802.11u PHYs
What is the PHY layer in IEEE 802.11u?
The PHY layer in 802.11u defines the physical transmission method for data over the wireless medium, typically based on existing 802.11 PHYs.
Does 802.11u introduce a new PHY?
No, 802.11u extends MAC and higher layers but uses PHYs defined in other 802.11 standards like 802.11a/b/g/n/ac.
Which frequency bands do 802.11u PHYs operate in?
PHYs used by 802.11u operate in 2.4 GHz and 5 GHz bands, depending on the underlying 802.11 standard.
What modulation schemes are supported by PHYs in 802.11u?
Modulation depends on the underlying PHY; common schemes include DSSS, OFDM, BPSK, QPSK, QAM variants.
Does 802.11u support OFDM PHY?
Yes, 802.11u can use OFDM PHYs, as defined in 802.11a/g/n/ac standards.
What is the typical channel bandwidth for PHYs under 802.11u?
Channel bandwidths vary from 20 MHz to 160 MHz, depending on the PHY (e.g., 802.11n uses 20/40 MHz).
How does PHY impact 802.11u performance?
PHY characteristics like modulation, coding, and bandwidth determine throughput and range for 802.11u communications.
Are 802.11u PHYs compatible with legacy devices?
PHY compatibility depends on the underlying standard; 802.11u works with PHYs that may support backward compatibility.
Can 802.11u PHYs support MIMO?
Yes, if the underlying PHY (like 802.11n or ac) supports MIMO, then 802.11u benefits from it.
What is the role of PHY in 802.11u roaming and network selection?
PHY provides the basic connectivity, while 802.11u extends higher layers for roaming decisions; good PHY quality improves user experience.
Does 802.11u define power levels for PHY transmissions?
No, power levels follow regional regulations and PHY specifications of the underlying 802.11 standard.
Are PHY parameters dynamically adjustable in 802.11u?
Dynamic adjustment is handled by the PHY and MAC layers of the underlying 802.11 standard, not specifically by 802.11u.
Which PHY rate adaptation methods work with 802.11u?
Rate adaptation algorithms are PHY-specific, and 802.11u uses those defined in the underlying PHY standard.
Does 802.11u support multiple PHY types simultaneously?
Yes, 802.11u can operate over different PHYs, depending on the hardware and network configuration.
What PHY layer error correction is used in 802.11u?
Error correction follows the underlying PHY’s methods, such as convolutional coding and LDPC in newer standards.
How does PHY layer affect 802.11u’s quality of service?
Higher PHY data rates and reliability improve QoS by enabling faster, more stable connections.
Is PHY layer security enhanced in 802.11u?
Security enhancements are primarily at MAC and higher layers; PHY layer security is inherited from the underlying PHY standard.
What PHY parameters are critical for 802.11u interworking with cellular networks?
Frequency bands, modulation schemes, and channel bandwidth must be compatible for seamless handoff and interoperability.
Can 802.11u PHY support fast handoffs?
Fast handoffs rely on PHY speed and MAC protocols; faster PHYs help reduce delay during handoff procedures.
Topics in this section,
Reference links