Bluetooth 5 Range Tests

Unseen Tech has a recent whitepaper on Bluetooth 5 range. It describes some tests that were performed to assess Bluetooth 5 to see the improvements in range compared to Bluetooth 4’s typical 30m to 100m. The tests used development boards from Texas Instruments and Nordic that, used outside, achieved about 650m and 750m respectively.

While some companies are claiming Bluetooth 5 support in products, many don’t actually use Bluetooth 5 yet but instead offer an upgrade path to Bluetooth 5. Other’s do offer Bluetooth 5 but downgrade to Bluetooth 4 when communicating with Bluetooth 4 devices (e.g. smartphones) which are still the large majority of devices.

There are also some ultra long range Bluetooth 4 devices that include output power amplifers that can achieve ranges of hundreds of metres and we have one USB powered beacon that reaches up to 4Km.

TRBOnet Update

There’s been an update to TRBOnet to allow DIMETRA Express to use iBeacon-based Indoor Location.

TRBOnet is the system used by Motorola for managing 2-way radios and pinpoints handsets on maps:

The 2-way radios upload GPS data but this obviously doesn’t work indoors where iBeacons are used instead. TRBOnet works with any iBeacons.

Are you an established 2-way radio company?
Contact us for advice on which beacons we have supplied for use with TRBOnet.

Maximising Bluetooth Gateway Throughput

Our article on What are Beacons shows the kind of data sent by beacons. While this might be iBeacon or Eddystone, both are a subset of all Bluetooth advertising as sent out by all Bluetooth LE devices such as smartphones, Fitbits and even industrial machines. The Bluetooth LE advertising advertising is just a short series of numbers.

Gateways look for Bluetooth advertising and send this on to a web server together with the signal strength of the detected device, the gateway’s own Bluetooth MAC address and MAC address of the detected Bluetooth device.

Bluetooth WiFi Gateway

In some situations a very large number of devices can be detected, most of which aren’t the ones that need to be detected. This can cause either the gateway to become overloaded or too much extraneous data to be sent to the server.

All gateways have ways of filtering what advertising is sent to the server. This usually includes matching some or all of the advertising with a given hexadecimal string and the ability to ignore devices weaker than a given signal strength.

Even after filtering, it’s possible in extreme circumstances that a gateway processes too many beacons and becomes overloaded. In these cases it’s important to have a gateway that can support the highest throughput. Gateway specifications detail the typical maximum number of devices that can be detected which varies considerably between devices. Ethernet connected devices tend to be more performant than those connected by WiFi. Also consider setting the gateway to only detect beacons close by and use more gateways per given area. Consider using MQTT in preference to HTTP so as to cause the gateway to do less work.

TINY Bluetooth® Low Energy SoC and Module

Inside every Bluetooth sensor beacon is a System on a Chip (SoC) that’s a small computer that runs code. Dialog Semiconductor, the manufacturer of the SoC in some beacons, has just announced the world’s smallest (2.0mm x 1.7mm) and most power-efficient Bluetooth 5.1 SoC the DA14531.

The high level of integration means it only needs six additional electronic components and a power supply to make a complete Bluetooth low energy system. It’s expected to bring SoCs down to $0.50 in high volume.

While beacons tend to be limited by battery size rather than SoC size, the reduced price might bring downward pressure on cost. The small size is of more use in power harvesting/wearable scenarios such as printed Bluetooth sensors, connected injectors, glucose monitors and smart patches.

Differentiating Between Vehicles and Pedestrians Using Bluetooth Sensing

Javier Martínez Plumé, Juan José Marténez Durá, Ramón Vicente Cirilo Gimeno, Francisco Ramón Soriano García and Antonio García Celda of Universitat de Valencia, Spain have a recent paper on Evaluation of the Use of a City Center through the Use of Bluetooth Sensors Network.

The research looks into using the occurrences of detected Bluetooth MAC addresses to differentiate between vehicles and pedestrians. It’s based on a study that was carried out in the city of Valencia that presented significant complexity due to the large number of pedestrians and motor vehicles.

“Conditions sometimes cause travel times between pedestrians and vehicles to be very close or overlapping, making it impossible to distinguish between trips associated with a pedestrian or with a vehicle by just using travel times”

The researchers implemented a filtering algorithm for the classification of trips so as to distinguish between pedestrians and vehicles using the occurrences of detected MAC addresses.

The results of the study found that 60–70% of the vehicles, in a given itinerary, used the historic centre as a shortcut through the city. These findings caused the City Council of Valencia to take the decision of limiting the traffic speed in the historic centre to 30 km/h so as to encourage use of the city inner ring road where 50 km/h is allowed.

Sensing such as this is part of ‘Smart Cities’, with aims such as reducing pollution, easing traffic and encouraging walking and cycling.

Using Bluetooth and WiFi RSSI for Locating

There’s a recent paper by Hongji Cao,Yunjia Wang,Jingxue Bi and Hongxia Qi of China University of Mining and Technology on An Adaptive Bluetooth/Wi-Fi Fingerprint Positioning Method based on Gaussian Process Regression and Relative Distance.

The paper looks into how to combine both Bluetooth fingerprint positioning (BFP) and Wi-Fi fingerprint positioning (WFP) to provide for an adaptive Bluetooth/Wi-Fi fingerprint positioning system based on Gaussian process regression (GPR).

The adapative feature is particularly useful because fingerprint acquisition requires a great deal of effort and requires subsequent update and maintenance.This new method provides a better positioning than Bluetooth and Wi-Fi positioning alone but at the cost of extra computation.

Read about Using Beacons, iBeacons for Real-time Locating Systems (RTLS)

Bluetooth Range Estimator

The Bluetooth SIG, who create the specifications for Bluetooth, have a new Bluetooth Range Estimator that takes into account the environment, transmit power, antenna gain and received gain to provide an estimated range.

There’s also an associated blog post on 3 Common Myths About Bluetooth.

In terms of beacons, the range usually relates to how they are powered. The beacons with smaller CR2032 batteries tend to be designed for ranges up 50m. Larger CR2477 powered beacons usually reach about 100m. AA battery beacons or those with power amplifers reach hundreds of metres. and some USB beacons can reach up to 4Km. These ranges are outdoors. Indoors, there’s often radio reflections and blocking that reduce range. Beacon orientation can also affect range.

Bluetooth AoA Direction Finding Study Finds Limitations

While we wait for products based on Bluetooth 5.1 direction finding to reach the market, researchers in the UK and Italy have performed a study Dead on Arrival: An Empirical Study of The Bluetooth 5.1 Positioning System.

The paper tests the market readiness of the Bluetooth 5.1 direction finding by experimentally evaluating the performance of the AoA mechanism. The authors took Software-Defined Radios(SDR) manufactured by Ettus Research and emulated Bluetooth AoA data in order to assess the potential accuracy and security.

The results show that accurate angular detection is limited to a restricted range:

“Observe that the error is below 85 cm for more than 95% of the positions. However, this is far from meeting the centimetre level accuracy expected by IoT applications, since the absolute positioning error is <10 cm only in 15% of cases. Although offering sub-meter accuracy, is far from achieving centimetre-level precision.”

It was found that a malicious device can easily alter the truthfulness of the measured AoA data by tampering with the packet structure because the Bluetooth 5.1 standard doesn’t enforce any security provisions. The researchers suggest an improvement to the standard, by changing the receiver, so that instead of using one main antenna and switching to the other only for measuring the phase-delay, it keeps the other antenna active for the next packet to be received.