Bluetooth Low Energy : The essential guide

Bluetooth Low Energy (BLE) was introduced back in the days in 2010 as part of Bluetooth with Bluetooth 4.0. Bluetooth Low Energy was originally designed by Nokia under the name Wibree before being definitively adopted by the SIG (the Bluetooth Special Interest Group). Offering easy and reliable access, BLE is highly valued by consumer electronics manufacturers, mobile application developers and engineers. It is more and more suitable for everything related to the Internet of Things (IoT), which is experiencing strong growth today such as indoor positioning or asset tracking , but don’t worry, we will explain everything there is to know about BLE here.

What is Bluetooth Low Energy (BLE)?

You may have seen it often, and you may use it more than you think. But what really is BLE ? Where does it come from and what does it stand for ?

Little history throwback

Let’s jump back in time for a few lines to understand everything better.

In 1999, a standard technology for wireless communication via radio waves was born: Bluetooth. Constantly progressing over time, it spreads very quickly and is integrated into many devices in our daily lives. Starting as a short range communication to replace short distance cable technology such as mouse, headset etc., but because it consumes battery life quickly, it could not answer challenges that the industry would face, needing a low-power consumption technology. Only ten years later, Bluetooth Low Energy was introduced with the release of version 4.0 of the Core Specification. It has the same characteristics as its big brother, but has some important differences.

Now let’s get to the definition of BLE. What do BLE mean?

BLE, you guessed it, is the short version for Bluetooth Low Energy. Besides those designation, it is also known under other names like Bluetooth LE or Bluetooth Smart, its official (marketed) name. To define it simply, Bluetooth Low Energy is a wireless, low power technology, operating in frequencies between 2.4 GHz and 2.483 GHz ISM. It is very similar to WiFi, as it allows nearby devices to connect with each others. However, it was created mainly for IoT applications that need to consume less power but in a extended range of time, going from months to years, depending on the use. BLE made it possible for sensors and beacons to connect with others, despite having a quite small compartment (and thus small batteries). By transferring small amount of data in a punctual way, it makes BLE ideal for industrial use, as it goes in a « sleep mode » when not activated.

How do BLE technology work?

Now we are getting a bit more technical.

BLE has different types of connections. An object connected in BLE can have up to 4 different functions:

• The “Broadcaster”: it can act as a server. Thus, its purpose is to regularly transmit data to a device, but it does not accept any incoming connection.
• “The Observer”: In a second step, the object can only listen to and interpret the data sent by a “broadcaster”. In this situation, the object cannot send connections to the server.
• The “Central”: often a smartphone or a tablet. It is an element that interacts in two different ways: either in advertising mode or in connected mode. He is then the leader and it is from him that the exchange of data starts. What application to connect to ? Discover 5 applications to connect your BLE Tags
• The “Peripheral”: it accepts connections from the exchange and sends data to it periodically. The aim of this system is to package data universally via the protocol so that it can be understood by other devices.

What abour advertising and connected mode?

Bluetooth devices send packets to broadcast data: this is Advertising. These are 31-byte blocks that can contain sender-specific information. They are also used to allow other devices (usually scanners) to connect to them. For information, there are several types of Advertising packages allowing each one to realize different functionalities (used for Direct or Indirect Advertising with or without the possibility of connection).

In BLE, two devices can establish a connection on a master/slave principle. This is connected mode. In this case, the GATT protocol is often used (acronym of “Generic ATTribute”) to transmit the data. This protocol defines how two BLE devices exchange data. It uses the concepts of “services and features” used to describe the information exchanged:

• A service may contain a collection of features
• A characteristic contains a description, a value and information to define the value.

On the frequency side, for Bluetooth 4.2, some will be dedicated to Advertising while others will be specific to the connected mode.

Bluetooth allows bidirectional data exchange using UHF radio waves and operates in the 2.4 GHz band. 40 physical channels are allocated for time and frequency multiplexing, each spaced at 2 MHz (i.e. from 2.4 GHz to 2.8 GHz). Some channels are used for Bluetooth Advertising while others will be used for the connection part.

Bluetooth uses the same frequency range as Wi-Fi, but the resemblance ends there. Bluetooth and especially BLE consumes less energy. However, the range and speed are much less important than for Wi-Fi.

Is BLE different from Bluetooth ?

When trying to understand what is Bluetooth Low Energy, it is essential to understand what’s the difference with Bluetooth. Of course, we are more used to Bluetooth known as Bluetooth Classic, the one we use to stream audio, music, or transfer large file. However, Bluetooth Classic and Bluetooth Smart are both highly used in our everyday life. First, it is important to note that BLE is not compatible with Bluetooth classic. However, some devices might combine both technologies to allow device to communicate. To know which one to use, it is important to know the differences between the two.

Power consumption

The main difference between the two technologies is their power consumption. They key term of BLE is undoubtly low energy. Used for the periodic transfer of small amounts of data at short range, BLE does not consume a lot of energy. In general, BLE consumes half as much power as Bluetooth.

Application and use

This is why those technologies are used for different purposes. BLE target application that need to consume less, i.e. application that does not require the exchange of large amounts of data, therefore retrieving relatively light information (such as time or temperature, for example). Classical Bluetooth is used to process, transfer and exchange many data without interruption (e.g. audio). However, it quickly consumes battery life and costs much more.

Price

The price is therefore another variable when it comes to BLE vs Bluetooth. BLE offering a non-continuous connection, it can operate on battery power for several years at a lower cost than Bluetooth. Its cost remains relatively low and the longevity of its battery is not negligible.

Communication

It is also important to note the communication of Bluetooth Low Energy and classic Bluetooth differs. As we’ve said early, classic Bluetooth is bidirectionnal whereas BLE works in one direction.

Here is a table that summarize the main differences between BLE and Bluetooth Classic.

To learn more in depth the difference between Bluetooth and Bluetooth Low Energy, read more here : Bluetooth vs Bluetooth Low Energy, what’s the difference?

Benefits of BLE

Each protocol has its advantages and disadvantages. Here are some of the key benefits of BLE:

• For the user: Indeed, it comes from a consortium of industry giants (IBM, Microsoft, Intel …) which gives it an adoption and a strong credit of economic stability. It is already integrated in all smartphones, making it easy to use.
• On the security side: the protocol allows to manage several security levels.
• Low power consumption. BLE, even among low power technologies, is considered as a low power technology.
• Free cost for accessing specification documents. You don’t have to be a member of the official group to access the core spec, in contrary to some other wireless technologies
• Lower cost of module and chips
• Low bandwidth
• High proliferation. BLE exist in most phone in the market.

What is BLE used for?

BLE is used for many IoT applications. The Internet of Things, using seamless communication, connect everyday objects to the intenert via devices. Its ecosystem is composed of smart system that use embedded systems, such as sensor, to collect data they get from their environnement. This latter can be a workplace (an office, an hospital), to vehicle or even cities.

BLE became rapidly one of the best option for IoT. When combined, BLE become very suitable for numerous applications, especially for uses where other location tracking technologies are limited such as in indoor environments, where gps systems cannot accurately asses the location of people, objects and others assets. Here are some typical use cases of BLE in IoT  :

People tracking

BLE beacons is also useful when it comes to tracking people (employee, personal, patient or customer). This use case is particularly interesting when it come to the optimisation of one’s journey or  improve one’s safety such as hospital staff tracking. In the recent years, more and more companies uses people tracking solution to ensure the security of their staff on construction site, as it is easy and quick to deploy, and can operate for several months.

Asset tracking :

There are many many advantages to asset tracking. BLE is useful for tracking the location of an asset within indoor or outdoor environnement. Attached to an asset (it could be an object, a moving vehicle or enven a logistic machine), the BLE beacon can provide its real time location system, allowing the reduction of loss of equipment.

Things to keep in mind

Bluetooth Low Energy (BLE) is a technology adapted to the industrial environment since it allows the rapid exchange of information that can be energy consuming such as temperature, humidity or movement. All this while ensuring a battery life twice as long as conventional Bluetooth.