Martin covered scanning, GATT, how to maximise data rates, speed vs reliability and using different PHY for enhanced range or data rates. The second part of the talk covers Bluetooth Mesh and proxy nodes.
One thing not mentioned in the slides, to be careful of, is that connection via a proxy node is relatively slow because it’s limited by the GATT connection. Proxy nodes are good for controlling (sending small amounts of data into) a Bluetooth Mesh but poor if you want to use the connected Android device as a gateway for all outgoing data.
There’s a new virtual Bluetooth Developer Meetup arranged for 15th October 2020. The first event will include talks from experienced Bluetooth developers from Google, Samsung, Foundries.IO and Bluetooth SIG.
The Bluetooth SIG has recently released a 2020 Bluetooth® Market Update identifying new trends and forecasts from ABI Research and other analyst firms.
The use of Bluetooth for location is expected to achieve 32% compound annual growth (CAGR):
Obviously, these and other numbers in the report were analysed prior to the coronavirus crisis.
For Bluetooth Mesh, 90% of end-product Bluetooth® mesh qualifications are lighting focused. As with the introduction of iBeacon, which initially focused on marketing messages, the wider capabilities and opportunities are initially not being fully exploited. Part of the problem is that the standard models that come with Bluetooth Mesh are more lighting focused because the standard was driven by individuals from the lighting industry. Custom models, such used by our SensorMesh™, are possible but take more effort.
Today’s Bluetooth devices use advertising, GATT connection and mesh. Advertising occurs over three channels to reduce the affects of wireless interference. When more than one device advertises at the same time, the data is lost. However, advertising takes of the order of 1ms so the chance of collision is usually small.
In contrast, BlueFlood uses concurrent transmissions (CT) that purposely synchronise transmissions such that if colliding packets are tightly synchronised and have the same contents, the resulting signal might be distorted, but highly probable that they do not destruct each other. This is used with the Glossy flooding protocol and 40 rather than 3 advertising channels.
CT-based protocols achieve enormous performance gains in terms of end-to-end reliability, latency and energy consumption even under harsh interference conditions
Concurrent transmissions are challenging using Bluetooth because transmissions need to be synchronised down to 250ns. Nevertheless, the researchers show this is possible using standard Bluetooth PHY and commercial Nordic SoCs. They achieved an end-to-end loss rate below 1% and managed to receive the signals on a standard smartphone. While the mechanism was fragile it was found to be viable.
There’s a push by the Bluetooth SIG at the moment, promoting long range Bluetooth that appeared with Bluetooth 5 in June 2016. This is presumably because, to date, there haven’t been many long range end-user products. There aren’t many devices out there because you need Bluetooth 5 hardware at both ends of communication and existing devices can’t be upgraded.
Device manufacturers have been waiting for the ‘device at the other end of the communication’ (beacons, sensors, smartphones, single board computers) to become compatible before creating new products using Bluetooth 5 which is a chicken and egg situation. There are also tradeoffs around backwards compatibility and battery power. It’s more complex to create a device that supports Bluetooth 5 and is backwards compatible with Bluetooth 4. Advertising both at the same time uses more power and hence reduces the battery lifetime.
In order to validate Bluetooth 5’s long range claims, Nordic have a new blog post testing long range. The post gives a good explanation of path loss, outside vs inside and deterioration of the signal due to precipitation, humidity and reflected signals. Nordic also have an older post comparing the range of BLE, ZigBee and Thread Protocols.
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.
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.