doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 1 RSNI: Simple SNIR for TGk Notice: This document has been prepared to assist IEEE 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 Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures, 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 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 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at SEP-21 Authors :

doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 2 Introduction At very inception of TGk, the need for a signal quality metric was identified. Measuring the “goodness” of a STAs communication link with its serving AP and measuring the “goodness” of the links to neighbor APs is crucial to effective roaming. Erred packet counts at MAC level do not suffice: most links adapt to operate with minimal or no errors so scaled measurement is not possible. “no errors” or “few errors” is insufficient. Time delay to get true picture of link quality is too long to be useful; 100’s or 1000’s of errors needed for meaningful measure. No information is available if “no errors” detected. TGk needs a fast signal quality metric. PSNI attempted to define a fast metric to quantify quality of link output data stream. Considered too complex. A new metric is proposed here as a simple metric to quantify input RF signal quality at a receiving STA.

doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 3 Receive Signal to Noise Indicator (RSNI) SIMPLE, based on what we already have: RCPI and Noise Histogram RCPI measures RF signal (plus noise & interference) at antenna connector. Noise Histogram measures noise & interference at antenna connector RSNI is simple ratio derived from these two existing measurements. Need to define new “average” noise plus interference metric (ANPI) as intermediate product. Suggest that we attach new ANPI to Noise Histogram Report. ANPI may be derived as a summary metric from the Noise Histogram by calculating a weighted average of the histogram bin power levels. Define RSNI at MAC layer: Add new RSNI to: Beacon Report Frame Report (Re)Association Response (RCPI - ANPI) ANPI

doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 4 RCPI measures total RF Power at antenna input connector A. PSNI measures observed S/(N+I) within demodulator but normalizes measurement for FER at E. RSNI measures RF S/(N+I) at antenna input connector A. PHY Measurement Architecture Radio front end A/D FEC Decoder (optional) Demodulator and tracking loops (PHY specific) A: Total RF power, RF (S+N+I) from each AP RF (N+I) in the channel DC B A B: BB S/(N+I) from each AP (BB power constant by AGC) C&D: Bit Error Rate data rate from each AP Frame Check (CRC) E E: Frame Error Rate data rate from each AP AGC

doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 5 Measure PHY Demod Input (power) and Output (QOS) Accurate S/(N+I) measurement at A is interesting but because RF/demod implementations vary widely, it cannot be used comparatively between STAs to evaluate delivered signal quality. Accurate FER measurement at E is ideal quality measure, but cannot be measured frame by frame. FER can only be accurately measured over 100s-1000s of frames. Also, FERs are comparable only at same frame size and data rate. Measure RCPI power at A. RSNI derived from Measure Noise power at A. measurements at A. Good STA Med STA Marginal STA A (dBm) E (FER) -80dbm 10E-2 10E-4 10E-5 Good STA Med STA Marginal STA A (dBm)E (FER) 10E-5 Signal at same objective SNR Signal at same subjective SNR -80dbm -78dbm -75dbm

doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 6 RCPI and PSNI Relation to SNR in Demodulator Received Channel Power Level dBm (S + N + I) Operating Margin Required Min RSPL Level Desired Signal Power dBm Interference Power at Input Boltzman’s C (-198dBm/Hz/K) Antenna Connector: Input Power Level (S+ N + I) Input RF SNIR Ratio (RSNI at antenna conn) Thermal Input Noise Level (-100 dBm) Theoretical SNR for required BER (RCPI at antenna connector) NBW = 22MHz = 73.4dB Temp = 290K = 24.6dB Channel Impairments (CI) ) (fading + multipath + etc, = 0 in AWGN) dBm Total Modem Implementation Losses (TML) FEC Decoder Loss, if any Demodulator Loss Rx Amp Noise Figure + IM Distortion dBm Observed Digital SNIR Ratio (PSNI in demodulator ) Input RF SNR Ratio Total Channel Condition Losses Observed Analog SNIR Ratio o (ANPI at antenna connector)

doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 7 DRAFT Normative Text Changes "Average Noise Power Indicator (ANPI) value represents the average noise plus interference power on the measured channel at the antenna connector during the measurement duration when NAV is equal to 0 (when virtual CS mechanism indicates idle channel). ANPI power is defined in dbm using the same units as defined for RCPI. ANPI may be calculated by a weighted average for the reported RPI densities assuming noise power to be the mid range value for each of the nine defined ranges for the RPI levels defined in Table k14. Other measurement techniques are allowed.” " The RSNI field contains the RSNI value for the received frame as measured by the reporting STA at the currently in use receiving antenna connector. RSNI is the received signal to noise plus interference ratio derived from the measured RCPI for the received frame and from the most recent ANPI value measured on the channel used to received the frame. RSNI may be calculated by the ratio of the received signal power (RCPI - ANPI) over the noise plus interference power (ANPI), expressed in db (1/2 db steps), where RSNI = [(ratio(dB) + 10) * 2], for ratios in the range -10dB to +118dB. Other measurement techniques are allowed."

doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 8 Conclusions This SIMPLE new approach which defines RSNI plugs the TGk hole for fast signal quality metric. RSNI builds upon existing facilities to accomplish this goal in the MAC layer. Straw poll at last meeting indicated strong support for this proposal. (16 for, 5 against) Normative text has been developed for consideration 05/0941r0. VOTE FOR NORMATIVE TEXT

doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 9 Motion for Improved Normative Text Move to instruct the editor to incorporate text from document k-NormText_RSNI.doc into next TGk draft specification document. Moved by Joe Kwak Seconded by: _______________ Vote YEA _______ Vote NEA _______ ABSTAIN _______ Vote Passes/Fails at ___%

doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 10 ANNEX A The following charts are excerpts of prior work which attempted to define a SNIR metric for TGk. PSNI was proposed as an SNIR-based metric which measured the quality (PER & BER) of an link. Excerpts which follow are from 03/898r2 and 04/0109r1.

doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 11 RCPI measures total RF Power at antenna input connector A. PSNI measures observed S/(N+I) within demodulator but normalizes measurement for FER at E. PHY Measurement Architecture Radio front end A/D FEC Decoder (optional) Demodulator and tracking loops (PHY specific) A: Total RF power, RF S/(N+I) from each AP DC B A B: BB S/(N+I) from each AP (BB power constant by AGC) C&D: Bit Error Rate data rate from each AP Frame Check (CRC) E E: Frame Error Rate data rate from each AP AGC

doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 12 Measure PHY Demod Input (power) and Output (QOS) Accurate S/(N+I) measurement at A is interesting but because RF/demod implementations vary widely, it cannot be used comparatively between STAs to evaluate delivered signal quality. Accurate FER measurement at E is ideal quality measure, but cannot be measured frame by frame. FER can only be accurately measured over 100s-1000s of frames. Also, FERs are comparable only at same frame size and data rate. Measure RCPI power at A. Measure PSNI quality in middle, but specify PSNI with FER at E. Good STA Med STA Marginal STA A (dBm) E (FER) -80dbm 10E-2 10E-4 10E-5 Good STA Med STA Marginal STA A (dBm)E (FER) 10E-5 Signal at same objective SNR Signal at same subjective SNR -80dbm -78dbm -75dbm

doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 13 RCPI and PSNI Relation to SNR in Demodulator Received Channel Power Level dBm (S + N + I) Operating Margin Required Min RSPL Level Desired Signal Power dBm Interference Power at Input Boltzman’s C (-198dBm/Hz/K) Antenna Connector: Input Power Level (S+ N + I) Input Analog SNIR Ratio Thermal Input Noise Level (-100dBm) Theoretical SNR for required BER (RCPI at antenna connector) NBW = 22MHz = 73.4dB Temp = 290K = 24.6dB Channel Impairments (CI) ) (fading + multipath + etc, = 0 in AWGN) dBm Total Modem Implementation Losses (TML) FEC Decoder Loss, if any Demodulator Loss Rx Amp Noise Figure + IM Distortion dBm Observed Digital SNIR Ratio (PSNI in demodulator ) Input SNR Ratio Total Channel Condition Losses Observed Analog SNIR Ratio o

doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 14 PSNI is Specified for “Black Box” Sig LevelNoiseChan Fade Adjust sig, noise, fading for desired BER or Throughput for selected rate PSNI STA RCVR (at selected rate) BER or throughput SET INPUTS READ OUTPUT RCVR implementation may use: -EVM on data symbols -EVM on pilots -other FEC decoder metrics -FEC corrected bit rate -spreading code correlation quality -many others possible

doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 15 PSNI Concept: Measure Output Signal Quality Specified like RSSI: 8-bit unsigned value, monotonically increasing with increasing S/(N+I). PSNI shall be logarithmically scaled to perceived S/(N+I) which relates directly to FER performance. PSNI output values reflect output FER and are specified in AWGN and in one representative fading channel. Specify tabular performance using single PSNI output value for each data rate. Make PSNI performance optional. Specify accuracy of PSNI in AWGN to be +/- 2.0dB in AWGN and +/- 6.0dB in fading channels with 20 packets/sample. PSNI range shall span the lower 43 dB portion of the operating range of S/(N+I) to cover high FERs at data rates from 1 to 54 Mbps.

doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 16 PSNI specified on BER/FER curves

doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 17 PSNI Normative Specification Text The PSNI is a measure of the perceived, post-processing signal-to-noise-plus-interference (S/(N+I)) ratio in the demodulator. The allowed values for the Perceived Signal to Noise Indicator (PSNI) parameter shall be an 8 bit value in the range from 0 through 255. This parameter shall be a measure by the PHY sublayer of the perceived signal link quality observed after RF downconversion, demodulation, and FEC decoding and is derived from internal digital signal processing metrics of the demodulator, e.g. Error Vector Magnitude (EVM). PSNI shall be measured over the PLCP preamble and over the entire received frame. PSNI is intended to be used in a relative manner, and it shall be a monotonically increasing, logarithmic function of the observed link S/(N+I). Specified PSNI performance shall be measured over no less than 20 PPDUs from the same transmitter. PSNI accuracy and range shall be specified in AWGN and fading at given FERs for each data rate as indicated in Table XX. The fading channel model shall be the IEEE exponential ray decay model with 50nsec decay time. Theoretical FEC coding gain assumed in FER calculations: R = 1/2, 5.4dB gain R = 2/3, 4.7dB gain R = 3/4, 4.4dB gain PSNI SPECIAL VALUE: “0” shall indicate inability to measure PSNI When PSNI exceeds high end of measurable range for a given data rate, maximum PSNI for that rate shall be reported.

doc: IEEE /0779r1September 2005 Submission Joe Kwak, InterDigital 18 PSNI Normative Specification Text (cont) Since the PHY layer measures PSNI on a packet-by-packet basis, the statistics processing and variance adjustment will be done in the MAC layer. Additional Specification Text: The MAC layer will process statistics for PSNI measured on multiple packets from the same transmitter. The MAC will collect packet PSNI measurements, received from the PHY layer from the same transmitter, into a measurement set called a PSNI sample. The MAC will calculate the mean and standard deviation for the PSNI sample. The MAC will use the mean and standard deviation of the PSNI sample to calculate a PSNI fading correction. The MAC will add the fading correction to the mean of the PSNI sample to produce the PSNI Value to be reported for the PSNI sample. The calculation of the PSNI fading correction is designed to decrease the mean of the PSNI sample to produce a reported PSNI value which indicates output BER/FER using AWGN demodulation/decoder curves, where SNR = (PSNI / 6) - 9dB. PSNI Sample Statistics Adjust for Fading Reported Results PSNI 3 PSNI 5 PSNI 4 PSNI 2 PSNI 1 PSNI Mean PSNI StdDev Calc Fade Correction + - PSNI Value Sample Variance Sample Size