What Is the Capacity of nxn MIMO?
In wired transmission, as shown in Figure 15-1, transmission media of each link are independent of each other. As each one more TX/RX group is added, the throughput capacity is doubled.
To describe it mathematically, only the diagonal element is not 0 in the transmission matrix, as shown in Figure 15-2. Y1 = H1*X1, Y2 = H2*X2, xxx, and Yn = Hn*Xn. When obtaining the transmit signal, the receive end does not need to solve the equation.
For example, if two switches are connected through a GE cable, the bandwidth is 1000 Mbit/s. If they are connected through two GE cables, the bandwidth is 2000 Mbit/s.
In Wi-Fi transmission, as shown in Figure 15-3, transmission media of each link are not independent of each other. As each one more TX/RX group is added, the throughput capacity can be doubled to the maximum.
As shown in Figure 15-4, the receiver can be described using a mathematical formula: Y1 = H11*X1 + H12*X2 + ... + H1n*Xn. That is, X1 can be received by Y1, Y2, and ... Yn. To obtain the transmit signal, the receive end needs to solve the equation.
The Wi-Fi protocol obtains the H matrix by using a pilot with the short training field (STF) and long training field (LTF). During actual data transmission, after receiving Y, the receive end obtains X according to the inverse matrix of H to complete information transmission. The theoretical maximum link setup rate can be reached only when the rank of the H matrix is n and each row vector or column vector is not closely related. This poses a great challenge to the antenna design of APs.
In some tests, the link setup rate between the two ends of a Wi-Fi connection may not reach the highest value. When the AP antenna design is not satisfactory, the positions of the AP and STA need to be adjusted to optimize the H matrix so as to reach the highest link setup rate.
Based on its professional technical capabilities, Huawei designs AP antennas in a delicate and high-level manner. In various tests, the link setup rate is high and the air interface bandwidth is high. Customers can enjoy high-bandwidth and low-latency Wi-Fi networks.