I am going to examine just how modern day audio transmission technologies that are utilised in today’s wireless speakers operate in real-world situations having a large amount of interference from other wireless gadgets.
The increasing rise in popularity of wireless consumer products like wireless speakers has begun to cause problems with a number of products competing for the constrained frequency space. Wireless networks, wireless phones , Bluetooth as well as different devices are eating up the valuable frequency space at 900 MHz and 2.4 GHz. Cordless sound gadgets need to assure robust real-time transmission in an environment having a great deal of interference.
FM type sound transmitters are generally the least robust with regards to tolerating interference because the transmission doesn’t have any mechanism to cope with competing transmitters. On the other hand, these transmitters use a fairly restricted bandwidth and changing channels can often avoid interference. The 2.4 GHz and 5.8 Gigahertz frequency bands are utilized by digital transmitters and also are getting to be very congested lately as digital signals occupy a lot more bandwidth as compared to analog transmitters.
Merely changing channels, however, is no dependable remedy for steering clear of specific transmitters which use frequency hopping. Frequency hoppers like Bluetooth systems as well as several cordless phones are going to hop throughout the whole frequency spectrum. Hence transmission on channels is going to be disrupted for short bursts of time. Real-time audio has fairly rigid demands pertaining to reliability and low latency. In order to provide those, different mechanisms are needed.
One of these approaches is referred to as forward error correction or FEC for short. The transmitter will transmit additional information in addition to the audio data. By using a number of advanced calculations, the receiver may then fix the information that might partially be damaged by interfering transmitters. Because of this, these systems may transmit 100% error-free even if there exists interference. Transmitters using FEC can broadcast to a large number of wireless receivers and does not require any feedback from the receiver. A different strategy employs bidirectional transmission, i.e. every receiver sends information back to the transmitter. This method is only useful if the quantity of receivers is small. In addition, it requires a back channel to the transmitter. The transmitters contains a checksum with every data packet. Each receiver can easily decide if a certain packet was received properly or disrupted as a result of interference. Subsequently, each wireless receiver will be sending an acknowledgement to the transmitter. Considering that dropped packets will have to be resent, the transmitter and receivers need to store information packets in a buffer. This kind of buffer will cause an audio delay which will depend on the buffer size with a larger buffer improving the robustness of the transmission. Yet a large buffer will result in a large latency that may lead to difficulties with speakers not being in sync with the video. Cordless systems that use this method, however, can only broadcast to a limited quantity of wireless receivers. Normally the receivers have to be paired to the transmitter. As each receiver also requires broadcast functionality, the receivers are more expensive to fabricate and in addition consume more energy. In order to better overcome interference, a number of cordless outdoor speakers is going to monitor the available frequency band in order to determine which channels are clear at any given moment in time. If any certain channel gets crowded by a competing transmitter, these systems can change transmission to a clean channel without interruption of the audio. The clear channel is chosen from a list of channels that was identified to be clean. One technology that makes use of this kind of transmission protocol is referred to as adaptive frequency hopping spread spectrum or AFHSS
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