In wifi, a string of bits is converted into a symbol. For example, 2 bits can be converted into a BPSK symbol. A symbol is the modulated carrier, which can be phase, frequency or amplitude.
The unit of symbol is s*hertz. What does it mean? That is, a symbol's interval (unit is s) and its occupied bandwidth (unit is hertz) are multiplied and equal to 1.
For example, with an interval of 12.8us, the bandwidth is 78.125khz. For the 3.2us interval, its bandwidth is 312.5khz.
What is the meaning of the number of bits that each symbol can transmit? For example, 1024-QAM, the number of bits that a symbol can transmit is 10. What does this mean?
In terms of units, it is bits/s/hertz, which is actually the data rate that each hertz can carry, which is called bandwidth efficiency. It means how much bandwidth is needed to carry a data rate. If the bandwidth efficiency is equal to 1, the required bandwidth and the data rate to be carried are equal. If the bandwidth efficiency is greater than 1, then there is no need for bandwidth as large as the data rate, but divide by a bandwidth efficiency.