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.

Direct measurement of transverse coherence length of hard X rays from interference fringes

Abstract: We propose a simple interferometric technique for hard x-ray spatial coherence characterization, recording a Fresnel interference pattern produced by a round fiber or a slit. We have derived analytical formulas that give a direct relation between a visibility of interference fringes and either the source size or the transverse coherence length. The technique is well suited to third-generation synchrotron radiation sources and was experimentally applied to determine the spatial coherence length and the source size at the European Synchrotron Radiation Facility.

Symbol-Level Multiuser MISO Precoding for Multi-Level Adaptive Modulation

Abstract: Symbol-level precoding is a new paradigm for multiuser multiple-antenna downlink systems aimed at creating constructive interference among transmitted data streams. This can be enabled by designing the precoded signal of the multiantenna transmitter on a symbol level, taking into account both channel state information and data symbols. Previous literature has studied this paradigm for Mary phase shift keying modulations by addressing various performance metrics, such as power minimization and maximization of the minimum rate. In this paper, we extend this to generic multi-level modulations, i.e., Mary quadrature amplitude modulation by establishing connection to PHY layer multicasting with phase constraints. Furthermore, we address the adaptive modulation schemes which are crucial in enabling the throughput scaling of symbol-level precoded systems. In this direction, we design the signal processing algorithms for minimizing the required power under per-user signal to interference noise ratio or goodput constraints. Extensive numerical results show that the proposed algorithm provides considerable power and energy efficiency gains, while adapting the employed modulation scheme to match the requested data rate.

On the Degrees of Freedom of $K$ -User SISO Interference and X Channels With Delayed CSIT

Abstract: The K-user single-input single-output (SISO) additive white Gaussian noise (AWGN) interference channel and 2×K SISO AWGN X channel are considered, where the transmitters have delayed channel state information (CSI) through noiseless feedback links. Multiphase transmission schemes are proposed for both channels which possess novel ingredients, namely, multiphase partial interference nulling, distributed interference management via user scheduling, and distributed higher order symbol generation. The achieved degree-of-freedom (DoF) values are greater than the best previously known DoFs for both channels with delayed CSI at the transmitters.

Two different philosophies in CDMA-a comparison

Abstract: There has been considerable interest recently in the subject of multiuser interference cancellation techniques for CDMA wireless systems. It is widely believed that a system design using interference cancellation techniques has considerably better capacity than the design methodology adopted in the IS-95 CDMA cellular standard, which does not use such techniques. We examine this issue, and in particular focus on linear interference cancellation techniques. Linear techniques are simpler and require fewer assumptions, such as accurate knowledge of amplitude and phase information of the users to be canceled, than nonlinear interference cancellers. However, linear interference cancellation techniques require a fundamentally different CDMA system design philosophy than IS-95. In IS-95, the coding gain from error control codes bears the burden of handling interference, while a linear canceller uses the dimensional separation of users. This paper compares and contrasts the two design philosophies. Our comparison is based on overall user capacity (defined as the number of users per Hz per unit area) as well as robustness and fairness. The focus of the paper is on the mobile-user to base station reverse link which is modeled by the classical many-to-one multiple-access problem.

Devices based on surface plasmon interference filters

Abstract: Devices based on surface plasmon filters having at least one metal-dielectric interface to support surface plasmon waves. A multi-layer-coupled surface plasmon notch filter is provided to have more than two symmetric metal-dielectric interfaces coupled with one another to produce a transmission spectral window with desired spectral profile and bandwidth. Such notch filters can form various color filtering devices for color flat panel displays.