Multilevel Coding Schemes for Compute-and-Forward with Flexible Decoding

We consider the design of coding schemes for the wireless two-way relaying channel when there is no channel state information at the transmitter. In the spirit of the compute and forward paradigm, we present a multilevel coding scheme that permits computation (or, decoding) of a class of functions at the relay. The function to be computed (or, decoded) is then chosen depending on the channel realization. We define such a class of functions which can be decoded at the relay using the proposed coding scheme and derive rates that are universally achievable over a set of channel gains when this class of functions is used at the relay. We develop our framework with general modulation formats in mind, but numerical results are presented for the case where each node transmits using the QPSK constellation. Numerical results with QPSK show that the flexibility afforded by our proposed scheme results in substantially higher rates than those achievable by always using a fixed function or by adapting the function at the relay but coding over GF(4).Comment: This paper was submitted to IEEE Transactions on Information Theory in July 2011. A shorter version also appeared in the proceedings of the International Symposium on Information Theory in August 2011 without the proof of the main theore

Joint Compute and Forward for the Two Way Relay Channel with Spatially Coupled LDPC Codes

We consider the design and analysis of coding schemes for the binary input two way relay channel with erasure noise. We are particularly interested in reliable physical layer network coding in which the relay performs perfect error correction prior to forwarding messages. The best known achievable rates for this problem can be achieved through either decode and forward or compute and forward relaying. We consider a decoding paradigm called joint compute and forward which we numerically show can achieve the best of these rates with a single encoder and decoder. This is accomplished by deriving the exact performance of a message passing decoder based on joint compute and forward for spatially coupled LDPC ensembles.Comment: This paper was submitted to IEEE Global Communications Conference 201

A discrete integrability test based on multiscale analysis

In this article we present the results obtained applying the multiple scale expansion up to the order \epsilon^6 to a dispersive multilinear class of equations on a square lattice depending on 13 parameters. We show that the integrability conditions given by the multiple scale expansion give rise to 4 nonlinear equations, 3 of which are new, depending at most on 2 parameters and containing integrable sub cases. Moreover at least one sub case provides an example of a new integrable system

Characteristics of Staphylococcus aureus infections to consider in designing an effective vaccine.

_Staphylococcus aureus_ is a very versatile and adaptable microorganism. It can potentially infect virtually any host tissue. Given the appropriate conditions it can become a life-threatening pathogen, or a commensal colonizer of the nose. Extensive antibiotic use for infection control facilitated the rise of antibiotic resistance, stressing the need for alternate forms of control. Vaccine efforts in other pathogens have proved successful, but so far _S. aureus_ candidate vaccines have not been as effective. Here we review _S. aureus_ factors involved in pathogenesis that could help develop a successful vaccine, like host nasal colonization and immune evasion factors. An effective multicomponent vaccine could incorporate antigenic fragments from several _S. aureus_ proteins, preferably involved in colonization, immune evasion and/or toxicity

Dispersal of _Aedes aegypti_: field study in temperate areas and statistical approach

We studied the dispersion of _Aedes aegypti_ during egg laying in natural conditions. Two independent experiments involving mosquitoes dispersing from urbanization towards adjacent un-urbanized areas were carried out and analyzed in statistical terms. We find relations between stochastic variables related to the egg laying mosquito activity (ELMA), useful to assess dispersion probabilities, despite the lack of knowledge of the total number of ovipositions in the zone. We propose to evaluate the activity as minus the logarithm of the fraction of negative ovitraps at different distances from buildings. We also estimate the average number of eggs laid per oviposition using a regression between the ELMA and the number of eggs found. Three zones with different oviposition activity were determined: a corridor surrounding the urbanized area, a second region between 10m and 25m and the third region extending from 30m to 45m from the urbanization. The landscape (plant cover) and the human activity in the area appear to have an influence in the dispersal of _Aedes aegypti_