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Data Rate is Signal Quality

Data Rate is Signal Quality. Presenter: Roger Durand. Outline. Need for a quality index Applications for a quality index Problems in finding a quality index Solution use data rate Concerns- Strength and Wisdom Motion. Need For a Quality Index. Power measurements is a start (RCPI, RPI)

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Data Rate is Signal Quality

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  1. Data Rate is Signal Quality Presenter: Roger Durand Roger Durand, Propagate Networks

  2. Outline • Need for a quality index • Applications for a quality index • Problems in finding a quality index • Solution use data rate • Concerns- Strength and Wisdom • Motion Roger Durand, Propagate Networks

  3. Need For a Quality Index • Power measurements is a start (RCPI, RPI) • By itself it does not: • Represent a useable link capacity or settable data rate with confidence • Missing: • Path Degradations • Radio Self Generated Noise, Radio Errors • Enhanced Equalization Techniques • Transmission Collisions Roger Durand, Propagate Networks

  4. Applications For a Quality Index • A means to better determine the need to initiate a possible roaming event • A means to infer: • Excess Interference • High multipath environment/channel • “Excessive” collisions • Poor or broken radio performance Roger Durand, Propagate Networks

  5. Problems in Finding a Quality Index • PSNI • Easier said then done in WLAN • Needs a training packet for consistency or lots of data • Collisions, Dynamic Interference and Errors issues • EVM • Implementation specific variables • Enhanced equalizers, loops, path assumptions • If acquisition-demodulation loops lose lock, then- EVM results lie if not filtered. Reasons- Low SNR, Path degradations, Collisions, Other Interference • The basic intention of both PSNI&EVM is valid. Roger Durand, Propagate Networks

  6. Solution use Data Rate • Data rate takes all parameters and other variables into account for that receive path • Data rate can be used to infer a rough SNR after all the degradations- • 54M~ 22-25 db... 36M~16-19dB...24M~12-16db...12M~6-9dB...6M~4-6dB • All modern APs have individual client tables with data rate lookups for transmission • Simple addition with little or no impact to existing products Roger Durand, Propagate Networks

  7. Concerns • The actual Data Rate selected, • Is dependent on actual implementation method • They all take time to settle • So many missed packets reduce the rate • So many accepted packets increase the rate • Variability of fast versus slow data rate methods • Aggressive- faster to respond to changes , more actual errors, wide rate swings • Passive- slower to respond to changes, less actual errors, less rate swings • The actual rate selection method, so far, has been considered beyond the scope of the standard Roger Durand, Propagate Networks

  8. Data Rate from 11g • From 11g 10.4.4.2 & 19.8.1- • Reference to data_rate/500k • EX:1M =002, 2M=004, 5.5M=011... • 54M=108 Dec = 6C Hex • Modulation code type: 0=default, 1=PBCC, 2=DSSS-OFDM • Lets take and use these to start Roger Durand, Propagate Networks

  9. Receiver might “pull” the rate • We need to enable the future • At this point we do not define how this is measured or done • The receiver if capable might tell the transmitter how “well” it is receiving the signal • 1 bit to say if it is capable • 2 hex (32) to call out a SNR “capacity” in 1 dB steps as referenced from present data rate. Roger Durand, Propagate Networks

  10. Discussion and Motions • Discussion • Motion- To endorse the value of using data rates as a means to discern signal quality. • Motion- To “empower” the editor to add the data rates as referenced from 802.11g and this presentation into 802.11k draft. • Motion- To “empower” the editor to add the receiver “pull” capability in this presentation into the 802.11k draft. Roger Durand, Propagate Networks

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