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Once upon a time, I dreamed of having a mobile phone with Bluetooth function, but now Bluetooth has gone to every home, almost all smartphones have Bluetooth function, Bluetooth headset, Bluetooth keyboard, Bluetooth mouse, Bluetooth speaker, electronic devices without Bluetooth function do not feel like a modern device. So what exactly is Bluetooth? Why is this wireless technology called Bluetooth? What on earth can Bluetooth do? The radio frequency school will find out with you today.

The origin of Bluetooth the development of wireless technology is precisely to meet the needs of people for the unlimited development of wireless connection. Bluetooth technology as a wireless technology is no exception. In 1994, Ericsson set up a special research group whose main task was to develop a low-power, low-cost wireless connection technology for wireless connections to electronic devices such as cordless phones and headphones. With the deepening of research, researchers have increasingly discovered the great commercial application potential of this technology. Similar to today's wireless mobile communications technology, it is difficult to promote it by one company, so Ericsson researchers announced the technology and recruited a group of people from five multinational communications companies-- in addition to Ericsson in Sweden, Nokia in Finland, IBM and Intel in the United States, and Toshiba in Japan. People in the electronic field can see from the origin of this group that this organization is extraordinary. The hegemons in the field of mobile communications-- Ericsson, Nokia, IBM and Intel-- how could the technology tree of the 1980s and 1990s be less than that of Japan. The gang gave itself a name-SIG, the acronym is very high-end, but the whole spelling is Special Interest Group, special interest group, the goal of the gang is to develop Bluetooth, the popular point is to establish a global small-scale communication technology.

This special interest group has grown rapidly, from the Big five in 1998 to more than 2000 members in 2000, and even in 1999, the world's richest man Bill Gates visited a small workshop in Las Vegas that makes Bluetooth badges, and then Microsoft joined the group. Now almost all the electronic equipment companies have joined this special group. Interested students can check to see if your company is in the organization.

The success of Bluetooth technology is undoubtedly great, but why is the special wireless technology developed by this special interest group SIG called Bluetooth? Isn't white teeth more beautiful? This wireless technology clenches like a blue tooth, never breaking the line? Or there is something wrong with the aesthetics of foreigners!

This "Bluetooth" is not created by the rich imagination of foreigners. The name is in memory of a great king in ancient times-- Harald Bl å tand,Bl å tand. In English, it just means Bluetooth. It so happens that the king likes blueberries very much and does not like brushing his teeth, so people simply call him Blue Tooth King King Bluetooth. Fortunately, he didn't eat strawberries, or he would be the King of Red teeth, just like eating raw meat with his mouth open. The king's greatest contribution was the unification of ancient Denmark, Sweden and Norway, and the introduction of Christianity in places where Vikings prevailed, bringing the era of pirates to an end. So the Bluetooth King ranks 63rd among the 100 emperors who influence the world. And the Bluetooth King is articulate and sociable, unifying Norway, Sweden and Denmark in his lifetime, the same as the original intention of setting up a special interest group. So we named this wireless technology: Bluetooth Bluetooth. The initials of Harald Bl å tand are designed as Bluetooth logos.

The development of Bluetooth technology has developed for five generations since the first generation of Bluetooth technology was launched in 1998, so Bluetooth technology has also reached the 5G era. As shown in the following figure, the main feature is that the transmission rate is getting faster and faster, and the transmission distance is getting farther and farther. Of course, there are some minor upgrades between generations. For example, Bluetooth 1.1 and Bluetooth 1.2 were launched in 2002 and 2003 respectively, and the transmission rate increased from the original 723Kb / s to 1Mb / s. This is inseparable from the hard work of the engineers, of course, there is also the great contribution of our RF engineers.

The development of Bluetooth technology the following is the Bluetooth development chronology, so that everyone can more easily understand this technology. The latest launch should be Bluetooth voice technology-Bluetooth Audio. The demand is endless, the development of technology is endless, and I believe that the future of Bluetooth technology will become more and more powerful.

Characteristics of Bluetooth technology as a standard wireless communication system, Bluetooth also has its own unique communication protocol-Bluetooth protocol. Bluetooth protocol is developed and published by his standards group SIG. The following figure shows the structure of Bluetooth protocol, including application layer, data layer, logical link control and adaptation protocol, HCI host controller interface. LMP link management and the baseband and RF parts that we RF people are familiar with.

Bluetooth works in the ISM band that we are most familiar with, that is, 2.4GHz, with a bandwidth of 83.5MHz, which is shared by 2.4GHz-2.4835GHz, wifi, etc. So how to deal with the interference between them? Bluetooth uses the frequency hopping spread spectrum technology FHSS (Frequency-Hopping Spectrum Spred), which divides the frequency band into 79 FM channels separated by 1MHz. The signal of the Bluetooth device jumps from one channel to another in a pseudo-random way. From the surface, Bluetooth occupies the whole ISM band, but in fact only about 1MHz band is occupied, and the rate of FM is 1600 hops per second.

At the same time, in order to avoid potential interference, the standards organization proposes the wireless personal area network standard IEEE802.15 based on Bluetooth protocol to solve the problem of coexistence between Bluetooth and wireless network Wifi.

reference

1. Where did the name Bluetooth come from?

Https://www.zhihu.com/question/363418394/answer/953846245

2, https://www.zhihu.com/market/pub/120053325/manuscript/1289625216721985536

3, https://www.zhihu.com/market/pub/119967083/manuscript/1284013495869583360

4, https://baike.baidu.com/item/%E5%93%88%E6%8B%89%E5%B0%94%E8%93%9D%E7%89%99%E7%8E%8B/4386452

5, https://www.bluetooth.com/bluetooth-resources/?types=study-guide

This article is from the official account of Wechat: radio Frequency School (ID:RF_Center), author: RF Carpenter

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