Distributed Stochastic Power Control in Ad-hoc Networks: A Nonconvex Case

Utility-based power allocation in wireless ad-hoc networks is inherently nonconvex because of the global coupling induced by the co-channel interference. To tackle this challenge, we first show that the globally optimal point lies on the boundary of the feasible region, which is utilized as a basis to transform the utility maximization problem into an equivalent max-min problem with more structure. By using extended duality theory, penalty multipliers are introduced for penalizing the constraint violations, and the minimum weighted utility maximization problem is then decomposed into subproblems for individual users to devise a distributed stochastic power control algorithm, where each user stochastically adjusts its target utility to improve the total utility by simulated annealing. The proposed distributed power control algorithm can guarantee global optimality at the cost of slow convergence due to simulated annealing involved in the global optimization. The geometric cooling scheme and suitable penalty parameters are used to improve the convergence rate. Next, by integrating the stochastic power control approach with the back-pressure algorithm, we develop a joint scheduling and power allocation policy to stabilize the queueing systems. Finally, we generalize the above distributed power control algorithms to multicast communications, and show their global optimality for multicast traffic.Comment: Contains 12 pages, 10 figures, and 2 tables; work submitted to IEEE Transactions on Mobile Computin

SCALE: A Low-Complexity Distributed Protocol for Spectrum Balancing in Multiuser DSL Networks

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Optimal Power Control for Rayleigh-Faded Multiuser Systems with Outage Constraints

How can we achieve the conflicting goals of reduced transmission power and increased capacity in a wireless network, without attempting to follow the instantaneous state of a fading channel? In this paper, we address this problem by jointly considering power control and multiuser detection (MUD) with outage-probability constraints in a Rayleigh fast-fading environment. The resulting power-control algorithms (PCAs) utilize the statistics of the channel and operate on a much slower timescale than traditional schemes. We propose an optimal iterative solution that is conceptually simple and finds the minimum sum power of all users while meeting their outage targets. Using a derived bound on outage probability, we introduce a mapping from outage to average signal-to-interference ratio (SIR) constraints. This allows us to propose a suboptimal iterative scheme that is a variation of an existing solution to a joint power control and MUD problem involving SIR constraints. We further use a recent result that transforms complex SIR expressions into a compact and decoupled form, to develop a noniterative and computationally inexpensive PCA for large systems of users. Simulation results are presented showing the closeness of the optimal and mapped schemes, speed of convergence, and performance comparisons.270

Distributed cross-layer optimization of MANETs in composite fading

This paper focuses on the Agrarian Question and examines the emergence of human rights from a historical perspective. Great emphasis is placed on the right to life guaranteed by the State Constitutions of the Countries of the World that contained an elaborate Bill of Rights, providing strategies of territorial integration through agrarian reform, allowing landless to reside on and use land as a means to restore their dignity which they were assigned at birth, according to the Universal Declaration of Human Rights, although their rights have been usurped in the trajectories of their lives by social disruptions and exclusion. From this perspective, the agrarian reform might be understood in a way that allows settlers and people who live in rural areas to argue that the political process should be concerned with ensuring them equal rights taking into account all aspects of urban and social space.O texto trata da Questão Agrária, à luz da emergência histórica dos Direitos Humanos. Argumenta então que o direito à vida, proclamada por todas as Constituições dos Estados de Direitos exige a integração dos despossuídos à terra de trabalho, via Reforma Agrária, como forma de restaurar-lhes a dignidade que lhes fora atribuída ao nascer, conforme a Declaração Universal dos Direitos Humanos e que lhes foi usurpada em trajetórias de vida cheias de rupturas e de exclusão social. Entender a Reforma Agrária por esse prisma permite a todos os assentados, bem como a todos os habitantes do campo, reivindicarem os direitos fundamentais concedidos aos habitantes da cidade e pensados sempre do ponto de vista do espaço social urbano

Distributed cross-layer optimization of MANETs in composite fading

Cross-layer design can significantly improve the performance of mobile ad-hoc networks (MANETs), as indicated by the flurry of recent results in the literature. Much of this work stems from the Kelly network utility maximization (NUM) framework, where convexity is crucial for developing algorithms that reach the global optimum. Unfortunately many problems are nonconvex in nature, so convex approximations are abundant. In this paper, we consider the joint optimization of source data-rates and link transmitter powers in a MANET, specifically dealing with the statistical variations of the wireless channel. In this paradigm we show that the commonly applied high-SIR convex approximation is unrealistic, so we seek to find solutions of the unmodified NUM problem. Our first result shows that the canonical formulation (previously thought to be nonconvex) is indeed a convex problem for logarithmic TCP-Vegas utilities; we then derive an algorithm reaching the global optimum. Our main result caters for the general case of strictly concave utilities, where we derive an algorithm that provably converges to the global solution of the underlying nonconvex NUM problem