Hello everyone,
Today I will share with you what is MCS and the implementation of MCS values in products.
What is MCS?
MCS namely Modulation and Coding Scheme
The MCS for WLAN services can be understood as a sequence number combining modulation and coding strategies. The actual link rate of the WIFI device will be dynamically and adaptively selected in the existing MCS table. When the wireless signal is strong, MCS will try to choose a high-level combination (high bit + low redundancy); when the wireless signal is weak, MCS will try to choose a low-level combination (low bit + high redundancy).
The coding mode and code rate relationship corresponding to the MSC number are as follows:
For example: If the MCS is 0, the BPSK modulation method is used, and if the MCS is 11, the 1024AQM modulation method is used.
Definition and interpretation of the MCS field in the protocol
In the above screenshot of the protocol, Figure 9-772e shows the definition of the MCS field in the protocol. This field has a total of 16 Bits, and each 2 bit represents the MCS value corresponding to a spatial stream. For example, B0-B1 represents the first MCS value corresponding to a spatial stream.
When B0-B1 is assigned a value of 00, it means that the first spatial stream supports MSC0-MCS7;
When B0-B1 is assigned a value of 01, it means that the first spatial stream supports MSC0-MSC9;
When B0-B1 is assigned a value of 10, it means that the first space is reserved to support MCS0-MSC11;
When the value of B0-B1 is 11, it means that the first spatial stream does not support HE PPDUs.
The remaining fields and so on.
The MCS value is divided into uplink and downlink, and the data structure definition corresponding to the uplink and the downlink is the same.
Implementation of MCS Values in Products
The he {tx | rx} mcs-map nss nss-value map mcs-value parameter is used to set the MCS value for the number of spatial streams.
By default, the number of received and transmitted spatial streams is 8 and the MCS is 11.
The application scenarios are as follows:
Application scenario
For APs that support the 802.11ax protocol, the rate configuration is achieved through the modulation and coding strategy MCS (Modulation and Coding Scheme) index value. The greater the MCS value, the greater the transmission rate.
When the nss-value value is greater than or equal to the number of spatial streams actually supported by the AP, the MCS value corresponding to all the spatial streams of the AP is mcs-value.
When the nss-value value is less than the number of spatial streams actually supported by the AP, only the MCS value corresponding to the configured spatial stream on the AP is mcs-value, and the maximum MCS value of other spatial streams does not take effect.
For example, the nss-value value is 2, and the number of spatial streams actually supported by the AP is 3. Then only the MCS values corresponding to spatial streams 1 and 2 are mcs-value, and the MCS value of spatial stream 3 does not take effect.
Currently, the product supports the MCS capability carried in Beacon, Probe Resp, and Assoc Resp packets.
The MCS value carried in Beacon packets is as follows:
As shown in the preceding figure, the six uplink streams support MCS11 and the six downlink streams support MCS11.
That is all I want to share with you! Thank you!
