A novel fast algorithm for shape matching using statistical features of shape contexts is presented. By pruning the candidate shapes using the moment-based statistical features of shape contexts, the required number of matching processes is dramatically reduced with negligible performance degradation. Experimental results demonstrate that the proposed algorithm reduces the pruning time up to 1/(r·n) compared with the conventional RSC algorithm while maintaining a similar or better performance, where n is the number of sampled points of a shape and r is the number of randomly selected representative shape contexts for the query shape.

Handoff is a critical issue for stations in IEEE 802.11-based wireless networks. In order to provide Voice-over IP (VoIP) and real-time streaming applications to stations, a handoff mechanism is needed that can reduce latency and provide seamless communication. However, the IEEE802.11 handoff scheme is not appropriate to supply their quality of service (QoS), because it is based on a full-scanning approach. Full-scanning spends too much time searching for access points (APs). Therefore, various pre-scan handoff protocols such as SyncScan and DeuceScan have been proposed. They scan to find nearby APs before the station loses contact with its current AP, but the pre-scanning overhead is considerable. Our handoff mechanism reduces the delay and overhead associated with the link layer handoff by periodically scanning the channel groups.

In network coding, for the case that the network topology is unknown completely, random linear network coding has been proposed as an acceptable coding technique. In this paper, we define average failure probability of random linear network coding in order to characterize the performance of random network coding, and then analyze this failure probability for different known topological information of network. We obtain several upper bounds on the failure probabilities, and further show that, for some networks, these upper bounds are tight or asymptotically tight. Moreover, if the more topological information of the network is utilized, the better upper bounds are acquired.

Some statistical characteristics, including the means and the cross-correlations, of frequency-selective Rician fading channels seen by orthogonal frequency division multiplexing (OFDM) subcarriers are derived in this paper. Based on a pairwise error probability analysis, the mean vector and the cross-correlation matrix are used to obtain an upper bound of the overall bit-error rate (BER) in a closed-form for coded OFDM signals with and without inter-carrier interference. In this paper, the overall BER is defined as the average BER of OFDM signals of all subcarriers obtained by considering their cross-correlations. Numerical examples are presented to compare the proposed upper bound of the overall BERs and the overall BERs obtained by simulations.

Generally, the failure rate of a sealed relay is regarded as a constant value, no matter where and how it is used. However, the failure processes of sealed relays won't be the same under different conditions, even for one relay, its failure rate also will be changed during operations. This paper studies the failure process of a kind of sealed relay by analyzing the variations of its time parameters. Among contact resistance and all those time parameters, it is found that closing gap time can indicate the failure process of tested relay very well. For the purpose of verifying this conclusion derived from time parameters, the contacts are observed by microscope after the tested relay failed. Both theoretical calculation result of contacts gap and photos taken by microscope show that the hypothetic failure mode derived from time parameters is reasonable. Based on the failure analysis, the paper also proposes a dynamic reliability estimation method with closing gap time.

When contact failure occurs in a connector in a coaxial high-frequency (HF) signal transmission line, it is well known that common-mode (CM) radiation occurs on the line. We focus on contact conditions in a connector causing such CM radiation. Experiments and simulations verify that CM radiation increases as the contact resistance increases. While the CM current strongly depends on the distribution pattern of contact resistances at a low resistance, the CM current does not depend on these pattern at a high resistance. Our results indicate that it is important to maintain a symmetrical distribution of contact spots whenever the number of such spots is four or more.

The brain-machine interface (BMI) is a new method for man-machine interface, which enables us to control machines and to communicate with others, without input devices but directly using brain signals. Previously, we successfully developed a real time control system for operating a robot arm using brain-machine interfaces based on the brain surface electrodes, with the purpose of restoring motor and communication functions in severely disabled people such as amyotrophic lateral sclerosis patients. A fully-implantable wireless system is indispensable for the clinical application of invasive BMI in order to reduce the risk of infection. This system includes many new technologies such as two 64-channel integrated analog amplifier chips, a Bluetooth wireless data transfer circuit, a wirelessly rechargeable battery, 3 dimensional tissue-fitting high density electrodes, a titanium head casing, and a fluorine polymer body casing. This paper describes key features of the first prototype of the BMI system for clinical application.

This paper presents a new unequal error protection (UEP) image transmission system that incorporates a Lifting Wavelet Transform (LWT) and Reed Solomon (RS) coded cooperation scheme to increase image transmission diversity, as well as save transmission bandwidth. Having a partner to assist direct communication increases the resilience of low frequency subband data against an error-prone fading channel. Low frequency subbands are partitioned into two sets of data and transmitted using the RS coded cooperation scheme. High frequency subbands data are transmitted directly to a base station. Results show that the new UEP image transmission system using LWT based RS coded cooperation scheme achieves diversity gains of around 10 dB, with channel SNR from 10 to 20 dB, compared with the image transmission system with non-cooperative system under slow Rayleigh fading channel for all levels of LWT decomposition. In addition, the new UEP image transmission system using LWT based RS coded cooperation scheme with one level of wavelet decomposition offers around 37.5% bandwidth gain (β), compared with the system without LWT, which incurs a reduction of 3 dB in reconstructed image quality.

Recently, for electronic devices operating at high frequencies, the suppression of a high-frequency electromagnetic field of 1 GHz or more has become necessary. We focus on a loose connector between a pair of electrical devices operating in the high-frequency band. Many electronic devices are used in living spaces, most of which are connected to one another. When a user connects two devices, achieving good contact only by finger tightening can be difficult. Accordingly, in this paper, considering the case where the tightening torque of a coaxial connector is insufficient, we analyze the effect of loose contact on electromagnetic field radiation from a transmission line.

In this letter, a study on the end-to-end outage performance of dual-hop non-regenerative relaying in the presence of co-channel interference is presented. We assume that both the desired and the interfering signals are subjected to Nakagami-m fading. Exact analytical expressions, as well as tight lower bounds of the end-to-end outage probability, are derived. An asymptotic expression for the outage probability at high values of Signal-to-Interference Ratio is also presented. Furthermore, we also propose the optimal power allocation for high values of Signal-to-Interference Ratio. Extensive numerically evaluation and computer simulation results are presented to verify the validity and the accuracy of the proposed analysis.

In this letter, we derive another exact bit error rate (BER) for decode-and-forward (DF) relay systems over Rayleigh fading channels. At first, our focus is on fixed-DF (FDF) relay schemes in which the probability density function (PDF) is derived based on error-events at relay nodes. Some insight into how erroneous detection and transmission at relay nodes affect both the combined signal-to-noise ratio (SNR) and the averaged BER is obtained, and cooperative diversity is observed from the closed-form BER expression. In addition, the developed analytical method is extended to adaptive-DF (ADF) schemes and the exact BER expressions are derived. Simulation results are finally presented to validate the analysis.

This paper presents the development of a sound–specific vibration interface and its evaluation results by playing three commercial games with the interface. The proposed interface complements the pitfalls of existing frequency–based vibration interfaces such as vibrating headsets, mouses, and joysticks. Those interfaces may bring negative user experiences by generating incessant vibrations because they vibrate in response to certain sound frequencies. But the proposed interface which responds to only target sounds can improve user experiences effectively. The hardware and software parts of the interface are described; the structure and the implementation of a wrist pad that delivers vibration are discussed. Furthermore, we explain a sound-matching algorithm that extracts sound characteristics and a GUI-based pattern editor that helps users to design vibration patterns. The results from evaluating the performance show that the success ratio of the sound matching is over 90% at the volume of 20 dB and the delay time is around 400 msec. In the survey about user experiences, the users evaluates that the interface is more than four times effective in improving the reality of game playing than without using the vibration interfaces, and two times than the frequency–based ones.

Different encoding modes for variable block size are available in the H.264/AVC standard in order to offer better coding quality. However, this also introduces huge computation time due to the exhaustive check for all modes. In this paper, a fast spatial DIRECT mode decision method for profiles supporting B frame encoding (main profile, high profile, etc.) in H.264/AVC is proposed. Statistical analysis on multiple video sequences is carried out, and the strong relationship of mode selection and rate-distortion (RD) cost between the current DIRECT macroblock (MB) and the co-located MBs is observed. With the check of mode condition, predicted RD cost threshold and dynamic parameter update model, the complex mode decision process can be terminated at an early stage even for small QP cases. Simulation results demonstrate the proposed method can achieve much better performance than the original exhaustive rate-distortion optimization (RDO) based mode decision algorithm by reducing up to 56.8% of encoding time for IBPBP picture group and up to 67.8% of encoding time for IBBPBBP picture group while incurring only negligible bit increment and quality degradation.

This paper is about a new efficient method for the implementation of convolvers and correlators using the Fermat Number Transform (FNT) and the inverse (IFNT). The latter present advantages compared to Inverse Fast Fourier Transform (IFFT). An efficient state space method for implementing the Inverse FNT (IFNT) over rectangular windows is proposed for the cases where there is a large overlap between the consecutive input signals. This is called Inverse Generalized Sliding Fermat Number Transform (IGSFNT) and is useful for reducing the computational complexity of finite ring convolvers and correlators. This algorithm uses the technique of Generalized Sliding associated to matricial calculation in the Galois Field. The computational complexity of this method is compared with that of standard IFNT.

In this paper, a new power control scheme is proposed to maximize the network throughput with fairness provisioning. Based on the Stackelberg game model, the proposed scheme consists of two control mechanisms; user-level and system-level mechanisms. Control decisions in each mechanism act cooperatively and collaborate with each other to satisfy efficiency and fairness requirements. Simulation results demonstrate that the proposed scheme has excellent network performance, while other schemes cannot offer such an attractive performance balance.

In this letter, we investigate the Nth-best user selection scheme for amplify-and-forward cooperative systems over Rayleigh fading channels. We deduce the probability density function, the cumulative density function, and the moment generating function of the end-to-end signal-to-noise ratio of the system. Then, the respective closed-form expressions of the average symbol error probability and the outage probability at the destination are derived. The diversity order obtained in the scheme increases with user number but becomes less as the selection sequence number N increases. Simulation results verify the analytical results.

This paper presents a grid-based, real-time surface modeling algorithm in which the generation of a precise 3D model is possible by considering the user's intention during the course of the spatial input. In order to create the corresponding model according to the user's input data, plausible candidates of wand traversal patterns of grid edges are defined by considering the sequential and directional characteristics of the wand input. The continuity of the connected polygonal surfaces, including the octree space partitioning, is guaranteed without the extra crack-patching algorithm and the pre-defined patterns. Furthermore, the proposed system was shown to be a suitable and effective surface generation tool for the spatial sketching system. It is not possible to implement the unusual input intention of the 3D spatial sketching system using the conventional Marching Cubes algorithm.

Sender-based message logging (SBML) with checkpointing has its well-known beneficial feature, lowering highly failure-free overhead of synchronous logging with volatile logging at sender's memory. This feature encourages it to be applied into many distributed systems as a low-cost transparent rollback recovery technique. However, the original SBML recovery algorithm may no longer be progressing in some transient communication error cases. This paper proposes a consistent recovery algorithm to solve this problem by piggybacking small log information for unstable messages received on each acknowledgement message for returning the receive sequence number assigned to a message by its receiver. Our algorithm also enables all messages scheduled to be sent, but delayed because of some preceding unstable messages to be actually transmitted out much earlier than the existing ones.

This paper presents the initial results of a study of an asymptotic method for calculating the received intensity of multi-path millimeter waves transmitted over an undulating surface. First, an integral expression of the received intensity is derived using a physical optics approximation. Then its zero-th order asymptotic expression is derived, using the Pearcey integral, for the case where the phase function appearing in the integrand can be approximated by a quartic polynomial. A numerical examination made at 59.5 GHz showed that the asymptotic method is in good agreement with the physical optics method, even in cases where the geometrical optics method deviates significantly from the physical optics method, and that the range of applicability of the asymptotic method has its upper bound somewhere around a transmission distance to surface undulation wavelength ratio of 2.

This paper proposes a new resource allocation algorithm for uplink OFDMA-based cooperative relay networks, assuming multiple user nodes, multiple relay nodes and a single destination. The aim is to maximise the total sum of the users' data rates, while guaranteeing fairness among them with different QoS requirements. Assuming perfect channel state information (CSI) at the resource allocation controller, the optimisation problem is formulated such that each user is assigned a weight factor based on its QoS requirements. The ones with higher weights are given higher priorities to select their resources (relay stations and subcarriers) first. Once the required QoS is achieved for all users, the weight factor for all users is reduced to a small uniform value. The remaining resources are then allocated to the users with higher instantaneous rates in order of magnitude. The results show that the proposed algorithm outperforms the greedy and static algorithms in terms of outage probability and fairness, and at the same time outperforms Jeong's algorithm by 58% in terms of total sum rate, with an average 74% reduction in system complexity.