Xiaomi Mix 4 UWB Technology Detailed Science

Xiaomi Mix 4 UWB Technology Detailed

Xiaomi Mix 4 UWB Technology

As Xiaomi’s first under-screen camera flagship, Xiaomi MIX 4 has received a lot of consumer attention since its release. After three years, Xiaomi MIX 4 not only brings a stunning CUP full-screen but also is Xiaomi’s first phone equipped with UWB one-finger connection technology.

Less than a year from the release of the technology, Xiaomi UWB One Finger Link has already landed in mass production on Xiaomi Mi MIX 4. What are the advantages of UWB technology compared to traditional Wi-Fi and Bluetooth-based positioning based on the signal strength? And how is it achieved? In this regard, the official Xiaomi today published UWB technology science.

Xiaomi MIX 4 UWB, compared to traditional Wi-Fi and Bluetooth-based positioning based on signal strength, UWB technology allows for accurate 3D positioning of devices in space.

When used with the Xiaomi TV Master 77″ OLED or Xiaomi One Finger Connect Companion, the phone points to the TV to bring up the operating interface. Unlike other wireless technologies, Ultra-Wideband operates in a wide frequency range of 6-8.5 GHz, and its signal is reflected in the time domain as an ultra-short pulse of only about 2 nanoseconds. Its ultra-short pulse characteristic brings three advantages.

  1. High discrimination: Because of its distinctive characteristics, the UWB receiver can recognize UWB pulses from noisy signal noise, even allowing their signal strength to be somewhat weaker than the background noise. This allows UWB to use lower transmit power, typically up to 30dBm lower than Wi-Fi signals, reducing power consumption while allowing UWB signals to hide in what other communication technologies consider “background noise” and causing little interference. As a result, the MIX 4’s UWB one-finger connectivity does not interfere with the normal operation of radio frequencies such as Wi-Fi, Bluetooth, and 5G.
  2. Because the pulse is extremely short, echoes that bounce off walls and roofs often appear after the pulse ends, so the UWB receiver can effectively identify and ignore the echoes and has better multipath resistance. This makes it possible to use the Time of Flight of the UWB pulse for accurate ranging. Xiaomi MIX 4 can quickly determine the distance of AIoT devices with an error of only 20cm within a range of 10 meters, so it can effectively filter surrounding devices, such as activating only the AIoT devices closest to the user.
  3. UWB can not only perform 1D ToF ranging but also use two receiving antennas to perform 2D positioning using triangulation. 3 receiving antennas on the MIX 4 can perform 3D positioning of AIoT devices, report polar coordinates (longitude angle, latitude angle, and distance) for upper-layer applications, and accurately determine which IoT device the user is pointing at, enabling “One Finger Connection” in just 20ms, complete a positioning.

To accurately locate AIoT devices, all three UWB antennas of each MIX 4 need to be factory calibrated. To support subsequent features such as in-pocket sensorless unlocking, Xiaomi MIX 4 also has an additional transmitting antenna on the side of the phone to better prevent obstruction.

Theoretical applications include not only AIoT control, but also unattended authentication, such as car keys, door locks, gates, and hotel cards, or short-range positionings, such as mall navigation, online car search, bicycle-sharing, and even AR scenarios.


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