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.

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.

Layout design for analog circuits has historically been a time consuming, error-prone, manual task. Its complexity results not so much from the number of devices, as from the complex interactions among devices or with the operating environment, and also from continuous-valued performance specifications. This paper addresses the problem of device-level placement for analog layout in a non-traditional way. Different from the classic approaches--exploring a huge search space with a combinatorial optimization technique, where the cells are represented by means of absolute coordinates, being allowed to illegally overlap during their moves in the chip plane--this paper advocates the use of non-slicing topological representations, like (symmetric-feasible) sequence-pairs, ordered- and binary- trees. Extensive tests, processing industrial analog designs, have shown that using skillfully the symmetry constraints (very typical to analog circuits) to remodel the solution space of the encoding systems, the topological representation techniques can achieve a better computation speed than the traditional approaches, while obtaining a similar high quality of the designs.

Topological sorting is, given with a directed acyclic graph G=(V,E), to find a total ordering of the vertices such that if (u,v)E then u is ordered before v. Instead of topological sorting, we are interested in how many total orderings exist in a given directed acyclic graph. We call such a total ordering as legal sequence and the problem of finding total number of legal sequences as legal sequence number problem. In this paper, we firstly give necessary definitions and known results obtained in our previous research. Then we give a method how to obtain legal sequence number for a class of directed acyclic graphs, extended 2-b-SPGs. Finally we discuss the complexity of legal sequence number problem for extended 2-b-SPGs.

The legal firing sequence problem of Petri nets (LFS) is one of fundamental problems in the analysis of Petri nets, because it appears as a subproblem of various basic problems. Since LFS is shown to be NP-hard, various heuristics has been proposed to solve the problem of practical size in a reasonable time. In this paper, we propose a new algorithm for this problem. It is based on the partial order verification technique, and reduces redundant branches in the search tree. Moreover, the proposed algorithm can be combined with various types of heuristics.

This paper proposes a non-linear adaptive algorithm, the amplitude banded RLS (ABRLS) algorithm, as an adaptation procedure for time variant channel equalizers. In the ABRLS algorithm, a coefficient matrix is updated based on the amplitude level of the received sequence. To enhance the capability of tracking for the ABRLS algorithm, a parallel adaptation scheme is utilized which involves the structures of decision feedback equalizer (DFE). Computer simulations demonstrate that the novel ABRLS based equalizer provides a significant improvement relative to the conventional RLS DFE on a rapidly time variant communication channel.

A new ramped-square sustain waveform is proposed to improve both the luminance and the luminous efficiency of an alternate current plasma display panel (ac PDP). The luminous characteristics such as the luminance and luminous efficiency have been measured with a square-voltage and a ramp-voltage (or voltage slope) of the proposed sustain pulse. With an increase in the square-voltage of a ramped-square sustain waveform, the luminance increases but the luminous efficiency decreases. On the other hand, with an increase in the ramp-voltage of a ramped-square sustain waveform, both the luminance and the luminous efficiency increase. When compared with the conventional square sustain waveform, an improved luminance of 22% and luminous efficiency of 36% are simultaneously obtained based on the proper adjustment of the square-voltage and ramp-voltage of the ramped-square sustain waveform in a 4-inch ac PDP test panel at a frequency of 62 kHz.

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 SNRth 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.

There exist some results showing that quantum communications are more powerful than classical communications. Moreover, although quantum entangled states do not give extra information, by using prior entanglement the quantum communication complexity of some functions is less than the classical communication complexity. The communications with prior entanglement can be regarded as a type of public coin models. In this paper, we investigate quantum communications for multi-party with prior entanglement, and show that there exists a generalized inner product function for k-party such that the quantum communication complexity is at most k bits, but the classical communication complexity needs at least 3k/2 bits. Moreover, we also provide a generalized form of prior entanglements that is effective in order to compute some type of Boolean functions.

The present paper treats the analysis and design method of the (H)NRD guide and E-plane rectangular waveguide integrated structures on the basis of the transverse resonance technique. The analysis is made by assuming a resonant cavity short-circuited at appropriate reference planes and considering the cavity as a waveguide discontinuity problem in the transverse direction. The resonant lengths are determined from the transverse equivalent circuit, and the scattering parameters are calculated from the lengths. We analyze (H)NRD discontinuities and design two types of HNRD guide to E-plane waveguide transitions and a directional coupler composed of HNRD and E-plane waveguide. The theoretical results are in good agreement with results calculated by an EM-simulator.

Power supply rejection ratio (PSRR) characteristics of a switched capacitor filter (SCF) is improved when using an equal level diagram design of a leapfrog type filter. By using this design method, it is shown that PSRR of a SCF measured is improved about 20 dB.

This paper proposes a vector quantization scheme which makes it possible to consider the dynamics of input vectors. In the proposed scheme, a linear transformation is applied to the consecutive input vectors and the resulting vector is quantized with a distortion measure defined by the statistics. At the decoder side, the output vector sequence is determined using the statistics associated with the transmitted indices in such a way that a likelihood is maximized. To solve the maximization problem, a computationally efficient algorithm is derived. The performance of the proposed method is evaluated in LSP parameter quantization. It is found that the LSP trajectories and the corresponding spectra change quite smoothly in the proposed method. It is also shown that the use of the proposed method results in a significant improvement of subjective quality.

We present a novel kind of integrate-and-fire circuit (IFC) with two periodic inputs: a pulse-train stimulation input and a base input. We clarify that the system state is quantized by the pulse-train stimulation input. Then the system dynamics is described by a return map with quantized state (Qmap). By changing the shape of the base input, various Qmaps can be obtained. The Qmap exhibits co-existence state of various super-stable periodic orbits, and the IFC outputs one of corresponding super-stable periodic pulse-trains depending on the initial state. For a typical case, we clarify the number of co-existing periodic pulse-trains theoretically for the stimulation frequencies. Constructing a simple test circuit, typical phenomena can be verified in the laboratory.

The capacity of quantum channel with product input states was formulated by the quantum coding theorem. However, whether entangled input states can enhance the quantum channel is still open. It turns out that this problem is reduced to a special case of the more general problem whether the capacity of product quantum channel exhibits additivity. In the present study, we apply one of the quantum Arimoto-Blahut type algorithms to the latter problem. The results suggest that the additivity of product quantum channel capacity always holds and that entangled input states cannot enhance the quantum channel capacity.

Decentralized XML databases are often used in Electronic Commerce (EC) business models such as e-brokers on the Web. To flexibly model such applications, we need a modeling language for EC business processes. To this end, we have adopted a query language approach and have designed a query language, called XBML, for decentralized XML databases used in EC businesses. In this paper, we explain and validate the functionality of XBML by specifying e-broker business models and describe the implementation of the XBML server, focusing on the distributed query processing.

In this paper, we propose a new type of hybrid ARQ protocol, in which a channel-adaptive variable rate channel coding scheme is combined with a multi-copy retransmission strategy so as to enhance the system performance under the delay constraint of real-time ATM services in broadband radio access networks. The main feature of a multi-copy retransmission strategy in this scheme is to improve the average throughput for a given Forward Error Correction (FEC) rate, subject to the prescribed cell loss requirement of the real-time wireless ATM services, while augmenting the reliability of channel state information required for a channel-adaptive FEC scheme. Our analysis shows that under a harsh fading channel, the proposed approach is useful for achieving the prescribed cell loss performance without significantly degrading the average throughput performance.

In this paper, two efficient codebook searching algorithms for vector quantization (VQ) are presented. The first fast search algorithm utilizes the compactness property of signal energy of orthogonal transformation. On the transformed domain, the algorithm uses geometrical relations between the input vector and codeword to discard many unlikely codewords. The second algorithm, which transforms principal components only, is proposed to alleviate some calculation overhead and the amount of storage. The relation between the principal components and the input vector is utilized in the second algorithm. Since both of the proposed algorithms reject those codewords that are impossible to be the nearest codeword, they produce the same output as conventional full search algorithm. Simulation results confirm the effectiveness of the proposed algorithms.

WFQ (Weighted Fair Queueing) is an ideal scheduling algorithm in terms of delay and fairness. However, timestamp computation complexity makes the implementation difficult. In this paper we propose an efficient and simple fair queueing algorithm, called Emulated Weighted Fair Queueing (EWFQ), which has O(1) complexity for the virtual time computation while it almost perfectly emulates the delay and fairness properties of WFQ. The key idea of EWFQ is that it calibrates the system virtual time only at the end of each packet transmission, while it calculates the system virtual time for a newly arrived packet by employing a linear approximation. By doing so, EWFQ has a rate-proportional property. EWFQ can be implemented in a router for supporting the differential and integrated services.

The low-frequency noise of InGaAs pseudomorphic HEMTs fabricated on GaAs substrate was studied. The dependence of the noise spectral density on the gate voltage indicates that the channel of the device dominates the low-frequency noise. Generation-recombination (G-R) noise was observed in the form of bulges superimposed on a background of 1/f. The activation energyof the G-R noise was 0.32-0.39 eV which is close to that of the DX center, suggesting that the origin of the G-R noise is the DX center in the AlGaAs barrier layer. Little bulge was observed in the gate current noise of the HEMTs with large InAs mole fractions of 0.4 and 0.5. Generation of the traps with different time constant can explain this behavior.

We fabricated 50-nm-gate InAlAs/InGaAs high electron mobility transistors (HEMTs) lattice-matched to InP substrates by using a conventional process under low temperatures, below 300C, to prevent fluorine contamination and suppress possible diffusion of the Si-δ-doped sheet in the electron-supply layer, and measured the DC and RF performance of the transistors. The DC measurement showed that the maximum transconductance gm of a 50-nm-gate HEMT is about 0.91 S/mm. The cutoff frequency fT of our 50-nm-gate HEMT is 362 GHz, which is much higher than the values reported for previous 50-nm-gate lattice-matched HEMTs. The excellent RF performance of our HEMTs results from a shortening of the lateral extended range of charge control by the drain field, and this may have been achieved because the low-temperature fabrication process suppressed degradation of epitaxial structure.