Summary The problem of introducing WLAN access in China Unicom's existing CDMA2000 1X network has been discussed. The structure of CDMA2000 1x network and WLAN network is introduced, focusing on introducing WLAN access in CDMA2000 1x networks and services. Process and propose possible problems. Key words CDMA2000 1X WLAN PDSN Mobile IP Mode Simple IP Mode China Unicom has built CDMA2000 1x network in early 2003, and is currently improving to the third generation mobile communication network. From the application of the current network, the highest service transfer rate in the CDMA2000 1x network air is 150 kbit / s, and there is a phenomenon of speech and data service sharing carriers in some data service hotspots. These situations indicate that existing CDMA 2000 1x networks are difficult to meet business needs of high-speed data business hotspots. China Mobile's GPRS network also has similar problems. In order to solve this problem, China Mobile introduced 802.11 Wireless Lan (WLAN), and built WLANs in business office buildings, hotels, exhibition halls, airports and other areas. GPRS and WLAN dual-mode access, meet the high-speed data needs of high-end users, enhanced corporate image, enhanced market competitiveness.
Compared with the GPRS network, the introduction of WLAN access in CDMA2000 1x network is easier in technology implementation. The following will explore how the existing CDMA2000 1x network is economically, which is convenient to introduce WLAN access. 1 CDMA2000 1X Packet Network Structure CDMA2000 1x Packet Data Service is completely based on IP, and its network model includes two types of simple IP and mobile IP. The CDMA2000 1x packet core network adds PCF (packet control function) on the BSC side, mainly to implement two layers between PDSN (packet data service nodes) and management of radio resources and status, etc .; PDSN / FA (field Agent) mainly implements connection with mobile terminal PPP, connected to the packet data service network, with AAA authentication, supports the RADIUS client, receives charging information of PCF to form user billing record, support user address dynamic allocation in simple IP In the mobile IP, the FA function is supported; HA (home agent) is only used in mobile IP, mainly completing the mobile IP registration, allocating the user's home IP address, connected to the PDSN / FA tunnel. The PCF defines A8 (for carrier traffic) and A9 (for transport signaling) interfaces between the PCF and the BSC, and the PCF defines A10 (for carrying traffic) and A11 (for transmission signaling) interfaces to the PDSN.
In the actual network, BSC and PCF come from the same vendor, the A8 and A9 interfaces have not been open, while the A10 and A11 interfaces have good openness. From a network structure, the main difference between simple IP and mobile IP is that simple IP does not require FA function without HA and PDSN. From the business function, the main difference between simple IP and mobile IP is that in the mobile IP, PDSN / FA is connected to the Tunnel connection between HA, the agent discovery mechanism and the mobile registration mechanism, and the service is not interrupted when the user roams; Assign a static IP address to the user to facilitate the traffic initiated by the network; Simple IP is difficult to implement the traffic across PDSN and the user uses a static IP address to realize the network side. Due to the cluster, the single system PDSN can support millions of users at the same time, and the existing mobile terminal supports the support of mobile IP is not very mature, so the China Union Covenant Stage mainly uses simple IP networking mode, and The PDSN is set in the province to reduce roaming across PDSN. The discussion on this article is based primarily based on simple IP networking mode. 2 WLAN Profile Currently, 802.11 WLANs have main technical standards include 802.11b, 802.11a and 802.11, all based on CSMA / CA Ethernet protocol. 802.11B is currently the most widely used standard in China, also known as Wi-Fi, using 2.4 GHz band, CCK modulation technology, maximum shared bandwidth of 11 mbit / s.
At present, the indoor coverage of the product is generally 30 ~ 50 m, and the outdoor coverage can reach 100 to 200 m. 802.11a adopts 5 GHz UNII band, OFDM modulation technology, the maximum shared bandwidth is 54 mbit / s. 802.11g The largest shared bandwidth is 54 mbit / s, which is more than 802.11b, so it will be more likely to be widely adopted in the future. From the maturity of technology and products, WLANs are introduced in CDMA2000 1X, and the 802.11b network should be used. The AP mainly completes the Wireless Ethernet access function of the 802.11b mobile terminal, and can provide a wireless transmission rate of 11 mbit / s. AP typically includes wireless processing modules and Ethernet interface modules, which can complete the simplicity of the management of wireless users, the dynamic allocation of wireless channels, and the conversion of 802.11b and 802.3 Ethernet protocols. AC mainly completes the connection with users (such as PPP, etc.), with AAA supports PPPoE, DHCP Web, 802.1x and SIM authentication methods, dynamic allocation of user addresses, supports RADIUS client and forming user billing records, user security mechanisms, etc. Features. At present, vendors can do seamless coverage and roaming of AP under the same AC control.
3 CDMA2000 1x Introduced WLAN Access Solution 3.1 Network Structure of CDMA2000 1x WLAN It can be seen from the above-mentioned analysis of CDMA2000 1x and WLAN basic structures, and the functionality of both functional entities has more points: AP and BTS, Both the BSC / PCF can realize the spatial access of wireless users and the management of radio resources and status; both AC and PDSN can end with PPP connections between mobile terminals, with AAA to authenticate and billing; the same AC control Roaming, in the simple IP network, the PCF under the same PDSN is roaming. In view of the above common point, it is more convenient and economical for the CDMA2000 1x existing network to implement WLAN access. (1) Improvement of the original WLAN: The PCF is defined between the A10 and A11 interfaces between the PCF and the PDSN in the CD-MA2000 1X network, providing the PCF to provide the necessary protocol foundation through the IP network connection PDSN, which mainly transmits the meter from the wireless network. The fee record, PCF and PDSN connection control messages and user data. The AP can only complete the Layer 2 protocol, which is difficult to cross the three-layer IP network unless the tunnel method or a line is used to access the PDSN.
Therefore, the APGW (AP Gate-Way) device is added to the network, and the function of the A10, A11 interface is used to implement the wireless network billing record, and the PDSN connection control information and the transmission of user data adopted by the GRE package. The AP can access the PDSN through the IP network to facilitate WLAN access on the existing CD? -Ma2000 1x network. For easy transmission, the APGW should be close to the AP settings. (2) Improvements to the original CDMA2000 1X network: Since both CD-MA2000 1x and WLANs share PDSN and AAA, the PDSN is required to at least implement the WLAN user's PPPoE access, open interface with APGW, for CDMA2000 1x And the identification and intralation of WLAN users, requiring the AAA server to implement the authentication and charging of WLAN users. Take the above provincial CDMA2000 1X network as an example, explaining how to deploy WLAN on China Unicom existing CDMA2000 1x network. APGW can access router in CDMA2000 1x network through China Unicom's existing metropolitan area network, through China Unicom's existing R-P interface IP network to connect with PDSN.
The business process of WLAN access in the CDMA2000 1X network is as follows. (1) When the mobile terminal detects the WLAN signal in the WLAN, it is connected to the AP and initiates a registration request. (2) The AP / APGW receives the registration request message to send an indication message to the PDSN to create a new packet data session. (3) PDSN creates a PPP session, PDSN and APGW generate a binding record for the A10 connection. (4) If CHAP or PAP authentication is used when the PPP is established, the PDSN sends an authentication request to the AAA. In addition to the authentication information, the request also includes a user service outline. (5) Visiting the AAA server forwarding the authentication request to the mobile terminal home AAA server. (6) The home AAA server sends an authentication response to the AAA server. (7) The home AAA server forwarded the certification response to PDSN. (8) Establish a PPP session, PDSN assigns an IP address to the mobile terminal, and PDSN sends billing start messages to the AAA server, and invigorate the AAA server forwards the certification bill to the home AAA server. (9) Mobile terminal and PDSN use the PPP session to perform data transfer. The APGW can transmit or receive data on the A10 connection via the GRE frame. The APGW sends a registration request message to update the A10 connection before the registration life exceeds the registration life.
Registration request messages can also be used to transfer information related to billing and other information to PDSN, which are transmitted on system-defined trigger points. For valid registration requests, PDSN returns a A11 registration response message that accepts instructions and survival values. PDSN and APGW update the binding record of the A10 connection. PDSN saves information related to billing before returning to the registration response message (if received) is used for further processing. (10) If the user or PDSN terminates the data service, the PDSN will terminate and remove the user's PPP connection, remove the RP connection with the APGW, and send the charging information to the AAA. 3.2 CDMA2000 1x WLAN implemented business Currently, CDMA2000 1x network mainly provides Internet services, special network access services, WAP / BREW / JAVA-based business, and multimedia communication services. In the CDMA2000 1x network, WLAN is introduced, just provide a higher bandwidth access method, as long as mobile terminal support, you can implement a variety of existing CDMA2000 1X data services, and provide higher bandwidth requirements such as VOD, video broadcasting, etc. business. The introduction of WLAN does not affect the technical system of the existing CDMA2000 1x and the evolution to 1x / EV, as well as existing business strategies, networking strategies, billing strategies, address assignment policies, etc. 4 Explanation (1) WLAN itself Technical issues WLAN technology itself has radio frequency interference problems; in the user-intensive region, inherent collision detection and resending mechanism makes the problem of spectral efficiency reduced sharply; wireless interface security issues, etc. These issues can be gradually resolved through good network planning and continuous improvement of security mechanisms.
