Wireless audio is becoming popular. A large number of consumer products which include bluetooth outdoor loudspeakers are eliminating the cord plus offer ultimate freedom of movement. Let me investigate how latest cordless technology are able to address interference from other transmitters and how well they will perform in a real-world situation.
The increasing rise in popularity of wireless consumer gadgets just like wireless speakers has started to result in problems with various devices competing for the limited frequency space. Wireless networks, wireless telephones , Bluetooth and different products are eating up the precious frequency space at 900 MHz and 2.4 Gigahertz. Cordless sound gadgets must assure robust real-time transmission in an environment having a large amount of interference. FM type audio transmitters are usually the least robust with regards to tolerating interference considering that the transmission does not have any procedure to cope with competing transmitters. On the other hand, those transmitters possess a rather limited bandwidth and switching channels may avoid interference. The 2.4 Gigahertz and 5.8 GHz frequency bands are utilized by digital transmitters and also are becoming rather congested of late since digital signals occupy a lot more bandwidth compared to analog transmitters.
Frequency hopping gadgets, nonetheless, will continue to cause problems since they are going to disrupt even transmitters employing transmit channels. Audio can be viewed as a real-time protocol. As such it has strict demands pertaining to stability. Also, low latency is essential in most applications. Consequently more sophisticated techniques are required to guarantee stability. An often used technique is forward error correction in which the transmitter transmits additional information with the audio. Using some sophisticated algorithms, the receiver can then restore the information that may partly be damaged by interfering transmitters. Because of this, these systems may broadcast 100% error-free even if there is interference. Transmitters making use of FEC can transmit to a huge amount of wireless receivers and does not require any kind of feedback from the receiver.
An additional method utilizes bidirectional transmission, i.e. each receiver transmits information to the transmitter. This strategy is only useful if the quantity of receivers is small. Additionally, it needs a back channel to the transmitter. The information packets incorporate a checksum from which every receiver can easily determine if a packet was received correctly and acknowledge proper receipt to the transmitter. Considering that lost packets must be resent, the transmitter and receivers must hold data packets in a buffer. This will create an audio latency, also referred to as delay, to the transmission that could be a problem for real-time protocols including audio. Typically, the bigger the buffer is, the greater the robustness of the transmission. Video applications, however, require the sound to be in sync with the video. In such cases a big latency is problematic. Wireless products which incorporate this method, however, are only able to transmit to a limited quantity of wireless receivers. Commonly the receivers have to be paired to the transmitter. Because each receiver also requires broadcast functionality, the receivers cost more to produce and in addition consume more power.
In an effort to better cope with interference, some wireless speakers will monitor the accessible frequency band in order to decide which channels are clear at any given time. If any particular channel becomes crowded by a competing transmitter, these systems may change transmission to a clean channel without interruption of the audio. This technique is also called adaptive frequency hopping.
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