Wireless audio is now widely used. A large number of consumer products for instance wireless speakers are eliminating the cable and also offer ultimate freedom of movement. I will analyze how newest cordless technology are able to address interference from other transmitters and how well they will function in a real-world situation.
The popularity of cordless gizmos including wireless speakers is mainly responsible for a rapid rise of transmitters which transmit in the preferred frequency bands of 900 MHz, 2.4 GHz and 5.8 GHz and thus cordless interference has become a serious issue.
Typical FM transmitters typically work at 900 MHz and do not have any particular method of dealing with interference yet switching the broadcast channel is a method to deal with interfering transmitters. Contemporary sound products employ digital sound transmission and in most cases function at 2.4 GHz. These digital transmitters send out a signal that takes up a lot more frequency space than 900 MHz transmitters and therefore have a greater chance of colliding with other transmitters.
One of these approaches is referred to as forward error correction or FEC for short. The transmitter is going to broadcast extra information in addition to the sound data. Making use of a number of innovative calculations, the receiver is able to restore the data that might partly be damaged by interfering transmitters. Consequently, these systems can transmit 100% error-free even if there is interference. Transmitters using FEC can transmit to a large number of wireless receivers and does not need any feedback from the receiver.
Yet another approach utilizes bidirectional transmission, i.e. each receiver transmits data back to the transmitter. This approach is only practical if the number of receivers is small. It also requires a back channel to the transmitter. The data packets include a checksum from which each receiver can see whether a packet was received properly and acknowledge proper receipt to the transmitter. If a packet was damaged, the receiver is going to notify the transmitter and ask for retransmission of the packet. Consequently, the transmitter needs to store a great amount of packets in a buffer. Equally, the receiver will need to have a data buffer. This buffer will cause an audio delay that will depend on the buffer size with a larger buffer increasing the robustness of the transmission. A large latency can generate problems for certain applications however. Especially if video exists, the audio tracks ought to be in sync with the movie. Furthermore, in surround sound applications where several speakers are cordless, the wireless loudspeakers should be in sync with the corded speakers. Cordless systems that use this technique, however, are only able to broadcast to a small quantity of cordless receivers. Generally the receivers have to be paired to the transmitter. Because each receiver also requires broadcast functionality, the receivers are more pricey to produce and also use up more energy.
Often a frequency channel can become occupied by a different transmitter. Ideally the transmitter can understand this fact and change to another channel. To do this, some wireless speakers consistently watch which channels are available to enable them to instantly switch to a clear channel. This method is also called adaptive frequency hopping.
The popularity of cordless gizmos including wireless speakers is mainly responsible for a rapid rise of transmitters which transmit in the preferred frequency bands of 900 MHz, 2.4 GHz and 5.8 GHz and thus cordless interference has become a serious issue.
Typical FM transmitters typically work at 900 MHz and do not have any particular method of dealing with interference yet switching the broadcast channel is a method to deal with interfering transmitters. Contemporary sound products employ digital sound transmission and in most cases function at 2.4 GHz. These digital transmitters send out a signal that takes up a lot more frequency space than 900 MHz transmitters and therefore have a greater chance of colliding with other transmitters.
One of these approaches is referred to as forward error correction or FEC for short. The transmitter is going to broadcast extra information in addition to the sound data. Making use of a number of innovative calculations, the receiver is able to restore the data that might partly be damaged by interfering transmitters. Consequently, these systems can transmit 100% error-free even if there is interference. Transmitters using FEC can transmit to a large number of wireless receivers and does not need any feedback from the receiver.
Yet another approach utilizes bidirectional transmission, i.e. each receiver transmits data back to the transmitter. This approach is only practical if the number of receivers is small. It also requires a back channel to the transmitter. The data packets include a checksum from which each receiver can see whether a packet was received properly and acknowledge proper receipt to the transmitter. If a packet was damaged, the receiver is going to notify the transmitter and ask for retransmission of the packet. Consequently, the transmitter needs to store a great amount of packets in a buffer. Equally, the receiver will need to have a data buffer. This buffer will cause an audio delay that will depend on the buffer size with a larger buffer increasing the robustness of the transmission. A large latency can generate problems for certain applications however. Especially if video exists, the audio tracks ought to be in sync with the movie. Furthermore, in surround sound applications where several speakers are cordless, the wireless loudspeakers should be in sync with the corded speakers. Cordless systems that use this technique, however, are only able to broadcast to a small quantity of cordless receivers. Generally the receivers have to be paired to the transmitter. Because each receiver also requires broadcast functionality, the receivers are more pricey to produce and also use up more energy.
Often a frequency channel can become occupied by a different transmitter. Ideally the transmitter can understand this fact and change to another channel. To do this, some wireless speakers consistently watch which channels are available to enable them to instantly switch to a clear channel. This method is also called adaptive frequency hopping.
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