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Communication Technology, 2006. ICCT '06. International Conference on

Date 27-30 Nov. 2006

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Displaying Results 1 - 25 of 393
  • Research on a user-centered design method for interactive online teaching system

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5078 KB) |  | HTML iconHTML  

    With the rapid development of Internet, online teaching is booming and is gradually moving into the daily lives of people. More and more interactive online teaching systems are required. Yet the operational interactive online teaching system design and development methods are fewer. On the foundation of the analytical research on personas, scenarios, prototype and participatory design, this paper presents an integrated user-centered design method. It combines personas, scenarios, prototype and participatory design with the interactive online teaching system design and development process. The main steps of the design method are described in detail. And how to make use of personas, scenarios, prototype and participatory design in the design and development process is discussed. This method is very conducive to the interactive online teaching system design and development. View full abstract»

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  • Indoor channel prediction and measurement for wireless local area network (WLAN) system

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5453 KB) |  | HTML iconHTML  

    There are two basic way to deploy wireless local area network (WLAN) access point in an indoor scenario. Manual deployment of a system using site measurement based on empirical measurement and prediction using software tool that have signal propagation models. The measurement campaign was based on 2.4 GHz ISM band and conducted within campus KUiTTHO building. A measurement of signal level within indoor environment is done without presence of people movement. The measurement aims was to find empirical parameters for one slope models. Statistical analysis for site measurement in this paper follows the analysis that had been done in [3]. Results from both prediction and measurement campaign were compared and conclusions are drawn for the need of practical planning of indoor WLAN system coverage. View full abstract»

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  • A new Heuristic Operator for Job Shop Scheduling Problems

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5926 KB) |  | HTML iconHTML  

    Job shop scheduling problem is a NP-hard question. This paper proposes a new heuristic operator: activating operator; By means of shifting schedules into the most closed active schedules, the operator can limit the searching space (or make it close) to active schedules, which by far increases the possibility of finding the optimal solution. Because of the strong optimizing ability of the activating operator, using it in various algorithm to solve JSP, such as genetic algorithm and simulated annealing algorithm, can promote their efficiency and precision. Experiment results showed the operator's outstanding improvement to the SA and the GA. View full abstract»

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  • Joint Detection of Frequency Offset and MAI for MC-CDMA Systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4506 KB) |  | HTML iconHTML  

    Multi-carrier (MC) CDMA technique can reduce the interference and improve the performance of the system in fading channel. But the frequency offset and multiple access interference (MAI) are obstructive to its performance. In this paper, combining the PIC multiuser detection and frequency offset estimation based on maximum likelihood function guard interval, we propose a joint detection which called M-ML-MPIC (modified maximum likelihood multistage parallel interference canceller) to correction the frequency offset and MAI simultaneously. The numerical results of the performance analysis and comparisons of conventional schemes with the proposed method are given. View full abstract»

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  • PAPR Reduction of OFDM Signals using Radial Basis Function Neural

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3667 KB) |  | HTML iconHTML  

    In this paper we investigate a novel peak-to-average power ratio (PAPR) reduction method based on radial basis function network (RBFN). The RBFN can be regarded as a method of adaptive curve-fitting interpolator and is used to generate optimum mapping pattern to reduce the PAPR in this paper. Our simulation results show that our proposed method has significant performance advantages with low computational complexity compared to the conventional methods. View full abstract»

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  • New Parallel Interference Cancellation/Decoding for Convolutionally Coded CDMA Systems over Fading Channel

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3856 KB) |  | HTML iconHTML  

    In this paper, based on soft computation of tentative values, a new parallel interference cancellation and decoding (soft PIC/decoding) is proposed for convolutionally coded DS-CDMA systems. Two forms of soft PIC/decoding are analyzed, and compared over Rayleigh fading channel. It shows that the soft PIC/decoding achieves the dominant performance gain if the tentative decisions of coded symbols are computed in hyperbolic tangent function in terms of the sum of initial a priori log-likelihood rate (LLR) and updated a priori LLR, while a significant performance loss will occur if the tentative decisions of coded symbols are computed in hyperbolic tangent function in terms of the updated a priori LLR only. Besides, we compare the soft PIC/decoding with matched-filter (MF) receiver and conventional PIC/decoding, which shows that the soft PIC/decoding dominantly outperforms the MF receiver and conventional PIC/decodings. View full abstract»

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  • A Novel Self Configuring Dynamic Firewall for Load Reduction of Network Administrator

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (597 KB) |  | HTML iconHTML  

    In this paper we propose a system that shall enable network administrator to manage things with ease. The fire wall called DynFirewall proposed by us is a dynamically configurable firewall which configures itself according to user needs. Firewalls protect internal networks from outside attacks. However, to maintain integrity and order in a network we need some mechanism to control unwarranted traffic that spreads from and within that network. We call this mechanism DynFireWall- A dynamic firewall configuration. Since all users in the network are members of the authenticated user group, DynFireWall uses the central authentication system to authorize particular traffic for particular hosts. If all traffic from all internal hosts is authenticated, chances of stray traffic polluting the network shall be minimized. Unlike Al-based systems however, DynFireWall relies on the axiom that humans far exceed computers in the game of determining right things from wrong. Thus, instead of taking decisions on its own, it generates a list of options and solicits manual intervention for choice. View full abstract»

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  • Backdoor Intrusion in Wireless Networks- problems and solutions

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (595 KB) |  | HTML iconHTML  

    Wireless networks and ubiquitous availability of the global Internet have already changed dramatically the way we communicate, conduct business, and organize our society. With current research and developments in sensor networks and pervasive computing, we are even creating a new networked world. However, the benefits associated with information and communication technology imply new vulnerabilities. In wired networks we have to take care of front door security but same solutions do not apply to wireless networks and they have weak security solutions. The wireless networks by inherently insecure. In this paper we address the threats in wireless networks in detail and we propose novel solutions which will not only detect the attack on the network but will also take counter measures to save integrity of wireless networks. View full abstract»

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  • A Synchronization Algorithm for OFDM based on Training Cyclic Prefix

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3114 KB)  

    This paper presents an OFDM synchronization algorithm, which utilizes the training cyclic prefix. The algorithm, which conquers the problem of only utilizes training sequence or cyclic prefix, not only improves the performance of symbol timing and fractional frequency offset estimation, but also estimates the integral frequency offset under certainty range. The complexity of this algorithm is very small; simulation shows this algorithm completely solves the synchronization acquisition problem of OFDM system in practice. View full abstract»

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  • Parameter Estimation of Frequency-Hopping (FH-SS) Signals Using Modified Autocorrelation Techniques

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB) |  | HTML iconHTML  

    The paper deals with the estimation of two main parameters of frequency-hopping spread spectrum (FH-SS) signals': hop rate and epoch time. Hop rate is the number of frequency changes per second and it is equivalent to the code clock rate. Epoch time is the timing offset between the first hop and the receiver's clock when the transmitter and the receiver are not synchronized. Multiple-hop autocorrelation (MHAC) processor is used for estimating the hop rate of FH signals in the presence of broadband thermal noise. During the hopping time, the single-hop autocorrelation (SHAC) processor can be also used to estimate the epoch time. Previous work on both estimators assumes precise knowledge of the signal power, which in practical applications is usually not available apriori. Therefore modified MHAC and SHAC estimators are proposed here, which do not require prior knowledge of signal power. However, the signal power is estimated first and then utilized in the hop rate or epoch time estimation .The performance of the proposed estimators has been tested using extensive computational experiments. The estimators of hop rate for known and unknown signal power approach the same value for signal-to-noise ratio (SNR) ges 0 dB and the error in the estimation < 10% and similar results were obtained for epoch time, while the error in the estimation of signal power < 5% for SNR ges 0 dB. View full abstract»

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  • Hardware Implementation of 64B/66B Encoder/Decoder for 10-Gigabit Ethernet

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3498 KB) |  | HTML iconHTML  

    The encoding and decoding rules of 64B/66B and inherent characteristic among 64B/66B codes are studied in this paper. A hardware implementation of 64B/66B encoder/decoder is introduced, which combines the advantages of lookup-table and logic analysis methods with low resource consumption, High speed and high reliability. The algorithm of encoding and decoding is described with Verilog HDL, and was simulated and synthesized with high performance FPGA of Xilinx. So the hardware circuit is realized to validate the feasibility of this method. The design of different high speed 64B/66B encoding and decoding module or IC is easily fulfilled with it. View full abstract»

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  • An Approximate Approach of Finding the Number of Guard Channels in Wireless Communication Systems

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3019 KB) |  | HTML iconHTML  

    To realize real-time call admission control (RCAC), it's very important to get the number of guard channels quickly and accurately, when such parameters as the handover call blocking probability, the number of cell channels and both new and handover calls' load are specified. This paper derives an approximate formula of guard channels and then presents a new algorithm. We validates that, compared with the multi-iteration probing algorithm, the new algorithm can get the number of guard channels quickly and accurately. View full abstract»

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  • Novel Virtual Source Based Multicast Routing Algorithm in WDM Networks with Sparse Light Splitting

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4237 KB) |  | HTML iconHTML  

    Wavelength-division multiplexed (WDM) networks using wavelength-routing are considered to be potential candidates for the next generation wide area backbone networks. A node in the network may have both wavelength conversion and splitting capabilities which is called as virtual source. It is assumed that virtual sources are limited in number and are distributed evenly in the network. One virtual source based algorithm has been proposed in previous work. But this scheme leads to high tree cost and the virtual source is easy to be exhausted. In this paper, we propose two improved virtual source based algorithms that constructs all-optical multicast trees. We directed detailed simulations. The results show that our mechanism builds light-trees with the least wavelength channel cost and with the smallest number of wavelengths under certain number of multicast sessions. View full abstract»

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  • A Cost-Based Approach to a Reliable Multicast Transport Protocol

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3870 KB) |  | HTML iconHTML  

    In this paper we provide a new approach to estimate the link usage of multicast reliable transport protocols. It can be used as a benchmark to evaluate their scalability. We have chosen, as a case study, a multicast reliable transport protocol called RCCMP. It has been designed to be simple, scalable, reliable and TCP-friendly. The link cost is due to data, retransmitted data, and characteristic packets of multicast protocols such as control packets. For RCCMP, control packets are used to estimate the number of receivers involved in the session. Also, the reliability cost has to be added to the bandwidth consumption. Simulation results demonstrate that the proposed models are able to predict the bandwidth usage. View full abstract»

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  • SARED: Stabilized ARED

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3287 KB) |  | HTML iconHTML  

    AQM attempts to provide high network utilization with low loss and delay by regulating queues at bottleneck links. Most AQM algorithms suffer from instability. This paper focuses on the queue size estimation problem in RED and ARED gateways. Conventional RED and ARED gateways use exponentially weighted moving averages (EWMA) to estimate the queue size. More queue stability has been yielded by using two different queue weights in ARED instead of one fixed queue weight. View full abstract»

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  • Adaptive Processing of Wideband Signals through Interpolation and Direct Data Domain Least Square Techniques using Semicircular Array

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (573 KB) |  | HTML iconHTML  

    A multistage analysis procedure that combines electromagnetic analysis with signal processing is used to solve a problem in radar and mobile communication. Initially, electromagnetic principles are applied to compensate for the effects of mutual coupling between antenna elements, including the effect of nonuniformity in spacing between the elements. Then a direct data domain least square methodology is implemented to yield the signal of interest. These two techniques are dealt with narrowband signal. In this paper, we show that the above methodology can be applied in wideband signals using semicircular array. The performance and accuracy of the proposed technique is observed through two simulated examples. First example, the antenna elements are to be point sources. And second example, the mutual coupling between actual elements is taken into account. The effect of mutual coupling reduces the signal bandwidth that the proposed technique can deal with. View full abstract»

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  • Two Dimensional Direction of Arrival Estimation using Single Snapshot of Nonuniformly Spaced Planar Array

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB) |  | HTML iconHTML  

    Direction of arrival estimation (DoA) is one of the most demanding problems which one has to solve for localizing and tracking multiple rapidly moving targets as in radar, mobile communication and in other areas. In this paper, an approach is presented for two dimensional direction of arrival (2D-DoA) estimation using a single snapshot of the voltages measured at nonuniformly spaced omnidirectional isotropic point sources in a planar array. This is very useful to reach a real time or near to real time situation .The array elements are placed on a plane and arranged either exponentially or sinusoidally. The voltages induced in the antenna elements due to all signals impinging on the planar array at a particular instance of time are preprocessed by applying a transformation matrix to the measured snapshot of voltages. This electromagnetic preprocessing technique is used to compensate for the lack of nonuniformity in a planar array. Through this interpolation technique we perform 2D-DoA estimation using a modified Matrix Pencil technique. Limited numerical examples are presented to illustrate the performance and accuracy of the proposed method. View full abstract»

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  • Novel MIMO HARQ Schemes Jointly Utilizing Chase Combining

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3921 KB) |  | HTML iconHTML  

    In this paper we propose several novel HARQ schemes for MIMO system which jointly utilize bit-wise soft- information (BWSI) chase combining. Retransmission mechanisms to obtain ARQ diversity are developed. We present the detection algorithm and how to jointly utilize the BWSI derived from former retransmission to improve BER performance. Finally we propose a new retrans scheme using channel codes based on BWSI feedback, which can achieve better performance compared to normal HARQ with acceptable complexity. View full abstract»

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  • A Best-Effort Multicast Algorithm

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (524 KB) |  | HTML iconHTML  

    Today's IP networks have seen a growing number of applications whose traffic are most efficiently transported using multicast forwarding service. In this paper, we present a scalable, sender-initiated, performance-driven, best-effort tree construction algorithm, which adapts to the changing network conditions. The algorithm does not use any unicast routing protocol. We demonstrate the operations and evaluate the performance of the algorithm using computer simulations. View full abstract»

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  • A Fault-Tolerant Best-Effort Multicast Algorithm

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (512 KB) |  | HTML iconHTML  

    This paper integrates into this base algorithm the fault tolerance capability. We present a protection-based and a restoration-based reroute algorithm which is executed by every node in the network, and an algorithm to compute the degree of tolerance. The algorithms do not use any unicast routing protocol. We demonstrate and verify the operations of the algorithms using computer simulations. View full abstract»

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  • Applications of the Fault-Tolerance Best-Effort Multicast Algorithm

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (498 KB) |  | HTML iconHTML  

    The papers [1][2] presented an adaptive best- effort tree construction algorithm with fault tolerance. In this paper, we present applications to [1] showing how to (1) build QoS trees and paths, (2) build fault-tolerant multi-source and single or multi-root trees, (3) build link-disjoint trees, (4) discover the tree topology, and (5) support multi-party conferencing. We demonstrate the operations of the algorithms using computer simulations. View full abstract»

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  • Realization of Broadband Constrained Partitioned Processor Weights by Solving Lower Dimension Unconstrained Optimization Problem

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB) |  | HTML iconHTML  

    A constrained partitioned processor is used to implement a broadband time domain antenna array system using a fixed main beam steered in the direction of the desired signal and a set of auxiliary beams to estimate the unwanted noise in the main beam. Weight forming the auxiliary beams are constrained to block the desired signal from the output of the section consisting these beams. This requires solving a constrained beamforming problem of LN dimension with an array of L elements and a tapped delay line filter of length N. This paper presents a technique to estimate LN dimensional weights of the auxiliary beamformer by solving (L - 1) dimensional unconstrained problem and thus produces a computationally efficient method. View full abstract»

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  • Optimization Scheduling for Optical Burst Switching Networks with Wavelength Conversion

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4542 KB) |  | HTML iconHTML  

    Optical Burst Switching (OBS) is a promising solution for the future Internet backbone. In OBS network a key issue is data channel scheduling. In this paper we propose a channel scheduling scheme to optimize channel utilization for OBS networks with wavelength conversion. The channel scheduling problem is mapped to a problem of finding k-colorable subgraph of weight interval graph. The problem is formulated as an integer linear programming problem, which is solvable in polynomial time. Simulation results show that both channel utilization and bit loss probability performance improve compared with existing scheduling schemes. View full abstract»

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  • The Implementation of IEEE1451 for e-Health

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4020 KB) |  | HTML iconHTML  

    We're approaching to the Ubiquitous age with development of the internet, recently. The standardization is going to progress in wireless communication. For example, IEEE 802.15.1, IEEE 802.15.4, IEEE 1451. We will refer to IEEE 1451. Attributes of IEEE 1451 are PnP and flexibility and so on. And there is a standard for a e-Health, HL7(Health level seven). HL7 accredited Standards Developing Organizations (SDOs) operating in the healthcare arena. Transducers, defined here as sensors or actuators, serve a wide variety of industry's needs, manufacturing, industrial control, and biomedicine are but a few. This paper we will explain HL7 and IEEE 1451 ,in briefly. The present time we will realize sensor networking for e- Health using IEEE 1451 standard. For example, in hospital, doctors use sensor. Because, for catch hold of patient's health. In brief, sensor is a STIM and server is a NCAP. So, we will get model for sensor-networking in hospital. We will explain NCAP and STIM more So, this paper will introduce implementation of the IEEE 1451.1 and IEEE 1451.2. And introduce IEEE1451 and HL7. So we will say that relation between IEEE1451 and HL7. View full abstract»

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  • Ad-hoc routing Protocol-based Mobile Network for E-healthcare

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1032 KB) |  | HTML iconHTML  

    AODV is one of the various routing protocol on ad-hoc networks. This paper analyzes information about the user who moves from among the multi techniques which composes the Ubiquitous environment, and proposes about the network configuration and management to execute Ubiquitous system. In this paper, we propose efficient method that has AOD Vprotocol advantage and the property of power efficiency and reliable data transmission in the hospital or home environment. Our proposed method uses the mobile nodes which have the sensor and the role and an operational process of each system configuration is described in this paper. View full abstract»

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