Interference (wave propagation)

About: Interference (wave propagation) is a research topic. Over the lifetime, 26086 publications have been published within this topic receiving 321110 citations.

Aggregate Interference Modeling in Cognitive Radio Networks with Power and Contention Control

Abstract: In this paper, we present interference models for cognitive radio (CR) networks employing various interference management mechanisms including power control, contention control or hybrid power/contention control schemes. For the first case, a power control scheme is proposed to govern the transmission power of a CR node. For the second one, a contention control scheme at the media access control (MAC) layer, based on carrier sense multiple access with collision avoidance (CSMA/CA), is proposed to coordinate the operation of CR nodes with transmission requests. The probability density functions (PDFs) of the interference received at a primary receiver from a CR network are first derived numerically for these two cases. For the hybrid case, where power and contention controls are jointly adopted by a CR node to govern its transmission, the interference is analyzed and compared with that of the first two schemes by simulations. Then, the interference PDFs under the first two control schemes are fitted by log-normal PDFs to reduce computation complexity. Moreover, the effect of a hidden primary receiver on the interference experienced at the receiver is investigated. It is demonstrated that both power and contention controls are effective approaches to alleviate the interference caused by CR networks. Some in-depth analysis of the impact of key parameters on the interference of CR networks is given as well.

Interference Analysis in a Poisson Field of Nodes of Finite Area

Abstract: The research for analytical models that are able to estimate the amount of interference, which is the most important cause of performance degradation in wireless networks, has received a lot of attention over the past few years. This interest is expected to increase in the next few years due to the advent of new architectures and communication technologies, such as wireless networks sharing the same (unlicensed) frequency band, infrastructureless wireless networks, and ultrawideband (UWB) systems. In this paper, we try to overcome some of the limitations of the existing interference models and propose an analytical framework for the evaluation of any statistical moment of the interference provided by a Poisson field of nodes located on a given region of limited area. The propagation environment we consider is characterized by a deterministic distance-dependent path-loss model and log-normal shadowing. The present methodology can be used to provide a fast and accurate evaluation of the amount of interference in many practical situations. Exact closed-form expressions are given for some specific cases.

Effect of mutual coupling on the interference rejection capabilities of linear and circular arrays in CDMA systems

Abstract: This paper is concerned with assessing the interference rejection capabilities of linear and circular array of dipoles that can be part of a base station of a code-division multiple-access cellular communication system. The performance criteria for signal-to-interference ratio (SIR) improvement employed in this paper is the spatial interference suppression coefficient. We first derive an expression for this figure of merit and then analyze and compare the SIR performance of the two types of arrays. For a linear array, we quantitatively assess the degradation in SIR performance as we move from array broadside to array end-fire direction. In addition, the effect of mutual coupling is taken into account.

Rough surface interferometry at 10.6 µm

Abstract: An IR Twyman-Green interferometer is described. It uses a cw CO2 laser as a light source operating at a 10.6-μm wavelength. Theoretical analysis and experimental measurements of the relationship between the contrast of the interference fringes and the rms roughness of test surfaces are discussed. Interferometric testing results and special alignment methods are shown for rough surface optics.