Wireless audio is now widely used. Many consumer products including wireless speakers are cutting the cord and assure ultimate freedom of movement. Let me take a look at how most current wireless systems can cope with interference from other transmitters and exactly how well they function in a real-world scenario. The most common frequency bands that are employed by cordless gadgets are the 900 MHz, 2.4 Gigahertz and 5.8 GHz frequency band. Primarily the 900 MHz as well as 2.4 Gigahertz frequency bands have started to become clogged by the increasing quantity of gadgets such as wireless speakers, wireless phones and so forth.
Customary FM transmitters normally operate at 900 MHz and do not have any particular way of dealing with interference yet changing the transmit channel can be a method to cope with interfering transmitters. Advanced audio products use digital sound transmission and often function at 2.4 Gigahertz. Those 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.
Simply switching channels, on the other hand, is no dependable solution for steering clear of specific transmitters that use frequency hopping. Frequency hoppers such as Bluetooth products as well as quite a few wireless phones will hop through the full frequency spectrum. Thus transmission over channels will be disrupted for short bursts of time. Real-time audio has fairly rigid requirements with regards to stability and low latency. In order to offer those, other means are required.
One approach is called FEC or forward error correction. This method enables the receiver to fix a corrupted signal. For this purpose, supplemental information is sent from the transmitter. From this supplemental data, the receiver can easily recover the original information whether or not the signal was corrupted to some degree. Transmitters employing FEC on its own typically can transmit to any amount of wireless receivers. This approach is usually used for systems where the receiver cannot resend information to the transmitter or where the number of receivers is pretty large, just like digital radios, satellite receivers and so forth.
Another approach uses receivers which transmit data packets to the transmitter. The information which is transmit includes a checksum. Using this checksum the receiver can easily detect whether any specific packet was received correctly and acknowledge. In cases of dropped packets, the receiver is going to alert the transmitter and the dropped packet is resent. As such both the transmitter and also receiver require a buffer in order to store packets. This kind of buffer will cause an audio delay which is dependent upon the buffer size with a larger buffer improving the robustness of the transmission. Video applications, nevertheless, require the audio to be in sync with the video. In this instance a large latency is problematical. Products that integrate this particular procedure, however, are restricted to transmitting to a small number of receivers and the receivers consume more power.
As a way to better deal with interference, a number of outdoor wireless loudspeakers will monitor the available frequency band so as to determine which channels are clear at any time. If any specific channel becomes congested by a competing transmitter, these systems may change transmission to a clean channel without interruption of the audio. This technique is also known as adaptive frequency hopping.
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