In this paper, an efficient partial incremental redundancy (P-IR) scheme is proposed for an H-ARQ using block type low density parity check (B-LDPC) codes. The performance of the proposed P-IR scheme is evaluated in an HSDPA system using IEEE 802.16e B-LDPC codes. Simulation results show that the proposed H-ARQ using IEEE 802.16e B-LDPC codes outperforms the H-ARQ using 3GPP turbo codes.

A new class of sextic residue sequences of period prime p=4u2+27=6f+1 ≡ 3 ( mod 8) are presented. Their trace function representations are determined. And the exact value of the linear complexity is derived from the trace function representations. The result indicates that the new sextic sequences are quite good from the linear complexity viewpoint.

As a method to realize a high-speed communication in the home network, the power-line communication (PLC) technique is known. A problem of PLC is that leakage radiation interferes with existing systems. When OFDM is used in a PLC system, the leakage radiation is not sufficiently reduced, even if the subcarriers corresponding to the frequency-band of the existing system are never used, because the signal is not strictly band-limited. To solve this problem, each subcarrier must be band-limited. In this paper, we apply the OQAM based multi-carrier transmission (OQAM-MCT) to a high-speed PLC system, where each subcarrier is individually band-limited. We also propose a pilot-symbol sequence suitable for frequency offset estimation, symbol-timing detection and channel estimation in the OQAM-MCT system. In this method, the pilot signal-sequence consists of a repeated series of the same data symbol. With this method, the pilot sequence approximately becomes equivalent to OFDM sequence and therefore existing pilot-assisted methods for OFDM are also applicable to OQAM-MCT system. Computer simulation results show that the OQAM-MCT system achieves both good transmission rate performance and low out-of-band radiation in PLC channels. It is also shown that the proposed pilot-sequence improves frequency offset estimation, symbol-timing detection and channel estimation performance as compared with the case of using pseudo-noise sequence.

We demonstrated all-optical demultiplexing of 160-Gb/s signal to 40- and 80-Gb/s by a Mach-Zehnder Interferometric all-optical switch, where the picosecond cross-phase modulation (XPM) induced by intersubband excitation in InGaAs/AlAsSb coupled double quantum wells is utilized. A bi-directional pump configuration, i.e., two control pulses are injected from both sides of a waveguide chip simultaneously, increases a nonlinear phase shift twice in comparison with injection of single pump beam with forward- and backward direction. The bi-directional pump configuration is the effective way to avoid damaging waveguide facets in the case where high optical power of control pulse is necessary to be injected for optical gating at repetition rate of 40/80 GHz. Bit error rate (BER) measurements on 40-Gb/s demultiplexed signal show that the power penalty is decreased slightly for the bi-directional pump case in the BER range less than 10-6. The power penalty is 1.3 dB at BER of 10 - 9 for the bi-directional pump case, while it increases by 0.3-0.6 dB for single pump cases. A power penalty is influenced mainly by signal attenuation at "off" state due to the insufficient nonlinear phase shift, upper limit of which is constrained by the current low XPM efficiency of 0.1 rad/pJ and the damage threshold power of 100 mW in a waveguide facet.

We present a 10-bit 1-MS/s successive approximation analog-to-digital converter core including a charge redistribution digital-to-analog converter and a comparator. A new linearity calibration technique enables use of a nearly minimum capacitor limited by kT/C noise. The ADC core without digital control blocks has been fabricated in a 0.18-µm CMOS process and consumes 118 µW at 1.8 V power supply. Also, the active area of ADC core is realized to be 0.027 mm2. The calibration improves the SNDR by 13.4 dB and the SFDR by 21.0 dB. The measured SNDR and SFDR at 1 kHz input are 55.2 dB and 73.2 dB respectively.

One method for achieving high-speed waveform digitizing uses time-interleaved A-D Converters (ADCs). It is known that, in this method, using multiple ADCs enables sampling at a rate higher than the sampling rate of the ADC being used. Degradation of the dynamic range, however, results from such factors as phase error in the sampling clock applied to the ADC, and mismatched frequency characteristics among the individual ADCs. This paper describes a method for correcting these mismatches using a digital signal processing (DSP) technique for automatic test equipment applications. This method can be applied to any number of interleaved ADCs, and it does not require any additional hardware; good correction and improved accuracy can be obtained simply by adding a little to the computing overhead.

A novel automatic quality factor (Q) tuning scheme for an low-power and wideband active-RC filter is presented. Although Q-tuning is effective to reduce the power consumption of wideband active-RC filters, there are several problems since the Q-tuning normally relies on a magnitude locked loop (MLL). MLL is not accurate due to the amplitude detection circuits, and occupied area and power consumption tends to be large due to its complexity. In addition, flexibility to the reference signal may be the problem, since the reference signal which has a fixed accurate frequency is required. In order to solve these problems, we propose a Q-tuning scheme, which does not require a MLL. Therefore, proposed Q-tuning scheme has good accuracy, small die area, low power consumption and flexibility to the reference signal. In our proposed scheme, Q is tuned by adjusting the phase of an integrator to 90 degrees. The phase of an integrator is adjusted by detecting and controlling the oscillation frequency of a two-stage ring-integrator to the cutoff frequency of a filter, since the phase shift of an integrator is exactly 90 degrees at the oscillation frequency. The frequency is easily detected and controlled by counters and variable resistors, respectively. The Q-tuning circuit with a 5th-order Chebyshev LPF is implemented in a 0.13 µm CMOS technology. The tuning circuit occupies 0.12 mm2 and consumes 2.6 mW from 1.2 V supply.

The medical care day by day and more and more is associated with and reliant upon concepts and advances of electronics and electromagnetics. Numerous medical devices are implanted in the body for medical use. Tissue implanted devices are of great interest for wireless medical applications due to the promising of different clinical usage to promote a patient independence. It can be used in hospitals, health care facilities and home to transmit patient measurement data, such as pulse and respiration rates to a nearby receiver, permitting greater patient mobility and increased comfort. As this service permits remote monitoring of several patients simultaneously it could also potentially decrease health care costs. Advancement in radio frequency communications and miniaturization of bioelectronics are supporting medical implant applications. A central component of wireless implanted device is an antenna and there are several issues to consider when designing an in-body antenna, including power consumption, size, frequency, biocompatibility and the unique RF transmission challenges posed by the human body. The radiation characteristics of such devices are important in terms of both safety and performance. The implanted antenna and human body as a medium for wireless communication are discussed over Medical Implant Communications Service (MICS) band in the frequency range of 402-405 MHz.

Multi-carrier code division multiple access (MC-CDMA) is a promising wireless access technique for the next generation mobile communications systems, in which broadband packet data services will dominate. Hybrid automatic repeat request (HARQ) is an indispensable error control technique for high quality packet data transmission. The HARQ throughput performance of multi-code MC-CDMA degrades due to the presence of residual inter-code interference (ICI) after frequency-domain equalization (FDE). To reduce the residual ICI and improve the throughput performance, a frequency-domain soft interference cancellation (FDSIC) technique can be applied. An important issue is the generation of accurate residual ICI replica for FDSIC. In this paper, low-density parity-check coded (LDPC-coded) MC-CDMA HARQ is considered. We generate the residual ICI replica from a-posteriori log-likelihood ratio (LLR) of LDPC decoder output and evaluate, by computer simulation, the throughput performance in a frequency-selective Rayleigh fading channel. We show that if the residual ICI is removed, MC-CDMA can provide a throughput performance superior to orthogonal frequency division multiplexing (OFDM).

We identify a broadband equivalent circuit of an on-chip self-complementary antenna integrated with a µm-sized semiconductor mesa structure whose circuit elements can be interpreted by using closed-form analysis. Prior to the equivalent circuit analysis, an electromagnetic simulation is done to investigate frequency independency of the input impedance for the integrated self-complementary antenna in terahertz range.

In equational theorem proving, convergent term rewriting systems play a crucial role. In order to compute convergent term rewriting systems, the standard completion procedure (KB) was proposed by Knuth and Bendix and has been improved in various ways. The multi-completion system MKB developed by Kurihara and Kondo accepts as input a set of reduction orders in addition to equations and efficiently simulates parallel processes each of which executes the KB procedure with one of the given orderings. Wehrman and Stump also developed a new variant of completion procedure, constraint-based completion, in which reduction orders need not be given by using automated modern termination checkers. As a result, the constraint-based procedures simulate the execution of parallel KB processes in a sequential way, but naive search algorithms sometimes cause serious inefficiency when the number of the potential reduction orders is large. In this paper, we present a new procedure, called a constraint-based multi-completion procedure MKBcs, by augmenting the constraint-based completion with the framework of the multi-completion for suppressing the combinatorial explosion by sharing inferences among the processes. The existing constraint-based system SLOTHROP, which basically employs the best-first search, is more efficient when its built-in heuristics for process selection are appropriate, but when they are not, our system is more efficient. Therefore, both systems have their role to play.

In this paper, the impacts of using multiple transmit antennas under doubly correlated MIMO channels on CDMA uplink code acquisition is studied. The performance of a MIMO code acquisition system is analyzed by considering spatial fading correlations, which depend on antenna spacing and azimuth spread at both MS and BS. The detection performance and mean acquisition time in the presence of spatially correlated MIMO channel are presented on a frequency selective fading channel and compared with the cases of spatial fading decorrelation via numerical evaluation. It is observed that the acquisition performance relies on the degree of spatial fading correlations. In addition, it is surprisingly seen that a MIMO code acquisition system provides worse performance than SIMO.

We present a novel frequency partitioning technique of fractional frequency reuse (FFR) that reduces the effect of co-channel interference and increases the capacity of OFDM systems. The usable sub-channel sets are classified into the common sub-channel sets for all cells and the dedicated sub-channel sets for specific cell types in FFR. The proposed fractional frequency reuse with ordering scheme (FFRO) can decrease the amount of interference in the common sub-channel sets by specially designing the sub-channel sets and the order of sub-channel assignment for specific cell types. Simulation results show that the proposed FFRO yields enhanced performance for both uniform and non-uniform distributions of traffic load.

A graph is an interval graph if and only if each vertex in the graph can be associated with an interval on the real line such that any two vertices are adjacent in the graph exactly when the corresponding intervals have a nonempty intersection. A number of interesting applications for interval graphs have been found in the literature. In order to find structural features common to structural data which can be represented by intervals, this paper proposes new interval graph structured patterns, called linear interval graph patterns, and a polynomial time algorithm for finding a minimally generalized linear interval graph pattern explaining a given finite set of interval graphs.

Let T be a node-weighted tree with n nodes, and let π(u,v) denote the path between two nodes u and v in T. We address two problems: (i) Path Maximum Query: Preprocess T so that, for a query pair of nodes u and v, the maximum weight on π(u,v) can be found quickly. (ii) Path Maximum Sum Query: Preprocess T so that, for a query pair of nodes u and v, the maximum weight sum subpath of π(u,v) can be found quickly. For the problems we present solutions with O(1) query time and O(n log n) preprocessing time.

Role-based access control (RBAC) is widely used as an access control mechanism in various computer systems. Since an organization's lines of authority influence the authorized privileges of jobs, roles also form a hierarchical structure. A role graph is a model that represents role hierarchies and is suitable for the runtime phase of RBAC deployment. Since a role graph cannot take various forms for given roles and cannot handle abstraction of roles well, however, it is not suitable for the design phase of RBAC deployment. Hence, an extended role graph, which can take a more flexible form than that of a role graph, is proposed. The extended role graph improves diversity and clarifies abstraction of roles, making it suitable for the design phase. An equivalent transformation algorithm (ETA), for transforming an extended role graph into an equivalent role graph, is also proposed. Using the ETA, system administrators can deploy efficiently RBAC by using an extended role graph in the design phase and a standard role graph in the runtime phase.

Based on the cyclotomy classes of extension fields, a family of binary cyclotomic sequences are constructed and their pseudorandom measures (i.e., the well-distribution measure and the correlation measure of order k) are estimated using certain exponential sums. A lower bound on the linear complexity profile is also presented in terms of the correlation measure.

We study the high-frequency asymptotic analysis methods for the scattered fields by a cylindrically curved conducting surface excited by the incident wave on the curved surface from the convex side. We first derive the novel hybrid ray-mode solution for the scattered fields near the concave surface by solving a canonical problem formulated under the assumption that the cylindrically curved conducting surface possesses only one edge. Then by applying the ray tracing technique and the idea of Keller's GTD (Geometrical Theory of Diffraction), the solutions derived for the canonical problem are extended to account for the problem of the radiation from and the scattering by the other edge of the cylindrically curved surface. We confirm the validity of the novel asymptotic representations proposed in the present study by comparing both with the numerical results obtained from the method of moment and the experimental results performed in the anechoic chamber.

This letter proposes a computationally efficient way of jointly estimating the residual frequency offset (RFO) and sampling frequency offset (SFO) by using a continual pilot (CP) defined in OFDM-based DVB-T system. In order to devise an unbiased joint frequency estimator in the current DVB-T system, a CP subset is selected to offset the effects of RFO and SFO simultaneously.

This paper deals with a new formulation for the diffraction of a plane wave by a periodic grating. As a simple example, the diffraction of a transverse magnetic wave by a perfectly conductive periodic array of rectangular grooves is discussed. On the basis of a shadow hypothesis such that no diffraction takes place and only the reflection occurs with the reflection coefficient -1 at a low grazing limit of incident angle, this paper proposes the scattering factor as a new concept. In terms of the scattering factor, several new formulas on the diffraction amplitude, the diffraction efficiency and the optical theorem are obtained. It is newly found that the scattering factor is an even function due to the reciprocity. The diffraction efficiency is defined for a propagating incident wave as well as an evanescent incident wave. Then, it is theoretically found that the 0th order diffraction efficiency becomes unity and any other order diffraction efficiencies vanish when a real angle of incidence becomes low grazing. Numerical examples of the scattering factor and diffraction efficiency are illustrated in figures.