Fading distribution

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

Optimal Hop Distance and Power Control for a Single Cell, Dense, Ad Hoc Wireless Network

Abstract: We consider a dense, ad hoc wireless network, confined to a small region. The wireless network is operated as a single cell, i.e., only one successful transmission is supported at a time. Data packets are sent between source-destination pairs by multihop relaying. We assume that nodes self-organize into a multihop network such that all hops are of length d meters, where d is a design parameter. There is a contention-based multiaccess scheme, and it is assumed that every node always has data to send, either originated from it or a transit packet (saturation assumption). In this scenario, we seek to maximize a measure of the transport capacity of the network (measured in bit-meters per second) over power controls (in a fading environment) and over the hop distance d, subject to an average power constraint. We first motivate that for a dense collection of nodes confined to a small region, single cell operation is efficient for single user decoding transceivers. Then, operating the dense ad hoc wireless network (described above) as a single cell, we study the hop length and power control that maximizes the transport capacity for a given network power constraint. More specifically, for a fading channel and for a fixed transmission time strategy (akin to the IEEE 802.11 TXOP), we find that there exists an intrinsic aggregate bit rate (\Theta_{opt} bits per second, depending on the contention mechanism and the channel fading characteristics) carried by the network, when operating at the optimal hop length and power control. The optimal transport capacity is of the form d_{opt}(\bar{P_t}) \times \Theta_{opt} with d_{opt} scaling as \bar{P_t}^{{1\over \eta}}, where \bar{P_t} is the available time average transmit power and \eta is the path loss exponent. Under certain conditions on the fading distribution, we then provide a simple characterization of the optimal operating point. Simulation results are provided comparing the performance of the optimal strategy derived here with some simple strategies for operating the network.

Space-time correlation modeling of multielement antenna systems in mobile fading channels

Abstract: For the analysis and design of multielement antenna systems in mobile fading channels, we need a model for the space-time cross correlation among the links of the multiple-input multiple-output (MIMO) channel. We propose a general space-time cross correlation function for narrowband Rayleigh fading MIMO channels, where various parameters of interest such as angle spreads at the base station and the user, the distance between the base station and the user, mean directions of the signal arrivals, array configurations, and Doppler spread are all taken into account. The new space-time cross correlation function includes all the relevant parameters of the MIMO narrowband Rayleigh fading channel in a clean compact form, suitable for both simulation and mathematical analysis. It also covers many known correlation models as special cases. We demonstrate the utility of the new space-time correlation model by clarifying the limitations of a widely-accepted correlation model for MIMO fading channels.

Systems and methods for wireless communication using polarization diversity

Abstract: According to various embodiments, systems and methods are provided for improving signal quality and signal reliability over wireless communication using polarization diversity. Some embodiments use polarization diversity on a wireless channel to address and compensate for fading conditions such as non-frequency selective fading (also referred to as power fading, attenuation fading, and flat fading) and frequency selective fading (also referred to as multipath fading and dispersive fading). For example, some embodiments utilize a horizontal signal and a vertical signal on the same wireless channel when wirelessly communicating data between a transmitter and a receiver to address a fading condition.

Dual-Hop Cognitive Amplify-and-Forward Relaying Networks Over $\eta-\mu$ Fading Channels

Abstract: This paper presents a thorough performance analysis of dual-hop cognitive amplify-and-forward (AF) relaying networks under spectrum-sharing mechanism over independent nonidentically distributed (i.n.i.d.) $\eta-\mu$ fading channels. In order to guarantee the quality of service (QoS) of primary networks, both the maximum tolerable peak interference power $\mathcal{Q}$ at the primary users (PUs) and the maximum allowable transmit power $\mathcal{P}$ at the secondary users (SUs) are considered to constrain transmit power at the cognitive transmitters. For integer-valued fading parameters, a closed-form lower bound for the outage probability (OP) of the considered networks is obtained. Moreover, assuming arbitrary-valued fading parameters, the lower bound in integral form for the OP is derived. In order to obtain further insights into the OP performance, asymptotic expressions for the OP at high SNRs are derived, from which the diversity/coding gains and the diversity–multiplexing gain tradeoff (DMT) of the secondary network can be readily deduced. It is shown that the diversity gain and the DMT are solely determined by the fading parameters of the secondary network, whereas the primary network only affects the coding gain. The derived results include several others available in previously published studies as special cases, such as those for Nakagami- $m$ fading channels. In addition, performance evaluation results have been obtained by Monte Carlo computer simulations, which have verified the accuracy of the theoretical analysis.