Category: Beacons

Nordic Wireless Q Magazine

Nordic Semiconductor, the manufacturer of the System on a Chip (SoC) in many beacons, has published the latest online issue of Wireless Quarter Magazine. It showcases the many uses of Nordic SoCs.

The latest issue of the magazine highlights the use of the SoC in the following Bluetooth solutions:

  • A smart animal tracking and management system.
  • A handheld device used by students to answer test questions, record their attendance, answer surveys and provide class feedback.

There are also some interesting articles on:

  • How Bluetooth IoT sensors are enabling insurers to manage risks and mitigate claims by advancing accident prediction and prevention.
  • An explanation of the global chip shortage, manufacturing challenges and mitigations.
  • How IoT data can be used with AI machine learning to improve decision-making.

Read Nordic Semiconductor Wireless Quarter

Bluetooth AoA IQ to Location

Bluetooth direction finding uses locators that have multiple antennas. The antennas tend to be flat patches on a printed circuit board (PCB).

The antennas receive the same radio signal but at slightly different times based on the incident angle. This causes a phase difference in the received radio signal at each antenna.

Software is needed to process the radio signals from the antennas and calculate the incident angle. The radio signals are measured in terms of in-phase and quadrature components (IQ).

Processing the IQ signals isn’t easy because it requires taking account of the relative position of the antennas on the PCB, delays in switching between the antennas (there is only one radio receiver) and the use of complex-number arithmetic. The result is a power spectrum, the peak of which is the expected azimuth and elevation of the radio signal in two dimensions.

The finding of the peak also isn’t easy because it requires looping over lots of values to find the maximum. This is computationally time consuming especially as this has to be done many times per second for multiple locators.

Our LocationEngine™ is the first independent software to provide scalable IQ to location processing. It provides industry-leading accuracy, performance, security and reliability for Bluetooth® AoA direction finding. It’s currently compatible with the Minew AoA Kit but we are working with other manufacturers to support further hardware.

LocationEngine™ is designed in integrate into 3rd party systems to provide x, y, z and also area where locators cover more than one area. We supply PrecisionRTLS™ that uses this data to plot onto plans/maps, provide alerts and store historical data for later reporting.

Contact us about setting up a trial

Beacon Re-Designs

We are increasingly seeing beacon manufacturers providing updated versions of their beacons, not to provide extra functionality but to instead simplify the designs so as to reduce the component count or use fewer or cheaper semiconductors. The semiconductor manufacture crisis has resulted in a shortage of semiconductors that has resulted in component shortages and price rises. Beacon re-designs are an attempt by manufacturers to keep prices lower and in some cases prevent an existential crisis for a particular beacon model.

System on a Chip (SoC)

Some manufacturers are using simpler versions of the System On a Chip (SoC). These typically have less memory or have less functionality. Often the more-capable functionality wasn’t even used in the older beacon variant. Other times, things can be done in software that were performed in hardware. There’s also a trend to remove crystals that provide timing and instead perform this in software. Some manufactures are switching between SoC hardware manufacturers, for example from Nordic to Texas Instruments that requires a total hardware and software re-design.

Care needs to be taken when purchasing beacons especially when purchasing just a few samples and much later purchasing a larger quantity. Changes in hardware design mean that you won’t necessary get the same behaviour. This can affect aspects such as range and battery life. Doing things in software rather than hardware often affects battery use. At BeaconZone we are taking special care to ensure that current stocks of items behave as previously, if necessary specifying a particular variant when re-stocking.

Faraday Bags for Bluetooth

One of the most useful tools when deploying beacons is the Faraday Bag. A Faraday bag allows you purposely block beacons you haven’t yet placed so that they don’t affect testing. During development, it also allows you to simulate beacons or scanning devices going out of range without you even moving.

Faraday bags work by having a very thin gauze layer that block radio signals. Not all types of Faraday bag are the same. For BeaconZone Faraday bags, we had the manufacturer use two layers of gauze to block even the strongest Bluetooth beacons.

For any Faraday bag, the radio signal can leak through any larger holes in the gauze. This includes the opening that should be folded over and attached onto itself using the hook and loop fastening.

Faraday Bags

Beacon Signal Stability Observations

As previously mentioned, we perform signal strength and stability tests across beacons. The data feeds into our consultancy work. Here are some high level observations.

The following graph shows the standard deviation of the RSSI @ 1m, for some of our beacons, measured over a 60 second time period:

beaconsignalstability

Smaller bars are better and represent beacons
whose RSSI varied the least over time.

We found that beacons belonged to one or two groups. Firstly those with very stable RSSI and secondly those with an RSSI that had a standard deviation between about 4 and 6 dBm.

Signal stability is more important when you are using the RSSI to infer distance, either directly from the RSSI itself or indirectly via, for example, the iOS immediate, near and far indicators. RSSI varying without a change of distance might cause more spurious triggering. However, you should keep in mind that environmental factors can often cause variation much larger than the 4 to 6 dBm found in this test. Moving obstacles, for example people, will cause significant variation in RSSI.

Bluetooth LE advertising moves pseudo-randomly between radio channels. The channels use different radio frequencies that, in turn, results in fading of the signal at different distances. We experienced and mitigated similar behaviour in our LocationEngine™. Different radio frequencies experience different constructive and destructive interference at different physical locations. Beacons that move more between channels can cause more rapidly varying received signal strength (RSSI).

Bluetooth Market Update

The Bluetooth SIG, who manage the Bluetooth specifications, have a new market update that provides information on the Bluetooth ecosystem. The most interesting and pertinent segment for our customers is location services:

Location service device shipments are expected to have 25% compound annual growth over the next five years according to ABI Research:

Commercial RTLS are being driven by recent inventory and logistic challenges:

‘Retail and Services’ at 62% is surprising as we would have expected ‘Warehouse and Logistics’ to be the larger segment.

Read about BeaconRTLS™

CoreHW AoA Hardware

CoreHW in Finland is a new entrant in the Bluetooth direction finding ecosystem. Their main product is the CHW10x0 chip that supports switching of complex antenna arrays needed for Bluetooth direction finding. It allows designs with only one component where three to five are usually required. The switch has a fast settling time for RF signals and a good phase balance between antenna ports providing better position accuracy.

CoreHW also has reference antenna arrays and 2D software for angle and position estimation to shorten time-to-market for AoA locator and AoD beacon manufacturers. They have a demo kit including 4 locators, 2 tags, a CorePatch antenna array board with CHW1010 chip, a Bluetooth T5.1 chip for IQ sampling and a USB interface (Ethernet) to connect locators with a Windows PC.

The CoreHW reference boards have some intriguing Medusa-type printed circuit board (PCB) tracks, presumably to keep the track length the same to each antenna to normalise RF signal delays.

We look forward to seeing CoreHW components in their customers’ production devices.

Minew MWL01 AoA Beacon Insights

The MWL01 Beacon is an AoA beacon which means it advertises a constant tone extension (CTS) for angle of arrival detection. An accelerometer detects the degree of movement and adjusts the advertising across three levels between 100ms (fast) -> 250ms (normal) -> 4s (slow) to save battery life. The battery level is provided in the advertising data. Double clicking the button changes the advertising, for example, for SOS notification.

Here are some observations that aren’t immediately obvious in the documentation:

  • While AoA is Bluetooth 5.x, It actually advertises Bluetooth 4.1 rather than 5.x. This makes it suitable for non-AoA applications where it can be detected by non AoA Bluetooth 4.1 receivers. It’s particularly suited for asset tracking because it increases the period between advertising, when not moving, to significantly save battery.
  • You might think the change to 4s advertising isn’t working. Be patient. It takes 5 minutes of normal advertising before it switches to slow advertising. Note that it also takes 5 seconds to go from fast advertising to normal advertising. While the advertising rates can be changed, the times to transition can’t be changed.
  • The beacon that is supplied with the AoA kit is different to that supplied separately. The kit’s MWL01 is fixed to 100ms advertising and can’t be changed. This is because it much easier to evaluate AoA and develop software when the advertising is consistent over time. The kit MWL01 can be upgraded, if necessary, to support the changing advertising period. However, we recommend you keep them as 100ms advertising beacons for ease of testing.
  • The ‘Location Finding’ flag in the AoA advertising is actually an indication of the double button press rather than anything to do with direction finding. This flag stays on for a minute and the blue led flashes during this time. Again, the double button press is only available on the non-kit beacon.
  • The battery level isn’t in the AoA data advertising. The beacon advertises a second connectable broadcast frame that includes the MAC address and battery level every 1s, 1s and 4s in the fast, normal, and slow modes respectively. These times can’t be changed.
  • Unfortunately, Minew are stipulating that the settings and firmware upgrade are only available to people who have signed an NDA with Minew or BeaconZone if you purchased the beacons from us.