3,045 research outputs found
A Statistical Analysis of Multipath Interference for Impulse Radio UWB Systems
In this paper, we develop a statistical characterization of the multipath
interference in an Impulse Radio (IR)-UWB system, considering the standardized
IEEE 802.15.4a channel model. In such systems, the chip length has to be
carefully tuned as all the propagation paths located beyond this limit can
cause interframe/intersymbol interferences (IFI/ISI). Our approach aims at
computing the probability density function (PDF) of the power of all multipath
components with delays larger than the chip time, so as to prevent such
interferences. Exact analytical expressions are derived first for the
probability that the chip length falls into a particular cluster of the
multipath propagation model and for the statistics of the number of paths
spread over several contiguous clusters. A power delay profile (PDP)
approximation is then used to evaluate the total interference power as the
problem appears to be mathematically intractable. Using the proposed
closed-form expressions, and assuming minimal prior information on the channel
state, a rapid update of the chip time value is enabled so as to control the
signal to interference plus noise ratio.Comment: 17 pages, 9 figures; submitted to the Journal of the Franklin
Institute on Sept. 24, 201
Performance of optimum detector structures for noisy intersymbol interference channels
The errors which arise in transmitting digital information by radio or wireline systems because of additive noise from successively transmitted signals interfering with one another are described. The probability of error and the performance of optimum detector structures are examined. A comparative study of the performance of certain detector structures and approximations to them, and the performance of a transversal equalizer are included
Influence of bandwidth restriction on the signal-to-noise performance of a modulated PCM/NRZ signal, part 2
Analyzing effects of bandlimiting on performance of digital transmission corrupted by additive white Gaussian noise by averaging and series expansio
Power and Bandwidth Efficient Coded Modulation for Linear Gaussian Channels
A scheme for power- and bandwidth-efficient communication on the linear Gaussian channel is proposed. A scenario is assumed in which the channel is stationary in time and the channel characteristics are known at the transmitter. Using interleaving, the linear Gaussian channel with its intersymbol interference is decomposed into a set of memoryless subchannels. Each subchannel is further decomposed into parallel binary memoryless channels, to enable the use of binary codes. Code bits from these parallel binary channels are mapped to higher-order near-Gaussian distributed constellation symbols. At the receiver, the code bits are detected and decoded in a multistage fashion. The scheme is demonstrated on a simple instance of the linear Gaussian channel. Simulations show that the scheme achieves reliable communication at 1.2 dB away from the Shannon capacity using a moderate number of subchannels
Analysis of detector performance in a gigahertz clock rate quantum key distribution system
We present a detailed analysis of a gigahertz clock rate environmentally robust phase-encoded quantum key distribution (QKD) system utilizing several different single-photon detectors, including the first implementation of an experimental resonant cavity thin-junction silicon single-photon avalanche diode. The system operates at a wavelength of 850 nm using standard telecommunications optical fibre. A general-purpose theoretical model for the performance of QKD systems is presented with reference to these experimental results before predictions are made about realistic detector developments in this system. We discuss, with reference to the theoretical model, how detector operating parameters can be further optimized to maximize key exchange rates
Optimization of an optically implemented on-board FDMA demultiplexer
Performance of a 30 GHz frequency division multiple access (FDMA) uplink to a processing satellite is modelled for the case where the onboard demultiplexer is implemented optically. Included in the performance model are the effects of adjacent channel interference, intersymbol interference, and spurious signals associated with the optical implementation. Demultiplexer parameters are optimized to provide the minimum bit error probability at a given bandwidth efficiency when filtered QPSK modulation is employed
Digital communications techniques Interim report, 15 Sep. 1969 - 15 Feb. 1970
Convolutional codes and recursive signal processing for digital communication
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