Wireless audio is becoming popular. Numerous consumer products including wireless speakers are eliminating the cable and assure ultimate freedom of movement. I am about to investigate how newest wireless technology can cope with interference from other transmitters and exactly how well they will perform in a real-world scenario.
The most popular frequency bands which might be used by cordless products include the 900 MHz, 2.4 Gigahertz and 5.8 Gigahertz frequency band. Usually the 900 MHz and also 2.4 Gigahertz frequency bands have begun to become crowded by the ever increasing number of devices just like speakers for outdoors, wireless telephones etc.
Typical FM transmitters generally operate at 900 MHz and don’t possess any particular method of coping with interference yet changing the transmit channel is a method to deal with interfering transmitters. The 2.4 Gigahertz and 5.8 Gigahertz frequency bands are used by digital transmitters and also have become very crowded of late given that digital signals take up more bandwidth than analogue transmitters.
Frequency hopping products, nonetheless, are going to still cause problems because they will affect even transmitters using transmit channels. Audio can be regarded as a real-time protocol. Therefore it has stringent demands with regards to reliability. Furthermore, small latency is important in numerous applications. For this reason more sophisticated methods are required to ensure reliability.
One of these techniques is known as forward error correction or FEC in short. The transmitter is going to broadcast additional data in addition to the audio data. The receiver uses an algorithm that utilizes the additional information. In the event the signal is corrupted during the transmission due to interference, the receiver may remove the erroneous information and recover the original signal. This technique will work if the level of interference won’t exceed a certain threshold. FEC is unidirectional. The receiver doesn’t send back any data to the transmitter. Thus it is often used for systems such as radio receivers where the quantity of receivers is large.
In cases in which there is just a small number of receivers, often a further mechanism is utilized. The cordless receiver sends data packets back to the transmitter in order to confirm proper receipt of information. The transmitters contains a checksum with each information packet. Each receiver may decide if a particular packet has been received correctly or damaged as a result of interference. Next, each cordless receiver will send an acknowledgement to the transmitter. In cases of dropped packets, the receiver is going to notify the transmitter and the dropped packet is resent. Consequently both the transmitter as well as receiver require a buffer to store packets. This buffer brings about an audio delay which is dependent upon the buffer size with a larger buffer improving the robustness of the transmission. A big latency can be a problem for certain applications nonetheless. Particularly if video is present, the sound ought to be synchronized with the movie. Also, in multichannel applications where some loudspeakers are cordless, the cordless speakers ought to be in sync with the corded loudspeakers. Systems that integrate this particular procedure, however, are limited to transmitting to a small number of receivers and the receivers use up more power.
As a way to better cope with interference, a number of wireless speakers will monitor the available frequency band in order to determine which channels are clear at any given moment in time. If any specific channel becomes crowded by a competing transmitter, these systems may change transmission to a clean channel without interruption of the audio. Since the transmitter lists clear channels, there’s no delay in trying to find a clean channel. It’s simply picked from the list. This technique is usually termed adaptive frequency hopping spread spectrum.
Are Today's Wireless Speakers Dependable Enough? 