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Communications, IEE Proceedings-

Issue 1 • Date Feb 2001

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Displaying Results 1 - 9 of 9
  • Online error detection through observation of traffic self-similarity

    Page(s): 38 - 42
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    The authors present a new and universally applicable approach to error detection in packet or cell communication networks. The error detection uses measured traffic load data. The advantage is that detection of an error in a low layer reduces the probability of an undetected error in higher layers, and makes time-costly error detection in higher layers unnecessary. Most systems use static traffic load thresholds for error detection. The authors present an approach which can achieve considerably higher sensitivity. Their basic idea is to exploit the property of self-similarity in network traffic. This analytical redundancy gives a reference behaviour of the network traffic load, which allows the detection of faulty behaviour in the real network traffic load. For the error detection, the validity of the given self-similar property is checked through a deviation indicator Q based on second-order properties of the time series' distributions. This is a sufficient condition for normal (error-free) behaviour View full abstract»

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  • Regenerator placement algorithms for connection establishment in all-optical networks

    Page(s): 25 - 30
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (492 KB)  

    In wavelength-routed all-optical networks, signals are transmitted on a direct optical path, or a lightpath, in a single-hop manner without opto-electronic/electro-optic (OE/EO) conversion at intermediate nodes. However, due to the physical constraints of optical elements such as ASE noise and crosstalk, signals can be degraded on a long path. To establish a connection under such impairments, the optical signal may need to be regenerated at intermediate nodes, dividing a lightpath into two or more fragments. However, since signal regeneration at intermediate nodes requires additional network resources, the selection of these nodes should be made carefully to minimise blocking of other lightpaths. The problem of establishing a lightpath in a multihop manner under physical constraints is considered. The authors provide both minimal-cost and heuristic algorithms for locating signal regeneration nodes (SRNs). For a minimal-cost algorithm, the problem is formulated using dynamic programming (DP) such that blocking of other lightpaths due to the lack of transmitters/receivers (TXs/RXs) and wavelengths is minimised throughout the network. The blocking performances of the algorithms are compared with several other algorithms in a ring network View full abstract»

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  • Random-walk-based characterisation of multiple access interference in a DS/SSMA system

    Page(s): 43 - 48
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    The problem of calculating the probability of error in a DS/SSMA system has been extensively studied for more than two decades. When random sequences are employed some conditioning must be done before the application of the central limit theorem is attempted, leading to a Gaussian distribution. The authors seek to characterise the multiple access interference as a random-walk with a random number of steps, for random and deterministic sequences. Using results from random-walk theory, they model the interference as a K-distributed random variable and use it to calculate the probability of error in the form of a series, for a DS/SSMA system with a coherent correlation receiver and BPSK modulation under Gaussian noise. The asymptotic properties of the proposed distribution agree with other analyses. This is, to the best of the authors' knowledge, the first attempt to propose a non-Gaussian distribution for the interference. The modelling can be extended to consider multipath fading and general modulation View full abstract»

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  • Multicast ABR service in ATM networks using a fuzzy-logic-based consolidation algorithm

    Page(s): 8 - 13
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    The multicast available bit rate (ABR) service in ATM networks is important for many emerging data service applications. The authors propose a fuzzy-logic-based consolidation algorithm to solve the problems of consolidation noise and delay. The proposed algorithm is composed of the CI analyser, the adaptation law, and the fuzzy predictor. Using the CI analyser, the adaptation law determines an adaptation parameter so that the fuzzy predictor estimates the unknown congestion information. The usefulness of the proposed algorithm is demonstrated by some numerical results View full abstract»

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  • Optical OPPM-CDMA receivers with chip-level detectors

    Page(s): 31 - 37
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    A chip-level detector for optical overlapping pulse-position modulation code-division multiple-access (OPPM-CDMA) communication systems is proposed. The bit error rate of the proposed system is derived and compared to some traditional receivers under the constraints of fixed data rate and laser pulsewidth. These traditional receivers include OOK-, PPM- and OPPM-CDMA correlators. The throughput limitations of all these receivers are also presented and compared. The results reveal that a significant improvement in the performance is gained when using the proposed scheme. The throughput limitation of the OPPM-CDMA chip-level detection scheme is greater than that of an on-off keying CDMA correlation detection scheme by 7.5 times on average, when the bit error rate does not exceed 10-9 View full abstract»

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  • Performance of fast start-up equaliser for broadband indoor radio

    Page(s): 49 - 56
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    High-speed TDMA wireless networks require high data rate efficiency and fast turnaround times. In dispersive multipath channels, an equaliser is needed to remove ISI from the signal. The equaliser may be trained more quickly if its taps are preloaded with initial values. The paper describes a fast start-up equaliser which uses a power ratio approximation to estimate the initial tap values. The authors report on the performance of the fast start-up equaliser on data measured in an indoor radio environment View full abstract»

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  • Efficient algorithm for mobile multicast using anycast group

    Page(s): 14 - 18
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (492 KB)  

    The authors present a novel and efficient multicast algorithm that aims to reduce delay and communication cost for the registration between mobile nodes and mobility agents and solicitation for foreign agent services based on the mobile IP. The protocol applies anycast group technology to support multicast transmissions for both mobile nodes and home/foreign agents. Mobile hosts use anycast tunnelling to connect to the nearest available home/foreign agent where an agent is able to forward the multicast messages by selecting an anycast route to a multicast router so as to reduce the end-to-end delay. The performance analysis and experiments demonstrated that the proposed algorithm is able to enhance the performance over existing remote subscription and bidirectional tunnelling approaches regardless of the locations of mobile nodes/hosts View full abstract»

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  • Analytical model for an assured forwarding differentiated service over wireless links

    Page(s): 19 - 23
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    A weakness of the current structure of the Internet is that it does not provide the capability to support a wide range of QoS. This problem will worsen as wireless services become more popular and need to be supported using the Internet. A new model known as differentiated service (DiffServ), has been proposed by the IETF to extend the Internet to be a QoS-capable, scaleable and efficient network. Whereas DiffServ has received considerable attention from researchers, few analytical studies on supporting a wireless DiffServ have been published. The authors formulate a simple analytical model for the assured forwarding class of differentiated service over wireless links. Based on the assumption of a slowly fading channel and the use of a RIO queue management policy, they obtain expressions for performance measures that characterise the service provided to different kinds of packets. Although the model is simple, it is computationally efficient and numerical results generated using the model closely match those obtained using simulation View full abstract»

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  • DFT-based frequency estimators with narrow acquisition range

    Page(s): 1 - 7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    The authors propose new frequency estimators, with narrow frequency acquisition range which are based on the calculation of the discrete Fourier transform (DFT) of the input signal. The algorithms consist of two steps: coarse and fine search of the periodogram peak. This frequency estimator structure employing either parabolic interpolation, dichotomous search, two-rate spectral estimation or their combination for fine search allows a considerable decrease in computational load with respect to known estimators. The proposed estimators are shown to have accuracy performance close to that of the maximum likelihood (ML) estimator View full abstract»

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