List of PPDUs Supported in 802.11ah
What is a PPDU in 802.11ah?
PPDU stands for Physical Protocol Data Unit and is the packet format used for transmission at the physical layer in 802.11ah.
What are the main components of the 802.11ah PPDU?
The PPDU consists of the preamble, signal field, service field, data payload, and tail bits.
What is the purpose of the preamble in the PPDU?
The preamble helps the receiver synchronize timing, frequency, and channel estimation before receiving the data.
How does the SIGNAL field function in 802.11ah PPDU?
It contains information about data rate, modulation, coding scheme, and the length of the packet.
What modulation technique is used for the PPDU payload in 802.11ah?
OFDM (Orthogonal Frequency Division Multiplexing) is used for the PPDU payload modulation.
How does 802.11ah PPDU support different data rates?
By varying modulation types and coding rates specified in the SIGNAL field.
What is the role of the service field in the PPDU?
It provides padding and scrambling initialization for better error resilience.
What are tail bits in the PPDU?
Tail bits are appended to terminate convolutional coding for accurate decoding.
Does 802.11ah PPDU support different channel bandwidths?
Yes, it supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz channels.
How does the preamble length vary in 802.11ah PPDU?
Preamble length depends on the channel bandwidth and PHY type.
What is the typical duration of an 802.11ah PPDU?
It varies widely depending on data rate and packet size, from a few milliseconds up to tens of milliseconds.
How does 802.11ah PPDU ensure synchronization?
The preamble includes special sequences used for timing and frequency synchronization.
What is the difference between Legacy and High Throughput PPDU in 802.11ah?
Legacy PPDU uses basic modulation with longer preambles; High Throughput PPDU supports advanced modulation and coding schemes for faster rates.
How does 802.11ah PPDU handle error detection?
Through cyclic redundancy check (CRC) fields in the MAC frame, protected by the PHY coding.
Can the PPDU format be extended for future features?
Yes, the protocol allows extensions for enhanced features while maintaining backward compatibility.
What is the significance of OFDM symbols in the PPDU?
OFDM symbols carry the encoded data and pilot tones for channel estimation.
How is power efficiency considered in PPDU transmission?
Short preambles and efficient coding reduce transmission time, saving energy in battery-powered devices.
How does 802.11ah PPDU support long-range communication?
By using narrow bandwidths and robust modulation schemes to maintain signal integrity over distance.
Is the PPDU structure similar to other 802.11 standards?
It follows a similar basic structure but is optimized for sub-1 GHz operation and IoT use cases.
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