In this paper, we propose a new subcarrier allocation algorithm for a downlink OFDMA relay network with multicells. In the proposed algorithm, subcarriers are allocated to users and relays to maximize the overall sum of the achievable rate under fairness constraints. Simulation results show that the proposed algorithm achieves higher data rate than the static algorithm and reduces the outage probability compared to the static and greedy algorithms.

We consider the problem of fast identification of high-rate flows in backbone links with possibly millions of flows. Accurate identification of high-rate flows is important for active queue management, traffic measurement and network security such as detection of distributed denial of service attacks. It is difficult to directly identify high-rate flows in backbone links because tracking the possible millions of flows needs correspondingly large high speed memories. To reduce the measurement overhead, the deterministic 1-out-of-k sampling technique is adopted which is also implemented in Cisco routers (NetFlow). Ideally, a high-rate flow identification method should have short identification time, low memory cost and processing cost. Most importantly, it should be able to specify the identification accuracy. We develop two such methods. The first method is based on fixed sample size test (FSST) which is able to identify high-rate flows with user-specified identification accuracy. However, since FSST has to record every sampled flow during the measurement period, it is not memory efficient. Therefore the second novel method based on truncated sequential probability ratio test (TSPRT) is proposed. Through sequential sampling, TSPRT is able to remove the low-rate flows and identify the high-rate flows at the early stage which can reduce the memory cost and identification time respectively. According to the way to determine the parameters in TSPRT, two versions of TSPRT are proposed: TSPRT-M which is suitable when low memory cost is preferred and TSPRT-T which is suitable when short identification time is preferred. The experimental results show that TSPRT requires less memory and identification time in identifying high-rate flows while satisfying the accuracy requirement as compared to previously proposed methods.

In this letter, a highly linear 1.22 GHz current mirror based differential RF programmable gain amplifier (RFPGA) for digital TV tuner applications is proposed and implemented using 0.18-µm CMOS process. The fabricated RFPGA shows a maximum power gain of 9 dB, an OIP3 of 23.5 dBm, and an accurate dB-linear discrete gain step control while consuming 36 mA from a 1.8-V supply voltage.

Inductive theorem proving plays an important role in the field of formal verification of systems. The rewriting induction (RI) is a method for inductive theorem proving proposed by Reddy. In order to obtain successful proofs, it is very important to choose appropriate contexts (such as in which direction each equation should be oriented) when applying RI inference rules. If the choice is not appropriate, the procedure may diverge or the users have to come up with several lemmas to prove together with the main theorem. Therefore we have a good reason to consider parallel execution of several instances of the rewriting induction procedure, each in charge of a distinguished single context in search of a successful proof. In this paper, we propose a new procedure, called multi-context rewriting induction, which efficiently simulates parallel execution of rewriting induction procedures in a single process, based on the idea of the multi-completion procedure. By the experiments with a well-known problem set, we discuss the effectiveness of the proposed procedure when searching along various contexts for a successful inductive proof.

A generalized Gray map for codes over the ring Fq[u]/ is introduced, where q=pm is a prime power. It is shown that the generalized Gray image of a linear length-N (1-ut)-cyclic code over Fq[u]/ is a distance-invariant linear length-qtN quasi-cyclic code of index qt/p over Fq. It turns out that if (N,p)=1 then every linear code over Fq that is the generalized Gray image of a length-N cyclic code over Fq[u]/, is also equivalent to a linear length-qtN quasi-cyclic code of index qt/p over Fq. The relationship between linear length-pN cyclic codes with (N,p)=1 over Fp and linear length-N cyclic codes over Fp+uFp is explicitly determined.

This paper studies the feasibility of 700 MHz band inter-vehicle communication system when it is put into practical use in urban area. To verify the system, a large-scale demonstration experiment in a quasi-street test course is performed. In the experiment, a number of vehicles which are equipped with communication devices conforming to ITS FORUM RC-006 specifications are employed. A simulation method that is applicable to large-scale communication model is also designed, and the validity of the method is verified by utilizing the results derived from the experiment. Based on this model, the quality of the inter-vehicle communication system in urban area communication environment is estimated. The results show that the system's performance satisfies the requirements of representative prevention scenes of traffic accident, and the feasibility of the 700 MHz band inter-vehicle communication system specified in RC-006 is verified in the practical use in urban communication environment.

We present a technology based on Nb/NbxSi1-x/Nb junctions, with barriers near the metal-insulator transition, for applications in superconducting electronics (SCE) as an alternative to Nb/AlOx/Nb tunnel junctions. Josephson junctions with co-sputtered amorphous Nb-Si barriers can be made with a wide variety of electrical properties: critical current density (Jc), capacitance (C), and normal resistance (Rn) can be reliably selected within wide ranges by choosing both the barrier thickness and Nb concentration. Nonhysteretic Nb/NbxSi1-x/Nb junctions with IcRn products greater than 1 mV, where Ic is the critical current, and Jc values near 100 kA/cm2 have been fabricated and are promising for superconductive digital electronics. These barriers have thicknesses of several nanometers; this improves fabrication reproducibility and junction uniformity, both of which are necessary for complex digital circuits. Recent improvements to our deposition system have allowed us to obtain better uniformity across the wafer.

Nonlinear distortions in power amplifiers (PAs) generate spectral regrowth at the output, which causes interference to adjacent channels and errors in digitally modulated signals. This paper presents a novel method to evaluate adjacent channel leakage power ratio (ACPR) and error vector magnitude (EVM) from the amplitude-to-amplitude (AM/AM) and amplitude-to-phase (AM/PM) characteristics. The transmitted signal is considered to be complex Gaussian distributed in orthogonal frequency-division multiplexing (OFDM) systems. We use the Mehler formula to derive closed-form expressions of the PAs output power spectral density (PSD), ACPR and EVM for memoryless PA and memory PA respectively. We inspect the derived relationships using an OFDM signal in the IEEE 802.11a WLAN standard. Simulation results show that the proposed method is appropriate to predict the ACPR and EVM values of the nonlinear PA output in OFDM systems, when the AM/AM and AM/PM characteristics are known.

To achieve conductive and wear-durable carbon thin films by metal doping, we deposited Au-, Pt-, and Pd-doped carbon thin films by RF sputtering, and evaluated the dopant concentrations, resistivity, and scratch hardness. Among the doped films, the Pt-doped film with low Pt concentration was most suitable from a practical perspective.

Superconducting Quantum Interference Devices (SQUIDs) are known to be the most sensitive magnetometers, used in a wide range of applications like biomagnetism, geomagnetism, Non Destructive Evaluation (NDE), metrology or fundamental science. For all these applications, the SQUID sensor is used in analog mode and associated with a carefully designed room-temperature control and/or feedback electronics. Nevertheless, the use of SQUID sensors in digital mode is of high interest for several applications due to their quantum accuracy associated to high linearity, and their potentially very high slew rate and dynamic range. The concept and performances of a low-Tc digital magnetometer based on Single-Flux-Quantum (SFQ) logic, fabricated at the FLUXONICS Foundry located at IPHT Jena, Germany, are given after a presentation of the context of development of superconductive digital magnetometers. The sensitivity, limited to one magnetic single flux quantum, and a dynamic range of 76 dB, that corresponds to an upper limit of the magnetic field amplitude higher than 5 µT, have been measured along with overnight stability. The dynamic range of about 2800 magnetic flux quanta Φ0 has been experimentally observed with an external magnetic field. First signatures of magnetic fields have been observed simultaneously with the ones of analog SQUIDs in the low noise environment of the Laboratoire Souterrain a Bas Bruit (LSBB) located in Rustrel, Provence, France.

This letter presents an approach to the construction of multiple-rate quasi-cyclic (QC) low-density parity-check (LDPC) codes based on hyperplanes (µ-flats) of two different dimensions in Euclidean geometries. The codes constructed with this method have the same code length, multiple-rate and large stopping sets while maintaining the same basic hardware architecture. The code performance is investigated in terms of the bit error rate (BER) and compared with those of the LDPC codes which are proposed in IEEE 802.16e standard. Simulation results show that our codes perform very well and have low error floors over the AWGN channel.

Hierarchical Identity-Based Encryption (HIBE) is a generalization of identity-based encryption that mirrors an organizational hierarchy, and allows the root Private Key Generator (PKG) to distribute the workload of key generations to lower-level PKGs. In Indocrypt'08, Ren and Gu proposed a new HIBE scheme, and claimed that their scheme is fully chosen-ciphertext secure in the standard model. However, by giving a concrete attack, we show that Ren-Gu's HIBE is even not chosen-plaintext secure.

With the progress of ubiquitous technology, ubiquitous learning presents new opportunities to learners. Situations of a learner can be grasped through analyzing the learner's actions collected by sensors, RF-IDs, or cameras in order to provide support at proper time, proper place, and proper situation. Training for acquiring skills and enhancing physical abilities through exercise and experience in the real world is an important domain in u-learning. A training program may last for several days and has one or more training units (exercises) for a day. A learner's performance in a unit is considered as short term state. The performance in a series of units may change with patterns: progress, plateau, and decline. Long term state in a series of units is accumulatively computed based on short term states. In a learning/training program, it is necessary to apply different support strategies to adapt to different states of the learner. Adaptation in learning support is significant, because a learner loses his/her interests easily without adaptation. Systems with the adaptive support usually provide stimulators to a learner, and a learner can have a great motivation in learning at beginning. However, when the stimulators reach some levels, the learner may lose his/her motivation, because the long term state of the learner changes dynamically, which means a progress state may change to a plateau state or a decline state. In different long term learning states, different types of stimulators are needed. However, the stimulators and advice provided by the existing systems are monotonic without changeable support strategies. We propose a mutual adaptive support. The mutual adaptation means each of the system and the learner has their own states. On one hand, the system tries to change its state to adapt to the learner's state for providing adaptive support. On the other hand, the learner can change its performance following the advice given based on the state of the system. We create a ubiquitous pet (u-pet) as a metaphor of our system. A u-pet is always with the learner and encourage the leaner to start training at proper time and to do training smoothly. The u-pet can perform actions with the learner in training, change its own attributes based on the learner's attributes, and adjust its own learning rate by a learning function. The u-pet grasps the state of the learner and adopts different training support strategies to the learner's training based on the learner's short and long term states.

The establishment of inter-domain traffic engineered paths is a requisite to accomplishing an end-to-end bandwidth guarantee and end-to-end resource optimization. Though the inter-domain paths must be reliable, it is difficult to compute suitable backup inter-domain paths in advance when the traffic engineering information is not disclosed outside of each domain. This means that the inter-domain path computation must satisfy the severe requirement of path establishment delay, since all inter-domain paths traversing the links in failure need to be computed after the failure occurs. Though several inter-domain path computation schemes have been proposed, their relative characteristics remain unknown. First, this paper classifies the conventional inter-domain path computation schemes into two types, i.e. end-to-end and per-domain schemes, and compares their performances under various traffic loads. Based on results of the comparisons, this paper proposes an adaptive inter-domain path computation scheme that can satisfy the severe requirement of the path establishment delay. In this scheme, the domain sequence from the source node to the destination node is divided into multiple sub-domain sequences according to the traffic load in each domain. The end-to-end path computation scheme is applied to the sub-domain sequences under heavy traffic loads, while the per-domain path computation scheme is applied to those under normal traffic loads. The simulation results show that the proposed scheme can adaptively satisfy the requirement for the path establishment delay while it maintains the optimality of path computation, even if the traffic load applied to each domain changes.

We present a congestion control algorithm for the Internet and assess its stability. The algorithm has low operation complexity and exercises control over sources without keeping per-flow information. Given the lack of support for explicit-rate feedback in the Internet, we discuss an implementation where feedback is based on explicit binary indications. We assess the stability through a discrete-time model and present simulation results showing the efficacy of the algorithm. The obtained results indicate that when the algorithm is used to control sources that support explicit binary feedback, its stability is not affected and its performance is close to that obtained with sources that support explicit-rate feedback.

A fuel-supply system using movable fuel-supply vehicles (FSVs) is proposed and its performance is evaluated. Both FSVs and vehicles requesting fuel are equipped with networked sensors. The sensors in FSVs are location sensors, and those in vehicles requesting fuel are for determining the remaining amount of fuel and the location of the vehicle. The time from when a fuel request is generated until the request is satisfied is the most basic performance metric for this system. Explicit formulas for the probabilistic distribution of this request time are also derived. Numerical examples show that the number of movable FSVs can be smaller than that of fixed fuel stations by about 80% or more than two orders of magnitude. This result suggests that movable FSVs may reduce the cost of the fuel supply infrastructure for alternative-fuel vehicles such as fuel-cell vehicles.

With simultaneous multi-user transmissions, spatial division multiple access (SDMA) provides substantial throughput gain over the single user transmission. However, its implementation in WLANs with contention-based IEEE 802.11 MAC remains challenging. Problems such as coordinating and synchronizing the multiple users need to be solved in a distributed way. In this paper, we propose a distributed MAC protocol for WLANs with SDMA support. A dual-mode CTS responding mechanism is designed to accomplish the channel estimation and user synchronization required for SDMA. We analytically study the throughput performance of the proposed MAC, and dynamic parameter adjustment is designed to enhance the protocol efficiency. In addition, the proposed MAC protocol does not rely on specific physical layer realizations, and can work on legacy IEEE 802.11 equipment with slight software updates. Simulation results show that the proposed MAC outperforms IEEE 802.11 significantly, and that the dynamic parameter adjustment can effectively track the load variation in the network.

Quality requirements are scattered over a requirements specification, thus it is hard to measure and trace such quality requirements to validate the specification against stakeholders' needs. We proposed a technique called "spectrum analysis for quality requirements" which enabled analysts to sort a requirements specification to measure and track quality requirements in the specification. In the same way as a spectrum in optics, a quality spectrum of a specification shows a quantitative feature of the specification with respect to quality. Therefore, we can compare a specification of a system to another one with respect to quality. As a result, we can validate such a specification because we can check whether the specification has common quality features and know its specific features against specifications of existing similar systems. However, our first spectrum analysis for quality requirements required a lot of effort and knowledge of a problem domain and it was hard to reuse such knowledge to reduce the effort. We thus introduce domain knowledge called term-characteristic map (TCM) to reuse the knowledge for our quality spectrum analysis. Through several experiments, we evaluate our spectrum analysis, and main finding are as follows. First, we confirmed specifications of similar systems have similar quality spectra. Second, results of spectrum analysis using TCM are objective, i.e., different analysts can generate almost the same spectra when they analyze the same specification.

Finding a kernel mapping function for support vector machines (SVMs) is a key step towards construction of a high-performanced SVM-based classifier. While some recent methods exploited an evolutional approach to construct a suitable multifunction kernel, most of them searched randomly and diversely. In this paper, the concept of a family of identical-structured kernel trees is proposed to enable exploration of structure space using genetic programming whereas to pursue investigation of parameter space on a certain tree using evolution strategy. To control balance between structure and parameter search towards an optimal kernel, simulated annealing is introduced. By experiments on a number of benchmark datasets in the UCI and text classification collection, the proposed method is shown to be able to find a better optimal solution than other search methods, including grid search and gradient search.

Previous vehicle surveillance researches on distributed sensor network focused on overcoming power limitation and communication bandwidth constraints in sensor node. In spite of this constraints, vehicle surveillance sensor node must have signal compression, feature extraction, target localization, noise cancellation and collaborative signal processing with low computation and communication energy dissipation. In this paper, we introduce an algorithm for light-weight wireless sensor node signal processing based on lifting scheme wavelet analysis feature extraction in distributed sensor network.