Whether you’re a beginner or an expert in Bluetooth Low Energy development, it’s always good to take a step back and revisit some of the basics and facts.
In this post, I’ll be going through a list of 21 facts about Bluetooth Low Energy technology. You may know about all of these, but it’s always good to get a refresher from time to time.
- Bluetooth Low Energy is backward-compatible
What this means is that if you develop a BLE device today that is running the latest version of Bluetooth (5.2), you are guaranteed that you can interact with another BLE device that’s running the very first version that supported BLE (Bluetooth version 4.0). There are exceptions to this rule, specifically when one of the devices implements an optional feature of a specific Bluetooth version, but when it comes to the core functionality, the backward-compatibility is guaranteed by the spec.
- Bluetooth Low Energy is capable of achieving ranges of over 1 kilometer
When most people think of BLE, they think short-range communication, and due to good reasons, since the earlier Bluetooth specifications focused on these kinds of applications. However, with Bluetooth 5.0, a new mode called long-range mode (Coded PHY) was introduced and allowed BLE devices to communicate at much longer ranges, up to 1.5 km line-of-sight.
- Bluetooth Low Energy supports point-to-point, star, and mesh topologies
Bluetooth Low Energy is one of the few low-power wireless technologies to support multiple topologies that can address many different applications. It natively supports point-to-point communication such as between your smartphone and your fitness tracker. Also, it supports one-to-many topologies such as a Bluetooth Low Energy hub interfacing with multiple smart home devices at the same time. Finally, BLE also supports a many-to-many topology (mesh) with the introduction of the Bluetooth mesh specification in July 2017.
- Bluetooth Low Energy advertising packets contain up to 31 bytes of data
This is the standard size of the advertising payload for packets sent on the Primary Advertising channels (37, 38, and 39). However, keep in mind that the 31 bytes will include at least two bytes: one for length, and another for type. This leaves 29 bytes for user data. Also, keep in mind that if you have multiple fields of different advertising data types, then each of these types will use up two additional bytes for the length and type of each.
For advertising packets sent on the Secondary Advertising channels (introduced in Bluetooth 5.0), the payload goes up to 254 bytes instead of 31 bytes.
- Bluetooth 5.0 introduced two new modes: high-speed and long-range
In Bluetooth version 5.0, two new modes were introduced (each utilizes a new PHY): high-speed mode (2M PHY) and long-range mode (Coded PHY).
- Bluetooth Low Energy can achieve a throughput of up to 1.4 Mbps
With the introduction of the 2M PHY in Bluetooth 5.0, a throughput of up to 1.4 Mbps can be achieved. If using the standard 1M PHY, then the maximum user-data throughput is around 700 kbps.
The reason the throughputs are not up to the 2M or 1M is that the packets include header overhead and gaps in between the packets, so the user-level data throughput is reduced.
- Many new features introduced in new versions of Bluetooth are optional
When looking for a Bluetooth Low Energy chipset, it’s important to keep in mind that an advertised Bluetooth version supported by the chipset does not necessarily mean that a specific feature of that version is supported. For example, the 2M PHY and Coded PHY are both optional features in Bluetooth 5.0, so make sure that you study the datasheet and specs of a chosen Bluetooth Low Energy chipset to make sure it supports the Bluetooth features you’re interested in.
- 100% of shipped smartphones, laptops, and tablets will support both Bluetooth Low Energy and Bluetooth Classic in 2024
Per the most recent Bluetooth Market Update report, 100% of all new platform devices will support Bluetooth Classic + LE by 2024.
- There is no defined maximum number of connections between a Central and Peripherals per the Bluetooth spec
The Bluetooth specification does not dictate a limit to the number of connections between a BLE central and BLE peripherals. However, your device will probably be limited by the amount of memory available and the Bluetooth stack implementation. So, make sure you check your chipset vendor’s documentation and datasheets for the limits imposed by the stack and memory available.
- Anyone can download the latest official Bluetooth specification documents for free
Unlike many other low-power wireless technologies, the Bluetooth SIG provides access to the official Bluetooth specification documents for anyone to download, for free. You can download the latest Bluetooth Core Specification documents here: https://www.bluetooth.com/specifications/bluetooth-core-specification/
- What is the Bluetooth SIG?
The Bluetooth SIG (Special Interest Group) is the non-profit organization behind managing the technical specification, marketing, and qualification/certification of Bluetooth products. But did you know that the technical specifications are actually created and developed by working groups run by Bluetooth member companies such as Apple, Google, Samsung, Qualcomm, etc.?
- Certification fees for a Bluetooth product are fixed per product listing
Certification fees for a Bluetooth product which include qualification and listing fees are not on a royalty-basis, but rather are per product shipped.
- Bluetooth beacons have become the most popular solution for indoor navigation and asset tracking
Over the past few years, and especially since Apple released the popular iBeacon standard (which is based on BLE), the utilization of Bluetooth beacons has become the most popular solution for indoor navigation and asset tracking applications.
- Bluetooth Low Energy operates in the 2.4 GHz ISM band shared by a few other wireless technologies including Zigbee and Wi-Fi
The one characteristic that distinguishes Bluetooth Low Energy from other similar wireless technologies is the utilization of a technique called frequency hopping. This technique allows it to coexist with the other RF signals in the area while still maintaining a robust connection between two Bluetooth devices.
- The Bluetooth Low Energy spectrum is divided into 40 RF channels
Three of these channels are called Primary Advertising channels. The remaining 37 channels are used for Secondary advertisements and data packets transmitted during a connection. Each of these channels is 2MHz wide.
- Long-range mode (Coded PHY) can be used for enhancing reliability
Coded PHY can be used not only for enhancing the range of Bluetooth Low Energy communication but also for increasing the reliability of connections and advertisements through multiple obstacles. When operating on the Coded PHY, the receiver sensitivity is increased and the transmitted packets utilize a Forward Error Correction mechanism, which both allow for the recovery of the original data from a corrupt packet.
- You can switch between using the three PHYs: Coded PHY, 1M PHY, and 2M PHY on the fly during a connection
This is a powerful feature that provides flexibility to Bluetooth developers. It allows devices to adjust and adapt based on the environment and implemented application. The capability, however, depends on both devices in a connection supporting the PHY being switched to.
- You can utilize different PHYs to be used in each direction
The Bluetooth specification allows a PHY update procedure that can be sent from the master or requested by the slave to use different PHYs in each direction of data transmission (master –> slave vs. slave –> master).
- Bluetooth Classic (BR/EDR) and Bluetooth Low Energy are not compatible
This means that a Bluetooth Classic device cannot interact with a Bluetooth Low Energy device and vice versa. That is why most smartphones, tablets, and PCs nowadays include dual-mode Bluetooth radios which allow the phone to interact with both types of devices.
- A guide for developing a BLE peripheral that interacts with an iOS device
If you are developing a Bluetooth Low Energy peripheral device that will be interfaced with an iOS mobile app, you should check out Apple’s Accessory Design Guidelines document: https://developer.apple.com/accessories/Accessory-Design-Guidelines.pdf.
In this document, Apple lays out recommendations for the different Bluetooth Low Energy parameters including preferred connection parameters, advertising intervals, advertising types, etc.
- This one parameter allows your BLE peripheral to consume less power while still being able to achieve low latency
For optimal power consumption by a Bluetooth Low Energy peripheral, while also being able to achieve low latency, you can define a non-zero Slave Latency value. The Slave Latency parameter allows the slave to skip a number of connection events when no data is available for transfer. This ensures that even when the slave skips those connection events, the master will not consider the connection lost. However, a non-zero value still allows the slave to wake up and transfer data at every connection interval when needed and achieving low latency.
For example, if you set a Slave Latency value of 3 and a connection interval of 15 ms, then if the slave does not have any data during the 15 ms, it can skip up to 3 consecutive connection intervals and then waking up the radio and sending data after around 45 ms.
Hopefully you’ve learned something new from these facts, or at least refreshed your memory on some of these facts.
Take your BLE knowledge to the next level!
If you’re looking to dig deeper into Bluetooth Low Energy and learn more about the technical details of the technology including implementation on both mobile and embedded devices, then check out the Bluetooth Developer Academy.