The concept of personal networks is very user-centric and representative for the next generation networks. However, the present security mechanism does not consider at all what happens whenever a mobile node (device) is compromised, lost or stolen. Of course, a compromised, lost or stolen mobile node (device) is a main factor to leak stored secrets. This kind of leakage of stored secrets remains a great danger in the field of communication security since it can lead to the complete breakdown of the intended security level. In order to solve this problem, we propose a 3-way Leakage-Resilient and Forward-Secure Authenticated Key Exchange (3LRFS-AKE) protocol and its security architecture suitable for personal networks. The 3LRFS-AKE protocol guarantees not only forward secrecy of the shared key between device and its server as well as providing a new additional layer of security against the leakage of stored secrets. The proposed security architecture includes two different types of communications: PN wide communication and communication between P-PANs of two different users. In addition, we give a performance evaluation and numerical results of the delay generated by the proposed security architecture.

Optical Burst Switching (OBS) is one of the most promising switching technologies for next generation optical networks. As delay-sensitive applications such as Voice-over-IP (VoIP) have recently become popular, OBS networks should guarantee stringent Quality of Service (QoS) requirements for such applications. Thus, this paper proposes an Adaptive Loss-aware Flow Control (ALFC) scheme, which adaptively decides on the burst offset time based on loss-rate information delivered from core nodes for assigning a high priority to delay-sensitive application traffic. The proposed ALFC scheme also controls the upper-bounds of the factors inducing delay and jitter for guaranteeing the delay and jitter requirements of delay-sensitive application traffic. Moreover, a piggybacking method used in the proposed scheme accelerates the guarantee of the loss, delay, and jitter requirements because the response time for flow control can be extremely reduced up to a quarter of the Round Trip Time (RTT) on average while minimizing the signaling overhead. Simulation results show that our mechanism can guarantee a 10-3 loss-rate under any traffic load while offering satisfactory levels of delay and jitter for delay-sensitive applications.

Multiple-Input Multiple-Output (MIMO) wireless systems offer both high data rates and high capacity. Since different signals are transmitted by different antennas simultaneously, interference occurs between the transmitted signals. Each receive antenna receives all the signals transmitted by each transmit antenna simultaneously. The receiver has to detect each signal from the multiplexed signal. A Minimum Mean Square Error (MMSE) algorithm is used for spatial filtering. MMSE filtering can realize low complexity signal detection, but the signal output by MMSE filtering suffers from interference by the other signals. MMSE-SIC combines MMSE filtering and Soft Interference Cancellation (SIC) with soft replicas and can achieve good Bit Error Rate (BER) performance. If an irregular LDPC code or a turbo code is used, the reliability and BER of the information bits output by the decoder are likely to be higher and better than the parity bits. In MMSE-SIC, bits with poor reliability lower the accuracy of soft replica estimation. When the soft replica is inaccurate, the gain obtained by SIC is small. M-ary Phase Shift Keying (PSK) and M-ary Quadrature Amplitude Modulation (QAM) also achieve high data rates. Larger constellations such as 8 PSK and 16 QAM transfer more bits per symbol, and the number of bits per symbol impacts the accuracy of SIC. Unfortunately, increasing the number of bits per symbol is likely to lower the accuracy of soft replica estimation. In this paper, we evaluate three mapping schemes for MMSE-SIC with an LDPC code and a turbo code with the goal of effectively increasing the SIC gain. The first scheme is information reliable mapping. In this scheme, information bits are assigned to strongly protected bits. In the second scheme, parity reliable mapping, parity bits are assigned to strongly protected bits. The last one is random mapping. Computer simulations show that in MMSE-SIC with an irregular LDPC code and a turbo code, information reliable mapping offers the highest SIC gain. We also show that in MMSE-SIC with the regular LDPC code, the gains offered by the mapping schemes are very small.

A new adaptive model based on fuzzy integrals has been presented and used for combining three well-known methods, Eigenface, Fisherface and SOMface, for face classification. After training the competence estimation functions, the adaptive mechanism enables our system the filtering of unsure judgments of classifiers for a specific input. Comparison with classical and non-adaptive approaches proves the superiority of this model. Also we examined how these features contribute to the combined result and whether they can together establish a more robust feature.

In AlGaN/GaN high electron mobility transistors (HEMTs), drain current reduction by current collapse phenomenon is a big obstacle for a high efficient operation of power amplifier application. In this study, we investigated the effects of SiN passivation film quality on the electrical characteristics of AlGaN/GaN HEMTs. First, we conducted some experiments to investigate the relationship between electrical characteristics of AlGaN/GaN HEMTs and various conditions of SiN passivation film by plasma enhanced chemical vapor deposition (PE-CVD). We found that both gate current leakage and current collapse were improved simultaneously by SiN passivation film deposited by optimized condition of NH3 and SiH4 gas flow. It is found that the critical parameter in the optimization is a IN-H/ ISi-H ratio measured by Fourier transforms infrared spectroscopy (FT-IR) spectra. Next, a thermal CVD SiN was applied to the passivation film to be investigated from the same point of view, because a thermal CVD SiN is well known to have good quality with low hydrogen content and high IN-H/ISi-H ratio. We confirmed that the thermal CVD SiN passivation could improve much further both of the gate leakage current and the current collapse in AlGaN/GaN-HEMTs. Furthermore, we tried to apply the thermal CVD SiN to the gate insulator in MIS (Metal Insulator Semiconductor) structure of AlGaN/GaN HEMTs. The thermal CVD SiN passivation was more suitable for the gate insulator than PE-CVD SiN passivation in a view of reducing current collapse phenomena. It could be believed that the thermal CVD SiN film is superior to the PE-CVD SiN film to achieve good passivation and gate insulator film for AlGaN/GaN HEMTs due to the low hydrogen content and the high IN-H/ISi-H ratio.

Low-power dry-etching process has been adopted to study the influence of dry-etching on Ohmic contact to p-GaN. When the surface layer of as-grown p-GaN was removed by low-power SiCl4/Cl2-etching, no Ohmic contact can be formed on the low-power dry-etched p-GaN. The same dry-etching process was also applied on n-GaN to understand the influence of the low-power dry-etching process. By capacitance-voltage (C-V) measurement, the Schottky barrier heights (SBHs) of p-GaN and n-GaN were measured. By comparing the change of measured SBHs on p-GaN and n-GaN, it was suggested that etching damage is not the only reason responsible for the degraded Ohmic contacts to dry-etched p-GaN and for Ohmic contact formatin, the original surface layer of as-grown p-GaN have some special properties, which were removed by dry-etching process. To partially recover the original surface of as-grown p-GaN, high temperature annealing (1000C 30 s) was tried on the SiCl4/Cl2-etched p-GaN and Ohmic contact was obtained.

This paper will review the development of SiC power devices especially SiC power junction field-effect transistors (JFETs). Rationale and different approaches to the development of SiC power JFETs will be presented, focusing on normally-OFF power JFETs that can provide the highly desired fail-save feature for reliable power switching applications. New results for the first demonstration of SiC Power ICs will be presented and the potential for distributed DC-DC power converters at frequencies higher than 35 MHz will be discussed.

The performance of recently developed Large Signal (LS) HBT model was evaluated with extensive LS measurements like Power spectrum, Load pull and Inter-modulation investigations. Proposed model has adopted temperature dependent leakage resistance and a simplified capacitance models. The model was implemented in ADS as SDD. Important feature of the model is that the main model parameters are taken directly from measurements in rather simple and understandable way. Results show good accuracy despite the simplicity of the model. To our knowledge the HBT model is one of a few HBT models which can handle high current & Power HBT devices, with significantly less model parameters with good accuracy.

In this letter, we propose a simple reversible watermarking method for JPEG images using the characteristics of JPEG compression. The method embeds a watermark into a JPEG image, and it extracts the watermark from the watermarked JPEG image and at the same time can recover the watermarked JPEG image to an original unwatermarked JPEG image. Moreover we investigate the number of embeddable blocks, the quality of watermarked images, and the increase of file-size by embedding a watermark.

A reversible watermark algorithm with large capacity has been developed by applying the difference expansion of a generalized integer transform. In this algorithm, a watermark signal is inserted in the LSB of the difference values among pixels. In this paper, we apply the prediction errors calculated by a predictor in JPEG-LS for embedding watermark, which contributes to increase the amount of embedded information with less degradation. As one of the drawbacks discovered in the above conventional method is the large size of the embedded location map introduced to make it reversible, we decrease the large size of the location map by vectorization, and then modify the composition of the map using the local characteristics. We also exclude the positions such that the modification in the embedding operation cannot increase the capacity but merely degrade the image quality, which can be applicable to the conventional methods.

This paper studies packet scheduling schemes with QoE (user-level QoS) guarantee for audio-video transmission in a wireless LAN with HCF controlled channel access (HCCA) of the IEEE 802.11e MAC protocol. We first propose the static scheduling (SS) scheme, which grants adjustable transmission opportunity (TXOP) duration for constant bit rate (CBR) traffic. The SS scheme can determine the minimum TXOP duration capable of guaranteeing high QoE; it can maximize the number of admitted flows. As the burstiness of variable bit rate (VBR) traffic cannot be absorbed by the SS scheme, we also propose the multimedia priority dynamic scheduling (MPDS) scheme, which can absorb the burstiness through allocating additional TXOP duration. We then compare the SS scheme, the MPDS scheme, and the reference scheduler (TGe scheme) in terms of application-level QoS and user-level QoS (QoE). Numerical results show that in the SS scheme, the QoE can be kept relatively higher even when the TXOP duration is reduced in the case of video with the I picture pattern; this implies that more flows can be admitted. In the case of video with the IPPPPP picture pattern, which has the VBR characteristic more remarkably, reducing the TXOP duration according to the SS scheme will deteriorate the QoS level. In this case, the MPDS scheme performs better when the number of multimedia stations is small. However, the performance of the MPDS scheme deteriorates with the increase of the number of multimedia stations, though the results are comparable to or even better than those of the SS and TGe schemes.

An integrated power and rate control algorithm is proposed to satisfy the requirements of both user's data rate and signal quality. This algorithm lets only one representative user in each cell participate in the distributed power control and assigns the power levels to other users according to some constant power ratios. In addition to reducing the computational complexity, the proposed algorithm also gains larger throughput for the same number of iterations and finds a feasible power set faster than the other algorithm does.

The present paper introduces the construction of a class of sequence sets with zero-correlation zones called zero-correlation zone sequence sets. The proposed zero-correlation zone sequence set can be generated from an arbitrary perfect sequence and an arbitrary Golay complementary sequence pair. The proposed construction is a generalization of the zero-correlation zone sequence construction previously reported by the present author. The proposed sequence set can successfully provide CDMA communication without co-channel interference.

The dispersion and the splice characteristics of optical fibers with trench-index profile are investigated. The normalized distance between core and trench is preferably larger than 3.0 to realize complete compatibility with the standard G.652 fiber in terms of chromatic dispersion. The optical fiber realizes compatibility with ITU-T Recommendation G.652 fiber and bend-insensitivity simultaneously. Fabricated fibers with the trench-index profiles can be spliced to standard single-mode fiber with low losses, which have similar values with simulation results.

We propose a new bidirectional gigabit mm-wave wavelength division multiplexed-radio over fiber link which shares the same wavelength. As the downlink, the central station transmits a 30 GHz single sideband wireless signal which is modulated 1.25 Gbps and also transmits a remote 32 GHz local oscillator for down-conversion of a uplink wireless signal by using a mach-zehnder modulator and a fiber bragg grating. As the uplink, the base station transmits a down-converted 1.25 Gbps wireless signal by using a reflective semiconductor optical amplifier. We achieve a BER < 10-9 in the downlink at -14.05 dBm and uplink at -12.5 dBm after 20 km transmission.

The IEEE 802.11e standard defines several important techniques that guarantee the quality of service (QoS) of multimedia communications in wireless LAN applications. A key technique introduced in the standard is an efficient media access control based on the Hybrid Coordination Function (HCF), which assigns an appropriate transmission opportunity (TXOP) to each flow for satisfying several requirements on the flow, such as delay bound and communication bandwidth. Although the simple scheduler designed in HCF could provide an efficient tool to guarantee the QoS in wireless LAN applications, it has a serious drawback, wherein a useless bandwidth assignment frequently occurs. Such assignments occur primarily due to a limitation of the scheme, wherein all the flows share the same service interval (SI). In this paper, we propose a new scheduling scheme that associates each flow with its own SI according to the hardness of the required SI. The effect of this approach is experimentally evaluated by simulation, the results of which indicate that the number of admitted flows and network resource utilization increase due to the proposed scheme.

The RFID (Radio Frequency IDentification) tag technology is expected as a tool of localization. By the localization of RFID tags, a mobile robot which installs in RFID readers can recognize surrounding environments. In addition, RFID tags can be applied to a navigation system for walkers. In this paper, we propose an adaptive likelihood distribution scheme for the localization of RFID tags. This method adjusts the likelihood distribution depending on the signal intensity from RFID tags. We carry out the performance evaluation of estimated position error by both computer simulations and implemental experiments. We show that the proposed system is more effective than the conventional system.

Due to the dynamics of topology and resources, Call Admission Control (CAC) plays a significant role for increasing resource utilization ratio and guaranteeing users' QoS requirements in wireless/mobile networks. In this paper, a dynamic multi-threshold CAC scheme is proposed to serve multi-class service in a wireless/mobile network. The thresholds are renewed at the beginning of each time interval to react to the changing mobility rate and network load. To find suitable thresholds, a reward-penalty model is designed, which provides different priorities between different service classes and call types through different reward/penalty policies according to network load and average call arrival rate. To speed up the running time of CAC, an Optimized Genetic Algorithm (OGA) is presented, whose components such as encoding, population initialization, fitness function and mutation etc., are all optimized in terms of the traits of the CAC problem. The simulation demonstrates that the proposed CAC scheme outperforms the similar schemes, which means the optimization is realized. Finally, the simulation shows the efficiency of OGA.

One of the most promising applications of a mobile ad hoc network is a vehicular ad hoc network (VANET). Each vehicle is aware of its position information by GPS or other methods, so position-based routing is a useful approach in VANET. The position-based routing protocol can be classified roughly into a next-hop forwarding method and a directed flooding method. We evaluate performance of both methods by analytic approach and compare them in this paper. From the evaluation results, we conclude that it is effective for the position-based routing to choose either the next-hop forwarding method or the directed flooding method according to the environment. Then we propose the hybrid transmission method which can select one of them according to the environment, and clarify that the proposed method can keep the packet delivery ratio at a high level and reduce the delay time.

A key issue in QoS-provisioning real-time wireless communications is to provide the QoS requirement with low energy consumption. In this paper, we propose an energy-efficient error correction scheme for real-time communications with QoS requirements in wireless networks. The QoS requirement of a message stream is modeled with (m, k) constraint, implying that at least m messages should be sent to a receiver during any window of k periods. The proposed scheme adaptively selects an error correcting code in an energy-efficient manner so that it maximizes the number of QoS provisionings per unit energy consumption.