There are just 3 primary frequency bands in which today’s cordless loudspeakers function: 900 MHz, 2.4 GHz and 5.8 GHz. As the number of cordless devices which function within these frequency bands has been growing continuously, these frequency bands have gotten more and more crowded to a degree at which products lead to noticeable degradation to the overall performance of similar devices. My goal is to show one of several methods which contemporary cordless loudspeakers use in order to withstand other cordless gadgets and also to lessen the impact on different gadgets.
Adaptive frequency hopping is a technique that provides a high level of robustness against interference for wireless speakers. It works by checking all of the channels inside the operating frequency band. It then decides which of the available channels are being used by other cord-less systems.
From all free frequency channels, several frequency channels are chosen and put together into a hop set. During the broadcast, each of the hop-set frequency channels are used. Every frequency channel is employed for a brief time period (also referred to as “burst”). After that period, the transmitter and receiver swap to the following hop-set channel. The cordless receiver similarly switches to the subsequent channel to ensure that the transmitter as well as receiver are constantly transmitting and receiving on the identical frequency channel. For the transmitter as well as receiver to be in sync, both transmitter and also receiver correspond the hop set with one another.
Aside from the current hop set, the transmitter keeps checking all accessible frequency channels and keeps a catalog of backup frequency channels. One of these back-up frequency channels is chosen in the event another transmitter commences making use of one of the current hop-set frequency channels in order to switch the hop-set channel that is now busy. The list of backup frequency channels allows for the transmitter to replace an occupied channel with a free frequency channel in a short amount of time. Therefore adaptive frequency hopping works well in avoiding transmission at filled frequency channels as well as in avoiding interference from other products.
In addition to the adaptive frequency hopping scheme, today’s cordless audio transmitters include more techniques to increase their quality of service (QoS). One of those methods is data buffering. Data buffering was created to handle loss or damage of packets because of inadequate receipt or perhaps multipath fading. Both the transmitter and cord-less receiver maintain a storage buffer that stores data packets. The transmitter adds a checksum (CRC) to every data packet and a number. Using the CRC, the receiver can determine whether a packet was damaged. The packet counter enables the receiver to determine whether any packets have been dropped. In each case, the receiver is going to ask for the missing or impaired packet to be resent by transmitting a signal to the transmitter. This operation requires a back channel along with time slots during which each receiver is able to ask for packets from the transmitter and thus this particular method supports a limited amount of wireless receivers per transmitter only.
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