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.

Phase-controlled light switching at low light levels

Abstract: We report experimental observations of interference between three-photon and one-photon excitations, and phase control of light attenuation and/or transmission in a four-level system. Either constructive or destructive interferences can be obtained by varying the phase and/or frequency of a weak control laser. The interference enables absorptive switching of one field by another field at different frequencies and ultralow light levels.

Time-resolved dual-beam two-photon interferences with high visibility.

Abstract: We perform a two-photon interference experiment in a Michelson interferometer with photon pairs produced by spontaneous parametric down-conversion. The interferometer is set to a path difference much larger than the coherence length of the light field. Application of a time-resolved coincidence detection scheme reveals two-photon interference fringes with a visibility of 87%. This high visibility clearly demonstrates the nonclassical nature of the observed interference and should allow further spin-free tests of Bell's inequalities.

Multiple access using two sets of orthogonal signal waveforms

Abstract: We present a new multiple access concept which allows to accommodate more than N users on a channel of NW Hz bandwidth, where W Hz is the bandwidth of the individual user signals. It makes use of two sets of orthogonal signal waveforms, one for the first N users and one for the additional users. An iterative multistage detection technique is used to cancel interference between the two sets of users. At each stage of the detection process, the best estimate of the multiuser interference is synthesized using the decisions available from the previous stages, and this interference is subtracted from the user signals of interest before entering them to a threshold detector. The new concept is described using orthogonal code-division multiple access and time division multiple access as the two sets of signal waveforms, but we also briefly outline how it can be generalized to other orthogonal sets.

Exact bit error rate analysis of TH-PPM UWB systems in the presence of multiple-access interference

Abstract: A new method is proposed for precisely calculating the bit error probability of a time-hopping binary pulse position modulation ultra-wideband system with multiple access interference. The analytical expression is validated by simulation and used to assess the inaccuracy of the Gaussian approximation.

Spatial Interference Cancellation for Multiantenna Mobile Ad Hoc Networks

Abstract: Interference between nodes is a critical impairment in mobile ad hoc networks. This paper studies the role of multiple antennas in mitigating such interference. Specifically, a network is studied in which receivers apply zero-forcing beamforming to cancel the strongest interferers. Assuming a network with Poisson-distributed transmitters and independent Rayleigh fading channels, the transmission capacity is derived, which gives the maximum number of successful transmissions per unit area. Mathematical tools from stochastic geometry are applied to obtain the asymptotic transmission capacity scaling and characterize the impact of inaccurate channel state information (CSI). It is shown that, if each node cancels interferers, the transmission capacity decreases as as the outage probability vanishes. For fixed , as grows, the transmission capacity increases as where is the path-loss exponent. Moreover, CSI inaccuracy is shown to have no effect on the transmission capacity scaling as vanishes, provided that the CSI training sequence has an appropriate length, which we derive. Numerical results suggest that canceling merely one interferer by each node may increase the transmission capacity by an order of magnitude or more, even when the CSI is imperfect.