Power Saving Class Research Articles

An Improvement of Power Saving Class Type II Algorithm in WiMAX Sleep-mode

Because of the fact that users can connect to a WiMAX (IEEE 802.16) network wirelessly with large-scale movement capability, it is inevitable that they cannot access electrical power sources at their desired time. As a result, a mechanism is needed to reduce power consumption; and therefore three power saving classes have been defined in WiMAX that each one is designed for a specific application. Although using a suitable power saving class (PSC) can reduce power consumption significantly, but lack of cross-layer coordination can reduce the efficiency of the power saving mechanism. Since real-time services which are related to power saving class type II (PSC II) have great importance and vast applications, an improved PSC II algorithm for WiMAX is proposed in this paper which not only guarantees WiMAX quality of service (QoS), but also makes the cross-layer coordination using a proactive buffer resulting in less power consumption. There is also a comparison made between the performance of the proposed algorithm and the predefined PSC II algorithm in WiMAX using computer simulations and it shows that using the proposed algorithm reduces power consumption by 60 percent, while WiMAX QoS is still guaranteed.

Maximizing power saving with state transition overhead for multiple mobile subscriber stations in WiMAX

In the IEEE 802.16e/m standard, three power saving classes (PSCs) are defined to save the energy of a mobile sub-scriber station (MSS). However, how to set the parameters of PSCs to maximize the power saving and guarantee the quality of service is not specified in the standard. Thus, many algorithms were proposed to set the PSCs in IEEE 802.16 networks. However, most of the proposed algorithms consider only the power saving for a single MSS. In the algorithms designed for multiple MSSs, the sleep state, which is set for activation of state transition overhead power, is not considered. The PSC setting for real-time connections in multiple MSSs with consideration of the state transition overhead is studied. The problem is non-deterministic polynomial time hard (NP-hard), and a suboptimal algorithm for the problem is proposed. Simulation results demonstrate that the energy saving of the proposed algorithm is higher than that of state-of-the-art algorithms and approaches the optimum limit.

Development and Analysis of Power Saving Models for Energy Conservation in IEEE 802.16m Networks: Towards Green Communication

Mobile stations (MS) in IEEE 802.16m network undergo frequent battery drain out with mobile Internet services due to inappropriate power saving model (PSM) and power saving class (PSC). Although, PSM models for mobile Internet based services have been available in literature, they do not converge towards the best effort traffic requirements, namely, web browsing and file transfer protocol (FTP). Hence, to conserve energy towards green communication, PSMs are developed by considering the scaling, shaping and location or threshold parameter of the web browsing and FTP traffics. With these proposed PSMs, the MS with conventional PSC suffer from high-energy consumption and response delay as the interarrival time of the traffic increases. Hence, a modified PSC is proposed for the aforementioned traffics. Although the modified PSC performs well with web browsing traffic, it needs improvement under FTP traffic. Therefore, an adaptive PSC is proposed to improve the system performance with FTP traffic. With web browsing traffic, the proposed PSC reduces the response delay and energy consumption by 79.38 and 73.26 %, respectively, than the existing PSC. Also, with FTP traffic, the proposed PSC lessens the response delay and energy consumption by 62.58 and 41.79 %, respectively, than the existing PSC.

Analysis of Power Saving Class II Traffic in IEEE 802.16E with Multiple Sleep State and Balking

Abstract The battery life of Mobile Stations in IEEE 802.16e can be extended substantially by applying the sleep mode mechanism. This paper studies an effcient method to analyze the performance of the power saving class type II for delay sensitive traffc in multiple sleep state. The incoming data frames may join or balk the buffer due to impatience with some probability. We present an M/M/1/N queueing model with balking and multiple vacations in order to exhibit the self-similar property of IEEE 802.16e. We develop a cost function to determine the optimal service rate that minimizes the total expected cost. Various performance indices such as the average number of data frames in the system, the mean waiting time of the data frame in the system, the the average balking rate due to impatience, etc. have been presented. Numerical results are provided to show the inuence of various parameters on the behavior of the system. The proposed model provides a tradeoff between the average abandon rate and the power consumption.

Investigations on enhanced power saving mechanism for IEEE 802.16m network with heterogeneous traffic

In this paper, power management mechanisms for IEEE 802.16m network using power saving class (PSC) are suggested for heterogeneous traffic. The proposed algorithms, namely, combined cyclic binary exponent (CCBE), combined anti-cyclic binary exponent (CABE) and combined truncated binary exponent (CTBE) are derived by combining the existing PSC-I and PSC-II with appropriate modifications. The mobile station (MS) with existing PSC-I, PSC-II and combined PSC (CPSC) suffers from high response delay and/or more energy consumption if the packet interarrival time of heterogeneous traffic increases. The main reason behind reduced performance is due to the fixed position and duration of the listen interval in these PSC. To optimize the listen interval, the sleep interval of PSC-I is customized to realize the three proposed algorithms. In addition, the modified sleep interval of PSC-I is combined with fixed sleep interval of PSC-II. Finally, the resultant combined PSC is formulated by applying a scaling rule that minimizes and positions the duration of listening interval by referring the current listen interval of PSC-II. The performance of three PSC is studied by varying the interarrival time, minimum and maximum sleep intervals at the MS. It is observed with CCBE algorithm, the number of listen intervals, response delay and power consumption is reduced by 8.02%, 22.71% and 15.60%, than CABE, respectively. Similarly, CCBE shows an improvement of 28.62%, 25.24% and 31.97% than CTBE algorithm. Also, the performance of CCBE is improved by 57.82%, 89.67% and 64.16% than conventional CPSC algorithm.

Power saving mechanism for VoIP services over WiMAX systems

The IEEE 802.16 system provides the power saving class (PSC) type II as a power saving algorithm for voice over internet protocol (VoIP) service, but it is not designed to consider silent periods of VoIP traffic. The main objective of this paper is to introduce a power conservation mechanism that combines power saving modes class I, class II and class III which is applicable to VoIP service with silence suppression which basically follows PSC II during talk-spurt periods but in silence periods it combine PSC I and PSC III. According to experimental results, more than 96 % power reduction can be achieved in mutual silence period by using the proposed VoIP power saving mechanism for VoIP services during silent periods with respect to the Quality of Services.

Performance evaluation and optimisation guidelines for the Type II power-saving class of mobile World Interoperability for Microwave Access

In Mobile World Interoperability for Microwave Access (also known as IEEE802.16e), a standard power-saving mechanism (PSM) that alternates between sleep and wake modes is adopted to extend the lifetime of mobile stations (MSs), but it simultaneously induces a medium access control (MAC) service data unit (SDU) response delay. The standard PSM defines three power-saving classes (PSCs), among which Type I is based on a binary-exponential increase in the sleep window, and Type II is based on a constant sleep window. Over the years, most studies have mainly focused on PSC Type I, while only a few have considered Type II. This study derives several analytical models of PSC Type II and evaluates the power consumption and MAC SDU response delay performance. Based on the derived models, an optimised power under delay-bound mechanism (OPDBM) is proposed to find the optimal initial sleep window parameter that minimises the power consumption of an MS while satisfying a given MAC SDU response delay constraint. Both numerical analysis and simulation experiments show that the OPDBM effectively minimises the power consumption of an MS while guaranteeing any imposed/required MAC SDU response delay constraint in a wide variety of environments.

Improved Power Saving Mechanism to Increase Unavailability Interval in IEEE 802.16e Networks

To manage limited energy resources efficiently, IEEE 802.16e specifies sleep mode operation. Since there can be no communication between the mobile station (MS) and the serving base station (BS) during the unavailability interval, the MS can power down its physical operation components. We propose an improved power saving mechanism (iPSM) which effectively increases the unavailability interval of Type I and Type II power saving classes (PSCs) activated in an MS. After investigating the number of frames in the unavailability interval of each Type II PSC when used with Type I PSC, the iPSM chooses the Type II PSC that yields the maximum number of frames in the unavailability interval. Performance evaluation confirms that the proposed scheme is very effective.

Performance Analysis of Power Saving Class of Type I for Voice Service in Two-Way Communication in IEEE 802.16e

In IEEE 802.16e, power saving is one of the important issues for battery-powered mobile stations (MSs). We present a performance analysis of power saving class (PSC) of type I in IEEE 802.16e standard for voice over Internet protocol (VoIP) service with silence suppression in two-way communication. On-off pattern of a voice user in two-way communication is characterized by the modified Brady model, which includes short silence gaps less than 200ms and talkspurt periods shorter than 15ms, and so differs from the Brady model. Our analysis of PSC I follows the standard-based procedure for the deactivation of the sleep mode, where a uplink packet arrival during a mutual silence period wakes up the MS immediately while a downlink packet arrival waits to be served until the next listening window. We derive the delay distribution of the first downlink packet arriving during a mutual silence period, and find the dropping probability of downlink packets since a voice packet drops if it is not transmitted within maximum delay constraint. In addition, we calculate the average power consumption under the modified Brady model. Analysis and simulation results show that the sleep mode operation for the MS with VoIP service yields 32 ∼ 39% reduction in the power consumption of the MS. Finally we obtain the optimal initial/final-sleep windows that yield the minimum average power consumption while satisfying QoS constraints on the packet dropping probability and the maximum delay.

Managing Power Saving Classes in IEEE 802.16 Wireless MANs: A Fold-and-Demultiplex Method

In IEEE 802.16, power management at the Mobile Subscriber Station (MSS) side is always an important issue. The standard defines three types of power saving classes (PSCs). A PSC can bind one or multiple traffic flows. However, given multiple flows in an MSS, the standard does not define how to form PSCs, how to organize the cooperation of multiple PSCs to obtain better energy efficiency, and how to guarantee QoS of these flows. Given a set of flows and their QoS parameters, the objective of this paper is to define multiple PSCs and their listen-and-sleep-related parameters and packet-scheduling policy such that the unavailability intervals of the MSS can be maximized and the QoS of each flow can be guaranteed. To achieve this, we propose a novel fold-and-demultiplex method for an IEEE 802.16 network with PSCs of types I and II together with an earliest-next-bandwidth-first packet scheduler. Given a set of traffic flows in an MSS, the fold-and-demultiplex method first gives each flow a tentative PSC satisfying its bandwidth requirement. Then we fold them together into one long series so as to calculate the total bandwidth requirement. Finally, we demultiplex the series into multiple PSCs, each supporting one or multiple flows. It ends up with high energy efficiency of MSSs while meets flows' bandwidth requirements. Furthermore, our packet scheduler ensures that real-time flows' delay constraints can be met. To the best of our knowledge, this is the first result offering bounded packet delays under MSS's sleep-and-listen behaviors.

Performance evaluation of a power saving mechanism in IEEE 802.16 wireless MANs with bi-directional traffic

One of the most important ways for extending the battery lifetime of Mobile Stations (MSs) in a wireless Metropolitan Area Network (MAN) is to conserve the power consumption effectively. When a power saving mechanism with the sleep mode in IEEE 802.16-2009 is used, the system will be in a sleep state and the energy will be saved if both the Uplink (UL) and the Downlink (DL) are idle. In this paper, we present a new mathematical analysis for the system model with synchronous multiple vacations to capture the working principle of the Power Saving Class (PSC) type III in IEEE 802.16-2009 by taking into account the bi-directional traffic (the UL traffic and DL traffic together). By using the methods of a semi-Markov process and a two-dimensional embedded Markov chain, we derive the steady-state probability distribution of the system. Noting that the transmission of UL data frame will not be influenced by the sleep mode, but the sleep mode can be terminated by the arrival of UL data frames, we give the formula for the average delay of the DL data frames taking the bi-directional traffic into consideration. Moreover, we also present the expression for the energy saving ratio. Analytical results and simulation results are provided to investigate and validate the influence of the system parameters on the system performance. Finally, considering the trade-off between the average delay of data frames and the energy saving ratio, we develop a cost function to determine the optimal length of the sleep window in order to maximize the energy saving ratio while satisfying the Quality of Service (QoS) constraint on the average delay of data frames.

Per-flow sleep scheduling for power management in IEEE 802.16 wireless networks

Power management is a critical issue in IEEE 802.16 wireless networks. In the standard, a power saving class ( PSC) of type II is defined to support real-time traffic flows. It allows a flow to switch periodically between active and sleep states to save energy. However, previous studies either consider adjusting start frames of PSCs by assuming that the PSCs are already given or assume one single PSC to accommodate all flows in a mobile station, thus leading to higher energy cost. This paper proposes two “per-flow” sleep scheduling schemes, which assign one PSC to each real-time flow according to its QoS parameters. This leads to less energy consumption, more efficient use of bandwidth, and more compact listening windows. We also prove that deciding whether a given scheduling problem is solvable can be reduced to a maximum matching problem, which is computationally tractable. Simulation results show that such a per-flow scheduling does perform much closer to the active ratio lower bound and achieve higher resource utilization than previous schemes.

Performance evaluation of a power saving mechanism in IEEE 802.16 wireless MANs with bi-directional traffic

One of the most important ways for extending the battery lifetime of Mobile Stations (MSs) in a wireless Metropolitan Area Network (MAN) is to conserve the power consumption effectively. When a power saving mechanism with the sleep mode in IEEE 802.16-2009 is used, the system will be in a sleep state and the energy will be saved if both the Uplink (UL) and the Downlink (DL) are idle. In this paper, we present a new mathematical analysis for the system model with synchronous multiple vacations to capture the working principle of the Power Saving Class (PSC) type III in IEEE 802.16-2009 by taking into account the bi-directional traffic (the UL traffic and DL traffic together). By using the methods of a semi-Markov process and a two-dimensional embedded Markov chain, we derive the steady-state probability distribution of the system. Noting that the transmission of UL data frame will not be influenced by the sleep mode, but the sleep mode can be terminated by the arrival of UL data frames, we give the formula for the average delay of the DL data frames taking the bi-directional traffic into consideration. Moreover, we also present the expression for the energy saving ratio. Analytical results and simulation results are provided to investigate and validate the influence of the system parameters on the system performance. Finally, considering the trade-off between the average delay of data frames and the energy saving ratio, we develop a cost function to determine the optimal length of the sleep window in order to maximize the energy saving ratio while satisfying the Quality of Service (QoS) constraint on the average delay of data frames.

Enhanced Power Saving Mechanism for Type I and Type II Power Saving Classes in IEEE 802.16e

A mobile station (MS) in an IEEE 802.16e network manages its limited energy using the sleep mode operation. An MS can power down its physical operation components during the unavailability interval of the sleep mode. To reduce energy consumption by increasing the unavailability interval, this paper proposes an enhanced power saving mechanism (ePSM) when both activated Type I and Type II power saving classes (PSCs) exist in an MS. A performance evaluation confirms that ePSM results in the improved performance in terms of the unavailability interval as well as the energy consumption than conventional schemes.

Statistical Control Approach for Sleep-Mode Operations in IEEE 802.16m Systems

The power-saving class of type I (PSC I), which is one of the sleep-mode operations specified in the IEEE 802.16 e standard, is designed to reduce power consumption for nonreal-time traffic. However, the inefficiency of the PSC I comes from the configuration of its operation and the utilized mechanism of binary-exponential traffic detection. Based on the concepts of IEEE 802.16 m sleep-mode operation, a statistical sleep window control (SSWC) approach is proposed to improve the energy efficiency of a mobile station (MS) with nonreal-time downlink traffic in this paper. The SSWC approach constructs a discrete-time Markov-modulated Poisson process (dMMPP) for representing the states of nonreal-time traffic. Furthermore, a partially observable Markov decision process (POMDP) is exploited within the SSWC approach to conjecture the present traffic state. Based on the estimated traffic state and the considerations of tolerable delay and/or queue size, two suboptimal policies, including the sleep ratio-based (SR) and energy cost-based (EC) policies, are proposed within the SSWC approach. The efficiency of the proposed SSWC approach is evaluated and compared via simulations. Simulation results show that the proposed SSWC approach outperforms the conventional IEEE 802.16 e PSC I and the evolutional PSC I of the IEEE 802.16 m system in terms of both energy conservation and packet delay.

Performance Analysis and Evaluation of Wireless Mobile Networks using the Power Saving Class Type III in IEEE 802.16e with Self-similar Traffic

Performance Analysis and Evaluation of Wireless Mobile Networks using the Power Saving Class Type III in IEEE 802.16e with Self-similar Traffic

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.

Performance analysis and evaluation for power saving class type III in IEEE 802.16e network

In this paper, we present an enhanced power saving class (PSC)type III by introducing a sleep-delay mechanism into theconventional PSC type III in the IEEE 802.16e network. Twomultiple vacation queueing models: without sleep-delay and withsleep-delay, are built to capture the working principles of theconventional PSC type III and the enhanced PSC type III,respectively. Then, using the boundary state variable theorymethod, we analyze these queueing models and give the performancemeasures in terms of the switch ratio, the power saving ratio, theaverage response time and the system utility for both theconventional and the enhanced power saving schemes. Next,numerical results are given to demonstrate the dependencyrelationships between the performance measures and the sleepwindow size. Moreover, we compare the performance of the bothsystems without sleep-delay (the conventional PSC type III) andwith sleep-delay (the enhanced PSC type III) to validate theeffect of the sleep-delay mechanism in the enhanced PSC type IIIproposed in this paper. Finally, we also construct a cost functionto determine the optimal time length of the sleep-delay timer forminimizing the cost function.

The Power-Saving Mechanism With Periodic Traffic Indications in the IEEE 802.16e/m

In IEEE Standards 802.16e (air interface standard for MWiMAX) and 802.16m (evolution of MWiMAX for IMT-Advanced), power saving is one of the important issues for battery-powered mobile stations (MSs) due to mobility. According to the IEEE 802.16e standard, when an MS switches from awake mode to sleep mode, the MS is required to send a sleep request (MOB-SLP-REQ) message and to receive a sleep response (MOB-SLP-RSP) message. In this paper, we propose a new sleep mode scheme called the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">power-saving mechanism with periodic traffic indications</i> , where the MOB-SLP-REQ/RSP messages are omitted, and a traffic indication (TRF-IND) message is <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">periodically</i> sent at the beginning of every constant TRF-IND interval. The merits of the proposed scheme are simple implementation, reduction of energy consumption, and saving of the resource compared with the sleep mode in the IEEE 802.16e standard. The proposed scheme in this paper is well aligned with the design policy of sleep mode in discussion at IEEE 802.16m in the sense that it tries to minimize the state transition overhead between the awake and sleep modes, and hence, it can reduce the delay for state transition and enhance the power-saving efficiency. We investigate the performance of the proposed scheme in two ways: simulation and analytical methods. Using the performance evaluation, we find the optimal TRF-IND interval, which minimizes the average power consumption of the MS while satisfying the quality of service (QoS) on the mean delay. Numerical results show that the proposed scheme has 20%-50% reduction of the energy compared with the power-saving class (PSC) of type I, which is one of three operations for sleep mode in IEEE 802.16e.

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.