I'll examine how present day sound transmission systems that are employed in the latest wireless headphones operate in real-world conditions having a large amount of interference from other cordless products.
The rising popularity of cordless consumer systems including wireless headphones has begun to result in issues with several products competing for the constrained frequency space. Wireless networks, wireless phones , Bluetooth as well as different devices are eating up the valuable frequency space at 900 MHz and 2.4 GHz. Wireless audio gadgets must guarantee reliable real-time transmission within an environment having a great deal of interference.
Conventional FM transmitters generally work at 900 MHz and don't possess any specific method of coping with interference nevertheless switching the transmit channel is a solution to deal with interfering transmitters. The 2.4 Gigahertz and 5.8 Gigahertz frequency bands are used by digital transmitters and also are getting to be pretty crowded lately given that digital signals take up much more bandwidth as compared to analogue transmitters.
Frequency hopping systems, however, are going to continue to cause problems because they will disrupt even transmitters working with transmit channels. Real-time audio has rather strict requirements relating to reliability and minimal latency. To be able to offer these, additional mechanisms will be required.
One of these approaches is known as forward error correction or FEC in short. The transmitter will broadcast additional data besides the sound data. From this supplemental data, the receiver can easily restore the original information even if the signal was damaged to a certain extent. FEC is unidirectional. The receiver will not send back any information to the transmitter. As a result it is usually used by equipment including radio receivers where the quantity of receivers is big.
An additional method makes use of receivers that transmit data packets back to the transmitter. The data which is transmit includes a checksum. Using this checksum the receiver may decide if any specific packet was received correctly and acknowledge. If a packet was damaged, the receiver is going to inform the transmitter and ask for retransmission of the packet. Consequently, the transmitter needs to store a certain amount of packets in a buffer. Equally, the receiver will have to have a data buffer. This will create an audio latency, also known as delay, to the transmission which may be a dilemma for real-time protocols like audio. Normally, the greater the buffer is, the greater the robustness of the transmission. Video applications, nevertheless, require the sound to be synchronized with the video. In this instance a large latency is difficult. One constraint is that systems in which the receiver communicates with the transmitter usually can just broadcast to a small number of cordless receivers. Additionally, receivers have to add a transmitter and usually consume additional current
In order to prevent congested frequency channels, a few wireless headphones keep an eye on clear channels and can switch to a clear channel once the existing channel becomes occupied by a different transmitter. This technique is also called adaptive frequency hopping.
The rising popularity of cordless consumer systems including wireless headphones has begun to result in issues with several products competing for the constrained frequency space. Wireless networks, wireless phones , Bluetooth as well as different devices are eating up the valuable frequency space at 900 MHz and 2.4 GHz. Wireless audio gadgets must guarantee reliable real-time transmission within an environment having a great deal of interference.
Conventional FM transmitters generally work at 900 MHz and don't possess any specific method of coping with interference nevertheless switching the transmit channel is a solution to deal with interfering transmitters. The 2.4 Gigahertz and 5.8 Gigahertz frequency bands are used by digital transmitters and also are getting to be pretty crowded lately given that digital signals take up much more bandwidth as compared to analogue transmitters.
Frequency hopping systems, however, are going to continue to cause problems because they will disrupt even transmitters working with transmit channels. Real-time audio has rather strict requirements relating to reliability and minimal latency. To be able to offer these, additional mechanisms will be required.
One of these approaches is known as forward error correction or FEC in short. The transmitter will broadcast additional data besides the sound data. From this supplemental data, the receiver can easily restore the original information even if the signal was damaged to a certain extent. FEC is unidirectional. The receiver will not send back any information to the transmitter. As a result it is usually used by equipment including radio receivers where the quantity of receivers is big.
An additional method makes use of receivers that transmit data packets back to the transmitter. The data which is transmit includes a checksum. Using this checksum the receiver may decide if any specific packet was received correctly and acknowledge. If a packet was damaged, the receiver is going to inform the transmitter and ask for retransmission of the packet. Consequently, the transmitter needs to store a certain amount of packets in a buffer. Equally, the receiver will have to have a data buffer. This will create an audio latency, also known as delay, to the transmission which may be a dilemma for real-time protocols like audio. Normally, the greater the buffer is, the greater the robustness of the transmission. Video applications, nevertheless, require the sound to be synchronized with the video. In this instance a large latency is difficult. One constraint is that systems in which the receiver communicates with the transmitter usually can just broadcast to a small number of cordless receivers. Additionally, receivers have to add a transmitter and usually consume additional current
In order to prevent congested frequency channels, a few wireless headphones keep an eye on clear channels and can switch to a clear channel once the existing channel becomes occupied by a different transmitter. This technique is also called adaptive frequency hopping.
About the Author:
Gunter Fellbaum has been developing audio and other electronic products for over a decade. You can get additional information about wireless headphones from Amphony's website.
