Comprehensive Broadband Wireless Technology Based on WLAN and WiMAX (1)

WLAN is a wireless LAN. It combines the advantages of wireless communication technology and computer networks, and uses wireless channels as the transmission medium to implement wireless network communication within a short distance.

The basis of the wireless LAN is the traditional wired LAN, which only enables wireless communication through wireless access points (AP), wireless bridges, wireless NICs and other devices on the basis of the wired LAN.

WLAN features ease of installation, scalability, maintenance, mobility, high speed, and use of open frequency bands, or operators have already recognized the advantages of WLAN in wireless data transmission. WLAN can be seamlessly integrated with widely used Ethernet networks, allowing users to access the Internet, conduct online transactions, remote office, and other applications. As the application field continues to expand, various business applications have higher requirements for WLAN, such as speed, security, QoS, and roaming. In addition to data transmission, WLAN also hopes to make breakthroughs in wireless speech. The following briefly introduces the hot areas of WLAN development.

1. Speed

Bandwidth is the foundation of all services. Currently, the most widely used WLAN devices are based on the 802.11b standard, and the maximum wireless speed can reach 11 Mbps. In fact, due to the WLAN standard Wireless Frame head overhead, access control, and so on, users can only get about half of the maximum rate. The wireless interface speed for 802.11a and 802.11g devices is 54 Mbps, and the actual throughput is only about 30 Mbps. At present, the IEEE 802.11n Working Group is developing a High-Speed WLAN standard that can increase the speed to 108/320 Mbps, and further improve its management overhead and efficiency to enhance the performance of WLAN.

2. Security

WLAN implements data communication through wireless signal transmission. The biggest difference between WLAN and wired network is that any wireless network adapter and access point can receive wireless signals. Therefore, the security of WLAN networks has been a hot topic. In addition to the widely used SSID, ACL, and WEP, to improve the security of WLAN networks, the 802.11i standard adopted by IEEE recently has a profound impact on the security of WLAN networks.

The IEEE802.11i standard, combined with the user port authentication and device authentication in 802.1x, modifies and standardizes the MAC layer of the WLAN, and defines a strict encryption format and authentication mechanism to improve the security of the WLAN. The IEEE802.11i standard mainly includes two parts: Wi-Fi-protected Access WPA (wi-fi-FiProtected Access) technology and strong security network RSN technology. WPA uses the Temporary Key Integrity Protocol TKIP (Temporary Key Integrity Protocol) and algorithm to improve the security of WEP. Like WEP, TKIP is also based on RC4 encryption, but the key creation method is different. It can provide the function of quickly updating the key and solve the weakness of WEP vulnerability. RSN adopts Advanced Encryption Standard AES Based on 802.1x protocol and scalable authentication protocol EAP, and uses dynamic authentication and encryption algorithm between access points and mobile devices, to implement more powerful encryption and information integrity checks.

3. QoS

At present, WLAN follows the Ethernet sharing mechanism, so there is almost no distinction between different types of services. In this way, the necessary guarantees cannot be provided for applications that require high latency, bandwidth, packet loss rate, and other attributes such as VoIP and video. Therefore, IEEE sets up an 802.11e task group to refine the MAC layer by 802.11 to improve QoS. Two schemes are defined: Enhanced Distributed Channel Access (EDCA) and Hybrid Coordination (HCF ). EDCA is an extension of the queuing mechanism of the traditional wired LAN. It is used to mark data packets and use the channel access function to differentiate their priorities. Supports eight types of communication with priority levels, and can be directly mapped to RSVP priority protocols. HCF is a query access mechanism. Different transmission streams are allocated to dedicated communication time slots during use. These two mechanisms work together to maintain QoS control between the network and wireless users.

4. Roaming

To address the roaming problem between Access Points of Wireless LAN users, the IEEE Working Group has developed the 802.11f Protocol and elaborated on the Access Point internal Protocol IAPP (Inter-AccessPoint Protocol ), the IAPP protocol is designed to provide AP-To-AP mobile functions to meet users' needs for mobility. Its main function is to facilitate the creation and maintenance of the auto scaling service set. It supports the movement of 802.11 mobile terminals between APs and ensures that each mobile terminal has only one connection relationship with the AP at a specified time.

5. Speech Application

At present, VoIP has been widely accepted by the public. At the same time, people can easily access the network through WLAN. The combination of the two advantages has brought about VoWLAN applications. At present, Wi-Fi Mobile phones are available, but limited to the coverage of WLAN, mainly used within the enterprise, and may be used in the digital home field in the future. Some equipment manufacturers are developing WLAN + GSM or CDMA Dual-mode mobile phones to integrate WLAN voice applications with mobile networks.

The development of WLAN technology is closely related to application requirements. Users' Requirements for mobile extensiveness and high bandwidth are constantly increasing, standard Organizations, equipment manufacturers, and operators are actively developing standards, products, and services to meet user needs. On the one hand, new standards and technologies are used to solve existing technical difficulties and equipment defects. On the other hand, the integration with other technologies can complement each other to achieve the common development of various technologies.