Thursday, March 20, 2014

Methods To Select The Most Dependable Wireless Speakers

By Mike Heller

I am going to investigate just how modern-day audio transmission systems that are utilised in the latest wireless speakers work in real-world conditions having a large amount of interference from other wireless gadgets.

Conventional FM transmitters typically operate at 900 MHz and do not possess any particular way of dealing with interference nevertheless changing the transmit channel can be a strategy to cope with interfering transmitters. The 2.4 GHz and 5.8 Gigahertz frequency bands are utilized by digital transmitters and also are becoming rather crowded recently as digital signals take up a lot more bandwidth as compared to analog transmitters.

Typical FM transmitters normally operate at 900 MHz and don't possess any specific method of dealing with interference yet switching the transmit channel is a method to cope with interfering transmitters. The 2.4 Gigahertz and 5.8 Gigahertz frequency bands are used by digital transmitters and also are becoming pretty crowded these days since digital signals take up more bandwidth as compared to analogue transmitters.

An often employed technique is forward error correction where the transmitter transmits additional data with the sound. The receiver uses a formula which utilizes the additional data. If the signal is corrupted during the transmission as a result of interference, the receiver can filter out the erroneous data and restore the original signal. This method will work if the amount of interference won't rise above a certain threshold. FEC is unidirectional. The receiver will not send back any kind of data to the transmitter. As a result it is frequently used by systems just like radio receivers where the number of receivers is large.

Yet another strategy utilizes bidirectional transmission, i.e. every receiver transmits data back to the transmitter. This approach is only helpful if the quantity of receivers is small. Additionally, it requires a back channel to the transmitter. The data which is transmit has a checksum. Because of this checksum the receiver may see whether any certain packet was received properly and acknowledge. If a packet was corrupted, the receiver is going to inform the transmitter and ask for retransmission of the packet. As a result, the transmitter must store a certain amount of packets in a buffer. Likewise, the receiver must have a data buffer. This buffer brings about an audio delay which will depend on the buffer size with a larger buffer increasing the robustness of the transmission. Yet a big buffer will lead to a large latency which could cause issues with loudspeakers not being in sync with the movie. Systems that integrate this kind of procedure, nevertheless, are restricted to transmitting to a few receivers and the receivers consume more energy.

In order to steer clear of crowded frequency channels, several wireless speakers watch clear channels and can change to a clean channel once the current channel gets occupied by another transmitter. The clear channel is chosen from a list of channels which has been determined to be clean. A modern technology which makes use of this kind of transmission protocol is called adaptive frequency hopping spread spectrum or AFHSS

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