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11n Spectrum Mask Alignment

11n Spectrum Mask Alignment. Date: 2011-01-19. Authors:. Summary. 5 GHz Spectral mask floor in 11n is misaligned with that of 11a and 11ac 11n mask is -45 dBr, while 11a and 11ac mask is -40 dBr We propose to align the 11n mask specification with that of 11a and 11ac Only for 5 GHz band

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11n Spectrum Mask Alignment

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  1. 11n Spectrum Mask Alignment Date: 2011-01-19 Authors: Bijoy Bhukania, Broadcom

  2. Summary • 5 GHz Spectral mask floor in 11n is misaligned with that of 11a and 11ac • 11n mask is -45 dBr, while 11a and 11ac mask is -40 dBr • We propose to align the 11n mask specification with that of 11a and 11ac • Only for 5 GHz band • No spectral mask floor changes proposed for 2.4 GHz • Impact of this change is evaluated • Impact on transmit power • Impact of SINR of a adjacent receiver • Overall impact on network performance Bijoy Bhukania, Broadcom

  3. Mask Observations 11a, 11ac spec Existing 11n spec Bijoy Bhukania, Broadcom

  4. Issues with Different Specifications for 11n and 11ac • A 11ac device, when transmitting a 11n frame, has to comply with 11n specification • No reason to have different SM for 11n and 11ac • Existing 11a networks are working with -40 dBr mask • No real need to have 11n specification of -45 dBr, at least in 5 GHz band • A stricter mask limits the transmit power of lower MCS • SM limit is reached first. • Limits range Bijoy Bhukania, Broadcom

  5. Impact of SM on Transmit Power • The plots are based on 11a/n/ac Rapp model • The SM “slope” comes from nonlinearity, while the floor comes from noise • Transmit power of 11n devices is limited by the -45 dBr floor • -40 dBr spec would allow transmitter to transmit up to 4 dB higher power Bijoy Bhukania, Broadcom

  6. Impact on EVM • -18 dB EVM does not degrade PER performance of MCS0 • EVM of -18 dB is attained at 4 dB back-off from P1 dB point • But -45 dBr SM is violated, but -40 dBr is not Bijoy Bhukania, Broadcom

  7. Impact on SINR at an Alternate Adjacent Receiver • Additional degradation in SINR due to -40 dBr SM is 2.91 dB for worst-case AACI levels. • Not 5 dB as reported in Nov’2010 IEEE meeting • This is due to the noise level being accounted for Bijoy Bhukania, Broadcom

  8. Overall Benefits of -40 dBr Specification • Transmit power for lower MCS can be increased by up to 4 dB • Leads to increased range, bigger BSS, and reduced infrastructure cost • AACI level increase is not significant • SINR for worst-case AACI levels degrades by 2.91 dB (-50 dBm AACI power), while for the -70 dBm AACI power case AACI level degrades by marginal 0.07 dB. • “Range” in absence of AACI increases significantly Bijoy Bhukania, Broadcom

  9. Conclusion • TX spectral mask should be modified from -45 dBr to -40 dBr for several strong reasons: • Significant range enhancement in normal operating scenario • Important for 5 GHz band since no CCK rates are used • Whole home coverage • Marginally enhanced range in presence of AACI • Reduced infrastructure cost • Uniformity between 11a, 11n and 11ac specifications Bijoy Bhukania, Broadcom

  10. Straw Poll #1 • Only for 5 GHz band, do you support aligning the 11n spectral mask specifications with 11a and 11ac, which would require modifying the 11n mask level from -45 dBr to -40 dBr? • Yes: • No: • Abstain: Bijoy Bhukania, Broadcom

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