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jeudi 20 mars 2014

Ways To Select The Most Dependable Wireless Speakers

By Mike Heller


I am going to investigate how modern day sound transmission systems which are employed in the latest wireless speakers work in real-world conditions with a great deal of interference from other cordless equipment.

FM type audio transmitters are usually the least robust in regards to tolerating interference since the transmission doesn't have any mechanism to deal with competing transmitters. Nonetheless, these kinds of transmitters have a rather restricted bandwidth and switching channels may often eliminate interference. Today's sound systems use digital audio transmission and often function at 2.4 Gigahertz. Those digital transmitters send out a signal that takes up far more frequency space than 900 MHz transmitters and thus have a greater possibility of colliding with other transmitters.

Customary FM transmitters typically operate at 900 MHz and don't have any particular way of coping with interference but switching the broadcast channel can be a approach to cope with interfering transmitters. Modern sound gadgets employ digital sound transmission and often function at 2.4 Gigahertz. Those digital transmitters broadcast a signal that takes up much more frequency space than 900 MHz transmitters and thus have a greater potential for colliding with other transmitters.

One of these approaches is known as forward error correction or FEC for short. The transmitter is going to transmit additional data besides the sound data. The receiver utilizes a formula which uses the additional data. When the signal is damaged during the transmission due to interference, the receiver can remove the incorrect information and restore the original signal. This method will work if the level of interference won't exceed a certain limit. FEC is unidirectional. The receiver does not send back any data to the transmitter. Thus it is usually employed for products similar to radio receivers in which the number of receivers is big.

One strategy is named FEC or forward error correction. This method enables the receiver to repair a damaged signal. For this purpose, supplemental information is sent from the transmitter. Using this added information, the receiver can restore the original information even if the signal was damaged to a certain extent. FEC is unidirectional. The receiver will not send back any kind of information to the transmitter. As a result it is often used for systems like radio receivers in which the quantity of receivers is big. Another approach utilizes bidirectional transmission, i.e. every receiver transmits information to the transmitter. This approach is only practical if the quantity of receivers is small. It also requires a back channel to the transmitter. The transmitters has a checksum with each information packet. Every receiver may determine whether a specific packet has been acquired correctly or disrupted as a result of interference. Then, each wireless receiver will send an acknowledgement to the transmitter. If a packet was corrupted, the receiver will alert the transmitter and request retransmission of the packet. Consequently, the transmitter needs to store a great amount of packets in a buffer. Equally, the receiver must have a data buffer. This kind of buffer causes an audio delay which is dependent upon the buffer size with a bigger buffer increasing the robustness of the transmission. Nonetheless a large buffer can lead to a large latency which could cause problems with loudspeakers not being synchronized with the video. Wireless products that use this method, however, can only broadcast to a limited number of cordless receivers. Usually the receivers have to be paired to the transmitter. Since each receiver also requires broadcast functionality, the receivers are more expensive to make and also use up more energy.

In order to avoid congested frequency channels, a few wireless speakers keep an eye on clear channels and can change to a clean channel once the current channel becomes occupied by another transmitter. This method is also referred to as adaptive frequency hopping.




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