Let me investigate just how modern day audio transmission systems which are employed in nowaday’s bluetooth outdoor speakers operate in real-world environments with a large amount of interference from other cordless equipment.
The most popular frequency bands which can be employed by cordless gizmos include the 900 MHz, 2.4 GHz and 5.8 GHz frequency band. Usually the 900 MHz as well as 2.4 GHz frequency bands have started to become clogged by the ever increasing quantity of products just like wireless speakers, cordless telephones and so on. FM type audio transmitters are typically the least reliable in terms of tolerating interference considering that the transmission does not have any mechanism to deal with competing transmitters. However, these transmitters use a rather restricted bandwidth and switching channels may often steer clear of interference. The 2.4 Gigahertz and 5.8 GHz frequency bands are utilized by digital transmitters and also have become quite crowded lately because digital signals take up a lot more bandwidth than analogue transmitters.
Simply changing channels, on the other hand, is no dependable solution for staying away from specific transmitters that use frequency hopping. Frequency hoppers including Bluetooth devices or quite a few cordless telephones are going to hop throughout the entire frequency spectrum. Thereby transmission over channels will likely be disrupted for brief bursts of time. Real-time audio has rather rigid requirements relating to reliability and low latency. In order to provide these, other means are required.
An often used technique is forward error correction where the transmitter sends additional data with the sound. By using some advanced algorithms, the receiver is able to fix the information that might partly be damaged by interfering transmitters. Subsequently, these products can broadcast 100% error-free even if there’s interference. Transmitters making use of FEC can transmit to a huge amount of wireless devices and does not require any feedback from the receiver.
One more technique uses receivers which transmit data packets to the transmitter. The information packets incorporate a checksum from which each receiver can decide if a packet was received correctly and acknowledge proper receipt to the transmitter. Considering that dropped packets will have to be resent, the transmitter and receivers need to hold information packets in a buffer. This will create an audio latency, also known as delay, to the transmission which may be a dilemma for real-time protocols like audio. Normally, the larger the buffer is, the larger the robustness of the transmission. Video applications, nevertheless, need the sound to be in sync with the movie. In cases like this a big latency is difficult. Products that integrate this particular procedure, nevertheless, are limited to transmitting to a few receivers and the receivers consume more energy.
To avoid crowded frequency channels, a few wireless speakers watch clear channels and may change to a clear channel as soon as the current channel becomes occupied by a different transmitter. This approach is also known as adaptive frequency hopping.
What Technology Use Today's Wireless Loudspeakers? 