11 power-saving mode for mobile computing in Wi-Fi hotspots : Limitations , enhancements and open issues

Nowadays Wi-Fi is the most mature technology for wireless-Internet access. Despite the large (and ever increasing) diffusion of Wi-Fi hotspots, energy limitations of mobile devices are still an issue. To deal with this, the standard 802.11 includes a Power-Saving Mode (PSM), but not much attention has been devoted by the research community to understand its performance in depth. We think that this paper contributes to fill the gap. We focus on a typical WiFi hotspot scenario, and assess the dependence of the PSM behavior on several key parameters such as the packet loss probability, the Round Trip Time, the number of users within the hotspot. We show that during traffic bursts PSM is able to save up to 90% of the energy spent when no energy management is used, and introduces a limited additional delay. Unfortunately, in the case of long inactivity periods between bursts, PSM is not the optimal solution for energy management. We thus propose a very simple Cross-Layer Energy This work has been carried out while A. Passarella was with the Department of Information Engineering of the University of Pisa. G. Anastasi Pervasive Computing & Networking Laboratory (PerLab), Department of Information Engineering, University of Pisa, Via Diotisalvi 2 56122 Pisa, Italy e-mail: g.anastasi@iet.unipi.it M. Conti · E. Gregori · A. Passarella ( ) Pervasive Computing & Networking Laboratory (PerLab), CNR IIT Institute, Via G. Moruzzi, 1 56124 Pisa, Italy e-mail: andrea.passarella@iit.cnr.it M. Conti e-mail: marco.conti@iit.cnr.it E. Gregori e-mail: enrico.gregori@iit.cnr.it Manager (XEM) that dynamically tunes its energy-saving strategy depending on the application behavior and key network parameters. XEM does not require any modification to the applications or to the 802.11 standard, and can thus be easily integrated in current Wi-Fi devices. Depending on the network traffic pattern, XEM reduces the energy consumption of an additional 20–96% with respect to the standard PSM.

[1]  W. Richard Stevens,et al.  TCP/IP Illustrated, Volume 1: The Protocols , 1994 .

[2]  H. Balakrishnan,et al.  A comparison of mechanisms for improving TCP performance over wireless links , 1999, SIGCOMM '96.

[3]  Darrell D. E. Long,et al.  A dynamic disk spin-down technique for mobile computing , 1996, MobiCom '96.

[4]  Azer Bestavros,et al.  Self-similarity in World Wide Web traffic: evidence and possible causes , 1996, SIGMETRICS '96.

[5]  Randy H. Katz,et al.  Measuring and Reducing Energy Consumption of Network Interfaces in Hand-Held Devices (Special Issue on Mobile Computing) , 1997 .

[6]  Donald F. Towsley,et al.  Modeling TCP throughput: a simple model and its empirical validation , 1998, SIGCOMM '98.

[7]  Paul Barford,et al.  Generating representative Web workloads for network and server performance evaluation , 1998, SIGMETRICS '98/PERFORMANCE '98.

[8]  F. Cail,et al.  IEEE 802.11 wireless LAN : Capacity analysis and protocol enhancement , 1998, INFOCOM 1998.

[9]  Martin Arlitt,et al.  Workload Characterization of the 1998 World Cup Web Site , 1999 .

[10]  Luca Benini,et al.  Dynamic power management for nonstationary service requests , 1999, Design, Automation and Test in Europe Conference and Exhibition, 1999. Proceedings (Cat. No. PR00078).

[11]  Luca Benini,et al.  Dynamic power management for portable systems , 2000, MobiCom '00.

[12]  Adam Wolisz,et al.  An energy-efficient power control approach for WLANs , 2000, Journal of Communications and Networks.

[13]  Robin Kravets,et al.  Application‐driven power management for mobile communication , 2000, Wirel. Networks.

[14]  Luca Benini,et al.  Event-driven power management , 2001, IEEE Trans. Comput. Aided Des. Integr. Circuits Syst..

[15]  Martin Nilsson,et al.  Investigating the energy consumption of a wireless network interface in an ad hoc networking environment , 2001, Proceedings IEEE INFOCOM 2001. Conference on Computer Communications. Twentieth Annual Joint Conference of the IEEE Computer and Communications Society (Cat. No.01CH37213).

[16]  Marco Conti,et al.  A simple protocol for the dynamic tuning of the backoff mechanism in IEEE 802.11 networks , 2001, Comput. Networks.

[17]  Kevin Jeffay,et al.  What TCP/IP protocol headers can tell us about the web , 2001, SIGMETRICS '01.

[18]  B. R. Badrinath,et al.  Web&: an architecture for non-interactive Web , 2001, Proceedings. The Second IEEE Workshop on Internet Applications. WIAPP 2001.

[19]  Mahadev Satyanarayanan,et al.  Balancing performance, energy, and quality in pervasive computing , 2002, Proceedings 22nd International Conference on Distributed Computing Systems.

[20]  Luca Benini,et al.  Power-aware operating systems for interactive systems , 2002, IEEE Trans. Very Large Scale Integr. Syst..

[21]  Giuseppe Anastasi,et al.  Performance comparison of power-saving strategies for mobile Web access , 2003, Perform. Evaluation.

[22]  Sujit Dey,et al.  Energy-Efficient Link Adaptations in IEEE 802.11b Wireless LAN , 2003 .

[23]  Mani B. Srivastava,et al.  Power management for energy-aware communication systems , 2003, TECS.

[24]  Giuseppe Anastasi,et al.  A Power-Saving Network Architecture for Accessing the Internet from Mobile Computers: Design, Implementation and Measurements , 2003, Comput. J..

[25]  Srinivasan Seshan,et al.  Choosing beacon periods to improve response times for wireless HTTP clients , 2004, MobiWac '04.

[26]  Carla-Fabiana Chiasserini,et al.  An energy-efficient MAC layer scheme for 802.11-based WLANs , 2004, IEEE International Conference on Performance, Computing, and Communications, 2004.

[27]  Giuseppe Anastasi,et al.  A performance study of power-saving polices for Wi-Fi hotspots , 2004, Comput. Networks.

[28]  Marco Conti,et al.  Throughput Evaluation and Enhancement of TCP Clients in Wi-Fi Hot Spots , 2004, WONS.

[29]  Giuseppe Anastasi,et al.  Experimental analysis of an application-independent energy management policy for Wi-Fi hotspots , 2004, Proceedings. ISCC 2004. Ninth International Symposium on Computers And Communications (IEEE Cat. No.04TH8769).

[30]  Marco Conti,et al.  Cross-layering in mobile ad hoc network design , 2004, Computer.

[31]  Kang G. Shin,et al.  Smart power-saving mode for IEEE 802.11 wireless LANs , 2005, Proceedings IEEE 24th Annual Joint Conference of the IEEE Computer and Communications Societies..

[32]  Hari Balakrishnan,et al.  Minimizing Energy for Wireless Web Access with Bounded Slowdown , 2005, Wirel. Networks.

[33]  Jason Flinn,et al.  Self-Tuning Wireless Network Power Management , 2005, Wirel. Networks.

[34]  Nitin H. Vaidya,et al.  Design and implementation of a multi-channel multi-interface network , 2006, REALMAN '06.

[35]  Jesse James Garrett.  Ajax: A New Approach to Web Applications , 2007 .