Bluetooth Audio Standards: How to Choose the Right Wireless Headphones
In the age of modern technologies, you will no longer surprise anyone with wireless devices: We actively use Wi-Fi on phones and laptops, connect wireless mice and keyboards to computers, and listen to music through Bluetooth headphones. And here a drawback occurs: how to choose the best headphones specifically for your devices, because there are many BT audio transmission protocols, and not all of them are supported by the headphones and the device itself?
History and characteristics of the Bluetooth standard
But we will start as usual in the history of BT. And they started creating it, which is remarkable, a few years before USB; In 1994, Ericsson, a well-known manufacturer of telecommunications equipment, began working on this standard. The standard itself was developed as a wireless alternative to a wired RS-232 connection (better known as a serial port). The specifications themselves were ready in 1998, when the Bluetooth SIG group was created, which, along with Ericsson, included IBM, Intel, Nokia, and Toshiba. In 2002, Bluetooth became part of the IEEE 802.15.1 standard (Wi-Fi, remember, is included in the IEEE 802.11 standard). The Bluetooth SIG currently includes more than 18,000 companies, making Bluetooth one of the few important standards for short-range data transmission.
How does Bluetooth work?
Like Wi-Fi and many other systems, it operates in the ISM band, 2.4 to 2.4835 GHz. Of course, using one range leads to signal interference (overlap) and this, in turn, negatively affects stability and performance. operating speed. Considering the fact that sound should always be transmitted with the same quality and without lag, the developers of the standard did a trick. Perhaps the most important problem for BT is precisely Wi-Fi: there are many such networks in the 2.4 GHz band in every home, and there may be 13 channels in this range with a width of 22 MHz.
Here the approach is simple: both the transmitter and the receiver use a fairly wide channel all the time. Yes, it can overlap with other channels, which will negatively affect speed, but not stability, and this suits everyone. Bluetooth uses a different approach: in the ISM band it already has 79 channels (in some countries there are 23, but Russia does not belong to them) with a width of only 1 MHz, and the receiver and transmitter with a frequency of 1600 times per second change the channel according to a given algorithm.
This is specifically done to greatly reduce the probability of signal aliasing in such a small frequency range. But this does not cancel out the interference: small BT channels can get into large Wi-Fi channels, and this will lead to a loss of speed, which is unacceptable for high-quality sound transmission. Therefore, BT uses AFH (Adaptive Frequency Hopping) technology. Its principle is that when changing Bluetooth channels, those channels that fall into the big Wi-Fi channel are ignored.
So if you use Bluetooth in one place, then in theory there are no problems with sound transmission: out of 79 channels, free ones will be selected, which will provide enough speed. Problems can arise if you move, but on the other hand, have you often seen Wi-Fi networks on the street? Therefore, the technology for transmitting sound through BT can be considered completely immune to noise, and it remains only to find out the standards for transmitting sound through it.
