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Lajos Hanzo - One of the best experts on this subject based on the ideXlab platform.

  • optimum mode switching assisted constant power single and multicarrier Adaptive Modulation
    IEEE Transactions on Vehicular Technology, 2003
    Co-Authors: Byoungjo Choi, Lajos Hanzo
    Abstract:

    A set of optimum mode-switching levels is derived for a generic constant-power Adaptive-Modulation scheme based on a closed-form expression of the average bit error ratio (BER) and the average bits-per-symbol (BPS) throughput of the Adaptive-Modulation scheme. This results in a constant BER, variable-throughput arrangement. The corresponding BPS throughput performance and the achievable signal-to-noise ratio (SNR) gain are investigated for the optimum mode-switching assisted constant-power Adaptive-Modulation schemes employing various diversity schemes, including maximal ratio combining (MRC) receive-antenna diversity, a two-dimensional RAKE receiver, as well as transmit-diversity aided space-time (ST) coding, when communicating over various fading scenarios. The BPS throughput of our constant-power Adaptive quadrature amplitude Modulation (AQAM) scheme approaches the throughput of variable-power variable-rate AQAM within 1 dB. However, the achievable throughput gain of the Adaptive-Modulation scheme, in comparison to conventional fixed-mode modems, is substantially reduced as the diversity order of the receiver is increased. Hence, Adaptive Modulation constitutes a lower complexity alternative to multiple-transmitter and receiver-based systems when considering the range of techniques that can be used for mitigating the effects of the channel-quality fluctuations imposed by wireless channels.

  • DeModulation level selection in Adaptive Modulation
    Electronics Letters, 1996
    Co-Authors: J.m. Torrance, Lajos Hanzo
    Abstract:

    A novel, uneven protection, Modulation scheme is proposed for the transmission of control symbols in Adaptive Modulation. Theoretical and simulated results for transmissions over Rayleigh channels are presented and compared with those obtained using other techniques. A 5dB signal-to-noise(SNR) improvement is recorded for computer data transmission.

  • Optimum mode-switching assisted Adaptive Modulation
    GLOBECOM'01. IEEE Global Telecommunications Conference (Cat. No.01CH37270), 1
    Co-Authors: Byoungjo Choi, Lajos Hanzo
    Abstract:

    Adaptive Modulation techniques combat fading by employing a suitable Modulation mode depending on the instantaneous channel conditions for improving the Bit Error Rate (BER) performance or the average throughput. Based on a generic model of constant-power Adaptive Modulation, exact closed form expressions of the average BER and the average throughput are derived, when employing square Quadrature Amplitude Modulation (QAM) or Phase Shift Keying (PSK) as the constituent Modulation modes, operating over a Nakagami fading channel. The optimum Modulation-mode switching levels, achieving the highest possible throughput under the constraint of the average BER, are obtained using the Lagrangian optimisation method. Adaptive Modulation employing the optimum switching levels shows a superior performance, while maintaining a constant average BER.

Byoungjo Choi - One of the best experts on this subject based on the ideXlab platform.

  • optimum mode switching assisted constant power single and multicarrier Adaptive Modulation
    IEEE Transactions on Vehicular Technology, 2003
    Co-Authors: Byoungjo Choi, Lajos Hanzo
    Abstract:

    A set of optimum mode-switching levels is derived for a generic constant-power Adaptive-Modulation scheme based on a closed-form expression of the average bit error ratio (BER) and the average bits-per-symbol (BPS) throughput of the Adaptive-Modulation scheme. This results in a constant BER, variable-throughput arrangement. The corresponding BPS throughput performance and the achievable signal-to-noise ratio (SNR) gain are investigated for the optimum mode-switching assisted constant-power Adaptive-Modulation schemes employing various diversity schemes, including maximal ratio combining (MRC) receive-antenna diversity, a two-dimensional RAKE receiver, as well as transmit-diversity aided space-time (ST) coding, when communicating over various fading scenarios. The BPS throughput of our constant-power Adaptive quadrature amplitude Modulation (AQAM) scheme approaches the throughput of variable-power variable-rate AQAM within 1 dB. However, the achievable throughput gain of the Adaptive-Modulation scheme, in comparison to conventional fixed-mode modems, is substantially reduced as the diversity order of the receiver is increased. Hence, Adaptive Modulation constitutes a lower complexity alternative to multiple-transmitter and receiver-based systems when considering the range of techniques that can be used for mitigating the effects of the channel-quality fluctuations imposed by wireless channels.

  • Optimum mode-switching assisted Adaptive Modulation
    GLOBECOM'01. IEEE Global Telecommunications Conference (Cat. No.01CH37270), 1
    Co-Authors: Byoungjo Choi, Lajos Hanzo
    Abstract:

    Adaptive Modulation techniques combat fading by employing a suitable Modulation mode depending on the instantaneous channel conditions for improving the Bit Error Rate (BER) performance or the average throughput. Based on a generic model of constant-power Adaptive Modulation, exact closed form expressions of the average BER and the average throughput are derived, when employing square Quadrature Amplitude Modulation (QAM) or Phase Shift Keying (PSK) as the constituent Modulation modes, operating over a Nakagami fading channel. The optimum Modulation-mode switching levels, achieving the highest possible throughput under the constraint of the average BER, are obtained using the Lagrangian optimisation method. Adaptive Modulation employing the optimum switching levels shows a superior performance, while maintaining a constant average BER.

Chang Heon Lim - One of the best experts on this subject based on the ideXlab platform.

Hong-chuan Yang - One of the best experts on this subject based on the ideXlab platform.

  • WCNC - Transmission Time Analysis for Adaptive Modulation System over Block Fading Channels
    2017 IEEE Wireless Communications and Networking Conference (WCNC), 2017
    Co-Authors: Wen Jing Wang, Hong-chuan Yang
    Abstract:

    In this paper, we investigate the statistics of packet transmission time of wireless transmission systems employing Adaptive Modulation. Unlike traditional transmission systems, where the transmission time of a fixed-size packet is typically regarded as a constant, the transmission time of Adaptive Modulation systems depends on the channel realization as the transmission rate varies with the fading channel conditions. In this paper, we derive the exact statistical distribution of packet transmission time for Adaptive Modulation systems over block fading channels. The exact expressions of the probability mass function (PMF) and cumulative distribution function (CDF) of packet transmission time are obtained for both slow and fast fading scenarios. We further present an approximate PMF for fast fading scenario to reduce the computation complexity. Selected numerical results are presented to illustrate the mathematical formulation.

Svante Signell - One of the best experts on this subject based on the ideXlab platform.

  • Adaptive Modulation and power allocation for OSTBC
    2009 7th International Conference on Information Communications and Signal Processing (ICICS), 2009
    Co-Authors: Jinliang Huang, Svante Signell
    Abstract:

    Adaptive Modulation and power allocation schemes have been widely used in multiple-input multiple-output (MIMO) systems to enhance spectral efficiency while maintaining bit error ratio (BER) to a target level. We derive the spectral efficiency of orthogonal space-time block codes (OSTBC) that can be achieved by applying Adaptive Modulation and power allocation. Compared to non-Adaptive power scheme, the Adaptive power allocation can achieve substantial gain in the spectral efficiency. Moreover, channel estimation errors are taken into account and the impact on the spectral efficiency is investigated.