Transmit Power Requirements May 2005 doc.: IEEE 802.11-yy/xxxxr0 May 2005 Transmit Power Requirements Date: 2005-05-19 Authors: Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures <http:// ieee802.org/guides/bylaws/sb-bylaws.pdf>, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair <stuart.kerry@philips.com> as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at <patcom@ieee.org>. Joe Epstein, Meru Networks Joe Epstein, Meru Networks

May 2005 doc.: IEEE 802.11-yy/xxxxr0 May 2005 Abstract Reviews use of Transmit Power Control (TPC) to increase wireless network capacity. Suggests that we evaluate existing mechanisms Joe Epstein, Meru Networks Joe Epstein, Meru Networks

Contents Background The problem Common Uses May 2005 Contents Background The problem Common Uses How This Affects What We Do A Few More Considerations Suggestions Joe Epstein, Meru Networks

Background What is Transmit Power Control? Mechanisms May 2005 Background What is Transmit Power Control? Ability to require that a STA constrain transmit power to within some bounds Mechanisms Defined in 802.11h, and extended by 802.11k BSS-wide constraints provided by occasional advertisements, with STA having its own control within constraints 802.11h was motivated originally for regulatory compliance. Of course, 802.11h does acknowledge other uses Joe Epstein, Meru Networks

Background (2) Why do TPC? May 2005 Background (2) Why do TPC? Smaller cells leads to greater capacity: spatial reuse. Joe Epstein, Meru Networks

Background (3) Why control the stations’ power levels? May 2005 Background (3) Why control the stations’ power levels? Asymmetric or non-uniform cell sizes do not work well with CSMA/CA AP STA AP Client thinks it can speak to AP; AP can not successfully respond STA 2 STA 1 Station 1 is hidden from Station 2 Creates more hidden stations, which is bad given the handshaking nature of the protocol Thus, both sides need to agree Joe Epstein, Meru Networks

Considerations Diminishing to negative returns on cell shrinkage May 2005 Considerations Diminishing to negative returns on cell shrinkage Increased protocol overhead (handovers and such) Lower transmit powers increases dominance of variable channel affects Attenuation by the user’s body The orientation of the station Multipath Higher power burst transmissions or interference Different clients have different accuracies and precisions for power settings This certainly varies over different antenna configurations This may vary over different PHYs Transitions from high-power to low-power coverage areas are difficult Again, causes lack of uniform cell sizes, increasing collisions Joe Epstein, Meru Networks

Recommendation We may already be far along We should consider sensitivity mechanisms as well (other presentations) May get us involved in discussion on what sensitivity truly means: carrier sense definitions Let’s keep on thinking about the existing and in-progress mechanisms Let’s ensure that it’s possible to make things work well in a heterogeneous client environment This may involve making sure that accuracies are given correctly and that the behaviors are somewhat predictable Let’s ask whether we should think about transitions in coverage across cells of different power levels Joe Epstein, Meru Networks