Analysis of bluetooth key technologies and experience in product development

1 Analysis of the Origin and Development Background of Bluetooth Technology
Since the end of the last century, the information industry has maintained a rapid development momentum, especially communication and computer technology, which has penetrated into all walks of life and every corner of people's lives. The development of the Internet makes people seem unwilling to leave the "network" for a moment. People expect to be able to carry the network with them, that is, to use a cheap wireless method to achieve multimedia transmission anytime and anywhere, which makes broadband wireless communication a new hot spot. However, due to the non-renewable nature of frequency resources, broadband and large capacity have become a pair of major contradictions. Any solution that can effectively solve this contradiction at a low cost will arouse great interest among people. Small-scale applications are representative, and typical achievements include: IEEE 802.11 and HiperLAN with wireless LAN (Local Area Network) as typical applications; the "Shared Wireless Access Protocol" (SWAP) proposed by the "Home Radio Frequency Working Group" (HRFWG) with home applications as the main background; the "Bluetooth Special Interest Group" (BSIG) initiated by Ericsson and other companies. Most of these systems use frequency hopping technology and work in the frequency bands above 2.4 GHz or 5 GHz. Although their standards are still being revised, they have shown strong vitality. The world's top communication companies, computer companies and software companies are working together to tackle key problems, and are also competing fiercely.
From the perspective of network, after the Wide Area Network (WAN) or Metropolitan Area Network (MAN) and Local Area Network (LAN), people have proposed the "Wireless Personal Area Network" (WPAN). This new concept has attracted much attention. The IEEE 802.15, which was established in 1999, now has four working groups dedicated to studying related protocols and coordinating the coexistence of existing standards and WPAN.
In comparison, the Bluetooth system is more representative. It is developing according to the concept of WPAN and complements the concept of WPAN, becoming a prototype of WPAN. In fact, WPAN and its small-scale applications have huge market potential. It complements and supplements the applications in large-scale and fast-moving situations, and is of great significance to the development of the national economy and the improvement of people's living standards. In a sense, the market potential of the former may be greater, because this application can establish information transmission between various mobile communication devices, fixed communication devices, computers and their terminal devices, various digital data systems and even various household appliances in a small range using cheap wireless methods. The equipment involved is wide and large, and it is easy to form a new economic growth point. Its rapid development is inevitable. 2 Bluetooth technology Analysis of characteristics and key technologies In general, Bluetooth has the following characteristics. · Works in the 2.4GHz ISM (Industrial Scientific Medical) band. Most countries use 79 channels, with a carrier frequency of 2402+kMHz (k = 0,1,…,78) and a channel spacing of 1MHz. · The maximum transmit power is divided into three levels: 100mW (20dBm), 2.5mW (4dBm) and 1mW (0dBm). Power control is required within the range of 4 to 20dBm. · The modulation method is GFSK with BT = 0.5, and the modulation index is 0.28 to 0.35. · The symbol rate is 1Mbit/s. · Channels are divided according to 625μs per time slot; TDD is used for full-duplex communication. · Information on the channel is sent in the form of data packets; it supports circuit switching and packet switching, supports multiple asynchronous data channels or up to 3 concurrent synchronous voice channels, or channels that transmit a synchronous voice and one or more asynchronous data at the same time. · Each voice channel supports 64 kbit/s synchronous voice; the asynchronous channel supports asymmetric connections of up to 921 kbit/s and 57.6 kbit/s for the reverse channel, or 432 kbit/s for symmetrical connections. It can be seen that Bluetooth uses a hybrid multiple access method of CDMA and TDMA, and the frequency hopping, TDD and GFSK modulation methods make its radio frequency circuit relatively simple. Most of the content of the communication protocol can be implemented with dedicated integrated circuits and software, which technically guarantees the high performance and low cost of its equipment. Therefore, Bluetooth will have the characteristics of simple equipment, small size, low price and stable operation. However, so far, Bluetooth has no interference avoidance mechanism, and the anti-interference ability and potential of frequency hopping have not been brought into play; the rate of 1 Mbps still has many disadvantages in multimedia applications. These two major problems have attracted attention from all parties. 3 Wide application The basic starting point of Bluetooth is to enable its equipment to be used for any small-scale communication on a global scale. According to the communication protocol, various Bluetooth devices can find other Bluetooth devices through manual or automatic query no matter where they are, thus forming a network and realizing various functions provided by the system. At present, the Bluetooth standard provides the following applications: general access, service discovery protocol, cordless phone, intercom system, serial port, headset, dial-up network, fax, LAN access, general object exchange, object push, file transfer and synchronization application. It can be seen that Bluetooth can add new functions to existing networks such as cellular mobile phone systems, cordless communication systems, wireless LANs and the Internet, and add wireless transmission and networking functions to various computers, fax machines, printers and even various indoor electronic, information and electrical equipment. The application space is extremely broad. According to our experience, Bluetooth products will be quickly integrated with the following equipment or systems: various telephone systems, vehicle-mounted communication equipment, wireless cables and WLANs, wireless briefcases, various digital electronic devices, e-commerce, information appliances, industrial control, intelligent buildings, various special occasions, etc. 4 Development of Bluetooth Products The State Key Laboratory of Mobile Communications of Southeast University has been tracking Bluetooth technology since 1998. It is one of the earliest units in China to participate in SIG and a member unit of TF9 of SIG China Working Group.















In 1999, the State Key Laboratory of Mobile Communications of Southeast University signed a cooperation agreement on "Development of System Software for ASIC Solutions of Bluetooth Systems" with the "Communication Technology Center Co., Ltd." wholly owned by the Hong Kong government, and jointly completed the "ASIC Solutions for Bluetooth Systems" project of the Innovation and Technology Fund (ITF) of the Hong Kong Special Administrative Region Government. By April 2001, the development of two versions of the protocol stack had been completed. In June 2001, the results were appraised by the Jiangsu Provincial Department of Science and Technology, and the SIG certification is currently being sought. In 2000, the Jiangsu Provincial Department of Science and Technology gave strong support to the research and development of Bluetooth products. The State Key Laboratory of Mobile Communications undertook the "CDMA Wireless Access System", a key scientific and technological research project of Jiangsu Province during the "15th Five-Year Plan", and developed Bluetooth products such as PSTN gateways, LAN access equipment and related terminal equipment. The work is progressing smoothly. Since April 2001, the laboratory has also served as a technical support unit of China Electronics Equipment Shenzhen Company and has carried out multi-faceted cooperation with it. Currently, the two parties are working on the project of "Development of Bluetooth System Demonstration and Development Platform Based on Ericsson Bluetooth Module". In addition, since the end of 1999, we have also undertaken the key scientific and technological research project of the Ministry of Education, "Research on key technologies of frequency-hopping multimedia communication in complex environments"; in 2000, the project "Research on key technologies of broadband high-speed frequency-hopping system under WPAN environment" was funded by the National Natural Science Foundation; since February 2001, we have cooperated with Motorola China Software Center to carry out the project "Research on key algorithms of HiperLAN/2". These projects have enabled us to master the basic theories of Bluetooth system, wireless LAN and wireless personal area network, and have conducted in-depth research on several algorithms around real-time optimization problems, which will play a positive role in the next step of development.
The following is a brief introduction to the development of Bluetooth PSTN gateway and LAN access point equipment.
The Bluetooth telephone gateway is a key device of the cordless telephone model (Cordless Telephone Profile) defined in the application model, and its schematic diagram is shown in Figure 1.

The Bluetooth LAN access point is the key device of the LAN access model (LAN Access Profile) in the Bluetooth application model, and its schematic diagram is shown in Figure 2. It enables Bluetooth terminals to access the Internet wirelessly anytime and anywhere, eliminating the trouble of connecting to the network cable.
For the above two applications, we have developed a model prototype and will launch a practical product as soon as possible. 5 Conclusion Bluetooth is a recently proposed small-scale information transmission system that has shown strong vitality. Bluetooth technology and its development direction will have a significant impact on the national economy and will become one of the widely used mainstream technologies. The State Key Laboratory of Mobile Communications of Southeast University and some sister colleges, scientific research institutions and enterprises have been tracking and studying it for a long time, and have put forward their own views and developed some products, which are basically at the same level as international counterparts. The market of China's information industry is huge, and the application prospects of Bluetooth and its related technologies are broad. The conditions for vigorously promoting the application research of Bluetooth technology in China are ripe. Therefore, under the guidance of the government, more and more Bluetooth products will be developed through the integration of industry, academia and research and by making enterprises the protagonists as soon as possible. Innovative applications are the lifeline for the development of Bluetooth and subsequent products.