| With the development of the automotive industry,car communication also developed rapidly. Wireless access through a variety of ways becomes to the direction of network development in the future, people are no longer astricted by wire, but may connect internet through a variety of intervention at anytime and anywhere, and get information or communicate with other people. Mobile terminal station (wireless access point) connect with the network, interrupted from the coverage of a mobile base station to another, known as the handoff.A major goal of future communication systems is to seamlessly integrate a variety of advanced multimedia services which support fixed and mobile networks to achieve the integration of the whole network, and the mobile part of the network framework must be set up on the basis of different types of wireless networks overlapping, because of there is no wireless access technology can be used as a universal and long-term universal solution exists so far, while the future of mobile communications technology from the ability to change the focus to the service, from the wireless network to the entire problem.With the increasing prevalence of WLAN technology, low bandwidth of CDMA can not meet people's needs, experts have predicted that 3G will be replaced by cheaper Wi-Fi when it might not be the mainstream consumer.CDMA has the advantage of wide area network, broad coverage, but relatively low bandwidth. It can reach the highest rate of 153.6Kbps, under steady-state rate at only about 70K-80K. The coverage and relative mobility of WLAN network are bad relatively, but the bandwidth is higher than CDMA. The effective rate of WLAN is about 5.5Mbps. It has strong anti-interference, good confidentiality. It is cheaper than CDMA, and has been widely used in the society in all aspects. At the same time, wireless local area network (WLAN) with the characteristics of broadband, mobile and easy to lay. It is suitable to personnel mobility in public places such as airports, stations, hotels and so on. The limited coverage of WLAN lead mobile users can not serve in place without WLAN. In this cases CDMA are needed to fill the wide area network to ensure the progression of operation transmission. Low bandwidth price and limited cover area makes WLAN a good supplement to CDMA. Stronger relation and mutual supplement should be constructed in aspect of mobile between CDMA and WLAN. When user feel the absent of access mode and network, the two technology can be seemed to be amalgamation really. In this case, the value of transfer operation can be exhibited in WLAN. Because of 3G and WLAN have different advantages and limitations in coverage area and bandwidth, the two technology can support different application and meet various needs. In this extent, they develop and supplement mutually. Handoff has become the hotspot and focus.Because of more and more dependent on strong and mobile computing technology of the ever-increasing population on mobile network computing, mobile IP technology came into being in such an environment. IPv4's own design flaws causes IPv4-based mobile IP technology is difficult to make people feel that this is a satisfactory solution for mobile computing. IPv6 mobile computing has become a real turning point, because IPv6 is completely redesigned, it foresaw the need to effectively meet the requirements of mobile computing, and therefore provides a wide range of protocol design for mobile user support. These is a very important role to IPV6. Mobile IM agreement is to provide mobile functionality internet program, it provides a mechanism for IP routing to the mobile node and makes a permanent IP address to connect to any link, and causes handoff nodes still maintain ongoing links communications. It has the scalability, high reliability and high security advantages.Our title of the project is: IPv4/IPv6 dual-stack gateway safety car. It is based on the development of ARM9.0 at redhat9.0 embedded development board. The system can be divided into the database server, monitor the terminal, mobile board system. It Includes GPS positioning, security architecture implementation, CDMA module, WLAN module, as well as handoff between CDMA and WLAN and so on.Handoff can be divided into two types: handoff between the same intervention can be called horizontal handoff, the handoff between different types of intervention to can be called vertical handoff. The witching between CDMA and wireless I have done includes vertical handoff and horizontal handoff between CDMA and WLAN.Handoff process can be divided into three main stages. In accordance with the time and they must satisfy certain constraints at each stage of the order:1, Initiation Phase: This phase is responsible for measurements of signal quality or state of wireless links based on wireless transmission methods, but also may include a number of system parameters, and hereby dicide the need to determine the trigger handoff.2, Decision Phase: this phase is to select access technology and network on the basis of data collected on the Cell.3, Execution Phase: this phase is construct new connection and cut the old connection, and the changing must the same to the selected line in second phase.Handoff trigger parameters are: the absolute signal intensity, with an absolute signal strength threshold, the relative signal strength with threshold, such as the relative signal strength. Performance indicators have to handoff: handoff the ratio of non-essential, the number of attempts to handoff to expect the number of handoff, handoff delay and so on. On the basis of the above working principle of MIPv6 and use of the above parameters, we can do the handoff between CDMA and WLAN.With the rapid development of 802.11 wireless LAN technology, many wireless access points based on the (Access Point, AP) wireless LAN are widely used. AP allocate on a large density range required a highly efficient and reliable mechanism to enable the mobile terminal from a number of AP in the implementation of the dynamic handoff. In the WLAN network, each AP is AP coverage for the center of a circle, a radius of 100 meters round, but also with the surrounding environment in order to select a wireless service can provide a higher quality of AP. When car moved AP has about three possible causes to handoff: 1.The new AP can provide higher quality services in the framework mobile terminal has accepted;2.Mobile terminal leave the AP original coverage; 3.In order to achieve the load balancing between the number of AP. Therefore, the project also includes handoff of WLAN at different levels of the AP.The CDMA and WLAN handoff technology research based on IPv6 under linux fills the gaps in China on the basis of experimental network communication. The social and economic benefits of project construction are very clear, and its significance is significant and far-reaching. With the development of the automotive industry,car communication also developed rapidly. Wireless access through a variety of ways becomes to the direction of network development in the future, people are no longer astricted by wire, but may connect internet through a variety of intervention at anytime and anywhere, and get information or communicate with other people. Mobile terminal station (wireless access point) connected with the network, interrupted from the coverage of a mobile base station to another, known as the handoff.A major goal of future communication systems is to seamlessly integrate a variety of advanced multimedia services which support fixed and mobile networks to achieve the integration of the whole network, and the mobile part of the network framework must be set up on the basis of different types of wireless networks overlapping, because of there is no wireless access technology can be used as a universal and long-term universal solution exists so far, while the future of mobile communications technology from the ability to change the focus to the service, from the wireless network to the entire problem.With the increasing prevalence of WLAN technology, low bandwidth of CDMA can not meet people's needs, experts have predicted that 3G will be replaced by cheaper Wi-Fi when it might not be the mainstream consumer.CDMA has the advantage of wide area network, broad coverage, but relatively low bandwidth. It can reach the highest rate of 153.6Kbps, under steady-state rate at only about 70K-80K. The coverage and relative mobility of WLAN network are bad relatively, but the bandwidth is higher than CDMA. The effective rate of WLAN is about 5.5Mbps. It has strong anti-interference, good confidentiality. It is cheaper than CDMA, and has been widely used in the society in all aspects. At the same time, wireless local area network (WLAN) with the characteristics of broadband, mobile and easy to lay. It is suitable to personnel mobility in public places such as airports, stations, hotels and so on. The limited coverage of WLAN lead mobile users can not serve in place without WLAN. In those cases CDMA is needed to fill the wide area network to ensure the progression of operation transmission. Low bandwidth price and limited cover area make WLAN a good supplement to CDMA. Stronger relation and mutual supplement should be constructed in aspect of mobile between CDMA and WLAN. When user feels the absent of access mode and network, the two technology can be seemed to be amalgamation really. In this case, the value of transfer operation can be exhibited in WLAN. Because of 3G and WLAN have different advantages and limitations in coverage area and bandwidth, the two technologies can support different application and meet various needs. In this extent, they develop and supplement mutually. Handoff has become the hotspot and focus.As the increasing population is more and more dependent on mobile network computing and mobile computing technology, mobile IP technology came into being in such an environment. IPv4's own design flaws causes IPv4-based mobile IP technology is difficult to make people feel that this is a satisfactory solution for mobile computing. IPv6 mobile computing has become a real turning point, because IPv6 is completely redesigned, it foresaw the need to effectively meet the requirements of mobile computing, and therefore provides a wide range of protocol design for mobile user support. These is a very important role to IPV6. Mobile IM agreement is to provide mobile functionality internet program, it provides a mechanism for IP routing to the mobile node and makes a permanent IP address to connect to any link, and causes handoff nodes still maintain ongoing links communications. It has the scalability, high reliability and high security advantages.Our title of the project is: IPv4/IPv6 dual-stack gateway safety car. It is based on the development of ARM9.0 at redhat9.0 embedded development board. The system can be divided into the database server, monitor the terminal, mobile board system. It Includes GPS positioning, security architecture implementation, CDMA module, WLAN module, as well as handoff between CDMA and WLAN and so on.Handoff can be divided into two types: handoff between the same intervention can be called horizontal handoff, the handoff between different types of intervention to can be called vertical handoff. The witching between CDMA and wireless what have done includes vertical handoff and horizontal handoff between CDMA and WLAN. Handoff process can be divided into three main stages. In accordance with the time and they must satisfy certain constraints at each stage of the order:1, Initiation Phase: This phase is responsible for measurements of signal quality or state of wireless links based on wireless transmission methods, but also may include a number of system parameters, and hereby dicide the need to determine the trigger handoff.2, Decision Phase: this phase is to select access technology and network on the basis of data collected on the Cell.3, Execution Phase: this phase is construct new connection and cut the old connection, and the changing must the same to the selected line in second phase. Handoff trigger parameters are: the absolute signal intensity, with an absolute signal strength threshold, the relative signal strength with threshold, such as the relative signal strength. Performance indicators have to handoff: handoff the ratio of non-essential, the number of attempts to handoff to expect the number of handoff, handoff delay and so on. On the basis of the above working principle of MIPv6 and use of the above parameters, then it can do the handoff between CDMA and WLAN.With the rapid development of 802.11 wireless LAN technology, many wireless access points based on the (Access Point, AP) wireless LAN are widely used. AP allocate on a large density range required a highly efficient and reliable mechanism to enable the mobile terminal from a number of AP in the implementation of the dynamic handoff. In the WLAN network, each AP is AP coverage for the center of a circle, a radius of 100 meters round, but also with the surrounding environment in order to select a wireless service can provide a higher quality of AP. When car moved AP has about three possible causes to handoff: 1.The new AP can provide higher quality services in the framework mobile terminal has accepted; 2.Mobile terminal leaves the AP original coverage; 3.In order to achieve the load balancing between the number of AP. Therefore, the project also includes handoff of WLAN at different levels of the AP.The CDMA and WLAN handoff technology research based on IPv6 under linux fills the gaps in China on the basis of experimental network communication. The social and economic benefits of project construction are very clear, and its significance is significant and far-reaching. |
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