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.

By applying Wigner distribution, which has high time resolution and high random noise reducing capability, to the acoustic bio–signals, the possibility of early diagnosis in both intracranial vascular deformation and prosthetic cardiac valve malfunction increased. Especially in latter case, 1st–order local moment of the distribution showed its effectiveness.

In this paper, we propose an acoustic model that is robust to multiple noise environments, as well as a method for adapting the acoustic model to an environment to improve the model. The model is called "the multi-mixture model," which is based on a mixture of different HMMs each of which is trained using speech under different noise conditions. Speech recognition experiments showed that the proposed model performs better than the conventional multi-condition model. The method for adaptation is based on the aspect model, which is a "mixture-of-mixture" model. To realize adaptation using extremely small amount of adaptation data (i.e., a few seconds), we train a small number of mixture models, which can be interpreted as models for "clusters" of noise environments. Then, the models are mixed using weights, which are determined according to the adaptation data. The experimental results showed that the adaptation based on the aspect model improved the word accuracy in a heavy noise environment and showed no performance deterioration for all noise conditions, while the conventional methods either did not improve the performance or showed both improvement and degradation of recognition performance according to noise conditions.

In this paper, we investigate the problems of the established congestion solution and then introduce a self-adjustable rate control that supports quality of service assurances over multi-hop wireless mesh networks. This scheme eliminates two phases of the established congestion solution and works on the MAC layer for congestion control. Each node performs rate control by itself so network congestion is eliminated after it independently collects its vector parameters and network status parameters for rate control. It decides its transmission rate based on a predication model which uses a rate function including a congestion risk level and a passing function. We prove that our scheme works efficiently without any negative effects between the network layer and the data link layer. Simulation results show that the proposed scheme is more effective and has better performance than the existing method.

We have manufactured a trial 'Digital Packet Video (PV) Link' system for super high-resolution display. 'Digital PV Link' is a new data transmission protocol where the host transfers video data with attributes for only a selected area such as a motion picture window. This protocol handles the video data with an ID, which can be used for handling between plural hosts and plural displays such as multi display. This ID also makes the display to handle plural windows in accordance with different parameter such as scaling factor, color-adjust, and so on. In this protocol, error handling is a key because the video data is transferred only when the host wants to change display data. So, we have examined transmission errors and capability for motion pictures by using this trial system. In this report, we will introduce the concept and the characteristics of 'Digital PV Link,' and the result of examination.

Quantum computations have so far proved to be more powerful than classical computations, but quantum computers still have not been put into practical use due to several technical issues. One of the most serious problems for realizing quantum computers is decoherence that occurs inevitably since our apparatus are surrounded with environment and open systems. In this paper, we give some surveys on a variety of effects of decoherence in quantum algorithms such as Grover's database search and quantum walks, and we show how quantum algorithms work under decoherence, how sensitive they are against decoherence, and how to implement a robust quantum circuit.

For the purpose of detecting the intracranial vascular deformations noninvasively, transducer for bruit sound emanated from diseased lesion and analyzing system were developed and applied clinically. Several aspects of the bruit signals were clarified and the possibility of early diagnosis was increased.

A wireless sensor network is a network of compact micro-sensors equipped with wireless communication capability. In a wireless sensor network, saving energy is a critical issue. Furthermore, a sensor node is expected to face many difficulties in signaling and computing. As a MAC scheme for a wireless sensor network, we thus propose an energy-aware version of pure ALOHA scheme, where rather than sacrificing the simplicity of pure ALOHA, we take a straightforward approach in saving energy by trading off throughput performance. First, we add a step of deciding between stop and continuation prior to each delivery attempt for a MAC PDU. Secondly, we find an optimal stopping rule for such a decision in consideration of the losses reflecting energy consumption as well as throughput degradation. In particular, we note that the results of delivery attempts are hardly predictable in the environment that sensor nodes contend for the error-prone wireless resource. Thus, presuming that only partial information about such results is available to sensor nodes, we explicitly draw an optimal stopping rule. Finally, numerical examples are given to demonstrate the expected losses incurred by optimal stopping rules with full and partial information.

This paper presents an Application Specific Instruction-set Processor (ASIP) for the SHA-3 BLAKE algorithm family by instruction set extensions (ISE) from an RISC (reduced instruction set computer) processor. With a design space exploration for this ASIP to increase the performance and reduce the area cost, we accomplish an efficient hardware and software implementation of BLAKE algorithm. The special instructions and their well-matched hardware function unit improve the calculation of the key section of the algorithm, namely G-functions. Also, relaxing the time constraint of the special function unit can decrease its hardware cost, while keeping the high data throughput of the processor. Evaluation results reveal the ASIP achieves 335 Mbps and 176 Mbps for BLAKE-256 and BLAKE-512. The extra area cost is only 8.06k equivalent gates. The proposed ASIP outperforms several software approaches on various platforms in cycle per byte. In fact, both high throughput and low hardware cost achieved by this programmable processor are comparable to that of ASIC implementations.

Intracranial blood flow noise measuring and analyzing system were developed to detect the cerebrovascular diseases such as aneurysm, stenosis and occlusion in their early stage. To realize the effective measuring of the sound known as the 'bruit,' dedicated PVDF-film based sensor working on the closed eyelid was designed. FFT spectrums and Wigner distributions were used as analyzing methods to clarify both the precise spectrum and the time variance of the signals. Thirty normal people without any history of cerebrovascular disease were tested with the system to estimate the characteristics of the background noise. Thirteen patients, including eight stenosis, four aneurysm and one occlusion, were studied with the system. FFT spectral differences between patient and normal existed over the frequency range from 0.5kHz to 1.2kHz. In this range apparent increases of the signal components' power were observed for the patients. Numerically, this tendency was confirmed by the power difference between 750Hz and 1.5kHz, which could be the possible index of the existence diagnosis for cerebrovascular diseases. The shape of the FFT spectral pattern showed some difference between stenosis and aneurysm. In stenosis cases, it seemed that there existed the flat level from 0.4kHz to 1.2kHz, while in aneurysm cases the power decreases smoothly as frequency increases from the peak around 0.7kHz. Time variance of the bruit according to the cardiac cycle could be seen in the cases of stenosis from 30% to 50%, but not in the cases from 40% to 90%. This fact suggested the possibility to diagnose the extent of the stenosis. In most cases, recognizable spectral peak around 0.7 kHz were observed. Although the physical meanings of those peaks were not so clear, still it was the apparent characteristics and might be including important information.

This paper proposes a new hybrid scheme based on a given set of channels for preventing channel interference and collision in mobile networks. The proposed scheme is designed for improving system performance, focusing on enhancement of performance related to path breakage and channel interference. The objective of this scheme is to improve the performance of inter-node communication. Simulation results from this paper show that the new hybrid scheme can reduce a more control message overhead than a conventional random scheme.

Many cloud service providers employ specialized hardware accelerators, called neural processing units (NPUs), to accelerate deep neural networks (DNNs). An NPU scheduler is responsible for scheduling incoming user requests and required to satisfy the two, often conflicting, optimization goals: maximizing system throughput and satisfying quality-of-service (QoS) constraints (e.g., deadlines) of individual requests. We propose Layerweaver+, a low-cost layer-wise DNN scheduler for NPUs, which provides both high system throughput and minimal QoS violations. For a serving scenario based on the industry-standard MLPerf inference benchmark, Layerweaver+ significantly improves the system throughput by up to 266.7% over the baseline scheduler serving one DNN at a time.

In this paper, we propose a new channel allocation scheme, which is designed to efficiently carry out handoffs in wireless networks. Our scheme is based on conventional handoff methods, which include the channel reservation, carrying and sub-rating methods to assign channels for handoffs. First, we reserve a number of channels only for handoffs. Second, if there is no available channel in the next cell during handoff, the mobile station is allowed to carry a movable channel into the next cell. Finally, in order to avoid co-channel interference due to channel mobility, we adopt the sub-rating method for its carried channel. We evaluated our scheme using both Markov analysis and computer simulation. The analytical and simulation results indicate that our scheme may offer better performance than conventional handoff schemes in terms of handoff blocking probability and channel utilization.

This paper deals with graph colouring games, an example of pseudo-telepathy, in which two players can convince a verifier that a graph G is c-colourable where c is less than the chromatic number of the graph. They win the game if they convince the verifier. It is known that the players cannot win if they share only classical information, but they can win in some cases by sharing entanglement. The smallest known graph where the players win in the quantum setting, but not in the classical setting, was found by Galliard, Tapp and Wolf and has 32,768 vertices. It is a connected component of the Hadamard graph GN with N=c=16. Their protocol applies only to Hadamard graphs where N is a power of 2. We propose a protocol that applies to all Hadamard graphs. Combined with a result of Frankl, this shows that the players can win on any induced subgraph of G12 having 1609 vertices, with c=12. Moreover combined with a result of Godsil and Newman, our result shows that all Hadamard graphs GN (N ≥ 12) and c=N yield pseudo-telepathy games.

In provisioning packet data service on wireless cellular networks, a scheme of altering connection status between mobile and base stations appeared intending to efficiently utilize resource during idle periods. In such a scheme, connection components are sequentially released as an idle period persists, while the transmitting station converts to an transmission activity mode as the station is loaded with packets. However, actual resume of transmission activity is postponed by connection retrieval time to restore lost connection components. In general, an idle period affects the following connection retrieval time, which in turn produces an impact on the forthcoming idle period. Such chain reaction also makes a significant influence on overall packet delay performance. In this paper, as a way of improving packet delay performance, we propose two schemes identified as conservative extension and load threshold schemes. In the conservative extension scheme, we intentionally extend connection retrieval times so that each connection retrieval time is guaranteed not to be lower than a certain value. On the other hand, according to the load threshold scheme, a retrieval of lost connection components is postponed until packets are accumulated at the transmitting station up to a prescribed threshold. An increase in the value and threshold incurs an additional stand-by before resuming transmission activity in both proposed schemes. In turn, such intentional stand-by may contribute to regulating the length of idle period and connection retrieval time, and subsequently improving packet delay performance. To inspect the impact of conservative extension and load threshold schemes on packet delay performance, we first investigate the properties of idle periods. Secondly, for Poisson packet arrivals, we present an analytical method to exactly calculate the moments of packet delay time (at steady state) in each scheme. From numerical examples, we confirm the existence of non-trivial optimal value and threshold minimizing average packet delay or packet delay variation and conclude that conservative extension and load threshold schemes are able to enhance packet delay performance in various environments.

Mechanical prosthetic cardiac valves generate not only the widely recognized audible closing clicks but also ultrasonic closing clicks, as previously reported by us. A personal-computer-based measurement and analysis system with the bandwidth of 625 kHz has been developed to clarify the characteristics of these ultrasonic closing clicks. Fifty cases in total were assessed clinically, including cases with tilting disk valves, bileaflet valves, and flat disk valves. The ultrasonic closing clicks are damped vibrations continuing for about two milliseconds, and their frequency range was confirmed to be from 8 kHz to 625 kHz, while that of the audible click was up to 8 kHz. Although the sensitivity of the sensor decreased by approximately 30 dB at 625 kHz, effective power of the ultrasonic closing click was confirmed at this frequency. Moreover, it was shown that, surprisingly, the signal power at 625 kHz was still at the same level as that at around 100 kHz. Those wide bandwidth signal components exist independent of the type of mechanical valve, but the spectral pattern shows some dependence on the valve type.

A new in vitro experimental tool was developed to study the mechanism of the ultrasonic closing clicks' genesis of mechanical heart valves. Since the newly developed tester adopted compressed air flow directly instead of the blood analog fluid to drive the mechanical heart valve, it is not possibe to generate any cavitation. Closing clicks were measured with a small accelerometer at the surface of the valve holder made of silicone rubber. Ultrasonic closing clicks as well as audible closing clicks, similar to those measured clinically, could be observed using this setup. Thus, it was confirmed that the ultrasonic closing clicks can be generated without the existence of cavitation. Simultaneous measurements of the valve motion were made with a high-speed video camera, and the analysis of the video frames and clicks showed that higher frequency signal components of more than 50 kHz could be generated only at the instant of the closure, which means the collision of the occluder with the housing. Eighteen miniature accelerometers with an area of one square millimeter were developed and stuck on the housing to monitor the distribution of the housing vibrations in detail, and it was found that the vibrations correspond to the ultrasonic closing clicks propagated from the valve stop: the collision point of the occluder with the housing. This fact indicated that the generation of ultrasonic closing clicks are limited to the small area of the collision. From those results, it was concluded that the major origin of the ultrasonic closing clicks' genesis should be the collision of the occluder with the housing.

We propose an improved reference speaker weighting (RSW) and speaker cluster weighting (SCW) approach that uses an aspect model. The concept of the approach is that the adapted model is a linear combination of a few latent reference models obtained from a set of reference speakers. The aspect model has specific latent-space characteristics that differ from orthogonal basis vectors of eigenvoice. The aspect model is a "mixture-of-mixture" model. We first calculate a small number of latent reference models as mixtures of distributions of the reference speaker's models, and then the latent reference models are mixed to obtain the adapted distribution. The mixture weights are calculated based on the expectation maximization (EM) algorithm. We use the obtained mixture weights for interpolating mean parameters of the distributions. Both training and adaptation are performed based on likelihood maximization with respect to the training and adaptation data, respectively. We conduct a continuous speech recognition experiment using a Korean database (KAIST-TRADE). The results are compared to those of a conventional MAP, MLLR, RSW, eigenvoice and SCW. Absolute word accuracy improvement of 2.06 point was achieved using the proposed method, even though we use only 0.3 s of adaptation data.

In this paper, we proposed two models, the full multiple MCS (Multicast Server) model and the hybrid multiple MCS model to support multiple MCS over a single large cluster in ATM (Asynchronous Transfer Mode) networks. Also, we presented two methods for MCS assignment which are known as 2PSPMT (2 Phase Shortest Path based on Multicast tree) and hybrid-2PSPMT, and evaluated its performance by simulation. When an ATM host requests joining a specific multicast group, the MARS (Multicast Address Resolution Server) designates a proper MCS among the multiple MCSs for the group member to minimize the average path delay between the sender and the group members. Each method for MCS assignment construct a 2-phase partial multicast tree based on the shortest path algorithm. We reduced the average path delay in the multicast tree using these methods with various cluster topologies and MCS distribution scenarios in addition to distributing the load among multiple MCSs.

Power consumption is one of the most important factors in successfully designing of wireless sensor networks since it directly affects network lifetime. We propose a topology control scheme that reduces power consumption by minimizing, as much as possible, the number of active nodes, in a highly dense region as well as to decrease packet transmission delay. Simulation results show that our scheme can effectively solve the energy inefficiency problem caused by unbalanced power consumption, and can significantly reduce packet transmission delay.