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

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

3. 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 Systems and Their Use in Kinematic State Estimation” white paper written (by Richard Roy) and distributed ( 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 p 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 p compliant radio receivers?  
Invited chipset / semiconductor manufacturers ( & phone follow-up)
Atheros, Conexant, Intel, Motorola and Texas Instruments.
No responses prior to this meeting.

4. 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.

5. 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.

6. 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

7. 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 +

8. 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.”

9. 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

10. * 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).

11. July 2005
Desired Feedback from 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)

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

13. 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