Wireless audio is now widely used. A multitude of consumer products for instance wireless headphones are cutting the cord and also promise ultimate freedom of movement. I am about to look into how newest cordless systems can address interference from other transmitters and exactly how well they work in a real-world scenario.
The rising popularity of cordless consumer systems just like wireless headphones has started to cause difficulties with a number of gadgets competing for the constrained frequency space. Wireless networks, wireless phones , Bluetooth as well as other products are eating up the valuable frequency space at 900 MHz and 2.4 GHz. Cordless sound systems must ensure reliable real-time transmission in an environment which has a great deal of interference.
The most cost effective transmitters generally broadcast at 900 MHz. They work just like FM radios. Since the FM transmission uses a small bandwidth and therefore just consumes a small part of the free frequency space, interference is generally prevented by changing to a different channel. Digital audio transmission is generally utilized by more sophisticated sound systems. Digital transmitters generally operate at 2.4 Gigahertz or 5.8 Gigahertz. The signal bandwidth is higher than 900 MHz transmitters and thus competition in these frequency bands is high.
Frequency hopping devices, however, will still lead to further problems given that they are going to affect even transmitters working with transmit channels. Sound can be regarded as a real-time protocol. Consequently it has stringent requirements with regards to reliability. Furthermore, small latency is critical in most applications. As a result more sophisticated techniques are necessary to guarantee stability.
One approach is known as FEC or forward error correction. This technique will allow the receiver to repair a damaged signal. For this purpose, extra information is sent by the transmitter. Making use of a few innovative algorithms, the receiver may then repair the data that may partially be corrupted by interfering transmitters. Subsequently, these systems may transmit 100% error-free even when there is interference. Transmitters employing FEC on its own usually can broadcast to any number of cordless receivers. This approach is normally employed for systems where the receiver is not able to resend information to the transmitter or where the number of receivers is fairly large, like digital stereos, satellite receivers and so forth.
Yet another technique utilizes bidirectional transmission, i.e. every receiver sends information back to the transmitter. This strategy is only helpful if the number of receivers is small. It also needs a back channel to the transmitter. The data packets incorporate a checksum from which each receiver can decide if a packet was received properly and acknowledge correct receipt to the transmitter. In cases of dropped packets, the receiver will notify the transmitter and the dropped packet is resent. Therefore both the transmitter and also receiver have to have a buffer in order to keep packets. Making use of buffers leads to a delay or latency in the transmission. The amount of the delay is proportional to the buffer size. A bigger buffer size enhances the stability of the transmission. A large latency can be a problem for several applications nonetheless. Particularly when video is present, the sound should be synchronized with the movie. Additionally, in multi channel audio applications in which several speakers are wireless, the wireless loudspeakers should be synchronized with the corded loudspeakers. One constraint is that products in which the receiver communicates with the transmitter can usually merely broadcast to a few wireless receivers. Also, receivers must add a transmitter and usually consume additional current
So as to better handle interference, a number of wireless headphones is going to monitor the accessible frequency band as a way to decide which channels are clear at any given moment in time. If any specific channel becomes crowded by a competing transmitter, these devices can switch transmission to a clean channel without interruption of the audio. Because the transmitter lists clean channels, there is no delay in looking for a clear channel. It is simply chosen from the list. This method is often called adaptive frequency hopping spread spectrum.
The rising popularity of cordless consumer systems just like wireless headphones has started to cause difficulties with a number of gadgets competing for the constrained frequency space. Wireless networks, wireless phones , Bluetooth as well as other products are eating up the valuable frequency space at 900 MHz and 2.4 GHz. Cordless sound systems must ensure reliable real-time transmission in an environment which has a great deal of interference.
The most cost effective transmitters generally broadcast at 900 MHz. They work just like FM radios. Since the FM transmission uses a small bandwidth and therefore just consumes a small part of the free frequency space, interference is generally prevented by changing to a different channel. Digital audio transmission is generally utilized by more sophisticated sound systems. Digital transmitters generally operate at 2.4 Gigahertz or 5.8 Gigahertz. The signal bandwidth is higher than 900 MHz transmitters and thus competition in these frequency bands is high.
Frequency hopping devices, however, will still lead to further problems given that they are going to affect even transmitters working with transmit channels. Sound can be regarded as a real-time protocol. Consequently it has stringent requirements with regards to reliability. Furthermore, small latency is critical in most applications. As a result more sophisticated techniques are necessary to guarantee stability.
One approach is known as FEC or forward error correction. This technique will allow the receiver to repair a damaged signal. For this purpose, extra information is sent by the transmitter. Making use of a few innovative algorithms, the receiver may then repair the data that may partially be corrupted by interfering transmitters. Subsequently, these systems may transmit 100% error-free even when there is interference. Transmitters employing FEC on its own usually can broadcast to any number of cordless receivers. This approach is normally employed for systems where the receiver is not able to resend information to the transmitter or where the number of receivers is fairly large, like digital stereos, satellite receivers and so forth.
Yet another technique utilizes bidirectional transmission, i.e. every receiver sends information back to the transmitter. This strategy is only helpful if the number of receivers is small. It also needs a back channel to the transmitter. The data packets incorporate a checksum from which each receiver can decide if a packet was received properly and acknowledge correct receipt to the transmitter. In cases of dropped packets, the receiver will notify the transmitter and the dropped packet is resent. Therefore both the transmitter and also receiver have to have a buffer in order to keep packets. Making use of buffers leads to a delay or latency in the transmission. The amount of the delay is proportional to the buffer size. A bigger buffer size enhances the stability of the transmission. A large latency can be a problem for several applications nonetheless. Particularly when video is present, the sound should be synchronized with the movie. Additionally, in multi channel audio applications in which several speakers are wireless, the wireless loudspeakers should be synchronized with the corded loudspeakers. One constraint is that products in which the receiver communicates with the transmitter can usually merely broadcast to a few wireless receivers. Also, receivers must add a transmitter and usually consume additional current
So as to better handle interference, a number of wireless headphones is going to monitor the accessible frequency band as a way to decide which channels are clear at any given moment in time. If any specific channel becomes crowded by a competing transmitter, these devices can switch transmission to a clean channel without interruption of the audio. Because the transmitter lists clean channels, there is no delay in looking for a clear channel. It is simply chosen from the list. This method is often called adaptive frequency hopping spread spectrum.
About the Author:
Gunter Fellbaum has been developing audio and electronic products for over a decade. You can get additional details regarding wireless headphones from Amphony's website.
0 comments:
Post a Comment