If your application will not be released on the Apple Store, you can use any of the background modes described here . Please read this entire article if you do not understand the background execution in iOS - it is important that you know this as an iOS developer.
You also don't seem to understand how Core Bluetooth works in the background, so please read this article .
In short: you need a good reason to keep your app in the background indefinitely and be accepted by the Apple Store Review.
EDIT:
What OP means is that the device did not wake up. Decision. You need to listen to a specific BLE service in CoreBluetooth to start waking up.
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