Alberto Conte

Cell wilting and blossoming for energy efficiency

In this article, we consider the adoption of sleep modes for the base stations of a cellular access network, focusing on the design of base station sleep and wake-up transients.. We discuss the main issues arising with this approach, and we focus on the design of base station sleep and wake-up transients, also known as cell wilting and blossoming. The performance of the proposed procedures is evaluated in a realistic test scenario, and the results show that sleep and wake-up transients are short, lasting at most 30 seconds.

Dynamic Resource Provisioning for Energy Efficiency in Wireless Access Networks: A Survey and an Outlook

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 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.

Caching at the edge: A green perspective for 5G networks

Endowed with context-awareness and proactive capabilities, caching users content locally at the edge of the network is able to cope with increasing data traffic demand in 5G wireless networks. In this work, we focus on the energy consumption aspects of cache-enabled wireless cellular networks, specifically in terms of area power consumption (APC) and energy efficiency (EE). We assume that both base stations (BSs) and mobile users are distributed according to homogeneous Poisson point processes (PPPs) and we introduce a detailed power model that takes into account caching. We study the conditions under which the area power consumption is minimized with respect to BS transmit power, while ensuring a certain quality of service (QoS) in terms of coverage probability. Furthermore, we provide the optimal BS transmit power that maximizes the area spectral efficiency per unit total power spent. The main takeaway of this paper is that caching seems to be an energy efficient solution.

Environmental friendly mobile radio networks: Approaches of the European OPERA-Net 2 project

Reducing the overall environmental impact of mobile radio networks is a central factor in achieving improved mobile services whilst at the same time enabling a growing telecommunications industry in emerging markets. The OPERA-Net-2 (Optimising Power Efficiency in Mobile Radio Networks 2) project concentrates on this challenge, addressing both energy and material efficiencies of 3G, 4G and heterogeneous networks, while also considering the use of renewable energy sources. This paper presents an insight into the project after its first year and discusses research trends in `green communications networks for the future.

The TREND experimental activities on “green” communication networks

Aimed at answering important questions about the energy demand of current telecom infrastructure and the design of sustainable and energy-efficient future networks, the research of a number of European partners is brought together in the TREND project. In this paper we present the achievements of the Work Package coordinating the experimental activities of the project - WP4. Although not presenting a completely finished portrait yet, the results shown help building a better global view on the “big picture” in the field of energy-efficient networking.

Optimal area power efficiency in cellular networks

In this paper, we study the problem of minimizing the area power consumption in wireless cellular networks. We focus on the downlink of a single-tier network, in which the locations of base stations (BSs) are distributed according to a homogeneous Poisson point process (PPP). Assuming that a mobile user is connected to its strongest candidate BS, we derive bounds on the optimal transmit power in order to guarantee a certain minimum coverage and data rate. Under the same quality of service constraints, we find the optimal network density that minimizes the area power density. Our results show that the existence of an optimal BS density for minimizing the power consumption depends on the value of the pathloss exponent.

Practical energy-saving in 3G femtocells

Cell stand-by is widely considered today as one of the most promising techniques to reduce energy consumption of cellular base stations. The majority of existing studies assume that cells can simply enter standby mode, but very few measurements and practical studies exist. In this paper we present a practical implementation of standby mode on a commercial 3G femtocell, the lessons learned and the results obtained.

Orchestrating 5G virtual network functions as a modular Programmable Data Plane

The upcoming 5G architecture is expected to heavily rely on network functions implemented by software deployed on commodity hardware architectures. Multiple standardization efforts are underway to specify interfaces between virtualized and real infrastructure, and procedures for interoperability among functions. However, the practical feasibility of function implementation in such abstract and disembodied conditions is scarcely covered in the latest literature. In this paper, we argue for a Network Function Virtualization (NFV) framework that provides 5G network functions built around a modular software router model, rather than following the traditional VM-container approaches. We illustrate its advantages in enabling support for efficient processing on heterogeneous hardware and in ensuring consistency of flow/session semantics across distributed 5G data planes. Finally, we report on the state of Programmable Data Plane, our architecture to implement 5G network functions as modular pipelines orchestrated across multiple devices.

Physical limits of point-to-point communication systems

In this paper, we explore the physical limits of successful information transfer in a point-to-point communication system. In interest of studying the fundamental limits imposed by physics on communication systems in general, we model a simple generic system that enables us to make some basic inquiries about the energy efficiency in information transfer and processing. We use ideas from thermodynamics such as Szilard engine to represent information bits. We further use ideas from electromagnetic theory for transfer of information, and information theory to define the energy efficiency metric. We find the upper limit of this efficiency and conditions at which it can be achieved.

Sustainable Internet

Information and communications technology (ICT) is expected to play a major role in reducing worldwide energy requirements by optimizing energy generation, transportation, and consumption. Recent research, however, also reveals staggering facts about how ICT is becoming a major component of the energy consumption budget. Some projections indicate that next-generation Internet applications will require electricity in amounts that cant be generated or transported to major metropolitan areas. This special issue provides a snapshot of ongoing efforts toward a global solution to these urgent challenges that will lead, in the end, to a new energy-efficient and sustainable Internet.