Power saving with p-persistent sleep decision for wireless communications

In wireless and mobile communications systems, battery power is an essential and limited resource of portable devices. Sleep mode operation is widely used to save battery power. However, by using the sleep mode, the delay in packet transmission increases. In this paper, we propose an adaptive scheme, called the p-persistent sleep decision (SD), which controls the tradeoff between the power saving and the delay performance. The proposed p-persistent SD scheme can be used for the systems adopting frame structure with fixed length. At each beginning of frame, a node decides its state (i.e., sleep or active) for the frame, according to the result of p-persistent test, considering a variety of sleep-decision parameters, for examples, the number of queued packets and the channel condition. The performance of the p-persistent SD is evaluated by using Markov analysis. Numerical results show that we can easily control the tradeoff between the power saving and the delay performance by assigning different weights to the sleep-decision parameters. As an application example, we suggest the p-persistent SD applied to IEEE 802.11 MAC and compare its performance with that of the conventional IEEE 802.11 power save mode by using simulation. The simulation results show that the proposed scheme saves more energy under the given delay constraint. Since the proposed scheme is simple and practical, it can be applied to any star- and mesh-topology wireless networks with fixed frame length.     

Energy‐efficient network selection with mobility pattern awareness in an integrated WiMAX and WiFi network

To provide wireless Internet access, WiFi networks have been deployed in many regions such as buildings and campuses. However, WiFi networks are still insufficient to support ubiquitous wireless service due to their narrow coverage. One possibility to resolve this deficiency is to integrate WiFi networks with the wide‐range WiMAX networks. Under such an integrated WiMAX and WiFi network, how to conduct energy‐efficient handovers is a critical issue. In this paper, we propose a handover scheme with geographic mobility awareness (HGMA), which considers the historical handover patterns of mobile devices. HGMA can conserve the energy of handovering devices from three aspects. First, it prevents mobile devices from triggering unnecessary handovers according to their received signal strength and moving speeds. Second, it contains a handover candidate selection method for mobile devices to intelligently select a subset of WiFi access points or WiMAX relay stations to be scanned. Therefore, mobile devices can reduce their network scanning and thus save their energy. Third, HGMA prefers mobile devices staying in their original WiMAX or WiFi networks. This can prevent mobile devices from consuming too much energy on interface switching. In addition, HGMA prefers the low‐tier WiFi network over the WiMAX network and guarantees the bandwidth requirements of handovering devices. Simulation results show that HGMA can save about 59– 80% of energy consumption of a handover operation, make mobile devices to associate with WiFi networks with 16–62% more probabilities, and increase about 20–61% of QoS satisfaction ratio to handovering devices. Copyright © 2009 John Wiley & Sons, Ltd.     

支持WiMAX节点灵活休眠的两阶段可靠多播策略

节能是无线网络的一个重要课题.针对IEEE 802.16e标准第2类节能模型中监听窗口长度固定会导致一些空闲移动站因得不到及时休眠而浪费能量这一不足,该文提出"两阶段可靠多播策略",让基站在第1阶段多播数据包,在第2阶段对第1阶段丢失的数据包进行网络编码并重播.该策略让移动站一旦空闲就进入休眠,实现了时延约束下数据包的可靠传递.仿真试验表明,该策略可以降低能耗,且移动站的占空比、能耗、吞吐率、丢包率等指标均优于传统的重传与确认方案.     

Delay-bounded packet scheduling of bursty traffic over wireless channels

In this paper, we study minimal power transmission of bursty sources over wireless channels with constraints on mean queuing delay. The power minimizing schedulers adapt power and rate of transmission based on the queue and channel state. We show that packet scheduling based on queue state can be used to trade queuing delay with transmission power, even on additive white Gaussian noise (AWGN) channels. Our extensive simulations show that small increases in average delay can lead to substantial savings in transmission power, thereby providing another avenue for mobile devices to save on battery power. We propose a low-complexity scheduler that has near-optimal performance. We also construct a variable-rate quadrature amplitude modulation (QAM)-based transmission scheme to show the benefits of the proposed formulation in a practical communication system. Power optimal schedulers with absolute packet delay constraints are also studied and their performance is evaluated via simulations.     

Seamless IP mobility support for flat architecture mobile WiMAX networks - [WiMAX update]

The growing demand for wireless Internet services is accelerating the evolution of wireless networks toward all-IP architecture, and the mobile WiMAX network is a prominent example. Although currently deployed mobile WiMAX networks use hierarchical architecture, flat architecture is feasible and specified as a design alternative in the mobile WiMAX standard. In flat architecture the functionalities of the ASN-GW and BS are consolidated into a single element. In this article we first discuss the benefits and challenges of flat architecture mobile WiMAX networks. We then present a scheme to deal with the seamless mobility issue, which is one of the key challenges of the flat architecture. The proposed scheme combines two standard IP-mobility protocols, Proxy Mobile IP and Fast Mobile IP, and customizes them for IEEE 802.16e-based mobile WiMAX networks. This provides interoperability with existing mobile WiMAX networks. We demonstrate the viability of the proposed scheme through simulations using NS-2.     

Joint source coding and data rate adaptation for energy efficient wireless video streaming

Rapid growth in wireless networks is fueling demand for video services from mobile users. While the problem of transmitting video over unreliable channels has received some attention, the wireless network environment poses challenges such as transmission power management that have received little attention previously in connection with video. Transmission power management affects battery life in mobile devices, interference to other users, and network capacity. We consider energy efficient transmission of a video sequence under delay and quality constraints. The selection of source coding parameters is considered jointly with transmitter power and rate adaptation, and packet transmission scheduling. The goal is to transmit a video frame using the minimal required transmission energy under delay and quality constraints. Experimental results are presented that illustrate the advantages of the proposed approach.     

DRX mechanism for power saving in lte - [topics in radio communications]

Enhanced discontinuous reception mode is supported in long term evolution of 3GPP standards to conserve the mobile terminal?s battery power. Furthermore, there are additional advantages in using DRX, such as over-the-air resource saving on both the uplink and downlink to increase overall system capacity. One of the enhancements over 3G wireless systems is that in LTE DRX mode can be enabled even when the user equipment is registered with the evolved node-B. However, there is a need to optimize the DRX parameters, so as to maximize power saving without incurring network re-entry and packet delay. In particular, care should be exercised for real-time services. In this article the power saving methods in both network attached and network idle modes as outlined in LTE are explained. The optimum criteria to select the DRX mode are defined for different applications. Analytical/simulation results are presented to show the power saving/connection reestablishment and packet delay.     

EPON和WiMAX融合架构下带宽分配和调度机制的研究

以太网无源光网络(EPON)和IEEE 802.16(WiMAX)的融合网络在固定移动混合接入网中被认为是很有前景的接入方式.文中提出了3种WiMAX无线网络与EPON网络系统融合架构,融合系统同时具有光网络的高带宽和无线网络的灵活性.为了在接入网中支持QoS,本文为融合结构提出了一种动态带宽分配算法(DBA)和调度机...     

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.     

WiMAX应用潜力分析

文章分析了WiMAX在固定宽带无线接入场合和便携、移动通信场合的应用前景.文章认为:在固定宽带无线通信中,WiMAX会广泛应用于家庭用户、IP语音用户、传输承载用户和集团客户,为他们提供宽带无线接入;在便携、移动通信中,IEEE802.16即将集成到笔记本电脑和个人数字助理(PDA)等便携式电子设备中,实现在城域网范围内的可移动的宽带无线数据服务;用户需求加上WiMAX设备的批量上市及终端成本的下降,WiMAX的应用潜力巨大,市场将呈几何级增长.     

Improving the R-score of an adaptive VoIP codec in IEEE 802.16 networks

Worldwide Interoperability for Microwave Access (WiMAX) technology, which is based on the IEEE 802.16 standard, supports different quality of service (QoS) for different services. WiMAX is expected to support QoS in real-time applications such as Voice over Internet Protocol (VoIP). When network congestion occurs, the VoIP bit rate needs to be adjusted to achieve the best speech quality. In this study, we propose a new scheme called Adaptive VoIP Level Coding (AVLC). This scheme takes into consideration network conditions (packet delay and packet loss) and a connection’s modulation scheme. The amount of data that can be transmitted increases with the speed of the modulation scheme. When network congestion occurs, AVLC scheme prioritizes reducing the bit rate of a connection that has a slower modulation scheme to mitigate congestion. Depending on network conditions, such as modulation scheme, packet delay, packet loss, and residual time slot, we use the G.722.2 codec to adjust each connection’s bit rate. Simulations are conducted to test the performance (network delay, packet loss, number of modulation symbols, and R-score) of the proposed scheme. The simulation results indicate that speech quality is improved by the use of AVLC.     

An energy‐saving‐centric downlink scheduling scheme for WiMAX networks

This study proposes an energy‐saving‐centric downlink scheduling scheme to support efficient power utilization and to satisfy the QoS requirements. The base station considers the queue lengths of mobile stations with real‐time and non‐real‐time connections and considers their QoS requirements to determine the sleeping parameters when the mobile stations issue sleep requests. The proposed scheme appropriately reschedules the sleep‐requesting mobile station to transmit its queued packets for optimal power‐saving efficiency. The QoS requirement is considered as the constraint during traffic rescheduling. The treatment of real‐time connections generally requires a trade‐off of the delay requirement and the longer sleep window, and the non‐real‐time connections must concern the packet drop and minimum data rates when performing the energy‐centric scheduling. Two rescheduling algorithms, that is, whole and partial reschedules, are proposed and analyzed in this paper. The whole‐reschedule scheme provides improved energy‐saving performance at the cost of tolerable longer delay and computing complexity when compared with the partial‐reschedule scheme. Our simulation results indicated that both schemes not only guarantee the desired QoS but also achieve superior energy‐saving efficiency to that of traditional scheduling. Copyright © 2012 John Wiley & Sons, Ltd.     

An energy‐aware transmission mechanism for WiFi‐based mobile devices handling upload TCP traffic

This paper presents an energy‐aware transmission mechanism that improves the throughput and reduces the energy consumption of mobile devices in wired‐cum‐wireless TCP networks. The proposed mechanism places an agent at the base station, which identifies the cause of packet losses in the underlying network. When the mobile device acts as a TCP source, it adjusts the size of the congestion window adaptively according to the cause of packet losses with the aids of the agent in order to improve the transmission performance. In addition, the proposed mechanism lets the communication device to stay in sleep mode after completing the transmission in order to reduce the energy consumption. As a result, the cooperation between the mobile device and the agent improves the transmission performance as well as the energy efficiency greatly. To evaluate the performance of the proposed mechanism, we analyzed the effect of TCP on the communication device for mobile devices and present a power model. With extensive simulations based on the power model, we demonstrate that the proposed mechanism significantly improves the transmission performance, and reduces the energy consumption over a wide range of both wired and wireless packet losses. Copyright © 2008 John Wiley & Sons, Ltd.     

Performance analysis of power saving class of Type III in IEEE 802.16e with user initiated traffic

A novel method for analysing the performance of power saving class of Type III in IEEE 802.16e is proposed, which is applicable to design, maintenance and management for mobile wireless metropolitan area network. Considering the memoryless nature of user initiated packet arrival, a Geom/G/1 queue model with multiple vacations and setup period is built to capture the principle for the power saving class of Type III. By using an embedded Markov chain method and the boundary state variable theory, we obtain the queueing measures such as queueing length, waiting time and busy cycle in steady state. Correspondingly, we derive explicitly the performance measures for the power saving class of Type III in terms of handover ratio, energy saving ratio, and average packet response time. Based on numerical results, we develop a cost function to determine numerically the optimal length of sleep window and the minimal cost with different offered loads.     

A Network Selection Algorithm Based on Enhanced Access Router Discovery in Heterogeneous Wireless Networks

The management process between different wireless technologies for mobile devices is very important to complete the handover operations. The handover operation needs to determine the delay and packet loss in order to be the quality of service within a certain level. Selecting the best available network at the appropriate time is very significant in the direction of realizing ubiquitous networks. In this paper a network selection approach named enhanced access router discovery (EARD) is proposed. The approach is developed to work in a heterogeneous environment including of WiMAX and WLAN networks. The EARD method utilizes the prioritized rating for multiple criteria (PRMC) proposed for selecting the target network. The proposed approach is evaluated with respect to various conditions with different traffic types. The simulation results show that our proposed approach outperform the traditional network selection methods is selecting the most appropriate network.     

WiMAX跨层切换技术的研究与仿真

介绍了在移动WiMAX网络中引入IP层移动性管理协议FMIPv6来支持以全IP网络为核心网的语音、视频等多媒体实时业务,并将它与IEEE802.21工作组提出的草案MIH(Media Independent Handover)相结合,设计出一种跨层切换方案,并通过NS-2仿真工具对网络间的切换时延和丢包率进行仿真分析和比较,验证了方案的可用性和良好性能.     

Measurement and analysis of online gaming services on mobile WiMAX networks

Online games have been played mainly in desktop computers over wired networks because of high speed and intensive computation requirements. The advances in mobile devices and ever increasing wireless link bandwidth motivate us to study whether players can enjoy online gaming over broadband wireless networks such as mobile Worldwide Inter‐operability for Microwave Access (WiMAX). In this paper, we carry out comprehensive measurements of the World of Warcraft (WoW) over the mobile WiMAX in Seoul, Korea, and analyze the network performance focusing on two aspects: (1) network layer dynamics such as round trip time, jitter, and packet loss and (2) WiMAX link layer statistics such as the radio signal strength, handovers, and piggyback mechanism. From the empirical data, we set up performance models and evaluate the performance of WoW over WiMAX. We also discuss how to improve the service quality of online gaming over WiMAX.Copyright © 2013 John Wiley & Sons, Ltd.     

Opportunistic media access control and routing for delay-tolerant mobile ad hoc networks

In delay-tolerant mobile ad hoc networks, motion of network nodes, network sparsity and sporadic density can cause a lack of guaranteed connectivity. These networks experience significant link delay and their routing protocols must take a store-and-forward approach. In this paper, an opportunistic routing protocol is proposed, along with its compatible media access control, for non-real-time services in delay-tolerant networks. The scheme is mobility-aware such that each network node needs to know its own position and velocity. The media access control employs a four-fold handshake procedure to probe the wireless channel and cooperatively prioritize candidate nodes for packet replication. It exploits the broadcast characteristic of the wireless medium to utilize long-range but unreliable links. The routing process seizes opportunities of node contacts for data delivery. It takes a multiple-copy approach that is adaptive with node movements. Numerical results in mobile ad hoc networks and vehicular ad hoc networks show superior performance of the proposed protocol compared with other routing protocols. The mobility-aware media access control and routing scheme exhibits relatively small packet delivery delay and requires a modest amount of total packet replications/transmissions.     

D2D网络中基于立即可解网络编码的时延最小化重传方案

该文针对D2D无线网络中多终端并发协作重传冲突避免问题,提出一种基于立即可解网络编码的时延最小化重传方案。在重传阶段,充分利用D2D无线网络终端协作传输数据的优势,结合各终端数据包接收状态,综合考虑时延的影响因素,选取单次重传时延增量较小的数据包生成编码包,最小化重传时延。同时,构建终端冲突图,在图中搜索极大独立集,根据各终端的编码包权重值,选择最大加权独立集中的终端作为并发协作重传终端,从而降低重传次数。仿真结果表明,所提方案能够进一步改善D2D无线网络的重传效率。     

An efficient power management scheme with SDMA for IEEE 802.15.3 WPANs

IEEE 802.15.3 is devised for short‐distance wireless connectivity within a wireless personal area network (WPAN). In WPANs, a power management (PM) mechanism is used for power saving. The PM enables devices to sleep for one or more superframes in order to conserve power. Space division multiple access (SDMA) is a new technology to optimize performance of current and future mobile communication systems. In this paper, we propose an SDMA‐based PM scheme, called enhanced min‐degree searching (EMDS) for WPANs. EMDS orders the streams among multiple devices to minimize the total wake‐up times. In this scheme, every device that can transmit data at the same time is checked using the SDMA. The total wake‐up times will be reduced substantially if the majority of the devices can transmit data at the same time. Simulation results show that the performance of the proposed EMDS outperforms that of the existing approaches. Copyright © 2013 John Wiley & Sons, Ltd.