Fading distribution

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

The ALOHA systems in shadowed mobile radio channels with slow or fast fading

Abstract: The influence of receiver capture on the performance of the ALOHA protocol in the presence of shadowing is investigated. The combined effect of Rayleigh fading, log-normal shadowing, and spatial distribution of mobile users is also studied. It is shown that shadowing is similar to fading and near/far phenomena, in that it makes the capture effect possible and provides ALOHA systems with substantial improvements in throughput. It is also confirmed that the superimposed Rayleigh fading, log-normal shadowing, and spatial distribution can further enhance the capture effect, resulting in a ALOHA system with higher throughput. The fast fading effect in ALOHA systems is explored. A very fast fading case is examined which may be considered to be equivalent to interleaving in slow fading. It is found that an ALOHA system under fast fading conditions also benefits from the capture results in higher throughput. >

On the multicell processing capacity of the cellular MIMO uplink channel in correlated rayleigh fading environment

Abstract: In the context of cellular systems, it has been shown that multicell processing can eliminate inter-cell interference and provide high spectral efficiencies with respect to traditional interference-limited implementations. Moreover, it has been proved that the multiplexing sum-rate capacity gain of multicell processing systems is proportional to the number of base station (BS) antennas. These results have been also established for cellular systems, where BSs and user terminals (UTs) are equipped with multiple antennas. Nevertheless, a common simplifying assumption in the literature is the uncorrelated nature of the Rayleigh fading coefficients within the BSUT MIMO links. In this direction, this paper investigates the ergodic multicell-processing sum-rate capacity of the Gaussian MIMO cellular multiple-access channel in a correlated fading environment. More specifically, the multiple antennas of both BSs and UTs are assumed to be correlated according to the Kronecker product model. Furthermore, the current system model considers Rayleigh fading, uniformly distributed UTs over a planar coverage area and power-law path loss. Based on free probabilistic arguments, the empirical eigenvalue distribution of the channel covariance matrix is derived and it is used to calculate both optimal joint decoding and minimum mean square error (MMSE) filtering capacity. In addition, numerical results are presented, where the per-cell sum-rate capacity is evaluated while varying the cell density of the system, as well as the level of fading correlation. In this context, it is shown that the capacity performance is greatly compromised by BS-side correlation, whereas UT-side correlation has a negligible effect on the system's performance. Furthermore, MMSE performance is shown to be greatly suboptimal but more resilient to fading correlation in comparison to optimal decoding.

Robust uncorrelated bit extraction methodologies for wireless sensors

Abstract: This paper presents novel methodologies which allow robust secret key extraction from radio channel measurements which suffer from real-world non-reciprocities and a priori unknown fading statistics. These methodologies have low computational complexity, automatically adapt to differences in transmitter and receiver hardware, fading distribution and temporal correlations of the fading signal to produce secret keys with uncorrelated bits. Moreover, the introduced method produces secret key bits at a higher rate than has previously been reported. We validate the method using extensive measurements between TelosB wireless sensors.

Diversity analysis of space-time coding in cascaded Rayleigh fading channels

Abstract: Cascaded Rayleigh distribution is used to model multipath fading in mobile-to-mobile communication scenarios and provides a better fit to experimental data in such scenarios compared to the conventional Rayleigh channel model. In this letter, we derive an exact expression for the pairwise error probability (PEP) of space-time trellis codes over the cascaded Rayleigh fading channel, which is in the form of a simple single finite-range integral. Through the derived PEP expression, we present the maximum diversity order achievable over such channels and demonstrate the performance degradation in comparison to conventional Rayleigh channels. Monte-Carlo simulations are further demonstrated to confirm the analytical results.

Weibull-gamma composite distribution: alternative multipath/shadowing fading model

Abstract: The Weibull-gamma (WG) distribution, which is appropriate for modelling fading environments when multipath is superimposed on shadowing, is introduced and studied. For this composite distribution the probability density, cumulative distribution, characteristic functions and the moments are derived in closed form. Furthermore, the average bit error and outage probabilities of a receiver operating over WG fading channels are assessed and compared with the corresponding performances obtained using other composite distributions.