Cloud Computing: Survey on Energy Efficiency <s> Scaling of Energy Consumption with Load in Wireless Networks. <s> In this paper we examine the somewhat controversial subject of energy consumption of networking devices in the Internet, motivated by data collected by the U.S. Department of Commerce. We discuss the impact on network protocols of saving energy by putting network interfaces and other router & switch components to sleep. Using sample packet traces, we first show that it is indeed reasonable to do this and then we discuss the changes that may need to be made to current Internet protocols to support a more aggressive strategy for sleeping. Since this is a position paper, we do not present results but rather suggest interesting directions for core networking research. The impact of saving energy is huge, particularly in the developing world where energy is a precious resource whose scarcity hinders widespread Internet deployment. <s> BIB001 </s> Cloud Computing: Survey on Energy Efficiency <s> Scaling of Energy Consumption with Load in Wireless Networks. <s> Mobile receiver complexity persists as one of the key areas of concern in the adoption of MIMO technologies for systems such as high-speed downlink packet access in UMTS. This is particularly the case for high-order modulation schemes such as 16- and 64-QAM, where optimum a posteriori probability detection becomes too complex, and sub-optimal detection based on serial or parallel interference cancellation performs poorly. The above issues are successfully tackled by introducing a judicious layered encoding process at the transmitter which, once appropriately exploited at the receiver, allows considerable reductions in computational complexity in addition to improvements in performance. Also, the applicability of high-order modulations with layered encoding is investigated using system-level simulations for a 2-cell and a 7-cell urban scenario. It is shown that high-order modulations can be used in a substantial area of the cell for both investigated scenarios. <s> BIB002 </s> Cloud Computing: Survey on Energy Efficiency <s> Scaling of Energy Consumption with Load in Wireless Networks. <s> Spatial modulation (SM) is a recently developed transmission technique that uses multiple antennas. The basic idea is to map a block of information bits to two information carrying units: 1) a symbol that was chosen from a constellation diagram and 2) a unique transmit antenna number that was chosen from a set of transmit antennas. The use of the transmit antenna number as an information-bearing unit increases the overall spectral efficiency by the base-two logarithm of the number of transmit antennas. At the receiver, a maximum receive ratio combining algorithm is used to retrieve the transmitted block of information bits. Here, we apply SM to orthogonal frequency division multiplexing (OFDM) transmission. We develop an analytical approach for symbol error ratio (SER) analysis of the SM algorithm in independent identically distributed (i.i.d.) Rayleigh channels. The analytical and simulation results closely match. The performance and the receiver complexity of the SM-OFDM technique are compared to those of the vertical Bell Labs layered space-time (V-BLAST-OFDM) and Alamouti-OFDM algorithms. V-BLAST uses minimum mean square error (MMSE) detection with ordered successive interference cancellation. The combined effect of spatial correlation, mutual antenna coupling, and Rician fading on both coded and uncoded systems are presented. It is shown that, for the same spectral efficiency, SM results in a reduction of around 90% in receiver complexity as compared to V-BLAST and nearly the same receiver complexity as Alamouti. In addition, we show that SM achieves better performance in all studied channel conditions, as compared with other techniques. It is also shown to efficiently work for any configuration of transmit and receive antennas, even for the case of fewer receive antennas than transmit antennas. <s> BIB003 </s> Cloud Computing: Survey on Energy Efficiency <s> Scaling of Energy Consumption with Load in Wireless Networks. <s> The concept of a user-deployed femtocell that operates in licensed spectrum and provides cellular coverage in the home has attracted much interest in the wireless industry and an extensive deployment of femtocells is expected in the future. However, several issues arise when femtocells become more widely deployed. One concern is the additional energy consumption caused by femtocells due to their continuous receiver processing and signal transmissions, which can be significant with a large number of femtocells. Secondly, the increase in the number of active cells can result in a high increase in core networks signaling for mobility procedures. Finally, the continuous pilot transmissions can cause interference, particularly in dense urban areas. In this paper all these issues are addressed by a novel idle mode procedure which allows the femtocell transmissions and associated processing to be switched off completely at all times when the femtocell does not need to support an active call. <s> BIB004 </s> Cloud Computing: Survey on Energy Efficiency <s> Scaling of Energy Consumption with Load in Wireless Networks. <s> The concept of energy-efficient networking has begun to spread in the past few years, gaining increasing popularity. Besides the widespread sensitivity to ecological issues, such interest also stems from economic needs, since both energy costs and electrical requirements of telcos' and Internet Service Providers' infrastructures around the world show a continuously growing trend. In this respect, a common opinion among networking researchers is that the sole introduction of low consumption silicon technologies may not be enough to effectively curb energy requirements. Thus, for disruptively boosting the network energy efficiency, these hardware enhancements must be integrated with ad-hoc mechanisms that explicitly manage energy saving, by exploiting network-specific features. This paper aims at providing a twofold contribution to green networking. At first, we explore current perspectives in power consumption for next generation networks. Secondly, we provide a detailed survey on emerging technologies, projects, and work-in-progress standards, which can be adopted in networks and related infrastructures in order to reduce their carbon footprint. The considered approaches range from energy saving techniques for networked hosts, to technologies and mechanisms for designing next-generation and energy-aware networks and networking equipment. <s> BIB005 </s> Cloud Computing: Survey on Energy Efficiency <s> Scaling of Energy Consumption with Load in Wireless Networks. <s> In modern wireless communication systems, it is very important to realize simultaneously high-efficiency and linear operation of power amplifiers. This paper-overview describes the historical aspect of the Doherty approach to the power-amplifier design introduced in 1936 and modern trends in Doherty amplifier (DA) design techniques using multistage and asymmetric multiway architectures. To increase efficiency over the power backoff range, the switchmode class-E, conventional class-F, or inverse class-F operation mode by controlling the second and third harmonics can be used in the load network. The DA with a series-connected load, and inverted, push–pull, balanced, and parallel Doherty architectures are also described and discussed. Finally, examples of the lumped DA implemented in monolithic microwave integrated circuits, digitally driven Doherty technique, and broadband capability of the two-stage DA are given. <s> BIB006 </s> Cloud Computing: Survey on Energy Efficiency <s> Scaling of Energy Consumption with Load in Wireless Networks. <s> How to reduce power consumption within individual data centers has attracted major research efforts in the past decade, as their energy bills have contributed significantly to the overall operating costs. In recent years, increasing research efforts have also been devoted to the design of practical power-saving techniques in content delivery networks (CDNs), as they involve thousands of globally distributed data centers with content server clusters. In this paper, we present a comprehensive survey on existing research works aiming to save power in data centers and content delivery networks that share high degree of commonalities in different aspects. We firstly highlight the necessities of saving power in these two types of networks, followed by the identification of four major power-saving strategies that have been widely exploited in the literature. Furthermore, we present a high-level overview of the literature by categorizing existing approaches with respect to their scopes and research directions. These schemes are later analyzed with respect to their strategies, advantages and limitations. In the end, we summarize several key aspects that are considered to be crucial in effective power-saving schemes. We also highlight a number of our envisaged open research directions in the relevant areas that are of significance and hence require further elaborations. <s> BIB007 </s> Cloud Computing: Survey on Energy Efficiency <s> Scaling of Energy Consumption with Load in Wireless Networks. <s> With the growth of data volumes and variety of Internet applications, data centers (DCs) have become an efficient and promising infrastructure for supporting data storage, and providing the platform for the deployment of diversified network services and applications (e.g., video streaming, cloud computing). These applications and services often impose multifarious resource demands (storage, compute power, bandwidth, latency) on the underlying infrastructure. Existing data center architectures lack the flexibility to effectively support these applications, which results in poor support of QoS, deployability, manageability, and defence against security attacks. Data center network virtualization is a promising solution to address these problems. Virtualized data centers are envisioned to provide better management flexibility, lower cost, scalability, better resources utilization, and energy efficiency. In this paper, we present a survey of the current state-of-the-art in data center networks virtualization, and provide a detailed comparison of the surveyed proposals. We discuss the key research challenges for future research and point out some potential directions for tackling the problems related to data center design. <s> BIB008
A second important aspect for wireless network equipment is the ability of network equipment to scale energy consumption linearly with load and to switch off components into an idle state while not in use. Scalability with load is a big issue with macrocellular networks, which are dimensioned for peak load, but often operate at a fraction of their capacity. A major contributor to the power consumption of macrocells is their power amplifiers, which are currently relatively inefficient and consume a large amount of power even when the cell is only lightly loaded. One approach for addressing this problem is presented in BIB006 using multistage Doherty power amplifiers. A further important area is the use of idle modes that allow network equipment to be switched off while not required and switched quickly back on when users need to be served. This is particularly important for heterogeneous networks where many small cells are deployed, since with reducing coverage, the fraction of time when the cell is not serving users is increasing. In BIB004 , an efficient idle mode control mechanism was proposed that enables small cells to switch off all components, except for a low power uplink power detector, while not serving active connections. 3.2.3. Low-Complexity Processing in Wireless Networks. Finally, processing for wireless communications becomes more complex to maximize capacity within limited frequency resources. Examples for this trend are Multiple Input Multiple Output (MIMO) transmission, turbo coding, and base station coordination. In BIB003 , the authors showed that receiver complexity can be reduced significantly using the concept of spatial modulation. Examples of earlier work have focused on low-complexity detection algorithms  ] and on new ways of combining modulation and coding to reduce the complexity of the detection process BIB002 . Reducing processing complexity is becoming increasingly important since when moving to small cells processing becomes the limiting factor for the energy consumption of wireless networks. The topic of reducing energy consumption in fixed-access networks has been wellstudied, and the concept of greening the Internet was proposed in BIB001 . Since then, a significant amount of work has been carried out. Two comprehensive surveys have been recently published BIB005  . Additional surveys include those by BIB007 on power-saving techniques and more specifically BIB008 on network virtualization. Most of the work can be categorized into two main directions: designing energy-aware network devices and exploring energy-efficient traffic engineering and routing.