What Type of Radio Frequency Transmissions Are Used by Bluetooth Devices?
Bluetooth low energy transmissions uses short-wavelength Radio Frequency (UHF) of a frequency range between 2.4 and 2.485 GHz unlicensed ISM frequency band. Bluetooth Devices use very little power below 10 milli-watts in most cases – sometimes as little as 0.5mW.
Bluetooth v5 and later does push the range out quite a bit though – and can get power up to 100 mW.
Bluetooth operates at frequencies between 2.402 and 2.480 GHz, or 2.400 and 2.4835 GHz including guard bands 2 MHz wide at the bottom end and 3.5 MHz wide at the top.
This is in the globally unlicensed (but not unregulated) industrial, scientific and medical (ISM) 2.4 GHz short-range radio frequency band. Bluetooth uses a radio technology called frequency-hopping spread spectrum.
Bluetooth divides transmitted data into packets, and transmits each packet on one of 79 designated Bluetooth channels.
Each channel has a bandwidth of 1 MHz. It usually performs 1600 hops per second, with adaptive frequency-hopping (AFH) enabled. Bluetooth Low Energy uses 2 MHz spacing, which accommodates 40 channels.
Bluetooth Low Energy technology operates in the same spectrum range (the 2.400–2.4835 GHz ISM band) as classic Bluetooth technology, but uses a different set of channels.
Instead of the classic Bluetooth 79 1-MHz channels, Bluetooth Low Energy has 40 2-MHz channels. Within a channel, data is transmitted using Gaussian frequency shift modulation, similar to classic Bluetooth’s Basic Rate scheme.
The bit rate is 1 Mbit/s (with an option of 2 Mbit/s in Bluetooth 5), and the maximum transmit power is 10 mW (100 mW in Bluetooth 5). Further details are given in Volume 6 Part A (Physical Layer Specification) of the Bluetooth Core Specification V4.0.
Bluetooth exists in numerous products such as telephones, speakers, tablets, media players, robotics systems, laptops, and console gaming equipment as well as some high definition headsets, modems, hearing aids and even watches.
Given the variety of devices which use the Bluetooth, coupled with the contemporary deprecation of headphone jacks by Apple, Google, and other companies, and the lack of regulation by the FCC, the technology is prone to interference.
Nonetheless Bluetooth is useful when transferring information between two or more devices that are near each other in low-bandwidth situations.
Bluetooth is commonly used to transfer sound data with telephones (i.e., with a Bluetooth headset) or byte data with hand-held computers (transferring files).
Bluetooth protocols simplify the discovery and setup of services between devices.
Bluetooth devices can advertise all of the services they provide. This makes using services easier, because more of the security, network address and permission configuration can be automated than with many other network types.
A personal computer that does not have embedded Bluetooth can use a Bluetooth adapter that enables the PC to communicate with Bluetooth devices.
While some desktop computers and most recent laptops come with a built-in Bluetooth radio, others require an external adapter, typically in the form of a small USB “dongle.”
Unlike its predecessor, IrDA, which requires a separate adapter for each device, Bluetooth lets multiple devices communicate with a computer over a single adapter.
What is the range of Bluetooth transmitter/receivers?
Bluetooth headsets are currently Class 2 Bluetooth devices with a range of approximately 10 meters, or roughly 30 feet.
What is the data throughput speed of a Bluetooth connection?
Bluetooth transfers data at a rate of 721 Kbps, which is from three to eight times the average speed of parallel and serial ports, respectively. This bandwidth is capable of transmitting voice, data, video and still images.
How secure is a Bluetooth network?
Bluetooth is extremely secure in that it employs several layers of data encryption and user authentication measures. Bluetooth devices use a combination of the Personal Identification Number (PIN) and a Bluetooth address to identify other Bluetooth devices.
Data encryption (i.e., 128-bit) can be used to further enhance the degree of Bluetooth security.
The transmission scheme (FHSS) provides another level of security in itself. Instead of transmitting over one frequency within the 2.4 GHz band, Bluetooth radios use a fast frequency-hopping spread spectrum (FHSS) technique, allowing only synchronized receivers to access the transmitted data.
How is Bluetooth used?
Bluetooth can be used to wirelessly synchronize and transfer data among devices. Bluetooth can be thought of as a cable replacement technology. Typical uses include automatically synchronizing contact and calendar information among desktop, notebook and palmtop computers without connecting cables.
Bluetooth can also be used to access a network or the Internet with a notebook computer by connecting wirelessly to a cellular phone.