By Topic

Communications, IEE Proceedings-

Issue 1 • Date Feb 2000

Filter Results

Displaying Results 1 - 10 of 10
  • ATM-level performance analysis on a DS-CDMA satellite link using DTX

    Page(s): 47 - 56
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    The authors present analysis and numerical results for ATM cell transmission over a DS-CDMA satellite link. An increase in capacity is achieved by using discontinuous transmission detection (DTX) for all on-off sources, thus exploiting the burstiness of ATM traffic. Three scenarios are analysed. System performance is expressed in terms of link efficiency, capacity and their relative increases. It is shown that the bursty nature of ATM is in this case beneficial rather than detrimental to the system capacity. Finally, the idea for the connection admission control in a satellite network that conveys ATM over DS-CDMA is presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • DBG MANs and their routing performance

    Page(s): 32 - 40
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    The authors propose the de Bruijn graph (dBG) as a topology for multi-hop lightwave networks and their hierarchical structures. Three routing algorithms that would progressively improve on the mean path length and network throughput-delay performance are studied under various topological variations and locality factors. The study shows that the performance of the bidirectional dBG networks and their hierarchical derivatives are desirable and are comparable to other types of multi-hop systems. Therefore, they are candidates for metropolitan area networks View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Annealed neural network based multiuser detector in code division multiple access communications

    Page(s): 57 - 62
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    An annealed neural network based multiuser detector in code division multiple access (CDMA) communications is presented. This detector combines features of the Hopfield neural network and simulated annealing. Unlike existing neural network based detectors, this detector does not need good initial estimates or optimal selection of network parameters. The BER performance of the proposed detector is close to the theoretical lower bound of the BER performance, especially in `near-far' situations. Extensive numerical evaluation of the proposed technique as well as various suboptimal multiuser detectors is conducted using Monte-Carlo simulation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Design of trellis decoders for block-coded modulation schemes

    Page(s): 1 - 7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    Block-coded modulation (BCM) combines bandwidth-efficient modulation techniques with error-correction capabilities to allow efficient data transmission over mobile communication channels. The main shortcoming of BCM is the complex decoding process for which, until today, mainly suboptimum decoding methods are used, because existing approaches for trellis decoders are limited to a small subset of possible BCM schemes. The authors address this shortcoming by introducing a new technique for the construction of trellis decoders for arbitrary BCM schemes. This technique is based on a new approach for the calculation of the trellis state vector and a computationally efficient recursive method for the construction of the trellis. A large number of simulation results for BCM schemes with various QAM constellations are presented, and comparisons in terms of performance and decoding complexity allow the formulation of guidelines for the choice of efficient coding schemes View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance analysis method for optical codes in coherent optical CDMA networks

    Page(s): 41 - 46
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    In the past, the selection of the address codes for coherent optical CDMA networks was carried out with the assumption that synchronisation at both sequence bit and data bit frame levels had been achieved throughout the networks at all times (totally synchronous (TS) systems). Establishing and maintaining global synchronisation requires costly and complex hardware. One way to alleviate this problem is to acquire synchronisation by coding only prior to the transmission of data bits (partially synchronous (PS) systems). It is shown that it is essential to consider the whole correlation output sequences of the correlation processes at the decoders in order to evaluate the correlation performance of address codes in the PS systems. A mathematical method is presented to simulate the correlation processes in such systems. The method is used to evaluate the PS system correlation performances of the address codes chosen previously for TS systems. It is shown that the address codes' performances in PS systems are generally worse than in TS systems, and that there is a need to design methods for selecting address codes with certain desired correlation performance levels in PS systems. The developed mathematical method will be useful for this purpose View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Intelligent location tracking strategy in PCS

    Page(s): 63 - 68
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    An alternative strategy (AS) for reducing location update signalling load has been proposed to improve the classical strategy (CS) used in the Global System for Mobile Communications (GSM). However, the AS is suitable only for long-term events and fixed movement tracks. Location tracking (paging) costs more when the mobile host (MH) changes movement habits or encounters short-term events. A novel method is proposed that aims to reduce signalling load resulting from location tracking in the above situations. The key idea is to take user recent movement information (called the paging information record) into account to determine which location area to page first. Performance evaluation has been conducted using a city area zone model that can model a realistic city area environment. Experimental results show that the method can reduce location management signalling costs by 14-55%, and 6-39% compared to CS and AS, respectively. The overhead of the approach is the additional storage space required (for storing MH profiles and paging information records) and the additional processing time. However, the overhead is insignificant in terms of today's memory capacity and processor speed, and the reduction in signalling load makes more bandwidth available View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Proportionally fair pricing: dynamics, stability and pathology

    Page(s): 23 - 31
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    A potential key to the future control on the Internet of high quality-of-service traffic is dynamic pricing of bandwidth allocations, with `proportional fairness' as one attractive possibility. For the first time to the authors' knowledge, `small-changes' and complex frequency-domain techniques (as used in classical control theory) are used to study dynamics of the relationships between bid-prices, proportionally fair bandwidth allocations and resource prices; instability, stability and convergence rates; integration from one (approximate) solution to another (accurate) solution allowing assessment of stability of major changes of traffic on the network; how coalitions of customers might distort the market by changing their bids but not getting any change in their allocation of bandwidth. Both standard proportional fairness and price-limited proportional fairness are discussed: the latter having floor prices for the resources. These prevent large unwanted allocations of bandwidth that may be needed at a later time, provide a smooth transition between low and high demands and greatly speed up dynamic allocations at low utilisation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimum delay and mean square error using a mixed crosscorrelation and constant modulus algorithm

    Page(s): 18 - 22
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    The performance of the constant modulus algorithm can suffer because of the existence of local minima with large mean squared error (MSE). The paper presents a new method to obtain the optimum MSE over all delays using a second equaliser with a mixed constant modulus and cross-correlation algorithm (CM-CCA). Proof of convergence is obtained for the noiseless case for a general symbol constellation. Simulations support the potential of the method even in noisy environments View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Design of optimum M-PSK codes for Rayleigh fading channel

    Page(s): 13 - 17
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    A methodology for the design of M-PSK codes for the Rayleigh fading channel optimised for a specific target BER is proposed, using the framework of multilevel coded modulation. The principle is to equalise the BER at each stage of a multistage decoder. An 8-PSK code is designed which exceeds the performance of the code of Seshadri and Sundberg (1992) by 2.4 dB at BER=10-3 as well as 16-PSK codes optimised for BERs of 10-3 and 10-6. No additional interleaver delay is introduced beyond that required by the channel View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Step-by-step decoding algorithm for Reed-Solomon codes

    Page(s): 8 - 12
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    A new step-by-step decoding algorithm for decoding Reed-Solomon codes over GF(2m) is presented. Based on several properties of the syndrome matrices, the new step-by-step decoding algorithm can directly determine whether every received symbol is an error locator. The detection of error location is based only on the determinant of a v×v syndrome matrix, where v is the number of errors, When an error location is found, its corresponding error value can also be determined by performing a determinant division operation between two syndrome matrices. The new decoding algorithm can significantly reduce computation complexity and improve the decoding speed compared with the conventional step-by-step decoding algorithm View full abstract»

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