Bluetooth 5.1provides new "direction-finding" features that allow Bluetooth devices to identify physical location to the centimeter, which helps in indoor positioning. This latest version includes features that can also make more reliable Bluetooth connections.
Bluetooth devices can now set your location
Current Bluetooth proximity systems can guess how far a device like your smarthome or smartwatch is using signal strength. They may know that you are a few meters away, but they do not know the direction.
It is enhanced with a new directional function in Bluetooth 5.1, just announced by the Bluetooth Special Interest Group (SIG) industry group that monitors Bluetooth. A positioning system can now determine which direction a Bluetooth signal comes from.
Bluetooth 5.1 offers two different methods for determining direction, the name "Arrival angle" (AoA) and "Departure angle" (AoD). One of the two devices must have a set of several antennas, and the data received from these antennas can be used to identify the direction the Bluetooth signal comes from.
If you carry a smartphone around and that phone has Bluetooth 5.1, a positioning system can have a good idea of your exact location. This can be used to improve indoor navigation, find lost keys or activate the smarthome hardware to better identify your location.
Faster connection initiation with less power supply
As you would expect from the version number, Bluetooth 5.1 is not a big step with many changes, as Bluetooth 5.0 was. Its other changes are quite small, but are still useful.  Low energy Bluetooth devices use something called "Generic Attribute Profile," or GATT, when a client device connects, it performs "service discovery" to see what the server device supports. It takes time and energy. Bluetooth 5.1 performs more aggressive caching and clients can skip the service discovery stage when nothing has changed.These "GATT cache enhancements" mean that the connection happens faster and less energy is spent.
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Connection ad improvements
Bluetooth 5.1 contains several improvements to advertising. noning "refers to how a Bluetooth device sends it available to connect, announcing its availability to other nearby Bluetooth devices. This would make the connections work better.
A new feature is "randomized advertising channel indexing." Bluetooth 5.0 required devices to cycle through channels 37, 38 and 39 in strict order. Now, devices can select random channels. This reduces the odds that two Bluetooth devices will interfere with each other and "talk over" each other on the same channels when they announce their readiness to connect, and it will be helpful in locations with many Bluetooth devices.
Bluetooth 5.0 added the ability of devices to synchronize their scan for connection to the "advertising scheme" of another device. For example, if you connect your smartphone to a TV via Bluetooth, the TV can tell your phone exactly when it will advertise with a data field named SyncInfo. Your phone does not need to constantly search for the TV, but knows exactly when the TV will market itself. This saves power and can possibly help if the devices need to change data at a precise time.
But this "periodic ad sync exchange" uses a little power, and low power devices may not want to waste their energy on it. With "periodic ad synchronization transfer", connected devices can transfer data to each other, for example, your smartphone can transfer information about the TV's advertising schedule directly to your smartwatch instead of forcing your smartwatch to communicate this information with the TV. with low power, which makes the batteries long.
More technical details on how exactly these features work are available in the official Bluetooth core specification feature overview. The document also contains some minor changes that we did not mention here.