What is a Mobile Node?

Mobility refers to the feature that users can enter one or more communication networks to communicate from any place. Service mobility management exists to support service mobility. It must support the QoS of the current session when the user is roaming. At the same time, it needs to ensure that mobile devices (including mobile phones, PDAs and notebooks) can access all customized network services . ^[1]

Wireless communication users move from one area to another, and their communication connections can also

Mobility management is used when the location area of a mobile station changes. Including mobile station registration and roaming. Mobile station registration is to report characteristics, such as location or status, of the mobile station to the network. Both the mobile station and the network can initiate registration. The registration initiated by the mobile station is that the mobile station informs the service provider of its presence and desire to be served. After being registered as a mobile station's geographic location, the network can pass calls to it.

When mobile users leave the registered system service area and enter other system service areas, the ability to obtain communication is called roaming. For example, if a user in Beijing moves to Tianjin, we call it a roaming state. In a roaming state, the user information is copied from the user management server in the original home area to the user management server in the roaming area. ^[5]

Mobility Terminal Mobility

Traditional mobility refers to terminal mobility, that is, users can use a certain terminal while moving,

Mobility

The access points for users to access services are not fixed, and the network has the ability to identify and locate terminals.

The mobile communication network mainly solves the problem of terminal mobility. The 2G / 2.5G mobile communication network supports mobility mainly at the physical layer and the link layer, including location management, handover management, and roaming support. With the development of wireless technology and the Internet, user mobility between heterogeneous networks has increased, and the demand for data services has increased, making the network layer more involved in supporting mobility. The IP network will be the backbone network of the future, so IP mobility is the main problem to be solved at the network layer.

According to the main supporters of mobility in the mobility implementation technology, terminal mobility can be divided into Edge Mobility and Host Mobility.

Edge mobility refers to when the mobile node moves, the network is responsible for routing the data flow to the current network access point of the mobile node.

Host mobility means that when a mobile node moves, the mobile node itself is responsible for routing the data flow to the current location without the assistance of the network.

Compared with host mobility, edge mobility is supported by the network, while host mobility is supported by the mobile node itself. The advantage of edge mobility is that it can rely on the local state when it is implemented, it can change the route when it is close to the mobile node, and it can achieve fast handover and smooth handover. The disadvantage is that it can't do anything about mobility outside the network. The advantage of host mobility is that it can realize the mobility of different access technologies in the global scope, and the disadvantage is that the signaling load of location update is large. The typical technologies used by edge mobility are intra-domain mobility management and NetLMM in cellular networks, while the typical technologies for host mobility management are Mobile IPv4, Mobile IPv6, and HIP.

Edge mobility and mobile office and management host mobility are not an antithetical relationship. Together they provide complete mobility support and good performance. ^[4]

Personal mobility

Personal mobility means that users can use any terminal to access the same service through personal identification. User access to services is not related to the terminal. The network has the ability to identify and locate users.

Mobility

The support for personal mobility is mainly implemented as a network service.

Universal Personal Telecommunications (UPT) is such a service that supports personal mobility. UPT users use a unique personal communication number that can access any network and can initiate and accept any type of call across multiple networks. The personal communication number can be translated into the corresponding communication number and routed according to the user's requirements, and will be received at any place specified by the user in the future. UPT implementation solutions are generally based on intelligent networks. UPT is also supported by intelligent networks.

One of the main business. Due to the characteristics and defects of the intelligent network, the UPT function is limited. Support for personal mobility is mainly reflected in telephone calling services. In addition, email and other services are actually services that support personal mobility. Unlike terminal mobility, which emphasizes that the same terminal changes network access points due to movement, personal mobility emphasizes access point changes when the same user uses different terminals or spans different network interfaces. At the same time, the main issues in achieving personal mobility include communication reachability and business personalization.

The key to achieving communication reachability is to use the user, not the terminal, as the endpoint of the communication. You need to set up a unique identity for each user and dynamically map the identity used in the communication process to the specific domain or terminal . Various personal mobility solutions are designed to address this critical issue. ^[4]

Mobility Session Mobility

Session mobility means that users can suspend and resume services between different terminals during the use of services

Mobility

Sessions, users can move between terminals while using services. In fact, session mobility is reflected in N-ISDN. The N-ISDN terminal can be carried as a supplementary service, which allows the service to move a call from a terminal within a given access port when the call is running. To another terminal. Of course, this session mobility is also very limited in both function and scope.

The future development of heterogeneous and coexisting network environments and terminal technologies has brought the following new features:

(I) In the future network environment, there are multiple heterogeneous wireless access technologies with different characteristics in terms of coverage, bandwidth, and delay. For example, IEEE 802.15 can form a wireless personal area network (WPAN) with a range of tens of meters, and IEEE 802.1 1 can form a wireless local area network (WLAN) with a wireless coverage of hundreds of meters. Ten kilometers of wireless metropolitan area network (WMAN) coverage, while cellular mobile communication networks (2G and 3G) achieve wide area network (WWAN) range of wireless coverage, and satellite communication networks can achieve global coverage. At the same time, there is a large amount of heterogeneous wireless access network overlap.

(2) With the advancement of information and communication technology, more and more terminals in the future may have multiple different access network interfaces, or multiple terminals of the same user (such as mobile phones, PDAs, notebook computers, printers, fax machines, and Sensors, etc.) realize interconnection and cooperative work through personal area network (WPAN) technology, so that users in overlapping areas of the network can simultaneously utilize network services provided by multiple available access networks.

Based on the above analysis, most research on session mobility in future mobility management focuses on two hot issues of vertical handover and connectivity management. ^[4]