In this letter, a relay-assisted transmission scenario over frequency-selective fading channels perturbed by different random carrier frequency offsets is considered. OFDM and block-double differential (BDD) design are implemented to overcome the problem of intersymbol interference (ISI) and carrier frequency offsets (CFOs). We analyze the symbol error rate (SER) performance of decode-and-forward relaying with BDD design in wireless cooperative communications over frequency-selective fading channels and derive a theoretical upper bound for average SER when the relay (R) is error free. It can be seen from our analysis that the system performance is influenced by the ability of R to decode, and when R decodes without error, both spatial and multipath diversity can be obtained without requiring any knowledge of channel state information and CFO information at the receivers. Numerical examples are provided to corroborate our theoretical analysis.

Optical buffer memory for 10-Gb/s data signal is demonstrated experimentally using a polarization bistable vertical-cavity surface-emitting laser (VCSEL). The optical buffer memory is based on an optical AND gate function and the polarization bistability of the VCSEL. Fast AND gate operation responsive to 50-ps-width optical pulses is achieved experimentally by increasing the detuning frequency between an injection light into the VCSEL and a lasing light from the VCSEL. A specified bit is extracted from the 10-Gb/s data signal by the fast AND gate operation and is stored as the polarization state of the VCSEL by the polarization bistability. The corresponding numerical simulations are also performed using two-mode rate equations taking into account the detuning frequency. The simulation results confirm the fast AND gate operation by increasing the detuning frequency as well as the experimental results.

In this paper, the performance of multiuser MIMO E-SDM systems in downlink transmission is evaluated in both uncorrelated and correlated time-varying fading environments. In the ideal case, using the block diagonalization scheme, inter-user interference can be completely eliminated at each user; and using the E-SDM technique for each user, optimal resource allocation can be achieved, and spatially orthogonal substreams can be obtained. Therefore, a combination of the block diagonalization scheme and the E-SDM technique applied to multiuser MIMO systems gives very good results. In realistic environments, however, due to the dynamic nature of the channel and processing delay at both the transmitter and the receiver, the channel change during the delay may cause inter-user interference even if the BD scheme is used. In addition, the change may also result in large inter-substream interference and prevent optimal resource allocation from being achieved. As a result, system performance may be degraded seriously. To overcome the problem, we propose a method of channel extrapolation to compensate for the channel change. Applying our proposed method, simulation results show that much better system performance can be obtained than the conventional case. Moreover, it also shows that the system performance in the correlated fading environments is much dependent on the antenna configuration and the angle spread from the base station to scatterers.

An equalizer initialization technique for least mean squares (LMS) algorithm, which can equalize frequency selective multiple input multiple output (MIMO) channels, is presented and analyzed. The proposed method conducts an initial convergence step for superior training prior to running the LMS algorithm. This approach raises the training performance while the complexity of the LMS algorithm, which is known as the simplest training algorithm, is almost the same. The proposed technique is analyzed for the initial convergence and simulated for a possible single carrier MIMO application in single carrier (SC) IEEE802.16-2004 standards. The obtained performance after coding approximates the performance of the recursive least squares (RLS) algorithm as it is presented for 33 and 55 MIMO for comparisons.

A new H.264 fast inter-mode decision algorithm based on coded block patterns is presented. Compared to the exhaustive mode search, the proposed method achieves an average 57 % reduction in computation time with negligible degradation in visual quality. The speed and rate-distortion performance is comparable to known fast algorithms that involve more elaborate mechanisms.

This letter proposes a simple modification of LEACH protocol to exploit its multi-hop scenario for user cooperation. Instead of a single cluster-head we propose M cluster-heads in each cluster to obtain the diversity of order M. All cluster-heads gather data from all sensor nodes within the cluster using the same technique as LEACH. Cluster-heads transmit gathered data cooperatively towards the destination or higher order cluster-head. We propose a code combining based cooperative protocol. We also develop the upper bounds on frame error rate (FER) for our proposal. Simulation and analysis show that our proposal can significantly prolong the system lifetime.

The very fast transients of micro-gap discharges driven by low voltage electrostatic discharging (ESDs) are investigated in the time domain. We previously developed a 12 GHz wideband measurement setup consisting of a distributed constant line system, however the observed transients due to micro-gap discharges had very fast rise times of 34 ps or less, which reached the limitation on our system. In this paper, we proposed a method for estimating wideband transients beyond the measurement limit by using the transmission loss of a high performance coaxial transmission line. The proposed method is validated by estimating an impulsive voltage waveform with rise/fall time of 16 ps from the waveform measured through a semi-rigid coaxial cable with a length of 10 m.

The inflection S-shaped software reliability growth model (SRGM) proposed by Ohba (1984) is one of the well- known SRGMs. This paper deals with the optimal software release problem with regard to the expected software cost under this model based on the Bayesian approach. To reflect the effect of the learning experience for the updated software system, we consider several improvement factors to adjust the values of parameters characterizing the inflection S-shaped SRGM. Appropriate prior distributions are assumed for such factors and the expected total software cost is formulated. The optimal release time is shown to be finite and uniquely determined. Because of the flexibility of prior distributions, the proposed Bayesian methods may be applied in many different situations. Numerical results are presented on the basis of the real data.

A parallel multiplexing scheduling (PMS) scheme is proposed for distributed antenna systems (DAS), which greatly improves average system throughput due to multi-user diversity and multi-user multiplexing. However, PMS has poor fairness because of the use of the "best channel selection" criteria in the scheduler. Thus we present a parallel proportional fair scheduling (PPFS) scheme, which combines PMS with proportional fair scheduling (PFS) to achieve a tradeoff between average throughput and fairness. In PPFS, the "relative signal to noise ratio (SNR)" is employed as a metric to select the user instead of the "relative throughput" in the original PFS. And only partial channel state information (CSI) is fed back to the base station (BS) in PPFS. Moreover, there are multiple users selected to transmit simultaneously at each slot in PPFS, while only one user occupies all channel resources at each slot in PFS. Consequently, PPFS improves fairness performance of PMS greatly with a relatively small loss of average throughput compared to PFS.

Recently, the security scheme, proposed by Kempf and Koodli, has been adopted as a security standard for Fast handover for Mobile IPv6. But, it does not prevent denial of service attacks while resulting in high computation cost. More importantly, we find that it is still vulnerable to redirection attacks because it fails to secure the Unsolicited Neighbor Advertisement messages. In this paper, Kempf-Koodli's scheme is formally analyzed through BAN-logic and its weaknesses are demonstrated.

Several scheduling algorithms have been proposed for the downlink of a Code Division Multiple Access (CDMA) system with High Data Rate (HDR). Modified Largest Weighted Delay First (M-LWDF) scheduling algorithm selects a user according to the user current channel condition, user head-of-line packet delay and user Quality of Service (QoS) requirement. Proportional Fair (PF) scheduling algorithm has also been proposed for CDMA/HDR system and it selects a user according to the ratio of the user current channel rate and the user average channel rate, which provides good performance in terms of fairness. However, when variable bit rate (VBR) traffic is considered under different channel conditions for each user, both schedulers' performance decrease. M-LWDF scheduler can not guarantee the QoS requirement to be achieved and PF scheduler can not achieve a good fairness among the users. In this work, we propose a new scheduling algorithm to enhance M-LWDF and PF schedulers performance. Proposed scheduler selects a user according to the user input traffic characteristic, user current channel condition and user QoS requirement, which consists of a delay value with a maximum violation probability. We consider the well-known effective bandwidth expression, which takes into account the user QoS requirement and the user input traffic characteristics, to select a user to be scheduled. Properties of the proposed scheduling algorithm are investigated through simulations with constant bit rate (CBR) and VBR flows and performance comparisons with M-LWDF and PF schedulers. The results show a better performance of the proposed scheduler compared with M-LWDF and PF schedulers.

This paper develops a complete architecture for constant false alarm rate (CFAR) detection based on a goodness-of-fit (GOF) test. This architecture begins with a logarithmic amplifier, which transforms the background distribution, whether Weibull or lognormal into a location-scale (LS) one, some relevant properties of which are exploited to ensure CFAR. A GOF test is adopted at last to decide whether the samples under test belong to the background or are abnormal given the background and so should be declared to be a target of interest. The performance of this new CFAR scheme is investigated both in homogeneous and multiple interfering targets environment.

In wireless cellular networks, streaming of continuous media (with strict QoS requirements) over wireless links is challenging due to their inherent unreliability characterized by location-dependent, bursty errors. To address this challenge, we present a two-step scheduling algorithm for a base station to provide streaming of continuous media to wireless clients over the error-prone wireless links. The proposed algorithm is capable of minimizing the packet loss rate of individual clients in the presence of error bursts, by transmitting packets in the round-robin manner and also adopting a mechanism for channel prediction and swapping.

We study the interaction of TCP and the proportional fair scheduling algorithm in wireless networks. We show that the additive increase and multiplicative decrease algorithm of TCP can favor bad channel users, which results in inefficient use of radio resources. To remedy the problem, a proportional queue management scheme is proposed. The effectiveness of the algorithm is shown by simulations.

A transmission line created by cables adjoined by connectors is influenced by noise from connectors with contact failure, and such noise degrades communication quality. The authors used a model of a connector with increased contact resistance in a coaxial cable and measured the electromagnetic near-field around a cable while changing positions of the model. In this paper, the result shows that the radiated electromagnetic field has no relationship with the position along the cable of a connector with increased contact resistance, when the contact condition of connector, contact resistance value, measurement position, and length of a transmission line are constant.

The wireless sensor network is a resource-constrained self-organizing system that consists of a large number of tiny sensor nodes. Due to the low-cost and low-power nature of sensor nodes, sensor nodes are failure-prone when sensing and processing data. Most presented fault-tolerant research for wireless sensor networks focused on crash faults or power faults and less on Byzantine faults. Hence, in this paper, we propose a power-saving data aggregation algorithm for Byzantine faults to provide power savings and high success rates even in the environment with high fault rates. The algorithm utilizes the concept of Byzantine masking quorum systems to mask the erroneous values and to finally determine the correct value. Our simulation results demonstrate that when the fault rate of sensor nodes is up to 50%, our algorithm still has 48% success rate to obtain the correct value. Under the same condition, other fault-tolerant algorithms are almost failed.

Frequency dependent properties of accumulation-mode MOS varactors, which are key elements in many RF circuits, are dominated by Non-Quasi-Static (NQS) effects in the carrier transport. The circuit performances containing MOS varactors can hardly be reproduced without considering the NQS effect in MOS-varactor models. For the LC-VCO circuit as an example it is verified that frequency-tuning range and oscillation amplitude can be overestimated by over 20% and more than a factor 2, respectively, without inclusion of the NQS effect.

A data analysis technology of atomic force microscopy for atomically flat silicon surfaces has been developed. Atomically flat silicon surfaces composed of atomic terraces and steps are obtained on (100) orientation 200 mm diameter wafers by annealing in pure argon ambience at 1,200 for 30 minutes. Atomically flat silicon surfaces are lead to improve the MOS inversion layer mobility and current drivability of MOSFETs and to decrease the fluctuations in electrical characteristics of MOSFETs. It is important to realize the technology that evaluates the flatness and the uniformity of atomically flat silicon surfaces. The off direction angle is calculated by using two straight edge lines selected from measurement data. And the off angle is calculated from average atomic terrace width under assumption that height difference between neighboring terraces is equal to the step height, 0.135 nm, of (100) silicon surface. The analyzing of flatness of each terrace can be realized by converting the measurement data using the off direction angle and the off angle. And, the average roughness of each terrace is about 0.017-0.023 nm. Therefore, the roughness and the uniformity of each terrace can be evaluated by this proposed technique.

Almost all the existing secret sharing schemes are based on a single dealer. Maybe in some situations, the secret needs to be maintained by multiple dealers. In this paper, we proposed a novel secret sharing scheme based on the multi-dealer by means of Shamir's threshold scheme and T. Okamoto and S. Uchiyama's public-key cryptosystem. Multiple dealers can commonly maintain the secret and the secret can be dynamically renewed by any dealer. Meanwhile, the reusable secret shadows just needs to be distributed only once. In the secret updated phase, the dealer just needs to publish a little public information instead of redistributing the new secret shadows. Its security is based on the security of Shamir's threshold scheme and the intractability of factoring problem and discrete logarithm problem.

Frequency-domain equalization (FDE) has been studied for suppressing inter-symbol interference (ISI) due to frequency selective fading in single carrier systems. When a high-mobility terminal is assumed in the system, channel transition within an FDE block cannot be ignored. The ISI reduction performance of FDE degrades since the cyclicity of the channel matrix is lost. To solve this problem, a method of dividing the received data block into multiple subblocks has been proposed, where pseudo cyclic prefix (CP) processing is introduced to realize periodicity in each subblock. In this method, the performance is degraded by the inherently-inaccurate pseudo CP. In this paper, we study the application of frequency-domain turbo equalization (FDTE) to subblock processing for improving the accuracy of pseudo CP. The simulation results show that FDTE with subblock processing yields remarkable performance improvements.