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Communications and Networking in China, 2006. ChinaCom '06. First International Conference on

Date 25-27 Oct. 2006

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Displaying Results 1 - 25 of 288
  • Partial Pre-Deflection Scheme with Least Hop First Routing for Optical Burst Switching Networks under Self-Similar Traffic

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5648 KB) |  | HTML iconHTML  

    A new scheme for optical burst switching (OBS) networks under self-similar traffic is proposed in this paper. Self-similar traffic is classified into two types of payload by partial pre-deflection edge node router, and the two types of payload are transferred using different routing algorithms - least hop first routing and shortest path first routing respectively, in order to properly utilize network resources and avoid burst contention at the core node switch. Simulation results indicate that the new scheme performs better than fixed routing and alternative routing for OBS networks under self-similar traffic. Furthermore, the implement of this scheme is feasible and easy, which makes OBS technology more applicable in network engineering (NE). View full abstract»

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  • Pilot Design and Channel Estimation in MIMO-OFDM System with Two Transmit Antennas

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4971 KB) |  | HTML iconHTML  

    A novel pilot design scheme and simple channel estimation algorithm for an orthogonal frequency-division multiplexing (OFDM) system with two transmit antennas is proposed in this paper. The proposed algorithm takes advantage of the essence of SFBC to reduce the interantenna interference. In the proposed channel estimation scheme, the pilot sequences for two transmit antennas are carefully designed to reduce the interantenna interference, which will lead to more accurate channel estimation. And the interantenna interference at the receiver is used to further improve the performance of the channel estimation. The mean square error (MSE) for the proposed algorithm is formulated and the computational complexity is also analyzed. Computer simulations are conducted to verify the effectiveness of the algorithm. The simulation results show that the MSE accords with theoretical analysis and the loss in BER performance due to the proposed channel estimation are negligible compared to that with perfect channel state information (CSI) case. View full abstract»

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  • Using MRUL to Improve Network Fairness

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (6145 KB) |  | HTML iconHTML  

    Internet routers generally see packets from a fast flow more often than a slow flow. This suggests that network fairness may be improved without per-flow information. In this paper, we propose a scheme using most recently used list (MRUL) - a list storing statistics of limited active flows that sorted in most recently seen first mode - to improve the fairness of RED. Based on the list, our proposed scheme jointly considers the identification and punish of the fast and unresponsive fast flows, and the protection of slow flows. Its performance improvements are demonstrated with extensive simulations. Different from the previous proposals, the complexity of our proposed scheme is proportional to the size of the MRUL list but not coupled with the queue buffer size or the number of active flows, so it is scalable and suitable for various routers. View full abstract»

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  • Analysis of Switching Control Channels in Ason

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4128 KB) |  | HTML iconHTML  

    The introduction of control plane in ASON enables optical network intellective for the first time. As the channel to transfer message in control plane, the reliability of control channel significantly influences the performance of network. In traditional mechanism, control node should report fault to manager when control channel is down. In this paper, a new method of switching control channel is proposed and the process of switching among different modes of control channel is mainly focused on. Simulation results validate that the performance of network could be improved greatly by switching among control channels, the shorter switching time can lead to lower blocking probability. View full abstract»

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  • Traffic Splitting over ECMPs using ACC Scheme

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3503 KB) |  | HTML iconHTML  

    In order to reduce network congestion, when equal-cost-multi-paths (ECMPs) are between a forwarding node and a destination subnet, traffic should be balanced among ECMPs and packets of the same TCP flow should reach destination host in the same order. An algorithm called ARC-based caching with counting (ACC) is proposed. Packet length differentiation is considered to achieve load balance. UDP packets are only concerned to achieve load balance. Furthermore, flow access recency and frequency are considered when redirecting a flow to a new path. Simulation shows that when delay differentiation among ECMPs is not significant, storage requirement is small, only one cycle is needed for each cache lookup, load balance is near optimal, and only 1% of packets are out of order. View full abstract»

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  • Grouped Interleave-Division Multiple Access

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4876 KB) |  | HTML iconHTML  

    Recently, a new multiple access scheme called interleave-division multiple access (IDMA) has attracted much attention, in which interleaves are used as the only means for user separation. It has been shown that the IDMA can achieve near single user performance in multi-user environment with very low receiver complexity. In this paper, active users are arranged into several groups to form a new scheme called grouped-IDMA, where each group of users is characterized by an orthogonal code. By employing group-specific orthogonal spreading code for group separation, grouped-IDMA inherits the advantages of IDMA and orthogonal CDMA. Our analysis and simulation results show that the new scheme outperforms IDMA when user number is relatively large, and the multiple access interference (MAI) can be reduced in a more efficient way. In addition, the group size, an important parameter to the proposed scheme, is also discussed in order to achieve optimal performance. View full abstract»

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  • Combined Power and Rate Control for Integrated Voice and Data Transmission Systems

    Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2061 KB)  

    In this paper, two combined power and rate control (CPRC) algorithms, without-priority CPRC and priority-based CPRC, are proposed for the uplink of a cellular system integrated constant bit rate (CBR) voice and variable bit rate (VBR) data transmission. The CBR users and the VBR users are treated equally when assigning power and rate by the without-priority CPRC algorithm; while the CBR users are given higher priority by the priority-based CPRC algorithm. Simulation results demonstrate that the proposed algorithms can provide better performance than SPC (selective power control) algorithm proposed by S.-L.Kim. Comparing with the without-priority CPRC, the priority-based CPRC can provide lower outage probability for CBR users and less transmission power at the cost of throughput of VBR users under heavy system load. View full abstract»

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  • Multicast in Splitter-Sharing Optical Network

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3177 KB) |  | HTML iconHTML  

    In optical multicast, because of the high cost and complex architecture of multicast capable (MC) node, splitter-sharing switch structure is introduced. To accommodate to this structure, a multicast routing algorithm in splitter-sharing optical network and a changing link weight policy to balance traffic throughput are proposed. At the same time, by extending RSVP and OSPF, an optical multicast protocol mechanism is provided. Simulations in NSFNET show when the number of splitters is 25% of that demanded by traditional MC nodes, the performance has been close to the ideal circumstance. Using changing link weight can improve the performance fairly but has a longer setup time. View full abstract»

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  • User Selection and Resource Allocation for Multi-User MIMO-OFDM Systems with Downlink Beamforming

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4815 KB) |  | HTML iconHTML  

    In this paper, a multi-user MIMO-OFDM system with downlink beamforming technique is considered. We aim at minimizing the total transmission power while fulfilling each user's data rate and bit error rate (BER) requirement. This problem is formulated as a linear optimization problem in our paper. Since the optimal solution obtained from integer programming (IP) approach can hardly be implemented due to its high computational complexity, we present a heuristic user selection and resource allocation algorithm. Simulation results show that compared with existing SDMA-OFDM systems with or without resource allocation, our algorithm achieves significant performance improvement. The performance of the proposed heuristic algorithm is very close to that of the optimal solution. View full abstract»

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  • Distributed File Sharing: Network Coding Meets Compressed Sensing

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5735 KB) |  | HTML iconHTML  

    In a peer-to-peer file distribution network, a large file is split into blocks residing in multiple storage locations. A peer node tries to retrieve the original file by downloading blocks from randomly chosen peers. We compare the performance of four storage strategies: uncoded, erasure coding, random linear coding, and random linear coding over coded blocks. We show that, in principle, random linear coding makes a better tradeoff between the storage requirement and decoding complexity. However, the sparsity of the file blocks is not fully exploited by random linear combinations of all original blocks. Motivated by the recent results from compressed sensing, we study the design tradeoff in random linear coding over coded blocks and propose an efficient decoding algorithm based on basis pursuit. We show that the minimum number of storage locations that a peer note has to connect to reconstruct the entire file with high probability can be significantly smaller than the total number of blocks that the file is broken into View full abstract»

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  • A Novel OBS-Based Grid Architecture with Dual-Link-Server Model

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB) |  | HTML iconHTML  

    In this letter, we proposed a novel efficient infrastructure for grid based on "dual-link-server" optical burst switching (OBS) network to improve the performance of burst contention resolution scheme. The functional block required to support grid services is identified as one uniform grid network interface. The details of associated challenges in terms of functionality and technology were discussed and solutions were obtained. Dual-link-server model is used to solve the collision problem. The numerical simulation was performed to evaluate the performance of the proposed scheme. Techno-economic analysis results show that "dual-link-server" architecture for OBS grid is efficient and cost-effective. View full abstract»

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  • A New Scheme for Constructing High Code Efficiency LS ZCW Multiple Access Codes

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3675 KB) |  | HTML iconHTML  

    New zero correlation window (ZCW) LS (loosely synchronous) codes derived from basic LS codes are constructed. A general scheme for generating these codes is also discussed. It is showed mathematically that these new codes have a uniform ZCW for both aperiodic auto-correlation function (ACF) and cross-correlation function (CCF) within one group. Moreover, the minimum ZCW among different groups is the same as that of basic LS codes. The number of these new codes is more than the basic LS codes, and code efficiency can be greatly enhanced. Finally, the computer simulations verify the validity of new LS codes. View full abstract»

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  • Sequences with Three no Hit Zones and their Applications in Time-Frequency Hopping Systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4276 KB) |  | HTML iconHTML  

    Based on the idea of no hit zone (NHZ) in frequency hopping (FH) system, new sequences with three no hit zones (T-NHZ) in time-frequency hopping (TFH) systems are presented. With the correlation functions of the T-NHZ in the time-frequency (TF), the proposed T-NHZ sequences can be directly employed in time-frequency hopping code division multiple access (TFH-CDMA) communication systems to reduce or eliminate multipath interference. View full abstract»

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  • Provisioning of Survivable Multicast Sessions Against Single Failures in Sparse-Splitting Optical WDM Mesh Networks

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4961 KB) |  | HTML iconHTML  

    Recently, many heuristic algorithms have been put forward for protecting the multicast session against any single link failure in a WDM mesh network. But for the same session, the strategy is same. For the first time, in this paper we propose a novel technique to blend two classes of strategies in a hybrid recovery approach. Using this technique the multicast session is divided into two parts through a parameter called threshold. One is critical tree, the other is uncritical tree. These two parts are recovered by using two different sharing strategies of backup resources. We perform simulations to study static provisioning of survivable multicast sessions in a WDM mesh network with sparse light splitting and detailed simulations results are shown. View full abstract»

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  • On Bandwidth Efficient Coded OFDM using Multilevel Turbo Codes and Iterative Multistage Decoding

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4973 KB) |  | HTML iconHTML  

    In this paper, we present some design methods for bandwidth efficient coded OFDM system. Multilevel turbo coded M-QAM scheme is investigated and some novel strategies are proposed to reduce coding complexities. An iterative multistage decoding with feedback between higher levels and lower ones is considered to be combined with Turbo decoding, which can improve the overall performance greatly. Several simulation results show that these schemes can provide substantial coding gains with high spectral efficiency. View full abstract»

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  • An Improved Urban Macrocellular Model for MIMO Wireless Systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4953 KB) |  | HTML iconHTML  

    We present an improved model for outdoor MIMO wireless channels and its spatial fading correlation and capacity performances. The proposed model is more representative than the traditional independently and identically distributed (i.i.d) model by considering the remote scatterers on top of the "one-ring" model. We consider both local and remote scatterers with respect to the receiver for modeling the urban macrocellular wireless environment. The channel capacity for a given structure of scatterers and a set of physical parameters including the antenna pattern and propagation loss has been investigated. As a result, the fading correlation is expressed as a function of the scattering characteristics as well as the propagation parameters of the MIMO channels. We provide detailed analysis on the effect of correlation due to the increased number of scatterers and the capacity results obtained via extensive simulations. Using the proposed model we show the combined correlation and scattering effect on the capacity of MIMO systems and the difference on the capacity performance between the proposed macrocellular model and the "one-ring" model. View full abstract»

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  • Performance of Low-Density Parity-Check (LDPC) Coded OFDM system based on Adaptive Power Allocation Algorithm

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4581 KB) |  | HTML iconHTML  

    A LDPC-COFDM system model based on adaptive algorithm can allocate transmit power and bits among sub-carriers according to the channel gain of each sub-channel. An adaptive power allocation algorithm, which is beneficial for log likelihood ratio decoding of LDPC coded modulation, is proposed in this paper. The simulation results show that the model can effectively improve the bit-error-rate (BER) performance of the system, compared with the traditional OFDM system based on equal power allocation, adapting to the time-variant behavior of the multi-path fading channel. View full abstract»

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  • Rate Adaptive Live Video Streaming in Manets

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5136 KB) |  | HTML iconHTML  

    Live video streaming in a MANET is very appealing, as well as challenging due to high variability of the network bandwidth. In this paper, we enhanced CLARC (cross-layer adaptive rate control) taking playback buffer size into considerations, and emulated it in qualnet with real encoder and decoder. Extensive emulations were carried out to evaluate its performance. The results show that CLARC reacts to network bandwidth quickly; shares the bottleneck bandwidth with other CLARC flows fairly; and coexists with TCP. View full abstract»

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  • H-optimal traffic predictor for VBR video

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3834 KB) |  | HTML iconHTML  

    An H-optimal video traffic predicting algorithm is proposed, which not only minimizes the worst possible effect in the estimation error but also does not require a priori knowledge of the noise source statistics. The proposed method has been applied to modeling and predicting MPEG4 variable bit rate (VBR) video traffic. The low computational complexity and good prediction performance of the H predictor are encouraging and reflect on the practicability of the proposed approach. Simulation results show that the proposed model is more robust compared with the Kalman predicting model and is able to predict the original traffic more accurately, thus more suitable for real time video traffic prediction and resource reservation. View full abstract»

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  • A Lower Bound for Cumulative Self-Similar Processes and Burst Assembly Algorithms

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3241 KB) |  | HTML iconHTML  

    In this paper, we introduce a probabilistic lower bound for the amount of work arrived for self-similar processes. The obtained bound is accurate and tight. In the optical burst switching context, using the developed lower bound we obtained an analytical expression for the minimum burst length generated by a timer-based burst assembly algorithm, the maximum delay imposed by a burstlength-based burst assembly algorithm and project constraints of a mixed timer/burstlength-based burst assembly algorithm when the incoming traffic is self-similar. Our results are very useful when designing optical burst switching networks and analyzing the performance of burst assembly algorithms at the presence of self-similarity. View full abstract»

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  • Intrusion Detection System Based on Feature Selection and Support Vector Machine

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5705 KB) |  | HTML iconHTML  

    Support vector machine (SVM) has been applied to intrusion detection system (IDS) for its abilities to perform classification and regression. But for large-scale network intrusion detection problem, since solving a support vector machine is a typical quadratic optimization problem, which is influenced by the dimension and quantity of examples, many problems arise. KDDCUP'99 was used as the experiment dataset in this paper. A feature selection technology based on Fisher score was presented and used to construct a reduced feature subset of KDDCUP'99 dataset. SVM was used as a classifier. Experiment was run. The experiment results show, using Fisher score combined with SVM to select the important features is an effective method to reduce the dimension of the example feature space, and the classification accuracy has not dramatically decreased comparing to the original feature space. View full abstract»

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  • Peer-to-Peer Batching Policy for Video-on-Demand System

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (6761 KB) |  | HTML iconHTML  

    Multicast and peer-to-peer (P2P) are two common transmission strategies to provide scalable and cost efficient solutions for video-on-demand (VoD) services. It is noted that a native P2P mechanism requires small server resources and provides an insensitive delay to users. However, the bandwidth requirement inside the network is rapidly increased when more customers joins the video session. On the other hand, if the system simply uses a multicast scheme to deliver the video, the customers have to wait for a noticeable delay before watching the videos whereas the overall bandwidth requirement will not be significantly increased. In this paper, a new transmission policy denoted peer-to-peer batching (PPB) policy is proposed to exploit the multicast capability of the network and P2P paradigm to efficiently deliver video data to the clients. Our analysis shows that the proposed PPB scheme achieves better system performance when compared with Patching (a native multicast system) and DirectStream (a native P2P system). View full abstract»

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  • Multi-Channel Primary Initialization Algorithm for Wireless Sensor Networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3679 KB) |  | HTML iconHTML  

    The most urgent and important thing for a newly deployed sensor as to quickly establish a primary structure. In this paper, a practical algorithm for selecting cluster leader nodes and for setting up the affiliation of leader nodes and slave nodes is presented. Since the occurrence of collision (or co-channel interference) is a serious problem in unstructured networks, three independent channels are taken to reduce interference, Further, we analyze the algorithm based on a co-channel interference model. The simulation results show even in this harsh model, the primary initialization algorithm in our paper can be completed efficiently. View full abstract»

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  • Parametric Channel Estimation for OFDM Systems in Time-Varying Environment Based on Subspace Projecting and Tracking

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5501 KB) |  | HTML iconHTML  

    Channel estimation is critical for coherent detection in OFDM systems. In pilot symbol aided channel estimation methods, the LS channel estimation can be viewed as a noisy observation of the true channel frequency response, so the noise component can be compressed through signal subspace projecting. In this paper, we focus on parametric channel estimation method combined with subspace projecting. First, we estimate the signal space of the OFDM system, and then we can use ESPRIT method to estimate the multipath delay of wireless channel, finally we use subspace projecting to get more accurate channel estimation. When the channel multipath delays vary with time, the signal subspace should be tracked to keep the efficiency of channel estimation. Computer simulations show that the performance of our method is much better than traditional channel estimation methods and its nonparametric counterpart. View full abstract»

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  • The Effect of Channel Estimation Error on MIMO CDMA System

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3726 KB) |  | HTML iconHTML  

    Based on the LS codes, MCD (multi-code detection) and MLD (maximum likelihood detection) receiver, the paper analyses the effect of channel estimation error on MIMO CDMA system in Rayleigh fading channel. Both analysis and results show that channel capacity decreases quickly when the channel estimation error increasing. When the channel estimation error is smaller than one percent, the channel capacity is increasing with the antennas linearly. But the increasing rate of system capacity declines rapidly when the channel estimation error becomes larger. When it becomes ten percent, the system capacity will not increase nearly with the antenna number increasing. View full abstract»

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