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Communications Letters, IEEE

Issue 2 • Date February 1999

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Displaying Results 1 - 10 of 10
  • Design of user codes in QS-CDMA systems for MUI elimination in unknown multipath

    Publication Year: 1999 , Page(s): 25 - 27
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (163 KB)  

    Low-complexity quasi synchronous CDMA systems are derived for eliminating multi-user interference (MUI) completely in the presence of unknown and even rapidly varying multipath. They rely on judiciously designed precomputable user codes and offer a generalization of orthogonal frequency division multiplexing, especially valuable when carrier frequency errors and Doppler effects are present. View full abstract»

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  • Residue number system arithmetic assisted M-ary modulation

    Publication Year: 1999 , Page(s): 28 - 30
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (125 KB)  

    A residue number system based M-ary modem is proposed and its performance is evaluated over Gaussian channels. When one or two redundant moduli are employed, a signal-to-noise ratio gain of 1.2-2 dB was achieved for a 16-ary, 32-ary and 37-ary modem, respectively, at a bit error rate of 10/sup -6/. View full abstract»

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  • Approximate analysis of coupled queueing in ATM networks

    Publication Year: 1999 , Page(s): 31 - 33
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (99 KB)  

    We discuss a scheduling discipline for multiclass traffic in asynchronous transfer mode network nodes. The scheduler provides minimum bandwidth guarantees for each class of traffic and is well suited for high-speed implementation. The scheme is a modification of static head-of-line priority queueing, and was originally presented in a slightly different form by Huang and Wu (1993). We begin by considering a system with two queues which is analyzed by decoupling the system into separate M/G/1 queues. The analysis provides a very good estimate for the mean response time of customers in each queue. We also demonstrate the applicability of the analysis to a system with n/spl ges/2 queues. View full abstract»

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  • A note on the convergence of asynchronous greedy algorithm with relaxation in a multiclass queueing environment

    Publication Year: 1999 , Page(s): 34 - 36
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (113 KB)  

    In this letter, we consider the convergence of an asynchronous greedy algorithm with relaxation for Nash equilibrium in a noncooperative multiclass queueing environment. The process of an asynchronous greedy algorithm is equivalent to the iteration of the Jacobi method in solving a linear system. However, it has been proved that the algorithm converges only for some particular range of queueing parameters. Here we propose the asynchronous greedy algorithm with relaxation, which is in principle equivalent to solving a linear system by the Jacobi method with relaxation. We propose also some relaxation parameters such that our algorithm converges very fast. View full abstract»

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  • Impact of amplifier nonlinearities on OFDM transmission system performance

    Publication Year: 1999 , Page(s): 37 - 39
    Cited by:  Papers (107)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (119 KB)  

    The power spectral density of an orthogonal frequency-division multiplexing (OFDM) signal after a saturated high-power amplifier (HPA) is analytically derived. The distortion of the HPA-processed OFDM signal is defined, and its power spectrum is computed. The spectra of the signal and of the distortion are used to get an accurate estimate of the bit-error rate of an OFDM transmission system and to derive compensation at the receiver, which leads to performance improvement. View full abstract»

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  • Adaptive channel estimation for multichannel MLSE receivers

    Publication Year: 1999 , Page(s): 40 - 42
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (118 KB)  

    The performance of multichannel coherent maximum-likelihood sequence estimation (MLSE) reception in the presence of co-channel interference is limited by the channel estimation accuracy. An adaptive channel estimation approach is developed which improves the performance through interference cancellation. Significant performance gains (up to 8 dB) are demonstrated for the Digital Advanced Mobile Phone Service (D-AMPS) (IS-136) digital cellular system. View full abstract»

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  • An error probability formula for noncoherent orthogonal binary FSK with dual diversity on correlated Rician channels

    Publication Year: 1999 , Page(s): 43 - 45
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (128 KB)  

    We derive a novel error probability formula for noncoherent detection of orthogonal binary frequency-shift keying with dual diversity and equal gain combining in the presence of slow, correlated, Rician time-selective fading. Numerical results indicate that: (1) fading correlation may produce a substantial performance loss and (2) the error performance of the noncoherent detector improves uniformly as the intensity of the line-of-sight signal component increases. View full abstract»

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  • A context-tree based model for quantized fading

    Publication Year: 1999 , Page(s): 46 - 48
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (98 KB)  

    Fading is modeled by applying context tree pruning (CTP) to the sequence of fading states that results from quantizing a sequence of real-valued fading measurements. There results a family of finite state Markov chains of increasing order that represent the channel with increasing fidelity. A fading state may be the union of chain states. A particular model may be chosen from that family according to an application-specific criterion. The resulting models facilitate analysis and simulation of wireless systems that exploit channel memory. An example criterion compares each model's fading state sojourn time statistics with those of the original sequence. View full abstract»

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  • On the error exponent for memoryless flat fading channels with channel-state-information feedback

    Publication Year: 1999 , Page(s): 49 - 51
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (102 KB)  

    We derive the random coding error exponent for the time-independent flat fading channel with perfect knowledge of the channel state information (CSI) at both the receiver and the transmitter. That is, the CSI is feedback from the receiver to the transmitter. In such a situation, the transmitter is capable of optimizing the power allocation of the transmitted signal according to the fading state in order to obtain, for our case, the best error exponent. The power scheme obtained here is different from the water-pouring one, which is known to maximize the channel capacity. View full abstract»

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  • An adaptive ARQ scheme with packet combining for time varying channels

    Publication Year: 1999 , Page(s): 52 - 54
    Cited by:  Papers (13)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (78 KB)  

    The dependence of the efficiency of hybrid type-II ARQ schemes on the packet size in the context of a simple packet combining scheme is discussed. A simple algorithm for adopting the optimum packet size according to the channel bit error rate (BER) is presented. Also, a very simple method of estimating the channel BER is provided. View full abstract»

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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. 

 

 

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Meet Our Editors

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