Haven't used this one, even though have used other popular brands... If you search the Net, you will find mixed reviews, mostly advising against.
Here's a recent one dated 4 Jan 2022.
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Xiaomi Mi WiFi Range Extender AC1200 review: an affordable, but limited repeater.
To assess the performance of Xiaomi’s repeater, we repeated the 5 GHz signal from our Netgear RAX200 router to which we connected a laptop PC via an adapter to the 2.5 Gb / s socket. In order to measure the speeds, we transferred a 4.73 GB file (a disk image) from the first laptop PC to a second equipped with an Intel AX200 Wi-Fi 6 chip, but also to a stationary desktop PC located at upstairs and connected to a Gigabyte GC-WBAX200 PCIe card, also with the Intel AX200 chip, but with an external antenna.
The router is positioned in a corner of the housing, the repeater plugged into a socket 15 cm from the floor almost in the middle of the latter. We take a measurement 1 m from the router which gives us the optimal flow rates (point 1), a measurement in the center of the housing 1 m from the repeater (point n ° 2), another in a room about 5 m from the repeater with a load-bearing wall opposite the router (point 4), a third measurement on the fixed PC upstairs through a concrete floor (point 3), and the last measurement on the second floor as well, but above of the first room where the router’s speeds are the lowest (point 5).
The 5 GHz band of the Xiaomi Mi WiFi Range Extender AC1200 offers fairly low speeds, since even in the best case the performance remains below 200 Mb / s. It delivers almost the same performance as the Netgear EX3110 which has a speed cumulative (2.4 GHz + 5 GHz) of 750 Mb / s. More problematic: despite its external antennas, the 5 GHz signal is not even picked up by our laptop PC located at our measurement point n ° 5. A failure that we had never suffered until then.
The performance on the 2.4 GHz band is close to the performance of the 5 GHz band, which is quite logical: the 5 GHz band is used to communicate with the router when the repeated signal is that of 2.4 GHz, and Conversely. Thus, in all cases, we find ourselves limited by the maximum theoretical bandwidth of the 2.4 GHz band of this repeater, i.e. 300 Mb / s. Although the signal is in this case picked up at our point n ° 5, it was not possible for us to complete the transfer of our 4.73 GB file. It would be difficult to use it for anything other than very light internet browsing – forget about video streaming.
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