Improving fairness using dynamic weights in ATM ABR service

A new scheme termed active fairness is proposed that substantially improves fairness in allocating bandwidth among the available bit rate (ABR) connections in ATM networks. In contrast to the one set of weights used in the generalised fairness scheme, active fairness maintains two sets of weights at each link. Simulation results prove the efficacy of the proposed scheme     

Two-dimensional power-line selection scheme for lowsubthreshold-current multi-gigabit DRAM's

A two-dimensional power-line selection scheme for an iterative CMOS circuit block is proposed to reduce the subthreshold current. In this scheme, a block is divided into sub-blocks in a two-dimensional arrangement and selectively energized by two-dimensional power-line selection. It is shown to be suitable for dual word-line structure, particularly because of its single sub-word line activation. This scheme achieves a very large reduction of active current to one sixteenth, from 116 mA to 22 mA for a 1-V 16-Gb DRAM with dual word-line structure, while maintaining a speed comparable to existing multi-megabit DRAM's. The proposed scheme is promising for reducing the active power of future multi-gigabit DRAM's     

主动重发的DS／CDMA ALOHA

针对DS/CDMA ALOHA系统,本文提出了一种主动复发方案,并对主动重发时延为无限和有限值的情况分别进行了分析和研究,研究结果表明,主动重发时延为一个时隙时即可获得接近理想情况的性能。从理论计算和仿真实验的结果可以看到,这种新方案可以有效地改善DS/CDMA ALOHA协议的性能。     

Wavelength retuning without service interruption in an all‐optical survivable network

This paper proposes a new wavelength retuning (WRT) scheme in an all‐optical WDM network. Compared with the existing WRT schemes developed for all‐optical networks, which can alleviate the wavelength‐continuity constraint but cannot avoid service interruption or data loss, the proposed scheme is able to alleviate the wavelength‐continuity constraint and reduce the connection blocking probability with no service interruption to the on‐going traffic. This is achieved by allocating two routes, one for active path and one for backup path, to each incoming connection request and conducting WRT only on the backup path. The backup path provides an alternate path in case of a failure, while the active path carries traffic under normal conditions. Thus, WRT on the backup path will not cause any impact on data transmission. An optimal backup path WRT scheme and a heuristic algorithm are developed and the performance evaluation on the proposed schemes is presented. The simulation results show that the proposed optimal scheme reduces the connection blocking probability by 46.8% on average, while the proposed heuristic scheme reduces the blocking probability by 28.3% on average, all compared with the scheme without WRT. Copyright © 2009 John Wiley & Sons, Ltd.     

A method of matrix addressing polarization rotating or retarding light-valve arrays

A geometrical arrangement is described that allows matrix-addressed arrays of light valves to be built out of optically active materials which do not possess a switching threshold. Such arrays can be used for optical selectors, composers, and displays. Unlike classical coincident matrix addressing, this new scheme does not impose any limitation on addressing speed nor is it critically dependent on uniformity of switching properties within the material. The basic scheme consists of forming the rows of the matrix on one piece of material, the columns on another, and separating the two pieces with suitably oriented polarizers. This scheme can be applied to ferromagnetic, ferroelectric, and electrooptic solids and optically active liquids. A modified form of the separated matrix scheme, employing no polarizers, can be used with light scattering, absorbing, or reflecting materials which have no switching threshold.     

一种基于随机密钥的无线传感器网络加密方案

密钥的建立与管理是无线传感器网络安全的重要且基础的组成部分,是影响大规模应用的一个关键问题。近来,密钥建立与管理成为无线传感器网络安全领域一个活跃的研究分支。提出一种基于随机密钥预分配的无线传感器网络加密方案。该方案通过密钥互斥机制解决传统随机密钥预分配方案中点到点数据源认证问题。     

JOINT SPACE－FREQUENCY MULTIUSER SYMBOL DETECTOR FOR MC－CDMA SYSTEM WITH UNIFORM LINEAR ARRAY

The MultiCarrier COde Division Multiple Access (MC-CDMA) scheme is promising for relieving capacity limit problems of Direct Sequence(DS-CDMA systems due to serious InterCip Interference(ICI) and MultiUser Interference(MUI)in high-data-rate wireless communication systems.In this paper the Uniform Linear Array(ULA) is applied to the base station of macrocellular MC-CDMA systems in a frequency-selective fading channel environment.A joint space-frequency multiuser symblo sequence detector is developed for all active users within one macrocell without space-frequency channel estimation.Simultaneously,Directions-of -Arrivals (ODAs)of all active users can also be estimated.By dividing the ULA into two identical overlapping subarrays,a specific auxiliary matrix is constructed,which includes both symbol sequence and DOA information of all active users,Then,based on the subspace method,performing the eigen decomposition on such auxiliary matrix,the closed-form solution of symbol sequences and DOAs for all active users can be obtained.In comparison with schemes based on channel estimation,our algorithm need not explicitly estimate the space-frequency channel for each active user,so it has lower computation complexity,Extensive computer simulations demonstrate the overall performance of this novel scheme.     

抗高重频激光有源干扰的方案研究

在对激光末制导武器的抗干扰现状分析的基础上,对高重频干扰进行了分析,提出了抗高重频激光有源干扰的方案.该方案将高重频干扰建立数学模式后,对该数学模式进行分析,总结出该模型的规律,从而判断出高重频周期,该原理将构成方案的核心思想.该高重频信号处理方案的关键点,包括高重频周期的测定和反向高重频信号同步点的确定.该方案将有效的消除高重频有源干扰,和我们曾提出过的激光末制导炮弹武器系统的一类新型激光编码方案,构成了完备的激光末制导武器系统抗激光有源干扰方案.     

Wound Rotor Induction Generator With Sensorless Control and Integrated Active Filter for Feeding Nonlinear Loads in a Stand-Alone Grid

This paper describes a vector control scheme for a stand-alone generator based on a wound rotor induction machine with rotor side control. The stand-alone generator refers to an isolated grid feeding a local load. The primary objective of the control scheme is to maintain constant voltage and frequency at the output of the generator irrespective of prime mover speed variation. A novel, simple, and easily implementable sensorless control scheme is proposed. The issue of power quality, which is one of the main concerns of a stand-alone generation system, is also addressed. This is done by incorporating the active filter concept in the control scheme to cancel significant harmonics. A method of unit vector generation for field-oriented control is proposed. A laboratory prototype consisting of back-to-back insulated-gate bipolar transistor converters and a TMS320F240 DSP controller is developed. Detailed experimental results are presented which demonstrate and validate the effectiveness of the proposed scheme.     

基于北斗系统的伪码捕获技术的研究

北斗卫星导航定位系统是我国自主研发的有源三维卫星定位与通信系统.北斗卫星信号的捕获是北斗用户接收机的关键技术之一,捕获性能的优劣直接影响着北斗导航系统的精度和实时性要求.本文基于北斗系统,在FFT并行捕获算法的基础上研究分析了一种相位补偿和同步块累加的伪码捕获算法,并对该算法的性能进行了分析.理论分析和仿真结果表明,该方案能够大大提高信噪比,提高信号的捕获效率.     

一种基于提升方案小波和纹理块的图像鲁棒水印算法

数字水印技术是多媒体信息安全领域的一个重要的研究课题。文章在对宿主图像小波低频子带进行纹理块检测的基础上，提出一种基于提升方案小波和纹理块曲图像鲁棒水印算法。该算法可以自适应的确定出二值图像水印在中频子带的嵌入强度，从而保证了所嵌入的水印在不可见性的前提下对常见的一些图像处理操作具有很强的鲁棒性。试验结果验证了所提出方法的有效性。     

Threshold-Voltage Control of AC Performance Degradation-Free FD SOI MOSFET With Extremely Thin BOX Using Variable Body-Factor Scheme

The bias scheme of the variable body-factor fully depleted (FD) silicon-on-insulator (SOI) MOSFET, which has been previously proposed, is reexamined. Using a new scheme, the inversion and accumulation on the substrate in the active state can be avoided, and thus, ac performance in the active state is not degraded even with extremely thin buried-oxide (BOX), owing to the depletion of the substrate. Moreover, subthreshold leakage can be sufficiently suppressed in the standby state, owing to extremely thin BOX. This scheme provides threshold-voltage adjustability for the suppression of interdie and within-die variation in the active state. This device scheme is also applicable to multichannel FD SOI MOSFETs including FinFETs with a low-aspect-ratio fin, where the back-bias scheme can be applied     

A low-power microcontroller having a 0.5-/spl mu/A standby current on-chip regulator with dual-reference scheme

We present a microcontroller having a 0.5-/spl mu/A standby current on-chip regulator. To break through the area overhead problem which a conventional regulator scheme suffers from to achieve small standby current, we propose a dual-reference scheme in which one voltage reference circuit is provided for active mode and another voltage reference circuit is provided for standby mode. For the voltage reference circuit for standby mode, a resistor-free circuit was used to achieve small current consumption without occupying large area. The microcontroller was fabricated in a 0.18-/spl mu/m CMOS process. The implementation and measurement results show that the dual-reference scheme achieves 0.5-/spl mu/A current consumption of the regulator in standby mode with 50% smaller area than the conventional scheme. The measured standby current of the whole chip was 2.0 /spl mu/A.     

A single-phase capacitor clamped converter operated simultaneously as a PWM rectifier and an active power filter

A control scheme is proposed that employs an active rectifier to work simultaneously as an active power filter to decrease current harmonics. The adopted capacitor clamped rectifier is controlled to draw a sine wave line current with low current harmonics. A voltage controller, three capacitor voltage compensators and one current controller are used in the proposed control algorithm to achieve a constant DC bus voltage, balanced capacitor voltages and line current tracking. The validity of the proposed system is proved by the results of computer simulations and experimental tests.     

Transfer function synthesis using a finite-gain amplifier

An active RC circuit employing a single finite–gain amplifier, one two–port and two ono–ports, has been presented here for the realization of n general voltage transfer function without positive real axis zeros. The comparative merits of the scheme with respect to that proposed by Rao (1969) are that the synthesis procedure is simpler and the number of passive circuit elements required is smaller. The coefficient of realization of the synthesized transfer function can always be made equal to unity with the scheme. A few examples are included to illustrate the synthesis procedure.     

An Improved and Secure Two-factor Dynamic ID Based Authenticated Key Agreement Scheme for Multiserver Environment

The smart card based password authentication scheme is one of the most important and efficient security mechanism, which is used for providing security to authorized users over an insecure network. In this paper, we analyzed major security flaws of Jangirala et al.’s scheme and proved that it is vulnerable to forgery attack, replay attack, user impersonation attack. Also, Jangirala et al.’s scheme fail to achieve mutual authentication as it claimed. We proposed an improved two factor based dynamic ID based authenticated key agreement protocol for the multiserver environment. The proposed scheme has been simulated using widely accepted AVISPA tool. Furthermore, mutual authentication is proved through BAN logic. The rigorous security and performance analysis depicts that the proposed scheme provides users anonymity, mutual authentication, session key agreement and secure against various active attacks.     

Performance comparison of OFDM bandwidth request schemes in fixed IEEE 802.16 networks

IEEE 802.16 standard specifies two contention based bandwidth request schemes working with OFDM physical layer specification in point-to-multipoint (PMP) architecture, the mandatory one used in region-full and the optional one used in region-focused. This letter presents a unified analytical model to study the bandwidth efficiency and channel access delay performance of the two schemes. The impacts of access parameters, available bandwidth and subchannelization have been taken into account. The model is validated by simulations. The mandatory scheme is observed to perform closely to the optional one when subchannelization is active for both schemes.     

Measurements of BER performance for bipolar encoding of an SFS

This paper reports on the measurements of bit error rate (BER) performance for a broad-band optical communications scheme that encodes the power spectrum of an erbium-doped superfluorescent fiber source (SFS) with bipolar equivalent codes. The proposed scheme, like spectrum-sliced wavelength division multiplexing (WDM), suffers from the excess noise associated with the detection of a thermal-like source. BER calculations based on measured testbed characteristics and a simple model are compared with BER measurements for one and two active users. In addition, the performance of a single user in the presence of broad-band spectral interference is investigated, giving a preliminary estimate of multiuser capacity. This paper discusses various solutions for increasing network capacity and performance, relevant to the proposed scheme as well as to wavelength division multiplexing (WDM)     

Provision of continuous VCR functions in interactive broadcast VoD systems

Video broadcasting is one of the feasible solutions to implement a large-scale video-on-demand (VoD) system. Nevertheless, it is still an open issue for the provision of continuous VCR functions in a delay insensitive broadcast VoD system. In this paper, we propose to jointly optimize an active buffer management scheme with contingency channels to support the VCR functions in an efficient protocol called partitioned broadcasting. We develop a greedy channel management scheme by exploiting the property of the broadcasting protocol such that the system bandwidth capacity can be fully utilized. Incorporating the channel management scheme with the partitioned video broadcast, the VoD system not only provides delay insensitive services but also handles all the interactive requests. Extensive simulation results demonstrate that the partitioned broadcasting system outperforms the traditional system based on the staggered broadcasting protocols. It is found that 20 broadcasting channels and 10 contingency channels are sufficient to support on average 720 customers for a single video with less that one second start-up delay and all types of VCR functions.     

Scalable key exchange transformation: from two-party to group

A modular method which derives a scalable construction of a group key exchange (GKE) scheme from a two-party key exchange (KE) one is presented. By combining the method presented with the compiler by Katz and Yung (see Advances in Cryptology-CRYPTO 2003, Springer-Verlag, LNCS, 2729, p.110-125) a scalable compiler can be obtained that transforms any two-party KE protocol secure against a passive eavesdropper to an authenticated GKE one secure against a stronger active adversary.