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August 2009 John Moring

August 2009 John Moring. Maximum Transmit Power in WAVE. Issue. 1609 allows higher layers to set transmit power on individual messages, but Regulatory constraints limit the max tx power, so The stack could be told to transmit at illegal power levels That’s dangerous!. What 802.11 says….

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August 2009 John Moring

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  1. August 2009John Moring Maximum Transmit Power in WAVE

  2. Issue • 1609 allows higher layers to set transmit power on individual messages, but • Regulatory constraints limit the max tx power, so • The stack could be told to transmit at illegal power levels • That’s dangerous!

  3. What 802.11 says… • 11.8.2 • “A STA shall determine a regulatory maximum transmit power for the current channel. The STA shall use the minimum of the following: • - …[info received from an Access Point, not applicable to WAVE] and - Any regulatory maximum transmit power for the channel in the current regulatory domain known by the STA from other sources.” WAVE distributes Transmit Power Level for each SCH in the WSA • This counts as “maximum transmit power … known … from other sources”

  4. Preventing illegal transmissions • The 802.11 MAC/MLME should prevent transmissions from exceeding the allowed maximum, even if requested by higher layers per 802.11/11.8.2 • We will explicitly refer to the requirement from 1609.4 • Assumes the system can distribute the regulatory info

  5. What about the CCH? • WAVE has not historically distributed power constraints for the CCH • Solution: CCH parameters may be included in the Channel Info of the WSA • New feature to be added in 1609.3/.4 d1.4

  6. Regulatory info distribution and usage • Default regulatory info configured out of band for the expected areas of operation • Providers may broadcast regulatory info in WSA • Country String in WSA header • Power levels in Channel Info • Users override defaults on receipt of valid WSA • Power limits over-ridden downward only • Users retain latest received Country String • Users revert to default power levels on leaving Provider coverage

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