Wireless audio has become widely used. A multitude of consumer products which include Sony wireless speakers are eliminating the cable and promise greatest freedom of movement. Let me examine how most up-to-date cordless technology are able to cope with interference from other transmitters and just how well they will function in a real-world scenario.
The most popular frequency bands which can be used by wireless gadgets include the 900 MHz, 2.4 GHz and 5.8 GHz frequency band. Mostly the 900 MHz and 2.4 Gigahertz frequency bands have begun to become clogged by the increasing number of gadgets just like wireless speakers, cordless telephones and so forth.
Conventional FM transmitters usually operate at 900 MHz and don’t have any particular way of coping with interference yet switching the broadcast channel can be a solution to deal with interfering transmitters. Digital audio transmission is usually employed by more sophisticated sound gadgets. Digital transmitters commonly function at 2.4 Gigahertz or 5.8 GHz. The signal bandwidth is higher than 900 MHz transmitters and thus competition in these frequency bands is high.
Frequency hopping devices, however, will still create problems because they are going to disrupt even transmitters using transmit channels. Sound can be regarded as a real-time protocol. Because of this it has stringent needs concerning reliability. Furthermore, low latency is critical in most applications. Consequently more advanced techniques are required to ensure stability.
A regularly used technique is forward error correction in which the transmitter sends additional data with the sound. The receiver makes use of a formula which uses the additional data. In the event the signal is corrupted during the transmission resulting from interference, the receiver can easily remove the incorrect data and restore the original signal. This technique works if the level of interference won’t rise above a certain limit. Transmitters making use of FEC may transmit to a multitude of wireless devices and does not require any feedback from the receiver. A different technique uses receivers which transmit data packets back to the transmitter. The information packets include a checksum from which each receiver can determine whether a packet was received correctly and acknowledge correct receipt to the transmitter. In cases of dropped packets, the receiver is going to alert the transmitter and the lost packet is resent. Because of this both the transmitter and receiver require a buffer to store packets. Making use of buffers causes a delay or latency in the transmission. The amount of the delay is proportional to the buffer size. A bigger buffer size improves the stability of the transmission. A big latency can generate problems for many applications nonetheless. Particularly when video is present, the audio tracks must be synchronized with the movie. Additionally, in multichannel applications in which a number of loudspeakers are cordless, the cordless loudspeakers ought to be synchronized with the corded loudspeakers. One constraint is that systems where the receiver communicates with the transmitter usually can merely transmit to a few wireless receivers. Additionally, receivers have to add a transmitter and usually consume more current
In order to avoid congested frequency channels, several wireless speakers keep an eye on clear channels and can change to a clear channel once the current channel gets occupied by another transmitter. Since the transmitter has a list of clear channels, there is no delay in looking for a clear channel. It is simply picked from the list. This technique is often named adaptive frequency hopping spread spectrum.