Compressive and Noncompressive Power Spectral Density Estimation from Periodic Nonuniform Samples

This paper presents a novel power spectral density estimation technique for band-limited, wide-sense stationary signals from sub-Nyquist sampled data. The technique employs multi-coset sampling and incorporates the advantages of compressed sensing (CS) when the power spectrum is sparse, but applies to sparse and nonsparse power spectra alike. The estimates are consistent piecewise constant approximations whose resolutions (width of the piecewise constant segments) are controlled by the periodicity of the multi-coset sampling. We show that compressive estimates exhibit better tradeoffs among the estimator's resolution, system complexity, and average sampling rate compared to their noncompressive counterparts. For suitable sampling patterns, noncompressive estimates are obtained as least squares solutions. Because of the non-negativity of power spectra, compressive estimates can be computed by seeking non-negative least squares solutions (provided appropriate sampling patterns exist) instead of using standard CS recovery algorithms. This flexibility suggests a reduction in computational overhead for systems estimating both sparse and nonsparse power spectra because one algorithm can be used to compute both compressive and noncompressive estimates.Comment: 26 pages, single spaced, 9 figure

Patterns of Scalable Bayesian Inference

Datasets are growing not just in size but in complexity, creating a demand for rich models and quantification of uncertainty. Bayesian methods are an excellent fit for this demand, but scaling Bayesian inference is a challenge. In response to this challenge, there has been considerable recent work based on varying assumptions about model structure, underlying computational resources, and the importance of asymptotic correctness. As a result, there is a zoo of ideas with few clear overarching principles. In this paper, we seek to identify unifying principles, patterns, and intuitions for scaling Bayesian inference. We review existing work on utilizing modern computing resources with both MCMC and variational approximation techniques. From this taxonomy of ideas, we characterize the general principles that have proven successful for designing scalable inference procedures and comment on the path forward

Do the benefits of fixed exchange rates outweigh their costs? The Franc Zone in Africa

The authors develop a simple, formal framework for clarifying the tradeoffs involved in choosing between a fixed and flexible exchange rate system. They apply this framework to the countries of Africa's CFA Zone, which have maintained fixed parity with the French franc since independence. Because a few agricultural products and natural resources dominate their exports, member countries of Africa's CFA Zone have suffered frequent shocks in terms of trade. A flexible exchange rate could possibly have alleviated the costs of these external shocks. On the other hand, CFA member countries have managed to maintain lower inflation levels than their neighbors. The fixed exchange rate of the CFA Zone acts as a credible committment. The government"ties its own hands"so that it will not be tempted to use the exchange rate, thereby eliciting lower wage and price increases from the private sector. Weighing this benefit against the costs of nonadjustment to external shocks, the authors conclude that fixed exchange rates have been a bad bargain for the CFA member countries. These countries would have been better off having the ability to adjust to external shocks.Environmental Economics&Policies,Macroeconomic Management,Fiscal&Monetary Policy,Economic Stabilization,Economic Theory&Research

Do the Benefits of Fixed Exchange Rates Outweigh Their Costs? The Franc Zone in Africa

We develop a simple formal framework to clarify the trade-offs involved in the choice between a fixed and flexible exchange-rate system. We then apply the framework to the CFA Zone countries in Africa, which have maintained a fixed parity with the French Franc since independence. Thanks to the predominance of a few agricultural products and natural resources in their exports, CFA member countries have suffered frequent shocks in their terms of trade. A flexible exchange rate could have possibly alleviated the costs of these external shocks. On the other hand, CFA member countries have managed to maintain lower inflation levels than their neighbors. Our framework provides a way of weighing these costs and benefits. The inflation differential between CFA and non-CFA African countries has been around 14 percentage points. We attribute this differential to the standard time-consistency problem inherent in discretionary macroeconomic policy. Nonetheless, our highly stylized calculations suggest that fixed exchange rates have been, on the whole, a bad bargain for the CFA member countries. Under reasonable output-inflation tradeoffs, the output costs of maintaining a fixed exchange rate have outweighed the benefits of lower inflation.

Simulation and analysis of differential global positioning system for civil helicopter operations

A Differential Global Positioning System (DGPS) computer simulation was developed, to provide a versatile tool for assessing DGPS referenced civil helicopter navigation. The civil helicopter community will probably be an early user of the GPS capability because of the unique mission requirements which include offshore exploration and low altitude transport into remote areas not currently served by ground based Navaids. The Monte Carlo simulation provided a sufficiently high fidelity dynamic motion and propagation environment to enable accurate comparisons of alternative differential GPS implementations and navigation filter tradeoffs. The analyst has provided the capability to adjust most aspects of the system, the helicopter flight profile, the receiver Kalman filter, and the signal propagation environment to assess differential GPS performance and parameter sensitivities. Preliminary analysis was conducted to evaluate alternative implementations of the differential navigation algorithm in both the position and measurement domain. Results are presented to show that significant performance gains are achieved when compared with conventional GPS but that differences due to DGPS implementation techniques were small. System performance was relatively insensitive to the update rates of the error correction information