Attractive features of time-hopping spread-spectrum multiple-access systems employing impulse signal technology are outlined, and emerging design issues are described. Performance of such communications systems in terms of achievable transmission rate and multiple-access capability are estimated for both analog and digital data modulation formats under ideal multiple-access channel conditions.

http://ultra.usc.edu/assets/001/35750.pdf

Ultra-wide bandwidth time-hopping spread-spectrum impulse radio for wireless multiple-access communications

Impulse radio, a form of ultra-wide bandwidth (UWB) spread-spectrum signaling, has properties that make it a viable candidate for short-range communications in dense multipath environments. This paper describes the characteristics of impulse radio using a modulation format that can be supported by currently available impulse signal technology and gives analytical estimates of its multiple-access capability under ideal multiple-access channel conditions.

Impulse radio: how it works

Presented here is a unified approach to evaluating the error-rate performance of digital communication systems operating over a generalized fading channel. What enables the unification is the recognition of the desirable form for alternate representations of the Gaussian and Marcum Q-functions that are characteristic of error-probability expressions for coherent, differentially coherent, and noncoherent forms of detection. It is shown that in the largest majority of cases, these error-rate expressions can be put in the form of a single integral with finite limits and an integrand composed of elementary functions, thus readily enabling numerical evaluation.

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A unified approach to the performance analysis of digital communication over generalized fading channels

An ultra-wide bandwidth (UWB) signal propagation experiment is performed in a typical modern laboratory/office building. The bandwidth of the signal used in this experiment is in excess of 1 GHz, which results in a differential path delay resolution of less than a nanosecond, without special processing. Based on the experimental results, a characterization of the propagation channel from a communications theoretic view point is described, and its implications for the design of a UWB radio receiver are presented. Robustness of the UWB signal to multipath fading is quantified through histograms and cumulative distributions. The all RAKE (ARAKE) receiver and maximum-energy-capture selective RAKE (SRAKE) receiver are introduced. The ARAKE receiver serves as the best case (bench mark) for RAKE receiver design and lower bounds the performance degradation caused by multipath. Multipath components of measured waveforms are detected using a maximum-likelihood detector. Energy capture as a function of the number of single-path signal correlators used in UWB SRAKE receiver provides a complexity versus performance tradeoff. Bit-error-probability performance of a UWB SRAKE receiver, based on measured channels, is given as a function of the signal-to-noise ratio and the number of correlators implemented in the receiver.

/pdf/characterization-of-ultra-wide-bandwidth-wireless-indoor-4fi11y5xjv.pdf

Characterization of ultra-wide bandwidth wireless indoor channels: a communication-theoretic view

In this paper, we introduce a mathematical framework for the characterization of network interference in wireless systems. We consider a network in which the interferers are scattered according to a spatial Poisson process and are operating asynchronously in a wireless environment subject to path loss, shadowing, and multipath fading. We start by determining the statistical distribution of the aggregate network interference. We then investigate four applications of the proposed model: 1) interference in cognitive radio networks; 2) interference in wireless packet networks; 3) spectrum of the aggregate radio-frequency emission of wireless networks; and 4) coexistence between ultrawideband and narrowband systems. Our framework accounts for all the essential physical parameters that affect network interference, such as the wireless propagation effects, the transmission technology, the spatial density of interferers, and the transmitted power of the interferers.

A Mathematical Theory of Network Interference and Its Applications

1. Introduction to Telecommunications. 2. Power Spectral Density of Digital Modulations. 3. Scalar and Vector Communications Over the Discrete Memoryless Channel. 4. Coherent Communication with Waveforms. 5. Noncoherent Communication with Waveforms. 6. Partially Coherent Communication with Waveforms. 7. Differentially Coherent Communication with Waveforms. 8. Double Differentially Coherent Communication with Waveforms. 9. Communication over Bandlimited Channels. 10. Demodulation and Detection of Other Digital Modulations. 11. Coded Digital Communications. 12. Block-Coded Digital Communications. 13. Convolutional-Coded Digital Communications. Index.

Digital communication techniques : signal design and detection

This article reexamines the notion of closed-loop carrier phase synchronization motivated by the theory of maximum a posteriori phase estimation with emphasis on the development of new structures based on both maximum-likelihood and average-likelihood functions. The criterion of performance used for comparison of all the closed-loop structures discussed is the mean-squared phase error for a fixed-loop bandwidth.

Closed-loop carrier phase synchronization techniques motivated by likelihood functions

This article presents flve communication system options for single-aperture multiple-link (SAML) mission support that are capable of supporting a multiplicity of spacecraft that are simultaneously within the beamwidth of a single groundstation antenna. These proposed system options provide both short-term and longterm solutions for future deep-space missions such as MarsNet and the Mars Surveyor Program. The article describes these options in detail and also identifles issues and potential limitations associated with each option. Preliminary solutions are provided to some of these issues, and a set of recommendations regarding which system options are suitable for SAML scenarios is also presented.

/pdf/description-of-communication-system-options-for-single-3yrarvonkv.pdf

Description of Communication System Options for Single-Aperture Multiple-Link (SAML) Mission Support

The design of a spacecraft-monitoring system based on a Neyman–Pearson detection criterion is discussed. Each noncatastrophic state of the spacecraft is indicated by the transmission of a specific signal to the ground station. Complete failure of the spacecraft is indicated by the transmission of no signal. The set of signals chosen to represent the spacecraft states consists of a group of orthogonally spaced (in frequency) carriers each with unknown (random) phase. Receiver structures derived from maximum-likelihood considerations are proposed that provide suitable performance in the presence of frequency uncertainty (due to Doppler) and frequency rate uncertainty (due to oscillator drift). Numerical results are obtained from a combination of analysis and simulation and indicate the trade-offs among the various receiver structures between performance and implementation complexity.

/pdf/optimum-strategies-for-monitoring-the-operational-status-of-3jhp9z9wi5.pdf

Optimum Strategies for Monitoring the Operational Status of a Spacecraft

Motivated by the theory of MAP carrier phase estimation, the authors have developed a number of closed loop structures suitably derived from maximum-likelihood (ML) and average-likelihood (AL) functions. Several of these structures reduce to previously known closed loop carrier phase synchronizers while others appear to be new. Of particular interest is one of the ML structures which, when properly optimized, gives improved mean-square phase error performance over the other ML and AL structures. The improvement is largest at low symbol SNR and is thus quite significant in applications that involve a combination of low rate coding and antenna arraying such as the NASA/JPL Galileo mission to Jupiter. The structures proposed in the paper are not exhaustive of the ways that closed loop phase synchronizers can be derived from open loop MAP estimation theory. Rather they are given primarily to indicate the variety of different closed loop schemes that can be constructed simply from likelihood and log-likelihood functions. >

/pdf/closed-loop-carrier-phase-synchronization-techniques-3rj0fabtp4.pdf

S. Hinedi

Papers

Digital communication techniques : signal design and detection

Closed-loop carrier phase synchronization techniques motivated by likelihood functions

Description of Communication System Options for Single-Aperture Multiple-Link (SAML) Mission Support

Optimum Strategies for Monitoring the Operational Status of a Spacecraft

Closed loop carrier phase synchronization techniques motivated by likelihood functions