High performance, Low Power, Low Cost BLE for IOT Applications
One of the challenging aspects of placing increasing numbers of IOT sensors into consumer and industrial applications is compromised link budget due to non-ideal placement of devices around absorptive or conducting surfaces, and non-ideal antenna and packaging configurations, as well as long range.
The key to success in these challenging environments and use cases is a communication protocol and link budget that support:
low average power
low peak power requirements
long battery life
easy provisioning and management to mobile devices and gateways
BLE 5.0 long range is now a very good option for challenging these IoT use cases. The 5.0 release has an excellent feature for expanding the range of wireless devices called LE Long Range/Coded PHY. This feature provides long range not by increasing power into the antenna or cranking up receive gain settings, but by using “bit repetition/error correction” that sends each bit in the data packet as a coded 8-bit byte, giving more devices at farther distances the opportunity to successfully receive transmissions.
Long-range mode is useful for extending the range of a Bluetooth connection or discovery of advertisements, as well as achieving more robust communication in noisy RF environments and in areas with many obstacles, such as non-ideal device placement, for instance, monitoring sensors deployed in:
Smart cities
Large farms
Industrial manufacturing
Near floors or large metal objects
Medical Devices in a home or hospital setting
Connected homes and buildings
The Blue Tooth Low Energy 5.0 Specification added support for operation in these environments by adding reduced bit rates of 125kbs and 500kbs, FEC (forward error correction) and the ability to increase the power output from +10db to +20db. The key to increasing the link budget of BLE is reducing the effective bit rate and adding forward error correction giving a 12dB improvement in Link budget for a link budget of better than 99dB.
When designing a link protocol, designers must consider the required current, the peak currents during transmit, the message duration, the antenna pattern, and the environment that the system will be utilized in. For instance, a moisture sensor might be placed on a concrete floor in a basement near a large metal water heater. The sensor will need to have a very low average power draw, to ensure that the battery volume is reasonable, and the battery life meets the requirements.
For this difficult use case, the designer can improve the link budget by using a lower transmit power and utilize the link budget improvement provided by the lower bit rate and forward correction and still has the option of increasing the power (if the battery size constraint can be relaxed) to 20dbm and use the full forward error correction rate to get the best link budget achievable to counter the environmentally compromised link budget and possible antenna nulls created by the location near the water heater.
A key aspect of usability is the provisioning of sensor “into” the system or to a gateway. BLE provides a robust set of transmission mechanisms and secure encryption through the advertising and connection mechanisms. In some instance, the devices can send asynchronous advertising packets in order to deliver information without a true connection for the simplest provisioning. In other instance, BLE supports a full paired provisioning connection for circumstances that require an encrypted secure connection to avoid man in the middle attacks , snooping, flooding, or injecting malicious packets.
Additionally, the certification process for BLE 5.0 Long Range devices in a chip down or module configuration has been matured making the challenge of agency certification simpler.
The availability of chip sets and modules from multiple vendors allows for quicker development cycle for these challenging use cases. This broad range of capabilities makes BLE 5.0 Long range a very attractive option.