By using the gain expansive and compressive characteristics of two FET to compensate for the phase shift at large signal, one can greatly improve Adjacent Channel Power Ratio (ACPR) of the power amplifier. This 3 to 5 dB improvement result was verified experimentally by selecting the biasing point and the gain level of the first and second stage amplifiers. This MCM circuit-level technique is more attractive to achieve low cost and good ACPR design. As examples, some novel high efficiency power amplifiers with good ACPR for the handset applications are developed by this method. Those mass producible 0.12 cc volume (7.87.82.0 mm) multi-chip module power amplifiers (MCM PA) employ state-of-the-art enhancement GaAs HJFET devices that need only a single power supply.

Physical limitation of the conventional longitudinal media has been actualized recent days according to the dramatic increase in storage area density with a growth ratio of more than 100%/year so that perpendicular recording is being watched with keen interest. Development in perpendicular recording media from the proposal to actual usage for HDD system are reviewed in terms of historical back ground, recent media design and preparation, new media proposal and recording performances, mainly basing on the author's results. In case of perpendicular media, physical limit of thermal stability could not be so serious but media noise reduction with sophisticated preparation method has been research topics as the breakthrough for the commercialization. Improvements on Co-Cr system alloy media were made by introducing proper additives and under layers so that a high storage density over 60 Gb/inch2 has been achieved. Far higher density up to 1 Tera bits/ inch2 is expected to be possible by using newly proposed Co/Pd multilayer or Fe-Pt metal compound films. It is prospected that breakthrough for the future progresses would be mechanical issues such as head medium spacing and tribology problems rather than magnetic properties of media.

This is a study on a certain group theoretic property of the set of encryption functions of a block cipher. We have shown how to construct a subset which has this property in a given symmetric group by a computer algebra software GAP4.2 (Groups, Algorithms, and Programming, Version 4.2). These observations on group structures of block ciphers suggest us that we may be able to set a trapdoor based on meet-in-the-middle attack on block ciphers.

In mobile broadcasting environments, an information server periodically broadcasts a set of data items to a large mobile client population at every broadcast cycle and mobile clients retrieve the data items they need upon arrival at the broadcast channel. In such environments, the cost of data delivery is independent of the number of clients. Many applications such as auctions and stock quotes perform read-only transactions that require the clients to read consistent and current data for accurate result. Previous concurrency control mechanisms designed for such environments ensure that the clients read consistent data, but they cannot ensure latest-bound currency which allows the clients to read the latest or most up-to-date data. In this paper, we propose an efficient concurrency control mechanism that ensures latest-bound currency as well as update consistency, which is appropriate for the mobile broadcasting environments. To ensure latest-bound currency, the server computes control information using "virtual" broadcast cycles. This control information is also used for checking update consistency. Thus, the proposed mechanism allows all data committed in current broadcast cycle to be broadcast. We have performed simulation experiments to measure transaction aborts in order to evaluate the performance of the proposed mechanism. The result confirms that the proposed mechanism produces no stale reads and also shows that the proposed mechanism generates less transaction aborts than previous mechanisms, which implies that we can get higher data currency without increasing data inconsistency.

A compact optically-fed radio access point module was developed that consists of a uni-traveling-carrier refracting-facet photodiode, a patch antenna, and an optical input interface. An output power from the photodiode was 1.4 dBm at a frequency of 5.88 GHz without any bias voltage.

This paper describes the results of a series of laboratory experiments for performance evaluations of our proposed Maximum Likelihood Sequence Estimation (MLSE) based interference canceller, the Interference Canceling Equalizer (ICE), which can cancel both co-channel interference (CCI) and inter-symbol interference (ISI). To verify the feasibility of ICE for the Japanese cellular communications system, a standard of which has been released under the name of Personal Digital Cellular (PDC) system, a prototype system was constructed using 27 TI TMS320C40 Digital Signal Processor (DSP) chips. The ICE prototype works in real-time on the PDC air interface, major specifications of which are π/4 QDPSK 21 k symbols/s 3-channel time-division multiple-access (TDMA). Two-branch diversity reception is used to enhance the signal detection performance of ICE. In the experiments, BER performances were evaluated using the prototype system. Under a single-path Rayleigh fading and a single CCI condition, the ICE receiver attains the BER of less than 310-2 with the negative values of the average CIR: for fD = 5 Hz and 40 Hz, the average CIR more than -20 dB and -10 dB, respectively. Under a double-path Rayleigh fading and a single CCI condition, the ICE receiver attains the BER of less than 1.510-2 with the negative values of the average CIR: for fD = 5 Hz and 40 Hz, the average CIR more than -20 dB and -10 dB, respectively. The laboratory test results suggest that the ICE receiver has potential for system capacity enhancement.

In order to ease the impact of the packet fragmentation problem and to avoid network congestion in TCP over UBR, packet discard schemes in ATM layer (such as PPD and EPD) have been proposed. These schemes drop packets before they reach their intended destinations if the network is congested and the packets are to be partially discarded. On the other hand, TCP also regulates data flow with its own flow control method. Due to restriction of data flow at the TCP layer, buffer space is not fully used in an ATM switch. In order to make use of more buffer resources, this paper generalizes the PPD and EDP schemes. From this generalization, an optimistic packet discard scheme named the "Probability-Based Delayed Packet Discard" (PDPD) scheme is proposed. Depending on a particular probability, this scheme sets a discard flag to delay actual discard operation. This paper presents the results of several simulated models to find out the potential of improvement of goodput by PDPD. The results of these simulations indicate that PDPD obtains higher goodput than ordinary schemes when the packet size is large and the input load is not light. This author concludes that a PDPD scheme should achieve effective goodput and link utilization while using more buffer resources effectively.

This paper describes how the image sequences taken by a stationary video camera may be effectively processed to detect and track moving objects against a stationary background in real-time. Our approach is first to isolate the moving objects in image sequences via a modified adaptive background estimation method and then perform token tracking of multiple objects based on features extracted from the processed image sequences. In feature based multiple object tracking, the most prominent tracking issues are track initialization, data association, occlusions due to traffic congestion, and object maneuvering. While there are limited past works addressing these problems, most relevant tracking systems proposed in the past are independently focused to either "occlusion" or "data association" only. In this paper, we propose the KL-IMMPDA (Kanade Lucas-Interacting Multiple Model Probabilistic Data Association) filtering approach for multiple-object tracking to collectively address the key issues. The proposed method essentially employs optical flow measurements for both detection and track initialization while the KL-IMMPDA filter is used to accept or reject measurements, which belong to other objects. The data association performed by the proposed KL-IMMPDA results in an effective tracking scheme, which is robust to partial occlusions and image clutter of object maneuvering. The simulation results show a significant performance improvement for tracking multi-objects in occlusion and maneuvering, when compared to other conventional trackers such as Kalman filter.

A trapdoor one-way function is an extended version of a zero-way permutation. A zero-way permutation was first introduced by Niemi-Renvall in Asiacrypt'94. In this paper we define the class of functions called no-way functions. This is an extended version of a zero-way permutation. Intuitively, a function f is no-way if, without trapdoor, both computing f and computing f-1 are hard. Li-Chida-Shizuya defined the notion of a no-way function, which is a provable-security version of a zero-way permutation. They also gave an example of a no-way function such that computing f and f-1 is proven to be as hard as breaking the Diffie-Hellman key exchange scheme. We redefine the notion of a trapdoor no-way function more preciously, classify no-way functions by the property of the trapdoor: common, separated and semi-separated trapdoor no-way, give a method for constructing trapdoor no-way functions from trapdoor one-way functions, and also give an example of trapdoor no-way functions.

In this paper, we propose a call arrival history-based location tracking strategy for a variable call arrival rate over time. The basis of the proposed strategy is a time-based location tracking strategy. A mobile terminal obtains the up-to-date information about changes in the call arrival rate by maintaining its call arrival history, from which it can calculate an appropriate timeout interval for a variable call arrival rate. We present a simple analytical model and numerical results to investigate its performance for both a fixed and a variable call arrival rate which is modeled by a Markov-modulated Poisson process.

For vacuum-UV (VUV) phosphor application such as plasma display panels (PDPs) and mercury free lamps, CaAl2O4:Eu2+ (CA:Eu2+) showing 440 nm blue emission was examined. A single phase CA:Eu2+ was obtained by two step firing technique. The photoluminescence (PL) spectrum shows blue shift compared to that of blue-emitting BaMgAl10O17:Eu2+ (BAM:Eu2+) phosphors. CA:Eu2+ phosphors with β-tridymite crystal structure show less luminance degradation on baking in comparison to the commercial BAM:Eu2+ phosphors under VUV excitation. The initial PL intensity of CA:Eu2+ (Eu: 2 mol%) powder phosphor excited by 147 nm light was found to be about 60% of the commercial BAM:Eu2+ and the luminance of test panel with CA:Eu2+ (Eu: 1 mol%) was 37.4 cd/m2. The low test panel luminance with CA:Eu2+ phosphor is partly caused by the poor spread characteristics of the phosphor slurry due to the large particle size distribution. With improvement of luminance efficiency and the powder characteristics, there is a possibility that CA:Eu2+ phosphors can be applied for PDPs.

Cellular Digital Packet Data (CDPD) provides wireless data communication services to mobile users by sharing unused RF channels with AMPS on a non-interfering basis. To prevent interference on the voice activities, CDPD makes forced hop to a channel stream when a voice request is about to use the RF channel occupied by the channel stream. The number of forced hops is affected by the voice channel selection policy. We propose analytic models to investigate the CDPD channel holding time for the the least-idle and random voice channel selection policies. Under various system parameters and voice channel selection policies, we provide guidelines to reduce the number of forced hops.

A Co/Pd multilayer film with perpendicular coercivity of 2.2 kOe and remanence ratio (SQ) of unity was prepared by electron beam evaporation in vacuum. In the MFM image of signal patterns of 4 kFRPI recorded using a ring-type MIG head, many reversed domains were observed. However, when the film was magnetized along the film normal direction using an electromagnet (H = -13 kOe), only few reversed magnetic domains were observed, which was consistent with SQ = 1. Therefore, the reversed domains in the signal patterns were induced in the recording process. dc erasing was also studied with the magnetic field inclined to the film normal. The domain structures were almost the same when the perpendicular component of the field was kept constant while the in-plane component was varied, implying that the in-plane field component did not contribute to the formation of the reversed domains. It was found that reversed magnetic domains were easily induced even by a weak reversing magnetic field applied along the film normal. Hence, although the possibility of an insufficient recording head field was not excluded, it seemed more likely that the reversed magnetic domains in the signal patterns were caused by some erasing effect of the ring-type MIG head. For a Co/Pd multilayer medium with a negative nucleation field in the perpendicular M-H loop, a stronger reversing field was needed to induce the reversed magnetic domains. No reversed magnetic domains were observed in the MFM image for signal patterns of 4 kFRPI in this medium, indicating that a negative nucleation field was effective to suppress the formation of reversed magnetic domains.

The medium noise of single-layer perpendicular recording media is known to be suppressed by reducing the magnetic domain size and achieving a higher squareness ratio (Mr/Ms = SQ) in the perpendicular M-H loop. The media with smaller domain sizes exhibit a small slope at Hc in the M-H loop due to exchange de-coupling between adjacent grains, which requires a sharp head field to acquire high recording performances. Reduction of the medium thickness would be effective for recording as only a sharp head field near the head surface could be used. Thus, the effects of reduced recording layer thickness in single-layer perpendicular recording media on read/write performances were investigated using Co/Pd multilayer media with a small loop slope having thickness, δ, of 46, 22 and 10 nm, and with a steeper loop slope having δ of 40 and 10 nm. It was found that the recording performance on small loop slope media could be improved in terms of signal level by reducing the recording layer thickness, which indicated that the recording on the media was sensitive to the recording head field. The results in the simulation analysis were similar to those obtained experimentally, indicating that the change in recording layer thickness could be mainly regarded as that in the head-medium spacing. Thinner media with steeper loop slopes could acquire a narrower dipulse width. The recording resolution of the present media, however, was determined under the influence of the domain structure and the size. Finally, for media with small loop slopes, the same SNR of 38 dB at 100 kFRPI was obtained for thicknesses of 22 and 10 nm, which was larger than that for a thick medium of 46 nm thickness by 8 dB. For both the steep loop slope media, the obtained SNR was 35 dB at 100 kFRPI.

We have developed a map-based approach that enables us to efficiently extract information about man-made objects, such as buildings, from aerial images. An image is matched with a corresponding map in order to estimate the object information in the image (i. e. , presence, location, shape, size, kind, and surroundings). This approach is characterized by using a figure contained in a map as an object model for a top-down (model-driven) analysis of an object in the aerial image. We determined the principal steps of the map-based approach needed to extract object information and update a map. These steps were then applied to obtain the locations of missing buildings and the heights of existing buildings. The extraction results of experiments using aerial images of Kobe City (taken after the 1995 earthquake) show that the approach is effective for automatically extracting building information from aerial images and for rapidly updating map data.

In this paper, we propose fast block matching criteria to reduce the implementation complexity of motion estimation in VLSI video coders. Based on generalized quantization of pixel difference measures, the block matching criteria combined with bitmap exclusive-OR (XOR) concept can be realized by short length adders and a multi-input binary counter. The proposed approach can be treated as a generalization of the pixel difference classification (PDC) criterion. Simulation results show that the proposed block-matching criteria along with various block search algorithms achieve better results than the PDC and obtain nearly the same performance as the mean absolute difference (MAD) criterion. However, the complete gate-level synthesis of the proposed matching criterion is much less than those of the MAD and the PDC in the VLSI implementation.

In this paper, the efficiency of transferring non-realtime data over Wireless ATM (WATM) networks is studied. Non-realtime services are sensitive to bit error as well as cell loss. The loss or error of a single cell due to congestion or a line error will result in the retransmission of the entire protocol data unit (PDU) by the end user in ATM networks. In WATM, cells are subject to the influences of noise. In this paper, we propose an adaptive cell checking controller (ACCC) for WATM networks to early find out error PDUs and to drop all remaining cells of these frames. The proposed ACCC only needs several bits overhead for each PDU of size of several Kilobytes. The removable percentage of an erroneous PDU by ACCC is analyzed. Simulation results show that compared with a conventional early packet drop mechanism, the proposed ACCC can achieve superior network utilization while keeping the minimum overhead in WATM networks.

The proliferation and development of cellular voice systems over the past several years has exposed the capabilities and the effectiveness of wireless communications and, thus, has paved the way for wide-area wireless data applications as well. The demand for such applications is currently experiencing a significant increase and, therefore, there is a strong call for advanced and efficient mobile data technologies. This article deals with these mobile data technologies and aims to exhibit their potential. It provides a thorough survey of the most important mobile packet data services and technologies, including MOBITEX, CDPD, ARDIS, and the emerging GPRS. For each technology, the article outlines its main technical characteristics, discusses its architectural aspects, and explains the medium access protocol, the services provided, and the mobile routing scheme.

The relationships between lattice orientation of the electron-beam evaporated MgO layer used as protecting layer for ac plasma displays (ac-PDPs) and the discharge characteristics of color ac-PDPs were investigated by the measurements of ion-induced secondary electron emission. It is proved that values of γi for MgO are large in the order of (220) orientation, (200) orientation, and (111) orientation, that is, γi(220) > γi(200) > γi(111). The values of φ for different lattice orientation are obtained by the measurements of thermionic emission and photo emission. The aging measurements for testing panels with the different lattice orientation of MgO layer revealed that performance of those panels are excellent in the order of (220), (200), and (111). In particular, luminance and luminous efficiency become larger in the order of (220), (200), and (111). It is pointed out that the degree of longevity, sustaining voltage, and memory margin for ac-PDPs with protecting materials as MgO are estimated by the measurements of γi.

We investigated the relationship between the film characteristics and the sputtering rate of the MgO protecting layer in AC-PDP. As possible elements for determining the sputtering rate, we considered the density, orientation, and surface morphology. With respect to the orientation, we found that the sputtering rate increased for the sequence of (200) < (220) < (111). However, we noticed that orientation and surface structure are not really decisive factors affecting the sputtering rate; the density of the film is most important.