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Computers and Communications, 2004. Proceedings. ISCC 2004. Ninth International Symposium on

Date 28 June-1 July 2004

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  • Multi-objective optimization scheme for dynamic multicast groups

    Page(s): 1018 - 1023 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (589 KB) |  | HTML iconHTML  

    In this paper, we propose a multi-objective traffic engineering scheme using different distribution trees to dynamic multicast groups (in which egress nodes can change during the connection's lifetime). If a multicast tree is recomputed from scratch, it may consume a considerable amount of CPU time and all communication using the multicast tree will be temporarily interrupted. To alleviate these drawbacks we propose a dynamic optimization model that makes use of a previously computed multicast tree (static model) in order to add new egress nodes. Using these two models, our aim is to combine into a single aggregated metric, the following weighting objectives: maximum link utilization, hop count, total bandwidth consumption and total end-to-end delay. Moreover, our proposal solves the traffic split ratio for multiple trees. We compare the dynamic and static multicast routing models using SNOPT solver. The proposed approach can be applied in MPLS networks by allowing explicit routes to be established in multicast events. View full abstract»

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  • DFT based transceivers with-windowing

    Page(s): 574 - 579 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB) |  | HTML iconHTML  

    In this paper we consider window designs for DFT (discrete Fourier transform) based multicarrier transceivers without using extra cyclic prefix. As in previous works of window designs for DFT based transceiver, a post processing matrix, generally channel dependent, is needed to have a zero forcing receiver. We show that post processing is channel independent if and only if the window itself has the cyclic prefixed property. We design optimal windows with minimum spectral leakage subject to the cyclic-prefixed condition. Moreover, we analyze how post processing affects SNR (signal to noise ratio) at the receiver, an aspect that is hot considered in most of the earlier works. The resulting SNR can be given in a closed form. Join optimization of spectral leakage and SNR are also considered. Furthermore, examples demonstrate that we can have a significant reduction in spectral leakage at the cost of a small SNR penalty. View full abstract»

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  • A novel Lagrangian-relaxation to the minimum cost multicommodity flow problem and its application to OSPF traffic engineering

    Page(s): 957 - 962 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (608 KB) |  | HTML iconHTML  

    The minimum cost multicommodity flow problem plays a central role in today's operations research theory with applications ranging from transportation and logistics to telecommunications network routing. In this paper, we introduce a novel Lagrangian-relaxation technique, which, given an initial feasible solution, can solve the minimum cost multicommodity flow problem as a sequence of single-commodity flow problems. Our methodology is best suited for OSPF traffic engineering, because it can rapidly improve a given path set towards approximate optimality while simultaneously provides the link weights, which implement the paths as shortest paths. View full abstract»

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  • Adaptive LDPC for Rayleigh fading channel

    Page(s): 651 - 656 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (718 KB) |  | HTML iconHTML  

    Two adaptive coded modulation schemes employing LDPC (low-density parity-check) code are proposed for Rayleigh fading channels. Scheme 1: we fix the code rate (rate=1/2), and only change the modulation methods according to the channel state, that is, during poor channel conditions, QPSK modulation is employed, as channel conditions improve, more efficient modulation scheme such as 8PSK is used. Scheme 2: the modulation scheme is fixed (BPSK modulation), and the code rate is changed according to the channel state. Through simulation, we get the performance of these two adaptive LDPC schemes under different demands of BER, and the comparison between adaptive LDPC and nonadaptive LDPC is also given. View full abstract»

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  • An effective heuristic algorithm for dynamic multicast routing with delay-constrained

    Page(s): 1024 - 1031 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (729 KB) |  | HTML iconHTML  

    With the development of multimedia group applications, the construction of multicast routing tree satisfying quality of service (QoS) is more important. In many multicast applications, it is required that the network supports dynamic multicast which the membership of the multicast group changes with the time. In this paper an effective heuristic algorithm is proposed for dynamic multicast routing with delay-constrained. The aim of this proposed algorithm is to guarantee that: 1) the cost of multicast tree is as small as possible at each node addition/removal event; 2) all the maximal path delay meets a fixed delay-constrained; and 3) minimize perturbation to an existing tree. The proposed algorithm is based on "damage" and "usefulness" concept, and a balancing factor (BF) is provided to judge whether or not to arrange a region of tree. Mutation operation in genetic algorithm (GA) is also employed to find an attached node in tree for a dynamic adding node. Simulation shows that our algorithm performs well than those static heuristic algorithms in term of cost especially. View full abstract»

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  • Interleaving harmonic broadcasting and receiving scheme with loss-anticipation delivery

    Page(s): 600 - 605 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB) |  | HTML iconHTML  

    With the growth of broadband networks, video-on-demand (VoD) has become realistic. Many significant broadcasting schemes have been proposed to reduce the bandwidth requirement for stored popular videos, but they cannot be used for provide reliable delivery over lossy channels perfectly. Herein, we propose a new broadcasting scheme, called the interleaving harmonic broadcasting (IHB) scheme, which guarantees continuous playback, and mitigates the effect of packet losses. Further, in comparison with the poly-harmonic broadcasting (PHB), cautions harmonic broadcasting (CHB) scheme, reliable periodic broadcasting (RPB) scheme and second chance broadcasting (SCB) scheme, the IHB outperforms on required bandwidth, maximum required buffers and maximum disk transfer rate. View full abstract»

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  • Dynamic IP router-tables using highest-priority matching

    Page(s): 858 - 863 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (689 KB) |  | HTML iconHTML  

    We develop a data structure called BOB (binary tree on binary tree) for dynamic router tables in which the rule filters are nonintersecting ranges and in which ties are broken by selecting the highest-priority rule that matches a destination address. Prefix filters are a special case of nonintersecting ranges and the commonly used longest-prefix tie breaker is a special case of the highest-priority tie breaker. We also develop two modified version of BOB - PBOB (prefix BOB) for the case when all rule filters are prefixes and LMPBOB (longest matching-prefix BOB) when all rule filters are prefixes and longest-prefix matching is to be done. On practical n-rule router table, BOB, PBOB and LMPBOB perform search, insert and delete In O(log n) time and with O(log n) cache misses. Experimental results also are presented. View full abstract»

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  • K-factor Gegenbauer ARMA process for network traffic simulation

    Page(s): 963 - 968 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (508 KB) |  | HTML iconHTML  

    The k-factor Gegenbauer ARMA process has been a widely used tool for modeling and predicting financial time series. This model has the ability to capture both short-range and long-range dependencies (SRD and LRD, respectively). Since the high-speed network traffic exhibits both of these dependencies, GARMA could be used for its modeling and prediction. In this paper, we present a simple parameter estimation procedure for the k-factor GARMA model. We also discuss the synthesis scheme for this model. The estimation procedure is used to model an MPEG video traffic data. Several synthetic traffic data are generated by varying the GARMA model parameters. The main characteristic of the synthetic traffic, self-similarity, is tested and compared to that of the actual MPEG data and the traffic synthesized using the autoregressive (AR) model. The results show that the k-factor GARMA model captures the main traffic characteristics in both time and frequency domain. They also show that the synthetic traffic data using the k-factor GARMA model are the closest to the actual data. View full abstract»

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  • Performance analysis of cooperative macro-diversity in mobile cellular networks

    Page(s): 686 - 689 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (397 KB) |  | HTML iconHTML  

    Based on the concept of multi-hop relaying, a cooperative macro-diversity system is suggested. In the Rayleigh-lognormal composite fading environment, the performances of a hexagonal macro-diversity cellular system are investigated. The maximum ratio combining (MRC) is considered for the uplink analysis of outage probability and bit error rate (BER) for differential phase shift keying (DPSK). Numerical results show that the performances of the new system outperform those of the conventional single-hop macro-diversity system. The multi-hop relaying can enhance the robustness of performance, and it is helpful to improve the reliability of the radio link. View full abstract»

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  • Streaming over EGPRS

    Page(s): 969 - 974 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (653 KB) |  | HTML iconHTML  

    Enhanced general packet radio service (EGPRS) is a new technology that provides higher bit rates and better error protection for packet-switched data transmissions, compared to the traditional GPRS technology. Especially video streaming which requires higher bitrates in order to achieve sharp image quality and fluent motion. GPRS allowed the introduction of streaming service with adequate quality, but better technology is needed in order to provide a more enjoyable service. The purpose of this article is to show what new benefits EGPRS brings to packet-switched streaming service (PSS). View full abstract»

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  • Nonlinear space-time multiuser detector for non-Gaussian channels

    Page(s): 610 - 614 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (458 KB) |  | HTML iconHTML  

    A space-time nonlinear receiver for a DS-CDMA synchronous channel is proposed for jointly mitigating impulsive noise and multiple access interference. The proposed scheme combines linear decorrelators and antenna arrays with nonlinear front ends based on the affinity matched myriad nonlinear filter. This myriad (log Cauchy) filter is incorporated to combat the impulsive noise and prevent it from entering the system. The proposed detector also incorporates a structure for estimating the impulsive noise parameter in order to update a filter parameter called the nonlinearity parameter. Monte Carlo simulation results of the proposed space-time receiver are presented to justify the relative merits of nonlinear signal processing in the space-time domain. View full abstract»

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  • Time-series model for wireless fading channels in isotropic and non-isotropic scattering environments

    Page(s): 633 - 638 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (559 KB) |  | HTML iconHTML  

    This work presents an autoregressive (AR) model for fading envelope influenced by isotropic and non-isotropic scattering environments. It is shown that at least a second order AR process is required to model the damped sinusoidal auto/cross correlation function inherent in the complex received envelope. The comparison of statistics of the simulation trace obtained using the model shows good agreement with the theoretical values. The model based simulation procedure is compared to the Jake's simulator for isotropic scattering case and is shown to exhibit an order of magnitude smaller time complexity. View full abstract»

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  • A limited path unicast QoS routing algorithm

    Page(s): 870 - 875 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB) |  | HTML iconHTML  

    In this paper, we propose a novel limited path algorithm called LPUA to deal with two constrained unicast QoS routing problems, which is known as NP complete. By combining two weights linearly into a single one, Dijkstra algorithm based on the single weight can be used directly to return a least cost path between the source node and the destination node. When a routing request comes, LPUA only needs to compute a limited number of paths. If any of these paths cannot meet the routing constraints, the routing request would be refused. Extensive simulations have show that LPUA is very efficient. View full abstract»

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  • Bandwidth aggregation in stream control transmission protocol

    Page(s): 975 - 980 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (588 KB) |  | HTML iconHTML  

    In this paper, we address various aspects related to extending and engineering stream control transmission protocol (SCTP) to utilize its multi-homing support for simultaneous transmission of data chunks on different path, while maintaining the congestion control on each path to ensure fair integration with other traffic in the network. The extended SCTP, referred to as load sharing-SCTP (LS-SCTP), is able to aggregate the bandwidth of all the active transmission paths between the communicating endpoints. It monitors the paths, and accordingly chooses the paths that are suitable for load sharing. In addition, LS-SCTP retransmission mechanism accelerates the delivery of missing data to the receiver to prevent stalling the transport connection while waiting for missing data chunks. Simulation results show that LS-SCTP is extremely beneficial for networks with limited bandwidth and failure prone links. View full abstract»

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  • Availability aware cost modeling of mesh architectures for long-haul networks

    Page(s): 766 - 771 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB) |  | HTML iconHTML  

    Carriers determined to stay competitive in the market have learned that simply going for the cheapest networking solution in terms of CAPEX is not enough, as the total cost includes OPEX as well. Availability of the network, which is too important to ignore in terms of providing meaningful service to customers, also relates to OPEX cost through maintenance and repair efforts. This study introduces a modeling methodology that incorporates availability awareness in to the cost modeling in order to propose a mesh architecture for a given core network with an acceptable trade-off between cost-efficiency and availability. View full abstract»

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  • Improving the stability of spanning trees for application-layer multicast

    Page(s): 1071 - 1076 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (654 KB) |  | HTML iconHTML  

    Currently, a large number of ALM algorithms have been proposed to build the overlay networks and transmit data through spanning trees over the overlay networks. However, few works focus on the congestion of spanning tree, the key to the performance of application. This paper studies the impact of spanning tree congestion on ALM performance and proposes a model to quantify and evaluate the congestion. A statistical link model is introduced to describe congestion occurring in ALM networks and a dependency-degree factor is presented to express the dependence between adjacent links. Furthermore, two schemes, the inter-level redundant links (INTER-RL) scheme and the intra-level redundant links (INTRA-RL) scheme, are proposed to enhance the resilience of ALM spanning trees against congestion. Simulation results indicate that the proposed statistical model well describes the congestion in ALM networks and two redundant link schemes both significantly boost the robustness of ALM even in tough network environments. View full abstract»

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  • Path loss model for TETRA networks in metropolitan areas

    Page(s): 690 - 695 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (538 KB) |  | HTML iconHTML  

    This paper reports on measurements of the attenuation in the transmitted RF-power of a TETRA system, operating in the UIIF band. The measurements data are consistent with a log-distance path loss model for arbitrary T-R separation, with a path loss exponent n = 4.0 ± 0.5. Small scale fading is characterized by a Gaussian signal level distribution (log-normal) with standard deviation s = 8.6 ± 0.2. Furthermore, the reference distance in the far field of the transmitting antenna from the measurements is d0 = 1 km. Interestingly, the average value of the received RF-power approaches a level close to the dynamic sensitivity of the TETRA receivers at approximately the same distance (around 5 km) from a base station, for various low-altitude base station locations with similar transmission characteristics. This distance provides a simple characterization reference indicative of the attenuation of the RF-power in the particular urban environment; it also provides a rule of thumb for cell planning in metropolitan locations similar to that of the Greek capital. View full abstract»

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  • Accuracy of link capacity estimates using passive and active approaches with CapProbe

    Page(s): 1085 - 1090 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (676 KB) |  | HTML iconHTML  

    CapProbe is an inexpensive and accurate means to estimate capacity. CapProbe combines both dispersion and end-to-end delay to estimate the capacity of the narrowest link on a path. We evaluate in this paper the accuracy of CapProbe estimation, and its dependence on end systems speed, packet sizes, narrow link speeds, and other system parameters. We test kernel and user level implementations of CapProbe and find the kernel implementation to be much more accurate. We also evaluate through experiments the effect of probing packet size on the accuracy of CapProbe estimation. Finally, we explore the idea of a "passive CapProbe" within the context of a TCP flow. Passive here means that the dispersion and delay observed for the TCP flow data and ACK packets, without introducing any additional probing packets. We test active and passive versions of CapProbe with TCP. The active version is found to produce more accurate capacity estimates than the passive version. View full abstract»

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  • Design of odd-periodic complementary binary signal set

    Page(s): 590 - 593 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (322 KB) |  | HTML iconHTML  

    Two or more sequences are called a set of odd-periodic complementary sequences (OPCS) if the sum of their respective odd-periodic autocorrelation function is a delta function. In this paper, the definition of OPCS is given. The construction and synthesis methods of OPCS are discussed. The relation of the sets of odd-periodic complementary binary sequences with the sets of periodic complementary binary sequences is pointed out. We get some new PCS. View full abstract»

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  • QoS support for interactive communication with DVB/RCS satellites

    Page(s): 897 - 902 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (607 KB) |  | HTML iconHTML  

    Full integration of satellite technology in future terrestrial infrastructures requires support for high-quality broadband bi-directional communications. Research efforts in the field of satellite communications are currently oriented in the study of QoS-aware solutions for DVB-S and DVB-RCS, which allowed seamless deployment in the Internet. In this paper the QoS architecture designed in the framework of the SATIP6 project, sponsored within the 5th EU Research Programme Framework, is presented. This is organized into two main modules, the traffic control and bandwidth on demand (BoD) module, whose aim are to provide for differentiated service of conveyed IP flows and efficient utilization of uplink bandwidth respectively. Experimental results obtained through Opnet simulations are reported and discussed to assess the effectiveness of the designed solution in terms of both service differentiation and efficient utilization of satellite resources. View full abstract»

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  • Closed-form results for the BER of maximal ratio combining with channel estimation errors in Ricean fading channels

    Page(s): 645 - 650 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (590 KB) |  | HTML iconHTML  

    Closed-form expressions for computing the average bit error rate (BER) for a class of modulation schemes in Ricean flat fading channels with maximal-ratio combing (MRC) diversity and channel estimation errors are derived. The results are applicable to channel estimators that are jointly Gaussian with the channel gain. The BER performance of pilot symbol assisted modulation (PSAM) is studied. The effects of estimation error on the diversity system are examined as well as the influences of varying the Ricean factor, K, and changing the numbers of diversity branches, L. View full abstract»

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  • Optical CDMA protocol with selective retransmission

    Page(s): 621 - 626 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (542 KB) |  | HTML iconHTML  

    New protocol for optical code-division multiple access (CDMA) networks is proposed. Our proposed protocol is based on selective retransmission technique. A mathematical model is presented using a detailed state diagram. The protocol is analyzed using equilibrium point analysis (EPA), and its performance is examined using traditional throughput and average delay for several network parameters. We also compare the performance of the proposed protocol to the R3T protocol based on go-back-n technique. Results show that a higher performance is achieved by the proposed protocol at the expense of system complexity. View full abstract»

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  • On the provision of immersive audio communication to massively multi-player online games

    Page(s): 1000 - 1005 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (613 KB) |  | HTML iconHTML  

    This paper discusses issues in providing immersive audio communication to massively multi-player online games (MMOG). We focus on network and server architectures for creating immersive audio scenes for game clients. We examine advantages and limitations of several architectures, including central server, distributed servers, and peer-to-peer architectures. We focus on a dynamic centralized server architecture which is suitable for the current MMOG in terms of sealability at end users and resource efficiency. We propose algorithms to optimize the performance of a centralized server. Finally, a simulation study is carried out to evaluate the performance of our proposed centralized server architecture and provide some comparisons with others in term of delays and network resource usage. View full abstract»

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  • Evaluation of flow control algorithms for ABR multipoint services

    Page(s): 1077 - 1084 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (647 KB) |  | HTML iconHTML  

    In this paper, we first present a simulation-based evaluation of existing multipoint-to-point (mp-p) flow control schemes for ABR (available bit rate) services in ATM (asynchronous transfer mode) networks. The evaluation shows that these schemes suffer from one or more of the following problems: non-compliance with the selected bandwidth allocation definition (BAD), link under-utilization, and prolonged rate fluctuations. Moreover, most of them implement only one BAD, namely source-based allocation. We then propose an mpp flow control algorithm, the WSB (weighted-source-based) algorithm that is effective and supports a large set of BADs. Experimental results are presented to demonstrate the advantages of the WSB algorithm: correct rate allocations with fast convergence, maximum link utilization, and minimal rate oscillations. View full abstract»

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  • SPLIT: A priority based TCP-friendly video protocol

    Page(s): 828 - 833 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (684 KB) |  | HTML iconHTML  

    In this paper, priority dropping mechanism (PDM) is applied to RED algorithm to protect the video layers selectively from performance and throughput deterioration. Moreover, to achieve fairness among different type of the network traffic with PDM, packet classification scheme (PCS) is implemented to assign the priority to each SPLIT layer or packet based upon the target rate. View full abstract»

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