When it comes to a short-range wireless connection, Bluetooth is the standard of choice – the Corona Warning app also uses the technology for a reason. You will find Bluetooth radio modules in PCs, notebooks and tablets as well as in loudspeakers, headphones, smartphones, fitness trackers, smart thermometers, mice and keyboards. The technology is so popular because it is so easy to connect. Actually. Because problems occur often enough. We offer you solutions.
Via Bluetooth, data can be transmitted over short distances by radio. This basically includes video, audio and speech. In the simplest case, two devices are connected to each other – such as a Bluetooth speaker and a smartphone. They represent a piconet (Personal Area Network) with a point-to-point connection. The devices identify each other using AMA (Active Member Address).
As a rule, up to eight devices can be actively connected to one another. Then one speaks of a point-to-multipoint connection. Here, one device acts as a “master”, each other as a “slave”. In addition, the devices in the Piconet can also remain in passive mode. Although they are logged on here, they are marked as “Standby” or “Parked” in the Bluetooth network. That is why they receive the address PMA (Passive Member Address). Since it is an 8-bit address, up to 256 devices (2 to the 8) can theoretically remain in standby mode. If several piconets are combined, one speaks of a scatter network. At least one Bluetooth device must be included here.
To connect two devices via Bluetooth, you have to activate the function on all devices. The pairing process always starts from one device: On the smartphone, select the device from the list that appears under “Settings -> Bluetooth”. Before the actual connection, the devices exchange a security code, which you either only confirm or enter on a device. Only then does the pairing process start.
Bluetooth uses the ISM band (Industrial, Scientific and Medical Band) in the ranges between 2.402 and 2.480 GHz. There are 79 channels available, each of which is 1 MHz wide. The frequency band around 2.4 GHz is also used by other wireless transmission methods – such as WLAN according to IEEE 802.11. That is why Bluetooth operates frequency hopping (FHSS) and changes channels up to 1600 times a second. The many jumps and the small data packets make the bluetooth data transmission very stable.
Bluetooth uses two methods for transmission: Synchronous Connection Oriented (SCO) and Asynchronous Connectionless Link (ACL). SCO is used to send speech that is transmitted in fixed timeslots with a maximum data rate of 64 kbps. Bluetooth sends data via ACL and requires that the transmission device has memory. In contrast to WLAN, Bluetooth masters both transmission methods. WLAN can only transmit asynchronously.
No matter whether smartphones, tablets or PCs – before devices can be connected via Bluetooth, the function must be activated on every device. On smartphones, you will usually find Bluetooth in the “Settings”, less often in the “Network” submenu, and in the status bar, which you can display by swiping downwards on the display. You activate the function by tapping on the symbol.
In mobile devices such as smartphones and tablets, the processor determines the Bluetooth version, because one-chip systems (SOC – Systemon-a-Chip) are installed here. If you want to know which Bluetooth version your Android device comes with, first download a system app such as “Aida64” or “CPU-Z” to the mobile device to find out the exact CPU name. For example with CPU-Z you will find the entry “Qualcomm Snapdragon 808 1.82 GHz” under the “SOC” tab. If you search on the manufacturer’s website, you will also find the Bluetooth version in the processor’s technical data – in this case 4.1.
Bluetooth classes and range
The Bluetooth classes determine the distance and performance that the radio connection supports. ?
class 1: Here is transmitted with 100 milliwatts (mW). The maximum range is 100 meters outdoors. It is the most powerful Bluetooth class. Transmitters and receivers of this class can often be found in notebooks and PCs. ?
2nd grade: The maximum transmission power is 10 milliwatts (mW), which should be sufficient for a maximum distance of up to 50 meters. Corresponding hardware is installed in PCs, laptops or USB Bluetooth adapters. ?
Class 3: The lowest power class achieves 1 milliwatt and a range of 10 meters outdoors. The performance class is found in portable devices such as MP3 players. The range achieved in practice depends not only on the transmission power but also on factors such as the sensitivity of the receiver or the construction of the antennas. There are also obstacles that can affect performance, such as walls or metal parts. You can reduce the radio signal to a few meters even in a powerful class.