Fading distribution

About: Fading distribution is a research topic. Over the lifetime, 5732 publications have been published within this topic receiving 114193 citations.

SNR estimation in Nakagami-m fading with diversity combining and its application to turbo decoding

Abstract: We propose an online signal-to-noise ratio (SNR) estimation scheme for Nakagami-m (1960) fading channels with L branch equal gain combining (EGC) diversity. We derive the SNR estimate based on the statistical ratio of certain observables over a block of data, and use the SNR estimates in the iterative decoding of turbo codes on Nakagami-m fading channels with L branch EGC diversity. We evaluate the turbo decoder performance using the SNR estimate under various fading and diversity scenarios (m = 0.5, 1, 5 and L = 1, 2, 3) and compare it with the performance using perfect knowledge of the SNR and the fade amplitudes.

Turbo code design for block fading channels

Abstract: Shannon capacity approaching codes have been extensively studied during the last decade for ergodic channels. We propose and analyze new channel multiplexing/interleaving techniques for parallel turbo codes over non-ergodic block fading channels. We reveal word error probability performance at less than 1dB from outage capacity. The achieved word error probability is almost insensitive to the code length. The race to the outage capacity limit on block fading channels is declared open.

Symbol-aided channel estimation with nonselective Rayleigh fading channels

Abstract: New algorithms are proposed to implement coherent detection of PSK signals transmitted over frequency-flat Rayleigh channels. Channel gain estimates are derived both from known symbols multiplexed with the data stream and from tentative data decisions. The performance of these algorithms is assessed by computer simulation with uncoded and trellis-coded modulation. Comparisons are also made with differentially coherent detection (DPSK) and with perfect coherent detection (corresponding to ideal knowledge of the fading process). Simulation results demonstrate that these algorithms can track adequately the severe fading fluctuations encountered on a Rayleigh channel and that their superiority over DPSK becomes impressive with fast fading.

Fading correlation and analytical performance evaluation of the space-diversity free-space optical communications system

Abstract: This paper investigates fading correlation in space-diversity free-space optical (FSO) communication systems and its effect on the link performance. We firstly evaluate the fading correlation in multiple-aperture FSO systems using wave-optics simulations. The influence of different system parameters including the link distance and aperture spacing is illustrated under realistic beam propagation conditions. In particular, we show that, at relatively large link distances where the scattering disk is much larger than the receiver aperture size, the fading correlation coefficient is almost independent of the apertures' diameter and depends only on the apertures' edge separation. To investigate the impact of fading correlation on the system's performance, we propose an analytical approach to evaluate the performance of the space-diversity FSO system over a correlated Gamma–Gamma (ΓΓ) fading channel. Our approach is based on approximating the sum of arbitrarily correlated ΓΓ random variables by an α−μ distribution. To validate the accuracy of this method, we evaluate the average bit-error-rate (BER) performance for the case of a multiple-aperture FSO system and compare it with the BER results obtained via Monte Carlo simulations.

Performance of Dual-Hop Transmissions with Fixed Gain Relays over Generalized-K Fading Channels

Abstract: We present the end-to-end performance of dual-hop wireless communication systems with non-regenerative fixed gain relays operating over independent not necessarily identically Generalized-K (KG) fading channels. New closed-form expressions are derived for the moments of the end-to-end signal-to-noise ratio (SNR), while the corresponding moment-generating function (MGF) is accurately approximated with the aid of Pade approximants theory. Useful performance criteria are studied; the average end-to-end SNR and the amount of fading, which are expressed in closed form, the average bit-error probability for several coherent, noncoherent, and multilevel modulation schemes, and the outage probability, which are both accurately approximated using the well-known MGF approach. Furthermore, novel closed-form expression is obtained for the gain of semi-blind relays over KG fading channels. The proposed mathematical analysis is complemented by various performance evaluation results, which demonstrate the accuracy of the theoretical approach.