Abstract: Wireless personal area networks (WPAN) are currently dominated by internal applications of self-contained networks. The problem of coexistence and integration with various networks such as cellular networks and the Internet still needs in-depth study. Multi-network integration will inevitably require more intelligent networks and terminals. Since the current WPAN technology is not yet mature, its practical application will face greater challenges, but it is also an opportunity. Once the related technical problems are solved, it may generate huge business opportunities. .
Keywords: Broadband wireless access; wireless metropolitan area network; wireless local area network; wireless personal area network
Editor's note
The demand for broadband, wireless, and personalization of global communications is driving the process of broadband for wireless access. Due to the development of portable products and the rapid growth of application requirements, the birth of wireless personal area network (WPAN) technology has been promoted, and the wireless access industry chain has become more complete. With the further formation of unified standards, WPAN is bound to usher in a period of full prosperity and become a new opportunity for operators to enter the access market.
The information industry is developing rapidly, and broadband access technologies are constantly emerging. Various broadband wireless access systems are favored by telecom operators due to their fast construction speed, low operating cost, and high return on investment. The current main technologies of broadband wireless access are: local multipoint distribution system (LMDS), multipoint multichannel distribution system (MMDS), wireless local area network (WLAN) and Bluetooth technology (Bluetooth), etc. Among them, LMDS and MMDS are wireless metropolitan area network (WMAN) technologies, and the IEEE 802.16 broadband wireless access standard working group is developing corresponding specifications to standardize these technologies; WLAN standards mainly refer to IEEE 802.11 series standards and HiperLAN / 2 standards; Bluetooth is currently Mainstream technology for wireless personal area network (WPAN) applications. Due to the diversification of consumer demand and applications, WMAN, WLAN and WPAN technologies will complement each other and jointly promote the development of the broadband wireless access market.
1 Broadband wireless access technology
1.1 Wireless Metropolitan Area Network
At present, broadband wireless access systems (such as LMDS and MMDS) that belong to WMAN applications lack uniform standards and are not compatible with each other. WMAN uses a variety of technologies, mainly orthogonal frequency division multiplexing (OFDM) technology, code division multiple access (CDMA) technology.
The IEEE 802.16 standard was developed to solve the aforementioned compatibility issues. The 2002 revision of the standard defines three main WMAN network types, namely: fixed, portable and mobile, which correspond to the standards IEEE 802.16, IEEE 802.16a and IEEE 802.16e, respectively. Among them, the IEEE 802.16 standard is suitable for line-of-sight transmission, and the operating frequency is 10 to 66 GHz, which is used in LMDS; the IEEE 802.16a standard is over-the-horizon transmission, and the operating frequency is 2 to 11 GHz, which is used in MMDS; 2 ～ 6 GHz, mainly used in cellular mobile communication and 3G.
At present, the focus of the 802.16 standard formulation work is on IEEE 802.16e. The goal is to maintain a certain degree of network roaming service when low-speed and light-weight mobile devices cross different access points.
WMAN's broadband wireless access business is rapidly expanding from North America and Europe to other parts of the world, providing new opportunities and prospects for telecom operators to broaden the network access market.
1.2 Wireless LAN
The IEEE 802.11 series of standards is the de facto standard for WLAN, including IEEE 802.11, IEEE 802.11a, IEEE 802.11b, and IEEE 802.11g. Among them, IEEE 802.11b transmission rate can be as high as 11 Mb / s, using 2.4 GHz unlicensed frequency band, has been widely used in offices, homes, hotels, airports and many other occasions, is currently the mainstream standard of WLAN; IEEE 802.11a is IEEE 802.11 The successor standard of b, the peak rate can reach 54 Mb / s, especially suitable for indoor and mobile environments, has a wider application prospect, and is optimistic about many manufacturers; IEEE 802.11g can achieve a maximum of 54 Mb / s in the 2.4 GHz band Data transmission maintains compatibility with IEEE 802.11b, and has solved the problem of mutual interference between devices using Bluetooth technology and the IEEE 802.11b standard.
HiperLAN / 2 is a high-performance wireless access standard developed by the Broadband Radio Access Network (BRAN) project team of the European Telecommunications Standardization Institute (ETSI). HiperLAN / 2 corresponds to the IEEE 802.11a standard and works in the 5 GHz frequency band. The modulation technology also uses orthogonal frequency division multiplexing (OFDM), which is compatible with IEEE 802.11a at the physical layer and uses a dynamic time division duplex technology with a data rate. It can be up to 54 Mb / s, and can support QoS at high throughput, thus providing support for real-time applications such as video and voice.
The four major telecommunications operators in China have all entered the WLAN field and jointly promoted the development of the WLAN market. In July 2002, the Ministry of Information Industry issued the "Notice on the Use of 5.8 GHz Band Frequency", approving the use of the 5 725 MHz to 5 850 MHz band
Used as a common frequency band for radio stations such as point-to-point or point-to-multipoint spread spectrum communication systems, high-speed wireless local area networks, broadband wireless access systems, Bluetooth technology equipment, and vehicle wireless automatic identification systems [1]. From a policy perspective, it opens up new space for the further application and promotion of WLAN in China.
1.3 Wireless personal area network
WPAN is a concept proposed after WMAN and WLAN. Its goal is to solve the problem of how to let people carry the network with them. The core is to solve the wireless multimedia transmission in small areas.
The IEEE 802.15 working group [2], established in 1999, is specifically responsible for formulating standards related to WPAN. The working group consists of four groups. Among them, IEEE 802.15.1 is responsible for the standardization of Bluetooth; IEEE 802.15.2 studies the inter-existence of WPAN and WLAN; IEEE 802.15.3 formulates high-speed WPAN standards; IEEE 802.15.4 studies special power-saving technologies and low-complexity solutions, application fields Mainly for sensors, remote control and home automation, etc.
The IEEE 802.15.1 standard is based on the Bluetooth v1.1 specification and defines the media access control (MAC) layer (including L2CAP, LMP, baseband) and physical layer of Bluetooth technology. IEEE 802.15.1 has been following the standard version upgrade work of the Bluetooth Special Interest Group to keep IEEE 802.15.1 synchronized with the Bluetooth standard. The Bluetooth Special Interest Group officially announced the Bluetooth standard v1.2 at the end of 2003.
IEEE 802.15.3 completed the MAC layer / physical layer standard formulation of high-speed WPAN in June 2003. The standard has the following characteristics: supports data rates up to 55 Mb / s, can transmit high-quality video and sound, supports service quality assurance, has Ad hoc point-to-point network characteristics, low power consumption and low cost.
IEEE 802.15.4 has passed the 18th round of draft amendments. The standard has the following characteristics: the data rate is 25, 40, 250 kb / s, and the CSMA-CA mechanism is used to ensure transmission reliability and provide optimal power management.
The Bluetooth technology that belongs to the WPAN application has become the current mainstream technology of WPAN due to its flexible, safe, low-cost, and low-power voice and data communication. Under the strong promotion of the Bluetooth Special Interest Group, Bluetooth technology is rapidly penetrating into the PC, consumer electronics and vertical application markets.
At present, Bluetooth is still regarded as the most promising WPAN technology by most people in the industry, and its degree of promotion and application marks the practicality of wireless personal area network.
Because of this, the China National Standardization Management Committee included Bluetooth technology in the national standard formulation plan for 2002-2003 in the "National Standards Committee [2002] No. 41", and authorized the Ministry of Information Industry Post and Telecommunications Industry Standardization Institute to preside over the drafting of this series of standards, reflecting The importance of Bluetooth technology in China. The China Bluetooth Standards Development Working Group has been paying close attention to the upgrade of Bluetooth standards in order to synchronize with international Bluetooth standards.
The transmission rate of Bluetooth restricts its application expansion and becomes the most important factor affecting the overall popularity of the technology. IEEE 802.15.3 has higher data rates, more comprehensive business and QoS support than Bluetooth, and shorter connection time. The characteristics have received widespread attention in the industry. However, although the formulation of the IEEE 802.15.3 standard has been completed, according to the person in charge of the IEEE 802.15 standard group, communication equipment using the IEEE 802.15.3 standard may not be launched until the end of 2004, and the chip price is estimated to be between 100 and 150 US dollars between.
2 Broadband WPAN access technology issues
Among the three complementary broadband access technologies, WMAN and WLAN are relatively mature and have begun to occupy the broadband wireless access market. Relative to WMAN and WLAN, WPAN is currently dominated by internal applications of its own network, its access technology is not yet perfect, and the application of wireless access has been slow to expand. China should seize this opportunity in a timely manner and strengthen its efforts to research and improve WPAN access technology.
2.1 WPAN network structure
Broadband WPAN is a typical Ad hoc network, and its working environment is sometimes very simple, but sometimes very complicated. The status of all devices in the network is equal, and a small area network can be formed at any time. Any device in broadband WPAN can form a network with similar devices in front, back, left, right, up, and down. Through "multi-hop", it can expand its application space and functions. The device has fixed, semi-fixed, small-scale mobile, In the case of large-scale movement, you need to consider handover. Therefore, the research of WPAN network structure is very important. Figure 1 is a schematic diagram of WPAN's network structure [3].
2.2 Integration of WPAN and cellular networks
When the access technology of WPAN and cellular network is solved, the application of WPAN in outdoor space will be very broad. The integration of WPAN and cellular networks can expand the capacity of the entire system, balance the traffic of adjacent cells, reduce the number of base stations, reduce the power consumption of mobile terminals, and expand new applications of cellular networks.
In a WPAN and cellular network fusion system structure, the base station coverage area is usually divided into three parts: the first part is a high-rate TDD area, and mobile terminals in the area can transmit data at a high rate; the second part is a low Rate TDD area, mobile terminals in this area can only transmit data at a lower rate; the third part is the area that the base station cannot cover, and the mobile terminals in this area cannot carry out data because they cannot receive the synchronization information sent by the base station Send. The mobile terminals in the three areas can communicate directly within a certain range based on the Ad hoc network protocol, or a distributed network composed of multiple piconets to achieve mutual communication.
3 Issues requiring in-depth research Aiming at the system structure of WPAN and cellular network multi-network integration, this paper believes that various adaptive algorithms with real-time optimization as the core content, broadband WLAN and WPAN wireless access technologies, and multi-network coexistence Network capacity and the optimization design of terminal equipment, it is essential to develop experimental systems and corresponding equipment. Specifically, the following topics should be studied in depth:
(1) Study the network structure of broadband WPAN, including WPAN spatial topology, key technologies of mobile self-organizing network, etc.
(2) Research key algorithms, including information rate adaptive algorithm, frequency hopping pattern and frequency hopping rate adaptive algorithm, link adaptive algorithm, frequency selection adaptive algorithm, etc.
(3) Research and development of broadband WPAN shared access protocol, including research on the overall structure of WPAN protocol, and research and development of several key software modules.
â‘·Develop an experimental demonstration system to verify the contents of research and development, and conduct research on multiple access methods, efficient modulation methods, radio frequency modules, multi-carrier transmission, etc. in the system.
(5) Research on the convergence technology of mobile ad hoc networks and cellular networks, focusing on random drive multiple access (ODMA) technology. As a supplement to the UMTS TDD mode, ODMA is used to provide higher data rates for mobile terminals at the edge of a cell in a TDD cellular network, so as to increase the range of high-rate data services. Combining ODMA and mobile self-organizing networks organically, complement each other and complement each other, can effectively expand the new application range of 3G systems.
(6) Study mobile self-organizing system based on TD-SCDMA. The system adopts ODMA multi-hop transmission technology and adaptive routing algorithm dedicated on-demand distance vector (AODV) routing protocol, which can provide a variety of new applications for 3G systems, and realize direct communication and multi-hop communication between mobile terminals and mobile terminals. , And can support seamless switching and roaming with existing 3G systems.
4 Conclusion Although the current broadband wireless access market is still in its infancy, the development of broadband wireless access technology is extremely rapid. Opportunities and challenges coexist. Relevant research departments in China should actively carry out research on related topics, generate China ’s independent intellectual property through research, contribute to the formation of China ’s broadband WPAN standard, or keep China ’s research in this field at least in sync with the international community. It is believed that as long as extensive and in-depth research is carried out in this field, the development of foreign industries is closely followed, and cooperation in various fields is strengthened, more broadband voice access will be gained internationally.
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