microwave devices which have a wide frequency response combined with flat group delay characteristics in order to improve the quality of the video signals after transmission. We also analyze theoretically the hybrid transmission capacity of AM analog video signals and 64QAM signals for digital video and data, and show the FM modulation parameters needed to realize high quality transmission. An experimental evaluation shows that our designed optical transmitter and receiver achieve high quality for the various channel plans for AM/64QAM hybrid transmission. The system has high received optical sensitivity and a wide optical dynamic range, allowing it to distribute analog video, digital video, and Internet data to many users over a wide area.

In this paper, we consider the subchannel detection problem in forward links for the multicarrier DS-CDMA system when some different subchannel allocation policies are used. An optimal subchannel decision algorithm is proposed based on the maximum-likelihood (ML) criterion. Theoretical analysis and simulation results are presented. Furthermore, we discuss the parameter selection problem on the length of the training sequences in the subchannel allocation scheme in [8],[12] by using the proposed ML detection algorithm. The results show that the subchannel allocation scheme in [8],[12] is feasible since only a few symbols overhead is required.

The next generation of wireless networks must provide sufficient resources to support a broader range of services beyond the traditional voice-only services provided in current wireless systems. For this, packet scheduling is the most critical function involved in the provision of individual bandwidth, and delay guarantee to meet the required qualities of service (QoS) for the switched sessions. In this paper we introduce the concept of system capacity in the multi-code CDMA system and evaluate the system performance constrained by the required SNR_th and other QoS factors. The CAC algorithm is proposed to administer the requests. Moreover, the enforcer, scheduler and shaper are proposed to maintain the required QoS. The system performance including blocking probability, mean delay and bandwidth utilization in the BS egress are evaluated and compared under different traffic loadings.

An adaptive rate communication system based on the N-MSK modulation technique is described. Two examples of the system using a 2-MSK adaptive modulation scheme and a 4-MSK adaptive modulation scheme are presented and analysed in slow fading channel. The channel attenuation obeys either Rayleigh or lognormal distribution. The proposed adaptive rate communication system is able to track slow variations of channel attenuation and the average system throughput is therefore increased at a given BER.

This paper presents a variable rate transmission scheme suitable for bandlimited meteor burst channel. Meteor Burst Communication (MBC) is a unique type of radio communication, which is primarily used for non-realtime remote data collection. In the paper, along with conventional BPSK and QPSK modulations, QAM and M-ary Bi-orthogonal modulations are analyzed for software modem implementation in an MBC system. Performance of the modulation methods is presented for both static AWGN channel and meteor burst channel. The proposed scheme for variable rate transmission dynamically estimates the MBC channel and varies the modulation type of a software modem, to control the transmission rate between bursts. The scheme dynamically selects a modulation type and packet length that will maximize the average throughput of the system. Performance of the scheme is analyzed and compared with conventional fixed rate modems. A practical implementation for software modem is suggested that uses a common core modulator/demodulator structure.

A quality-of-service based link control scheme to counteract correlated channel errors for wireless multimedia communications is proposed in this paper. Both the medium access (MAC) and data link control (DLC) layers are treated. The performance of the proposed scheme is evaluated using both analysis and simulation. The delay and jitter behaviors are examined for both the constant bit rate (CBR) traffic and variable bit rate (VBR) traffic. The throughput performance is also obtained for the available bit rate (ABR) traffic. Through numerical experiments, the proposed scheme is demonstrated to be not only robust against channel impairments but also capable of providing the desired QoS for wireless multimedia communications.

The IEEE 1394 is a standard for the high performance serial bus interface. This standard has the isochronous transfer mode that is suitable for real-time applications and the asynchronous transfer mode for delay-insensitive applications. It can be used to construct a small-size local area network. We propose a queueing model for a network with this standard under some assumptions, and calculate the average waiting time of an asynchronous packet in the buffer in the steady state. We give some numerical results, along with validation by simulation, in order to evaluate its performance.

A distributed network management system (NMS) is urgently needed to manage large number of network managed objects (MOs) such as public network MOs. The ATM Forum has proposed the M4-interface to achieve just such a distributed NMS. However, the basis of the M4-interface is not adequate in terms of flexible distribution, because its main unit of distribution is location. To improve the granularity of the distribution, we have defined the route as a further unit of distribution. We also describe new MOs that provide for a distribution based on routes. A more detailed distribution is then possible than with a distribution purely based on location. In addition, we propose a new CMIP Action to move MOs from one sub-NMS (SubNMS) to another while the system is running. Using this Action, we can achieve a more flexible distribution in terms of network problems and load.

Today software piracy is a major concern to electronic commerce since a digitized product such as software is vulnerable to redistribution and unauthorized use. This paper presents an enhanced electronic software distribution and software protection model. Authentication scheme of the proposed model is based on zero-knowledge (ZK) proof which requires limited computation. The proposed model considers post installation security using authentication agent. It prevents software piracy and illegal copy. It also provides secure and efficient software live-update mechanism based on traitor tracing scheme. Even if software or personal key is copied illegally, a merchant can trace back to its original owner from the electronic license and personal key. The proposed model provides security and reasonable performance and safety.

This paper presents an intelligent routing algorithm, called Q-Agents, which bases its actions only on the agent-environment interaction. This algorithm combines properties of three learning strategies (Q-learning, dual reinforcement learning and learning based on ant colony behavior), adding to them two further mechanisms to improve its adaptability. Hence, the proposed algorithm is composed of a set of agents, moving through the network independently and concurrently, searching for the best routes. The agents share knowledge about the quality of the paths traversed through indirect communication. Information about the network and traffic status is updated by using Q-learning and dual reinforcement updating rules. Q-Agents were applied to a model of an AT&T circuit-switched network. Experiments were carried out on the performance of the algorithm under variations of traffic patterns, load level and topology, and with addition of noise in the information used to route calls. Q-Agents suffered a lower number of lost calls than two algorithms based entirely on ant colony behavior.

This paper proposes the Vector Evaluated GA-ICT (VEGA-ICT), a novel design method that employs the Genetic Algorithm (GA) to obtain the optimum antenna design. GA-ICT incorporates an arbitrary wire-grid model antenna to derive the optimum solution without any basic structure or limitation on the number of elements by merely optimizing an objective function. GA-ICT comprises the GA and an analysis method, the Improved Circuit Theory (ICT), with the following characteristics. (1) To achieve optimization of an arbitrary wire-grid model antenna without a basic antenna structure, the unknowns of the ICT are directly assigned to variables of the GA in the GA-ICT. (2) To achieve a variable number of elements, duplicate elements generated by using the same feasible region are deleted in the ICT. (3) To satisfy all complex design conditions, the GA-ICT generates an objective function using a weighting function generated based on electrical characteristics, antenna configuration, and size. (4) To overcome the difficulty of convergence caused by the nonlinearity of each term in the objective function, GA-ICT adopts a vector evaluation method. In this paper, the novel GA-ICT method is applied to downsize sector antennas. The calculation region in GA-ICT is reduced by adopting cylindrical coordinates and a periodic imaging structure. The GA-ICT achieves a 30% reduction in size compared to the previously reported small sector antenna, MS-MPYA, while retaining almost the same characteristics.

This paper presents the performance of the Directionally Constrained Minimization of Power (DCMP) and the Zero-Forcing (ZF) in the Angular Spread (AS) environment. To obtain the optimal weights for both methods, the Extended Array Mode Vector (EAMV) is employed. It is known that the EAMV represents the instantaneous AS as well as the instantaneous DOA in the slow fading channel. As a result, it is shown that the DCMP and the ZF using the EAMV estimates can improve the Signal-to-Interference-plus-Noise Ratio (SINR) considerably, as compared with those using the Direction of Arrival (DOA) information only. At the same time, the intrinsic problems causing the performance loss in the DCMP and the ZF are revisited. From this, the reasons for the performance deterioration are analyzed, in relation with the AS, the number of samples, the number of antenna elements, and the spatial correlation coefficient of the signals. It follows that the optimal signal combining techniques using the EAMV estimates can diminish such effects.

A multi-grid finite-difference time-domain (FDTD) method was applied for numerical dosimetry analysis in the human head for 5 GHz band portable terminals. By applying fine FDTD grids to the volumes in the human head where the highest electromagnetic (EM) absorption occurs and coarse grids to the remaining volumes of the head, the spatial peak specific absorption rate (SAR) assessment was achieved with a less computation memory and time. The accuracy of applying the multi-grid FDTD method to the spatial peak SAR assessment was checked in comparison with the results obtained from the usual uniform-grid method, and then the spatial peak SARs for three typical situations of a person using a 5.2 GHz band portable terminal were calculated in conjunction with an anatomically based human head model.

This paper investigates a device model of the power current used for an LSI/IC. The model is proposed to analyze the power bus noise in digital circuit boards. This model is defined in the frequency domain and constructed with an equivalent internal impedance and an equivalent internal current source. Accordingly, the output current of the model is affected by power bus impedance, such as the capacitance of bypass capacitors and the parasitic inductance of power bus wiring. Therefore, the model is useful for analyzing the effectiveness of bypass capacitors and power bus wiring. The structure of equivalent internal impedance for a simple logic IC, such as 74HCXX, can be represented as an RLC series circuit. These parameters are identified by applying the least square method. To demonstrate the validity of the model, an experimental study was conducted. As a result, it was shown that the output current of the model corresponds to the measured current under a variety of power bus impedance levels within 6 dB.

A novel in vivo exposure setup has been developed for testing the possible promoting effects of 1.5 GHz digital cellular phones on mouse skin carcinogenesis. The exposure setup has two main features: one is the employment of an electrically short monopole antenna with capacitive-loading, which supplies the ability to realize a highly localized peak SAR above 2 W/kg without any thermal stress for a mouse; the other is the use of a transparent absorber to allow real-time observation of both the exposure process as well as mouse activities during the exposure. Dosimetric analyses for the exposure setup have been carried out both numerically and experimentally. Good agreement was confirmed between the numerical and experimental results, thereby demonstrating the validity of the novel exposure setup.

In this letter, blind adaptive H multiuser detection is developed by employing a generalized sidelobe canceler (GSC) with and without subweight partition scheme. It is shown that the adaptive H algorithm with subweight approach has the advantages of fast convergence speed, insensitivity of dynamic estimate error, and suitability for arbitrary ambient noise over the conventional H and the RLS-based adaptive algorithms.

Signal fading due to multipath propagation severely impairs the performance of high speed mobile communication systems. The probability density function (PDF) for the envelope of the received signal using STTD (Space Time Transmitter Diversity) over correlated Nakagami fading channels with additive white Gaussian noise (AWGN) is derived in this paper. System performances of noncoherent signals over slow and flat fading channels in the presence of AWGN can be evaluated from this new PDF.

We present a simple cell scheduling algorithm for an input buffered switch. The suggested algorithm is based on iSLIP and consists of request, grant and accept steps. The pointer update scheme of iSLIP is simplified in the suggested algorithm. By virtue of the new update scheme, the performance of the suggested algorithm is better than that of iSLIP with one iteration. Using computer simulations under a uniform traffic, we show the suggested algorithm is more appropriate than iSLIP for scheduling of an input buffered switch with multiple service classes.

A dual-offset microstrip-fed slot antenna having large bandwidth studied in this paper. The proposed antenna is analyzed by the Finite Difference Time Domain (FDTD) method. In this case, two offsets and other design parameters of the antenna lead to the good impedance matching over a wide frequency band. The experimental bandwidth is approximately 1.587 octave (-10 dB S₁₁). And the experimented data for the impedance loci, the radiation patterns, and gain of the antenna are also described. The measured results are relatively in good agreement with the FDTD results.