Video Prioritization for Unequal Error Protection

We analyze the effect of packet losses in video sequences and propose a lightweight Unequal Error Protection strategy which, by choosing which packet is discarded, reduces strongly the Mean Square Error of the received sequenc

Memory effects can make the transmission capability of a communication channel uncomputable

Most communication channels are subjected to noise. One of the goals of Information Theory is to add redundancy in the transmission of information so that the information is transmitted reliably and the amount of information transmitted through the channel is as large as possible. The maximum rate at which reliable transmission is possible is called the capacity. If the channel does not keep memory of its past, the capacity is given by a simple optimization problem and can be efficiently computed. The situation of channels with memory is less clear. Here we show that for channels with memory the capacity cannot be computed to within precision 1/5. Our result holds even if we consider one of the simplest families of such channels -information-stable finite state machine channels-, restrict the input and output of the channel to 4 and 1 bit respectively and allow 6 bits of memory.Comment: Improved presentation and clarified claim

Cooling, Physical Scales and the Vacuum Structure of Y-M Theories

We present a cooling method controlled by a physical cooling radius that defines a scale below which fluctuations are smoothed out while leaving physics unchanged at all larger scales. This method can be generally used as a gauge invariant low pass filter to extract the physics from noisy MC configurations. Here we apply this method to study topological properties of lattice gauge theories where it allows to retain instanton--anti-instanton pairs.Comment: Lattice'99 contribution, 3 pages, 5 figure

Non-stationary Job Search When Jobs Do Not Last Forever: A Structural Estimation to Evaluate Alternative Unemployment Insurance Systems

This paper considers a job search model where the environment is not constant throughout the unemployment spell and where jobs do not last forever. In this situation, reservation wages can be lower than they would be in a model without consideration of such separations, but also they can initially be higher precisely because of this non-stationarity of the model. Moreover, the time-dependence of reservation wages is stronger than it is when separations are not controlled for. The model is estimated structurally by using Spanish data for the period 1985-1996. The main finding is that, although at the beginning the decrease in reservation wages is the main determinant of the exit from unemployment, as time progresses the job offer arrival rate comes to be the only significant factor, given that acceptance probabilities become equal to one. The estimated parameters are used to evaluate the effect of different Unemployment Insurance designs on unemployment duration. Accordingly, one can draw the conclusion that a sufficiently decreasing pattern in unemployment benefits makes this duration to be 8.4% lower.Job Search, Nonstationarity, Unemployment, Separation probability, Structural estimation, Unemployment Insurance.