“Throughput Fluctuation Caused by Different MIMO Antenna Gains
1. Take 2 TP-Link wireless routers (the specific model is not convenient to disclose), and flash the Openwrt firmware (this can support STA mode).
2. Place one of the devices in the shielding box (hereinafter referred to as DUTA) and the other device outside the shielding box (hereinafter referred to as DUTB).
3. Connect the two antenna ports of the DUTB with 20dB and 30dB attenuators respectively, then connect them to the SMA connectors of the shielding box through the RF coaxial cable, and connect the two omnidirectional antennas to the corresponding SMA connectors inside the shielding box.
4. The two antenna ports of DUTA are directly connected to two omnidirectional antennas. As shown below.
5. Use a wireless bridge between DUTA and DUTB.
6. Wireless throughput test using Iperf between DUTA and DUTB using two computers.
At this time, it is obvious that the traffic measured by Iperf is jumping, rising and falling (forgot to take a screenshot at that time), and through the luci interface of Openwrt, it can be seen that the negotiation rate has been very unstable.
Then do the next experiment:
Repeat the above process and change the two attenuators of the DUTB to 30dB, as shown in the figure below.
Likewise, a wireless throughput test was performed using Iperf between DUTA and DUTB using two computers. At this time, it can be found that the throughput measured by Iperf is very stable and does not change.
The above experiments show that for 2×2 MIMO wireless devices, if the signal strengths received by the two antennas are quite different, the wireless negotiation rate will be unstable, which will further lead to unstable data traffic. Network engineering construction has certain guiding significance.