WRSS in 802.11p Date: 2005-07-20 July 2005 Month Year doc.: IEEE 802.11-05/0368r0 July 2005 WRSS in 802.11p Date: 2005-07-20 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>. Jeffrey Zhu, Mark IV industries

Agenda – WRSS in 802.11p July 2005 Progress since Cairns Month Year doc.: IEEE 802.11-05/0368r0 July 2005 Agenda – WRSS in 802.11p Progress since Cairns TGk / RCPI and TGp / WRSS Updated Definitions and Terms Current adhoc group consensus Responses / Direction Jeffrey Zhu, Mark IV industries

Progress Since Last Meeting in Cairns July 2005 Progress Since Last Meeting in Cairns Face-to-face meetings and multiple conference calls to address WRSS issues among concerned parties. “Issues Related to RF Signal Strength Measurements in IEEE 802.11 Systems and Their Use in Kinematic State Estimation” white paper written (by Richard Roy) and distributed (11-04-0597-00-wave … how it got this number is interesting?). Document discusses the statistical characteristics of the signal strength measurements being proposed. Two questions posed were: What RF signal strength measurement accuracies are required now and in the near future from original equipment manufacturers (OEMs) of otherwise IEEE 802.11p compliant radio receivers by designers of RF RSS-based location estimation applications? What RF signal strength measurement accuracies are achievable now and in the near future by original equipment manufacturers (OEMs) of otherwise IEEE 802.11p compliant radio receivers?   Invited 802.11 chipset / semiconductor manufacturers (email & phone follow-up) Atheros, Conexant, Intel, Motorola and Texas Instruments. No responses prior to this meeting.

TGk and RCPI July 2005 RCPI measurement latency Current TGk definition of RCPI “The RCPI indicator is a measure of the received RF power in the selected channel. This parameter shall be a measure by the PHY sublayer of the received RF power in the channel measured over the preamble and the entire received frame.” RCPI statistics RCPI measurement accuracy in TGk is assumed to be either: the second moment of the probability density function describing the statistics of the RCPI measurement over all operating conditions (input powers, temperature, etc.) by any radio. or maximum measurement error (3σ) in db made by any radio over all operating condition in product life. RCPI measurement accuracy (?) ± 5 dB and resolution < 0.5 dB across the entire range of input powers as currently proposed in TGk may not be acceptable for some WAVE applications, though there are currently no available documents containing technically sound justifications for more stringent specifications. RCPI measurement latency TGp should investigate MAC issues to ensure that RF signal strength measurements can meet latency requirements of WAVE applications (fast polling). Protocol induced latency associated with the RCPI measurement currently being proposed in TGk is believed to be unacceptable for some WAVE applications.

TGp and WRSS WRSS measurement definition WRSS measurement statistics July 2005 TGp and WRSS WRSS measurement definition Received RF power (in dBm) in the selected channel as measured at the antenna connector by the PHY sublayer. WRSS measurement statistics The concept of short-term (< ~ 1 sec) and long-term (> ~ secs) statistics (fast and slow respectively) should be included in TGk (and TGp if necessary). Test conditions for estimating statistics (means and variances) Repeated WRSS measurements are made over a single burst (preamble and entire frame) at a fixed operating condition. The operating conditions are then varied over the entire range with multiple measurements made at each set point. Current WRSS draft specifications WRSS measurement accuracy and resolution specifications of ± 3 dB and 0.2 dB, respectively, are in previous and current (D0.21) 11p drafts. Some believe these specifications have been neither justified by application developers, nor officially agreed to by chipset and/or OEM manufacturers.

Short-term (fast) Statistics July 2005 Short-term (fast) Statistics sfast bfast Ptrue Mean(ZRSS) Ptrue is the true value of the received power (RSS) Mean(ZRSS) is the mean value of the measured power (averaged over a large number of (consecutive) frames at a fixed operating point (eg. temperature, input power, AGC, etc.)) bfast is the bias in the short-term estimate of RSS at a fixed operating condition is the standard deviation of the measured power sfast

Long-term (slow) Statistics July 2005 Long-term (slow) Statistics sslow Mean(bfast) Bias (dB) Mean(bfast) is the mean of the bias in the measurement of RSS at a fixed operating point (temperature, input power, AGC, etc.), averaged over a large number of operating points within the operating region. is the standard deviation of the bias over all operating conditions (Mean(bfast))2 is the second moment of the bias over all operating conditions sslow sslow2 +

WRSS-related Properties from a Potential WAVE Application July 2005 WRSS-related Properties from a Potential WAVE Application WRSS used in threshold tests for initiating communications WRSS measurements made in line-of-sight conditions Very short distances (1-10 m) between transmitter and receiver Well-know communication zone (pre-calibrated) Interactions of short duration (< 1 sec) REMEMBER the definition of WRSS: “Received RF power (dBm) in the selected channel as measured at the antenna connector by the PHY sublayer.”

RSSI, RCPI & WRSS (Reference Only) July 2005 RSSI, RCPI & WRSS (Reference Only) Parameter RSSI (from TGk) RCPI WRSS Proposed Measurement object Preamble Preamble & Entire message Preamble & Entire Message Protocol Simple Complex Set-up time 2 ms Absolute accuracy*1 Not specified ± 5 db Absolute resolution*2 0.5 db Short term accuracy*3 ± 3 db Short term resolution*4 0.2 db Applicable signal OFDM, DSSS Applicable input range (-110 to 0 dbm) (-60 to -30 dbm) Bandwidth 10 MHz 11 MHz Measurement point Antenna Connector Antenna Connector * - Definitions

* Definitions for the RSSI, RCPI & WRSS Table July 2005 * Definitions for the RSSI, RCPI & WRSS Table Absolute accuracy: The maximum WRSS measurement error (?σ) in db made by any radio over all operating condition in product life. Absolute resolution: The minimum distinguishable WRSS measurement made by any radio over all operating condition in product life. Short term accuracy: The maximum WRSS measurement variation (?σ) in db made by a specific radio over any specific condition over short period of time (1 min). Short term resolution: The minimum distinguishable WRSS measurement made by a specific radio over any specific condition over short period of time (1 min).

July 2005 Desired Feedback from 802.11 Chipset Manufacturers and Radio Subsystem OEMs What values of WRSS_TOTAL, WRSS_FAST and WRSS_SLOW (in dB) do your current (and future) products achieve? Note: WRSS_FAST is tested under condition of entire temperature range and input power between -30 and -60 dB (Worst Case)

July 2005 Desired Feedback from 802.11 Chipset Manufacturers and Radio Subsystem OEMs Present 802.11p draft (D0.21) specifies ± 3 dB accuracy and 0.2 dB resolution. Will you support a proposed 802.11p amendment to the 802.11 standard with these specifications?

If Non-response from Chipset Manufacturers, Conduct Straw Poll in TGp July 2005 If Non-response from Chipset Manufacturers, Conduct Straw Poll in TGp Should TGp concern itself with “WRSS”? __ Yes __ No __ Abstain Should WRSS be mandated even if it has a considerable impact on product complexity? __ Yes __ No __ Abstain Should TGp request TGk to address MAC poll/response latency issues for WAVE applications? __ Yes __ No __ Abstain Should TGp address WRSS MAC poll/response effects and accept current accuracy/resolution values for absolute measurements from TGk? __ Yes __ No __ Abstain Should TGp request that TGk incorporate short- and long-term statistical parameters in defining accuracy and setting limits (as described herein)? __ Yes __ No __ Abstain Reconfirmation: Should TGp continue work on including WRSS (both MAC poll/response and accuracy/resolution)? __ Yes __ No __ Abstain Should TGp eliminate WRSS entirely? __ Yes __ No __ Abstain