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PHY measurements for interference reduction from 11h

July 2003. doc: IEEE 802.11-03/537r0. PHY measurements for interference reduction from 11h. Joe Kwak, Marian Rudolf InterDigital. Outline. Introduction Transmit Power Control (TPC) in 802.11h D3.3.4 defines a link probe and Tx power limitation mechanisms Aspects / benefits of TPC

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PHY measurements for interference reduction from 11h

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  1. July 2003 doc: IEEE 802.11-03/537r0 PHY measurements for interference reduction from 11h Joe Kwak, Marian Rudolf InterDigital Joe Kwak, InterDigital

  2. Outline • Introduction • Transmit Power Control (TPC) in 802.11h D3.3.4 defines a link probe and Tx power limitation mechanisms • Aspects / benefits of TPC • Why should 802.11k consider TPC ? • Summary of proposal Joe Kwak, InterDigital

  3. Introduction • 2 main areas where WLAN Radio Resource Management algorithms can achieve very significant performance gains • In-band interference mitigation (= keeping Tx power levels at an optimum level) • Frequency reuse (= assigning channels in a clever way when multiple “cells” are deployed) • Interference mitigation needs PHY Tx power / link margin measurements and signaling mechanisms to request / retrieve or broadcast this information from / to STA’s • Such measurements and signaling mechanisms are already being standardized in 11h – our baseline proposal is to take over these features into 11k Joe Kwak, InterDigital

  4. 802.11h D3.3.4 Joe Kwak, InterDigital

  5. Motivation for TPC in 802.11h • Primary reason for Transmit Power Control (TPC) mechanism in 802.11a • TPC (max. regulatory Tx power settings) is a requirement for operation on the 5 GHz band in Europe • Secondary - extremely important - side effects • Baseline mechanism for interference reduction in 802.11 network in the more general sense • Basic tool for system adaptivity for any form of WLAN RRM Joe Kwak, InterDigital

  6. Overview on TPC in 802.11h D3.3.4 • 2 new action frames are defined (similar to MEASUREMENT REQUEST and MEASUREMENT REPORT), • TPC REQUEST and TPC RESPONSE • BEACON and PROBE RESPONSE frames extended by, • New Power Constraint and TPC Report IE’s • Modified Country IE (from 802.11d) • New MLME-TPCADAPT.request/.confirm primitives • TPC procedures are introduced (= “rule set”) • (RE-)ASSOCIATION REQUEST framesextended by, • New Power Capability IE Joe Kwak, InterDigital

  7. TPC REQUEST / RESPONSE frames STEP 1: AP sends TPC REQUEST action frame AP This is clearly a link measurement procedure! STEP 2: STA replies with TPC REPORT action frame (Does not contain any IE, works like a “Ping”) Contains 2 IE’s:- “Transmit Power” field- “Link margin” field STA “Transmit Power” (8 bits, signed integer, unit dBm) is equal to Tx power used to transmit the TPC REPORT frame with +/- 5dB accuracy compared to “real” EIRP of the STA “Link Margin” (8 bits, signed integer, unit dB) contains information on sufficient / un-sufficient relative Rx power level at the time and at the rate for which the TPC REQUEST action frame was received by the STA. Concept very similar to PSNI proposal. Joe Kwak, InterDigital

  8. BEACON and PROBE RESPONSE frames AP AP broadcasts BEACON frame (or replies with PROBE RESPONSE frame) “Country” contains Maximum regulatory power level (8 bits, signed integer, unit dBm) per channel “Power Constraint” contains Offset value (8 bits, signed integer, unit dB) compared to max regulatory power level in “Country” field (… Existing IE’s …) +- “Country” field - “Power Constraint” field- “Transmit power” field- “Link margin” field STA “Transmit Power” (8 bits, signed integer, unit dBm) is equal to Tx power used to transmit the TPC REPORT frame with +/- 5dB accuracy compared to “real” EIRP of the STA “Link Margin” set to 0 in BEACON and PROBE RESPONSE frames Max allowed power in BSS = Maximum regulatory power level – Offset value Joe Kwak, InterDigital

  9. TPC (link probe) operation in 802.11h Joe Kwak, InterDigital

  10. TPC procedures (= “rule set”) • STA’s must indicate their “power capabilities” (= a STA’s min and max possible Tx power levels) in (RE-) ASSOCIATION REQUEST frames • A STA’s (RE-) ASSOCIATION REQUEST may be refused if AP considers that the max or min Tx power capability is unacceptable • AP must send Maximum regulatory Tx power level and Offset value in BEACON and PROBE RESPONSE frames • Tx power of STA or AP shall not exceed the value of, • Maximum regulatory Tx power level - Offset value • TPC REQUEST / RESPONSE action frames containing Tx power and link margin for adaptation of the Tx power (criteria / RRM algorithms obviously not specified, only measurements and messaging as essential tools) Joe Kwak, InterDigital

  11. More thoughts … • Reported Tx power and Link margin from TPC REPORT frames are not made available in MIB in current 11h draft (a STA’s min and max power capability are available though) • 11h only applies to 11a in 5GHz band in Europe • Several more considerations for operating 11h TPC with PCF/DCF and EDCA/HCF (11e), see references • Special provisions are made for special operational scenarios like IBSS (i.e. non infra-structure mode) Joe Kwak, InterDigital

  12. Aspects / benefits of TPC Joe Kwak, InterDigital

  13. If STA reported Tx power levels and link margins are made available in AP MIB, effective load control and BSS range adjustments become possible Maximum range in a BSS is essentially dependent on the maximum Tx power that is configured in AP Range and load controlAdjustable coverage areas See references for results on capacity increases Joe Kwak, InterDigital

  14. Conceptual summary ofproposal for 11k • Take over the complete Transmit-Power-Control related draft specifications from 11h into 11k (see summary on slide 6) • In addition, consider, • Making the PHY measurements reported by means of TPC REQUEST / REPORT frames fully available in AP MIB on an individual per-STA basis with history • Potential alignments / extensions with PHY measurements proposed so far in 11k in MEASUREMENT REQUEST / REPORT frames Joe Kwak, InterDigital

  15. Why should 802.11k consider 11h TPC for inclusion ? • Some parts of 11h TPC draft specification relate to RRM control, some parts are purely link measurements (Tx EIRP and link margin etc.) • When 11k was created, biggest concern on inclusion of RRM control features in the scope of the group was on timely completion of the new supplement - not the need for it was questioned…(the measurement part was simply considered to be less controversial and more consensus-prone) • But,… the 11h draft is stable and likely to be released well before 11k completes • 11h TPC mechanism offers a baseline tool set (RRM measurements and control) for interference mitigation – an extension to 2.4Ghz and other PHY’s than 11a is straightforward and should not be controversial Joe Kwak, InterDigital

  16. Strawpole for normative text • Should we draft normative text along these lines to incorporate 11h TPC into TGk draft? • Vote YEA _______ • Vote NEA _______ • ABSTAIN _______ Joe Kwak, InterDigital

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