Bluetooth, or Bluetooth, is a new wireless transmission protocol, which was first created by Ericsson, and then the technical standard was formulated by the Bluetooth Special Interest Group. It is said that because this technology is still in its infancy, Bluetooth has registered its Chinese translation in Taiwan Province Province, but according to the literal translation of English itself, Bluetooth is more suitable.
history
Bluetooth technology was originally invented by Ericsson. 1On May 20th, 999, industry leaders such as Sony Ericsson, IBM, Intel, Nokia, Toshiba, etc. set up Bluetooth special interest groups and formulated Bluetooth technical standards. The name "Bluetooth" comes from the nickname of Danish King harald in 10 century. Harald, who came from a pirate family, unified the divided countries in Northern Europe and became the king of the Viking Kingdom. Because he likes eating blueberries, his teeth are often dyed blue, so he got the nickname "Bluetooth". At that time, blueberries were considered unfit for eating because of their peculiar colors, so the king who loves to taste new things became a symbol of innovation and courage to try. 1998, Ericsson hoped that the wireless communication technology could be unified and named it "Bluetooth".
Recent development
A PDA mobile phone that communicates with wireless headphones through Bluetooth interface is currently on the market. All products are in the format of 1. 1 It is a low-power radio equipment, which uses a low-cost microprocessor chip to send and receive information in a short distance (10 to 100 meters).
Bluetooth is used for wireless connection between different devices, such as connecting computers and peripheral devices, such as printers and keyboards, or allowing personal digital assistants (PDA) to communicate with other PDA or computers nearby. At present, there are many mobile phones with Bluetooth technology on the market, which can be connected to computers, PDA and even hands-free headphones.
In fact, according to the established standards, Bluetooth can support more powerful long-distance communication and form a wireless local area network. Each Bluetooth device can keep 7 connections at the same time. Each device can be configured to constantly announce its presence to nearby devices in order to establish a connection. In addition, the connection between two devices can also be password protected to prevent it from being received by other devices.
The standard of Bluetooth is IEEE 802. 15, and the Bluetooth protocol works at 2.45GHz of unlicensed ISM band. The highest speed can reach 723.1kb/s. In order to avoid interference, other protocols of 2.45GHz may be used. Bluetooth protocol divides the frequency band into 79 channels, which can be changed at most 1600 times per second.
It is not appropriate to compare Bluetooth with WiFi, because WiFi is a faster and wider coverage protocol. Although they use the same frequency range, they also need more expensive hardware. Bluetooth should be used to create wireless connections between different devices, and WiFi is a wireless LAN protocol. They have different purposes.
Future development
The Bluetooth Special Interest Group is developing versions 1.2 and 2.0.
1.2 version
This version is backward compatible with 1. 1, and its main improvements include:
Anonymity: Mask the hardware address (BD_ADDR) of the device to protect users from identity sniffing attacks and tracking. Hardware anonymity has been realized since 1. 1 version, but it has not been realized yet, so ordinary consumers still don't have it.
AFH, Adaptive Frequency Hopping (AFH): By avoiding the use of crowded frequencies in frequency hopping sequences, the resistance to radio interference can be improved.
Higher actual transmission speed
L2CAP layer introduces flow control and error correction mechanism.
Version 2.0
There is no clear information about the content of version 2.0, but Ericsson researchers have published some contents:
Added "non-hopping narrowband channel".
Because there is no need to exchange reply signals with each device, this channel can be used to broadcast the Bluetooth service summaries of various devices to a large number of Bluetooth devices at the same time. The answer signal exchange process currently takes about one second.
Unencrypted information such as real-time public transport timetable, basic traffic information and advance traffic direction indication can be sent to the equipment at high speed.
Higher connection speed
Support multiple speed levels
Early bluetooth
The earlier versions of 1.0 and 1.0B had many problems, and many manufacturers pointed out that their products were incompatible with each other. At the same time, in the process of "shaking hands" between two devices, the address of Bluetooth hardware (BD_ADDR) will be transmitted, which can not be anonymous at the protocol level, causing the danger of data leakage and deterring some users.