By Topic

Communications Letters, IEEE

Issue 8 • Date Aug. 2000

Filter Results

Displaying Results 1 - 7 of 7
  • Stabilization of the randomized slotted ALOHA protocol without the use of channel feedback information

    Page(s): 249 - 251
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (51 KB)  

    This paper examines the dynamic characteristics of the randomized slotted ALOHA (RSA) protocol that is commonly employed in contention-based reservation multiaccess schemes. The average drift (or expected packet flow) is derived from a Markov chain for a finite number of single-buffer users and is used to determine the stability of the protocol. Results show that unlike many random access schemes (RSA) possesses exactly one equilibrium point even when the channel load estimate is inaccurate. However, any under-estimation in the channel load increases the equilibrium backlog (and reduces the average throughput) at a rate faster than when the channel load is overestimated. The protocol can achieve stable, nonzero throughput without the need for channel feedback information. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A new vector quantization technique for performance evaluation in frequency hopping mobile radio systems

    Page(s): 252 - 254
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (34 KB)  

    A new technique based on vector quantization (VQ) is proposed for interfacing the link-level and the system level analysis of frequency hopping (FH) mobile systems. The method represents an original solution to overcome the problem that the time scales adopted within the two analysis levels are usually different, thus discouraging a direct link between them. The VQ technique is applied, as a test case, to the study of a typical FH-GSM mobile environment. The corresponding results show excellent correlation with those achievable by means of a much more time consuming, as well as often infeasible, direct approach. View full abstract»

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

    Page(s): 255 - 257
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (85 KB)  

    We propose an adaptive channel SNR estimation algorithm required for the iterative MAP decoding of turbo decoders. The proposed algorithm uses the extrinsic values generated within the iterative MAP decoder to update the channel SNR estimate toward its optimum value per each decoder iteration or per each turbo code frame. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A simple stopping criterion for turbo decoding

    Page(s): 258 - 260
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (83 KB)  

    This article proposes a simple stopping criterion for turbo decoding that extends the existing sign change ratio (SCR) technique. The new sign difference ratio (SDR) criterion counts the sign differences between the a priori information and the extrinsic information. Unlike the SCR, it requires no extra data storage. Simulations comparing the new technique with other well known stopping criteria show that the proposed SDR scheme achieves similar performance in terms of the bit error rate (BER), frame error rate (FER), and the average number of iterations, while requiring lower complexity. A GENIE scheme is included as the limit of all possible stopping criteria. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Convergence behavior of a PS-FSE in the presence of a cyclostationary crosstalk interference

    Page(s): 261 - 263
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (79 KB)  

    The convergence and steady-state behavior of a phase-splitting fractionally spaced equalizer (PS-FSE) are analyzed in the presence of a cyclostationary crosstalk interference. It is shown that the FSE in the presence of cyclostationary crosstalk has a different eigenstructure compared to the one in the presence of stationary noise. We also show that the convergence characteristic of the PS-FSE varies depending on the relative clock phase between the signal and the crosstalk. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Impact of the beat noise on the performance of 2-D optical CDMA systems

    Page(s): 264 - 266
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (88 KB)  

    The system performance of 2-D wavelength hopping/time spreading CDMA systems is found to be limited by the occurrence of the beat noise between the components of the signal and the multiple user interference. The variance of the noise is determined and the probability of error is calculated for a general system employing asymmetric prime-hop sequences. A comparison with an idealized system neglecting the beat noise reveals that the system performance is seriously affected by the beat noise. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Comparison of a genetic algorithm with a simulated annealing algorithm for the design of an ATM network

    Page(s): 267 - 269
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (56 KB)  

    The genetic algorithm (GA) and simulated annealing algorithm (SA) are empirically compared for the problem of optimizing the topological design of a network. In addition to the usual problem of optimizing only the placement of links, in this paper the number and placement of concentrators are also decision variables for a class of problems using a real set of concentrators, links, and traffic. The average GA solution cost less than the average SA solution. View full abstract»

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

Aims & Scope

IEEE Communications Letters  is aimed at satisfying the need for rapid dissemination of information, offering a vehicle for authors to expose their results to be used in future developments. This ensures early recognition of work. 

 

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
George K. Karagiannidis
Aristotle University of Thessaloniki
Greece