802.11ad PHYs
What is the PHY in IEEE 802.11ad?
The PHY (Physical Layer) in 802.11ad handles high-speed wireless transmission using the 60 GHz band with directional communication and ultra-wide channels.
What modulation types are used in 802.11ad?
802.11ad supports BPSK, QPSK, 16-QAM, and 64-QAM, depending on the physical layer variant and data rate.
How many PHY types exist in 802.11ad?
There are four PHY types: Control PHY, SC PHY, OFDM PHY, and Spread QPSK (SQPSK) PHY, each optimized for different use cases.
What is SC PHY in 802.11ad?
Single Carrier PHY (SC PHY) uses single-carrier modulation, offering lower complexity and power consumption, suitable for handheld devices.
What is OFDM PHY in 802.11ad?
OFDM PHY uses Orthogonal Frequency Division Multiplexing to achieve higher throughput, especially in less power-sensitive applications.
What is the bandwidth of 802.11ad PHY channels?
Each channel in 802.11ad is 2.16 GHz wide, far exceeding traditional Wi-Fi channel widths.
How fast is 802.11ad PHY?
It supports data rates up to 6.76 Gbps, depending on modulation and coding scheme.
What is the role of beamforming in PHY?
Beamforming focuses transmission and reception in specific directions, overcoming high path loss at 60 GHz.
Is 802.11ad PHY full-duplex?
No, like other Wi-Fi PHYs, it operates in half-duplex mode—transmit and receive occur at different times.
What coding scheme is used in 802.11ad?
LDPC (Low-Density Parity-Check) coding is used for error correction in higher-rate transmissions, improving reliability.
Does 802.11ad use convolutional coding?
Yes, for lower-rate transmissions (e.g., Control PHY), convolutional coding may be used instead of LDPC.
What is the Control PHY?
Control PHY supports robust, low-data-rate communication for link establishment and management.
What is the SQPSK PHY used for?
SQPSK (Spread QPSK) PHY is designed for robust transmission under noisy conditions, using spreading for additional gain.
What is the symbol rate in 802.11ad SC PHY?
The symbol rate can reach 1.76 Gsymbols/s depending on the modulation and configuration.
What is the guard interval in OFDM PHY?
Guard intervals in 802.11ad OFDM PHY reduce inter-symbol interference and can vary with configuration.
What FFT size does 802.11ad OFDM use?
The OFDM PHY uses a 512-point FFT for processing 512 subcarriers in the wide 2.16 GHz channel.
How does PHY preamble work in 802.11ad?
The preamble includes training fields and synchronization sequences needed for accurate beamforming and channel estimation.
Does 802.11ad PHY support rate adaptation?
Yes, dynamic rate selection is used to switch between modulation and coding schemes based on link quality.
What affects PHY performance in 802.11ad?
Line-of-sight, antenna alignment, interference, and distance all significantly impact PHY layer performance.
What is the training field in PHY preamble?
It helps establish timing and phase synchronization and is used for beamforming training in directional links.
Does 802.11ad PHY support MIMO?
No, 802.11ad uses beamforming and directional antennas instead of spatial multiplexing like traditional MIMO.
What is spectral efficiency in 802.11ad PHY?
802.11ad achieves high spectral efficiency due to wide bandwidth and high-order modulation, up to ~3.1 bps/Hz.
How is PHY feedback handled?
Receivers provide channel feedback to optimize beamforming and select modulation and coding schemes.
What is the maximum PHY payload size?
The maximum PSDU (PHY Service Data Unit) size can be over 4,000 bytes, depending on mode and rate.
What is the MAC-PHY interface?
The MAC layer passes frames to the PHY layer, which encodes, modulates, and transmits them over the 60 GHz band.
How does PHY handle interference in 60 GHz?
Directional beams and limited range reduce interference, but PHY must still adapt to reflection and blockage.
Does PHY impact power consumption in 802.11ad?
Yes, higher data rates and beamforming require more processing and power—SC PHY is used to save energy.
What makes 802.11ad PHY different from 802.11a?
802.11ad operates at much higher frequencies, uses wider channels, includes beamforming, and achieves multi-gigabit speeds.
What are typical use cases for 802.11ad PHY?
High-speed short-range applications like wireless docking, VR headsets, and uncompressed video streaming.
Is 802.11ad PHY backward compatible?
No, it is not backward compatible with lower-frequency Wi-Fi standards like 802.11a/b/g/n/ac.
Is 802.11ad PHY still relevant today?
It laid the foundation for 802.11ay and continues to be used in some enterprise and specialty wireless applications.
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