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Transmitter Power Control (TPC) for 802.11 WLAN - Rev.1

This document explores the need for Transmitter Power Control (TPC) in 802.11 WLAN networks to comply with European Radiocommunications Committee (ERC) requirements. It discusses different TPC methods for Power Control Function (PCF) and Distributed Coordination Function (DCF), as well as frame format modifications.

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Transmitter Power Control (TPC) for 802.11 WLAN - Rev.1

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  1. Transmitter Power Control (TPC) for 802.11 WLAN - Rev.1 Mika Kasslin and Antti Lappeteläinen Nokia Research Center Mika Kasslin and Antti Lappeteläinen, Nokia

  2. Outline • Why a TPC? • The ERC requirements • TPC for 802.11 • A method for PCF • A method for DCF • Frame format modifications Mika Kasslin and Antti Lappeteläinen, Nokia

  3. Why a TPC? • RLANs can be deployed in 5 GHz band in CEPT countries under certain conditions • European Radiocommunications Committee (ERC) decision ERC/DEC/(99)23 • Power limitations, indoor vs. indoor+outdoor • Transmitter Power Control (TPC) • Dynamic Frequency Selection (DFS) • STA power dissipation, system capacity, etc. Mika Kasslin and Antti Lappeteläinen, Nokia

  4. The ERC requirements • Designated bands • 5150-5350 MHz for indoor use, mean EIRP limited to 200 mW • 5470-5725 MHz for indoor and outdoor use, mean EIRP limited to 1 W • TPC process required • both in up- and downlink to reduce the interference effect caused by RLANs under the coverage area of a satellite • to ensure a mitigation factor of at least 3 dB on the average output power Mika Kasslin and Antti Lappeteläinen, Nokia

  5. Proposed method • Different schemes for CP and CFP • A common power limit for CP • STA-specific power limitation for CFP • Apply mainly to uplink • In downlink AP's transmission power has to be adjustable • Algorithm beyond the scope of the standard • Relatively slow adjustments with small steps preferred Mika Kasslin and Antti Lappeteläinen, Nokia

  6. TPC for CFP (1/2) AP STA AP's transmission power • New control signals conveyed in • BeaconTxP in Beacon management frames • DTxP in Poll data frames TPC process TPC process - broadcasted regularly Normal frame transmission - "background" process - Determine own TxPower as AP_TxP + Corr - Adjust own TxPower - Determine STA-specific correction term STA-specific power correction - unicast frame Mika Kasslin and Antti Lappeteläinen, Nokia

  7. TPC for CFP (2/2) • AP determines its own transmission power "freely" • accuracy requirements in the standard? • DTxP determination • RSSI • PER • QoS • etc. Mika Kasslin and Antti Lappeteläinen, Nokia

  8. TPC for CP AP/1st STA STA • Only upper power limit • BeaconTxP in beacons • Power adjustment needed also in IBSS AP/1st STA's transmission power TPC process TPC process - broadcasted regularly - Determine own TxPower - Adjust own TxPower Mika Kasslin and Antti Lappeteläinen, Nokia

  9. Frame format modifications (1/2) • No new frames required • New fixed field for BeaconTxP in beacon frames • How about defining BeaconTxP as AP_TxP in HIPERLAN/2? • -15-30 dBm covered by 4 bits Mika Kasslin and Antti Lappeteläinen, Nokia

  10. Frame format modifications (2/2) • Duration/ID field used to signalDTxP • Data + CF-Poll, Data + CF-Ack + CF-Poll and CF-Poll Mika Kasslin and Antti Lappeteläinen, Nokia

  11. Adjusting TxP in DL • A mechanism to adjust AP's transmission power in a range of few decibels, e.g. 6 dB • Totally up to the manufacturer to decide how many power levels and which ones are used Mika Kasslin and Antti Lappeteläinen, Nokia

  12. Adjusting TxP in DL - cont. • Basic rules: • adjustments on a frame-by-frame base (i.e. in the beginning of the CFP) • max 3 dB between consecutive frames • upper limit (e.g. 9 dB) for the cumulative power changes over several frames Mika Kasslin and Antti Lappeteläinen, Nokia

  13. Summary • TPC required in 5 GHz in CEPT countries • both up- and downlink • 3 dB mitigation • TPC tailored for 802.11 • STA-specific power control for PCF • Common power limitation for DCF • Modifications to the existing frames • Basic rules for TPC in DL Mika Kasslin and Antti Lappeteläinen, Nokia

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