Navegando por Autor "VIJAYKUMAR, Nandamudi Lankalapalli"

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Acesso aberto (Open Access)
Green-Markov models - new optimization strategies: a case study for user allocation in co-channel macro/femto networks
(2012-12) CARDOSO, Diego Lisboa; SANTANA, Ádamo Lima de; SILVA, Marcelino Silva da; FRANCÊS, Carlos Renato Lisboa; COSTA, João Crisóstomo Weyl Albuquerque; CARVALHO, Solon Venâncio de; VIJAYKUMAR, Nandamudi Lankalapalli
The femtocell concept aims to combine fixed-line broadband access with mobile telephony using the deployment of low-cost, low-power third and fourth generation base stations in the subscribers' homes. While the self-configuration of femtocells is a plus, it can limit the quality of service (QoS) for the users and reduce the efficiency of the network, based on outdated allocation parameters such as signal power level. To this end, this paper presents a proposal for optimized allocation of users on a co-channel macro-femto network, that enable self-configuration and public access, aiming to maximize the quality of service of applications and using more efficiently the available energy, seeking the concept of Green networking. Thus, when the user needs to connect to make a voice or a data call, the mobile phone has to decide which network to connect, using the information of number of connections, the QoS parameters (packet loss and throughput) and the signal power level of each network. For this purpose, the system is modeled as a Markov Decision Process, which is formulated to obtain an optimal policy that can be applied on the mobile phone. The policy created is flexible, allowing different analyzes, and adaptive to the specific characteristics defined by the telephone company. The results show that compared to traditional QoS approaches, the policy proposed here can improve energy efficiency by up to 10%.
Acesso aberto (Open Access)
QoS management in smart grids: a Markovian approach
(2014-12) SILVA, Marcelino Silva da; FRANCÊS, Carlos Renato Lisboa; COSTA, João Crisóstomo Weyl Albuquerque; CARDOSO, Diego Lisboa; VIJAYKUMAR, Nandamudi Lankalapalli; CARVALHO, Solon Venâncio de
In Smart Grids, a variety of new applications are available to users of the electrical system (from consumers to the electric system operators and market operators). Some applications such as the SCADA systems, which control generators or substations, have consequences, for example, with a communication delay. The result of a failure to deliver a control message due to noncompliance of the time constraint can be catastrophic. On the other hand, applications such as smart metering of consumption have fewer restrictions. Since each type of application has different quality of service requirements (importance, delay, and amount of data to transmit) to transmit its messages, the policy to control and share the resources of the data communication network must consider them. In this paper Markov Decision Process Theory is employed to determine optimal policies to explore as much as possible the availability of throughput in order to transmit all kinds of messages, considering the quality of service requirements defined to each kind of message. First a non-preemptive model is formulated and after that a preemptive model is derived. Numerical results are used to compare FIFO, non-preemptive and preemptive policies.
Acesso aberto (Open Access)
Wavelength assignment using a hybrid evolutionary computation to reduce cross-phase modulation
(2014-06) MIRANDA, André Moacir Lage; LIMA, Fabio de Oliveira; ROCHA, Helder Roberto de Oliveira; VIJAYKUMAR, Nandamudi Lankalapalli; FRANCÊS, Carlos Renato Lisboa; SEGATTO, Marcelo Eduardo Vieira; COSTA, João Crisóstomo Weyl Albuquerque
In this paper, we propose a hybrid methodology based on Graph-Coloring and Genetic Algorithm (GA) to solve the Wavelength Assignment (WA) problem in optical networks, impaired by physical layer effects. Our proposal was developed for a static scenario where the physical topology and traffic matrix are known a priori. First, we used fixed shortest-path routing to attend demand requests over the physical topology and the graph-coloring algorithm to minimize the number of necessary wavelengths. Then, we applied the genetic algorithm to solve WA. The GA finds the wavelength activation order on the wavelengths grid with the aim of reducing the Cross-Phase Modulation (XPM) effect; the variance due to the XPM was used as a function of fitness to evaluate the feasibility of the selected WA solution. Its performance is compared with the First-Fit algorithm in two different scenarios, and has shown a reduction in blocking probability up to 37.14% when considered both XPM and residual dispersion effects and up to 71.42% when only considered XPM effect. Moreover, it was possible to reduce by 57.14% the number of wavelengths.