Brief information: WiMAX wireless broadband connection technology

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Brief information: WiMAX wireless broadband connection technology [Copy link]

WiMAX

The main members of the WiMAX (Worldwide Interoperability for Microwave Access) Microwave Access Global Interoperability Certification Industry Alliance include equipment manufacturers, device suppliers, operators, etc. Its main task is to eliminate the barriers to the application of the IEEE802.16 standard and expand the scope of application of the standard by certifying the compatibility and interoperability of products. 802.16 is an air interface standard for wireless access technology developed by IEEE802. Representative standards include 802.16d fixed wireless access and 802.16e mobile wireless access standards. According to the current technological development, 802.16d is mainly positioned for enterprise users, providing a means of long-distance transmission, while the user group of 802.16e is positioned for individual users, supporting users to access the network with broadband while on the move.

　　WiMAX is an emerging technology that can provide "last mile" broadband connectivity over a wider geographical area than Wi-Fi, thereby supporting enterprise customers to enjoy T1-class services and residential users to have access capabilities equivalent to cable/DSL. With its coverage range of 1 to 6 miles at any location (depending on a variety of factors), WiMAX will provide better mobility for high-speed data applications. In addition, with this coverage and high throughput, WiMAX can also provide backhaul for telecommunications infrastructure, enterprise campuses and Wi-Fi hotspots.

　　WiMAX will be deployed in three phases. The first phase will deploy WiMAX technology using the IEEE802.16d specification through indoor antennas, targeting known subscribers in fixed locations. The second phase will deploy indoor antennas in large numbers, broadening the appeal of WiMAX technology to operators seeking to simplify user point installation. The third phase will introduce the IEEE802.16e specification, in which WiMAX certified hardware will be used in portable solutions for users who want to roam within the service area, supporting connectivity similar to today's Wi-Fi capabilities, but with more persistent and robust connectivity.

　　The primary challenge facing WiMAX is still its construction cost and equipment price. At present, the cost of each user of MMDS multi-point multi-channel distributed system, including WiMAX antenna deployment, is as high as about 3,000 US dollars. This not only makes it difficult for operators to obtain sufficient return on investment, but also makes users daunted and shy away. Moreover, after several rounds of program updates and technological innovations, various types of equipment have achieved quite good cost-effectiveness in China's 3.5GHz frequency band, which is a very limited resource. If WiMAX participates in the competition at similar prices, it will face severe challenges. In addition, WiMAX, Wi-Fi and 3G will coexist in a complementary manner for a long time, and will compete with each other to a certain extent in the overlapping areas. Therefore, maintaining effective interconnection between these system applications and enhancing their own competitiveness are also important tasks facing WiMAX.

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WiMAX vs. 3G

　　3G is an ITU specification that supports high-speed wireless communications. This worldwide wireless connection is compatible with GSM, TDMA and CDMA. The next generation of 3G cellular services can provide a long-range wireless access range for voice and data. Operators around the world are currently deploying 3G network infrastructure in towns, suburbs and rural areas with heavy traffic. The next generation of 3G cellular services can create a wide range of data access across a variety of geographies, providing the best mobile computing capabilities for voice communications and Internet connections.

　　IEEE802.16e has been attracting much attention since it was proposed. Especially with the promotion of industry giants such as Intel and WiMAX organizations, the industry has launched a heated discussion on 802.16e, especially the relationship between 802.16e and 3G. There are many different views: some believe that 802.16e will replace 3G, while others believe that 802.16e cannot replace 3G and is only a complementary technology to 3G. In order to analyze the relationship between 802.16e and 3G, the following is a comprehensive comparison of the two technologies.

　　As for 802.16e technology and 3G technology, there are great differences between the two due to their different positioning.

From the perspective of standardization, 802.16e only defines the physical layer and MAC layer of the air interface. The protocols used above the MAC layer and the core network are not within the scope of 802.16e. The standardization of the air interface of 802.16e is expected to be completed in the near future. As a complete network, 3G technology has completed the standardization of air interface specifications, core network series specifications, and service specifications, involving wireless transmission, mobility management, service applications, user number management, etc.

From the perspective of service capabilities, 802.16e mainly provides broadband data services with certain mobility characteristics, and its users are mainly laptop terminals and 802.16e terminal holders. 802.16e accesses the IP core network and can also provide VoIP services. 3G was designed for both voice and data services from the beginning. For voice services, the core network still uses circuit switching, and QoS is highly guaranteed. 802.16e sacrifices mobility in exchange for improved data transmission capabilities, and its data bandwidth is better than that of the 3G system. However, the data capabilities of 3G are also constantly improving. 3G enhanced models such as HSDPA can already achieve an access rate of 10Mbit/s. According to the definition of ITU, the ultimate goal of 3G enhanced models can reach 30Mbit/s.

Although WiMAX transmission rates can reach 10 times or even higher than 3G, and its coverage range can match or even exceed 3G when using low-order modulation, this is not the basic market positioning of the 3G standard for personal mobile terminals that use wireless wide area networks (WWAN) as the basic mode, public voice and multimedia data as content, and roam globally. In essence, WiMAX is only an important support means for 3G and 3G evolution as a wireless metropolitan area network and multi-point base station interconnection. The potential market size of the two is also very different, so there is no question of WiMAX becoming the terminator of 3G.

From the perspective of coverage, 802.16e must sacrifice coverage and mobility in order to obtain a higher data access bandwidth (30Mbit/s). Therefore, 802.16e will mainly solve the problem of hotspot coverage for a long time. The network can provide partial mobility, and the main application will focus on data access in nomadic or low-speed mobile states. 3G is a ubiquitous network with continuous coverage, and users can achieve uninterrupted communication.

In terms of wireless spectrum resources, 3G has globally unified spectrum resources, while 802.16e is trying to find frequency resources between 2 and 6 GHz. The frequencies currently available in different countries are not consistent. Therefore, it is difficult for 802.16e to finally obtain enough globally unified frequencies.

　　From the above analysis, we can see that although 802.16e is superior to 3G in data capacity, from the perspectives of standardization, global unified spectrum, technical characteristics, etc., 802.16e still has a long way to go before it can be truly commercialized, and for a long time it will mainly solve hotspot coverage and some mobility issues. Its application will be after 3G. The emergence of 802.16e will not affect the development of China's 3G industry.

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WiMAX vs. Wi-Fi

　　Wi-Fi stands for Wireless fidelity, and Wi-Fi technology includes the ratified IEEE 802.11a, b, and g specifications, and the pending 802.11n specification. Wi-Fi was the first high-speed wireless technology to be widely deployed, especially in hotspots around the world—including homes and offices, and increasingly coffee shops, hotels, and airports. Wi-Fi hotspots became an almost instant hit around the world, and are sought after by people on the go for their ability to increase productivity. However, Wi-Fi has a very limited range: users can only achieve high-speed connections if they are within 300 feet of a wireless access point (AP). Wi-Fi is one of the earliest high-speed wireless data technologies, and now benefits from a large number of supporting products and technologies. Some of the latest platforms can even support multiple Wi-Fi standards (such as 802.11a, b, and g), thereby supporting compatibility between several wireless networks.

Wi-Fi has created a strong upsurge in the market in recent years. In 2002, a total of 18 million Wi-Fi "hotspots" were sold worldwide, and telecom operators in various countries have also rushed to join the Wi-Fi camp. It is predicted that by 2007, 530,000 hotspots will be installed in the United States, 700,000 in Europe, and more than 1 million in Asia. Why is Wi-Fi developing so rapidly?

Wi-Fi is known as the "wireless version of Ethernet". Since the current Ethernet standard (IEEE 802.3 standard) has almost become synonymous with local area networks, at least 80% of local area networks in the world use Ethernet technology. WLAN is also a standard formulated by IEEE, so it can almost be regarded as an extension of the Ethernet standard in the wireless field. This makes WLAN have the characteristics of seamless transition and smooth installation in application.

The installation and setup of WLAN is quite simple - when you need to establish a network connection in a certain area, you only need to set up the corresponding access points within a certain range, and traditional processes such as planning, wiring, and testing can be ignored. And when users need to add, remove, and migrate, the operation is also very simple. If you set up an Internet cafe LAN, you will spend a lot of time on the layout of HUBs and cables, but after introducing Wi-Fi at home, the entire access process takes less than 10 minutes.

The overall cost of WLAN is very low. It is reported that by implementing wireless LAN solutions, enterprises with an average of 400 users can save up to 4.9 million US dollars in network costs. Due to its convenient access, low cost and no need to apply for a license, WLAN has become a star in the field of public access services.

The bandwidth of 802.11b can reach 11Mbit/s, while 802.11a and 802.11g can reach 54Mbit/s. Such high bandwidth almost catches up with the cable connection and greatly exceeds the same type of wireless network technology. In addition to the network, the application of WLAN will be expanded to a wider range of fields. In addition to being integrated into notebook computers, PDAs, mobile phones and other devices, it will also be integrated into products such as printers, DVD players, game consoles, MP3s, etc., and its functions will be further enhanced.

Although Wi-Fi has many advantages, its security risks are a fatal disadvantage. Wi-Fi uses radio frequency (RF) technology to send and receive data through the air. Since wireless networks use radio waves to transmit data signals, they are very vulnerable to attacks from the outside world. Radio waves can penetrate walls and partitions. Hackers can easily steal data within the coverage of radio waves and even enter unprotected company LANs.

　　However, although Wi-Fi has risen rapidly, in the face of the aggressive development of WiMAX, some people believe that WiMAX will replace Wi-Fi, but some people believe that WiMAX will not replace Wi-Fi, and the two will complement each other in wireless access. The most obvious difference between WiMAX and Wi-Fi is the huge difference in coverage. Wi-Fi can only reach a maximum coverage of 300 feet and can only be used in a wireless LAN environment, while WiMAX 802.16e can usually reach 1 to 3 miles and is mainly positioned for use in a mobile wireless metropolitan area network environment.

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WiMAX vs. DSL

　　xDSL technology can be divided into two types: symmetrical rate type and asymmetrical rate type, depending on whether the upstream and downstream rates are the same. Symmetric rate xDSL includes IDSL, HDSL, SDSL (Single line DSL), HDSL2 and other forms, while asymmetrical xDSL includes ADSL (Asymmetric DSL), G.lite ADSL and VDSL (Very high bit rate DSL). Currently, ADSL technology is the most widely used.

ADSL is a new technology that transmits telephone services and data signals simultaneously on a pair of twisted-pair wires. It is an asymmetric copper wire access network technology and can transmit up to 640Kbit/s upstream and 1.5~8Mbit/s downstream on a pair of user lines. In addition, ADSL uses advanced digital signal processing technology to reduce the impact of line damage on transmission performance.

Although ADSL uses advanced digital signal processing technology, coding modulation technology and error correction technology, when promoting ADSL services, many characteristics of user lines, including background noise on the line, pulse noise, line insertion loss, crosstalk between lines, changes in wire diameter, line bridge taps, line joints and line insulation will affect the performance of high-speed transmission services.

HDSL is a relatively mature technology among many DSL technologies. Its characteristic is that it uses two pairs of twisted pairs to achieve data transmission, supports various rates of N×64Kbit/s, and can reach a maximum rate of 2Mbit/s in both directions. HDSL can achieve normal data transmission within 3.6 kilometers without the help of a relay amplifier. Compared with traditional T1/E1 technology, the most prominent advantage of HDSL is its low cost and easy installation. It is one of the more ideal alternative technologies for digital relay interface T1/E1. SHDSL is an upgraded technology of the single-line version of HDSL (high bit rate DSL), which means that it can save a pair of twisted pairs, with faster transmission rate and longer transmission distance, so it is more convenient to install. SHDSL can provide a bandwidth of 2.3Mbit/s for both upstream and downstream, meeting the special needs of business users. What is more valuable in the market is that the compatibility of SHDSL equipment with ADSL equipment allows different equipment to provide different services on the same platform, reducing the equipment investment and installation costs of operators on the existing ADSL system. Telecom operators can use SHDSL technology to provide users with cheap and convenient dedicated line services and improve the competitiveness of DSL technology in the broadband access market.

VDSL technology pushes the transmission rate of twisted pair to an extremely high level. VDSL requires extremely high data transmission rate over a relatively short distance, and can achieve a transmission rate of up to 58Mbit/s. From a technical point of view, VDSL can actually be regarded as the next generation technology of ADSL, and its average transmission rate can be 5 to 10 times higher than that of ADSL. VDSL can adopt symmetrical and asymmetrical transmission methods, and supports ATM and STM transmission, providing voice and video conferencing and digital images. For telecom operators, VDSL is the best solution for entering video services. As the ultimate technology of DSL technology, VDSL does have an unparalleled advantage in access rate, especially using the existing telephone lines as the transmission medium.

　　Comparing WiMAX technology and DSL technology, it is clear that each has its own advantages. In terms of the use environment, WiMAX technology is used for wireless access, while DSL technology is used for wired access. It is inevitable that WiMAX technology has greater flexibility in networking applications than DSL technology. In terms of transmission rate, the maximum rate of WiMAX technology can reach 30Mbit/s, and the theoretical maximum rate of DSL technology can reach 58Mbit/s, but DSL is more susceptible to the characteristics of user lines, and the actual rate may be reduced. In terms of coverage, WiMAX can reach up to 6 miles, while DSL can only cover up to 3.6 kilometers (2.2356 miles). Although DSL technology is obviously inferior to WiMAX technology, DSL technology is based on the existing copper wire and is significantly lower in cost than WiMAX. However, as time goes by, once the development of WiMAX technology reduces costs significantly, DSL technology will face the threat of being eliminated by WiMAX technology.

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WiMAX vs Cable

　　Cable Modem technology can be divided into two-way symmetrical transmission and asymmetrical transmission in terms of transmission mode. The symmetrical transmission rate is 2Mbit/s~4Mbit/s, and can reach up to 10Mbit/s. The asymmetrical transmission downstream rate is 51Mbit/s, and the upstream rate is 500Kbit/s~31Mbit/s. Cable Modem itself is not just a modem, it integrates the functions of modem, tuner, encryption/decryption equipment, bridge, network interface card, virtual private network agent and Ethernet hub. It does not require dial-up Internet access, does not occupy telephone lines, and can provide a permanent connection online at any time. A virtual private network connection is established between the service provider's equipment and the user's modem. Cable Modem provides a standard 10BaseT or 10/100BaseT Ethernet interface connected to the user's PC device or Ethernet hub. The technical implementation of Cable Modem is generally to separate a 6MHz channel from the 42MHz~750MHz TV channel for downstream data transmission. Usually, downlink data uses 64QAM (quadrature amplitude modulation) modulation, with a maximum rate of up to 27Mbit/s. If 256QAM is used, the maximum rate can reach 51Mbit/s.

In the Cable Modem system, bidirectional asymmetric technology is adopted, and there is a 6MHz analog bandwidth in the downstream direction for users in the system to share. However, this sharing technology will not reduce the transmission rate. Cable Modem is different from the directional call connection of the line-switched telephone network. When connected, users do not occupy a fixed bandwidth, but share it with other active users, and only use network resources at the moment of sending and receiving data. In milliseconds or even microseconds, seize every opportunity to use bandwidth to download data packets. If there is congestion during the peak period of network use, it can be solved by flexibly allocating additional bandwidth. Simply allocating a 6MHz frequency band can double the downstream speed. Another method is to re-divide the physical network in the user segment and reasonably allocate bandwidth to users according to the frequency of access, and the speed can be comparable to that of a dedicated line.

There are some problems in stability, reliability, power supply and operation and maintenance system when using Cable Modem and HFC to build a network. Although the theoretical rate of Cable reaches 51Mbit/s, since the bandwidth of Cable line is shared, it is actually impossible to provide broadband data services after the number of users reaches a certain scale, and the bandwidth shared by users is very limited. In contrast, WiMAX technology has a more obvious bandwidth advantage.

Since the signals of all Cable Modem users are transmitted on the same coaxial cable, there is a risk of being tapped and eavesdropped. The tree-like network characteristics of CATV also make it very easy to cause single point failures. For example, cable damage, amplifier failure, and transmitter failure will cause interruption of user services on the entire node. Although early users of Cable Modem can definitely enjoy very high-quality services, because the bandwidth and frequency band of the line are very abundant when the number of users is small. However, the addition of each Cable Modem user will increase noise, occupy channels, reduce reliability, and affect the service quality of existing users on the line. WiMAX technology does not have the above concerns, and its security and stability are well guaranteed.

　　In addition, considering the cost of networking, Cable Modem can only be used after the HFC is modified. At present, most HFC in China can only meet the 450MHz frequency band requirement, while the use of HFC to provide two-way services requires at least 750MHz bandwidth. This obviously requires the replacement of all coaxial cables that do not meet the requirements. At the same time, to achieve two-way HFC, it is necessary to replace the unidirectional amplifiers currently used in cable TV networks. The high cost of modification also makes it difficult for Cable technology to compete with WiMAX technology.