Bluetooth 5.3 vs 5.2: Key Differences Explained

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What's the difference between Bluetooth 5.3 vs 5.2? As the standard in short-range wireless communication, Bluetooth continues to evolve and improve.

And while the nomenclature suggests that 5.3 is an incremental update over 5.2, there are some significant differences between the two.

Bluetooth 5.3 was officially released in July 2021. And it claims to add several feature enhancements. Let's have a closer look at what the main differences are, and what it actually means.

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Bluetooth 5.3 vs 5.2: Key Differences

We'll get into the detail shortly, but the changes in Bluetooth 5.3 can be broadly summarised as changes that are intended to improve power consumption, device performance, and create an enhanced user experience.

Let's look at the four main changes, as outlined in Bluetooth's New Core Specification v5.3 Feature Enhancements blog post.

Channel Classification Enhancement

This is a feature that is designed to increase connection reliability, by allowing the peripheral device to perform channel classification.

This can all get a bit technical, but two Bluetooth devices that are connected use a "spread spectrum technique" called adaptive frequency hopping (AFH). Bluetooth sends packets of data through smaller channels, and hops between them, based on a channel selection algorithm.

Previously all this work was done by the central device. But sometimes this could lead to a mismatch between suitable frequencies, especially when devices are further apart.

Now, peripheral devices can also perform channel classification, to help ensure that the right channels are being used, improving throughput and reliability.

Scene of office workers - Bluetooth 5.2 vs 5.3
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Credit: BluetoothSIG
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Encryption Key Size Control Enhancement

Bluetooth devices use encryption to ensure that only authorised devices have access to whatever data is being transmitted.

5.3 offers a new "optional Host Controller Interface command" which allows a host to specify the minimum key size a controller can accept when creating a connection with another device.

This seems like it will primarily benefit IoT devices such as medical equipment, commercial lighting, and access control.

Periodic Advertising Enhancement

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Bluetooth devices usually send multiple copies of the same data, to increase the chances of that data being received.

Periodic Advertising means that receiving devices can identify and discard any data they have received before, without sending it to the host. This has the benefit of reducing energy consumption on processing packets of redundant data.

Removal of Alternate MAC and PHY (AMP) Extension

Previous versions of Bluetooth contained this system, which allowed Bluetooth systems to include secondary controllers alongside the primary ones.

However, the use of AMP is low, so the decision was taken to remove this feature from Bluetooth 5.3.

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Connection Subrating

Bluetooth 5.3 adds a new connection subrating feature, which enables rapid switching between high and low-duty cycles.

A low duty cycle is more energy efficient, while a high duty cycle uses more power, but offers higher bandwidth. The ability to rapidly switch between the two modes can be highly beneficial.

The example offered by Bluetooth is a hearing aid, which typically requires a low duty cycle, but needs to switch to high duty when the wearer receives a phone call, or plays music on their smartphone. It will also benefit Bluetooth monitoring systems which use sensors.

What Does This All Mean?

There's a lot of quite technical information to process, so we don't blame you if some of it isn't immediately clear. we can summarise these changes as follows:

  • Bluetooth 5.3 will offer faster switching between low duty and high duty cycles, and is therefore more energy efficient than 5.2
  • Removing redundant data will also reduce energy consumption.
  • Bluetooth 5.3 should also reduce interference, and boost signal quality.
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This means that in new devices, such as the iPhone 14, audio quality will be improved, battery life will be improved, and in general, there will be an uplift in performance. Of course, Bluetooth 5.2 was still very good, so the differences may not be immediately obvious when you go about your day-to-day life. But they are there, just the same.