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Communications, IET

Issue 6 • Date June 2009

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Displaying Results 1 - 17 of 17
  • Simulation, analysis and measurement of broadband network traffic - [editorial]

    Publication Year: 2009 , Page(s): 883 - 886
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    Freely Available from IEEE
  • Analysis, simulation and measurement in large-scale packet networks

    Publication Year: 2009 , Page(s): 887 - 905
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (545 KB)  

    The authors review analysis, simulation and measurement techniques, the three fundamental methods for performance evaluation in packet networks, looking at what's known, what's new and some outstanding issues. In trying to avoid re-reviewing material which has already been well summarised elsewhere, the authors concentrate on areas that are relatively new or possibly less generally well appreciated. So, under analysis, the focus is on models for network topologies and connectivity, and on wireless access. In the simulation section the focus is on techniques for scalable simulation for large-scale packet networks. Compared to the other two areas measurement is relatively new anyway, and more time is spent on motivation, techniques and some recently discovered limitations. View full abstract»

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  • Adaptive wavelet-based multifractal model applied to the effective bandwidth estimation of network traffic flows

    Publication Year: 2009 , Page(s): 906 - 919
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (253 KB)  

    The authors investigate effective bandwidth estimation and Quality of Service (QoS) aware bandwidth provisioning for multifractal network traffic flows. They develop a novel adaptive wavelet-based multifractal model (AWMM) by using properties of the wavelet coefficients of multifractal cascade processes. The proposed AWMM has real-time updating capability and proves to be efficient in capturing multifractal network traffic characteristics. In addition, the authors derive an analytical expression for the effective bandwidth estimation of AWMM traffic flows, capable of being used to meet desired byte loss probabilities. Finally, they present an online effective bandwidth estimation algorithm that is incorporated into an adaptive bandwidth provisioning scheme and comparatively evaluated against some other bandwidth allocation methods. View full abstract»

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  • Precedence-enabled per-hop behaviour: impact on TCP and UDP flows

    Publication Year: 2009 , Page(s): 920 - 932
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (634 KB)  

    The author proposes and analyses an approach to support both precedence and preemption (P&P) and QoS handling in common packet transport infrastructures. Precedence has to do with the relative importance of the information content, whereas preemption has to do with mechanisms to deny lower precedence traffic access to network resources in favour of higher precedence traffic, when necessary. The author's approach to this duality is to enhance active queue management (AQM) techniques to provide P&P capabilities and rely on standard, well-studied QoS schedulers, for example, Weighted Round Robin, Class-Based Weighted Fair Queuing, etc., for handling QoS requirements. The present scheme allows low-order queues (within the context of QoS handling) to plead up to the next higher-order queue for help in alleviating queue congestion under periods of communication link overload. The scheme is referred as the cross-queue-AQM (CQ-ACM) scheme and can be extended to higher numbers of queues and any type of scheduler. Through extensive simulation studies, the performance of CQ-AQM scheme under heavy traffic limits is investigated, where preemption is required. The performance metrics of interest to this analysis are packet delay, packet loss and throughput as a function of the packet QoS class and P-L. Further, two new metrics of merit, Gain and System Efficiency, are defined, which are specific to P&P considerations. The studies concentrated on both flow-controlled and non-flow-controlled traffic, as well as mixed traffic conditions. Simulation results show that the algorithms perform extremely well for all cases studied. View full abstract»

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  • Application of the generalised ballot theorem for evaluation of performance in packet buffers with non-first in first out scheduling

    Publication Year: 2009 , Page(s): 933 - 944
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (337 KB)  

    Packet scheduling is a vital component to support different classes of service in all-packet networks. In classical queuing systems, the waiting-time performance of non-first in first out buffer scheduling systems could be predicted through the use of analysis. However, all-packet networks feature traffic patterns that do not conform to classical Poisson-like processes, and this greatly complicates the evaluation of their performance. Our novel approach to this problem is through a hybrid combination of analysis and simulation. The authors derive a combinatorial algorithm, using the generalised ballot theorem, which predicts waiting times for low-priority traffic. When this algorithm is combined with prior work on traffic aggregation, the authors achieve a significant reduction in the state space associated with the buffer under study. To numerically test this algorithm, the authors demonstrate its use in simulation, where state space and event count reduction is a fundamental requirement to ensure experiments complete in a timely fashion. Numerical results from these simulations show a very significant reduction in the number of events processed combined with improved state coverage. This is achieved while maintaining a highly accurate representation of packet delays compared with a conventional approach. View full abstract»

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  • Methodology for monitoring and measurement of complex broadband networks

    Publication Year: 2009 , Page(s): 945 - 956
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (946 KB)  

    A robustly engineered monitoring and measurement capability provides comprehensive and timely performance information that allows broadband network operators and service providers to observe and proactively respond to events that occur during deployment and operation of their respective networks. As network complexity increases, so do the requirements for monitoring and measurement to ensure the high-quality service to internal and external customers. A methodology for monitoring and measurement of complex broadband networks is presented. This methodology includes a framework and reference architecture, essential metrics categories to refine and focus the collection of information and extensions to support net-centric enterprise systems driven by service-oriented architecture (SOA). Examples of the application of the methodology to complex broadband networks are provided along with suggestions for further work. View full abstract»

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  • Challenges in the capture and dissemination of measurements from high-speed networks

    Publication Year: 2009 , Page(s): 957 - 966
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (211 KB)  

    The production of a large-scale monitoring system for a high-speed network leads to a number of challenges. These challenges are not purely technical but also socio-political and legal. The number of stakeholders in such monitoring activity is large including the network operators, the users, the equipment manufacturers and, of course, the monitoring researchers. The MASTS project (measurement at all scales in time and space) was created to instrument the high-speed JANET lightpath network and has been extended to incorporate other paths supported by JANET(UK). Challenges the project has faced included: simple access to the network; legal issues involved in the storage and dissemination of the captured information, which may be personal; the volume of data captured and the rate at which these data appear at store. To this end, the MASTS system will have established four monitoring points each capturing packets on a high-speed link. Traffic header data will be continuously collected, anonymised, indexed, stored and made available to the research community. A legal framework for the capture and storage of network measurement data has been developed which allows the anonymised IP traces to be used for research purposes. View full abstract»

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  • Pathpair: a fast available bandwidth estimation tool with the asymptotic one way delay comparison model

    Publication Year: 2009 , Page(s): 967 - 978
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    Significant research has been dedicated to active probing methods used to estimate the end-to-end available bandwidth (avail-bw) of a network path. The measurement speed of an avail-bw estimation tool is vital to real-time network services such as transport control protocol (TCP) slow start, path selection for P2P applications and video streaming services and so on. In addition, a fast avail-bw estimation tool sends less probing traffic to a measured network. Pathload, a one way delay (OWD) based tool, has been widely regarded as one of the most accurate tools, but its estimation speed is often 10 or more seconds per measurement. A fast OWD-based avail-bw estimation scheme has been explored. This scheme is based on the proposed asymptotic OWD comparison model, and an estimation tool called Pathpair has been developed. Validated in a real Internet environment, experimental results show that with Pathpair the measurement speed has been significantly improved (1-3 s per measurement), while preserving accuracy compared with other major tools like Pathload and Spruce. View full abstract»

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  • Measurement of packet loss probability by optimal design of packet probing experiments

    Publication Year: 2009 , Page(s): 979 - 991
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    Packet-level measurement is now critical to many aspects of broadband networking, for example for guaranteeing service level agreements, facilitating measurement-based admission control algorithms and performing network tomography. Because it is often impossible to measure all the data passing across a network, the most widely used method of measurement works by injecting probe packets. The probes provide samples of the packet loss and delay, and from these samples the loss and delay performance of the traffic as a whole can be deduced. However, measuring performance like this is prone to errors. Recent work has shown that some of these errors are minimised by using a gamma renewal process as the optimal pattern for the time instants at which to inject probes. This leaves the best rate at which to inject probes as the key unsolved problem, and this is addressed here by using the statistical principles of the design of experiments. The experimental design approach allows one to treat packet-level measurements as numerical experiments that can be designed optimally. Modelling the overflow of buffers as a 2-state Markov chain, the system's likelihood function is deduced, and from this a technique (using the Fisher information matrix) to determine the upper-bound on the optimal rate of probing is developed. A generalisation of this method accounts for the effect of the probed observations interfering with the experiment. The numerical results focus on VoIP traffic, allowing one to show how this methodology would be used in practice. One application of this is in measurement-based admission control algorithms, where the technique can be used to provide an upper-bound on the rate at which probes should be injected to monitor the loss performance of the target network, prior to making an admit/do not admit decision. View full abstract»

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  • Multi-scale analysis of generalised processor sharing queues with long-range-dependent traffic inputs and variable service rates

    Publication Year: 2009 , Page(s): 992 - 1004
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (627 KB)  

    An analytical technique is provided to estimate queue-length and delay distributions for multi-queue systems using generalised processor sharing discipline with time-correlated variable service rates, based on two-dimensional multi-level decoupling. First, temporal decomposition is used to convert the time-correlated queuing problem into a set of sub-problems over several timescales. Subsequently, queue decomposition exploits the queue weight dependencies to convert a multi-queue problem into a set of single-queue problems. The core of the analysis lies in estimating the multi-scale service rate models for each of these queues. The authors show the hierarchy of this estimation and the dependency of the queue service rate on the unused capacity of the other queues and their weights. Simulation and analytical results on queue and delay survivor functions are in good agreement. View full abstract»

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  • Differentiated cooperative multiple access for multimedia communications over fading wireless networks

    Publication Year: 2009 , Page(s): 1005 - 1015
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (291 KB)  

    The quality of service (QoS) support for multimedia communications faces a big challenge in a fading wireless network. On one hand, conventional automatic repeat request (ARQ) schemes are not effective for small-scale fading channels with correlated errors due to consecutive retransmission failures. On the other hand, large-scale fading due to propagation loss or shadowing severely limits transmission range. A novel differentiated cooperative medium access control (MAC) protocol, called DC-MAC, is proposed to enhance the QoS support for multimedia communications while supporting service differentiation based on the IEEE 802.11e architecture. By enabling cooperative ARQ, the retransmission is initiated from an appropriate transmission queue of an appropriate relay node instead of the original source. Since unnecessary and useless retransmissions may intensify the node contention and degrade the system performance contrarily, a novel negative acknowledgement feedback mechanism is introduced for loss distinguishing and channel estimation such that cooperative retransmission will be employed only when necessary and only by competent nodes. Extensive simulations are conducted on the OPNET platform to analyse the performances of DC-MAC under both small-scale and large-scale fading. Simulation results show that the proposed scheme significantly improves the performances of both multimedia applications and best-effort data applications in terms of throughput, delay and coverage with moderate user contention. View full abstract»

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  • Robust energy detection in cognitive radio

    Publication Year: 2009 , Page(s): 1016 - 1023
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (217 KB)  

    The success of advanced dynamic utilisation of the scarce spectrum in cognitive radio depends upon reliable primary signal detection where accurate noise power estimation plays a critical role. However, in practical scenarios, the noise power cannot be accurately estimated, which significantly degrades the performance of primary signal detection. To avoid inaccurate noise power estimation and associated accumulated problems. A novel two-stage Bayesian estimation-based energy detection algorithm is introduced here. This algorithm, as supported by simulation results, shows two main features: (a) a superior performance of 1 dB compared with previous methods; (b) the consistency of the algorithm has been proved indicating that 100 correct primary user signal detection can be approached as the number of samples tends to infinity. View full abstract»

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  • Effect of clock offset on an impulse radio ultra wideband ranging system with comparators

    Publication Year: 2009 , Page(s): 1024 - 1029
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (454 KB)  

    Impulse radio ultra wideband (IR-UWB) can achieve high resolution in ranging because it uses a very short pulse with a duration of less than 1 ns. In order to reduce cost and power consumption, a ranging system with high-speed comparators has been proposed. In this system, it is necessary to reduce noise power through averaging the comparator outputs. The authors evaluate the effect of clock offset on the averaging process, and a two-stage averaging scheme for the IR-UWB ranging system is proposed. Through computer simulation, it is proved that the proposed scheme can reduce the effect of the clock offset with appropriate numbers of initial averaging. View full abstract»

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  • Quality of service constrained throughput optimisation for joint adaptive transmission with automatic repeat request over block-fading channels

    Publication Year: 2009 , Page(s): 1030 - 1040
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    An optimisation framework for wireless link adaptation which maximises the system throughput subject to a packet-level quality of service (QoS) constraint is presented. The authors consider joint adaptive variation of the transmitted power level, transmission data rate and packet-error-rate (PER) at the physical layer to improve the throughput performance of the selective-repeat automatic repeat request (SR-ARQ) protocol over block-fading channels. Specifically, for discrete-rate coded M-QAM schemes, the authors present a power and rate adaptation algorithm that guarantees a target PER constraint. The proposed framework also facilitates optimising the throughput performance for delay constrained wireless applications, which imposes a limit on the number of retransmissions for the ARQ. In particular, a link adaptation scheme is presented, which guarantees a target packet-loss rate (PLR) when a truncated SR ARQ protocol at the data-link layer is employed. Numerical results indicate that the proposed adaptation schemes compared with other adaptive schemes noticeably enhance the system throughput. Also, in the case of truncated ARQ, the results illustrate a fundamental trade-off between the delay and PLR QoS metrics achieved at the maximum throughput performance. View full abstract»

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  • Adaptive RS codes for message delivery over an encrypted mobile network

    Publication Year: 2009 , Page(s): 1041 - 1049
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (590 KB)  

    The authors present a hybrid automatic repeat request technique using adaptive Reed-Solomon (RS) codes with packet erasure. This technique suits the transport layer in tactical mobile wireless networks with type I encryption, where encryption erasures the entire Internet protocol packet. The novelty of the presented technique is the multifaceted optimisation of Reed-Solomon codes at the transport layer for delivery assurance, speed of service (SoS) and network throughput. With this technique, the transport layer in tactical networks can meet the stringent requirements of quality of service imposed by the tactical network user, even under adverse conditions. These requirements define a high level of reliability (delivery assurance), a specific SoS and optimum use of the limited bandwidth (BW) of the wireless network, where the probability of packet erasure can be very high. The provided probabilistic analysis shows that focusing on network throughput alone will result in violating SoS and delivery assurance requirements. On the other hand, focusing on SoS and delivery assurance requirements can result in poor network throughput. The multifaceted optimisation technique, which utilises hybrid ARQ for message delivery, is described using a homogeneous Markov chain. View full abstract»

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  • Achieving higher throughput in ieee 802.11 wireless local area networks with burst transmission methods

    Publication Year: 2009 , Page(s): 1050 - 1060
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (597 KB)  

    As extensions in the emerging 802.11e for quality-of-service provisioning, burst transmission and the acknowledgment aggregation are the two important operations to improve the channel efficiency of IEEE 802.11-based wireless local area networks (WLANs). However, only a few works have been done on these operations, and usually assumed the networks to be operated under saturated traffic conditions and error-free channels. In practice, the assumptions may not be valid because real-time traffic with proper rate control will not saturate the networks and the channel is generally error-prone. Thus, the authors consider two new methods resulted from these operations and analyse their performance under unsaturated and error-prone WLANs, with a Markov chain model. The results show that the new methods generally have better throughput than the conventional IEEE 802.11 medium access control (MAC) in the WLANs. View full abstract»

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  • Medium access control access delay analysis of IEEE 802.11e wireless LAN

    Publication Year: 2009 , Page(s): 1061 - 1070
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (322 KB)  

    The IEEE 802.11e standard is specified to support quality-of-service in wireless local area networks, and different contention parameters are designated to each type of service. This developed model is presented to analyse the scheduling and the contention between packets with different priorities, where the new features of the enhanced distributed channel access such as virtual collision, backoff, minimum contention window and different arbitration inter-frame spaces are taken into account. Based on the model, the delay performance of differentiated service traffic is analysed and a recursive method is proposed, which is capable of calculating the mean access delay. Simulations show that the model and the analysis provide an insight into the protocol and the effects of different parameters on the performance. View full abstract»

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IET Communications covers the theory and practice of systems, networks and applications involving line, mobile radio, satellite and optical technologies for telecommunications, and Internet and multimedia communications.

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