In this paper, a hierarchical bit mapping (HBM) scheme suitable for M-level quadrature amplitude modulation (M-QAM) packet transmission is presented. Generally, M-QAM, such as 16QAM or 64QAM, consists of multiple bits with differing bit error-rate quality. Because the packet error rate when using M-QAM is highly dependent on the performance of the "weakest" (poor quality) bits, the throughput of M-QAM packets can dramatically deteriorate especially in a multi-path environment. This paper proposes the use of a bit mapping scheme conceptually similar to hierarchical QAM to improve packet transmission throughput. For 16QAM under this scheme for example, as there are four bits in a 16QAM symbol, four independent packets can be simultaneously transmitted on each of the different bits when HBM is used. In doing so, at least two packets can be transmitted with a high probability of success even under poor transmission conditions, and under good transmission conditions, four packets can potentially be successfully transmitted. An interference cancellation (IC) method is then presented for HBM, with simulation results showing that the combination of HBM with IC results in very good performance. It was also determined that the HBM scheme can be used easily and effectively with hybrid ARQ.

This paper presents the results of field experiments on the pilot symbol assisted (PSA) coherent multistage interference canceller (COMSIC) receiver in the direct sequence code division multiple access (DS-CDMA) reverse link. The implemented COMSIC receiver comprising three cancellation stages employs PSA channel estimation and replica generation of multiple access interference (MAI) of other users. The experimental results demonstrate that the COMSIC receiver associated with antenna diversity reception and fast transmission power control (TPC) exhibits effectiveness in suppressing severe MAI in actual multipath fading channels. The transmission power of a mobile station (MS) when the COMSIC receiver is employed at a base station (BS) is reduced by approximately 2.0 and 4.0 dB compared to that with the matched filter (MF)-based Rake receiver when the ratios of the target signal energy per bit-to-interference power spectrum density ratio (Eb/I0) of the desired user to the target user are Δtarget= -6 and -9 dB, respectively. Furthermore, for the COMSIC receiver, the transmission power of a MS at the average bit error rate (BER) of 10-3 with antenna diversity is decreased by approximately 7.5 and 11 dB compared to that without antenna diversity when the Δtarget values are -6 and -9 dB, respectively.

Using the finite-difference time-domain method, we evaluated the performance of apertured near-field fiber probes with a double-tapered structure, which have exhibited, in recent experiments, a much higher collection efficiency of localized light in comparison with single-tapered probes. We clarified that this high collection efficiency could be attributed to the shortening of the cutoff region, and the efficient coupling to the guiding mode of the optical fiber. By reproducing the experimental results in terms of the spatial resolution and the collection efficiency as a function of the aperture diameter, our calculation was confirmed to be valid and useful for the design of probes in a variety of applications.

In an orthogonal frequency division multiplexing (OFDM) system, the bit error performance is degraded in the presence of multiple propagation paths whose excess delays are longer than the Guard Interval (GI), because the orthogonality between subcarriers cannot be maintained. In this paper, we propose a new OFDM demodulation method with a variable-length effective symbol and a multi-stage inter-carrier interference (ICI) canceller, in order to improve the bit error performance in the presence of multipaths whose excess delays are longer than the GI. The influence of the inter-symbol interference (ISI) is eliminated by the variable-length effective symbol, and then the ICI component is reduced by the multi-stage ICI canceller. The principle of the proposed method is explained, and the performance of the proposed method is then evaluated by computer simulation. The results show that the proposed method improves the system availability under more various multipath fading environments without changing the system parameters.

Scanning near-field optical microscopy (SNOM) combined with Kelvin force microscopy (KFM) using a microfabricated force-sensing cantilever with a lead zirconate titanate (PZT) thin film as an integrated deflection sensor have been developed. We applied the frequency modulation (FM) detection method to this setup to increase the detection sensitivity of electrostatic forces between a probe tip and a sample. Latex particles dispersed in a polyvinylalcohol (PVA) thin film deposited onto a glass substrate were stably imaged with the SNOM while both local optical and electrical properties of a ferroelectric thin film were successfully investigated.

This paper presents a method of extracting car license plates captured from the arbitrary directions by using symmetry features. The generalized symmetry transform (GST) produces continuous features of symmetry between two points by combining locality constraint and reflectional symmetry, but its time complexity of GST is increased by the second power of the radius of a searching window. To achieve considerable reduction of this time complexity, we propose a scan line based GST (SLGST) which calculates the symmetry between a pair of edge pixels along the scan lines. Instead of calculating the global symmetry of a license plate, we assign the symmetry contribution acquired from SLGST to the corner point estimated from two edge points and their gradient orientations. The right angle tuned SLGST (RATSLGST) is newly proposed to detect the right angle corners more effectively. Image normalization by image warping is adopted to make such segmentation of license plate and later identification much easier. We also adopt the verifier that evaluates a candidate license plate to enhance extraction rate. Our experiments show that the proposed method for extracting perspectively distorted license plates is fairly reliable.

In this paper, the performance of multi-stage parallel interference cancellation receiver using forward-backward filtering channel estimation is evaluated for the W-CDMA uplink. The channel estimation employs a non-causal forward-backward-multiplication-method filter, which was originally proposed for the reception of W-CDMA random access. Results of link level simulations for data and voice traffic scenarios over Pedestrian A and Vehicular A channels are discussed in comparison with the conventional channel estimation methods of 1-slot pilot averaging, 1-slot averaging, and weighted multiple slot averaging. It is shown that the forward-backward filtering channel estimation improves performances of the interference cancellation receiver as well as that of the ordinary Rake receiver in both Pedestrian A and Vehicular A channels. With its features of short processing delay and low complexity, the forward-backward filtering channel estimation is suitable for practical implementations of multi-stage interference cancellation receivers.

An n-detection testing for stuck-at faults can be used not only for delay fault testing but also for detection of unmodeled faults. We have developed a hybrid BIST circuit; that is, a method consisting of a shift register with partial rotation and a procedure that selects test vectors from ATPG ones. This testing method can perform at-speed testing with high stuck-at fault coverage. During the at-speed testing, a subset of the ATPG vectors is input by using a low-speed tester. Computer simulations on ISCAS'85, ISCAS'89, and ITC'99 circuits are conducted for n = 1, 2, 3, 5, 10, and 15. The simulation results show that the amount of test vectors can be reduced to ranging from 52.3% to 0.9% in comparison with that of the ATPG vectors. As a result, the proposed method can reduce the cost of at-speed testing.

This paper presents a test vector modification method for reducing average power dissipation during test application for a full-scan circuit. The method first identifies a set of don't care (X) inputs of given test vectors, to which either logic value 0 or 1 can be assigned without losing fault coverage. Then, the method reassigns logic values to the X inputs so as to decrease switching activity of the circuit during scan shifting. Experimental results for benchmark circuits show the proposed method could decrease switching activity of a given test set to 45% of the original test sets in average.

In this paper, we focus on an image encryption scheme based on a truncated Baker transformation. The truncated Baker transformation globally preserves the original dynamics of Baker transformation but incorporates a random local rotation operator between two neighbor elements in the mapping domain in order to keep a finite precision. It generates binary sequences (the dynamics of elements) which have statistically good features on ergodicity, mixing and chaotic properties. The image encryption scheme extended from the truncated Baker transformation efficiently shuffles the input gray level image satisfying fundamental conditions on confusion and diffusion required for image encryption schemes. However, this scheme uses many binary sequences and thus needs to keep a large volume of secret keys. In order to solve this problem we introduce Peano space-filling curve in this scheme, which remarkably reduce the key size and mapping iterations without deteriorating good shuffling properties attained by this scheme.

In loudspeaker-based 3D audio systems, there are some acoustic crosstalk cancellation methods to enlarge the 'sweet spot' around a fixed listener position. However, these methods have common defect that most of them can be applied only to the specific narrow frequency band. In this letter, we propose the more robust acoustic crosstalk cancellation method so that we can cancel the crosstalk signal in far wider frequency band and enlarge 'sweet spot. ' For this goal, we apply a sum and difference filter to the conventional three loudspeaker-based 3D audio system.

This paper introduces an improved multistage parallel interference cancellation (PIC) technique that uses the reverse-link synchronous transmission technique (RLSTT) to improve the estimation of data at the initial stage. Because the subtraction of an interfering signal based on an incorrect bit decision quadruples the interference power for that signal, the relatively high decision bit error rate (BER) may lead to a poor cancellation or even a higher BER at the following stages. The RLSTT is a robust approach which takes into account the fact the tentative decision at the earlier stages is less reliable than the following stages and makes the earlier cancellation more reliable. The analysis demonstrates that a better transmission performance can be achieved by using the RLSTT at the initial stage of PIC.

This paper proposes a multipath interference canceller (MPIC) for orthogonal code multiplexed channels in the W-CDMA forward link and evaluates by computer simulation the improvement in BER performance owing to the multipath interference (MPI) suppression effect obtained by the MPIC. The simulation results show that a one-stage MPIC, which removes the MPI from the common pilot channel (PICH), common control channel (CCH), and synchronization channel (SCH), achieves a sufficient MPI suppression effect, and that the required received Eb/N0 of the traffic channel (TCH) at the average BER of 10-3 using the MPIC for the common channels is decreased by approximately 6.5 dB compared to that with a matched filter (MF)-based Rake receiver (the transmit power ratio of each common channel to TCH: ΔPICH/TCH=0 dB, ΔCCH/TCH=5 dB, ΔSCH/TCH=3 dB, without fast transmit power control (TPC) and antenna diversity reception). We also show that by using MPIC, the required transmit Eb/N0 at the average BER of 10-3, when the ratio of the target Eb/I0 of the 9-interfering users to desired user is ΔInt/Des=6 dB with fast TPC, is increased by only approximately 0.6 dB compared to that when ΔInt/Des=0 dB. This implies that the preferential MPI suppression from high-rate TCHs that abates the increase in complexity in a mobile terminal is effective in increasing the link capacity in the forward link.

This paper presents a comparison of the throughput performance employing hybrid automatic repeat request (HARQ) with packet combining, such as Type-I with packet combining (simply Chase combining hereafter) and Type-II (Incremental redundancy hereafter), using turbo coding in a multipath fading channel in high speed downlink packet access (HSDPA). We apply a multipath interference canceller (MPIC) to remove the influence of severe multipath interference. Link level simulation results show that the maximum throughput using Incremental redundancy with 64QAM is improved by approximately 5-8% compared to that using Chase combining, and that the required average received signal energy of 12 code channels per chip-to-background noise spectrum density (Ec/N0) at the throughput of 4 Mbps with Incremental redundancy is decreased by approximately 1.0 dB rather than that with Chase combining when the vehicular speed is higher than approximately 30 km/h. Furthermore, we elucidate based on the system level simulation that although no improvement is obtained in a slow mobility environment such as the average vehicular speed of 3 km/h, the achieved throughput of Incremental redundancy is increased by approximately 5-6% and 13% for the average vehicular speed of 30 km/h and 120 km/h, respectively, compared to that with Chase combining.

The optical recording on an azopolymer surface by the optical fiber probe with a 100 nm diameter aperture was demonstrated. The 150 nm diameter pit was formed by the optical fiber probe coupled with a 50 ns pulse of 10 mW and 488 nm wavelength coherent light.

A method for estimating propagation characteristics is described that uses the characteristics of pilot-data-inserted orthogonal frequency division multiplexing (OFDM) signal and is suitable for high-mobility OFDM transmission scheme. Several pilot data are inserted periodically along the frequency axis before the inverse fast Fourier transformation (IFFT) process in the transmitter. At the receiver, the received OFDM signal is correlated with a prepared distinctive OFDM signal in which several pilot data are inserted in the same positions as in the transmitted OFDM symbols and zeros are inserted in the other positions. The propagation characteristics can be estimated precisely and used to cancel any interference caused by delayed waves. Computer simulation shows that this method can estimate the propagation characteristics, which can then be used to cancel the interference caused by delayed waves before the FFT at the receiver under fast multipath fading conditions.

Iterative schemes for demodulating M-ary orthogonal signaling formats in direct-sequence code-division multiple access (DS-CDMA) systems are proposed and compared with the standard noncoherent matched filter receiver. Interference cancellation, i.e., (approximative) removal of the multiple access interference (MAI) by means of subtraction is studied. The considered system is similar to the uplink (reverse link) of an IS-95 system. Hence, the received signals from the concurrent users are asynchronous, and no pilot signals are available for channel estimation. A decision-directed algorithm is proposed for estimating the time-varying complex channel gains of a multipath channel. The receivers are evaluated on Rayleigh-fading channels and are shown to provide large capacity gains compared with the conventional receiver.

We introduce PC Linux cluster computing techniques to an Evolutionary Graph Generation (EGG) system, and successfully implement the parallel version of the EGG system, called PEGG. Our survey satisfactorily shows that the parallel evolutionary approach meets our expectation that the final solutions obtained from PEGG will be as good as or better than those obtained from EGG, and that PEGG can ultimately improve the speed of evolution.

In this paper, we propose an activity-based estimation scheme to determine the received signal power disparity, that enhances the BER performance of the SIC scheme in a DS/CDMA system considering a practical voice activity factor, and compare BER performance with those of other schemes with or without estimation. Numerical analysis results show that the SIC scheme with the proposed activity-based estimation improves the BER performance compared with that without considering voice activity, and it approaches to that of the ideal estimation as the total number of concurrent users increases. In addition, the higher becomes the maximum attainable SNR, the better becomes the BER performance of the proposed activity-based estimation scheme.

A fully on-chip active guard band circuit is proposed. The proposed circuit is mainly composed of current mirrors and based on a DC bias technique. HSPICE simulations and experiment results confirm the validity of the proposed active guard band circuit.