Adaptive power saving mechanism considering the request period of each initiation of awakening in the IEEE 802.16e system

Performance of the IEEE 802.16 e power management is mainly affected by two operating parameters: the minimum sleep interval (T _min) and the maximum sleep interval (T _max), in sleep-mode operation. To enhance the performance, this letter proposes a new power saving mechanism, which adaptively controls these parameters by considering the request period of each initiation of awakening (Tint)- The numerical analysis and simulation results show that this mechanism can achieve better energy conservation with reasonable response delay of Medium Access Control (MAC) Service Data Units (SDUs) than the standard operation.     

Energy saving mechanism in the IEEE 802.16e wireless MAN

In this paper, we study energy consumption for the IEEE 802.16e broadband wireless access (BWA) network, A mobile subscriber station goes to sleep-mode after negations with the base station and temporarily wake-up periodically for a short interval to check whether there is downlink traffic to it to decide whether it goes to wake-mode or continues to be in the sleep-mode. The sleep interval is increased exponentially upon no arrival traffic. We analytically model the sleep-mode scheme and validate the model with simulations.     

Performance analysis of the IEEE 802.16e power management for the initiations of awakening

To increase battery life in IEEE 802.16e systems, it is essential to efficiently manage energy in mobile stations. The sleep-mode operation in power management helps to increase the life of a station by saving energy consumption. In power management, there are two important performance metrics energy consumption and the response delay of awakening medium access control (MAC) service data unit (SDU). While in a base station (BS) initiation of awakening, the two performance metrics should be simultaneously considered, in a mobile subscriber station (MSS) initiation of awakening, the response delay is not considered because it is self-operational. There performance metrics are affected by the minimum sleep interval (Tmin), the maximum sleep interval (Tmax), and the average interarrival time of awakening MAC SDUs (TI) during sleep-mode operation. Therefore, it is imperative to evaluate the two initiations of awakening depending on TI. To reach a fuller understanding of the performance, this paper shows an analytical mode and simulations results for the standard sleep-mode operation in the IEEE 802.16e MAC.     

IEEE 802.16e/m energy‐efficient sleep‐mode operation with delay limitation in multibroadcast services

Mobile Worldwide Interoperability for Microwave Access networks usually provide flexible sleep‐mode operations that allow mobile stations to conserve energy during sleep or active mode. For example, the IEEE 802.16e/m standard presents three power‐saving classes that can be associated with different types of network connections to decrease the power consumption of mobile stations. However, previous studies failed to fully use the sleep‐mode features to save energy of a mobile station while simultaneously maintaining unicast and multicast/broadcast connections. This study proposes an energy‐efficient packet scheduling algorithm for both multicast and broadcast services that does not violate the QoS requirements of real‐time connections. The proposed activity aggregation selection mechanism approach can minimize total power consumption of mobile stations in one cell and simultaneously satisfy the QoS of real‐time connections. This method improves energy efficiency for IEEE 802.16e/m and the activity aggregation selection mechanism approach can optimize sleeping mode features to save the energy of mobile stations with overlapping connection packets The simulations in this study verified the proposed approach.Copyright © 2012 John Wiley & Sons, Ltd.     

Efficient performance analysis of newly proposed sleep-mode mechanisms for IEEE 802.16m in case of correlated downlink traffic

There is a considerable interest nowadays in improving energy efficiency of wireless telecommunications. The sleep-mode mechanism in WiMAX (IEEE 802.16) and the discontinuous reception (DRX) mechanism of LTE are prime examples of energy saving measures. Recently, Samsung proposed some modifications on the sleep-mode mechanism, scheduled to appear in the forthcoming IEEE 802.16m standard, aimed at minimizing the signaling overhead. In this work, we present a performance analysis of this proposal and clarify the differences with the standard mechanism included in IEEE 802.16e. We also propose some special algorithms aimed at reducing the computational complexity of the analysis.     

Delay versus energy consumption of the IEEE 802.16e sleep-mode mechanism

We propose a discrete-time queueing model for the evaluation of the IEEE 802.16e sleep-mode mechanism of Power Saving Class (PSC) I in wireless access networks. Contrary to previous studies, we model the downlink traffic by means of a Discrete Batch Markov Arrival Process (D-BMAP) with Ν phases, which allows to take traffic correlation into account. The tradeoff between energy saving and increased packet delay is discussed. In many situations, the sleep-mode performance improves for heavily correlated traffic. Also, when compared to other strategies, the exponential sleep-period update strategy of PSC I may not always be the best.     

IEEE 802.16e MAC层能量控制机制的研究

IEEE 802.16e标准是支持终端移动性的无线城域网接入标准.由于在移动网络中终端主要是由电池供电的,因此如何有效的控制终端能耗成为一个非常重要的问题.本文首先介绍了IEEE 802.16e标准建议睡眠模式的操作机制和操作参数.然后采用一致的模型,使用概率统计方法对睡眠模式节约能耗的效果及其对下行帧时延的影响进行了分析.最后采用Matlab工具对分析结果进行了仿真和讨论.     

Design of Predictive and Dynamic Energy-Efficient Mechanisms for IEEE 802.16e

Three predictive and dynamic sleep time planning (PDSTP) energy-efficient mechanisms are proposed in this paper to simultaneously improve energy efficiency and packet delay for IEEE 802.16e. To estimate the time instant when a mobile station (MS) should wake up for receiving downlink packets, a prediction method is designed. With the predicted time instant, an MS is then allowed to sleep as much as possible using multiple maximum sleep intervals followed by a smaller sleep interval before the predicted time instant. After the predicted time instant, a few smaller sleep intervals with a trend of constant level (CL), exponential decrease (ED), or linear decrease (LD) can be further arranged. To react to the outlier of prediction, exponential increase for sleep intervals can be extended. The combination of the aforementioned designs then forms our three proposed mechanisms, namely, PDSTP-CL, PDSTP-ED, and PDSTP-LD. Via simulations, we show that PDSTP-CL not only performs better than PDSTP-ED and PDSTP-LD under general situations but also outperforms the standard sleep mode operation of the type-I power saving class (PSC-I) in IEEE 802.16e and the exponential sleep time backoff mechanism (ESTBM) in the literature in terms of energy efficiency and packet delay.     

On the performance optimization for the cloud architecture with sleep-mode and registration service

In order to balance the energy conservation and the service quality for anonymous users,a novel sleep-mode based architecture with the free cloud service and the registration cloud service was proposed.Regarding the free cloud service as the first service,the registration cloud service as the second service and the sleep sate as the vacation,a partial asynchronous multiple vacation queueing model with a second optional service was built.Applying the method of a matrix-geometric solution,the steady-state distribution of the queueing model was derived,and then the energy saving rate of system as well as the average response time of anonymous users were estimated.By considering the benefits from accessing the cloud service and the time cost on waiting for the cloud service,benefit functions were constructed.Numerical results were carried out to reveal the relationship between Nash equilibrium arrival rate and social optimal arrival rate of anonymous users.The proposed cloud architecture provides a theoretical basis for social optimization.     

Performance analysis of the IEEE 802.16e sleep mode for correlated downlink traffic

In this paper, we evaluate the performance of the IEEE 802.16e sleep mode mechanism in wireless access networks. This mechanism reduces the energy consumption of a mobile station (MS) by allowing it to turn off its radio interface (sleep mode) when there is no traffic present at its serving base station (BS). After a sleep period expires, the MS briefly checks the BS for data packets and switches off for the duration of another sleep period if none are available. Specifically for IEEE 802.16e, each additional sleep period doubles in length, up to a certain maximum. Clearly, the sleep mode mechanism can extend the battery life of the MS considerably, but also increases the delay at the BS buffer. For the performance analysis, we use a discrete-time queueing model with general service times and multiple server vacations. The vacations represent the sleep periods and have a length depending on the number of preceding vacations. Unlike previous studies, we take the (short-range) traffic correlation into account by assuming a D-BMAP arrival process, i.e. the distribution of the number of packet arrivals per slot is modulated by the transitions in a Markov chain with N background states. As results, we obtain the distribution of the number of packets in the queue at various sets of time epochs, the distribution of the packet delay and the antenna activity rate. We apply these results to the IEEE 802.16e sleep mode mechanism with correlated downlink traffic. By means of some examples, we show the influence of both the configuration parameters and the traffic correlation on the delay and the energy consumption.     

DC-Gear: 延时约束型无线传感网占空比调控策略研究

Many Wireless Sensor Network (WSN) systems are deployed in unattended areas using non-rechargeable batteries. To enable sustainable operations, most WSN systems employ duty-cycling mechanisms, such as Low Power Listening (LPL). For reliable delivery of each packet with LPL, the sender has to transmit a preamble that is long enough to span over a complete sleep interval of the receiver. In this way, the sensor nodes avoid idle listening, however, at the cost of remarkably increased end-to-end delay of multi-hop packet transmissions. To address this issue, in this paper we propose a new duty-cycling mechanism called DC-Gear. DC-Gear exploits a“sleep less but save more” phenomenon, which means increasing the duty cycle in a timely and appropriate manner while minimizing the overall energy cost and satisfying the end-to-end delay constraint. We have implemented DC-Gear with TelosB motes and demonstrated its performance advantages through extensive experiments.     

Stochastic modeling for energy efficiency in modified directional discontinuous reception for LTE-5G networks

Fifth-generation (5G) networks deal with high-frequency data rates, ultra-low latency, more reliability, massive network capacity, more availability, and a more uniform user experience. To validate the high-frequency rates, 5G networks engage beam searching operation. By adopting a beam searching state between the short and long sleep, one can reduce the system's delay. The energy consumption of user equipment (UE) in 5G networks is much higher than in the 4G networks. To reduce the energy consumption and increase the energy saving in UE, Long-Term Evolution (LTE)-5G networks adopt the discontinuous reception (DRX) scheme with a fixed number of short sleep. LTE-DRX without beam search operation (i.e., beam alignment) cannot work in 5G networks. Hence, keeping this scenario in mind, we have modeled a new modified directional discontinuous reception (MD-DRX) mechanism for LTE-5G networks. The MD-DRX mechanism captures the behavior of a beam searching, an inactive, an active, a long sleep, an ON, and a short sleep states. The short sleep state consists of a maximum $M$ short sleep. To get the optimal energy saving and energy consumption (i.e., energy efficiency) from the MD-DRX mechanism, it is required to check the system's throughput. The trade-off between energy saving/energy consumption and throughput will provide the system's optimal energy saving and optimal energy consumption. In this paper, we have obtained the system's optimal energy saving and throughput by optimizing the maximum short sleep and short sleep duration. To get the energy efficiency for LTE-5G networks, the trade-off between average energy consumption/energy saving and throughput is shown.     

Wireless sensor networks with energy harvesting technologies: a game-theoretic approach to optimal energy management

Energy harvesting technologies are required for autonomous sensor networks for which using a power source from a fixed utility or manual battery recharging is infeasible. An energy harvesting device (e.g., a solar cell) converts different forms of environmental energy into electricity to be supplied to a sensor node. However, since it can produce energy only at a limited rate, energy saving mechanisms play an important role to reduce energy consumption in a sensor node. In this article we present an overview of the different energy harvesting technologies and the energy saving mechanisms for wireless sensor networks. The related research issues on energy efficiency for sensor networks using energy harvesting technology are then discussed. To this end, we present an optimal energy management policy for a solar-powered sensor node that uses a sleep and wakeup strategy for energy conservation. The problem of determining the sleep and wakeup probabilities is formulated as a bargaining game. The Nash equilibrium is used as the solution of this game.     

Research on Base Station Sleeping Mechanism of User Connections in Ultra Dense Network

On the basic of traditional macro cellular networks, ultra dense networks deploy plenty of low-power nodes working with maximum power, which provide superior communication quality and produce more energy consumption in networks. Aiming at the problem of wasting network resources caused by low-power nodes during low-load period in ultra dense networks, we study a kind of base station sleeping mechanism based on user connections. When the network loads are low, the connections between users and base stations (BSs) are sensed by environment awareness technology. Then, the connection relationship is used to establish a connection matrix. After that we use the established connection matrix to build a weighted bipartite graph. Taking the users’ QoS and the load of BSs into account, we build a weight matrix by weighting the two as the weights of the bipartite graph. We get the optimal connection between users and base stations by constantly optimizing the value of the connection matrix. By modeling, we transform the optimization problem into a 0–1 integer programming problem and get the optimal connection by Particle Swarm Optimization algorithm. Finally, the sleeping mechanism is executed according to this connection matrix, and we achieve the goal of energy conservation by closing low-load BSs.     

UEs Power Reduction Evolution with Adaptive Mechanism over LTE Wireless Networks

At present, the major drawback for mobile phones is the issue of power consumption. As one of the alternatives to decrease the power consumption of standard, power-hungry location-based services usually require the knowledge of how individual phone features consume power. A typical phone feature is that the applications related to multimedia streaming utilize more power while receiving, processing, and displaying the multimedia contents, thus contributing to the increased power consumption. There is a growing concern that current battery modules have limited capability in fulfilling the long-term energy need for the progress on the mobile phone because of increasing power consumption during multimedia streaming processes. Considering this, in this paper, we provide an offline meaning sleep-mode method to compute the minimum power consumption comparing with the power-on solution to save power by implementing energy rate adaptation (RA) mechanism based on mobile excess energy level purpose to save battery power use. Our simulation results show that our RA method preserves efficient power while achieving better throughput compared with the mechanism without rate adaptation (WRA).     

Energy efficiency in wireless sensor networks using sleep mode TDMA scheduling

Power saving is a very critical issue in energy-constrained wireless sensor networks. Many schemes can be found in the literature, which have significant contributions in energy conservation. However, these schemes do not concentrate on reducing the end-to-end packet delay while at the same time retaining the energy-saving capability. Since a long delay can be harmful for either large or small wireless sensor networks, this paper proposes a TDMA-based scheduling scheme that balances energy-saving and end-to-end delay. This balance is achieved by an appropriate scheduling of the wakeup intervals, to allow data packets to be delayed by only one sleep interval for the end-to-end transmission from the sensors to the gateway. The proposed scheme achieves the reduction of the end-to-end delay caused by the sleep mode operation while at the same time it maximizes the energy savings.     

An intelligent hybrid MAC protocol for a sensor-based personalized healthcare system

Sensors based on personalized healthcare systems have been widely used in the medical field. However, energy limitations have greatly hindered the further development of medical sensors. For the traditional Medium Access Control (MAC) protocol, the duration of low-power listening is fixed because it ignores that the available energy of sensors is different in some situations, which leads to a high delay and low energy utilization. In this paper, a Maximum Listening Length MAC (MLL-MAC) protocol is proposed to fully utilize the energy in the sensor-based systems. The MLL-MAC protocol is an improvement of the Receiver-Initiated (RI) MAC protocol. The main advance is that the sensor node performs the following additional operations: (1) The sender sends a beacon when it wakes up and sends data, thus establishing a communication link with the receiver in the listening state; (2) The receiver keeps listening as long as possible to reduce the delay when it wakes up and listens to the channel, which is different from the previous strategy in which the node turns into a sleep state immediately without receiving data. Furthermore, the sensor node can dynamically determine whether to send beacons and prolong listening duration according to its available energy level. The MLL-MAC protocol is evaluated through theoretical analysis and experimental results. The results show that, compared with the RI-MAC protocol, the MLL-MAC protocol can reduce the average end-to-end delay by 41.4% and improve the energy utilization by 15.1%.     

Recovery from control plane failures in the LDP signalling protocol

The Label Distribution Protocol (LDP) needs to recover its state information after a control plane failure, so that the established connections in the data plane are not disrupted by any new connection set-up. We propose a backup mechanism to store the LDP state information in an upstream neighbour node. The backup LDP state information is synchronized with the original LDP state information in a downstream node when the LDP sets up or tears down connections. Then, we propose a two-step LDP state information recovery, which uses a fast LDP state information recovery to recover what labels are idle before a control plane failure, and a detailed LDP state information recovery to fully recover all LDP state information. The fast LDP state information recovery is realized as part of the LDP initialization, allowing a restarting LDP session to process new connection set-up requests as soon as possible, without interfering existing connections. The detailed LDP state information recovery performs in the background in parallel to the normal LDP operations. When an LDP connection teardown requires the LDP state information that has not yet been recovered, an on-demand query based LDP state information recovery is conducted. The performance analysis demonstrates that our proposal achieves fast LDP recovery for the core label state information. It features scalable LDP state information storage and recovery by only involving a pair of neighbour nodes.     

Single- and multi- user uplink energy-efficient resource allocation algorithms with users’ power and minimum rate constraint in OFDMA cellular networks

In this paper, single- and multi- user Resource Allocation (RA) optimization problems considering transmit power and minimum rate constraint of Mobile Station (MS) for maximizing MS’ energy efficiency, measured as bits-per-joule (bpj), are addressed. Assume channel state information of all MSs is known by base station. We propose uplink RA algorithms, performing subcarrier assignment and power allocation, for optimizing bpj of MS in a single-cell OFDMA-based cellular network for both single- and multi- user scenarios. In the single-user case, we propose RA algorithms, which utilize the closed-form solution derived by applying Lambert-W function and an iterative approach based on Karush–Kuhn–Tucker conditions respectively to achieve optimal bpj of MS. In the multi-user case, centralized iterative multi-user RA algorithms for maximizing sum of MS’ bpj, performing joint subcarrier assignment and power allocation iteratively, are proposed by utilizing the proposed single-user RA schemes. In particular, tradeoffs between energy efficiency and spectral efficiency are fully investigated, and the influence of MS’ power and minimum rate constraints on bpj performance is also studied. The effectiveness of proposed algorithms is presented by numerical experiments. Numerical results demonstrate the proposed algorithms can enhance bpj significantly with limited loss of total throughput compared to the sum-rate maximization algorithm (in Moretti et al., IEEE Trans Veh Technol 60(4):1788–1798, 2011).     

Enhanced power saving through increasing unavailability interval in the IEEE 802.16e systems

The power saving mechanisms of the current IEEE 802.16e system are designed to take no consideration of the harmonization between power saving classes (PSCs) I and II. Using the IEEE 802.16e standard as a basis, we propose a dynamic power saving mechanism that increases unavailability interval when a mobile station (MS) uses PSCs. The proposed mechanism adjusts the timing of the sleep window of PSC I to maximize the unavailability interval of the MSs. As a result, the proposed scheme achieves power saving of the MSs. Through numerical analysis and simulations, we show that the proposed mechanism can reduce the power consumption of the MSs considerably compared with conventional mechanisms.