Sunday, February 23, 2014

Are Wireless Speakers Dependable In Real-World Situations?

By Mike Heller


I'll take a look at just how modern-day sound transmission technologies that are employed in the latest wireless speakers operate in real-world conditions with a great deal of interference from other cordless gadgets. The increasing rise in popularity of wireless consumer gadgets like wireless speakers has begun to result in problems with various products competing for the constrained frequency space. Wireless networks, cordless telephones , Bluetooth and also some other products are eating up the valuable frequency space at 900 MHz and 2.4 Gigahertz. Cordless sound products should assure reliable real-time transmission within an environment with a great deal of interference.

The most popular frequency bands that are used by cordless products are the 900 MHz, 2.4 GHz and 5.8 GHz frequency band. Primarily the 900 MHz as well as 2.4 Gigahertz frequency bands have begun to become clogged by the increasing quantity of gizmos including wireless speakers, wireless telephones and so on.

FM type sound transmitters are typically the least reliable in terms of tolerating interference considering that the transmission does not have any mechanism to cope with competing transmitters. Having said that, those transmitters have a fairly restricted bandwidth and changing channels can frequently steer clear of interference. Today's audio systems utilize digital audio transmission and in most cases operate at 2.4 GHz. Such digital transmitters broadcast a signal that takes up more frequency space than 900 MHz transmitters and therefore have a greater chance of colliding with other transmitters.

An often used strategy is forward error correction in which the transmitter sends extra information along with the sound. By using a few innovative calculations, the receiver can then fix the data which may partly be corrupted by interfering transmitters. As a result, these products can broadcast 100% error-free even if there exists interference. Transmitters employing FEC on its own typically may transmit to any number of cordless receivers. This mechanism is normally used in products in which the receiver cannot resend data to the transmitter or in which the quantity of receivers is pretty large, like digital radios, satellite receivers and so forth.

An additional technique makes use of receivers which transmit data packets back to the transmitter. The transmitters has a checksum with each data packet. Every receiver can easily decide if a certain packet has been acquired correctly or disrupted because of interference. Next, every cordless receiver sends an acknowledgement to the transmitter. Because dropped packets will need to be resent, the transmitter and receivers must hold data packets in a buffer. This kind of buffer will cause an audio delay which will depend on the buffer size with a bigger buffer improving the robustness of the transmission. However a big buffer can lead to a large latency which could result in problems with speakers not being in sync with the video. Products that incorporate this procedure, however, are limited to transmitting to a few receivers and the receivers use up more power.

In order to avoid congested frequency channels, a few wireless speakers watch clear channels and can change to a clean channel once the existing channel gets occupied by a different transmitter. Because the transmitter has a list of clean channels, there isn't any delay in trying to find a clear channel. It is simply picked from the list. This strategy is usually called adaptive frequency hopping spread spectrum.




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