WiFi6 key technologies: 1024QAMBetty
I will introduce you one of the three key technologies of Wi-Fi 6: 1024QAM.
What is QAM technology?
QAM is used to modulate and demodulate data by using a constellation diagram (dot matrix diagram). In practice, QAM coding is a relationship of 2 to the power of N. For example, 16 QAM, 16 is the fourth power of 2, and it can transmit four bits of data at a time. 802.11n is 64 QAM, which is the sixth power of 2. Therefore, in a constellation set of 64 lattice arrays, I can use any point to carry six bits of data information.
In 802.11ac, the 256QAM can transmit 8 bits of data, which is 2 to the power of 8. What is the increase from 6 to 8? We know that is 33% with a simple arithmetic, that is, compared with 802.11n, 802.11ac increases the rate by 33%. After 802.11ax, we introduced a higher order code, that is, the 10th power of 2. The 1024-QAM (1024QAM can transmit 10 bits of data).
We all know that the increase from 8 to 10 is 25%. That is, compared with 802.11ac, the performance of 1024QAM is improved by 25% compared with that of 256QAM, and the performance is changed to 1024-QAM. One symbol can carry 10 bits of data. We certainly hope that the more data we have, the more we will pay for any revenue.
Where’s the problem? The problem is that the space and time we use do not change. The length of each transmitted symbol is the same as that of the carrier bandwidth and time. At this time, we need to make the dot matrix very dense, which is very high requirements for components. If the signal is good enough, we can restore the data. If the signal is poor, the data may not be restored.
We can make an analogy, like two people talking, if you speak very fast, and you are far away, it is hard to hear, but if you speak very fast and two people are close, can hear clearly, because the voice speed is fast so that the volume will decrease. At the same time, the distance of two people is far, the voice of the conversation is not obvious compared with the background noise. When the signal is not strong enough, it’s hard to get it back.
Let’s take an example: For example, it is also an A4 paper, if this word is very large, even if this paper is far away from me, I can see more clearly, but an A4 paper writing big words cannot write a few, if write small words, that can write a lot, but after the distance, the small words cannot see clearly. Therefore, the 1024-QAM can provide a higher physical layer rate at close range. As the distance increases, the effective signal strength decreases. After the signal and noise ratio decreases, the RF component cannot effectively restore the data.
In this case, once the detected distance is relatively long, after a large number of errors and retransmissions begin to occur in the high-order code transmission.we can only passively change the small words into large characters to ensure normal transmission.Everyone may think that this is a waste of time. However, the Wi-Fi is more and more dense,in our hotel, each room is basically a Wi-Fi signal. The distance is close enough to transmit data with higher data. In our family, wireless projection, AR, and VR are all close to each other. However, we need higher bandwidth. In this case, 1024-QAM can play a big role.
In conclusion, the successful use of 1024-QAM modulation in WIFI6 depends on the channel condition. The more dense constellation point distance requires a stronger EVM (error vector magnitude, used to quantify the performance of the radio receiver or transmitter in modulation precision) and the receiver sensitivity function, and the channel quality requirement is higher than that of other modulation types. Huawei WIFI6 AP, which is supported by 5G, uses precise wireless transceivers and modulation and demodulation design to ensure higher wireless data throughput.