Tuesday 18 February 2014

Are Wireless Speakers Dependable In Real-World Situations?

By Mike Heller


An ever expanding number of wireless products such as wireless speakers is causing increasing competition for the precious frequency space. I'm going to check out a number of technologies which are employed by modern digital audio products in order to see how well these solutions may work in a real-world situation.

Customary FM transmitters typically work at 900 MHz and do not have any certain means of dealing with interference yet changing the broadcast channel is a way to deal with interfering transmitters. The 2.4 GHz and 5.8 Gigahertz frequency bands are used by digital transmitters and also are getting to be rather crowded of late as digital signals take up much more bandwidth than analog transmitters.

A few wireless systems such as Bluetooth gadgets as well as wireless phones incorporate frequency hopping. Consequently just switching the channel isn't going to prevent these frequency hoppers. Real-time audio has fairly strict demands with regards to dependability and minimal latency. In order to provide those, different mechanisms will be required.

A frequently utilized technique is forward error correction where the transmitter transmits additional information with the sound. Making use of several advanced calculations, the receiver can then restore the information which may partly be corrupted by interfering transmitters. As a result, these products may broadcast 100% error-free even if there's interference. Transmitters making use of FEC may transmit to a large number of wireless devices and doesn't require any kind of feedback from the receiver.

Yet another method makes use of receivers which transmit information packets to the transmitter. The information packets have a checksum from which each receiver may see whether a packet was received correctly and acknowledge proper receipt to the transmitter. If a packet was damaged, the receiver will inform the transmitter and request retransmission of the packet. Consequently, the transmitter needs to store a great amount of packets in a buffer. Likewise, the receiver will need to maintain a data buffer. This kind of buffer brings about an audio delay that is dependent upon the buffer size with a larger buffer improving the robustness of the transmission. A big latency can generate problems for several applications however. In particular when video is present, the audio ought to be synchronized with the video. Additionally, in multichannel audio applications in which a number of loudspeakers are cordless, the wireless speakers ought to be in sync with the corded speakers. One constraint is that systems where the receiver communicates with the transmitter usually can merely transmit to a few cordless receivers. Furthermore, receivers have to add a transmitter and usually use up more current

In order to better handle interference, a number of wireless speakers will monitor the accessible frequency band as a way to determine which channels are clear at any given time. If any specific channel becomes congested by a competing transmitter, these products may change transmission to a clean channel without interruption of the audio. This method is also called adaptive frequency hopping.




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