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Bluetooth does not work Android / iPhone (connection)

Who hasn’t experienced it: Bluetooth problems always occur when you don’t need them:

  • before an important customer meeting
  • at the climax of a film
  • during a conversation with the boss

How can I solve the problems quickly and prevent the causes?

This guide explains the solutions.

Let’s get started!

What is Bluetooth?

Bluetooth one for all – Bluetooth problems solutions Steffen Lippke

The Bluetooth Special Interest Group (SIG) developed Bluetooth as a standard for wireless communication over a short distance (1 m to 100 m). The device emits electromagnetic signals in the frequency spectrum between 2.402 GHz and 2.48 gigahertz, which create a Personal Area Network (PAN). The PAN does not connect to the Internet, but only distributes data within the small network.

Headphones, speakers, Mindstroms NXT, game consoles and home automation devices use Bluetooth to exchange music and data. The tech industry sold 4.7 billion devices with Bluetooth in 2023. In recent years, Bluetooth has become a must-have in almost every smartphone.

How does Bluetooth work?

The Bluetooth chip in your smartphone emits electromagnetic waves into its environment. The chip can transmit signals on 79 channels at a speed of 706.25 kbit/s – with the Enhanced Data Rate, a chip can use several channels simultaneously and achieve up to 50 Mbit/s.

Various translations (codecs) are used to transmit data with the highest possible data rate, low latency and low error rate. The codecs include

  • AAC as an energy-intensive codec for qualities up to 250 kbit/s
  • LC3 codec for a double data stream of 80 kbit/s per earbud
  • LLAC-LL for low latency (less than 30 milliseconds) and higher quality (48 kbit/s) – Alternative aptX LL with 40 milliseconds latency
LC3 Codec für die Zukunft - Bluetooth Probleme Lösungen Steffen Lippke
LC3 codec for the future – Bluetooth problems solutions Steffen Lippke

Most users do not know which codec they are using. If you are one of those users who are annoyed by poor transmission quality or high latency (films, video calls, recording), then look for the codecs or Bluetooth versions in the descriptions of your products.

What do the Bluetooth versions mean?

The Bluetooth working group has repeatedly updated the standard since 1998. Each update brings new functions, performance and security ideas with it.

The new Bluetooth 5.3 standard enables music streaming on several devices at the same time. It is also “safer” and more energy efficient. It allows multiple forms of control.

Most common problems and solutions

Programmieren für Bluetooth - Bluetooth Probleme Lösungen Steffen Lippke
Programming for Bluetooth – Bluetooth problems Solutions Steffen Lippke

The Bluetooth data stream does not always work without problems. This section gives you answers to common problems with Bluetooth. As a rule, it is not due to the hardware, but rather to an incorrect software error or software restrictions.

#1 Bluetooth will not connect

Try disconnecting from all Bluetooth devices and restart the Bluetooth on your mobile phone. Restart the other Bluetooth device (switch off the Bluetooth box or unplug the cable for 5 seconds). Try to establish a new connection. Make sure that the other device is no longer connected to other devices.

#2 Music is choppy / Bluetooth drops out

Various reasons can be the cause of a poor signal:

  • Too far away → Move closer to the device. Bluetooth can only send data within a small radius
  • Reinforced concrete is between the devices (or other metallic objects) → Avoid any objects in the line of sight
  • Too many Bluetooth devices in your area – too many 2.4 GHz WLANs in your area → Wireless (Bluetooth) connections overlap (interference). Move to a different location, switch off the other sources (if possible) or shield yourself from the radiation (reinforced concrete, steel mesh, distance, solid walls)

Try to disconnect yourself from all Bluetooth devices and restart the Bluetooth on your mobile phone. Restart the other device (switch off or unplug the cable for 5 seconds). Try to establish a new connection.

#3 Bluetooth shows high latency

Bluetooth is a “consumer” protocol. The standard is not suitable for active monitoring of recordings, e.g. playing the guitar, or for latency-free communication. Latency of 200 ms to 600 ms is possible depending on the codec and end device. If you are in a heated debate with Bluetooth headphones, this latency can be extremely annoying.

You can reduce the latency to 40 ms with apX LL, but you need external antennas for this. You can only achieve even lower latency with monitoring headphones, which transmit highly focussed data via other frequencies (€€€). This is usually bought by musicians on stage.

For films, music and podcasts, the latency is irrelevant and Bluetooth can be used well. Your device may be using the wrong codec. Many devices are capable of multiple codecs, but are talking to an old codec such as low-complexity subband codec (SBC, Advanced Audio Distribution Profile). The operating system may give you an option to select a newer, better codec.

#4 Why are paired devices not connecting?

Another device may have already (unintentionally) paired with your paired device. Speaker Bluetooth dongles usually only allow active pairing because you don’t want two music streams with the same speakers at the same time.

#5 Bluetooth does not connect automatically

Delete the old device from the Bluetooth settings, set up the device again. When you switch on Bluetooth on your smartphone, make sure that the other device is already ready. Some devices need a few seconds or minutes until they are in a pair-able state.

FAQ Bluetooth

RFC auch für Bluetooth - Bluetooth Probleme Lösungen Steffen Lippke
RFC also for Bluetooth – Bluetooth problems solutions Steffen Lippke

Is Bluetooth free of charge?

The connection between two devices is free of charge. You only have to pay for the power consumption of the end devices, which is slightly higher when Bluetooth is active, in use or on standby.

How far does Bluetooth reach?

Class 1 Bluetooth devices can transmit up to 100 metres outdoors. The distance depends on the nature of the receiving and transmitting devices. Class 3 devices can only transmit over a distance of 1 metre. In reality, you can only reach a few metres because objects such as walls strongly attenuate the signal.

Is Bluetooth safe?

Bluetooth has not been considered secure since 2005. A key exchange is necessary for secure communication. Often (old) end devices only use 4 PIN digits or less to establish a connection (key exchange). Brute forcing, i.e. trying out all combinations, is now possible in just a few seconds. In addition, IT security researchers can send interference signals to trigger a reconnection process. When re-negotiating the key, the researcher can bruteforce it.

Bluetooth is still a good choice for music and your favourite podcast. For telephone banking, confidential conversations or buying shares by phone, this medium is a poor choice.

Does Bluetooth have anything to do with the Internet?

Nothing. You don’t have to pay for mobile data, you don’t use up any data volume and you can’t use it to surf. You can use Bluetooth to connect to other devices that also have a Bluetooth chip and exchange data.

Use W-LAN or Bluetooth?

A Wi-Fi connection that is encrypted with the WPA3 standard is considered much more secure. Your W-LAN allows significantly higher data transfer rates of 1 gigabit with W-LAN 6 (ax). WLAN 4 b / g / n is also sufficient for streaming music.

How high is the power consumption of Bluetooth?

Bluetooth Low Energy consumes 15 mA per second, while normal Bluetooth can consume up to 30 mA. Instead of 2.1 Mbit/s of real throughput, Low Energy Bluetooth only sends 1.37 Mbit of data. This speed is sufficient for streaming music.

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