Xiaomi Mi 8, the world’s first Smartphone with dual-frequency GNSS – compared to the usual L1 single-frequency devices.
The Mi 8 comes equipped with a Broadcom BCM47755 chip, being capable of a position accuracy within some decimeters. The Broadcom chip computes simultaneously the frequencies of two GNSS: GALILEO E1/E5a and GPS L1/L5. The additional use of the E5a/L5 frequencies reduces particularly the effect of multipathing (= reflection of satellite signals by buildings and cliffs), therefore ensuring a better accuracy.
Update: The latest Mi 9 and Mi 10 feature also L1/L5 & E1/E5a -Dualband-GPS!
Broadcom BCM47755 – GNSS frequencies
- BeiDou B1 (China)
- Galileo E1 (Europe)
- Galileo E5a
- GLONASS L1 (Russia)
- GPS L1 C/A (USA)
- GPS L5
- QZSS L1 (Japan)
- QZSS L5
(provided by: Broadcom)
Since I’m curious about the GPS accuracy of the Xiaomi Mi 8 I tested the Chinese smartphone in the Bavarian Alps while hiking. Especially tour 1 provided a challenging environment with a deep valley, cliffs and forest.
Xiaomi Mi 8 – Our Pragmatic Testing
- Xiaomi Mi 8 (version: MIUI 220.127.116.11 | Stable): Attached to the shoulder strap of our backpack for a perfect GPS reception. The track was recorded with the Android app Locus Map Pro (setting: every 10 m or 10 s).
- Garmin GPSMAP 64s: Placed in the upper pocket of the backpack with the GPS antenna upwards, ensuring a perfect GPS reception. Settings: GPS + GLONASS, track log every 10 m.
- Garmin Oregon 700: Placed at the shoulder strap of our backpack, ensuring a perfect GPS reception. Settings: GPS + GLONASS, automatic track log.
- Garmin fenix 5x: Wrist worn with a limited satellite reception (dynamically moving arm, shaded by the body, antenna not always facing to the sky). Setup: GPS + GALILEO, track log in intelligent mode.
Xiaomi Mi 8 – Results
Wow – the accuracy of the Mi 8 track log can be compared to our reference GPS device, the Garmin GPSMAP 64s and to the Garmin Oregon 700.
The GPSMAP 64s accuracy is a tad better, but you can see the differences only when you have some knowledge of the trail. The track of the fenix 5x from tour 1 shows – as expected – some strong shift, especially in the deep valley with cliffs and forest.
But I have some questions and remarks:
- How would a single frequency smartphone compare?
- Can the Locus Map Pro app compute the additional E5a/L5 signals?
- How does the antenna design of the Xiaomi Mi 8 affects the reception (multifunctional smartphone compared to specialized GPS devices); the antenna has a significant impact on the signal strength.
- Has the low amount of available E5a/L5 satellites an impact on the accuracy?
- GALILEO*: Maximum of three satellites with medium to high signal quality (a bad scenario especially for the fenix 5x), only two dual-frequency satellites (GALILEO will be fully operational in 2020)
- GPS: Maximum of two dual-frequency satellites with medium to high signal quality.
- However, I’mreally pleased by the Xiaomi Mi 8 GPS & GALILEO accuracy
Screenshots: Locus Map Pro & GPSTest Android apps, screenshot locations see map.
- Circles: GPS (USA)
- Squares: GLONASS (Russia)
- Triangles: Beidou (China)
- Rhombus: Galileo (Europe)
- signal quality: red – low, yellow – middle, green – high)
- Height of bars: SNR (signal to noise ratio)
Satellites with two frequencies appear twice in the row with the satellite numbers. The accuracy of "16 m" might be a Mi 8 firmware error.
Update 15 Dec. 2018
The latest update to Android 9 (China ROM MIUI Version 10.1.2.0 PEACNFI) brings CF values to the Xiaomi Mi 8. You can see it in the "GPSTest" App (GPS: L1/L5; GALILEO: E1/E5a).
- Broadcom BCM47755
- World’s first dual-frequency GNSS smartphone … (European GNSS Agency)
- Data Quality From The Dual Frequency … (NSL)
- Portables: The challenge of low power and good GNSS … (u-blox white paper)
- Dual-frequency GNSS on Android devices
- GPSTest app discussion