Power-saving Mode Research Articles

Energy Efficient Downlink Transmission in Wireless LANs by Using Low-Power Wake-Up Radio

In the downlink of a wireless LAN, power-save mode is a typical method to reduce power consumption. However, it usually causes large delay. Recently, remote wake-up control via a low-power wake-up radio (WuR) has been introduced to activate a node to instantly receive packets from an access point (AP). But link quality is not taken into account and protocol overhead of wake-up per node is relatively large. To solve these problems, in this paper, a broadcast-based wake-up control framework is proposed, and a low-power WuR is used to receive traffic indication map from an AP, monitor link quality, and perform carrier sense. Among the nodes which have packets buffered at the AP, only those whose SNR is above a threshold will be activated, contending via a proper contention window to receive packets from the AP. Optimal SNR threshold, deduced by theoretical analysis, helps to reduce transmission collisions and false wake-ups (caused by wake-up latency) and improve transmission rate. Extensive simulations confirm that the proposed method (i) effectively reduces power consumption of nodes compared with other methods, (ii) has less delay than power-save mode in times of light traffic, and (iii) achieves higher throughput than other methods in the saturation state.

A location-aware power saving mechanism based on quorum systems for multi-hop mobile ad hoc networks

IEEE 802.11 specifies a Power Saving Mode (PSM) in order to save the consumption of energy or power for mobile stations in wireless ad hoc networks. Following the standard of PSM, a number of studies [1–5] further discussed the wake-up/sleep scheduling of beacon intervals based on Quorum systems so that any communication pair of stations has common awake intervals for data exchange. However, most of them did not take into consideration the fact that non-neighbor stations did not require common wake up intervals since they were unable to communicate with each other. Hence, the energy conservation and the transmission delay could not be significantly improved. This paper utilizes the location information and proposes a location-aware power saving mechanism. In the proposed scheme, the network area is partitioned into regular hexagon cells and every station determines the basic quorum intervals based on its cell location information such that only neighboring cells have common beacon intervals for data exchange. In addition, a collision avoidance strategy is proposed to improve the network throughput. Experiment results reveal that the proposed scheme outperforms existing approaches in terms of energy conservation and transmission delay.

Design of Temperature Control Coolant

Design of Temperature Control Coolant

An adaptive two-stage energy-efficiency mechanism for the doze mode in EPON

Abstract Sleep and doze power-saving modes are the common ways to reduce power consumption of optical network units (ONUs) in Ethernet passive optical network (EPON). The doze mode turns off the ONU transmitter when there is no traffic in the upstream direction while the sleep mode turns off the ONU transmitter and receiver. As the result, the sleep mode is more efficient compared to the doze mode, but it introduces additional complexity of scheduling and signaling, losses the clock synchronization and requires long clock recovery time; furthermore, it requires the cooperation of the optical line terminal (OLT) in the downstream direction to queue frames. To improve the energy-saving in the doze mode, a new two-stage mechanism is introduced that the doze sleep duration is extended for longer time with acceptable quality-of-services (QoS) metrics when ONU is idle in the current cycle. By this way the ONU enters the doze mode even in the high load traffic; moreover, the green dynamic bandwidth allocation (GBA) is proposed to calculate the doze sleep duration based on the ONU queue state and incoming traffic ratio. Simulation results show that the proposed mechanism significantly improves the energy-saving 74% and 54% when traffic load is from the light load to the high load in different traffic situations, and also promises the QoS performance.

Energy Aware Power Save Mode based AODV Routing for IEEE 802.11s Wireless Mesh Networks

Owing to the self organizing, self configuring and self healing capabilities, Wireless Mesh Nwetworks (WMN) have emerged as most powerful architectures in recent times. Wireless Mesh Networks operate with limited battery resources. In 802.11s, a mobile station(STA) can act as router as well as client that results in increased energy consumption during routing process. The degradation of energy at STA can result in low network performance due to relay STA failure. In order to increase network performance there is a need to reduce the energy consumption rate of STA. To save energy, 802.11s has introduced a mechanism called power save mode(PSM) which switches STA mode from active to light sleep or deep sleep mode when STA is not involved in transmission. This ensures saving of energy at each STA during routing process. Several models have been proposed by researchers to improve the energy saving mechanisms in 802.11s. Adhoc On Demand Distance Vector (AODV) routing algorithm is used for routing purpose in WMN. In this routing protocol, regular usage of the same node during routing may lead to battery failure and result in low network lifetime. Hence in this work we propose a novel Energy Aware Power Save Mode-AODV (EAPSM-AODV) routing model that switches among power save modes based on battery status of a node before participating in AODV routing. Our proposed routing model refers to the mechanism that takes available remaining energy and energy draining rate of a node into account to decide on relaying traffic. It consist of four units namely Routing, Path choosing, Mode selector and Energy units. Experiments have been conducted using NS3 simulator by considering various situations such as keeping nodes in static position and moving nodes dynamically in a simulation area. The results shows that our proposed model significantly improves network performance and increase in network lifetime.

ECO-FiWi: An Energy Conservation Scheme for Integrated Fiber-Wireless Access Networks

Integrated fiber-wireless (FiWi) access networks aim at taking full advantage of the reliability and high capacity of the optical backhaul along with the flexibility, ubiquity, and cost savings of the wireless/cellular front-end to provide broadband services for both mobile and fixed users. In FiWi access networks, energy efficiency issues must be addressed in a comprehensive fashion that takes into account not only wireless front-end but also optical backhaul segments to extend the battery life of wireless devices and allow operators to reduce their OPEX, while not compromising quality of service (QoS). This paper proposes an energy conservation scheme for FiWi networks (ECO-FiWi) that jointly schedules power-saving modes of wireless stations and access points and optical network units to reduce their energy consumption. ECO-FiWi maximizes the overall network performance by leveraging TDMA to synchronize the power-saving modes and incorporate them into the dynamic bandwidth allocation (DBA) process. A comprehensive energy saving model and an M/G/1 queuing-based analysis of downstream and upstream end-to-end frame delays are presented accounting for both backhaul and front-end network segments. Analytical results show that ECO-FiWi achieves significant amounts of energy saving, while preserving upstream delay and incurring a low delay for downstream traffic.

Design, Analysis, and Hardware Emulation of a Novel Energy Conservation Scheme for Sensor Enhanced FiWi Networks (ECO-SFiWi)

Fiber-wireless sensor networks (Fi-WSNs) composed of a hybrid fiber-wireless (FiWi) network enhanced with sensors will play a key role in supporting machine-to-machine (M2M) communications to enable a wide range of Internet of Things (IoT) applications, of which smart grids represent an important real-world example. This paper explores opportunities of designing an energy-efficient Fi-WSN based on EPON/10G-EPON, WLAN, wireless sensors, and passive fiber optic sensors as a shared communications infrastructure for broadband services and smart grids. A novel energy conservation scheme for sensor enhanced FiWi networks (ECO-SFiWi) is proposed to reduce the overall energy consumption. ECO-SFiWi maximizes energy efficiency by leveraging TDMA to schedule power-saving modes of EPON's optical network units, wireless stations, and wireless sensors and incorporate them into EPON's bandwidth allocation algorithm. To study the performance, a comprehensive energy saving model and a delay analysis of both FiWi traffic and sensor data based on M/G/1 queue modeling are presented. FPGA-based hardware emulation and demonstration are performed to verify the effectiveness of the proposed solution. Results provide deep insights into the tradeoff between energy savings and frame delays. Noticeably, ECO-SFiWi achieves significant amounts of energy saving, while maintaining low delay for FiWi traffic and sensor data under typical deployment scenarios.

Machine-to-Machine Communications Over FiWi Enhanced LTE Networks: A Power-Saving Framework and End-to-End Performance

To cope with the unprecedented acceleration of machine-to-machine (M2M) services over cellular networks, this paper envisions a highly converged network architecture based on the integration of high-capacity and reliable Ethernet fiber-wireless (FiWi) access networks with flexible and cost-effective 4G long term evolution (LTE) technology to support M2M connectivity in an end-to-end fashion, i.e., from air interface to transport (backhaul) network. In such emerging architecture, energy efficiency must be addressed in a comprehensive way, in which both wireless front-end and optical backhaul segments are considered at the same time to maximize the battery life of battery-constrained M2M devices as well as reduce operational expenditures for network operators, while maintaining acceptable network performance. Toward this end, an end-to-end power-saving framework is introduced in this paper that devises a timeout driven discontinuous reception (DRX) mechanism for LTE-enabled M2M devices and a polling-based power-saving mechanism for optical network units (ONUs) to improve the overall energy efficiency. End-to-end performance in terms of energy saving and packet delay is analytically modeled based on a semi-Markov process for the front-end and an M/G/1 queue for the backhaul. The obtained results indicate that the device battery life is significantly prolonged by extending the DRX cycle, whereas the backhaul energy consumption is minimized by incorporating the ONU power-saving modes into the dynamic bandwidth allocation process of the optical backhaul.

Dynamic Antenna Management for Uplink Energy Efficiency on 802.11n Mobile Devices

An increasing number of mobile devices are being equipped with 802.11n interfaces to support bandwidth-intensive applications; however, the improved bandwidth increases power consumption. To address the issue, researchers are focusing on antenna management. In this paper, we present a dynamic antenna management (DAM) scheme to improve the uplink energy efficiency on mobile devices whose packet workloads may vary significantly and frequently. First, we model antenna management as an optimization problem, with the objective of minimizing the energy required to transmit a sequence of variable-length packets with random arrival times. Then, we propose an optimal offline algorithm to solve the problem, as well as a competitive online algorithm that has a provable performance guarantee and allows compatible implementations on 802.11n mobile devices. To evaluate our scheme, we conducted extensive simulations based on real mobile user traces and application transmission patterns. Nearly all commercial 802.11n mobile devices support the power save mode (PSM). Our results demonstrate that DAM can improve the energy efficiency of PSM significantly at a cost of slight throughput degradation.

Sleep-Based Energy-Efficient DBA in an EPON Using the Controlling Mechanism for an ONU’s Buffer Occupancy and Packet Delay

We propose an energy-efficient dynamic bandwidth allocation (EE-DBA) in an Ethernet passive optical network. In the proposed EE-DBA, the eligibility of optical network units (ONUs) to enter a power-saving mode is investigated based on their buffer occupancy and packet delay conditions that satisfy the user's quality of service (QoS) requirement. These conditions are easily obtained through the multipoint control protocol that is exchanged between the optical line terminal and the ONUs. The performance of the proposed EE-DBA is evaluated through simulations, and the results show that the power consumption of ONUs could be reduced by about 53% without sacrificing the user's QoS requirement under light and moderate traffic loads.

Optimization of heat exchangers of refrigeration machines by entropy generation minimization method

The development of new and modernization of serial heat exchangers are inextricably linked with the identification of their effectiveness. The effectiveness of the heat exchanger as part of the refrigeration machine was analyzed from three perspectives: economic, energy and thermodynamic using specific criteria. Considering modern thermodynamic analysis methods, which are based on determining irreversible losses in the processes of refrigeration machines, the entropy generation minimization method for analyzing heat exchangers was proposed. The choice of the method has provided an analysis of the processes in a particular heat exchanger of the refrigeration machine irrelatively of other elements, and analysis of one flow in the heat exchanger, which determines the energy side of the operation. It is shown on a particular example of the water condenser that using the entropy generation minimization method eliminates complex and unproductive calculations, providing the designer with the tools, the action principle of which is based on scientific and independent thermodynamic laws. The characteristics that meet the entropy generation minimum, ensure power-saving mode at the design stage and in a subsequent operation. The method is an alternative to a feasibility study and preferred for refrigeration machines due to the absence of cost indexes.

Performance Modeling and Analysis of IEEE 802.11 IBSS PSM in Different Traffic Conditions

The IEEE 802.11 standard for wireless local area networks defines a power management algorithm for Independent Basic Service Set (IBSS) allowing it to save critical battery energy in low powered wireless devices. The power management algorithm for IBSS uses beacon intervals (BIs) as the time unit, where every BI consists of an Announcement Traffic Indication Message (ATIM) window and a data window. The stations that have data to send need to go through a handshaking procedure in the ATIM window. If this handshaking is successful, the station remains awake in the data window and participates in the data communication. Otherwise, it goes into the sleep mode. This paper presents an analytical model to compute the throughput, expected delay and expected power consumption in an IEEE 802.11 IBSS in power save mode (PSM) for different traffic conditions in the network. The impact of data arrival rate, network size, and size of the BI on the performance of the IEEE 802.11 DCF in PSM is also analyzed. This analysis reveals a clear trade-off among throughput, delay, and average power consumption. The trade-off analysis is useful for designing efficient power consumption algorithms while maintaining the consistence performance of the network in terms of throughput and delay.

Enhancement of the IEEE 802.11 Power Saving Mode by Prioritized Reservations

The increasing demand for real-time applications in WSN has raised the requirement of protocols considering both energy efficiency and end-to-end delay. A PSM is proposed in the IEEE 802.11 protocol to reduce the power consumptions of wireless nodes. Wireless nodes can stay in doze mode and periodically wake up to retrieve the frames buffered in the APs. However, the 802.11 PSM is not such energy efficiency for WSN. First, in the process of the node's transmitting polling frames to AP, channel contentions may cause sensor nodes to deplete power quickly. Second, the mechanism of retrieving buffered frames can be inefficient since a polling frame is able to pick up only one data frame. Third, a prioritized service for urgent needs is not supported. In this paper, we propose a prioritized reservation scheme to enhance the IEEE 802.11 PSM. The concept of PSCW is suggested, during which PSM sensor nodes can retrieve the buffered frames using the reserved SPs, where the priorities of the PSM nodes are considered in scheduling the SPs. Through analytic models and discrete simulations, we show that our proposed mechanism outperforms the existing PSM schemes in terms of energy efficiency and prioritized services.

Characterization of Energy Consumption of a 802.11g Device

Wireless communications are continuously growing and the aim of reducing its energy consumption has recently become a research key point. This paper aims to analyze the influence of the configuration of a 802.11g device and its energy consumption. Five operational parameters are analyzed: two related to the network connection (bandwidth and datagram size), the device driver, Power Save Mode (PSM), and signal strength. By analyzing the energy saving values, we show the influence of each operational parameter on the energy consumption value. results show that a correct device configuration can save up to 83% in terms of energy consumption.

Анализ факторов влияющих на продольную устойчивость трактора

. In drawing up the working units machines can be aggregated with a tractor according to the three schemes - mounted, semi-mounted and trailed. The mounted aggregation method, compared with a trailing one, has several advantages. Location of mounted machine behind the rear wheels of the tractor at the idling time can cause the loss of longitudinal stability and controllability. Analytical dependences were established, influencing the longitudinal stability and controllability of the tractor. Each tractor has a minimum mass of the working machine, which is provided for the aggregation power-saving mode of transportation. The total weight of mounted units, consisting of the mass of a tractor, driven machine and ballast weight must not exceed the maximum mass of the tractor, disclosed in the technical specifications. The dependence, which is determined by the maximum mass of the working machine with a tractor, was determined. Setting additional ballast weights leads to displacement of the center of mass of the tractor in the direction of movement of the machine. The evaluation of longitudinal stability, determining the controllability, is measured according to the coefficient longitudinal stability control. The coefficient of a stock of longitudinal stability is determined by a formula of professor D. A. Chudakov. The analysis of the obtained relationships and the analysis of the factors, affecting on the tractor’s longitudinal stability and controllability were carried out.

Dynamic Configuration and Optimization of WiMAX Networks with Relay Power Saving Modes: Measurement-Based Scenario in a Hilly Region

This paper investigates the performances achievable by WiMAX networks deployed in various sectorization configurations, with and without relay stations (RSs). Further, it studies the dynamic adjustment of the configuration to serve traffic loads at different times of the day while maximising the use of opportunistic sleep modes by relays in conjunction with cell zooming, thereby saving energy. The configuration changes and invocation of opportunistic sleep modes also take into account coverage constraints. This paper first reports extensive propagation measurements that have been undertaken in Covilha, a hilly area of Portugal which presents a realistic and challenging propagation scenario. Using this scenario as the topographical basis, practical cellular planning results are then obtained and compared, using the dominant path and ray tracing (RT) functionalities of Winprop™. It is shown that without RSs present, the supported throughput is lower in practice because coverage is not 100 %. Further, for the case with omnidirectional cells, coverage reduces to only approximately 60 % if RSs go into sleep mode, and for the tri-sectored cells case coverage drops from 95.75 to 81.90 % (based on RT calculations) if RSs go into sleep mode. There is, however, still a reasonable economic performance in all cases. Additional results demonstrate that savings typically of 47.6 % in RSs' average power consumption can be achieved. These savings are shown to result in a financial saving for the operator of 10 % of the combined operational and maintenance cost. However, it is observed that such solutions have to be used cautiously in hilly regions due to challenges in maintaining coverage.

Bluesaver: A Multi-PHY Approach to Smartphone Energy Savings

WiFi effectively has two extremes: low power consumption and high latency, or low latency and high power consumption. WiFi Power Save Mode saves energy by trading added latency for less power consumption. Minimal latency but maximum power, on the other hand, is consumed with WiFi Active Mode. While research has advanced in mitigating these extremes, certain types of network traffic such as constant bitrate streaming make the contrast unavoidable. We introduce Bluesaver, which provides low latency and low energy by maintaining a Bluetooth and WiFi connection simultaneously. Bluesaver is designed at the MAC layer and is able to opportunistically select the most efficient connection for packets while still assuring acceptable latency. We implement Bluesaver on an Android phone and Access Point and show that we can save more than 25% energy over existing solutions and attain the capability of quickly adapting to changes in network traffic.

A Practical PSM Scheme for Varying Server Delay

Today, many individuals use smartphones or other battery-powered mobile devices equipped with Wi-Fi to access the Internet. Since the network interface cards (NICs) often use a substantial portion of available energy, schemes such as the 802.11 power saving mode (PSM) have been used to limit the amount of time a NIC is awake in an operable state so as to extend battery life. However, since the NIC cannot retrieve packets while sleeping, PSM may negatively impact packet delay. These delays are also unbounded and can significantly increase communication time, particularly in a mobile environment where server delays may change drastically. To mitigate this, we present PSM-AW: a PSM with adaptive wake-up. PSM-AW is a client-side solution that allows the client device to sleep for a maximum time interval while still keeping a tight bound on performance. We present and prove a bound on performance using PSM-AW and demonstrate its effectiveness through extensive simulations and experiments.

Power-Efficiency Considerations for Adaptive Long-Haul Optical Transceivers

Adaptive optical transceivers are considered among the candidates for future optical communications, especially in long-haul and metro applications. In this paper, the hardware requirements of the adaptive digital coherent transceivers are studied. Challenges and solutions for power-efficient implementation of the electro-optical front-end and digital signal processor are investigated. Different power-saving modes are also presented.

Assessing the impact of the CPU power-saving modes on the task-parallel solution of sparse linear systems

We investigate the benefits that an energy-aware implementation of the runtime in charge of the concurrent execution of ILUPACK—a sophisticated preconditioned iterative solver for sparse linear systems—produces on the time-power-energy balance of the application. Furthermore, to connect the experimental results with the theory, we propose several simple yet accurate power models that capture the variations of average power that result from the introduction of the energy-aware strategies as well as the impact of the P-states into ILUPACK’s runtime, at high accuracy, on two distinct platforms based on multicore technology from AMD and Intel.