Since Ultra Wideband Impulse Radio (UWB-IR) system can resolve many paths and is thus rich in multipath diversity, the use of Rake diversity combining is very effective. In the Rake diversity combining, the bit error rate (BER) is improved with the increase of the number of fingers. The Pre-Rake diversity combining is known as another technique to achieve the performance equivalent to the Rake diversity combining without increasing the receiver complexity. In the Pre-Rake diversity combining, the transmitted signals are scaled and delayed according to the delay and strength of the multipath. In this paper, we propose Pre-Rake diversity combining techniques for UWB systems, All-Pre-Rake (A-Pre-Rake) diversity combining using perfect channel information, Selective-Pre-Rake (S-Pre-Rake) diversity combining using the information on the L strongest paths, and Partial-Pre-Rake (P-Pre-Rake) diversity combining using the information on the first L paths. From the results of our computer simulation for UWB-IR systems in IEEE 802.15 UWB multipath channel model, we show that the proposed Pre-Rake diversity combining techniques are effective for the UWB-IR systems to achieve good error rate performance, while keeping the complexity of the receiver low. We also show that the S-Pre-Rake diversity combining is effective to achieve good error rate performance with less channel information.

This paper reports on the bending loss insensitive single mode fiber suitable for access networks, which is applicable for wide wavelength use. Excellent attenuation stability of the fiber in the full spectrum range has been confirmed even in severe conditions such as fiber handling in mid-span access at aerial closure, cable installation/handling in indoor wirings and so on. Also, applications suitable for FTTH subscribers' use have been introduced.

The new design with minimum loop inductance suitable for the measurements at high frequencies with substrate bias is described. These test structures allow characterizing 4-terminal MOSFETs with a standard two-port Network Analyzer. The high-frequency behavior of bulk effect in MOSFETs is studied at different bias conditions for a 0.18 µm RF CMOS technology. The BSIM3 extension RF MOSFET modeling with bulk effect is verified and analyzed from two-port Y-parameter results. The result of RF NMOSFET shows that a good accuracy of the 4-terminal RF MOSFET modeling is achieved.

We implemented all-fiber delay line using linearly chirped fiber Bragg gratings (CFBG), which can be applicable for reflectometry or optical coherence tomography (OCT). Compared with the previously reported delay lines, the proposed fiber-based optical delay line has in principle novel advantages such as automatic dispersion cancellations without additional treatment and a gain in optical delay that is dependent on parameters of used CFBGs. Dispersion compensation in optical delay line (ODL), which is the indispensable problem in bulk optics based ODL, is demonstrated in fiber by using two identical but reversely ordered CFBGs. Amplified variable optical delay of around 2.5 mm can be obtained by applying small physical stretching of one of CFBGs in the proposed scheme. The operational principles of the all-fiber variable optical delay line, which are based on the distributed reflection characteristic of a CFBG employed, are described. Especially properties such as in-line automatic dispersion cancellation and amplified optical delay under strain are dealt. To demonstrate the properties of the proposed scheme, which is theoretical consequences under assumptions, an all-fiber optical delay line have been implemented using fiber optic components such as fiber couplers and fiber circulators. With the implanted ODL, the group delay and amplified optical delay length was measured with/without strain. The wavelength independent group delay measured within reflection bandwidth of the CFBG has proved the property of automatic dispersion cancellations in the proposed fiber delay line. Optical delay length of 2.5 mm was obtained when we apply small physical stretching to the CFBG by 100 µm and this is expressed by the amplification factor of 25. Amplification factor 25, which is less than theoretical value of 34 due to slipping of fiber in the fiber holder, shows that the proposed scheme can provide large optical delay with applying small physical stretching to the CFBG. We measure slide glass thickness to check the performance of the fiber delay line and the good agreement in measured and physical thickness of slide glass (1 mm thick) validates the potential of proposed delay line in the applications of optical reflectometry and OCT. We also discuss the problem and the solution to improve the performance.

A space-time RAKE (ST-RAKE) receiver with a blind interference-blocking (IB) pre-processor, termed as the IB-RAKE receiver, is proposed for spread spectrum communications systems. The design of the proposed architecture consists of three components. A blind IB transformer is first constructed based on the received data, and then applied on the undespread data for the suppression of strong interference. After despreading, optimal beamforming is then performed on the IB despread data to extract the signals of interest (SOIs) from the desired user. Finally, a RAKE receiver with a maximum ratio combining technique is employed to constructively collect all the SOI energies. Since strong interference has been removed in the first stage, the RAKE receiver combines only those SOIs plus negligible interference, leading to robustness against strong interference. Numerical results have shown that substantial improvement can be obtained from the proposed ST-RAKE receiver with the blind IB pre-processing scheme.

A topological book embedding of a graph is an embedding in a book that carries the vertices in the spine of the book and the edges in the pages; edges are allowed to cross the spine. Enomoto showed that for any graph G having n vertices, there exists a three-page book embedding of G in which each edge crosses the spine log n times. This paper generalizes the result and shows that for any graph G having n vertices, there exists a d + 1-page book embedding of G in which each edge crosses the spine logd n times.

"Can one walk to infinity on Gaussian primes taking steps of bounded length?" We adopted computational techniques to probe into this open problem. We propose an efficient method to search for the farthest point reachable from the origin, which can be parallelized easily, and have confirmed the existence of a moat of width k =, whereas the best previous result was k = due to Gethner et al. The amount of computation needed for k = is about 5000 times larger than that for k =. A refinement of Vardi's estimate for the farthest distance reachable from the origin is proposed. The proposed estimate incorporates discreteness into Vardi's that is based on percolation theory.

This paper presents a novel data transmission protocol "SVFTP," which enables high-speed and error-free video data transmission over IP networks. A video transmission system based on SVFTP is also presented. While conventional protocols are designed for file transmission, SVFTP focuses on video data as a continuous media. In order to fit a flexible video transmission system, SVFTP achieves higher throughput on the long distance link as well as transmission interruption/resumption and progressive download and play back. In addition, a rate shaping mechanism for SVFTP is introduced in order to control greediness and burst traffic of multiple-TCP sessions. Laboratory and field transmission experiments show that SVFTP achieves high performance and functionality.

This paper proposes a new angular measurement system to a moving target in the presence of clutter. We apply MUSIC (MUltiple SIgnal Classification) to the outputs of a Doppler filter bank consisting of quadrature mirror filter (QMF). The comparison between QMF and the short time Fourier transform (STFT) as a preprocessor of MUSIC is also discussed. DOA estimation performance by QMF-MUSIC is nearly equal to that of STFT-MUSIC. On the other hand, QMF-MUSIC overcomes STFT-MUSIC in the aspect of computational cost. In a specific example in this paper, the proposal QMF bank by Daubechies (4th order) wavelet requires 80% fewer the number of multiplications and 25% fewer the number of additions than the FFT-based STFT filter bank.

SOBER-128 is a stream cipher designed by Rose and Hawkes in 2003. It can be also used for generating Message Authentication Codes (MACs) and an authenticated encryption. The developers claimed that it is difficult to forge MACs generated by both functions of SOBER-128, though, the security assumption in the proposal paper is not realistic in some instances. In this paper, we examine the security of these message authentication mechanisms of SOBER-128 under security channel model. As a result, we show that both a MAC generation and an authenticated encryption are vulnerable against differential cryptanalysis. The success probabilities of the MAC forgery attack are estimated at 2-6 and 2-27 respectively. In addition, we show that some secret bits are revealed if a key is used many times.

In this paper, we propose a global routing method for 2-layer BGA packages. In our routing model, the global routing for each net is uniquely determined by a via assignment of each net. Our global routing method starts from an initial monotonic via assignment and incrementally improves the via assignment to optimize the total wire length and the wire congestion. Experimental results show that our proposed method generates a better global routing efficiently.

In this paper, a new 2-antenna transmit diversity, called orthogonal space-time spreading transmit diversity (OSTSTD) combined with delay transmission, is proposed. At the transmitter, N data symbols to be transmitted are spread using N different orthogonal space-time spreading codes (each represented by NN matrix) and are transmitted from two transmit antennas after adding different time delays. At the receiver, 2-step space-time despreading is carried out to recover the N transmitted data symbols. The first step recovers the N orthogonal spatial channels by taking the correlation between the received space-time spread signal and the time-domain spreading codes. The second step recovers the N transmitted data symbols using minimum mean square error (MMSE) despreading. The average bit error rate (BER) performance in a Rayleigh fading channel is evaluated by computer simulation. It is confirmed that the OSTSTD provides better BER performance than the Alamouti's space-time transmit diversity (STTD) at the cost of transmission time delay.

Recent progress and achievements in creating single fundamental mode vertical cavity lasers with the technique of etching a 2-dimensional pattern of photonic crystal holes into the top distributed Bragg reflector are described. A simulation method for the design of single mode lasers is described, along with accuracy and limitations in predicting modal properties in these devices. Progress in improving output power, methods of lowering threshold currents, and small signal modulation of single mode lasers are discussed.

We report the empirically obtained conditions for the fusion splicing with photonic crystal fibers (PCF) having large mode areas. By controlling the arc-power and the arc-time of a conventional electric-arc fusion splicer, the splicing loss between two PCFs could be lowered down to 0.2 dB in average. For the splicing PCF with a conventional single mode fiber (SMF), the loss was increased due to the modal field mismatch, but still below 0.45 dB in average. The tensile strength was weakened by the splicing from 2.83 GPa down to 1.04 GPa for the PCF-PCF case and 0.89 GPa for the PCF-SMF one.

To understand radio propagation structures and consider signal recovering techniques in mobile communications, it is most effective to estimate the signal parameters (e.g., DOA) of individual incoming waves. Also, in radar systems, it is required to discriminate the desired signal from interference. As one of the high-resolution DOA estimators, MUSIC and ESPRIT have attracted considerable attention in recent years. They need the eigenvectors of the correlation matrix and therefore we have to execute the EVD (eigenvalue decomposition) of correlation matrix. However, the EVD generally brings us a heavy computational load and as a result it is difficult to realize the real-time DOA estimator, which will be useful as a multibeam-forming algorithm for adaptive antennas. This paper focuses on MUSIC and ESPRIT using subspace tracking methods, such as BiSVD, PAST, and PASTd, to carry out iterative DOA estimation. Then, they are compared through computer simulation. Adaptive beamforming based on DCMP and MLM is also mentioned and an example is shown.

We present measurements of Gate-Induced-Drain-Leak-age at various temperatures and terminal biases. Besides Band-to-Band tunneling leakage observed at high Drain-to-Gate voltage VDG, we also observed Trap-Assisted-Tunneling leakage current at lower VDG. Based on ISE TCAD simulations of the electric field, we propose analytical models for Band-to-Band and Trap-Assisted Gate-Induced-Drain-Leakage currents suitable for compact modeling.

The XTR public key cryptosystem was introduced in 2000. XTR is suitable for a variety of environments including low-end smart cards, and is regarded as an excellent alternative to RSA and ECC. Moreover, it is remarked that XTR single exponentiation (XTR-SE) is less susceptible than usual exponentiation routines to environmental attacks such as the timing attack and the differential power analysis (DPA). This paper investigates the security of side channel attack (SCA) on XTR. In this paper, we show the immunity of XTR-SE against the simple power analysis if the order of the computation of XTR-SE is carefully considered. In addition, we show that XTR-SE is vulnerable to the data-bit DPA, the address-bit DPA, the doubling attack, the modified refined power analysis, and the modified zero-value attack. Moreover, we propose some countermeasures against these attacks. We also show experimental results of the efficiency of the countermeasures. From our implementation results, if we compare XTR with ECC with countermeasures against "SCAs," we think XTR is as suitable to smart cards as ECC.

By using multiple transmit antennas, wireless systems have a large capacity in time-varying multipath fading channels. Space-time block code (STBC), space-frequency block code (SFBC), and space-time-frequency (STF) block code are well-known techniques in transmitter diversity schemes. While the SFBC (or the STF block coded) system gives full diversity at frequency-nonselective channels, it breaks down when used in a frequency-selective environment. This is because the SFBC (or the STF block code) scheme disregards frequency selectivity of the channel by assuming that channel frequency responses (CFRs) at adjacent subcarriers are the same. In this paper, we propose efficient channel estimation and symbol decoding methods, which consider the difference between CFRs at the adjacent subcarriers of the SFBC (or the STF block coded) orthogonal frequency division multiplexing (OFDM) system in multipath fading channels. The proposed method gives initial channel information by designing a simple training symbol, and the CFRs at all the subcarriers and the differences between the CFRs are easily calculated by using an interpolation method or a discrete Fourier transform (DFT) operation.

We show that the necessary and sufficient condition for the existence of a balanced C4-bowtie decomposition of the complete multi-graph λKn is λ(n - 1) 0 (mod 16) and n 7. Decomposition algorithms are also given.

In the cellular mobile communication systems, co-channel interference and Rayleigh fading degrade the transmission performance. Adaptive Array Antenna (AAA) can suppress interference and, at the same time, can cope with multi-path fading by using a wide antenna spacing resulting in low correlation of received signals in each antenna element. A feedback-type AAA was proposed for frequency division duplexed (FDD) systems, where mobile station measures channel characteristics and feed-backs them to the base station. In this paper, we extend the system by introducing 2-branch diversity reception at a mobile station, and study the influence of antenna element spacing at the base station and control delay time on bit error rate performance under a realistic propagation model.