Understanding the limitations of transmit power control for indoor wlans

A wide range of transmit power control (TPC) algorithms have been proposed in recent literature to reduce interference and increase capacity in 802.11 wireless networks. However, few of them have made it to practice. In many cases this gap is attributed to lack of suitable hardware support in wireless cards to implement these algorithms. In particular, many research efforts have indicated that wireless card vendors need to support power control mechanisms in a fine-grained manner - both in the number of possible power levels and the time granularity at which the controls can be applied. In this paper we claim that even if fine-grained power control mechanisms were to be made available by wireless card vendors, algorithms would not be able to properly leverage such degrees of control in typical indoor environments. We prove this claim through rigorous empirical analysis and then build a tunable empirical model (Model-TPC) that can determine the granularity of power control that is actually useful. To illustrate the importance of our solution, we conclude by demonstrating the impact of choice of power control granularity on Internet applications where wireless clients interact with servers on the Internet. We observe that the number of feasible power was found to be between 2-4 for most indoor environments. We believe that the results from this study can serve as the right set of assumptions to build practically realizable TPC algorithms in the future.

[1]  Kin K. Leung,et al.  Controlling QoS by Integrated Power Control and Link Adaptation in Broadband Wireless Networks , 2000, Eur. Trans. Telecommun..

[2]  Sundeep Rangan,et al.  Distributed Uplink Power Control for Optimal SIR Assignment in Cellular Data Networks , 2006, Proceedings IEEE INFOCOM 2006. 25TH IEEE International Conference on Computer Communications.

[3]  Zvi Rosberg,et al.  Asymptotically optimal transmission power and rate control for CDMA channels with multiple user classes , 2005, Proceedings IEEE 24th Annual Joint Conference of the IEEE Computer and Communications Societies..

[4]  Hari Balakrishnan,et al.  Divert: fine-grained path selection for wireless LANs , 2004, MobiSys '04.

[5]  Ratul Mahajan,et al.  Measurement-based models of delivery and interference in static wireless networks , 2006, SIGCOMM.

[6]  Prashant Krishnamurthy,et al.  Modeling of indoor positioning systems based on location fingerprinting , 2004, IEEE INFOCOM 2004.

[7]  Srinivasan Seshan,et al.  Self-management in chaotic wireless deployments , 2005, MobiCom '05.

[8]  Thomas M. Cover,et al.  Elements of Information Theory , 2005 .

[9]  Moustafa Youssef,et al.  The Horus WLAN location determination system , 2005, MobiSys '05.

[10]  D. W. Allan,et al.  Time and Frequency (Time-Domain) Characterization, Estimation, and Prediction of Precision Clocks and Oscillators , 1987, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[11]  Panganamala Ramana Kumar,et al.  RHEINISCH-WESTFÄLISCHE TECHNISCHE HOCHSCHULE AACHEN , 2001 .

[12]  Vaduvur Bharghavan,et al.  A power controlled multiple access protocol for wireless packet networks , 2001, Proceedings IEEE INFOCOM 2001. Conference on Computer Communications. Twentieth Annual Joint Conference of the IEEE Computer and Communications Society (Cat. No.01CH37213).

[13]  J. Lansford,et al.  The design and implementation of HomeRF: a radio frequency wireless networking standard for the connected home , 2000, Proceedings of the IEEE.

[14]  Hari Balakrishnan,et al.  Improving loss resilience with multi-radio diversity in wireless networks , 2005, MobiCom '05.

[15]  Seung-Jae Han,et al.  Cell Breathing Techniques for Load Balancing in Wireless LANs , 2006, IEEE Transactions on Mobile Computing.

[16]  Madhavi W. Subbarao.  Dynamic power-conscious routing for MANETs: an initial approach , 1999, Gateway to 21st Century Communications Village. VTC 1999-Fall. IEEE VTS 50th Vehicular Technology Conference (Cat. No.99CH36324).

[17]  Chi-Hsiang Yeh,et al.  IPMA: an interference/power-aware MAC scheme for heterogeneous wireless networks , 2003, Proceedings of the Eighth IEEE Symposium on Computers and Communications. ISCC 2003.

[18]  Serge Fdida,et al.  On the feasibility of power control in current IEEE 802.11 devices , 2006, Fourth Annual IEEE International Conference on Pervasive Computing and Communications Workshops (PERCOMW'06).

[19]  Richard Han,et al.  SHUSH: reactive transmit power control for wireless MAC protocols , 2005, First International Conference on Wireless Internet (WICON'05).

[20]  Robert Tappan Morris,et al.  ExOR: opportunistic multi-hop routing for wireless networks , 2005, SIGCOMM '05.