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Bluetooth 5.1 – Six Important Updates for IoT Application and Device Developers

Bluetooth Low Energy is one of the top IoT connectivity protocols. Bluetooth 5.1 is the latest update to the standard and it makes BLE more suitable for Industrial IoT. Read this article for six important BLE 5.1 improvements that IoT application developers and device makers should know!

To compare BLE 5.1 with nine other IoT connectivity protocols, download our IoT Protocol Comparison Guide!

Bluetooth 5.1 Improves BLE Positioning Accuracy

Up to the 5.0 version, Bluetooth has used the signal strength indicator, RSSI (Received Signal Strength Indicator) to estimate the distance between transmitter and receiver. This method has been sufficient for positioning use cases with low accuracy requirements.

Bluetooth Low Energy 5.1 brings more accurate positioning for IoT applications and devices with two new methods:

Device Positioning with Angle of Arrival (AoA)

The device to be located, such as a tag transmits a specific direction-finding packet using a single antenna. The locating device receives that signal through an array of multiple antennae. The receiver gets the same signal through the different antennas with different phase. This phase difference is sampled and used to calculate the relative arrival direction for determining the location of the device.

Device Positioning with Angle of Departure (AoD)

In the Angle of Departure method, the object to be located such as a beacon transmits the same packet using the array of multiple antennae. The receiver has a single antenna, which captures the signal sent by the different antennas of the transmitter array. The signal sent from each transmitter antenna is received with a slightly different in phase. The phase difference is sampled to calculate the relative departure direction for determining the location of the device.

Bluetooth 5.1 new positioning methods
Bluetooth 5.1 positioning based on Angle of Arrival and Angle of Departure.

In Bluetooth 5.1, positioning is calculated based on the relative directions of arrival and departure signals. However, the Bluetooth standard does not specify any algorithms to calculate the directions – this is left for the IoT application developers and device makers.

Bluetooth 5.1 Service Discovery Improvements – GAPP

Bluetooth includes a service discovery procedure based on Generic Application Profile (GAPP) for devices to discover each other through advertising channels – one device is advertising and another device is scanning.

Since some devices rarely, or never, change the attributes during service discovery, the process is both, time and energy-consuming.

Bluetooth 5.1 provides caching for the attributes of the GAPP process when the attributes have minor, or no changes. This simple caching process enables the client and server to skip the complete service discovery if the attributes have not changed, saving time and energy.

The Advertising Improvements in Bluetooth 5.1

BLE 5.1 introduces a couple of improvements for the existing advertising methods.

Improved packet collision avoidance

Bluetooth devices use the channels 37, 38, and 39 of the Bluetooth (ISM) band for advertising. In BLE 5.0, the specification dictated that the advertising should be done in sequence, starting from channel 37.

The collision avoidance in BLE 5.0 is simple. If two or more devices attempt to advertise in the same channel concurrently, they introduce a random delay between 1 and 10 msec before the next attempt.

BLE 5.1 introduces a more effective collision avoidance mechanism – randomized advertising channel selection, instead of the sequenced selection of channels, and the random delay.

Better synchronization for Periodic Advertising   

The Periodic Advertising Sync Transfer (PAST) procedure is used to synchronize the scanning of a specific device. However, the periodic nature of this procedure requires a series of repetitions, which increases overall energy consumption.

To reduce energy consumption, the improved PAST procedure in BLE 5.1 allows a non-involved, third device to perform a synchronization operation between the scanning and the advertising devices.

The third device passes on the new synchronization details to the scanning device over a point-to-point BLE connection to save energy.

Typically, the synchronization target device is power constrained. The third-party device relaying the synchronization details is not power or energy limited, i.e., it can be an appliance connected to mains power.

Bluetooth 5.1 Protocol enhancements

Additional security enhancements bring extra security to the debugging processes. Bluetooth 5.1 adds Host Control Interface (HCI) support for debug keys in Bluetooth Low Energy secure connection. Additionally, Bluetooth 5.1 introduces a new sleep clock accuracy update mechanism, which allows for an increase or decrease of the sleep clock accuracy. This improvement is a new tool for IoT application developers and device makers seeking to reduce power consumption.

Error Correction Improvements in BLE 5.1

The response packets are part of the service discovery process enabled by the GAPP protocol. During scanning process, the target device sends a scan response. The response can include additional fields in extended response packets.

Now BLE 5.1 allows AdvDataInfo (ADI) field to appear in scan responses. This was not possible in previous Bluetooth versions. In another related update, BLE 5.1 also allows for the Advertising ID Set (SID) to appear in the scan responses.

Bluetooth 5.1 QoS updates

The Bluetooth 5.1 standard includes a clarification of the rules of interaction between QoS and flow, related to the context of Bluetooth Basic Rate (BR) and Enhanced Data Rate (EDR). This essentially provides clarifications on the device behavior upon violation of the interaction rules.

Conclusions of Bluetooth 5.1 updates

The Bluetooth 5.1 version makes the Bluetooth Low Energy connectivity protocol more accurate for positioning and location tracking applications and devices.

Thanks to the improvements in service discovery and advertising features, BLE connectivity protocol becomes more scalable and reliable. Also, the BLE-enabled IoT devices can be developed more power-efficient with Bluetooth 5.1.

In conclusion, with the updates in the latest Bluetooth standard, BLE connectivity protocol becomes a more viable option for the Industrial IoT applications!

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