Abstract: On the basis of introducing the WLAN standard, the article focuses on the security issues and roaming problems of WLAN, and introduces the GB15629.11 standard formulated by China at the end of the article.
Many emerging wireless broadband technologies will advertise themselves as mainstream technologies in the beginning, such as WLAN (Wireless Local Area Network), Bluetooth, HomeRF, UWB (Ultra Wide Band), etc., but can really stand the test of the market and get the majority. People agree, I am afraid that only the IEEE 802.11 series WLAN is qualified. From the application point of view, WLAN has been proposed for many years, but since it has been simply positioned to extend the wired LAN, plus no uniform standards and low transmission rate, it is not used much, it is difficult to promote. Until the end of the last century, with the advancement of WLAN technology and the unification of standards, it has been widely used as a high-speed wireless access technology for the Internet, and it has been widely used in offices, airports, hotels, shopping malls, coffee houses, etc. Hotsports. Therefore, it was rated as one of the top ten trends in American communication technology in 2000.
Changes in WLAN standards
In addition to the 802.11 announced in 1997, the IEEE 802.11 series of standards includes several new standards such as 802.11a, 11b, and 11g. From a technical point of view, 802.11a occupies the 5 GHz free frequency band. Since there are not many other applications in this frequency band, there is less interference; it uses Orthogonal Frequency Division Multiplexing (OFDM) technology with a high transmission rate in the range of 10 m. The rate can be as high as 54 Mb/s, but as the distance increases, its rate drops rapidly, and it drops to less than 10 Mb/s at more than 70 meters. 802.11b occupies the free band of 2.4GHz, but since many countries use this band in cordless phones, Bluetooth devices and even microwave ovens, the interference is larger. It uses relatively simple direct sequence spread spectrum (DSSS) technology, and its rate can theoretically It reaches 11 Mb/s, but considering the physical layer overhead (at least about 40%) and the free band is susceptible to interference, the rate is much lower. Although 802.11a began to be developed earlier than 802.11b, 802.11b products occupied a larger market share because 802.11b was easier to implement and completed earlier.
Obviously, 802.11a products are not compatible with 802.11b due to the use of different frequency bands. To solve this problem, IEEE developed the 802.11g protocol, which improves speed and transmission distance based on 802.11b compatibility. There are two modulation methods specified in 802.11g, including OFDM used in 802.11a and CCK (complement keying modulation) used in 802.11b. By specifying two modulation methods, the data transmission speed of the 802.11a level is realized in the 2.4 GHz band, and the compatibility with the 802.11b products with more than 11 million installed units is also ensured. The PBCC-22 (CCK-PBCC) modulation scheme and CCK-OFDM proposed by TI to achieve a data transmission speed of 22 Mb/s can also be used as an option. Therefore, 802.11g is actually a hybrid standard. It can adapt to the traditional 802.11b standard, providing 11Mb/s data transmission rate per second at 2.4GHz frequency, and 54Mb/s data transmission at 5GHz frequency in compliance with 802.11a standard. rate. But the cause of the interference determines that 802.11g is unlikely to reach the high rate of 802.11a, and the protocol was officially approved in July 2003, which has led many device manufacturers to adopt 802.11a directly.
Although the maximum rate of the 802.11g standard can reach 54Mb/s, this rate is far from enough for the multimedia services to be carried out in the WLAN in the future. So the IEEE has set up a new working group to prepare a new high-speed WLAN standard 802.11n. The standard uses Multiple Input Multiple Output (MIMO) technology and OFDM technology. It plans to increase the transmission rate of WLAN from 54Mb/s to above 108Mb/s to achieve seamless integration with 100M cable network. The maximum data rate is expected. Up to 320Mb/s.
WLAN In addition to some of the major standards mentioned above, the IEEE is still improving these protocols. The new or upcoming protocols are: 802.11d, which does not use the 2.4GHz band, improves QoS (Quality of Service) for 802.11 protocols. 802.11e, 802.11f with improved switching mechanism, 802.11i with improved security mechanism, etc.
Once the transmission technology standard is determined, the research focus of WLAN should be transferred from software development to software to solve some of the problems it currently encounters: first, security issues, all networks have security problems. However, the wireless network has its particularity; secondly, it is a roaming problem. Unlike the roaming problem of the mobile network, the WLAN roaming problem is more the roaming problem between different operators, as well as settlement and billing issues.
Figure 1 802.11 related standard development blueprint
Figure 2 Wi-Fi and Bluetooth application diagram
Security Issues In any network, data security issues should be the focus of consideration, but security is just one of the weakest places in WLAN. As a relatively reliable wired network security solution, VPN (Virtual Private Network) technology has been adopted to some extent in enterprise wired network applications. However, in a wireless network, radio link quality fluctuations or short interruptions due to factors such as burst interference or AP (access point) handoff may cause a short interruption of the user communication link. Once the link is broken, the user will have to manually reset to restore the VPN connection. This is unbearable for WLAN users, especially WLAN users who need mobility or QoS guarantees (such as VoIP services). In addition, the high complexity and cost of the VPN network also largely hinder the application of VPN technology in WLAN. As early as October 2000, 802.11b adopted the RC4 algorithm-based standard security protocol WEP (Wired Equivalent Privacy), which was found to have security vulnerabilities. It uses a 24-bit initial vector and a 40-bit key to encrypt data, and each user uses the same key, which means that a user's security vulnerability will threaten the security of the entire network. Some new products now support WEP2 (later IEEE named it TKIP: Temporal Key Integrity Protocol, Temporary Key Integrity Check Protocol), although it uses 48-bit initial vector and 128-bit key, it still does not leave WEP Core, fully compatible with WEP. However, the security vulnerability of the WEP algorithm is caused by the WEP mechanism itself, and has nothing to do with the length of the key. Therefore, it is impossible to increase the security of the key length. The increase of the initial vector length can only improve the difficulty of the crack to some extent. , to extend the crack time, and can not solve the problem fundamentally. To some extent, TKIP is more vulnerable because it uses Kerberos passwords and can often be broken with simple guessing methods. The Wi-Fi Alliance and the IEEE 802 committee also acknowledge that TKIP can only be used as a temporary transition solution rather than a final solution. In the long run, AES (Advanced EncrypTIon Standard) encryption is used.
In addition to improving security by encrypting the data to be transmitted, WLAN can enhance its security by enhancing authentication to users. The original 802.11b uses the Service Group Identifier (SSID), but since it is broadcast, users can receive it, so it is easy to be cracked. WLAN later adopted IEEE 802.1x authentication, but 802.1x was not designed for WLAN, it did not take into account the characteristics of wireless applications. 802.1x provides authentication between the wireless client and the RADIUS server, rather than authentication between the client and the wireless access point AP; user authentication with username and password is used, so it is still stored, used, and authenticated. There are great security risks, such as leakage, loss, etc.
Therefore, the security solution given by the IEEE 802.11i standard currently under development is: CCMP (CBC-MAC Protocol) encryption technology based on 802.1x authentication, that is, AES is the core algorithm, and CBC-MAC encryption mode is adopted, with grouping. The initial vector of the sequence number. CCMP is a 128-bit block cipher algorithm that is more secure than all of the previously described algorithms.
Of course, some simple security remedies that can be used before the new standard is officially issued include: paying attention to key management when using the WEP protocol, replacing the default key every day or week; protecting the hard disk and files with a password. Folder; change the default SSID; use the session key provided in some products; use the MAC address filtering function provided in some products.
Our national standard GB15629.11-2003 uses a security protocol called "WLAN Authentication and Privacy Infrastructure" (WAPI) instead of the WEP or TKIP security protocol used in the 802.11 standard. Technically, the WAPI security mechanism is different from current international standards. WAPI adopts the public key system elliptic curve cryptography algorithm approved by the National Cryptographic Management Committee Office and the secret key system block cipher algorithm, which are used for digital certificate, key agreement and transmission data encryption/decryption of WLAN equipment, respectively. The device's identity authentication, link verification, access control, and encryption protection of user information in the wireless transmission state. It has been approved by the ISO/IEC-authorized IEEE RegistraTIon Authority for the allocation of the Ethertype field for the WAPI protocol, which is the only protocol currently approved in the field in China and is awaiting submission to the ISO/IEC JTC1 committee.
From a market perspective, WAPI takes full account of market applications. The application mode is divided into single-point and centralized: single-point is mainly used for small-scale applications of households and small companies; centralized is mainly used in hotspots and large enterprises, and can be combined with the management system of operators. Work together to build a secure wireless application platform. Users can securely apply WLANs in homes, companies, hotspots, etc. without worrying about security and interoperability between devices.
The roaming problem and the coverage distance of the WLAN different from the 3G convergence are also different. Most 802.11b networks can transmit distances of up to 100 meters. Higher power transmitters can extend the coverage distance, but at the same time the signal will be more interfered and more obstacles will be encountered. In addition, considering the security, the WLAN requires limiting the transmission power, which affects the transmission distance. 802.11a can transmit as much as 802.11b. Although in principle, high-frequency electromagnetic waves are more easily absorbed and the transmission distance is shorter, since 11a adopts OFDM technology, the influence of multipath effect can be overcome. Considering these two factors comprehensively, it is easy to draw that their coverage distance is not much different. in conclusion. However, it should be noted that the 54Mb/s rate of 802.11a is achievable within 10 meters. As the distance increases, the rate decreases rapidly, and it drops to less than 10Mb/s when it is more than 70 meters.
Since 802.11g is a new standard and there is no experimental data to illustrate its transmission distance, it is speculated from the principle of OFDM technology that it should be able to reach a longer distance. Of course, increasing the transmission distance is not an advantage, because the wireless bandwidth is shared, and the increase of the distance means that the number of users increases, and the bandwidth that each user can allocate is correspondingly reduced. Therefore, 802.11g is suitable for environments where there are few users or where users have low bandwidth requirements. Another problem is that longer distances will leak signals, and intruders may break into the network from the far end. To solve this problem, we can solve it by using a directional antenna.
In summary, due to limited WLAN power, its service coverage area is limited, and its convenience is greatly reduced. However, if we find a way to connect the WLANs, we can form a wireless metropolitan area network, enabling portable Internet devices such as laptops and PDAs to move wirelessly in the same city to meet the access requirements in the mobile state. In the wireless network IP planning, it is assumed that the "floor" is defined as a network segment, and the users in the building can only maintain the fixed IP movement on their own floors, or switch between the different APs in the network segment. If the user leaves his/her own floor to the downstairs business activity area, he or she has to modify the original IP address in the computer or DHCP to regain a temporary IP to access the Internet. However, at this time, the user can no longer return to his own office network, and obtain corresponding intranet data and normal network working ability.
With mobile IP technology, the same IP address can be used in multiple areas on the IP network, and the network where the network terminal is located is performed by using a special router called a HomeAgent and a Foreign Agent. Management, you can achieve roaming between different network segments of the WLAN. From the perspective of operators, this is the problem of roaming between networks. If you can't roam, consumers need to buy a network of multiple carriers. When accessing different carrier networks, laptops need to log in again. People don't know how to identify operators in specific areas. Therefore, it should be considered that a plurality of wireless ISPs share the statistical information and charging information of the user using the network, coordinate the distribution of interests among the wireless ISPs, and realize interconnection and intercommunication between different operators.
But when roaming can be achieved, it's hard to say now. But the good news is that the world's largest wireless broadband operator alliance (WBA) announced at its third meeting in July 2003 that Wi-Fi international roaming will be in China (China Netcom), Australia, Malaysia and Singapore. The national pilot test, which proposes global brand identity, standard landing interface and Wi-Fi international roaming, aims to ensure that wireless broadband services can continue to operate stably in different countries, and the network can be smoothly and seamlessly connected, thus ensuring users' convenience. Wireless Internet access.
Despite the high access rate of the WLAN, neither the local area network nor the metropolitan area network can obtain data in fast mobility. At present, only cellular networks, ie 2G and 3G, can be accessed in a fast mobile environment. Because of the large coverage of such networks, it can also be called a wireless wide area network. But the fly in the ointment is that its data transmission rate is very low, even if the ideal 3G data transmission rate can only reach 2Mb / s, which is far from the 802.11b 11Mb / s. Therefore, it can only achieve "unlimited coverage, limited bandwidth"; in contrast, WLANs extended from wired LANs have the characteristics of "limited coverage, unlimited bandwidth". Therefore, in places where new lines cannot be deployed, WLAN can be used as a supplement to wired LAN; in some "hot spots" areas, WLAN can be used as a 3G competition solution. From this perspective, WLAN and 3G are not perfect. Different technologies and different solutions are positioned differently in the market. There may be a replacement relationship, but it is more likely to be a coexistence symbiotic relationship. For example, China Mobile has joined Lenovo in the external GPRS module in the laptop network card, through the SIM card to achieve Internet access and billing, trying to find the most suitable space in the wireless WAN and WLAN frontal confrontation. But in any case, WLAN will definitely have a big impact on 3G.
China's WLAN Strategy National Standardization Management Committee has officially promulgated the China WLAN GB 15629.11-2003 series of standards drafted by the "China Broadband Wireless IP Standards Working Group" (). The WLAN standard is based on the principle of adopting the international standard ISO/IEC8802.11 series standard. On the basis of fully considering and taking into account the interconnection and intercommunication of WLAN products, the technical solutions and specifications are given for the security problem of WLAN. It incorporates the country's requirements for cryptographic algorithms and radio frequencies. It is based on international standards and conforms to the Chinese security standards. These two standards are national enforcement standards and will be officially implemented in June 2004. WLAN products that do not meet this standard will not be allowed to appear on the market.
Although the introduction and enforcement of our national WLAN standards have had a great impact, this is a concrete implementation of China's information security strategy, which shows that our country has taken a solid step.
Many emerging wireless broadband technologies will advertise themselves as mainstream technologies in the beginning, such as WLAN (Wireless Local Area Network), Bluetooth, HomeRF, UWB (Ultra Wide Band), etc., but can really stand the test of the market and get the majority. People agree, I am afraid that only the IEEE 802.11 series WLAN is qualified. From the application point of view, WLAN has been proposed for many years, but since it has been simply positioned to extend the wired LAN, plus no uniform standards and low transmission rate, it is not used much, it is difficult to promote. Until the end of the last century, with the advancement of WLAN technology and the unification of standards, it has been widely used as a high-speed wireless access technology for the Internet, and it has been widely used in offices, airports, hotels, shopping malls, coffee houses, etc. Hotsports. Therefore, it was rated as one of the top ten trends in American communication technology in 2000.
Changes in WLAN standards
In addition to the 802.11 announced in 1997, the IEEE 802.11 series of standards includes several new standards such as 802.11a, 11b, and 11g. From a technical point of view, 802.11a occupies the 5 GHz free frequency band. Since there are not many other applications in this frequency band, there is less interference; it uses Orthogonal Frequency Division Multiplexing (OFDM) technology with a high transmission rate in the range of 10 m. The rate can be as high as 54 Mb/s, but as the distance increases, its rate drops rapidly, and it drops to less than 10 Mb/s at more than 70 meters. 802.11b occupies the free band of 2.4GHz, but since many countries use this band in cordless phones, Bluetooth devices and even microwave ovens, the interference is larger. It uses relatively simple direct sequence spread spectrum (DSSS) technology, and its rate can theoretically It reaches 11 Mb/s, but considering the physical layer overhead (at least about 40%) and the free band is susceptible to interference, the rate is much lower. Although 802.11a began to be developed earlier than 802.11b, 802.11b products occupied a larger market share because 802.11b was easier to implement and completed earlier.
Obviously, 802.11a products are not compatible with 802.11b due to the use of different frequency bands. To solve this problem, IEEE developed the 802.11g protocol, which improves speed and transmission distance based on 802.11b compatibility. There are two modulation methods specified in 802.11g, including OFDM used in 802.11a and CCK (complement keying modulation) used in 802.11b. By specifying two modulation methods, the data transmission speed of the 802.11a level is realized in the 2.4 GHz band, and the compatibility with the 802.11b products with more than 11 million installed units is also ensured. The PBCC-22 (CCK-PBCC) modulation scheme and CCK-OFDM proposed by TI to achieve a data transmission speed of 22 Mb/s can also be used as an option. Therefore, 802.11g is actually a hybrid standard. It can adapt to the traditional 802.11b standard, providing 11Mb/s data transmission rate per second at 2.4GHz frequency, and 54Mb/s data transmission at 5GHz frequency in compliance with 802.11a standard. rate. But the cause of the interference determines that 802.11g is unlikely to reach the high rate of 802.11a, and the protocol was officially approved in July 2003, which has led many device manufacturers to adopt 802.11a directly.
Although the maximum rate of the 802.11g standard can reach 54Mb/s, this rate is far from enough for the multimedia services to be carried out in the WLAN in the future. So the IEEE has set up a new working group to prepare a new high-speed WLAN standard 802.11n. The standard uses Multiple Input Multiple Output (MIMO) technology and OFDM technology. It plans to increase the transmission rate of WLAN from 54Mb/s to above 108Mb/s to achieve seamless integration with 100M cable network. The maximum data rate is expected. Up to 320Mb/s.
WLAN In addition to some of the major standards mentioned above, the IEEE is still improving these protocols. The new or upcoming protocols are: 802.11d, which does not use the 2.4GHz band, improves QoS (Quality of Service) for 802.11 protocols. 802.11e, 802.11f with improved switching mechanism, 802.11i with improved security mechanism, etc.
Once the transmission technology standard is determined, the research focus of WLAN should be transferred from software development to software to solve some of the problems it currently encounters: first, security issues, all networks have security problems. However, the wireless network has its particularity; secondly, it is a roaming problem. Unlike the roaming problem of the mobile network, the WLAN roaming problem is more the roaming problem between different operators, as well as settlement and billing issues.
Figure 1 802.11 related standard development blueprint
Figure 2 Wi-Fi and Bluetooth application diagram
Security Issues In any network, data security issues should be the focus of consideration, but security is just one of the weakest places in WLAN. As a relatively reliable wired network security solution, VPN (Virtual Private Network) technology has been adopted to some extent in enterprise wired network applications. However, in a wireless network, radio link quality fluctuations or short interruptions due to factors such as burst interference or AP (access point) handoff may cause a short interruption of the user communication link. Once the link is broken, the user will have to manually reset to restore the VPN connection. This is unbearable for WLAN users, especially WLAN users who need mobility or QoS guarantees (such as VoIP services). In addition, the high complexity and cost of the VPN network also largely hinder the application of VPN technology in WLAN. As early as October 2000, 802.11b adopted the RC4 algorithm-based standard security protocol WEP (Wired Equivalent Privacy), which was found to have security vulnerabilities. It uses a 24-bit initial vector and a 40-bit key to encrypt data, and each user uses the same key, which means that a user's security vulnerability will threaten the security of the entire network. Some new products now support WEP2 (later IEEE named it TKIP: Temporal Key Integrity Protocol, Temporary Key Integrity Check Protocol), although it uses 48-bit initial vector and 128-bit key, it still does not leave WEP Core, fully compatible with WEP. However, the security vulnerability of the WEP algorithm is caused by the WEP mechanism itself, and has nothing to do with the length of the key. Therefore, it is impossible to increase the security of the key length. The increase of the initial vector length can only improve the difficulty of the crack to some extent. , to extend the crack time, and can not solve the problem fundamentally. To some extent, TKIP is more vulnerable because it uses Kerberos passwords and can often be broken with simple guessing methods. The Wi-Fi Alliance and the IEEE 802 committee also acknowledge that TKIP can only be used as a temporary transition solution rather than a final solution. In the long run, AES (Advanced EncrypTIon Standard) encryption is used.
In addition to improving security by encrypting the data to be transmitted, WLAN can enhance its security by enhancing authentication to users. The original 802.11b uses the Service Group Identifier (SSID), but since it is broadcast, users can receive it, so it is easy to be cracked. WLAN later adopted IEEE 802.1x authentication, but 802.1x was not designed for WLAN, it did not take into account the characteristics of wireless applications. 802.1x provides authentication between the wireless client and the RADIUS server, rather than authentication between the client and the wireless access point AP; user authentication with username and password is used, so it is still stored, used, and authenticated. There are great security risks, such as leakage, loss, etc.
Therefore, the security solution given by the IEEE 802.11i standard currently under development is: CCMP (CBC-MAC Protocol) encryption technology based on 802.1x authentication, that is, AES is the core algorithm, and CBC-MAC encryption mode is adopted, with grouping. The initial vector of the sequence number. CCMP is a 128-bit block cipher algorithm that is more secure than all of the previously described algorithms.
Of course, some simple security remedies that can be used before the new standard is officially issued include: paying attention to key management when using the WEP protocol, replacing the default key every day or week; protecting the hard disk and files with a password. Folder; change the default SSID; use the session key provided in some products; use the MAC address filtering function provided in some products.
Our national standard GB15629.11-2003 uses a security protocol called "WLAN Authentication and Privacy Infrastructure" (WAPI) instead of the WEP or TKIP security protocol used in the 802.11 standard. Technically, the WAPI security mechanism is different from current international standards. WAPI adopts the public key system elliptic curve cryptography algorithm approved by the National Cryptographic Management Committee Office and the secret key system block cipher algorithm, which are used for digital certificate, key agreement and transmission data encryption/decryption of WLAN equipment, respectively. The device's identity authentication, link verification, access control, and encryption protection of user information in the wireless transmission state. It has been approved by the ISO/IEC-authorized IEEE RegistraTIon Authority for the allocation of the Ethertype field for the WAPI protocol, which is the only protocol currently approved in the field in China and is awaiting submission to the ISO/IEC JTC1 committee.
From a market perspective, WAPI takes full account of market applications. The application mode is divided into single-point and centralized: single-point is mainly used for small-scale applications of households and small companies; centralized is mainly used in hotspots and large enterprises, and can be combined with the management system of operators. Work together to build a secure wireless application platform. Users can securely apply WLANs in homes, companies, hotspots, etc. without worrying about security and interoperability between devices.
The roaming problem and the coverage distance of the WLAN different from the 3G convergence are also different. Most 802.11b networks can transmit distances of up to 100 meters. Higher power transmitters can extend the coverage distance, but at the same time the signal will be more interfered and more obstacles will be encountered. In addition, considering the security, the WLAN requires limiting the transmission power, which affects the transmission distance. 802.11a can transmit as much as 802.11b. Although in principle, high-frequency electromagnetic waves are more easily absorbed and the transmission distance is shorter, since 11a adopts OFDM technology, the influence of multipath effect can be overcome. Considering these two factors comprehensively, it is easy to draw that their coverage distance is not much different. in conclusion. However, it should be noted that the 54Mb/s rate of 802.11a is achievable within 10 meters. As the distance increases, the rate decreases rapidly, and it drops to less than 10Mb/s when it is more than 70 meters.
Since 802.11g is a new standard and there is no experimental data to illustrate its transmission distance, it is speculated from the principle of OFDM technology that it should be able to reach a longer distance. Of course, increasing the transmission distance is not an advantage, because the wireless bandwidth is shared, and the increase of the distance means that the number of users increases, and the bandwidth that each user can allocate is correspondingly reduced. Therefore, 802.11g is suitable for environments where there are few users or where users have low bandwidth requirements. Another problem is that longer distances will leak signals, and intruders may break into the network from the far end. To solve this problem, we can solve it by using a directional antenna.
In summary, due to limited WLAN power, its service coverage area is limited, and its convenience is greatly reduced. However, if we find a way to connect the WLANs, we can form a wireless metropolitan area network, enabling portable Internet devices such as laptops and PDAs to move wirelessly in the same city to meet the access requirements in the mobile state. In the wireless network IP planning, it is assumed that the "floor" is defined as a network segment, and the users in the building can only maintain the fixed IP movement on their own floors, or switch between the different APs in the network segment. If the user leaves his/her own floor to the downstairs business activity area, he or she has to modify the original IP address in the computer or DHCP to regain a temporary IP to access the Internet. However, at this time, the user can no longer return to his own office network, and obtain corresponding intranet data and normal network working ability.
With mobile IP technology, the same IP address can be used in multiple areas on the IP network, and the network where the network terminal is located is performed by using a special router called a HomeAgent and a Foreign Agent. Management, you can achieve roaming between different network segments of the WLAN. From the perspective of operators, this is the problem of roaming between networks. If you can't roam, consumers need to buy a network of multiple carriers. When accessing different carrier networks, laptops need to log in again. People don't know how to identify operators in specific areas. Therefore, it should be considered that a plurality of wireless ISPs share the statistical information and charging information of the user using the network, coordinate the distribution of interests among the wireless ISPs, and realize interconnection and intercommunication between different operators.
But when roaming can be achieved, it's hard to say now. But the good news is that the world's largest wireless broadband operator alliance (WBA) announced at its third meeting in July 2003 that Wi-Fi international roaming will be in China (China Netcom), Australia, Malaysia and Singapore. The national pilot test, which proposes global brand identity, standard landing interface and Wi-Fi international roaming, aims to ensure that wireless broadband services can continue to operate stably in different countries, and the network can be smoothly and seamlessly connected, thus ensuring users' convenience. Wireless Internet access.
Despite the high access rate of the WLAN, neither the local area network nor the metropolitan area network can obtain data in fast mobility. At present, only cellular networks, ie 2G and 3G, can be accessed in a fast mobile environment. Because of the large coverage of such networks, it can also be called a wireless wide area network. But the fly in the ointment is that its data transmission rate is very low, even if the ideal 3G data transmission rate can only reach 2Mb / s, which is far from the 802.11b 11Mb / s. Therefore, it can only achieve "unlimited coverage, limited bandwidth"; in contrast, WLANs extended from wired LANs have the characteristics of "limited coverage, unlimited bandwidth". Therefore, in places where new lines cannot be deployed, WLAN can be used as a supplement to wired LAN; in some "hot spots" areas, WLAN can be used as a 3G competition solution. From this perspective, WLAN and 3G are not perfect. Different technologies and different solutions are positioned differently in the market. There may be a replacement relationship, but it is more likely to be a coexistence symbiotic relationship. For example, China Mobile has joined Lenovo in the external GPRS module in the laptop network card, through the SIM card to achieve Internet access and billing, trying to find the most suitable space in the wireless WAN and WLAN frontal confrontation. But in any case, WLAN will definitely have a big impact on 3G.
China's WLAN Strategy National Standardization Management Committee has officially promulgated the China WLAN GB 15629.11-2003 series of standards drafted by the "China Broadband Wireless IP Standards Working Group" (). The WLAN standard is based on the principle of adopting the international standard ISO/IEC8802.11 series standard. On the basis of fully considering and taking into account the interconnection and intercommunication of WLAN products, the technical solutions and specifications are given for the security problem of WLAN. It incorporates the country's requirements for cryptographic algorithms and radio frequencies. It is based on international standards and conforms to the Chinese security standards. These two standards are national enforcement standards and will be officially implemented in June 2004. WLAN products that do not meet this standard will not be allowed to appear on the market.
Although the introduction and enforcement of our national WLAN standards have had a great impact, this is a concrete implementation of China's information security strategy, which shows that our country has taken a solid step.
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