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Date 27-28 March 2006

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Displaying Results 1 - 25 of 104
  • 2006 IEEE Sarnoff Symposium

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  • [Copyright notice]

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  • Table of contents

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  • index-author

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  • Particle Swarm Optimization for Routing and Wavelength Assignment in Optical Networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (903 KB) |  | HTML iconHTML  

    In this paper, we demonstrate the use of particle swarm optimization (PSO) to obtain near-optimal solutions to the NP-complete routing and wavelength assignment (RWA) problem in optical networks. More specifically, our PSO algorithm solves the RWA problem to carry the given traffic demands so that the network wavelength requirement as well as the average path lengths for the traffic is minimized. We have developed a Java based network simulator that uses our PSO algorithm to do RWA and present results of our experiments on a variety of hand-crafted and real-world networks. We compare our results with well-known theoretical results for the lower bound on the number of required wavelengths and average path lengths, and show that we can achieve optimal results in some cases and near-optimal in others, thus demonstrating the usefulness of our PSO technique. To the best of our knowledge this is the first time PSO has been used to solve the RWA problem. View full abstract»

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  • On the Future of Optical Ring Networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1354 KB) |  | HTML iconHTML  

    Optical ring networks provide only limited and inefficient resilience and are poorly suited to sustain unpredictable changes and shifts in future traffic loads. In this paper, we examine the impact of link upgrades, link reconfigurations, and link additions on the resilience and ability to sustain unpredictable traffic of optical bidirectional rings. View full abstract»

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  • Load Balancing in All-Optical Overlaid-Star TDM Networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1136 KB) |  | HTML iconHTML  

    Load balancing is an effective solution to relieving network congestion and achieving good network performance. This paper investigates routing strategies for load balancing in all-optical overlaid-star TDM networks. A random routing strategy and a least-congested-path routing strategy are first presented, based on which a weighted-least-congested-path routing strategy is then proposed. The proposed strategy takes into account both load balancing and end-to-end delay in path selection, and thus can achieve better delay performance while maintaining the same blocking performance under low traffic load as compared with the other strategies. The performance of the routing strategies is evaluated through simulation results. View full abstract»

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  • A Heuristic Algorithm Based on Tabu Search for Routing and Wavelength Assignment in Multicast Multi-Wavelength Multi-Fiber Networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1401 KB) |  | HTML iconHTML  

    This paper proposes a heuristic algorithm based on tabu search for solving the problem of routing and wavelength assignment in multicast multi-fiber WDM networks using virtual light -tree (VLT) technique. The objective is to design an effective algorithm that can be applied to large network problems served as an alternative method to that based on Integer Linear Programming technique. The design outcomes measured in terms of the total capacity requirement of the proposed algorithm are evaluated and compared to that of ILP approach. Results on tested networks demonstrate that both techniques offer comparable design output, signifying the effectiveness of the proposed algorithm. View full abstract»

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  • Analysis of Nonlinear Phenomena for Optical Soliton Transmission in DWDM Systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1502 KB) |  | HTML iconHTML  

    The key feature of optical soliton transmission is the capability of pulses to maintain their shape even when transmitted over very long distance. However, the optical soliton technique in DWDM systems is difficult to use because of optical fiber nonlinearities. CPM leads to spectral broadening and FWM may result in significant crosstalk among the channels. Understanding the effects optical fiber nonlinearities is crucial in order to optimize system performance. In this study, the effects of optical fiber nonlinearities are evaluated in conjunction with various EDFA gain ratios in 16 channel and 32 channel optical soliton transmission systems. View full abstract»

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  • Performance Evaluation of WDM Fiber Optic Frequency Distribution Systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3284 KB) |  | HTML iconHTML  

    In this paper we evaluate the phase stability of an externally modulated 8.8 km analog wavelength division multiplexing (WDM) fiber optic frequency distribution link. The analysis of additive radio frequency (RF) phase noise with and without erbium doped fiber amplifier (EDFA) in the fiber optic link is the main objective of this work. RF phase noise is mainly investigated with power amplifier configuration for 1540, 1545, 1550, 1555, and 1560 nm wavelengths and for different gains of EDFA. View full abstract»

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  • Multi-Constrained Routing in Networks with Shared Risk Link Groups

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (299 KB) |  | HTML iconHTML  

    Diverse routing in networks with shared risk link groups (SRLGs) is an NP-complete problem in general. In this work, we study a multi-constrained routing problem in networks with SRLGs where a path between a source and a destination is determined such that both the path cost and the weight of SRLGs to which the links of the path belong are bounded. The path cost is measured as the sum of cost of links on the path while the weight of SRLGs is calculated as the sum of the weight of individual SRLGs along the path. The solution to this problem can be used to design algorithms that find a pair of low cost SRLG-diverse paths between a source and a destination. The multi-constrained routing problem is solved in two steps. First, an algorithm is devised that finds a least cost path in the network where the path cost is defined to be the combined cost of links and SRLG weights along the path. Second, an intelligent search algorithm that integrates the algorithm of the first step is designed to solve the multi-constrained routing problem to effectively find a path with the least total link cost while the total weight of the SRLGs on the path is bounded. The performances of the proposed algorithms are evaluated via extensive simulation and are compared with the solutions obtained by integer linear programming. View full abstract»

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  • Approximating Optimal Survivable Routing in WDM Optical Networks under a Scheduled Traffic Model

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB) |  | HTML iconHTML  

    Survivable service provisioning design has emerged as one of the most important issues in communication networks in recent years. In this work, we study the problem under a scheduled traffic model in wavelength convertible WDM optical mesh networks. In this model, a set of demands is given, and the setup time and teardown time of a demand are known in advance. We propose an efficient capacity provision matrix based algorithm that uses different demand scheduling policies to solve the problem effectively under the scheduled traffic model. The objective is to minimize the total number of wavelength-links used by working paths and protection paths of a given set of demands by maximally exploiting network resource reuse in both space and time while 100% restorability is guaranteed against any single failures. Our simulation results indicate that the proposed algorithm is very effective in terms of total network resources required and computational time used compared with Integer Linear Programming based methods proposed in our previous work. View full abstract»

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  • A WDM Banyan Switching Network for Multicast Optical Cross-Connects

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1938 KB) |  | HTML iconHTML  

    In this paper, we investigate the problem of designing a WDM switching network with multicast capability. We propose, for the first time, a WDM Banyan switching network that is capable of replicating input signals on "different" wavelengths. Wavelength conversion in the proposed Banyan network occurs between two predefined wavelengths, and hence, the conversion cost is reduced. The new Banyan network can be used to construct wide-sense and strict-sense nonblocking WDM Mmulticast optical cross connects (MC-OXCs). View full abstract»

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  • Comparison of Modulation Formats for 40-Gbit/s DWDM Optical Fiber Transmission Systems with 50-GHz Channel Spacing

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1378 KB) |  | HTML iconHTML  

    We compare Duobinary, RZ-DPSK, RZ-DQPSK modulation formats for long haul optical fiber transmission for 40-Gb/s DWDM systems with 50-GHz channel spacing by numerical simulation. View full abstract»

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  • An Availability-Based Link QoS Routing for Mobile Ad hoc Networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1437 KB) |  | HTML iconHTML  

    With more and more wireless devices being mobile, there is a constant challenge to provide reliable and high quality communication services among these devices. In this paper, we propose an availability-based link QoS (ABLQ) routing protocol for mobile ad hoc networks based on mobility prediction and link quality measurement, in addition to energy consumption analysis. The goal is to provide highly reliable and better communication links with energy-efficiency. The proposed routing algorithm has been verified by NS-2 simulations. The results have shown that ABLQ outperforms existing algorithms by guarantying minimal link breakages and thereby reducing the reconnection and retransmission overhead. It also reduces the average end-to-end delay for data transfer and enhances the lifetime of nodes by making energy-efficient routing decisions. View full abstract»

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  • An Overlay Framework for QoS Management in Mobile Ad Hoc Networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2850 KB) |  | HTML iconHTML  

    For a delay-sensitive application, it is important to maintain the probability that the end-to-end delay is greater than a certain threshold as small as possible. In order to satisfy such a constraint, a shortest path in terms of hop-count is generally chosen. However, hop-count is a very crude measure of the path latency and also if the shortest path breaks before the end of the transmission, it is likely that the delay constraint will not be met. In this paper, we propose an overlay framework that considers both delay and mobility to satisfy the QoS requirements of the delay-sensitive application. Also, we propose network and application layer QoS and mobility management schemes which utilize both reactive and proactive methods. View full abstract»

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  • Peer-to-peer Wireless Sensor Network Data Acquisition System with Pipelined Time Division Scheduling

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1827 KB) |  | HTML iconHTML  

    this paper, we introduce a peer-to-peer sensor network (P2PWSNDAS) architecture with pipelined time division scheduling for sensor data acquisition from an ad hoc wireless sensor network (WSN). P2PWSNDAS takes a service-oriented, data-centric view of the deployed WSN. The wireless sensors that constitute the WSN measure physical attributes of the environment they are deployed in such as temperature, pressure, vibration, toxic chemical, biological agents, etc. In our architecture, we assume that the entire WSN can be divided into sets of 'sensor-clusters'. Each cluster has a gateway or base station that aggregates data from its sensor cluster. The gateways themselves which constitute the middleware layer between the WSN and end point clients are designed to form an IP-based distributed peer-to-peer (P2P) overlay network. Clients query the gateways for real-time sensor data via a publish/subscribe/notify paradigm implemented at the gateways, and they can also concurrently receive notifications on alarms/events of interest. Another contribution we report in this paper is a Pipelined Time- division Model (PTM) scheduling for continuous energy-aware MAC-layer communication between a gateway and its sensors. Our PTM scheduling algorithm is particularly targeted towards wireless sensors such as the MICA2 series [4] that have multichannel radio transceivers. View full abstract»

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  • Potential for Intra-Vehicle Wireless Automotive Sensor Networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2341 KB) |  | HTML iconHTML  

    We propose using a wireless network to facilitate communications between sensors/switches and control units located within a vehicle. In a typical modern vehicle, the most demanding sensor will require a latency of approximately less than 1 msec with throughput of 12 kbps. Further, the network will need to support about 15 sensors with this requirement. The least demanding sensor will require a latency of approximately 50 msec with data throughput rate of 5 bps and will need to support about 20 of these types of devices. Initial part of this paper gives an overview of the issues spanning several layers of the protocol stack. Then, we focus on the Medium access control (MAC) layer and derive necessary design parameters based on given network requirements. We evaluate the IEEE 802.15.4 standard with respect to its suitability for use in a prospective intra-vehicle wireless sensor network. View full abstract»

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  • Policy-Based Adaptive Routing in Mobile Ad Hoc Wireless Networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1642 KB) |  | HTML iconHTML  

    This paper investigates policy-based adaptive routing for mobile ad hoc networks (MANET's), in which routing metric, routing algorithm parameters and/or protocol selection can be controlled in response to observed performance and external service needs. We propose an adaptive routing framework which allows introduction of adjustable parameters and programmable routing modules. Control information is disseminated through the network to exchange state variables, and a global distributed policy manager is responsible for the adaptive operations at nodes of the network. The proposed architecture can support two types of adaptive mechanisms: the first involves switched selection between a set of routing protocols options or metrics, while the second is based on an integrated routing algorithm which incorporates adaptation of key network state parameters such as link speed or congestion. Example algorithms and simulation results are given, which show that adaptive routing help achieve the desired system performance under the dynamically changing network conditions. View full abstract»

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  • MMSE Noise Power and SNR Estimation for OFDM Systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (973 KB) |  | HTML iconHTML  

    This paper proposes a minimum mean-square error (MMSE) filtering technique to estimate the noise power that takes into account the variation of the noise statistics across the orthogonal frequency division multiplexing (OFDM) sub-carrier index as well as across OFDM symbols. The proposed method provides many local estimates that allow tracking of the variation of the noise statistics in frequency and time. The MMSE filter coefficients are obtained from the mean-squared-error (MSE) expression, which can be calculated using the noise statistics. Evaluation of the performance with computer simulations shows that the proposed method tracks the local statistics of the noise more efficiently than conventional methods. View full abstract»

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  • Self-Protection of Turbo- and LDPC-Coded OFDM Systems against Non-Stationary Disturbances

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1882 KB) |  | HTML iconHTML  

    This paper presents a method to protect turbo- and low density parity check (LDPC)-coded OFDM systems against non-stationary disturbances without using external codes. The technique does not alter the structure of the original code and the constellation mapper/demapper, but requires the insertion of a so-called self-protection unit (SPU) between the coding and constellation mapping units. The SPU enhances the burst-error-correction capabilities of turbo and LDPC codes by combining erasure-decoding, subframing (i.e., reordering the coded data into subframes), and the optional use of subframe interleaving to spread error bursts. Self-protected systems exhibit a reduced latency and storage capacity compared to classical channel interleaving schemes with similar protection level. View full abstract»

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  • Adjacent Frequency Coding Technique for Decreasing MB-OFDM UWB Interference to Other Radio Services

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1094 KB) |  | HTML iconHTML  

    Multiband OFDM (MB-OFDM) ultrawideband radio will have to coexist with numerous narrowband radio services that operate over the 3.1 - 10.6 GHz band. In order to coexist with other radio systems without becoming a harmful source of interference, MB-OFDM radio designers are actively developing methods to protect those portions of the band that are being used by other, actively transmitting, radios. This requires the ability to notch segments of the transmitted spectrum so that the impact to other services is minimal. In this paper, we present the Adjacent Frequency Coding method, which uses weighted sub- carrier pairs to shape the MB-OFDM spectrum so that it has a steeper roll-off, and thus a better ability to notch. This technique, which increases the achievable notch depth by ~ 10 dB when compared to simple tone dropping (i.e. sub-carrier nulling without spectral shaping), requires only a modest modification to the current MB-OFDM PHY specification. View full abstract»

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  • An Analog/Mixed-Signal FFT Processor for Wideband OFDM Systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1070 KB) |  | HTML iconHTML  

    An analog/mixed-signal (AMS) Fourier transform circuit topology is presented that has the potential to significantly reduce power consumption in future broad-band OFDM systems. The topology would replace the flash based analog-to-digital converter (ADC) and the digital FFT core in current OFDM systems with an alternative analog multiplier-based converter. System simulations are presented to demonstrate the feasibility of the proposed system. The new topology is shown to significantly reduce power consumption of the ADC/FFT block. View full abstract»

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  • Cognitive UWB-OFDM: Combining Ultrawideband with Opportunistic Spectrum Usage

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1002 KB) |  | HTML iconHTML  

    In a continuously expanding wireless world, the number of radio systems increases every day, and efficient spectrum usage becomes a more significant requirement. Ultrawideband (UWB) and cognitive radio are two recent and exciting technologies that offer a new approach to the spectrum usage. The main objective of this paper is to combine these two technologies. The strength of orthogonal frequency division multiplexing (OFDM) based UWB in co-existing with licensed systems is investigated. The opportunity concept is defined, and the requirements of the opportunistic spectrum usage are explained. It is proposed to take the UWB-OFDM from the current underlay implementation, and evolve it to a combined underlay and opportunistic spectrum usage technology, leading to cognitive UWB-OFDM. This way, we aim at making UWB more competitive in the wireless market with extended range, higher capacity, better performance, and a wide variety of applications. View full abstract»

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  • Technological Scaling and Impact on UWB Configurable RF Signal Source

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (521 KB) |  | HTML iconHTML  

    The coexistence of second and third generation wireless system requires multi-mode, multi-band and multi-standard mobile communication systems, therefore, requiring a configurable RF signal source (VCO) that may replace several narrow band VCO modules by a single low noise ultrawideband (UWB) adaptable RF signal source. The performance of the wireless communication systems strongly depends on the speed of devices, and technological scaling has driven this momentum towards achieving faster speed and high level of integration. This paper investigates the impact of device scaling on phase noise of the UWB (2-8GHz) configurable coupled N-Push voltage controlled oscillator (VCO) in SiGe HBT, which has recently emerged as a strong contender for RF and mixed signal applications. View full abstract»

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