An ever growing number of cordless systems which include wireless speakers causes increasing competition for the valuable frequency space. I am going to look at some technologies which are employed by today's electronic audio products in order to see how well these solutions can work in a real-world situation.
The growing interest in wireless consumer systems like wireless speakers has begun to result in problems with numerous products competing for the limited frequency space. Wireless networks, cordless telephones , Bluetooth and also some other products are eating up the precious frequency space at 900 MHz and 2.4 Gigahertz. Cordless sound gadgets need to assure reliable real-time transmission in an environment with a great deal of interference.
The most cost effective transmitters generally broadcast at 900 MHz. They work similar to FM stereos. Because the FM transmission has a small bandwidth and thus just consumes a tiny part of the free frequency space, interference is generally prevented simply by changing to an alternative channel. Modern audio systems use digital sound transmission and often operate at 2.4 GHz. These kinds of digital transmitters send out a signal which takes up more frequency space than 900 MHz transmitters and therefore have a greater potential for colliding with other transmitters.
One approach is referred to as FEC or forward error correction. This technique allows the receiver to correct a corrupted signal. For this purpose, additional information is sent by the transmitter. Using some sophisticated algorithms, the receiver can then restore the data that might partly be damaged by interfering transmitters. Subsequently, these products can easily transmit 100% error-free even if there is interference. Transmitters using FEC can transmit to a large number of cordless receivers and doesn't require any kind of feedback from the receiver.
One more technique utilizes bidirectional transmission, i.e. each receiver transmits information back to the transmitter. This approach is only helpful if the quantity of receivers is small. In addition, it needs a back channel to the transmitter. The data that is transmit has a checksum. Because of this checksum the receiver can easily see whether any specific packet was received correctly and acknowledge. As dropped packets will need to be resent, the transmitter and receivers must hold data packets in a buffer. This buffer will cause an audio delay which depends upon the buffer size with a larger buffer increasing the robustness of the transmission. Video applications, nevertheless, need the sound to be synchronized with the movie. In this instance a large latency is difficult. One limitation is that systems in which the receiver communicates with the transmitter usually can only transmit to a few cordless receivers. Additionally, receivers need to incorporate a transmitter and generally use up more current
In order to prevent crowded frequency channels, a few wireless speakers watch clear channels and can switch to a clean channel as soon as the current channel gets occupied by another transmitter. This technique is also referred to as adaptive frequency hopping.
The growing interest in wireless consumer systems like wireless speakers has begun to result in problems with numerous products competing for the limited frequency space. Wireless networks, cordless telephones , Bluetooth and also some other products are eating up the precious frequency space at 900 MHz and 2.4 Gigahertz. Cordless sound gadgets need to assure reliable real-time transmission in an environment with a great deal of interference.
The most cost effective transmitters generally broadcast at 900 MHz. They work similar to FM stereos. Because the FM transmission has a small bandwidth and thus just consumes a tiny part of the free frequency space, interference is generally prevented simply by changing to an alternative channel. Modern audio systems use digital sound transmission and often operate at 2.4 GHz. These kinds of digital transmitters send out a signal which takes up more frequency space than 900 MHz transmitters and therefore have a greater potential for colliding with other transmitters.
One approach is referred to as FEC or forward error correction. This technique allows the receiver to correct a corrupted signal. For this purpose, additional information is sent by the transmitter. Using some sophisticated algorithms, the receiver can then restore the data that might partly be damaged by interfering transmitters. Subsequently, these products can easily transmit 100% error-free even if there is interference. Transmitters using FEC can transmit to a large number of cordless receivers and doesn't require any kind of feedback from the receiver.
One more technique utilizes bidirectional transmission, i.e. each receiver transmits information back to the transmitter. This approach is only helpful if the quantity of receivers is small. In addition, it needs a back channel to the transmitter. The data that is transmit has a checksum. Because of this checksum the receiver can easily see whether any specific packet was received correctly and acknowledge. As dropped packets will need to be resent, the transmitter and receivers must hold data packets in a buffer. This buffer will cause an audio delay which depends upon the buffer size with a larger buffer increasing the robustness of the transmission. Video applications, nevertheless, need the sound to be synchronized with the movie. In this instance a large latency is difficult. One limitation is that systems in which the receiver communicates with the transmitter usually can only transmit to a few cordless receivers. Additionally, receivers need to incorporate a transmitter and generally use up more current
In order to prevent crowded frequency channels, a few wireless speakers watch clear channels and can switch to a clean channel as soon as the current channel gets occupied by another transmitter. This technique is also referred to as adaptive frequency hopping.
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