George L. Turin

An introduction to matched filters

In a tutorial exposition, the following topics are discussed: definition of a matched filter; where matched filters arise; properties of matched filters; matched-filter synthesis and signal specification; some forms of matched filters.

Introduction to spread-spectrum antimultipath techniques and their application to urban digital radio

In a combination tutorial and research paper, spread-spectrum techniques for combating the effects of multipath on high-rate data transmissions via radio are explored. The tutorial aspect of the paper presents: 1) a heuristic outline of the theory of spread-spectrum antimultipath radio receivers and 2) a summary of a statistical model of urban/suburban multipath. The research section of the paper presents results of analyses and simulations of various candidate receivers indicated by the theory, as they perform through urban/suburban multipath. A major result shows that megabit-per-second rates through urban multipath (which typically lasts up to 5 µs) are quite feasible.

A statistical model of urban multipath propagation

An urban multipath propagation experiment, involving the simultaneous transmission from a fixed site of 100-ns pulses at 488, 1280, and 2920 MHz and their reception at a mobile van, is described. A statistical analysis of the data in the resulting multipath responses is given and used as a basis for a statistical model of urban multipath propagation.

Simulation of urban vehicle-monitoring systems

The results of experimentally based computer simulations of phase-ranging and pulse-ranging urban vehicle-monitoring systems are given. These show that such systems are quite feasible even in the worst environments.

An introduction to digitial matched filters

In this introductory exposition, the class of noncoherent digital matcted filters (DMFs) which are matched to AM signals is analyzed. Attention is focused on the special case of binary signals and one-bit digitization. Expressions are obtained relating output and input signal-to-noise ratios when the channel interference is additive and a) white Gaussian, b) incoherent and of constant amplitude, and c) coherent and of constant amplitude. These expressions are compared with expressions for the performance of the corresponding noncoherent analog matched filter under the same conditions Improvements in DMF performance obtained by thresold biasing and by dithering are investigated; it is shown that DMFs can be made to outperform analog matched filters by proper use of the former technique. All theoretical results are corroborated by computer simulation.

On optimal diversity reception

The ideal probability-computing M -ary receiver is derived for a fading, noisy, multidiversity channel, in which the link fadings may be mutually correlated, as may the link noises. The results are interpreted in terms of block diagrams involving various filtering operations. Two special cases, those of very fast and very slow fading, are considered in detail.

Signal design for sequential detection systems with feedback

We consider a coherent white Gaussian channel, through which one of two signals is sent to a receiver which operates as a sequential detector. A noiseless delayless feedback link is assumed, which continuously informs the transmitter of the state of the receivers uncertainty concerning which signal was sent, and which also synchronizes the transmitter when the receiver has reached a decision. The transmitter, in turn, uses the output of the feedback link to modify its transmission so as to hasten the receivers decision. The following problem is posed: Given average- and peak-power constraints on the transmitter and a prescribed error probability for the receiver, what signal waveforms should the transmitter use in order to minimize the average transmission time, and how should it utilize the fedback values of the receivers uncertainty to modify these waveforms while transmission is in progress? We give partial solutions to these questions. In particular, we have shown that if the peak-to-average power ratio is allowed to be sufficiently large, substantial improvement of performance may be achieved through the use of uncertainty feedback.

On the estimation in the presence of noise of the impulse response of a random, linear filter

A sounding signal is transmitted through a transmission medium which may be characterized as a linear filter whose impulse response is random, i.e., drawn according to some probability law from an ensemble of possible impulse responses. To the output of the medium is added random noise; the resultant waveform is the received signal. A receiver is required to operate on this received signal so as to make a linear, minimum-mean-square-error estimate of the impulse response of the transmission medium. Two problems concerned with the design of such a sounding system are considered in this paper. The first is the determination of the transfer function of the optimum linear estimating filter in the receiver. The second is the optimization of the spectrum of the transmitted sounding signal.

Minimax Strategies for Matched-Filter Detection

The best signal and worst jamming are derived for a detection system which uses a matched-filter receiver. The penalty for deviation from the best signal is determined.

More on uncertainty feedback: The bandlimited case

A binary transmission scheme in which the transmitter is turned on and off during each bit by an uncertainty variable fed back from the receiver through a noisy feedback channel is analyzed. In particular, the energy advantage of this scheme over ordinary binary transmission without feedback, as a function of error probability, bit rate, channel bandwidth, and the magnitude of the feedback noise is given.