Wireless audio happens to be widely used. Many consumer products for instance wireless headphones are cutting the cable and also offer ultimate freedom of movement. Let me look at how most current wireless systems are able to deal with interference from other transmitters and just how well they will perform in a real-world situation.
The buzz of cordless devices like wireless headphones is mainly responsible for a rapid rise of transmitters that broadcast in the preferred frequency bands of 900 MHz, 2.4 Gigahertz as well as 5.8 GHz and therefore wireless interference has become a major concern.
The cheapest transmitters usually transmit at 900 MHz. They work just like FM stereos. Since the FM signal has a small bandwidth and thereby just uses up a small fraction of the free frequency space, interference can be avoided by changing to another channel. The 2.4 GHz and 5.8 Gigahertz frequency bands are used by digital transmitters and also are getting to be quite crowded of late as digital signals take up much more bandwidth than analog transmitters.
Only changing channels, however, is no reliable remedy for steering clear of certain transmitters which use frequency hopping. Frequency hoppers which include Bluetooth devices or many cordless phones will hop through the full frequency spectrum. Thus transmission over channels will be disrupted for brief bursts of time. For this reason contemporary sound transmitters incorporate special mechanisms to deal with interfering transmitters in order to ensure steady interruption-free sound transmission.
One of these methods is called forward error correction or FEC for short. The transmitter will transmit extra data in addition to the audio data. From this additional information, the receiver may restore the original information whether or not the signal was corrupted to a certain degree. Transmitters making use of FEC may broadcast to a huge amount of cordless devices and doesn't require any kind of feedback from the receiver.
In cases in which there is only a small number of receivers, commonly a different mechanism is utilized. The wireless receiver will send information packets to the transmitter to confirm proper receipt of information. The information that is transmit has a checksum. From this checksum the receiver can decide if any particular packet was received correctly and acknowledge. If a packet was corrupted, the receiver is going to inform the transmitter and ask for retransmission of the packet. Consequently, the transmitter needs to store a great amount of packets in a buffer. Likewise, the receiver will have to maintain a data buffer. This is going to introduce an audio latency, also called delay, to the transmission which can be an issue for real-time protocols including audio. Generally, the greater the buffer is, the larger the robustness of the transmission. Yet a big buffer can result in a large latency which could lead to issues with loudspeakers not being in sync with the movie. Products which incorporate this kind of mechanism, nevertheless, are limited to transmitting to a small number of receivers and the receivers consume more energy.
As a way to better handle interference, a number of wireless headphones is going to monitor the accessible frequency band so as to decide which channels are clear at any point in time. If any certain channel becomes crowded by a competing transmitter, these devices may switch transmission to a clean channel without interruption of the audio. This approach is also known as adaptive frequency hopping.
The buzz of cordless devices like wireless headphones is mainly responsible for a rapid rise of transmitters that broadcast in the preferred frequency bands of 900 MHz, 2.4 Gigahertz as well as 5.8 GHz and therefore wireless interference has become a major concern.
The cheapest transmitters usually transmit at 900 MHz. They work just like FM stereos. Since the FM signal has a small bandwidth and thereby just uses up a small fraction of the free frequency space, interference can be avoided by changing to another channel. The 2.4 GHz and 5.8 Gigahertz frequency bands are used by digital transmitters and also are getting to be quite crowded of late as digital signals take up much more bandwidth than analog transmitters.
Only changing channels, however, is no reliable remedy for steering clear of certain transmitters which use frequency hopping. Frequency hoppers which include Bluetooth devices or many cordless phones will hop through the full frequency spectrum. Thus transmission over channels will be disrupted for brief bursts of time. For this reason contemporary sound transmitters incorporate special mechanisms to deal with interfering transmitters in order to ensure steady interruption-free sound transmission.
One of these methods is called forward error correction or FEC for short. The transmitter will transmit extra data in addition to the audio data. From this additional information, the receiver may restore the original information whether or not the signal was corrupted to a certain degree. Transmitters making use of FEC may broadcast to a huge amount of cordless devices and doesn't require any kind of feedback from the receiver.
In cases in which there is only a small number of receivers, commonly a different mechanism is utilized. The wireless receiver will send information packets to the transmitter to confirm proper receipt of information. The information that is transmit has a checksum. From this checksum the receiver can decide if any particular packet was received correctly and acknowledge. If a packet was corrupted, the receiver is going to inform the transmitter and ask for retransmission of the packet. Consequently, the transmitter needs to store a great amount of packets in a buffer. Likewise, the receiver will have to maintain a data buffer. This is going to introduce an audio latency, also called delay, to the transmission which can be an issue for real-time protocols including audio. Generally, the greater the buffer is, the larger the robustness of the transmission. Yet a big buffer can result in a large latency which could lead to issues with loudspeakers not being in sync with the movie. Products which incorporate this kind of mechanism, nevertheless, are limited to transmitting to a small number of receivers and the receivers consume more energy.
As a way to better handle interference, a number of wireless headphones is going to monitor the accessible frequency band so as to decide which channels are clear at any point in time. If any certain channel becomes crowded by a competing transmitter, these devices may switch transmission to a clean channel without interruption of the audio. This approach is also known as adaptive frequency hopping.
About the Author:
Gunter Fellbaum has been developing audio and electronic products for over a decade. You can get further information regarding wireless headphones from Amphony's website.
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