I am going to examine just how present day sound transmission technologies which are employed in nowaday’s wireless speakers operate in real-world environments having a large amount of interference from other wireless gadgets.
The popularity of wireless gizmos just like wireless speakers is responsible for a quick increase of transmitters that transmit in the preferred frequency bands of 900 MHz, 2.4 Gigahertz as well as 5.8 Gigahertz and therefore cordless interference has become a serious problem.
FM type sound transmitters are generally the least reliable in terms of tolerating interference since the transmission does not have any procedure to deal with competing transmitters. Having said that, these types of transmitters have a relatively restricted bandwidth and changing channels may often eliminate interference. Advanced audio systems employ digital audio transmission and often work at 2.4 Gigahertz. These kinds of digital transmitters send out a signal that takes up a lot more frequency space than 900 MHz transmitters and thus have a greater potential for colliding with other transmitters. Simply switching channels, however, is no reliable remedy for steering clear of certain transmitters which use frequency hopping. Frequency hoppers which include Bluetooth gadgets as well as a lot of wireless phones are going to hop through the entire frequency spectrum. As a consequence transmission on channels is going to be disrupted for brief bursts of time. Audio can be regarded as a real-time protocol. Consequently it has strict requirements concerning reliability. In addition, small latency is vital in many applications. As a result more advanced methods are needed to assure dependability.
One of these strategies is referred to as forward error correction or FEC in short. The transmitter will broadcast additional information in addition to the audio data. Because of this added information, the receiver can easily recover the original data even when the signal was damaged to some extent. FEC is unidirectional. The receiver won’t send back any information to the transmitter. Thus it is often used by equipment including radio receivers in which the number of receivers is big.
In cases in which there is merely a small number of receivers, commonly yet another method is used. The wireless receiver sends information packets back to the transmitter to confirm proper receipt of data. The information which is transmit has a checksum. Using this checksum the receiver can see whether any particular packet was received correctly and acknowledge. If a packet was corrupted, the receiver will inform the transmitter and request retransmission of the packet. As a result, the transmitter needs to store a certain amount of packets in a buffer. Likewise, the receiver must maintain a data buffer. This buffer brings about an audio delay that depends on the buffer size with a larger buffer increasing the robustness of the transmission. A large latency can generate problems for several applications nonetheless. Particularly when video is present, the sound must be synchronized with the movie. Furthermore, in multichannel applications in which some loudspeakers are cordless, the wireless loudspeakers ought to be synchronized with the corded loudspeakers. One limitation is that systems in which the receiver communicates with the transmitter usually can only transmit to a few wireless receivers. Additionally, receivers must incorporate a transmitter and generally consume additional current So as to better cope with interference, several wireless speakers will monitor the available frequency band as a way to decide which channels are clear at any given point in time. If any specific channel becomes crowded by a competing transmitter, these devices may switch transmission to a clean channel without interruption of the audio. The clean channel is picked from a list of channels that was determined to be clear. One technology which employs this particular transmission protocol is called adaptive frequency hopping spread spectrum or AFHSS