This paper proposes a session state migration architecture for flexible server consolidation. One of technical challenges is how to split a session state from a connection and bind the session state to another connection in any servers. A conventional server and client application assumes that a session state is statically bound to a connection once the connection has been established. The proposed architecture reduces the migration latency, compared to an existing study by splitting the session state from the connection. This paper classifies common procedures of session state migration for various services. The session state migration architecture enables service providers to conduct server maintenance at their own convenience, and to conserve energy consumption at servers by consolidating them. A simulation to evaluate server consolidation reveals that the session state migration reduces the number of servers for accommdating users, compared to virtual machine migration. This paper also shows implementation of the session state migration architecture. Experimental results reveal that the impact caused by the proposed architecture on real-time applications is small.

Multi-view video consists of multiple video sequences which are captured by multiple closely spaced cameras from different angles and positions. It enables each user to freely switch viewpoints by playing different video sequences. However, the transmission of multi-view video requires more bandwidth than conventional multimedia. To reduce the bandwidth, UDMVT (User Dependent Multi-view Video Transmission) based on MVC (Multi-view Video Coding) for a single user has been proposed. In UDMVT, the same frames are encoded into different versions for different users, which increases the redundant transmission. To overcome this problem and extend UDMVT to multiple users' environment, this paper proposes UMSM (User dependent Multi-view video Streaming for Multi-users). UMSM calculates the overlapping and un-overlapping frame area for multiple users from all frames based on feedback information at a server. Proposed UMSM exploits the combination of multicasting overlapping area to multiple users and unicasting un-overlapping area to each user. By means of this concept, UMSM only transmits required frames for each user. To achieve further reduction of the traffic, UMSM combines other two features with this concept. The first one is that offset of the requests from multiple users is aligned periodically to maximize the overlapping frame area. The second one is that the SP-frames standardized in H.264/AVC are exploited as the anchor frame of overlapping frame area to prevent redundant transmissions of overlapping frames. The combination of these three techniques achieves substantial reduction of the transmission bitrate for multiple users in multi-view video streaming. Simulation results using benchmark test sequences provided by MERL show that UMSM decreases the transmission bit-rate 47.2% on average for 4 users are watching the same multi-view video compared to UDMVT.

The paper proposes the PMD method to design an introductory programming practice course plan that is inclusive for all learners and stable throughout a course. To achieve the course plan, the method utilizes personas, each of which represents learners having similar motivation to study programming. The learning of the personas is directed to the course goal with an enforcement resulting from the discipline, which is an integration of effective learning strategies with affective components of the persoans. Under the enforcement, services to facilitate and promote the learning of each persona can be decided, based on motivation components of each persona, motivational effects of the services, and the cycle of self-efficacy. The application of the method on about 500 freshmen in C programming practice course has shown this is a successful approach for designing courses.

In the sensor networks for surveillance, the requirements of providing energy efficiency and service differentiation, which is to deliver high-priority packets preferentially, while maintaining high goodput, which is to deliver many packets within their deadline are increasing. However, previous works have difficulties in satisfying the requirements simultaneously. Thus, we propose GES-MAC, which satisfies the requirements simultaneously. GES-MAC reduces idle listening energy consumption by using a duty cycle, periodic listen (i.e., turn on radio module) and sleep (i.e. turn off radio module) of sensor nodes. Cluster-based multi-hop scheduling provides high goodput in a duty-cycled environment by scheduling clusters of nodes in the listen period and opportunistically forwarding data packets in the sleep period. Priority-aware schedule switching makes more high-priority packets reach the sink node by letting high-priority packets preempt the schedules of low-priority packets. In experiments with MICA2 based sensor nodes and in simulations, the energy consumption of the radio module is reduced by 70% compared to the approaches without a duty cycle, while providing 80% 100% goodput of the approaches that provide high goodput. Service differentiation is also supported with little overhead.

In this paper, we propose a modified Tomlinson Harashima precoding (THP) method with less increase of computational complexity for the multi-user MIMO downlink system. The proposed THP scheme minimizes the influence of noise enhancement at the receivers by placing the diagonal weighted filters at both transmitter side and receiver side with square root. Compared to previously proposed non-linear precoding methods including vector perturbation (VP), the proposed THP achieves high BER performance. Furthermore, we show that the proposed THP method is implemented with lower computational complexity than that of existing modified THP and VP in literature.

In LTE-Advanced heterogeneous networks, a typical cell layout to enhance frequency utilization is to incorporate picocells and femtocells in a macrocell. However, the co-channel interference between the marcocell and picocell/femtocell is an important issue when the same frequency band is used between these systems. We have already clarified how the interference from the femto(macro) cell affects on the macro(femto) cell. In this paper, we evaluate the interference rejection characteristics by an adaptive array with user equipment (UE). The characteristics are evaluated based on the K-factor used in the Nakagami-Race Fading model and the spatial correlation that is obtained in an actual outdoor environment. It is shown that a two-element adaptive array at the macro UE (M-UE) can sufficiently reduce the interference from the femto base station (F-BS) to the M-UE even if the number of total signals exceeds the degrees of freedom of the array.

Wireless personal area networks (WPANs) will play an important role in next-generation communication networks. Currently, two technologies are being considered for the physical layer of WPANs, based on the two ultra wideband (UWB) standards, namely, multiband orthogonal frequency division multiplexing (MB-OFDM) UWB and direct-sequence (DS) UWB. The coexistence issue of these two types of WPANs in the same coverage area, raises new issues and introduces new problems which should be dealt with to avoid performance degradation. In particular, efficient radio resource management (RRM) in such environments is challenging. Indeed, the coexistence of heterogenous UWB based WPANs (UPANs) has an ad hoc nature, which requires RRM approaches that are different from traditional infrastructure-based ones. In this paper, we propose new algorithms for two RRM modules in heterogeneous UPANs, namely, radio access technology (RAT) selection and vertical handoff (VHO). To improve the overall performance of the system, our design considers possible narrowband interference (NBI) in the environment as well as the link outage probability, in the decision process. We also provide an analytical model based on a 4D Markov process to study the system in equilibrium and derive the performance metrics, namely, the new-call and handoff-call blocking probabilities, throughput and average carried traffic. Numerical results and comparisons show that our design achieves enhanced performance in terms of throughput and grade of service (GoS).

The performance of cooperative spectrum sensing (CSS) is limited not only by the imperfect sensing channels but also by the imperfect reporting channels. In order to improve the transmission reliability of the reporting channels, an object based cooperative spectrum sensing scheme with best relay (Pe-BRCS) is proposed, in which the best relay is selected by minimizing the total reporting error probability to improve the sensing performance. Numerical results show that, the reduced total reporting error probability and the improved sensing performance can be achieved by the Pe-BRCS scheme.

Turbo equalization is an iterative equalization and decoding technique that can achieve impressive performance gains for communication systems. In this letter, we investigate the turbo equalization method for the decoding of the Davey-MacKay (DM) construction over the IDS-AWGN channels, which indicates a cascaded insertion, deletion, substitution (IDS) channel and an additive white Gaussian noise (AWGN) channel. The inner decoder for the DM construction can be seen as an maximum a-posteriori (MAP) detector. It receives the beliefs generated by the outer LDPC decoder when turbo equalization is used. Two decoding schemes with different kinds of inner decoders, namely hard-input inner decoder and soft-input inner decoder, are investigated. Simulation results show that significant performance gains are obtained for both decoders with respect to the insertion/deletion probability at different SNR values.

This paper presents a method of designing transmission line couplers (TLCs) and a mixer-based receiver for dicode partial response communications. The channel design method results in the optimum TLC design. The receiver with mixers and DC balancing circuits reduces the threshold control circuits and digital circuits to decode dicode partial response signals. Our techniques enable low inter-symbol interference (ISI) dicode partial response communications without three level decision circuits and complex threshold control circuits. The techniques were evaluated in a simulation with an EM solver and a transistor level simulation. The circuit was designed in the 90-nm CMOS process. The simulation results show 12-Gb/s operation and 52mW power consumption at 1.2V.

A method for the specification of weighting functions for a spaceborne/airborne interferometric synthetic aperture radar (SAR) sensor for Earth observation and environment monitoring is introduced. This method is based on designing an optimum mismatched filter which minimizes the total power in sidelobes located out of a specified range region around the peak value point of the system point-target response, i.e. impulse response function under the constraint imposed on the peak value. It is shown that this method allows achieving appreciable improvement in accuracy performance without degradation in the range resolution.

We describe 25-Gb/s error-free transmission over multi-mode fiber (MMF) by using a transmitter based on a 1.3-µm lens-integrated surface-emitting laser (LISEL) and a CMOS laser-diode driver (LDD). It demonstrates 25-Gb/s error-free transmission over 30-m MMF under the overfilled-launch condition and over 150-m MMF with a power penalty less than 1.0 dB under the underfilled-launch condition.

We examine the relationship between 116 VHF sensor events recorded by the VHF sensor on the Maido-1 satellite and lightning strokes detected by the World Wide Lightning Location Network (WWLLN) to show that most of the VHF sensor events were caused by lightning discharges. For each VHF sensor event, the WWLLN events within 1400 km from the subsatellite point and within 1 sec, 30 sec, and 300 sec of the VHF sensor trigger time are analyzed. We find that the coincidence rates in the North and South American continents, and in Southeast/East Asia and the Australian continent are greater than 0.90. Those in the African and European continents, and in the Pacific and Atlantic Oceans are less than 0.61. These high enough coincidence rates indicate that the VHF sensor events were emitted from lightning, although the coincidence rates in the other regions are quite low because of the low detection efficiency of the WWLLN in the regions. We also focus on 6 coincident events measured by both the VHF sensor and the WWLLN. The incidence angles of the EM waves for the VHF sensor are estimated from the group delay characteristics of the recorded EM waveforms. Compared with the WWLLN lightning locations, the two incidence angles are temporally and spatially coincident. These results indicate that a large fraction of the VHF sensor events are emitted by lightning discharges.

In our previous work [2], we proposed a new concept of utility functions for rate control in communication networks. Unlike conventional utility-based rate control in which the utility function of each user is defined as a function of its transmitting data rate, in [2], we defined the utility function of each user as a function of not only its transmitting data rate but also it receiving data rate. The former is called a session-level utility function and the latter is called a user-level utility function. The user-level utility function reflects the satisfaction with the service of a user with two-way communication, which consists of transmitting and receiving sessions, better than the session-level utility function, since user's satisfaction depends on not only the satisfaction with its transmitting session but also that for its receiving session. In [2], an algorithm that required each user to know the exact utility function of its correspondent was developed. However, in some cases, this information might not be available due to some reasons such as security and privacy issues, and in such cases, the algorithm developed in [2] cannot be used. Hence, in this paper, we develop a new distributed algorithm that does not require each user to know the utility function of its correspondent. Numerical results show that our new algorithm, which does not require the utility information of the correspondent, converges to the same solution to that with the algorithm that requires the utility information of the correspondent.

In this paper, a symbol-rate clock recovery scheme for a receiver that uses an integrating decision feedback equalizer (DFE) is proposed. The proposed clock recovery using expected received signal amplitudes as the criterion realizes minimum mean square error (MMSE) clock recovery. A receiver architecture using an integrating DFE with the proposed symbol-rate clock recovery is also proposed. The proposed clock recovery algorithm successfully recovered the clock phase in a system level simulation only with a DFE. Higher jitter tolerance than 0.26 UIPP at 10 Gb/s operation was also confirmed in the simulation with an 11 dB channel loss at 5 GHz.

In situ UV-vis. absorption spectra of cytochrome c adsorbed on ITO electrode was observed with slab optical waveguide spectroscopy combining pulse potential step (PPS) between 0.3 and -0.45 V vs. Ag/AgCl. The amount of cytochrome c adsorbed on ITO electrode was estimated from the amount of coulomb of the peaks in cyclic voltammogram to be about a monolayer coverage in this experimental condition. Spectral change between oxidized and reduced cytochrome c by PPS was finished in about 20 msec with phosphate buffer solution. The results strongly proved that SOWG spectroscopy should be effective for in situ observation of ET reaction kinetics of surface adsorbed molecules.

We present an Interactive Tabu Search (ITS) algorithm to reduce the evaluation load of Interactive Evolutionary Computation (IEC) users. Most previous IEC studies used an evaluation interface that required users to provide evaluation values for all candidate solutions. However, user's burden with such an evaluation interface is large. Therefore, we propose ITS where users choose the favorite candidate solution from the presented candidate solutions. Tabu Search (TS) is recognized as an optimization technique. ITS evaluation is simpler than Interactive Genetic Algorithm (IGA) evaluation, in which users provide evaluation values for all candidate solutions. Therefore, ITS is effective for reducing user evaluation load. We evaluated the performance of our proposed ITS and a Normal IGA (NIGA), which is a conventional 10-stage evaluation, using a numerical simulation with an evaluation agent that imitates human preferences (Kansei). In addition, we implemented an ITS evaluation for a running-shoes-design system and examined its effectiveness through an experiment with real users. The simulation results showed that the evolution performance of ITS is better than that of NIGA. In addition, we conducted an evaluation experiment with 21 subjects in their 20 s to assess the effectiveness of these methods. The results showed that the satisfaction levels for the candidates generated by ITS and NIGA were approximately equal. Moreover, it was easier for test subjects to evaluate candidate solutions with ITS than with NIGA.

It is the key concern for service providers that how a web service stands out among functionally similar services. QoS is a distinct and decisive factor in service selection among functionally similar services. Therefore, how to design services to meet customers' QoS requirements is an urgent problem for service providers. This paper proposes an approach using QFD (Quality Function Deployment) which is a quality methodology to transfer services' QoS requirements into services' design attribute characteristics. Fuzzy set is utilized to deal with subjective and vague assessments such as importance of QoS properties. TCI (Technical Competitive Index) is defined to compare the technical competitive capacity of a web service with those of other functionally similar services in the aspect of QoS. Optimization solutions of target values of service design attributes is determined by GA (Genetic Algorithm) in order to make the technical performance of the improved service higher than those of any other rival service products with the lowest improvement efforts. Finally, we evaluate candidate improvement solutions on cost-effectiveness. As the output of QFD process, the optimization targets and order of priority of service design attributes can be used as an important basis for developing and improving service products.

With the fast development of mobile communication technologies, mobile multimedia services like mobile Video on Demand (VOD) are becoming prevalent. However, VOD streaming requires dedicated bandwidth to satisfy Quality of Service (QoS), and the limited wireless bandwidth will become insufficient to support the increasing number of mobile VOD users. In order to solve the problem, this paper proposes a Call Admission Control (CAC) approach which can accept new users even when the system bandwidth is insufficient. Our approach also guarantees continuous playback for subscribers by taking into account the service end time and the delay bound of the users. Simulation results demonstrate that the proposed scheme can increase the number of concurrent users and reduce the connection blocking probability significantly without playback interruption.

In OFDM-based cognitive radio systems, due to the out-of-band leakage from the secondary transmission, the interference to primary users must be considered in order to guarantee the quality of service of the primary transmission. For multiuser cognitive radio systems, there exist two crucial issues in resource allocation: fairness and efficiency, in order to balance the two issues, we proposed a new utility-based cross-layer resource allocation algorithm, which can not only control the interference to primary users caused by secondary users, but also balance the spectral efficiency and fairness among cognitive users. Further, the optimal NP-hard resource allocation problem in multiuser OFDM-based systems is reduced to the sub-optimal solution by dividing the original problem into the subcarrier allocation problem and the power allocation problem. It is shown that the proposed algorithm can obtain the best performance in terms of the average rate or the utility among existing algorithms, and at the same time, all the users obtain fair resource allocation.