No abstract

No abstract

The growing demand for mobile wireless access has stimulated the emergence of new communication technologies. Opportunistic Spectrum Access (OSA) is viewed as a promising alternative to overcome the problems caused by static spectrum assignment. Opportunistic access allows dynamic mapping of the transmission needs and communication opportunities. However, performing this task efficiently is not trivial. Indeed, it has been shown to be NP-complete. In this context, this paper presents an efficient heuristic for solving the channel allocation and data assignment problem, according to the opportunities and channels available. The proposed heuristic is optimal in terms of energy consumption, being close to the optimum, about 5% above, in terms of transmission time.

The type of practice can influence what is learned from a motor skill. The aim of this study was to investigate the effects of the constant and random practice on the learning of Generalized Motor Program and parameters of the volleyball serve. The sample was composed of 20 children between 10 and 12 years old. The participants performed a pre-test whose score was adopted to counterbalance two groups (n=10), random practice and constant practice. During the acquisition phase, the random group performed 252 serves from three different positions, always indicated at the end of each serve, and the constant group performed all serves from only a specific position. The retention test showed that both groups learned the Generalized Motor Program, but random practice conducted to higher parameterization learning, resultant from the variable of practice. During practice of a sport motor skills, although the constant and random practice improve the learning of Generalized Motor Program, only the random practice improves learning of parameters of the motor skill.

The growing demand for mobile wireless access has stimulated the emergence of new communication technologies. Opportunistic Spectrum Access (OSA) is viewed as a promising alternative to overcome the problems caused by static spectrum assignment. Opportunistic access allows dynamic mapping of the transmission needs and communication opportunities. However, performing this task efficiently is not trivial. Indeed, it has been shown to be NP-complete. In this context, this paper presents an efficient heuristic for solving the problem of channel allocation and routing, according to the opportunities and channels available. The proposed heuristic is optimal in terms of energy consumption, being close to the optimum, about 5% above, in terms of transmission time.

In wireless ad hoc networks, bridges and articulation nodes are critical elements that, in case of failure, render the network disconnected. Owing to their relevance, a number of works try to extend the life span of these elements. Nevertheless, in critical situations, such as the unavailability of a critical link, ways to reestablish the communication, even if for short periods of time, can be of importance in a number of urgent tasks. In this context, this work explores the concept of Cooperative Communication (CC) to monitor critical nodes and links and recover network connectivity in case of disruption. Unlike other works that perform exhaustive search to locate suitable CC-links that require global topology information, the proposed scheme identifies critical nodes and links based solely on local information. Compared to other prominent works, the proposed solution was able to reduce the computing cost to create CC-links in ≈ 67 times in the evaluated scenarios while persisting a lower message overhead.

No abstract

Cooperative communication (CC) is a technique that has been explored as an alternative to connect isolated network components in wireless ad hoc settings. However, existing solutions are centralized and have high computational cost, as they require complete topology information. This paper presents a distributed solution to improve network connectivity by exploring CC using localized information. Simulation results show that the proposed scheme is able to restore connectivity in more than 95% of the evaluated cases. Furthermore, transmission power needed to establish the CC is comparable to the cost of similar solutions that require global topological information.