List of PPDUs Supported in 802.11n
What is a PPDU in IEEE 802.11n?
A PPDU is the Physical Protocol Data Unit, the format used to transmit data at the physical layer in 802.11n.
What are the main components of an 802.11n PPDU?
It consists of a preamble, SIGNAL field, and data payload fields.
How does 802.11n PPDU differ from earlier 802.11 standards?
802.11n introduces HT (High Throughput) PPDUs with enhanced preambles and multiple spatial streams.
What is the purpose of the preamble in 802.11n PPDU?
The preamble synchronizes transmitter and receiver and allows channel estimation.
What types of PPDUs are defined in 802.11n?
Legacy PPDU, HT Mixed PPDU, and HT Greenfield PPDU.
What is the HT Mixed PPDU?
A PPDU type compatible with legacy 802.11a/b/g devices, containing a legacy preamble plus HT fields.
What is the HT Greenfield PPDU?
A PPDU type optimized for 802.11n-only networks with no legacy preamble, improving efficiency.
How does MIMO affect the PPDU structure in 802.11n?
Multiple spatial streams are transmitted simultaneously, increasing the data payload in the PPDU.
What modulation schemes are used in 802.11n PPDU?
OFDM modulation with BPSK, QPSK, 16-QAM, or 64-QAM depending on the data rate.
What is the SIGNAL field in the 802.11n PPDU?
It carries information about the modulation, coding rate, length, and MCS index.
How long is the preamble in 802.11n PPDUs?
It varies depending on the PPDU type, ranging from 16 to 40 microseconds.
What is the purpose of the HT-SIG field?
The HT-SIG field provides signaling specific to the HT (High Throughput) mode like MCS and spatial stream count.
Does the 802.11n PPDU support channel bonding?
Yes, PPDUs can use 40 MHz channels by bonding two adjacent 20 MHz channels.
How does channel bonding impact the PPDU?
It increases the data payload capacity and throughput by using wider channels.
Are PPDUs encrypted in 802.11n?
Encryption is applied at higher layers; PPDU itself carries encoded but not encrypted data.
How is error detection handled in the PPDU?
Error detection uses CRC in the MAC layer, and channel coding at the PHY layer protects the PPDU.
What is the maximum data rate achievable with 802.11n PPDUs?
Up to 600 Mbps using 4 spatial streams and 40 MHz channels.
How does 802.11n ensure backward compatibility via PPDUs?
By including legacy preambles in HT Mixed PPDUs so older devices can detect transmissions.
What is the difference between PPDU and MPDU?
PPDU is the physical layer data unit including preamble and payload, MPDU is the MAC Protocol Data Unit inside the payload.
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