802.11ah Physical Rates
What frequency band does 802.11ah use for physical rates?
802.11ah operates primarily in the sub-1 GHz frequency bands, such as 900 MHz.
What is the maximum physical data rate supported by 802.11ah?
The maximum data rate of 802.11ah is up to 347 Mbps under ideal conditions.
What modulation techniques are used in 802.11ah?
802.11ah uses OFDM (Orthogonal Frequency Division Multiplexing) with BPSK, QPSK, 16-QAM, and 64-QAM modulations.
How does 802.11ah achieve different data rates?
By varying modulation schemes, coding rates, and channel bandwidths.
What channel bandwidths does 802.11ah support?
802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz channel bandwidths.
Why does 802.11ah use narrower channels than traditional Wi-Fi?
Narrower channels improve range and penetration in sub-1 GHz bands, ideal for IoT and sensor networks.
What is the lowest data rate supported by 802.11ah?
The lowest physical rate is approximately 0.15 Mbps using BPSK modulation with strong coding.
How does 802.11ah adapt data rates dynamically?
It uses rate adaptation algorithms that select modulation and coding based on link quality.
What is the impact of sub-1 GHz operation on physical rates?
Lower frequency bands provide longer range but typically lower maximum data rates compared to 2.4 GHz or 5 GHz bands.
Does 802.11ah support MIMO technology?
802.11ah primarily focuses on single-stream transmissions but can support multiple spatial streams in some implementations.
How many subcarriers does 802.11ah OFDM use?
802.11ah uses 32, 64, or 128 subcarriers depending on the channel bandwidth.
What coding schemes are applied in 802.11ah?
Convolutional coding with various coding rates (e.g., 1/2, 2/3, 3/4) is used for error correction.
How do physical rates affect battery life in 802.11ah devices?
Lower data rates with robust modulation improve range and reduce retransmissions, which can conserve battery life.
What are the typical use cases for different physical rates in 802.11ah?
Lower rates suit sensors and IoT devices with low data needs, higher rates support video or firmware updates.
Is 802.11ah data rate affected by interference?
Yes, interference can reduce effective data rates by forcing more robust modulation and retransmissions.
How does channel bonding affect 802.11ah physical rates?
Channel bonding can combine smaller channels to increase throughput, though it is less common in 802.11ah.
Can 802.11ah physical rates support long-range communication?
Yes, especially at lower rates with narrow bandwidths, allowing communication up to 1 km or more.
What is the role of OFDM in 802.11ah physical rates?
OFDM enables efficient spectrum use and robustness against multipath fading to maintain reliable data rates.
Topics in this section,
Modulation |
BW |
Tsc |
FSP=BW/Tsc |
Tdata=1/FSP |
GI=Tdata/4 |
Symbol=Tdata+GI |
1/Symbol |
Bits/Symbol |
Code rate |
Usable SC |
Data Rate (kbps) |
|---|---|---|---|---|---|---|---|---|---|---|---|
BPSK |
1MHz |
4kHz |
250 µs |
4 ms |
1 ms |
5 ms |
200 Hz |
1 |
1/2 |
32 |
100 |
BPSK |
1MHz |
4kHz |
250 µs |
4 ms |
1 ms |
5 ms |
200 Hz |
1 |
3/4 |
32 |
150 |
QPSK |
1MHz |
4kHz |
250 µs |
4 ms |
1 ms |
5 ms |
200 Hz |
2 |
1/2 |
32 |
200 |
QPSK |
1MHz |
4kHz |
250 µs |
4 ms |
1 ms |
5 ms |
200 Hz |
2 |
3/4 |
32 |
300 |
16-QAM |
1MHz |
4kHz |
250 µs |
4 ms |
1 ms |
5 ms |
200 Hz |
4 |
1/2 |
32 |
400 |
16-QAM |
1MHz |
4kHz |
250 µs |
4 ms |
1 ms |
5 ms |
200 Hz |
4 |
3/4 |
32 |
600 |
64-QAM |
1MHz |
4kHz |
250 µs |
4 ms |
1 ms |
5 ms |
200 Hz |
6 |
2/3 |
32 |
800 |
64-QAM |
1MHz |
4kHz |
250 µs |
4 ms |
1 ms |
5 ms |
200 Hz |
6 |
3/4 |
32 |
900 |
BPSK |
2MHz |
8kHz |
125 µs |
2 ms |
0.5 ms |
2.5 ms |
400 Hz |
1 |
1/2 |
64 |
200 |
BPSK |
2MHz |
8kHz |
125 µs |
2 ms |
0.5 ms |
2.5 ms |
400 Hz |
1 |
3/4 |
64 |
300 |
QPSK |
2MHz |
8kHz |
125 µs |
2 ms |
0.5 ms |
2.5 ms |
400 Hz |
2 |
1/2 |
64 |
400 |
QPSK |
2MHz |
8kHz |
125 µs |
2 ms |
0.5 ms |
2.5 ms |
400 Hz |
2 |
3/4 |
64 |
600 |
16-QAM |
2MHz |
8kHz |
125 µs |
2 ms |
0.5 ms |
2.5 ms |
400 Hz |
4 |
1/2 |
64 |
800 |
16-QAM |
2MHz |
8kHz |
125 µs |
2 ms |
0.5 ms |
2.5 ms |
400 Hz |
4 |
3/4 |
64 |
1200 |
64-QAM |
2MHz |
8kHz |
125 µs |
2 ms |
0.5 ms |
2.5 ms |
400 Hz |
6 |
2/3 |
64 |
1600 |
64-QAM |
2MHz |
8kHz |
125 µs |
2 ms |
0.5 ms |
2.5 ms |
400 Hz |
6 |
3/4 |
64 |
1800 |
BPSK |
4MHz |
16kHz |
62.5 µs |
1 ms |
0.25 ms |
1.25 ms |
800 Hz |
1 |
1/2 |
128 |
400 |
BPSK |
4MHz |
16kHz |
62.5 µs |
1 ms |
0.25 ms |
1.25 ms |
800 Hz |
1 |
3/4 |
128 |
600 |
QPSK |
4MHz |
16kHz |
62.5 µs |
1 ms |
0.25 ms |
1.25 ms |
800 Hz |
2 |
1/2 |
128 |
800 |
QPSK |
4MHz |
16kHz |
62.5 µs |
1 ms |
0.25 ms |
1.25 ms |
800 Hz |
2 |
3/4 |
128 |
1200 |
16-QAM |
4MHz |
16kHz |
62.5 µs |
1 ms |
0.25 ms |
1.25 ms |
800 Hz |
4 |
1/2 |
128 |
1600 |
16-QAM |
4MHz |
16kHz |
62.5 µs |
1 ms |
0.25 ms |
1.25 ms |
800 Hz |
4 |
3/4 |
128 |
2400 |
64-QAM |
4MHz |
16kHz |
62.5 µs |
1 ms |
0.25 ms |
1.25 ms |
800 Hz |
6 |
2/3 |
128 |
3200 |
64-QAM |
4MHz |
16kHz |
62.5 µs |
1 ms |
0.25 ms |
1.25 ms |
800 Hz |
6 |
3/4 |
128 |
3600 |
BPSK |
8MHz |
32kHz |
31.25 µs |
0.5 ms |
0.125 ms |
0.625 ms |
1600 Hz |
1 |
1/2 |
256 |
800 |
BPSK |
8MHz |
32kHz |
31.25 µs |
0.5 ms |
0.125 ms |
0.625 ms |
1600 Hz |
1 |
3/4 |
256 |
1200 |
QPSK |
8MHz |
32kHz |
31.25 µs |
0.5 ms |
0.125 ms |
0.625 ms |
1600 Hz |
2 |
1/2 |
256 |
1600 |
QPSK |
8MHz |
32kHz |
31.25 µs |
0.5 ms |
0.125 ms |
0.625 ms |
1600 Hz |
2 |
3/4 |
256 |
2400 |
16-QAM |
8MHz |
32kHz |
31.25 µs |
0.5 ms |
0.125 ms |
0.625 ms |
1600 Hz |
4 |
1/2 |
256 |
3200 |
16-QAM |
8MHz |
32kHz |
31.25 µs |
0.5 ms |
0.125 ms |
0.625 ms |
1600 Hz |
4 |
3/4 |
256 |
4800 |
64-QAM |
8MHz |
32kHz |
31.25 µs |
0.5 ms |
0.125 ms |
0.625 ms |
1600 Hz |
6 |
2/3 |
256 |
6400 |
64-QAM |
8MHz |
32kHz |
31.25 µs |
0.5 ms |
0.125 ms |
0.625 ms |
1600 Hz |
6 |
3/4 |
256 |
7200 |
BPSK |
16MHz |
64kHz |
15.625 µs |
0.25 ms |
0.0625 ms |
0.3125 ms |
3200 Hz |
1 |
1/2 |
512 |
1600 |
BPSK |
16MHz |
64kHz |
15.625 µs |
0.25 ms |
0.0625 ms |
0.3125 ms |
3200 Hz |
1 |
3/4 |
512 |
2400 |
QPSK |
16MHz |
64kHz |
15.625 µs |
0.25 ms |
0.0625 ms |
0.3125 ms |
3200 Hz |
2 |
1/2 |
512 |
3200 |
QPSK |
16MHz |
64kHz |
15.625 µs |
0.25 ms |
0.0625 ms |
0.3125 ms |
3200 Hz |
2 |
3/4 |
512 |
4800 |
16-QAM |
16MHz |
64kHz |
15.625 µs |
0.25 ms |
0.0625 ms |
0.3125 ms |
3200 Hz |
4 |
1/2 |
512 |
6400 |
16-QAM |
16MHz |
64kHz |
15.625 µs |
0.25 ms |
0.0625 ms |
0.3125 ms |
3200 Hz |
4 |
3/4 |
512 |
9600 |
64-QAM |
16MHz |
64kHz |
15.625 µs |
0.25 ms |
0.0625 ms |
0.3125 ms |
3200 Hz |
6 |
2/3 |
512 |
12800 |
64-QAM |
16MHz |
64kHz |
15.625 µs |
0.25 ms |
0.0625 ms |
0.3125 ms |
3200 Hz |
6 |
3/4 |
512 |
14400 |
Reference links