Fading distribution

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

Distortion Minimization in Gaussian Layered Broadcast Coding with Successive Refinement

Abstract: A transmitter without channel state information (CSI) wishes to send a delay-limited Gaussian source over a slowly fading channel. The source is coded in superimposed layers, with each layer successively refining the description in the previous one. The receiver decodes the layers that are supported by the channel realization and reconstructs the source up to a distortion. The expected distortion is minimized by optimally allocating the transmit power among the source layers. For two source layers, the allocation is optimal when power is first assigned to the higher layer up to a power ceiling that depends only on the channel fading distribution; all remaining power, if any, is allocated to the lower layer. For convex distortion cost functions with convex constraints, the minimization is formulated as a convex optimization problem. In the limit of a continuum of infinite layers, the minimum expected distortion is given by the solution to a set of linear differential equations in terms of the density of the fading distribution. As the bandwidth ratio b (channel uses per source symbol) tends to zero, the power distribution that minimizes expected distortion converges to the one that maximizes expected capacity. While expected distortion can be improved by acquiring CSI at the transmitter (CSIT) or by increasing diversity from the realization of independent fading paths, at high SNR the performance benefit from diversity exceeds that from CSIT, especially when b is large.

Gaussian codes and weighted nearest neighbor decoding in fading multiple-antenna channels

Abstract: We investigate the fading multiple-antenna channel. The decoder is assumed to possess imperfect channel fading information. A modified nearest neighbor decoder with an innovative weighting factor is introduced and an expression for the generalized mutual information (GMI), the achievable rate, is obtained. We show that under certain conditions the achievable rate is equivalent to that of a fading multiple-antenna Gaussian channel where fading is known to the receiver and is equal to the channel estimation, and where noise is due to both the channel noise and the channel estimation error. We show that for our communication scheme, the minimum mean square error (MMSE) channel estimator is optimal in the sense that it achieves the highest value of GMI, and hence the highest communication rate. Additionally, a training based multiple-input multiple-output (MIMO) scheme in a block-fading channel is investigated and it is shown that the number of degrees of freedom depends on the signal-to-noise ratio (SNR).

Performance of Two-Way Opportunistic Relaying With Analog Network Coding Over Nakagami- $m$ Fading

Abstract: In this paper, we evaluate the performance of an outage-optimal two-way opportunistic relaying (TWOR) scheme with analog network coding (ANC) over independent but not necessarily identically distributed (i.ni.d.) Nakagami-m fading channels. Considering arbitrary integer-valued fading parameters over the two hops, we derive an exact outage expression that is applicable for the entire range of signal-to-noise ratio (SNR). For better insights, we provide simple closed-form expressions at high SNR for bounds on the outage probability and on the ergodic sum-rate of the scheme. We show that the achievable diversity order is equal to the minimum of the per-hop fading parameters times the number of relaying candidates. Numerical and simulation results are presented to illustrate the theoretical analysis and the effects of the various Nakagami fading conditions on the overall system performance.

A statistical model for indoor office wireless sensor channels

Abstract: Sensor networks and ad-hoc networks, where nodes inter-communicate without fixed infrastructure, have recently attracted interest due to potential use in industrial, environmental, and safety-related applications. The fading statistics of the propagation channels between sensor nodes are essential to determine the possible data rate, outage, and latency of sensor networks. This paper presents (to the best of our knowledge) the first in-depth analysis, based on measurements, of the propagation channels between typical sensor node locations in office environments. We find that the amplitude fading distribution can be characterized as Ricean. The Rice factor is analyzed as a function of distance and it is determined that it is not a monotonically decreasing function. Even in pure line-of-sight situations, Rice factors show a random behavior and are on the order of 10 or less. We propose models for the small- and large-scale fading correlation. A simulation model based on our analysis is also provided. Our results have relevance for the analysis of bit error rates and diversity order in clustered sensor networks.

Throughput estimation of ARQ protocols for a Rayleigh fading channel using fade- and interfade-duration statistics

Abstract: Error detection combined with automatic repeat request retransmission is used to provide reliable digital data transmission over a communication channel. The throughput for a system using go-back-N or selective-repeat protocols with Rayleigh fading in both directions of transmission is approximated by using fade- and interfade-duration statistics of a multipath channel. Results indicate that for a slow-fading channel (e.g. fading rate=1.34 Hz), the throughput of go-back-N is only slightly inferior to that of selective-repeat, mainly due to the burstiness of the channel bit errors. >