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With the development of communication technology to this day, revolutionary changes often do not occur at the technical level, but rather rapidly promote mature technologies to all areas of society, bringing huge impacts to the entire social life.

  The Revolutionary Event of WiMAX Broadband Access   Origin of
  
  WiMAX On
  
  June 9, John Antone, Vice President and General Manager of Intel Asia Pacific, announced that the company had signed a memorandum of understanding with the Dalian and Chengdu municipal governments to deploy the latest WiMAX broadband wireless technology in the above cities. According to the memorandum, the network facilities set up in Chengdu and Dalian will fully enable the latest WiMAX broadband wireless technology, thus providing a new wireless solution for the "last mile" problem of broadband access for enterprises and families.

  In fact, wireless microwave communications have existed for many years before the emergence of WiMAX, from the earliest microwave trunk lines used for television signal transmission to later line backups and even C-band satellite communications. In recent years, China Unicom has launched LMDS wireless access services working in the 26G frequency band, as well as 3.5G frequency band fixed wireless access services that have been launched through bidding in some cities since 2001. Microwave wireless communications are no longer a new technology.

  However, since the establishment of WiMAX by world-renowned suppliers including Nokia and Intel in 2001, WiMAX has received great attention from the industry. It has even been selected as one of the top ten most important technologies in the future. Many people even place high hopes on WiMAX with an optimistic attitude of replacing 3G.

  WiMAX (World Interoperability for Microwave Access) is the full name of global microwave access interoperability, and is a wireless metropolitan area network technology based on the IEEE802.16 standard. Although microwave communications have been used in various fields before the formal establishment of the WiMAX organization, due to the incompatibility of various equipment, there is no authoritative organization to formulate unified protocol standards and certify various equipment. In addition, the management of wireless spectrum in various countries around the world is not completely consistent. The solutions provided by each equipment manufacturer are highly specialized, and the application field and scope are limited, resulting in high equipment costs. The WiMAX organization began to formulate standards and certify chips and equipment in 2001. Economies of scale made it possible to reduce costs, and the application field of WiMAX also expanded accordingly.

  According to statistics, by 2002, there were 2,400 ISPs (Internet access service providers) in the United States serving more than 6,000 wireless access markets. However, due to the lack of unified standards, the equipment of each supplier was expensive and could not be interconnected, which brought a great burden to users. The emergence of WiMAX can solve this problem.

  Now the WiMAX organization includes chip manufacturers (such as Intel), equipment suppliers (such as Alcatel), and telecom operators (such as BT British Telecom), and the industry chain is already very complete. At present, there are many experimental networks in the world. Equipment that meets the WiMAX standard can be submitted for commercial use as early as the fourth quarter of this year. Large-scale application will begin in 2005. Intel plans to launch the Centrino chipset with integrated mobile WiMAX chips in 2006. Refer to the experience of WiFi. The large-scale application of WiMAX is not far away.

  
  
  Faster, farther, cheaper
  
  The outstanding feature of WiMAX technology is that it has a longer coverage radius than WiFi. WiFi mainly solves the problem of wireless access within 100 meters and belongs to the category of WLAN (wireless local area network). WiFi can reach up to 300 meters in open areas, and the effective coverage range is generally within 100 meters indoors. WiMAX can cover up to 50 kilometers, which belongs to the category of wireless metropolitan area network (WMAN). Its typical application coverage is 6-10 kilometers. Compared with 3G, which provides less than 2M bandwidth, each WiMAX base station can be divided into 6 sectors at most, each sector can provide 70M independent bandwidth, and the coverage of the base station is 10 times that of 3G base stations. Therefore, some people believe that WiMAX will replace 3G and become the mainstream technology of the next generation of communication.

  However, this view is too optimistic. WiMAX is based on the 802.16 protocol. In the early 802.16 standard, the working frequency band is 11-60G, and it cannot provide non-line-of-sight connection. The so-called line-of-sight connection means that there must be no obstruction between the communication base station and the client, and there must be a channel through which light (or line of sight) can pass directly. This is mainly due to the characteristics of microwave communication. The ability of high-frequency signals to bypass obstacles is very limited, and it is also affected by weather. For example, rain usually causes signal failure and reduced communication quality. At the same time, the 802.16 protocol is designed based on fixed wireless access technology and cannot meet the needs of mobility. 3G is a technical solution for wide-area mobile communications, which is incomparable to 802.16 in terms of mobility and the ability of signals to bypass obstacles.

  On this basis, the WiMAX organization developed 802.16a, which works at a lower frequency band than 802.16, mainly working in the frequency band range of 2-11G. The ability of signals to bypass obstacles has been improved. It can now support non-line-of-sight transmission, which means that there can be trees or buildings blocking the base station and the client, and the application field of WiMAX has been broadened.

  In response to the problem that 802.16a does not have mobility performance, WiMAX has formulated the 802.16e standard on this basis. According to the 802.16e standard, the wireless connection will not be interrupted when walking with a PDA or using a mobile computing device. Therefore, WiMAX has mobility performance. However, products that meet this standard will not be officially put into commercial use until 2006.

  According to the forecast of analysis agencies, due to the unification of WiMAX standards, economies of scale for base stations and clients can be achieved. By 2005, the price of each WiMAX chipset is expected to be around US$25, and the construction cost of each base station will be controlled below US$20,000. Looking back at the rapid decline in WiFi client prices from thousands of yuan to hundreds of yuan, economies of scale will be the most competitive advantage of WiMAX. Conservative calculations show that a base station has four sectors, each sector provides 50M bandwidth, and the coverage range is 10 kilometers. Each customer is provided with 512K independent bandwidth. A base station can serve 400 customers at the same time, and each customer shares the cost of the base station at US$50. The initial investment cost pressure on operators is not great. In addition, WiMAX has good adaptability to terrain. In areas with low customer density, the cost is much lower than that of optical fiber or twisted pair. WiMAX will have strong competitiveness in the field of broadband access.

  
  
  Flexible networking
  
  The typical networking mode of WiMAX is shown in the figure. In this solution, WiMAX is mainly used in the following areas:

  1. Cellular backhaul. When deploying a wireless access network in a larger area, wireless links between WiMAX base stations can be used to extend the network coverage.

  2. WiFi hotspot backhaul. As shown in Figure 2, WiFi hotspots are deployed in an area. The long-distance link between the hotspot and the Internet is completed by WiMAX, which extends the scope of use of the hotspot.

  3. Community broadband. For some places that are difficult to cover by DSL or Cable access, WiMAX can be considered as an alternative. In comparison, WiMAX is less affected by distance and community density. For some temporary gathering places, such as exhibitions, WiMAX has a short deployment cycle and is more flexible than DSL or Cable access.

  4. Economically underdeveloped areas or places that need protection. Economically underdeveloped areas may not have pre-deployed twisted pair or coaxial cables. Rewiring is restricted by user density and is not economical. For cultural relics such as the Forbidden City, rewiring is even more impossible. WiMAX becomes a good choice.

  5. Best wireless connection mode. For users who have deployed WiFi at home, they may temporarily move out of the WiFi coverage. At this time, 802.16e, as an extension of 802.16a, can ensure smooth roaming of mobile users in WiFi and WiMAX networks. In this way, the client can automatically choose to use WiFi or WiMAX, ensuring the best connection mode.

  Among the above networking modes, WiMAX supports data, voice and video. WiMAX's unique quality of service guarantee (QoS), bandwidth allocation on demand, adaptive parameter adjustment and other features bring greater flexibility to networking.

  For example, in voice and video services, they are very sensitive to delays, but not so sensitive to errors, while data services are just the opposite, insensitive to delays but very sensitive to errors. WiMAX can provide different levels of service quality guarantee according to different upper-layer applications to improve network throughput capacity.

  Business users may need wider bandwidth, while home users may not need very high bandwidth. Video on demand requires a smaller uplink bandwidth and a very high downlink bandwidth. WiMAX can flexibly configure to meet these needs. WiMAX can also automatically adapt to the distance and communication speed. For example, it can adjust the signal modulation method to meet the distance requirements and reduce the speed to ensure communication.

  Spectrum twists and turns However, just when Intel was fully promoting WiMAX, Nokia, the world's largest mobile phone supplier, the most important 3G equipment supplier, and one of the initiators of WiMAX, announced its withdrawal from WiMAX (the latest news is that Nokia has announced its rejoining of the WiMAX organization). Some analysts in the industry believe that Nokia's withdrawal actually reflects the spectrum problem of WiMAX. Although 802.16 for line-of-sight transmission and 802.16a for non-line-of-sight transmission work in the 11-60G frequency band and 2-11G frequency band respectively, the frequency resources appear to be very rich. However, the management of radio frequencies in various countries is not unified, and too many applications are stuffed into the above frequency bands: microwave radar, navigation, remote sensing testing, satellite communications, WiFi, etc. At the same time, for some frequency bands that do not require a license, anyone can use it. This is like being in a public meeting room, everyone can speak loudly, but whether they can be heard is another matter. Nokia's withdrawal actually confirmed this concern. The frequency bands that have been licensed face competition, and the frequency bands that do not need licenses face difficult-to-solve interference problems. It is not easy for WiMAX to adapt to the spectrum issues of various countries.

  But things are not as pessimistic as they seem. The technical appeal of WiMAX is enough to change this situation. Intel began lobbying in April this year. Intel's reason is that since radio frequencies can now be used for more interesting things, why can't they be changed?

  In 2003, at the Third China Broadband Wireless Technology Conference, Xie Feibo, deputy director of the State Radio Administration, introduced that the International Telecommunication Union has added frequencies for wireless fixed and mobile services in the 5G frequency band, so that 600M frequencies in the 5G frequency band can be used for wireless mobile and fixed communications. This has actually begun to provide sufficient frequency resources for WiMAX broadband wireless access applications.

  In the 3.5G frequency band, China has launched bidding since June 2001 and February 2003, and has carried out wireless access attempts in several cities.

  What is more interesting is that various analysis reports on market forecasts for WiMAX have regarded China as a very important market. One of the analysis materials even called China the world's largest broadband wireless access market.

  The report analyzed that China has invested hundreds of millions of dollars in ADSL since 2001, and the number of users accessing the Internet through ADSL has increased from 1 million to 10 million. China licensed two frequency bands of 3.5G to five cities in 2000, and to 32 cities in 2003. Soon, more than 300 cities in China will get this license.

  The report also listed the possible business areas in China, including telephone, Internet teahouse, medical insurance network, enterprise telephone exchange relay line, enterprise network access, bank dedicated network and high-speed mobile Internet business.

  At present, it seems that there is no force that can stop the application of WiMAX. The only suspense is what to do with WiMAX. A few years ago, there was a survey on the bottleneck of broadband network application. There were many different opinions, but later facts proved that all applications, industrial environment and consumer awareness were not a problem. When broadband becomes as cheap as cabbage, all problems are not a problem.

  The revolutionary nature of WiMAX is not in other things, but in being cheaper. Cheapness is something that even God cannot stop.
This post is from RF/Wirelessly
 

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