By Topic

Communications, IEE Proceedings-

Issue 6 • Date Dec 2001

Filter Results

Displaying Results 1 - 13 of 13
  • Wavelength requirements and routing for multicast connections in lightpath and light-tree models of WDM networks with limited drops

    Page(s): 363 - 367
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (329 KB)  

    The wavelength requirements of a multicast connection in WDM networks are studied. The network model is an all-optical network, in which a message can be dropped (or split) only at a limited number of destination nodes along a lightpath or a light-tree, due to the power loss of dropping optical signals. The upper and lower bounds of wavelength requirements for establishing a multicast connection in various topologies of networks are presented. The optimal routing and wavelength assignment algorithms for multicast connections to achieve the minimal number of wavelengths are also described View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Application of singular value decomposition Prony (SVDP) algorithm to mobile radio imaging

    Page(s): 405 - 410
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    The robustness of the singular value decomposition Prony (SVDP) algorithm when used in processing frequency domain radio channel data is examined. Sample radio imaging results from field trials are then presented. The encouraging results suggest that the algorithm can be used to improve the spectral efficiency of a high-resolution angle of arrival (AoA) measurement system by as much as 87% View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Average SER for M-ary modulation systems with space diversity over independent and correlated Nakagami-m fading channels

    Page(s): 377 - 384
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (379 KB)  

    The average symbol error rate (SER) performance of M-ary modulation systems with space diversity over independent and correlated Nagakami-m fading channels is investigated. Simple closed-form expressions are derived, respectively, to evaluate the average SER for three modulation schemes employing both L-order maximal ratio combining (MRC) and selection combining (SC) diversity reception over independent Nagakami-/n fading channels. This includes M-ary phase shift keying (MPSK), M-ary differential PSK (MDPSK) and noncoherent M-ary frequency shift keying (MFSK). Further closed-form expressions are derived to calculate the average SER for noncoherent MFSK with dual-branch MRC, SC and switched combining (SWC) diversity reception over correlated Nagakami-m fading channels. The effects of branch correlation on the average SER are also examined. For L = 2, numerical results show that MRC outperforms SC by 1.4 dB at an average SER = 10-2 for noncoherent MFSK over an independent channel with fading parameter m = 1. For a correlated channel with correlation coefficient ρ = 0.5, the respective gain marginally increases to 1.6 dB. The error performance of dual MRC, SC and SWC over a correlated channel with m = I is degraded by approximately 0.7 dB when ρ increases from 0 to 0.5, and the degradation increases to about 2.0 dB when ρ increases from 0.5 to 0.9 View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Maximum likelihood single tone frequency estimation in a multipath channel

    Page(s): 400 - 404
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (284 KB)  

    The paper considers the maximum likelihood (ML) estimation of the frequency offset of a known signal received in a multipath channel. The ML algorithm and the Cramer-Rao lower bound are derived. An estimator possessing a low computational load is proposed whose accuracy performance is close to that of the ML estimator over a wide frequency acquisition range View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Efficient optimal soft-decision decoding for multilevel block modulation codes

    Page(s): 333 - 338
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (373 KB)  

    The multistage trellis decoding method is examined when applied to multilevel block modulation codes. It is shown how low decoding complexity can be achieved using this method, while performing maximum-likelihood decoding. As the decoding complexity involved is shown to be channel-quality dependent, the actual decoding computational burden becomes very low when the system signal-to-noise ratio is high. A way of constructing the generator matrix for multilevel block modulation codes is demonstrated, in order to build a proper trellis for decoding View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Anomaly detection in communication networks using wavelets

    Page(s): 355 - 362
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    An algorithm is proposed for network anomaly detection based on the undecimated discrete wavelet transform and Bayesian analysis. The proposed algorithm checks the wavelet coefficients across resolution levels, and locates smooth and abrupt changes in variance and frequency in the given time series, by using the wavelet coefficients at these levels. The unknown variance of the wavelet coefficients is considered as a stochastic nuisance parameter. Marginalisation is then used to remove this nuisance parameter by using three different priors: flat, Jeffreys' and the inverse Wishart distribution (scalar case). The different versions of the proposed algorithm are evaluated using synthetic data, and compared with autoregressive models and thresholding techniques. The proposed algorithm is applied to monitor events in a Dial Internet Protocol service. The results show that the proposed algorithm is able to identify the presence of abnormal network behaviour in advance of reported network anomalies View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Use of VNAs for wideband propagation measurements

    Page(s): 411 - 415
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (533 KB)  

    Vector network analyser systems have been used by many workers to measure the wideband radio channel characteristics of short-range and indoor environments. The authors provide a detailed examination of the performance of such a measurement system and show how it can be extended to a synthetic aperture technique to obtain simultaneous angle and time of arrival information. Particular regard is given to the calibration process and the various performance metrics, such as delay resolution and delay range. In addition, measurement sensitivity and dynamic range are discussed. The paper also contains illustrative results of sequential radio imaging of a deep-shadow microcellular environment View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Establishing the region of stability for an input queueing cell switch

    Page(s): 343 - 347
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (313 KB)  

    High speed variable length packet switches often use a cell switching core. For such purposes, an input queueing structure has an advantage since it imposes minimal bandwidth requirements on cell buffering memories; this leads to superior scalability of the switches. The authors consider input queueing switches in which all cells arriving at an input are queued in a single first-come-first-served queue. It is well known that, for such a simple arrangement, the maximum switch throughput can be obtained by a saturation analysis (i.e.. each queue is assumed to be infinitely backlogged and then the switch throughput is computed). The authors establish that this saturation throughput also provides a sufficient condition for stochastic stability of the input queues. It is assumed that the cell arrival process at each input is Bernoulli. Each input belongs to one of two priority classes; during output contention resolution, the head-of-the-line cell from a high priority input is given preference. The saturation throughputs of the high and low priority inputs can be computed. It is proved that if the arrival rate at each input is less than the saturation throughput then the queue lengths are stochastically stable. The major contribution of the paper is that it provides an analytical approach for such a problem; the technique can be adapted for more general problems View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • RAKE receiver using blind adaptive minimum output energy detection for DS/CDMA over multipath fading channels

    Page(s): 385 - 392
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    To achieve better tracking of time-varying channel parameters, a structure using blind adaptive minimum output energy (MOE) detection in conjunction with RAKE combining diversity for direct-sequence code-division multiple-access communications over frequency selective multipath fading channels is introduced. In this MOE-RAKE structure, the signal replicas received from multiple fading paths are first independently produced by a bank of adaptive MOE detectors and then combined by a RAKE receiver for final symbol decision. A normalised, complex-valued stochastic gradient descent algorithm is developed for the blind adaptation used in the MOE-RAKE. Simulation results show that, in the time-invariant channel, the MOE-RAKE has a performance comparable to the previously proposed MOE and outperforms the conventional RAKE. In the time-varying channel, the MOE-RAKE performs better than the other blind multiuser detection techniques. In practice, to further improve the detector performance, a hybrid scheme started with blind adaptation for the initial updates and then switched to the decision-directed algorithm is desired View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Node arrangement optimisation in linear multihop lightwave networks

    Page(s): 369 - 376
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (449 KB)  

    Virtual topologies of WDM-based multihop networks can be arranged by assigning wavelengths to tunable transceivers of nodes. An optimal node arrangement problem in multihop lightwave networks with linearly virtual topologies is considered. For a given traffic matrix, this problem is to arrange node locations to adapt traffic patterns and optimise network performance. However, the problem of node arrangement for constructing optimised linear virtual topologies has been proved as NP-complete. Two lower bounds are proposed for this problem according to the traffic-weighted mean hop distance and the maximum link flow, respectively. An efficient node arrangement algorithm, called k-ENA, is also proposed. The performance of the k-ENA algorithm is compared with the best algorithms in previous work. Simulation results indicate that the k-ENA algorithm generally yields the best solutions View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Adaptive zero-forcing blind equalisers

    Page(s): 348 - 354
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    Several adaptive blind equalisers, based on the zero-forcing (ZF) cost function, are presented. In order to estimate the mean square error (MSE) learning curve of a ZF FIR-type blind equaliser, a recursive method to predict the MSE trajectory is introduced. The ZF cost function on a decision-feedback (DF) structure is investigated and a convergence description for this DF structure is given. Finally, in order to speed-up the convergence of the proposed ZF blind equaliser, the multidimensional Newton search method is applied and the fast FIR and fast IIR type adaptive blind equalisers are derived. Some simulation examples are given to demonstrate the effectiveness of the proposed adaptive blind equalisers View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Enhanced Birkhoff-von Neumann decomposition algorithm for input queued switches

    Page(s): 339 - 342
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (238 KB)  

    The enhanced Birkhoff-von Neumann (1953) decomposition (EBVND) algorithm, a new class of scheduling arbitrators for input queued (IQ) crossbar switches that is based on the Birkhoff-von Neumann decomposition algorithm, is introduced. Theoretical analysis shows that the performance of EBVND is better than the Birkhoff-von Neumann decomposition algorithm in terms of throughput and cell delay, and can also provide rate and cell delay guarantees. Also, the weighted rate filling algorithm (WRFA), a new algorithm that can be used to construct doubly stochastic matrices from doubly substochastic matrices with less complexity and better fairness, is proposed. The wavefront Birkhoff-von Neumann decomposition (WFBVND) algorithm and its simplified version WFBVND with logN iterations (WFBVND-logN), the special cases of EBVND, are also introduced and evaluated. Simulations show that the WFBVND and WFBVND-logN algorithms have much lower average cell delay as compared to the Birkhoff-von Neumann decomposition algorithm View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • GMD: a new CDMA multiuser detection technique using an evolutionary algorithm

    Page(s): 393 - 399
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    A new multiuser detection technique, based on the genetic algorithm, has been proposed and its performance is evaluated via simulations. The technique is the genetic implementation of optimal multiuser detection (OMD) using a new concept for the search space to process and improve the outputs of matched filters in terms of suppression of multiple access interference (MAI) in a code-division multiple-access (CDMA) system. A new matrix structure is formed from the conventional detector. The elements of this matrix, using the new search space, new fitness function, and employing a chromosome-like structure, evolve to make a near-optimal solution to nearly eliminate the MAI. Unlike neural networks, the introduced genetic engine does not need a complicated training process. When it reaches an acceptable level of performance, it has the unique capability to trigger off the genetic engine, dropping the weaker individuals and continuing with a smaller group of the fittest selected solutions. The genetic multiuser detector (GMD) outperforms the well known multiuser detection techniques such as multistage detectors in terms of bit error rate. By increasing the population size of the individuals, the GMD reaches near the single user bound with much less complexity than the OMD View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.