This paper presents a newly developed noise post-processing (NPP) algorithm and the results of several tests demonstrating its subjective performance. This NPP algorithm is designed to improve the subjective performance of low bit-rate code excited linear prediction (CELP) decoding under background noise conditions. The NPP algorithm is based on a stationary noise generator and improves the subjective quality of noisy signal input. A backward adaptive detector defines noisy input signal frames from decoded LSF, energy, and pitch parameters. The noise generator estimates and produces stationary noise signals using past line spectral frequency (LSF) and energy parameters. The stationary noise generator has a frame erasure concealment (FEC) scheme designed for stationary noise signals and therefore improves the speech decoder's robustness for frame erasure under background noise conditions. The algorithm has been applied to the following CELP decoders: 1) a candidate algorithm of the ITU-T 4-kbit/s speech coding standard and 2) existing ITU-T standards, the G.729 and G.723.1 series. In both cases, NPP improved the subjective performance of the baseline decoders. Improvements of approximately 0.25 CMOS (CCR MOS: comparison category rating mean opinion score) and around 0.2-0.8 DMOS (DCR MOS: degradation category rating mean opinion score) were demonstrated in the results of our subjective tests when applied to the 4-kbit/s decoder and G.729/G.723.1 decoders respectively. Other test results show that NPP improves the subjective performance of a G.729 decoder by around 0.45 in DMOS under both error-free and frame-erasure conditions, and a further improvement of around 0.2 DMOS is achieved by the FEC scheme in the noise generator.

This paper describes an analysis of IP-network traffic in terms of the time variation of self-similarity. To get a comprehensive view in analyzing the degree of long-range dependence (LRD) of IP-network traffic, this paper used a self-organizing map, which provides a way to map high-dimensional data onto a low-dimensional domain. Also, in the LRD-based analysis, this paper employed detrended fluctuation analysis (DFA), which is applicable to the analysis of long-range power-law correlations or LRD in non-stationary time-series signals. In applying this method to traffic analysis, this paper performed two kinds of traffic measurement: one based on IP-network traffic flowing into NTT Musashino R&D center (Tokyo, Japan) from the Internet and the other based on IP-network traffic flowing through at an interface point between an access provider (Tokyo, Japan) and the Internet. Based on sequential measurements of IP-network traffic, this paper derived corresponding values for the LRD-related parameter α of measured traffic. As a result, we found that the characteristic of self-similarity seen in the measured traffic fluctuated over time, with different time variation patterns for two measurement locations. In training the self-organizing map, this paper used three parameters: two α values for different plot ranges, and Shannon-based entropy, which reflects the degree of concentration of measured time-series data. We visually confirmed that the traffic data could be projected onto the map in accordance with the traffic properties, resulting in a combined depiction of the effects of the degree of LRD and network utilization rates. The proposed method can deal with multi-dimensional parameters, projecting its results onto a two-dimensional space in which the projected data positions give us an effective depiction of network conditions at different times.

As the Internet proliferates, there has been a growing interest in supporting multiparty collaborative applications. It has led to the emergence of many-to-ma ny reliable multicast. Congestion control is a key task in reliable multicast along with error control. However, existing tree-based congestion control schemes such as TRAMCC and MTCP are designed for one-to-many reliable multicast and have some drawbacks when they are used for many-to-many reliable multicast. We propose an efficient congestion control mechanism, MTRMCC, for tree-based many-to-many reliable multicast protocols. The proposed scheme is based on the congestion windowing mechanism and a rate controller is used in addition. The feedback for error recovery is exploited for congestion control as well to minimize the overhead at the receivers. The ACK timer and the NACK timers are set dynamically reflecting the network traffic changes. The rate regulation algorithm in the proposed scheme is designed to help the flows sharing the same link to achieve the fair share quickly. The performance of the proposed scheme is evaluated using network simulator ns-2. The simulation results show that the proposed scheme outperforms TRAMCC in terms of intra-session fairness and supports responsiveness, TCP-friendliness, and scalability.

We propose a neural-sensing LSI with a bi-directional wireless interface, which is capable of detecting 5-channel neural signals in a living animal. The proposed sensing LSI consists of a multiplexer with 5-channels selectable from 10 channels, a chopper amplifier using a new direct-chopper-input scheme, a programmable multi-mode analog-to-digital converter (ADC), and a wireless-transmitter/receiver with BPSK modulation signals. The test-chip was implemented by mixed-signal 0.35-µm CMOS technology. We measured the test chip and confirmed basic operations of these blocks. The chopper-amplifier achieved 66-dB DC gain, bandwidth of 400 kHz, and 4-µV noise with power dissipation of 6-mW with a 3-V supply. We observed real nerve signals in a living cricket using the proposed chopper amplifier. ADC achieved 52-ksps operation with power dissipation of 0.43-mW at 3-V supply. The wireless transmitter achieved 1-Mbps data transmission at a distance of 1-m with 1.5-mW power dissipation at 3-V supply.

A robust watermarking scheme based on the time-spread echo method is proposed in this letter. The embedding process is achieved by subband decomposition of a host signal and by controlling the amount of distortion, i.e., power of watermark, of each subband according to the Signal to Mask Ratio (SMR) calculated from MPEG psychoacoustic model. The decoding performance and robustness of the proposed method were evaluated.

In this paper, a test method is proposed to detect lead opens in CMOS LSIs. The test method is based on supply current which flows when test input vectors and AC electric field are provided from the outside of the ICs. Also, an application method of the test input vectors is proposed in this paper. It is shown experimentally that lead opens of SSIs and LSIs will be detected by providing each of the test input vectors per the period of AC electric field applied.

A simple method has been proposed for the measurement of the output power and phase characteristics of the 3rd-order inter-modulation distortion (IM3) components appearing in multistage power amplifiers. By adopting a unique definition of the phase for the IM3 components that is independent of the delay time caused by transmission lines and other instrument devices, it is possible to measure the phase, merely by using a vector signal analyzer. It is demonstrated that an accurate estimation of the IM3 characteristics of two-stage cascaded power amplifiers for cellular radio handheld terminals can be made by using the IM3 characteristics of the 1st and 2nd-stage amplifiers as measured by the proposed method. The results indicate that it is possible to reduce the dissipation power by 18% at 28 dBm RF output power with respect to conventional measurement methods. Further studies show that the error in the resultant vector of the estimated IM3 is less than 1 dB, when the asymmetry characteristics of the IM3 sidebands in the 2nd-stage amplifier are less than 7.3%.

In this paper, we derive expressions for the bit error probability of QPSK/OFDM on frequency-selective Rayleigh fading channels. In the OFDM system, ICI (interchannel interference) caused by Doppler spread of the channel degrades the error performance of the system and introduces the error floor even for coherent detection. Analysis results show that the error performance of QPSK/OFDM can be degraded as the normalized maximum Doppler frequency fD /Bsub is increased where fD is the maximum Doppler frequency and Bsub is the subchannel bandwidth. Computer simulations confirm the theoretical analysis results for BPSK and QPSK signals.

Illegal distribution of signed documents can be considered as one of serious problems of digital signatures. In this paper, to solve the problem, we propose three protocols concerning signature schemes. These schemes achieve not only traceability of an illegal user but also universal verifiability. The first scheme is a basic scheme which can trace an illegal receiver, and the generation and tracing of a signed document are simple and efficient. However, in this scheme, it is assumed that a signer is honest. The second scheme gives another tracing method which does not always assume that a signer is honest. Furthermore, in the method, an illegal user can be traced by an authority itself, hence, it is efficient in terms of communication costs. However, in this scheme it is assumed that there exists only a legal verification algorithm. Thus, in general, this scheme cannot trace a modified signed document which is accepted by a modified verification algorithm. The third one is a scheme which requires no trusted signer and allows a modified verification algorithm. It can trace an illegal receiver or even a signer in such a situation. All of our schemes are constructed by simple combinations of standard signature schemes, consequently, one can flexibly choose suitable building blocks for satisfying requirements for a system.

We propose a burst optical packet generator based on a novel photonic parallel-to-serial conversion scheme, and demonstrate 40-Gbit/s 16-bit optical packet generation from 16-ch parallel low-voltage TTL data streams. It consists of electrical 4:1 parallel-to-serial converters that employ InP metal-semiconductor-metal photodetectors, and an optical time-domain multiplexer with electroabsorption modulators. The proposed optical packet generator is suitable for burst optical packet generation and overcomes the electronic bandwidth limitation, which is prerequisite for achieving high-speed photonic packet switched networks. In addition, it can be driven by simple low-cost low-power CMOS logic circuits, and is compact and extensible in terms of the number of input channels due to the effective combination of electrical and optical multiplexing.

A band-pass delta-sigma modulator (BPDSM) is a key building block to implement a digital intermediate frequency (IF) receiver in a wireless communication system. This paper proposes a time-interleaved (TI) switched-capacitor (SC) BPDSM architecture that consists of 5-stage TI blocks with recursive loop. The proposed TI BPDSM provides reduction in the clock frequency requirement by a factor of 5 and relaxes the settling time requirement to one-fourth of conventional approach. The test chip was designed and fabricated for a 30-MHz IF system with a 0.35-µm CMOS process. The measured peak SNR for a 200-kHz bandwidth is 63 dB while dissipating 75 mW from a 3.3-V supply and occupying 1.3 mm2.

This paper is focused on the measurement of the complex permittivity of a liquid phantom by the transmission line method using a coaxial line for measuring high-permittivity and high-loss materials. First, the complex permittivity of the liquid phantom material is measured under various physical lengths of the coaxial line for accurate measurement. Secondly, comparison between the measured result and the result obtained by the coaxial probe method is carried out in the frequency range from 0.5 to 3 GHz. Finally, the measurement error included in the complex permittivity is estimated quantitatively. The discussions lead to the conclusion that accurate measurement of the liquid material with high-permittivity and high-loss is possible by the presented method.

We proposed a one-way trapdoor permutation f based multi-signature scheme which can keep tighter reduction rate. Assuming the underlying hash functions are ideal, our proposed scheme is not only provably secure, but are so in a tight. An ability to forge multi-signatures with a certain amount of computational resources implies the ability to invert a one-way trapdoor permutation f (on the same size modulus) with about the same computational effort. The proposed scheme provides the exact security against Adaptive-Chosen-Message-Attack and Adaptive-Insider-Attack by . can also attack in key generation phase, and act in collusion with corrupted signers.

This letter evaluates the peak-to-average power ratio (PAR) performance in a space-time block coded (STBC) multicode CDMA (MC-CDMA) system using a selected mapping (SLM) approach. The ordinary method is to apply the SLM scheme for each transmit antenna individually, while the investigated SLM-based STBC MC-CDMA system selects the transmitted sequence with the lowest average PAR over all transmit antennas concurrently. SLM-based STBC MC-CDMA system retrieves the side information very accurately at the expense of a slight degradation of the PAR performance, which can improve the overall detection performance of the STBC MC-CDMA system in the presence of erroneous side information compared to the ordinary SLM approach.

This paper provides methods for construction of pairing-based cryptosystems based on non-supersingular elliptic curves.

Multiuser diversity, identified by recent information theoretic results, is a form of diversity inherent in a wireless network. The diversity gain is obtained from independent time-varying fading channels across different users. The main practical issue in multiuser diversity is lack of Quality of Service (QoS) guarantees. This study proposes a wireless scheduling algorithm named MUDSEQ for downlink channels exploiting multiuser diversity under explicit QoS constraints. The numerical results demonstrate that the novel algorithm can yield non-negligible diversity gain even under tight QoS constraints and little scattering or slow fading environments. Additionally, a system framework for dynamic resource allocation based on the proposed algorithm is developed.

A novel method for measuring microwave reflection coefficients without the open and load standards is proposed. In this method, a single probe is inserted into an air line and the output wave is detected by a vector detector. Offset shorts are used for the calibration. The measurement system is constructed using 7 mm coaxial line and APC7 connectors. The result of the measurement in the frequency range 1-9 GHz shows the possibility of the proposed method. All the major systematic errors can be estimated from the data that is easily obtainable.

In wireless communication systems where users compete for limited bandwidth, radio resource control is essential for throughput enhancement and delay reduction. In this paper, we present a game-theoretical approach to distributed resource control in CDMA systems. Incomplete information about channel conditions is considered. The resource control problem is formulated as a noncooperative game of incomplete information, with which the existence and uniqueness of the Bayesian Nash equilibrium (BNE) of the game is investigated. Since the equilibrium is Pareto inefficient, we propose a pricing policy to the resource control game by adding a penalty price to user's transmission cost. With the adoption of the price, user's aggressive behavior is depressed, and Pareto improvement is achieved. Also the Pareto efficient BNE of the game with pricing is studied. Simulation results show that users can obtain higher throughput and lower average packet transmission delay by proper pricing policy. It is also verified that the scheme of pricing policy is robust when information of channel conditions is inaccurate.

We consider a new post-filtering algorithm for residual acoustic echo cancellation in hands-free application. The new post-filtering algorithm is composed of AR analysis, pitch prediction, and noise reduction algorithm. The residual acoustic echo is whitened via AR analysis and pitch prediction during no near-end talker period and then is cancelled by noise reduction algorithm. By removing speech characteristics of the residual acoustic echo, noise reduction algorithm reduces the power of the residual acoustic echo as well as the ambient noise. For the hands-free application in the moving car, the proposed system attenuated the interferences more than 15 dB at a constant speed of 80 km/h.

Recent advances in measurement techniques for microwave active devices and circuits are reviewed in this paper. The R&D activities have been devoted aggressively how to characterize nonlinear performance of high power devices and circuits. They are pulsed I-V, a variety of load-pull measurements, probing, sampling, and sensing techniques, supported by the recent significant advances in DSP (Digital Signal Processing), RF components, semiconductor devices, etc. The recent advances in vector network analyzers are of our great interest. They are (a) multi-port vector network analyzers for characterizing mixers, differential devices, packaged components, electronic package characterization, and multi-layer transmission lines, and (b) EO (Electro-Optic) modulated vector network analyzers for characterizing electronic performance of EO devices with the aid of EO modulators and photonic probes. In addition, probing, sampling, and sensing techniques have made great progress to directly measure electromagnetic field, time-domain voltage waveform, and temperature in small spot areas. In this paper, some topics related to these measurement techniques are briefly reviewed. Then the existing and future issues for characterization and measurement techniques of microwave active devices and circuits are discussed.