Bluetooth (English: Bluetooth), an open communication technical standard for wireless data and voice communication. It is a special short-distance wireless technology connection based on low-cost short-distance wireless connection, which establishes a communication environment for fixed and mobile devices. It is widely used in telecommunications, computers, networks, consumer electronics and other fields. Bluetooth enables today's portable mobile devices and computer devices to connect to the Internet without cables, and can access the Internet wirelessly. The frequency band of Bluetooth is 2400-2483.5MHz (including protection band). This is a short-range radio band of 2.4GHz in the industrial, scientific and medical (ISM) band, which is not licensed (but not unregulated) all over the world. Using Bluetooth frequency hopping technology, the transmitted data is divided into data packets and transmitted through 79 designated Bluetooth channels respectively. The bandwidth of each channel is 1MHz. Bluetooth 4.0 uses an interval of 2MHz and can accommodate 40 channels. The first channel starts at 2402MHz, and there is a channel from 1MHz to 2480MHz. It has adaptive frequency hopping (AFH) function, and usually hops 1600 times per second.
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