What is Bluetooth LE and How Does It Work?

Bluetooth Low Energy (BLE) is a power-efficient version of the classic Bluetooth protocol. Both are widely used in everyday applications, from wireless headphones to smart devices. This includes headset audio, smart devices, peripheral connectivity (such as keyboards, mice, microphones, and printers), and wearables like the Fitbit and Apple Watch. 

BLE, in contrast to standard Bluetooth, is used for low-power consumption devices. It has captured a significant market share for wearables and is employed in industry for more standard IoT applications. BLE can have a greater range and longer run times and tends to use less power than an always-on Bluetooth standard device.

Bluetooth dominates the IoT space with the largest number of users and supported devices.

Where Did BLE Originate?

Bluetooth Low Energy was introduced in December 2009 as an integration into the overarching Bluetooth standard 4.0. It's still classified as a WPAN, or Wireless Personal Area Network (though that particular appellation is being stretched further and further as time progresses). It's managed as a standard by the Bluetooth SIG, or Special Interest Group.

BLE rose out of a need to have a more energy-conscious design than regular Bluetooth, and to some degree to standardize some novel applications that vendors had begun using legacy Bluetooth for; after all, if you don't need your device to beacon or listen all the time, it's kind of a waste to have it doing so. The primary goal of BLE was to create a different standard that would consume less energy, while maintaining the usefulness and range of its previous incarnation.

BLE and Bluetooth Classic are separate protocols and not inherently compatible, although many modern devices support both. One device can run both in many cases; however, your phone, for example, may be capable of communicating with both BLE IoT devices, and your legacy Bluetooth headset. The Bluetooth SIG originally had a logo for devices capable of this, but it has since been retired (inset):

Bluetooth Low Energy (BLE) was the brainchild of researchers at Nokia, who began work on use cases that Bluetooth may not be ideally suited for, but could likely be adapted to. Nokia published this development in 2004, then named Bluetooth Low End Extension. This development continued through a partnership with popular peripheral maker Logitech and culminated in a consumer product known as Wibree. 

In response to this development, the Bluetooth SIG agreed to include it in a future standard, which was eventually incorporated into the 4.0 standard. (Bluetooth reached version 6 in 2024.) One of the more recent and significant additions to the standard was the introduction of Mesh Profiles and Models in 2017.

This chart breaks down the core differences between the two protocols:

Use Cases and Profiles

The Bluetooth SIG designates specifications for ways a BLE device may function, called Profiles. The most common being GATT, or Generic Attribute Profile, which covers the most general use case of sending small amounts of data in a PAN range with a low energy cost relative to the standard. They do, however, define a number of other specialist profiles, such as:

• Mesh Profiles: Allow BLE devices to connect and route data through each other, forming a mesh network.

• Health Care Profiles: Enable clinical tools to measure vital signs such as blood pressure, temperature, and glucose levels.

• Sports and Fitness Profiles: Support fitness trackers, smart scales, and GPS-based activity monitors.

• Others: Other usages might include battery and power level monitoring

BLE is a highly adaptive protocol that has found nearly as many use cases as there are devices. If you were to take a spectrum analysis device out into the wild, you'd likely be shocked by how often you'd catch the signature of a BLE or Bluetooth transmission over the air. It's become so incredibly prolific that we don't much consider IF it will be there, but rather WHEN we'd like to use it.

Millions of users simply leave their Bluetooth on their phone or computer and expect services to auto-connect. A prime example is when people get into their car for the morning commute. Many car manufacturers have designed their systems to automatically connect and begin playing content, such as a user’s playlist or media from an app like YouTube, without requiring any manual setup.

BLE Spectrum and Transmission

Okay, now the nerdy stuff! How does BLE actually work? BLE works in a familiar frequency space, the 2.4 GHz range. Savvy readers will recognize that this is the same range that WiFi and Bluetooth Classic, as well as many other protocols like ISA100.11a, transmit in. However, both Bluetooth and BLE use different channel sets from each other and from WiFi.

Bluetooth Classic runs 79 1MHz-wide channels, and BLE, by contrast, runs 40 2 MHz channels. While both are considered frequency-hopping, BT Classic uses FHSS, or Frequency Hopping Spread Spectrum. 

BLE uses a version of Direct Sequence Spread Spectrum, which is a bit more deterministic. Both use a modulation scheme referred to as Gaussian frequency shift Keying, or GFSK. Unlike FHSS/DSSS, you won't see GFSK represented in WiFi nearly ever, unless it's a proprietary standard and device.

Rather than constant beaconing, BLE typically uses a specific type of packet called a broadcast advertising packet. The packet is sent on a minimum of three channels, and is repeated in a driver-defined period called the advertising interval, which has a "salted" random delay, similar to the backoff timer in WiFi, to avoid undetected interference.

Rate and Use Case Limitations

BLE and Bluetooth are great, but they do, of course, have use cases they're simply not suited for, namely, they have range and rate limitations. Bluetooth has an ideal throughput of approximately 2 Mbps, and BLE has an ideal throughput of just under 1.5 Mbps. 

This means that streaming HD or 4K video is not an option. In real-world scenarios, actual speeds are often lower due to interference and protocol overhead. This rate is generally acceptable for music streaming, chat, or audio, but would be wholly unsuited for larger files. 

No one in the world is going to propose that you beam your CAD file through Bluetooth! That said, most applications that transfer text, small pictures, or streaming audio are handled quite well.

Keep in mind that with BLE, one of the main goals of the protocol is to be low-energy. This means that constant, high-throughput applications should generally be avoided. BLE wants to conserve your battery, and there is an inverse relation between frequency and length of transmission and your battery life.

A good example here is the WHOOP 4.0 fitness tracker, which is designed to sync with the companion app throughout the day while preserving battery life. When used for periodic data uploads—like sleep tracking or recovery monitoring—it offers a practical battery life of around four to five days. However, when live features like continuous heart rate or strain monitoring are enabled, the device transmits data more frequently, significantly shortening battery life.

This is an important consideration when using or recommending Bluetooth Low Energy (BLE) for a particular use case, as there's a direct tradeoff between data transmission frequency and battery longevity. A similar tradeoff exists in ISA100.11a industrial deployments, where sensors are designed to be battery-powered and operate for years without maintenance by limiting the frequency of data transmission.

Final Thoughts

BLE can be a great protocol as long as it's kept within the bounds established by the protocol, and it benefits from incredibly wide adoption, as well as a wide availability of both industrial and consumer support. APs are built with BLE radios, phones have them, and nearly every sophisticated wireless device is capable of being adapted to use them. Armed with this knowledge, you're ready to use this ubiquitous protocol effectively in your home or office and maximize its benefits.