Energy efficient infrastructures or green IT (Information Technology) has recently become a hot button issue for most corporations as they strive to eliminate every inefficiency from their enterprise IT systems and save capital and operational costs. Vendors of IT equipment now compete on the power efficiency of their devices, and as a result, many of the new equipment models are indeed more energy efficient. Various studies have estimated the annual electricity consumed by networking devices in the U.S. in the range of 6 - 20 Terra Watt hours. Our research has the potential to make promising solutions solve those overuses of electricity. An energy-efficient data center network architecture which can lower the energy consumption is highly desirable. First of all, we propose a fair bandwidth allocation algorithm which adopts the max-min fairness principle to decrease power consumption on packet switch fabric interconnects. Specifically, we include power aware computing factor as high power dissipation in switches which is fast turning into a key problem, owing to increasing line speeds and decreasing chip sizes. This efficient algorithm could not only reduce the convergence iterations but also lower processing power utilization on switch fabric interconnects. Secondly, we study the deployment strategy of multicast switches in hybrid mode in energy-aware data center network: a case of famous Fat-tree topology. The objective is to find the best location to deploy multicast switch not only to achieve optimal bandwidth utilization but also minimize power consumption. We show that it is possible to easily achieve nearly 50% of energy consumption after applying our proposed algorithm. Finally, although there exists a number of energy optimization solutions for DCNs, they consider only either the hosts or network, but not both. We propose a joint optimization scheme that simultaneously optimizes virtual machine (VM) placement and network flow routing to maximize energy savings. The simulation results fully demonstrate that our design outperforms existing host- or network-only optimization solutions, and well approximates the ideal but NP-complete linear program. To sum up, this study could be crucial for guiding future eco-friendly data center network that deploy our algorithm on four major layers (with reference to OSI seven layers) which are physical, data link, network and application layer to benefit power consumption in green data center.

Placing smaller cells in a heterogeneous cellular network can be beneficial in terms of energy because better capacities can be obtained for a given energy constraint. These type of deployments not only highlight the need for appropriate metrics to evaluate how well energy is being spent, but also raise important issues that need to be taken into account when analysing the overall use of energy. In this work, handoff strategies, bandwidth allocation, and path loss models in different scenarios, illustrate how energy can be consumed in a more efficient way when cell size is decreased. A handoff strategy based on per-energy capacity is studied in order to give priority to a more energy efficient handoff option. Energy can also be spent more adequately if the transmit power is adjusted as a function of interference. As a result, users can experience higher capacities while spending less energy, depending whether they handoff or not, increasing the overall performance of the network in terms of energy efficiency.

No description available.

The use of solar heated attic air is an area of increasing interest in commercial poultry production. Attic inlets satisfy the demand for alternative heating while being simple to implement in an existing poultry house. However, little attention has been given to the configuration of the attic space and its influence on thermal energy extraction. This issue was approached in a threefold manner: i.) test case experimental data for the operation of attic inlets in an east-west oriented commercial broiler house was recorded, ii.) a two-dimensional computational fluid dynamics (CFD) attic inlet ventilation model (AIVM) was developed and verified using the experimental data, and iii.) the simulation was used to investigate the efficiency of attic inlet system improvements. The simulation demonstrated that the strategic placement of a simple diverter and an inlet riser may increase thermal energy extraction by 40% over the measured attic inlet system.

No / The complementary features of various wireless access technologies in heterogeneous wireless networks make it attractive and challenging to offer users an always best connected (ABC) service. To achieve this goal, the dynamic network selection has received many research efforts. However, most of the existing work have focused on the network layer performance and ignored the consideration of energy efficiency. To fill this gap, an energy-efficient network selection scheme is proposed in this paper to improve the energy efficiency of wireless network access in heterogeneous wireless networks environment. The dynamics of network selection is formulated as the process of an evolutionary game. The users in different service areas complete for the data rate from different wireless networks (i.e., WMAN, cellular networks, and WLAN), and the network selection made by a user is based on its payoff that is a function of the data rate and power consumption. The addressed problem is then modelled by the replicator dynamics. Simulation results are presented to demonstrate the significant performance improvement compared to the existing scheme.

Energieffektivisering har länge varit och blir alltmer aktuell, dels för att främja social, ekonomisk och miljömässig hållbarhet, dels för att motverka den rådande energikrisen i Europa. 2014 beslutades det om Lag (2014:266) om energikartläggning i stora företag. Lagen innebär att företag som årligen omsätter mer än 50 miljoner euro och är fler än 250 anställda ska göra en energikartläggning var fjärde år. Foria AB omsätter årligen mer än 50 miljoner euro och blev under 2022 fler än 250 anställda vilket resulterar i att företaget omfattas av Lag (2014:266). Syftet med examensarbetet är identifiera vilka styrkor och svagheter som energikartläggningar har samt att genomföra en energikartläggning över Foria AB:s energikrävande aktiviteter enligt kategorierna transport, verksamhet och byggnader och identifiera energieffektiviserande åtgärder i enlighet med Lag (2014:266). Energikartläggningen är genomförd enligt ISO 50001 standarden vilket bland annat kräver ett kontinuerligt arbete med energifrågan. Ett kontinuerligt arbete med energifrågan har visat sig ha större positiv effekt av företags energieffektivisering i jämförelse med om det är en engångsprocedur. Energikartläggningen är baserad på data om energianvändningen i form av tankad mängd drivmedel, el- och värmefakturor samt schablonberäkningar där data inte är tillgängliga. Resultatet av energikartläggningen visar att Forias transporter utgör den största energiposten med ett energibehov på 22,1 GWh under 2022, följt av byggnader som hade ett energibehov på 0,97 GWh och verksamhet med ett energibehov på 0,51 GWh. Vid utarbetandet av de energieffektiviserande åtgärderna togs beslutet att fokusera på transporter i sin helhet, samt byggnaderna och tillhörande verksamheter vid tre olika platskontor. De energieffektiviserande åtgärder som identifierades inom litteraturen och i samband med intervjuer med Foria AB:s anställda inom transportkategorin är att köra mer sparsamt, installera GPS:er i fordonen för att kunna trafikleda mer effektivt samt att nyttja ett mjukvaruprogram vid trafikledning. Bland dessa energibesparingsåtgärder identifierades överexponeringar och överlappande åtgärder på grund av bristfälliga data, vilka är några av de svagheterna som finns med energikartläggningar. Energieffektiviserande åtgärder inom kategorin byggnader är att behovsanpassa underhållsystem, optimera nyttjandet av lokaler i syfte att minska värme- och ventilationsbehovet samt byta ut och renovera ineffektiva värmesystem. De energibesparande åtgärder som ger störst andel sparad energi är samtliga åtgärder inom transport. Trots att den exakta besparingen inte kunnat fastställas görs bedömningen att det finns potential till energibesparing då både litteraturen och känslighetsanalysen tyder på det. För att få mer exakta resultat av energianvändningen och energibesparingen behöver mer data samlas in. Trots att datainsamlingen delvis är baserad på schablonberäkningar, att svagheter identifierats och de energieffektiviserande åtgärderna är baserade på förväntad andel sparad energi bedöms energikartläggningen ge en tillräckligt representativ bild av energibehovet samt att Foria AB har god potential till energieffektivisering genom att implementera de föreslagna åtgärderna. / To be energy efficiency is increasingly relevant, partly to promote social, economic, and environmental sustainability, and partly to counteract the ongoing energy crisis in Europe. In 2014, the Law (2014:266) on Energy Mapping in Large Companies was enacted. The law stipulates that companies that has an annual turnover of more than 50 million euros and have more than 250 employees must conduct an energy mapping every four years. In 2022, the transportation company Foria AB exceeded 250 employees, had an annual turnover of more than 50 million euros, and is therefore subject to Law (2014:266). The purpose of the thesis is to identify strengths and weaknesses of energy audits and to conduct an energy mapping of Foria AB's energy-intensive activities in the categories of transportation, operations, and buildings, and identify energy efficiency measures in accordance with Law (2014:266).  The energy audit has been conducted according to the ISO 50001 standards, which, among other things, requires ongoing work with the energy related questions. Continuous efforts in addressing energy issues have been found to have a greater impact on a company’s energy efficiency compared to a one-time procedure. The energy audit is based on data regarding fuel consumption, electricity, and heat invoices, as well as default calculations where real data was unavailable. The result of the energy audit revealed that Foria's transportations are the largest energy expenditure, with an energy demand of 22.1 GWh in 2022, followed by buildings with an energy demand of 0.97 GWh and operations with 0.51 GWh. When identifying the energy efficiency measures, the decision was made to focus on transportation, as well as the buildings and associated operations at three different branch offices. The energy efficiency measures were identified in the literature and through interviews with employees at Foria AB. For the transportation category this resulted in driving more efficiently, installing GPS systems in vehicles for more efficient traffic management, and utilizing software programs for traffic control. Energy efficiency measures for buildings include adapting maintenance systems to actual needs, optimizing space utilization to reduce heating and ventilation requirements, and replacing and renovating inefficient heating systems. The energy-saving measures that result in the largest proportion of saved energy are all within transportation. Although the exact savings couldn't be determined, the assessment is that there is potential for energy savings, as both the literature and sensitivity analysis suggest. To obtain more precise results regarding energy consumption and energy savings, more data needs to be collected. Although the data is partly based on default calculations, that weaknesses were identified, and the energy efficiency measures are based on expected energy savings, the energy mapping is deemed to provide a sufficiently representative picture of the energy demand and that Foria AB has good potential for energy efficiency by implementing the proposed measures.

Scaling up application performance on single high-end machines is increasingly becoming difficult due to scalability challenges of processor interconnects, cache coherence protocols, and memory bandwidth. Significant prior work has addressed this problem by scaling-out application threads across multiple nodes to exploit resources outside the single machine boundary. Prior works have also leveraged heterogeneous instruction set architecture (ISA) systems to improve application performance as well as energy-efficiency, a major cost driver in datacenters, by augmenting high-end servers with power-efficient embedded boards. Existing works, however, suffer from deployability challenges due to dependencies on the operating system or programming models that require non-trivial application modifications. We introduce CRIU-RTX, a userspace framework to scale-out multi-threaded applications across multiple nodes. Integrated with HetMigrate, a prior work on migrating processes across heterogeneous-ISA systems, CRIU-RTX can suspend a subset of threads in a process and resume their execution on different nodes, including, but not limited to heterogeneous-ISA nodes. CRIU-RTX implements distributed shared memory in userspace, thereby allowing application threads to access distributed memory transparently without any operating system dependency. Our experimental evaluations show 21% to 43% performance gains while scaling-out applications across x86-64 servers, and energy efficiency gains of up to 18% while scaling-out across a cluster of x86-64 server and ARM64 embedded boards. Since CRIU-RTX does not depend on operating system modifications, it can be easily deployed on a diverse set of machines, including, but not limited to ISA-different machines running the stock Linux operating system. / Master of Science / Commonly referred to as "Moore's Law", Gordan Moore predicted that the number of transistors on a chip would double every two years. However, this law no longer holds true, leading to a shift in computer research and development. To meet the increasing demands for faster and cheaper servers, researchers began exploring alternative computer designs. Data centers have started adopting servers with diverse architectures to enhance the cost-to-performance ratio, resulting in heterogeneous environments. Distributed execution refers to the process of running computational tasks or executing software across multiple interconnected systems or nodes. Instead of relying on a single machine or processor, the workload is distributed among a network of computers, allowing for parallel processing and improved performance. Prior works in this direction had difficulty in adoption due to customized hardware or operating system requirements. This thesis introduces CRIU-RTX, a userspace framework to scale-out application threads without operating system dependency. We implemented a distributed shared memory system in userspace to allow application threads running in scaled-out execution to access distributed memory as if they are running on the same machine. Our evaluations of CRIU-RTX show significant improvement in performance and energy-efficiency.

Database management systems (DBMS) are typically tuned for high performance and scalability. Nevertheless, carbon footprint and energy efficiency are also becoming increasing concerns. Unfortunately, existing studies mainly present theoretical contributions but fall short on proposing practical techniques. These could be used by administrators or query optimizers to increase the energy efficiency of the DBMS. Thus, this paper explores the effect of so-called sweet spots, which are energy-efficient CPU frequencies, on the energy required to execute queries. From our findings, we derive the Sweet Spot Technique, which relies on identifying energy-efficient sweet spots and the optimal number of threads that minimizes energy consumption for a query or an entire database workload. The technique is simple and has a practical implementation leading to energy savings of up to 50% compared to using the nominal frequency and maximum number of threads.

No description available.

Wireless sensor network (WSN) technology has gained in importance due to its potential support for a wide range of applications. Most of the WSN applications consist of a large number of distributed nodes that work together to achieve common objectives. Running a large number of nodes requires an efficient mechanism to bring them all together in order to form a multi-hop wireless network that can accomplish specific tasks. Even with the recent developments made in WSN technology, a number of important challenges still create vulnerabilities for WSNs, including: energy waste sources; synchronisation leaks; low network capacity; and self-configuration difficulties. However, energy efficiency perhaps remains both the most challenging and highest priority problem due to the scarce energy resources available in sensor nodes. Synchronization by means of scheduling clusters allows the nodes to cooperate and transmit traffic in a scheduled manner under the duty cycle mechanism. This paper aims to make further advances in this area of work by achieving higher accuracy and precision in time synchronisation through controlling the network topology, self-configuration and estimation of the clock errors between the nodes and finally correcting the nodes’ clock to the estimated value. Furthermore, the target in designing energy efficient protocol relies on synchronized duty cycle mechanism and requires a precise synchronisation algorithm that can schedule a group of nodes to cooperate by communicating together in a scheduled manner. These techniques are considered as parameters in the proposed OLS-MAC algorithm. This algorithm has been designed with the objective of ensuring the schedules of the clusters overlap by introducing a small shift in time between the adjacent clusters’ schedules to compensate for the clock drift. The OLS-MAC algorithm is simulated in NS-2 and compared to some S-MAC derived protocols. The simulation results verified that the proposed algorithm outperforms previous protocols in number of performance criterion.