Improving Resource Efficiency with Partial Resource Muting for Future Wireless Networks

We propose novel resource allocation algorithms that have the objective of finding a good tradeoff between resource reuse and interference avoidance in wireless networks. To this end, we first study properties of functions that relate the resource budget available to network elements to the optimal utility and to the optimal resource efficiency obtained by solving max-min utility optimization problems. From the asymptotic behavior of these functions, we obtain a transition point that indicates whether a network is operating in an efficient noise-limited regime or in an inefficient interference-limited regime for a given resource budget. For networks operating in the inefficient regime, we propose a novel partial resource muting scheme to improve the efficiency of the resource utilization. The framework is very general. It can be applied not only to the downlink of 4G networks, but also to 5G networks equipped with flexible duplex mechanisms. Numerical results show significant performance gains of the proposed scheme compared to the solution to the max-min utility optimization problem with full frequency reuse.Comment: 8 pages, 9 figures, to appear in WiMob 201

The role of asymptotic functions in network optimization and feasibility studies

Solutions to network optimization problems have greatly benefited from developments in nonlinear analysis, and, in particular, from developments in convex optimization. A key concept that has made convex and nonconvex analysis an important tool in science and engineering is the notion of asymptotic function, which is often hidden in many influential studies on nonlinear analysis and related fields. Therefore, we can also expect that asymptotic functions are deeply connected to many results in the wireless domain, even though they are rarely mentioned in the wireless literature. In this study, we show connections of this type. By doing so, we explain many properties of centralized and distributed solutions to wireless resource allocation problems within a unified framework, and we also generalize and unify existing approaches to feasibility analysis of network designs. In particular, we show sufficient and necessary conditions for mappings widely used in wireless communication problems (more precisely, the class of standard interference mappings) to have a fixed point. Furthermore, we derive fundamental bounds on the utility and the energy efficiency that can be achieved by solving a large family of max-min utility optimization problems in wireless networks.Comment: GlobalSIP 2017 (to appear

Consensus Acceleration in Multiagent Systems with the Chebyshev Semi-Iterative Method

We consider the fundamental problem of reaching consensus in multiagent systems; an operation required in many applications such as, among others, vehicle formation and coordination, shape formation in modular robotics, distributed target tracking, and environmental modeling. To date, the consensus problem (the problem where agents have to agree on their reported values) has been typically solved with iterative decentralized algorithms based on graph Laplacians. However, the convergence of these existing consensus algorithms is often too slow for many important multiagent applications, and thus they are increasingly being combined with acceleration methods. Unfortunately, state-of-the-art acceleration techniques require parameters that can be optimally selected only if complete information about the network topology is available, which is rarely the case in practice. We address this limitation by deriving two novel acceleration methods that can deliver good performance even if little information about the network is available. The first proposed algorithm is based on the Chebyshev semi-iterative method and is optimal in a well defined sense; it maximizes the worst-case convergence speed (in the mean sense) given that only rough bounds on the extremal eigenvalues of the network matrix are available. It can be applied to systems where agents use unreliable communication links, and its computational complexity is similar to those of simple Laplacian-based methods. This algorithm requires synchronization among agents, so we also propose an asynchronous version that approximates the output of the synchronous algorithm. Mathematical analysis and numerical simulations show that the convergence speed of the proposed acceleration methods decrease gracefully in scenarios where the sole use of Laplacian-based methods is known to be impractical

Diffraction and an infrared finite gluon propagator

We discuss some phenomenological applications of an infrared finite gluon propagator characterized by a dynamically generated gluon mass. In particular we compute the effect of the dynamical gluon mass on $pp$ and ${\bar{p}}p$ diffractive scattering. We also show how the data on $\gamma p$ photoproduction and hadronic $\gamma \gamma$ reactions can be derived from the $pp$ and $\bar{p}p$ forward scattering amplitudes by assuming vector meson dominance and the additive quark model.Comment: 4 pages, 7 figures, added references and figures, changed structure. Contribution to Proceedings of XVIIIth Reuniao de Trabalho sobre Interacoes Hadronicas, Sao Paulo, Brazil, 22-24 May, 200

All-strain based valley filter in graphene nanoribbons using snake states

A pseudo-magnetic field kink can be realized along a graphene nanoribbon using strain engineering. Electron transport along this kink is governed by snake states that are characterized by a single propagation direction. Those pseudo-magnetic fields point towards opposite directions in the K and K' valleys, leading to valley polarized snake states. In a graphene nanoribbon with armchair edges this effect results in a valley filter that is based only on strain engineering. We discuss how to maximize this valley filtering by adjusting the parameters that define the stress distribution along the graphene ribbon.Comment: 8 pages, 6 figure

Scalar form factors and nuclear interactions

The scalar-isoscalar term in the two-pion exchange $NN$ potential is abnormally large and does not respect the hierarchy of effects predicted by chiral perturbation theory. We argue that this anomaly is associated with non-perturbative effects, which are also present in the $\pi N$ scalar form factor.Comment: Talk given at the 20EFB, Pisa, Italy, September 2007. 3 pages and 4 figure

Pion-delta sigma-term

We use a configuration space chiral model in order to evaluate nucleon and delta sigma-terms. Analytic expressions are consistent with chiral counting rules and give rise to expected non-analytic terms in the chiral limit. We obtain the results $\sigma_N=46$ MeV and $\sigma_{\Delta}=32$ MeV, which are very close to values extracted from experiment and produced by other groups.Comment: 18 pages, 4 figure

Palma forrageira: alternativa para a estacionalidade de produção de forragem no semi-árido brasileiro.

bitstream/item/86054/1/Midia-Palma-Forrageira.pd

Produção e distribuição sazonal de litter em áreas de caatinga sob diferentes manejos.

Resumo: O litter compreende restos vegetais e animais. Sua presença confere proteção ao solo evitando o efeito negativo das enxurradas, mantendo a temperatura e estrutura do solo. Este trabalho objetivou quantificar a produção e distribuição de litter em áreas de caatinga raleada e não manipulada. Três áreas foram utilizadas: raleada para fins pastoris, raleada para fins apícolas e não manipulada. A produção foi obtida a partir do lançamento de molduras e 1,0x0,25m em diferentes épocas do ano de 2012. O litter foi fracionado manualmente em seus componentes e determinados suas proporções da massa total. A área não manipulada apresentou maior produção de litter, 5.714,35 Kg/ha enquanto a área de Caatinga raleada para fins apícolas a menor produção, 3.921,21 Kg/ha. A miscelânea foi a fração do litter que apresentou maior representatividade chegando a responder por 50% de toda a produção. A produção de litter de uma área nativa pode ser semelhante a uma área raleada. A produção tem relação direta com a precipitação. Esta mostrou sazonalidade na produção total, contrariando suas frações que mantiveram-se equilibrados durante todo o ano. [Seasonal production and distribution of litter in different areas under caatinga managements]. Abstract: The litter includes plant and animal remains. Its presence confers protection to the ground avoiding the negative effect of floods, keeping the temperature and soil structure. This study aimed to quantify the production and distribution of litter in areas of thinned caatinga and not manipulated. Three areas were used for grazing purposes thinned, thinned for apiculture and not manipulated. The production was obtained from the launch of frames and 1.0 x0, 25m at different times of the year 2012. The litter was manually fractionated into its components, and certain proportions of their total mass. The area had not manipulated greater production of litter, 5714.35 kg / ha while the area of Caatinga thinned for apiculture lower production, 3921.21 kg / ha. The smorgasbord was the fraction of the litter with the highest representation coming to account for 50% of all production. The production of litter from an area native can be similar to a thinned area. The production is directly related to precipitation. The total production of litter showed seasonality, contradicting its fractions which remained balanced throughout the year