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Wireless and Optical Communications Conference (WOCC), 2010 19th Annual

Date 14-15 May 2010

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Displaying Results 1 - 25 of 91
  • [Copyright notice]

    Publication Year: 2010 , Page(s): 1
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    Freely Available from IEEE
  • [Front cover]

    Publication Year: 2010 , Page(s): c1
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    Freely Available from IEEE
  • Spectrum sensing and data transmission tradeoff in cognitive radio networks

    Publication Year: 2010 , Page(s): 1 - 5
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (402 KB) |  | HTML iconHTML  

    In cognitive radio networks, a cognitive source node typically requires two essential phases to complete a cognitive transmission process: the phase of spectrum sensing with a certain time duration to detect a spectrum hole (thus also referred to as spectrum hole detection phase) and the phase of data transmission through the detected spectrum hole. In this paper, we focus on the analysis of cognitive transmissions by jointly considering the two phases. An exact closed-form expression of an overall outage probability that accounts for both the probability of no spectrum hole detected and the probability of a channel outage is derived for cognitive transmissions. Based on the derived overall outage probability, we investigate the spectrum hole utilization efficiency, which is used to quantify the percentage of spectrum holes utilized by the cognitive source for its successful data transmission. Numerical results show that there is a tradeoff in determining the time durations for hole detection and data transmission phases in order to maximize the spectrum hole utilization efficiency. View full abstract»

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  • Priority-aware optical shared protection coupled with mutation probability

    Publication Year: 2010 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB) |  | HTML iconHTML  

    The next big challenge for optical network operators is to meet the diverse availability requirements of the various subscribed services through the adoption of appropriate protection strategies. One promising scheme that has been proposed in the open literature and that is presenting itself as a potential approach to dealing with this challenge is the priority-aware protection scheme. However, the priority-aware protection strategy suffers from a major limitation as it privileges the failed high priority connections taking no account of the failed low priority ones. As such, this paper proposes to combine priority-aware shared protection with a parameter called mutation probability thus giving birth to a more effective protection strategy. The mutation probability parameter expresses the likelihood that a low-priority connection be promoted temporarily to a higher priority level during its recovery. The proposed mutation-based protection strategy therefore allows optical operators to improve the availability of their low-priority clients without violating the availability requirements of their high-priority ones. Performance of this novel protection strategy is analyzed in this paper by precisely calculating the connection unavailability that results from its deployment. A computational framework is proposed in this regard to highlight the merit that the mutation-based protection strategy has over the existing priority-aware protection scheme. View full abstract»

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  • A Location aided Energy-Efficient Routing protocol for Ad hoc Networks

    Publication Year: 2010 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (443 KB) |  | HTML iconHTML  

    Routing in Ad hoc Networks remains a challenging problem given the constrained energy, limited bandwidth, and large scale. Many protocols such as AODV and DSR have been proposed; however, they are not energy-efficient without using nodes' location information. In this paper, we propose a Location aided Energy-Efficient Routing protocol (LEER), which is based on nodes' location information. The main aim of this protocol is to reduce the energy consumption and prolong the lifetime of the networks. The simulation results show this protocol achieves excellent routing performance, and the average energy consumption of LEER is less than AODV and DSR. View full abstract»

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  • WHAT: A novel routing metric for multi-hop cognitive wireless networks

    Publication Year: 2010 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1024 KB) |  | HTML iconHTML  

    In this paper, we study how to select a high performance end-to-end path in multi-hop cognitive wireless networks. Due to the time-varying spectrums and undetermined activity of primary users, path selection in cognitive wireless networks is much harder than that of traditional wireless networks. To attack this problem, we propose a novel routing metric, called WHAT (Weighted Hop, spectrum-Awareness, and sTability), which takes not only opportunistic spectrum access into account, but also path stability. WHAT synthesizes channel switching frequency, usage of licensed channels, and length of path together to evaluate the overall quality of an end-to-end path. In addition, different from some existing routing metrics, WHAT has two key properties of routing metric: isotonicity and monotonicity. The theoretical analysis and simulation results show that WHAT can improve the network performance (TCP throughput) profoundly and ensure routing protocols operate correctly. View full abstract»

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  • 40 Gbps ultra long span unrepeatered system with large dispersion tolerance

    Publication Year: 2010 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (955 KB) |  | HTML iconHTML  

    A 40 Gbps ultra long span unrepeatered system is proposed. In the scheme, total effective capacity (40 Gbps) of the system is inverse multiplexed into 12 channels by digital signal processing. The bit rate of each channel is 10 Gbps. Principle of operation is clarified and experiment is performed without dispersion compensation. Results indicate that the proposed system can tolerate distortion caused by chromatic dispersion effectively after long distance transmission. The proposed system is applicable for ultra long single span transmission. View full abstract»

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  • A novel architecture of reconfigurable WDM/TDM-PON

    Publication Year: 2010 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (383 KB) |  | HTML iconHTML  

    A novel architecture of hybrid WDM/TDM-PON based on a dual-fiber ring with access-tree topology is proposed. This system can enable the network operator to easily and flexibly reconfigure wavelength resources in the light of dynamical traffic load and bandwidth requirement by using a ROADM based on WB technology at each RN. Simultaneously, this scheme is able to improve reconfiguration of network in response to the failure of some fiber by utilizing a backup feeder-fiber ring and some optical switches. View full abstract»

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  • Adaptive spectrally precoded OFDM with cyclic prefix

    Publication Year: 2010 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (361 KB) |  | HTML iconHTML  

    Adaptive spectrally precoded orthogonal frequency-division multiplexing (ASP-OFDM) is a recently proposed adaptive modulation scheme to significantly improve the system throughput in adaptive OFDM applications. In this paper, new spectral precoder is proposed for ASP-OFDM with cyclic prefix (ASP-CP-OFDM) on the flat fading channel. By jointly adapting the precoding order for spectral precoder and the component modulation, the proposed ASP-CP-OFDM is shown to outperform adaptive nonprecoded OFDM and previously designed ASPCP-OFDM significantly in average spectral efficiency. View full abstract»

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  • The study of wavelet de-noising in multi-span nonlinear intensity-modulated fiber communication systems

    Publication Year: 2010 , Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (285 KB) |  | HTML iconHTML  

    In this work, wavelet de-noising with several different types of wavelets such as db4, coif4 and dmey wavelets was applied at the end of the multi-span intensity-modulated fiber communication systems. The results of numerical simulations carried out in different fiber links demonstrated that the wavelet de-noising method could remove the random amplitude fluctuation and pulse breaking induced by the interaction of ASE noise and fiber dispersion and nonlinearity. The normalized energy deviation (NED) of the signal without and with de-noising in dispersion compensation fiber link were plotted to show the effectiveness of the wavelet de-noising in the fiber-optic communication systems and wavelet de-noising with demy wavelet can achieve better result than with other type wavelet. View full abstract»

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  • Fast genetic algorithm for bits allocation in OFDM based cognitive radio systems

    Publication Year: 2010 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (112 KB) |  | HTML iconHTML  

    In this paper, we propose a fast genetic algorithm (FGA) for bits allocation in OFDM based cognitive radio systems. The bits allocation in OFDM subchannels is modeled as a binary sequences search problem, which is NP-Hard. First, the bits with the least cost in each subchannel are formulated as a possible solution with a predefined probability. Then a genetic-like algorithm is used to search the current local optima, which have the most allocated bits. The algorithm terminates until the total power is consumed or the mutual interference is over-the-threshold. Simulation results show that the performance of FGA is close to the optimal solution obtained by commercial software. View full abstract»

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  • Analysis of PCE-based wavelength assignment schemes in wavelength switched optical networks

    Publication Year: 2010 , Page(s): 1 - 3
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB) |  | HTML iconHTML  

    As a key problem in wavelength switched optical networks (WSON) in which wavelengths are the most important resources, routing and wavelength assignment (RWA) problem has been researched extensively. Due to the advantages of path computation in multi-layer and multi-domain networks, especially in multi-constraints scenarios, path computation element (PCE) has been introduced into WSON, which provides a better approach to the solution of RWA problem in WSON. A novel PCE-based wavelength assignment scheme CRWA-PQ is proposed in wavelength switched optical networks (WSON), and compared with several other schemes by simulation using OMNeT++. View full abstract»

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  • Study on partial-transit Inter-domain routing over the TEIN2 backbone

    Publication Year: 2010 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1558 KB) |  | HTML iconHTML  

    Based on the transit behavior, we categorize the Internet backbones into two types, global-transit backbone and partial-transit backbone. Partial-transit backbone represents the majority of R&E (Research & Education) backbones, which is liable to a number of inter-domain routing problems due to its particular characteristics. Through two routing cases in TEIN2 backbone, a typical R&E partial-transit backbone, we point out the main problems in partial-transit inter-domain routing, most of which are all relevant to inter-domain routing policy. After studying the related work on inter-domain routing policy, we propose a Distributed BGP Policy Simulation and Evaluation System, BGP-Grid. This solution is mainly out of consideration for operation and network engineering of TEIN2 backbone, which is proved to be practicable and effective during the three years' TEIN2 operation. View full abstract»

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  • Cooperative and distributed spectrum sharing in dynamic spectrum pooling networks

    Publication Year: 2010 , Page(s): 1 - 5
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (338 KB) |  | HTML iconHTML  

    In dynamic spectrum access systems, such as cognitive radio networks, spectrum pooling is one of the approaches to manage the available spectrum bands from different licensed networks. Based on the concept of spectrum pooling, most previous work focuses on the system architecture and the design of flexible access algorithms and schemes. In this paper, a cooperative and distributed scheme for dynamic internetwork spectrum sharing among multiple networks is proposed, taking into account the spectrum access price and the spectrum efficiency. Specifically, the spectrum sharing problem is formulated as a restless bandits model-based optimization system, which dramatically reduces the complexity of the scheme by allowing the spectrum allocation scheme to be simply select the network with the lowest index. Extensive simulation results illustrate that the proposed scheme improves the performance significantly compared to the existing scheme that ignores the distributed and cooperative spectrum sharing. View full abstract»

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  • Threshold-based opportunistic routing protocol in multi-hop wireless networks

    Publication Year: 2010 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (502 KB) |  | HTML iconHTML  

    Unlike traditional unicast routing where a transmitting node needs to specify its single next-hop forwarder in a multi-hop wireless networks in an a priori manner, Opportunistic Routing allows multiple potential next-hop forwarders to be selected. Any selected node may forwards the packet towards the destination if it can decode the packet correctly. Existing opportunistic routing protocols tend to limit the size of the forwarding set for each transmitting node due to the communication overheads required to suppress unnecessary packet duplicates generated by multiple eligible next-hop forwarders. As such, they fail to capitalize on the key advantage of opportunistic routing, namely, the ability to utilize a large number of long but unreliable wireless links in progressing towards the destination. In this paper, we propose TORP, the Threshold-based Opportunistic Routing Protocol, which applies a novel threshold-based forwarding technique to reduce the coordination requirements between multiple potential next-hop nodes. This in turn, enables TORP to exploit the advantage of using numerous distant downstream nodes as next-hop forwarders. Simulation results show significant improvements in the end-to-end delay and total traffic load generated by TORP over unicast routing. Compared with the state-of-the-art ExOR protocol, TORP reduces the average end-to-end delays by 25-40% under typical network configurations and has the advantage of being more amenable to a fully-distributed implementation. View full abstract»

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  • Safety guaranteed smooth playout algorithm for wireless video streaming

    Publication Year: 2010 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (329 KB) |  | HTML iconHTML  

    Recently smooth adaptive media playout (SAMP) was suggested to deal with the visual quality degradation problem caused by the fluctuation of playout speed in conventional AMP. However, while encountering the burst packet losses, it still had a potential buffer outage risk if buffer level was not safe enough. In this paper, a safety guaranteed SAMP (SG SAMP) algorithm is proposed to deal with the above hazard. Whenever the current buffer level deviates from the predefined safe area, the linear playout adjustment order is triggered to maintain the buffer safety. The simulation results have shown that SG SAMP outperforms SAMP in reducing the buffer outage probability and provides smooth and reliable playback, especially in wireless video streaming. The playout adjustment number and the frame loss number are both about 30% less. View full abstract»

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  • A modified constellation extension scheme with low complexity for PAPR reduction in OFDM systems

    Publication Year: 2010 , Page(s): 1 - 4
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB) |  | HTML iconHTML  

    High peak-to-average power ratio (PAPR) is one major drawback of orthogonal frequency division multiplexing (OFDM) systems. Recently, the constellation extended scheme (CES) is an active technique for reducing PAPR of OFDM signals. However, this approach needs high computational load and more inverse Fast Fourier transform (IFFT) operations for finding the transmitted signal with minimum PAPR out. Therefore, this paper proposes a modified CES with lower computational load and IFFT operations than the CES in a 16-QAM OFDM system. Our proposed method, which combines the CES with the partial transmit sequences (PTS) technique, is also called CES-PTS. When compared to PTS techniques, our proposed method has no need to transmit side information in the transmitter. View full abstract»

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  • An optimal transmission scheme for two-way relaying networks with power constraint

    Publication Year: 2010 , Page(s): 1 - 4
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (202 KB) |  | HTML iconHTML  

    Cooperative communication is an efficient method to combat wireless channel fading and to increase system throughput in future board communication. Through physical layer networking coding(PNC)modulation, two-way relaying has been shown to improve the network capacity significantly. However for power-constraints application, the performance of two-way relaying is actually inferior to one-way relaying at low SNR environment. To solve the issue, the scenario of three nodes cooperative communication is considered in this paper.Assuming that perfect channel knowledge is available at the relay node, an optimal transmission scheme for two-way relaying communication is proposed. The transmission scheme, which is based on instantaneous channel link quality, is selected to offer maximum system capacity. The efficiency of the proposed solution is demonstrated by both analytical performance and simulations. View full abstract»

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  • MAC protocol classification in a cognitive radio network

    Publication Year: 2010 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (269 KB) |  | HTML iconHTML  

    Most media access control (MAC) protocols can be classified as contention based or controlled based according to their transmission mechanisms. To classify contention based or control based MAC protocols in an unknown primary network, we choose received power mean and variance as two features for support vector machines (SVMs) in a machine learning based algorithm. The data consisting of these two features are collected from two primary network models based on time division multiple access (control based) and slotted Aloha (contention based), respectively. In the training process, data along with their identification class labels (say, 1 denotes time division multiple access, and -1 stands for slotted Aloha) are used to train the SVMs. After training, contention or control based MAC protocols can be effectively determined by the trained SVMs embedded in a cognitive radio terminal of a secondary network. View full abstract»

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  • An improved location algorithm for RFID system in NLOS environment

    Publication Year: 2010 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (482 KB) |  | HTML iconHTML  

    A novel location algorithm based on geolocation algorithm and LANDMARC algorithm is proposed to improve the location accuracy of Radio Frequency Identification (RFID) system in non-line-of-sight (NLOS) environment. We compare this algorithm with the existing LANDMARC algorithm via two metrics: the mean location error and cumulative location error distribution in line-of-sight (LOS) and NLOS environments, respectively. Numerical simulation results show that the proposed algorithm is very simple, and it gives higher location accuracy in NLOS environment with little performance degradation compared with in LOS environment. View full abstract»

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  • Performance evaluation of ad-hoc routing protocols in underwater acoustic sensor networks

    Publication Year: 2010 , Page(s): 1 - 6
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (520 KB) |  | HTML iconHTML  

    Underwater acoustic sensor networks (UWASNs) is an emerging technology, comprising of sensor nodes and unattended automated vehicles (AUVs), all working in a collaboration to sense various phenomenon, process digital information, store processed data and communicate among each other and base stations. Acoustic propagation in water is characterized by high and variable delays, fading effect, Doppler spread and multi path which in turn lead to a limited bandwidth and high error rates. Also, battery life and storage capacity of nodes is limited. So there is a need of suitable routing protocol that takes all these limitations into consideration and makes communication in underwater networks viable. This is the first attempt to analyze the performance of ad-hoc routing protocols in underwater acoustic network environment. We used performance metrics like packet delivery ratio, average end-to-end delay, throughput, routing overhead and energy consumption of the sensor nodes. AODV, DSDV, DSR and OLSR are compared for their performance at different traffic conditions, number of nodes and depths. By analyzing our simulation results, we found that among the discussed protocols, AODV may be used for denser networks but with less traffic and DSDV is suitable for higher traffic conditions with optimal number of nodes. View full abstract»

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  • Throughput analysis of CSMA protocol with Exponential Backoff

    Publication Year: 2010 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (411 KB) |  | HTML iconHTML  

    This paper studies the performance of Non-persistent CSMA protocols using K-Exponential Backoff collision resolution algorithms. We model it as a multi-queue single-server system with infinite buffer size and consider the service time distribution of Head-of-line packets as a Markov Chain to get the network throughput as well as the stability. The stable region of retransmission factor q is illustrated in examples of Exponential Backoff (K=∞). For throughput stability, we show the stabilized throughput can be obtained in networks even for infinite nodes. View full abstract»

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  • Investigation on the Wavelength Division Multiplexing optical thin-film filter

    Publication Year: 2010 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (127 KB) |  | HTML iconHTML  

    Currently, WDM thin-film filter has become one of the hottest areas in optical communication. In this research, the structure of parallel plate thin-film filter and wedge thin-film filter are designed and transmittance curve is simulated. Then samples of thin-film filter are tested and the performances are analyzed. View full abstract»

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  • Nonblocking multicast Clos networks

    Publication Year: 2010 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB) |  | HTML iconHTML  

    This paper studies the necessary and sufficient nonblocking conditions for multicast Clos network or v(m, n1, r1, n2, r2) network, wherein there are r1/r2 switch modules at first/third stage, n1 input/n2 output ports on each first/third stage switch module, and m central stage modules. We prove that given constant n1, n2, if r1 ≥ L = n2 ((n2-1m)-1)+1, r2 ≥ n1n2(n2L), m ≥ n1n2 is a necessary and sufficient nonblocking condition. Analogy to point-to-point Clos network, this result is independent of r1,r2 and improves on the current best sufficient condition at the given region. We also present a wide-sense nonblocking routing algorithm for satisfying each input multicast call. View full abstract»

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  • Multimode fiber bandwidth increase by means of spatial light filtration

    Publication Year: 2010 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (426 KB) |  | HTML iconHTML  

    The paper investigates the influence of the amplitude spatial filtering of the launched light beam on the base-band width of MM fiber frequency response. The filter is located on the confocal plane of an 4f imager. It is shown both theoretically and experimentally that a substantial increase of 3 dB base-band frequency is possible with only moderate filtration losses. View full abstract»

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