802.11d PHYs
What is IEEE 802.11d?
IEEE 802.11d is an amendment that adds support for additional regulatory domains to the 802.11 standard, enabling devices to operate in different countries with country-specific parameters.
Does 802.11d define a new PHY?
No, 802.11d does not introduce a new PHY; it enhances existing PHY layers by providing mechanisms to support new frequency bands and channels based on regulatory requirements.
What is the purpose of the country information element in 802.11d?
It allows access points to broadcast regulatory information such as allowed channels and transmit power limits to clients.
How does 802.11d affect channel selection?
Devices dynamically adjust the set of available channels according to country-specific regulations communicated via 802.11d.
What MAC layer changes does 802.11d introduce?
It adds support for transmitting and processing the country information element in beacon and probe response frames.
How does 802.11d improve interoperability?
By ensuring devices comply with local regulations automatically, 802.11d enables seamless roaming across different regulatory domains.
What frequency bands are supported by 802.11d?
802.11d supports operation on both 2.4 GHz and 5 GHz bands, with region-specific channels as allowed by local regulations.
Does 802.11d modify timing parameters at MAC?
It can modify timing parameters indirectly by adjusting allowed channel usage and regulatory restrictions but does not change core MAC timing functions.
How does a client device learn about country regulations?
Through the country information element broadcasted in beacon frames by the access point or infrastructure network.
What happens if a device does not support 802.11d?
It may not operate legally or efficiently in certain countries as it cannot adjust to region-specific parameters dynamically.
How does 802.11d impact channel availability?
It restricts or enables channels according to local regulations, preventing illegal transmission on forbidden frequencies.
Does 802.11d affect transmit power?
Yes, 802.11d enables devices to adjust their transmit power to comply with country-specific limits.
Is 802.11d mandatory for all 802.11 devices?
No, but many devices implement it to meet global regulatory compliance and enable international roaming.
How does 802.11d handle multi-domain roaming?
Devices switch regulatory settings on the fly by reading updated country info elements as they roam between regions.
What frame types carry the 802.11d country information element?
Primarily beacon frames, probe responses, and sometimes association request frames.
Does 802.11d specify changes to security?
No, 802.11d focuses on regulatory compliance and does not affect security protocols.
How is 802.11d related to 802.11h?
Both address regulatory issues, but 802.11h focuses on dynamic frequency selection and transmit power control in 5 GHz, while 802.11d adds regulatory domain info for all bands.
Can 802.11d support new countries after deployment?
Yes, by updating the country information elements broadcast by APs, new regions can be supported without firmware upgrades to clients.
Does 802.11d impact throughput?
Indirectly—by limiting channels or power levels, it can affect available bandwidth and performance.
What must firmware developers do to implement 802.11d?
They need to implement parsing and adherence to country information elements and adjust radio parameters dynamically.
Topics in this section,
Reference links