-Bluetooth Technology-
The name “Bluetooth” is derived from King Harald Bluetooth of Denmark, whose proponents hoped it would play a significant role in the information industry. In 1994, Ericsson initiated research aimed at solving the wireless communication issues between mobile phones and external devices, which later evolved into the concept of wireless communication. In May 1998, Ericsson, Nokia, IBM, Intel, and Toshiba announced the Bluetooth project as SIG founders. The technology essentially establishes a universal wireless interface and an open standard for control software, enabling cable-free interconnection of various portable devices over short distances. Its main applications include connecting peripheral devices to hosts via Bluetooth links, personal networking, information sharing, and secure wireless access to wide area networks from computers.
Components of the Bluetooth System
The functional modules in the Bluetooth system mainly consist of antenna unit, link control unit, link management unit, and software unit, making up four parts.
1. Antenna Unit
The antenna of the Bluetooth system is designed with a nominal output power of 0 dBm, complying with FCC requirements for the ISM band. By employing spread spectrum technology, the transmission power can reach 100 mW. The system’s maximum frequency hopping rate is 1600 hops/s, operating within the 2.4~2.48 GHz range, using 79 frequency points with a bandwidth of 1 MHz. The designed communication distance of the system is approximately 10 meters, and increasing the transmission power can extend this to 100 meters.
2. Link Control Unit
The link control unit mainly consists of three integrated chips: connection controller, baseband processor, and transceiver. The link control unit implements baseband protocols and other low-level connection procedures, supporting both synchronous connection-oriented (SCO) and asynchronous connectionless (ACL) modes.
3. Link Management Unit
The link management (LM) software module carries data devices, authentication, link hardware configuration, and other protocols. The link management unit can discover other remote link managers and communicate with them via the link management protocol (LMP). It primarily provides services such as sending and receiving data, requesting names, address queries, authentication, establishing connections, negotiating and establishing link modes, and determining frame types.
4. Software Unit
The link protocols can be divided into four layers: core protocol layer, cable replacement layer, telephone control protocol layer, and adopted other protocol layer. The main functions include configuration and diagnostics, discovery of Bluetooth devices, cable emulation, communication with peripheral devices, audio communication, and call control.
Characteristics of Bluetooth Technology
The characteristics of Bluetooth technology can be summarized as follows:
(1) Globally Applicable. Bluetooth operates in the 2.4 GHz ISM band, which is available in most countries worldwide, with the range being 2.4~2.4835 GHz. Using this band does not require a license from national radio resource management authorities.
(2) Simultaneous Transmission of Voice and Data. Bluetooth employs circuit switching and packet switching technologies, supporting three voice channels and asynchronous data channels, as well as channels that allow simultaneous transmission of asynchronous data and synchronous voice. Each voice channel has a data transmission rate of 64 kb/s, with voice signal encoding using pulse code modulation (PCM) or continuously variable slope delta modulation (CVSD). When using asymmetric channels for data transmission, the maximum rate is 721 kb/s, with a reverse rate of 57.6 kb/s; when using symmetric channels, the maximum rate is 342.6 kb/s. Bluetooth has two link types: asynchronous connectionless (ACL) link and synchronous connection-oriented (SCO) link.
(3) Temporary Peer-to-Peer Connections can be established. Based on the role of Bluetooth devices in the network, they can be classified as master and slave. The master device actively initiates connection requests, and when several Bluetooth devices connect to form a piconet, there is only one master device, while the others are slaves. A piconet is the most basic form of Bluetooth network, consisting of a point-to-point communication link between one master and one slave device.
(4) Good Interference Resistance. Many wireless devices operate in the ISM band, such as household microwaves and wireless local area networks (WLAN). To effectively resist interference from these devices, Bluetooth employs frequency hopping to spread the spectrum, dividing the 2.4~2.48 GHz band into 79 frequency points, with a 1 MHz interval between adjacent points. After sending data on one frequency point, Bluetooth devices jump to another frequency point, with the order of frequency points being pseudo-random, changing frequency 1600 times per second, with each frequency lasting for 625 ms.
(5) Compact Size and Easy Integration of Bluetooth Modules. Due to the small size of personal mobile devices, the Bluetooth modules embedded within them should be even smaller. For example, Ericsson’s Bluetooth module ROK101008 has dimensions of only 32.8 mm x 16.8 mm x 2.95 mm.
(6) Low Power Consumption. Bluetooth devices have four operational modes during communication connection: active mode, sniff mode, hold mode, and park mode. The active mode is the normal working state, while the other three modes are defined as low-power modes for energy saving.
(7) Open Interface Standards. To promote Bluetooth technology, SIG has made all Bluetooth technical standards public, allowing any organization or individual worldwide to develop Bluetooth products, as long as they pass SIG’s Bluetooth product compatibility testing before being marketed.
(8) Low Cost. With the expansion of market demand, various suppliers have launched their Bluetooth chips and modules, leading to a rapid decrease in the prices of Bluetooth products.
Finally, let’s ask everyone: which device in your life interacts with Bluetooth in a way that makes you feel “just right”? Feel free to share your “Bluetooth stories” in the comments!