1. Wi-Fi theoretical bandwidth calculation method
Wi-Fi theoretical bandwidth = (symbol bit length × code rate × number of subcarriers × spatial stream) ÷ transmission time
sign bit length
The number of bits a Symbol can carry is related to debugging.
| 11a/g | 11n | 11ac | 11ax | |
| Maximum Modulation | 64QAM | 64QAM | 256QAM | 1024QAM |
| Number of bits/Symbol | 6 | 6 | 8 | 10 |
code rate
During Wi-Fi transmission, according to the quality of the air interface environment, different numbers of error correction codes are added to improve the reliability of transmission. The worse the air interface environment, the more error correction codes. The lower the rate, and vice versa. At present, the highest bit rate of 11n, 11ac and 11ax is 5/6.
Number of data subcarriers
| bandwidth | 11n | 11ac | 11ax | |
| effective number of subcarriers | HT20 | 52 | 52 | 234 |
| HT40 | 108 | 108 | 468 | |
| VHT80 | N/A | 234 | 980 | |
| VHT160 | N/A | 468 | 1960 |
transmission time
The transmission time is the time required to transmit a Symbol plus a gap (GI). In order to avoid interference between Symbols, there needs to be a certain gap between two adjacent Symbols. Different Wi-Fi standards have different gaps.
Transmission time = Symbol + GI time
As shown in the table below:
| 11b/g/n/ac | 11ax | |
| Symbol | 3.2us | 12.8us |
| Short GI | 0.4us | N/A |
| GI | 0.8us | 0.8us |
| 2*GI | N/A | 1.6us |
| 4*GI | N/A | 3.2us |
Let's calculate the highest rate of 11ax based on the highest bit rate (5/6), the largest spatial stream (8*8), and the largest bandwidth (160M).
Formula: Wi-Fi theoretical bandwidth = (symbol bit length × code rate × number of subcarriers × spatial stream) ÷ transmission time
11ax theoretical bandwidth = (10bit × 5/6 × 1960 * 8) ÷ (12.8 + 0.8) = 9607.86Mbps
2. Speed correspondence table
2.1, 802.11b rate correspondence table
| 802.11b | ||
| spatial flow | Modulation | Rate(Mbps) |
| 1 | DSSS | 1 |
| DSSS | 2 | |
| CCK | 5.5 | |
| CCK | 11 | |
2.2, 802.11a/g rate correspondence table
2.3, 802.11n rate correspondence table
1 flow rate table
2 stream rate tables
3 stream rate tables
4 stream rate tables
