Streaming multimedia content in real-time over a wireless link is a challenging task because of the rapid fluctuations in link conditions that can occur due to movement, interference, and so on. The popular IEEE 802.11 standard includes low-level tuning parameters like the transmission rate. Standard device drivers for today's wireless products are based on gathering statistics, and consequently, adapt rather slowly to changes in conditions. To meet the strict latency requirements of streaming applications, we designed and implemented an advanced control algorithm that uses signal-strength (SNR) information to achieve fast responses. Since SNR readings are quite noisy we do not use that information to directly control the rate setting, but rather as a safeguard limiting the range of feasible settings to choose from. We report on real-time experiments involving two laptops equipped with IEEE 802.11a wireless interface cards. The results show that using SNR information greatly enhances responsiveness in comparison to statistics-based rate controllers.
Abstract-Traditionally, energy efficiency aspects have been included in the wireless access network design space only in the context of power control aimed at interference mitigation and for the increase of the terminal battery lifetime. Energy consumption of network components has also, for a long time, not been considered an issue, neither in equipment design nor in network planning and management. However, in recent years, with the user demand increasing at nearly exponential pace and margins rapidly shrinking, concerns about energy efficiency have been raised, with the objective of reducing network operational costs (not to mention the environmental issues). Installing more energy-efficient hardware does not seem to fully solve the problem, since wireless access networks are almost invariably (over)provisioned with respect to the peak user demand. This means that efficient resource management schemes, which are capable of controlling how much of the network infrastructure is actually needed and which parts can be temporarily powered off to save energy, can be extremely effective and provide quite large cost reductions. Considering that most of the energy in wireless access networks is consumed in the radio part, dynamic provisioning of wireless access network resources is crucial to achieving energy-efficient operation. The consensus on this approach in the research community has been wide in the last Manuscript received September 6, 2013; revised March 13, 2014; accepted May 6, 2014 G. Koutitas and L. Tassiulas are with the Department of Computer Engineering and Telecommunications, University of Thessaly, Volos 38221, Greece (e-mail: george.koutitas@gmail.com; leandros@inf.uth.gr).S. Lambert, B. Lannoo, and M. Pickavet are with the Department of Information Technology, Ghent University iMinds, Gent 9000, Belgium (e-mail: sofie.lambert@intec.ugent.be; bart.lannoo@intec.ugent.be; mario.pickavet@ intec.ugent.be).A. Conte and I. Haratcherev are with Alcatel-Lucent Bell Labs, BoulogneBillancourt 92100, France (e-mail: alberto.conte@alcatel-lucent.com; ivaylo@alcatel-lucent.com; haratcherev@alcatel-lucent.com few years, and a large number of solutions have been proposed. In this paper, we survey the most important proposals, considering the two most common wireless access technologies, namely, cellular and WLAN. The main features of the proposed solutions are analyzed and compared, with an outlook on their applicability in typical network scenarios that also include cooperation between both access technologies. Moreover, we provide an overview of the practical implementation aspects that must be addressed to achieve truly energy-efficient wireless access networks, including current standardization work, and trends in the development of energy-efficient hardware.
The expected massive adoption of indoor Access Points requires specific solutions to meet requirements for eco-sustainability regarding consumed power and radio interferences. Since Access Points are unused the main part of the day, application of a sleep mode mechanism is a promising approach. However, its implementation represents a radical change in mobile networking paradigm and requires innovative mechanisms to wake up the Access Points and thus rapidly restore the connectivity.Our approach uses an auxiliary low-power radio to carry out-of-band control information to maintain connectivity and wake up the Access Points when necessary. The paper details the software and hardware architecture as well as the prototyping results on Wi-Fi technology.
Streaming multimedia content in real-time over a wireless link is a challenging task because of the rapid fluctuations in link conditions that can occur due to movement, interference, and so on. The popular IEEE 802.11 standard includes low-level tuning parameters like the transmission rate. Standard device drivers for today's wireless products are based on gathering statistics, and consequently, adapt rather slowly to changes in conditions. To meet the strict latency requirements of streaming applications, we designed and implemented an advanced hybrid control algorithm that uses signal-strength (SNR) information to achieve fast responses. Since SNR readings are quite noisy we do not use that information to directly control the rate setting, but rather as a safeguard limiting the range of feasible settings to choose from. We report on real-time experiments involving two laptops equipped with IEEE 802.11a wireless interface cards. The results show that using SNR information greatly enhances responsiveness in comparison to statistics-based rate controllers. Finally, we will present the results of an experiment with realtime video streaming to a moving laptop in an office-like environment. Our hybrid control algorithm effectively prevented many packets losses, thereby achieving a much higher video quality than 1 the statistics based algorithm.
Abstract-Femtocells are considered as an enabler for low power, high bit rate future mobile access networks. In this study, we look at them as a technology to cover an area with a high bit rate connectivity. From the evaluation it is clear that sleep modes are imperative to maximise the energy efficiency of the mobile access network. We evaluate the power reduction and wake up time of different sleep modes and apply them to the model in order to evaluate the influence of the power consumption of the mobile access network. We demonstrate that fast wake up times and low power sleep modes are essential in order to make femtocells a viable technology for mobile access networks.
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