Detection statistics for a coherent laser radar are substantially different from those of a direct detection laser radar. Direct detection ladar detection statistics vary depending upon the detection mode (i.e., photon-counting vs. continuous direct detection). Speckle noise also impacts the detection statistics. For a single-pixel single-frequency single-polarization coherent detection transce...

Techniques have been proposed to estimate unknown antenna impedance due time-varying near-field loading conditions at multiple-input single-output (MISO) receivers. However, it remains unclear when a change occurs and estimation becomes necessary. In this letter, we address problem by formulating as hypothesis test. Our contributions include deriving generalized likelihood-ratio test (GLRT) det...

The link layer of an optical direct-detection code-division multiple-access (CDMA) packet network is considered. Two different protocols that need pretransmission coordination are proposed. A variation of the second protocol that does not need pretransmission coordination is discussed. Both system throughput and average packet delay are derived and investigated for two different receiver models...

Intensity modulation and direct detection (IM/DD) is a cost-effective optical communication strategy which finds wide applications in fiber communication, free-space optical communication, and indoor visible light communication. In IM/DD, orthogonal frequency division multiplexing (OFDM), originally employed in radio frequency communication, is considered as a strong candidate solution to comba...

We investigate our ability to determine the mean position, or centroid, of a linear array equally-bright incoherent point sources light, whose continuum limit is problem estimating center uniformly-radiating object. consider two receivers: an image-plane ideal direct-detection imager and receiver that employs Hermite-Gaussian (HG) Spatial-mode Demultiplexing (SPADE) in image plane, prior shot-n...

Refractive index turbulence causes random power fluctuations in optical communication systems, making communication through the atmosphere difficult. This same phenomenon makes the stars twinkle at night, and pavement shimmer on a hot summer day. True to the old adage, “don’t put all your eggs in one basket,” we examine laser communication systems that use multiple transmit and receive aperture...

We demonstrate the effectiveness of multiuser detection for an ultra-wideband (UWB) pulse based direct sequence spread spectrum system using code division multiple access. Extensive simulations were run using channel soundings of the 2–8 GHz band collected in a residential setting and characterized by a high level of multipath fragmentation. We show that the adaptive minimum mean square error (...

In this paper, we investigate the use of nonlinear distortion of the electrical post-detection signal in order to design simple, yet very effective, maximum likelihood sequence detection (MLSD) receivers for optical communications with direct photo-detection. This distortion enables the use of standard Euclidean branch metrics in the Viterbi algorithm which implements MLSD. Our results suggest ...

Joint Detection is used to reduce both inter-symbol interference (ISI) and multiple-access interference (MAI) in the Time Division-Synchronous Code Division Multiple Access (TDSCDMA) system. Conventional rake receivers only consider desired user’s signal, while joint detection receivers take into account both desired user’s signal and other user signals for interference cancellation. If the tra...