802.11aj Physical Rates
What are physical rates in 802.11aj?
Physical rates define the data transmission speeds achievable over the wireless channel, determined by modulation, coding, and bandwidth.
What frequency bands does 802.11aj operate in?
802.11aj primarily operates in the 45 GHz and 60 GHz mmWave bands.
What modulation schemes are used for physical rates in 802.11aj?
802.11aj uses BPSK, QPSK, 16-QAM, 64-QAM, and 256-QAM modulation schemes.
What coding rates are supported in 802.11aj PHY?
Coding rates include 1/2, 2/3, 3/4, and 5/6 to balance reliability and throughput.
How does symbol duration affect physical rates?
Symbol length impacts data throughput; shorter symbols allow higher rates but require better channel conditions.
What is the maximum PHY rate supported by 802.11aj?
The maximum rate depends on modulation and bandwidth but can exceed multiple Gbps under optimal conditions.
How does the number of spatial streams (NSS) affect physical rates?
Increasing NSS multiplies throughput by transmitting parallel data streams via MIMO.
Are channel bandwidths wider in 802.11aj compared to previous standards?
Yes, 802.11aj supports channel bandwidths up to 2.16 GHz to enable very high data rates.
Does 802.11aj support OFDM or SC PHY?
802.11aj primarily uses OFDM PHY similar to 802.11ad, optimized for mmWave.
How many usable subcarriers are in 802.11aj OFDM?
52 subcarriers are typically used, matching 802.11ad standards.
Are physical rates affected by beamforming in 802.11aj?
Yes, beamforming improves SNR, enabling higher modulation schemes and faster physical rates.
Does 802.11aj use any new coding techniques?
It builds on LDPC and convolutional coding used in previous standards for error correction.
How is rate adaptation handled in 802.11aj?
Devices dynamically select the best modulation and coding based on channel conditions to optimize rates.
Can 802.11aj physical rates be directly compared with 802.11ad?
They are similar but 802.11aj extends to the 45 GHz band with additional features.
What role does symbol length of 3.6 µs play in rates?
The 3.6 µs symbol length balances between multipath resilience and throughput in mmWave environments.
Are there physical rate differences between single-user and multi-user transmissions?
Multi-user MIMO can aggregate rates across users but individual user rates depend on link quality.
How does 802.11aj handle rate fallback?
The MAC layer can command rate fallback to lower modulation and coding for reliable links.
What determines the choice of modulation and coding scheme (MCS) in 802.11aj?
Channel conditions, SNR, and interference levels guide the MCS selection to maximize throughput and reliability.
Topics in this section,
Modulation |
BW(GHz) |
Tsc |
FSP=BW/Tsc |
Tdata=1/FSP |
GI=Tdata/4 |
Symbol=Tdata+GI |
1/Symbol |
Bits/Symbol |
Code rate |
Usable sc |
Rate |
|---|---|---|---|---|---|---|---|---|---|---|---|
π/2-BPSK |
4.32 |
0.568 |
7605.64 |
0.131 ns |
0.033 ns |
0.164 ns |
6.10 Gsym |
1 |
1/2 |
64 |
770 Mbps |
π/2-BPSK |
4.32 |
0.568 |
7605.64 |
0.131 ns |
0.033 ns |
0.164 ns |
6.10 Gsym |
1 |
13/16 |
64 |
2.00 Gbps |
π/2-QPSK |
4.32 |
0.568 |
7605.64 |
0.131 ns |
0.033 ns |
0.164 ns |
6.10 Gsym |
2 |
1/2 |
64 |
1.54 Gbps |
QPSK |
4.32 |
0.568 |
7605.64 |
0.131 ns |
0.033 ns |
0.164 ns |
6.10 Gsym |
2 |
13/16 |
64 |
3.08 Gbps |
16-QAM |
4.32 |
0.568 |
7605.64 |
0.131 ns |
0.033 ns |
0.164 ns |
6.10 Gsym |
4 |
3/4 |
64 |
6.16 Gbps |
16-QAM |
4.32 |
0.568 |
7605.64 |
0.131 ns |
0.033 ns |
0.164 ns |
6.10 Gsym |
4 |
13/16 |
64 |
9.24 Gbps |
64-QAM |
4.32 |
0.568 |
7605.64 |
0.131 ns |
0.033 ns |
0.164 ns |
6.10 Gsym |
6 |
13/16 |
64 |
13.5 Gbps |
Reference links