An ever growing amount of cordless gadgets like wireless speakers produces increasing competition for the valuable frequency space. I am going to examine several technologies that are utilized by modern day electronic audio gadgets in order to discover how well these products may operate in a real-world environment.
The most popular frequency bands which are utilized by wireless devices include the 900 MHz, 2.4 GHz and 5.8 GHz frequency band. Mainly the 900 MHz as well as 2.4 GHz frequency bands have started to become clogged by the ever increasing amount of gadgets just like bluetooth outdoor loudspeakers, wireless telephones etc.
FM type sound transmitters are typically the least reliable with regards to tolerating interference because the transmission doesn’t have any procedure to cope with competing transmitters. Nonetheless, these transmitters use a relatively constrained bandwidth and changing channels can frequently avoid interference. Contemporary sound systems employ digital sound transmission and frequently work at 2.4 Gigahertz. Those digital transmitters send out a signal that takes up far more frequency space than 900 MHz transmitters and thus have a greater potential for colliding with other transmitters. Just changing channels, on the other hand, is no dependable solution for avoiding specific transmitters that use frequency hopping. Frequency hoppers including Bluetooth devices or numerous cordless telephones will hop through the full frequency spectrum. Hence transmission over channels is going to be disrupted for short bursts of time. For that reason modern audio transmitters use special mechanisms to deal with interfering transmitters to assure continuous interruption-free sound transmission. One of these techniques is referred to as forward error correction or FEC in short. The transmitter is going to broadcast additional information in addition to the sound data. From this added data, the receiver can easily recover the original information even when the signal was corrupted to a certain degree. FEC is unidirectional. The receiver will not send back any data to the transmitter. As a result it is usually used for products just like radio receivers in which the number of receivers is large.
Another method utilizes receivers that transmit data packets back to the transmitter. The data which is transmit includes a checksum. Using this checksum the receiver can detect whether any certain packet was received correctly and acknowledge. If a packet was corrupted, the receiver is going to alert the transmitter and ask for retransmission of the packet. As such, the transmitter needs to store a certain amount of packets in a buffer. Likewise, the receiver must have a data buffer. This buffer brings about an audio delay that depends on the buffer size with a larger buffer increasing the robustness of the transmission. A large latency can be a problem for many applications however. In particular when video is present, the audio should be in sync with the video. Additionally, in multichannel applications in which several loudspeakers are cordless, the cordless speakers ought to be synchronized with the corded speakers. Products that integrate this mechanism, nevertheless, are limited to transmitting to a small number of receivers and the receivers use up more power.
Often a frequency channel can get occupied by a different transmitter. Preferably the transmitter is going to recognize this fact and change to a different channel. To accomplish this, several wireless speakers consistently check which channels are available so that they can instantly change to a clean channel. Since the transmitter lists clear channels, there’s no delay in trying to find a clean channel. It’s simply chosen from the list. This method is frequently termed adaptive frequency hopping spread spectrum.
A Peek At The Most Modern Cordless Speakers 