Geo-location is one of the most important information for any use case or any industry, be it Telecommunication, Marketing, Logistics, Security etc. Most of the Geo-location solutions are based on GPS, still the accuracy levels could be as bad as ~50-100m in urban environments depending upon the quality of GPS Signal, Mobility and Quality of Sensor on the device. The accuracy becomes much more important in dense urban areas and security/ emergency services use cases. With Internet of things, connected devices, connected cars most of the decisions will be in cities, in real time and need high level of accuracy.
Recently, Broadcom launched their new chip, BCM47755 , location hub which is a single-chip device that combines location awareness capabilities with the typical functions of a sensor hub. The combination provides synergistic benefits that cannot be achieved with multiple ICs :
- High accuracy
- Low power consumyion
- Small form factor
The BCM47755 supports two frequencies (L1+L5), and as a result, achieves lane-level accuracy outdoors and much higher resistance to multipath and reflected signals in urban scenarios, as well as higher interference and jamming immunity. Furthermore, the BCM47755 incorporates numerous technologies that enable ultralow power consumption in both the location function and the sensor hub function. The device features a low-power RF path, a Big/Little CPU configuration composed of an ARM-based 32-bit Cortex-M4F (CM4), an ARM-based Cortex-M0 (CM0), and is built in a 28 nm process.
L5, How it helps with Accuracy :
L5 signals are brief that the reflections are unlikely to overlap with the direct signal. The receiver chip can simply ignore any signal after the first one it receives, which is the direct path. The Broadcom chip also uses information in the phase of the carrier signal to further improve accuracy.
Tech Talks with Mr. Manuel Del Castillo
Techplayon got chance to speak with Manuel del Castillo,Associate Director, GNSS Product Marketing at Broadcom , about key features, availability and more about the solution.
[TPO] How does dual frequency solution improves the accuracy and to what level? How are the results, compared to single frequency solution?
[MdC] Satellites transmit a variety of signals, including the basic L1 signal and an advanced L5 signal. Up to now, all GNSS receivers for smartphones used only the basic L1 signal. This is the first time a GNSS receiver for the smartphone market can use two frequencies from each satellite. The benefits of the L5 signal compared to the L1 signal are:
- L5 signal is much more accurate calculating the distance from the receiver to the satellite, because the signal has 10x higher chipping rate (frequency of bits). This translates into an improvement in accuracy of obtained positions outdoors in an open area, that goes from the previous (L1 only receivers) 5m down to 0.3m (for dual freq L1+L5 BCM47755)
- Higher resistance to urban multipath. The new BCM47755 can isolate the direct ray from the reflected paths and therefore avoid the potentially large errors (up to 50-60m) that an L1 only receiver can show in deep urban environments. As a result, the new BCM47755 places you on the right street always in deep urban environments, even before hybridizing the position with sensor information from the smartphone (accelerometers, gyros and altimeters)
- the L5 signal allows for detection of reflections (when the direct ray is blocked), and therefore helps in the selection of the right satellites to use for an accurate position calculation
- using L1 and L5 allows for cancellation of the ionospheric delay error
- using L1 and L5 allows for very fast transition from code tracking to carrier phase tracking, reaching the 0.3m accuracy level
[TPO] How the solution still lowering the power consumption,even being more accurate ?
[MdC] The BCM47755 uses a new RF architecture that is very efficient. Also, the chip is built in 28nm technology, that inherently uses less power than the previous gen 40nm technology
[TPO] How many minimum satellites are needed to lock the accuracy level of centimeters?
[MdC] The more satellites you have available, the better, because you can make a better selection and avoid bad quality signals. Generally speaking, you need at least four satellites to compute a position. Also, you can use a mix of L5 satellites and L1 signals, as long as you have a minimum of 4 satellites. Some satellites still transmit only in L1, but depending on the situation, it may make sense to use them too, because they may be cleaner or have better geometry than other L5 signals, that’s why BCM47755 can simultaneously use any combination of L1 and L5 signals available for a particular position fix.
[TPO] Does the solution takes anything else into account or how the triangulation works with dual frequency?
[MdC] As mentioned before, there are two signals (L1 and L5) available from each satellite for your triangulation, but you still need at least 4 satellites to solve for X, Y, Z and Time, and compute a fix. With the help of sensors from the smartphone, you can sometimes reduce the number of satellites used for the position fix from the theoretical minimum of 4
[TPO] Does this solve Indoor positioning as well? Or we still need help of external BLE. Beacons for Geolocations?
[MdC] The L5 signal has slightly more penetration thru buildings and it is slightly higher in power than the basic L1, but not enough to compute good positions indoors. A hybrid with WiFi location, CID location, BLE beacons, etc is still needed.
[TPO] When can we expect to see this chip in poc devices before actually hitting market ?
[MdC] We are currently sampling to our key customers, and we expect to see devices in the market using the new chip by mid 2018.
More on Broadcom, BCM47755 location hub
Reach out for more questions/Information/Solution to Mr. Manuel Del Castillo