Terminal mobility
The traditional mobility refers to the terminal mobility, that is, the user can use a terminal in the mobile, and the access point of the user accesses the service is not fixed, the network has the ability to identify and position the terminal. From an OSI perspective, the terminal mobility solution is generally distinguished from the physical layer, link layer, network layer, transport layer, session layer, and application layer.
The mobile communication network mainly solves the terminal mobility problem, 2G / 2.5G mobile communication network is mainly reflected on the physical layer and the link layer, including location management, switch management, roaming support, etc. And the development of wireless technology and Internet, the mobile phone between heterogeneous networks and the demand for data services, which make the network layer to participate in supporting mobility, and IP network will be the future backbone network, so IP mobility It is the main solution of network layer movement. Mobile IP and derived other protocols, Mobile IPv6, etc. are the main solutions to solve IP mobility issues. It is generally discussed that the terminal mobility has set from the three layers of the physical layer, the link layer, and the network layer. The mobility scheme of network layers such as Mobile IP is discussed below. The physical layer and the link layer move can refer to the mobility management of the mobile communication network, the transport layer movement can be refer to [1], the conversation layer can be referred to [2], and the application layer movement can be referred to [3].
The basic principle of Mobile IP is to allow mobile hosts (MH, Mobile Host) to implement mobile features using a pair of IP addresses, introducing two network entities of the local agent (HA, HOME Agent) and the FA, Foreign Agent. When MH is in the local network, it communicates with normal IP protocols. When MH enters the field network, it obtains the transfer address (COA, CARE OF ADDRESS) through an external agent or DHCP, and registering its COA to the HA. The data package for the mobile node is sent to the mobile node to reach the local network of MH through normal IP routing. The Tunnel technology forwards them to MH's current FA or MH itself, from MH to CH packets use normal IP routes. Mobile IP mainly exists, 1) "Triangle Routing" problem. The packet sent to MH must be passed through HA, while the packet sent from MH to CH is directly transmitted, which in the case where MH is away from HA, CH and MH, in particular, low; 2) switching the problem. During the switching process, the MH is far from HA, then the Tunnel of HA and MH is established in the outdated position information will cause serious packet loss; 3) Internal movement problems: frequent MH in small range, resulting in frequent switching, resulting in frequent switching A large number of registration packets in the network seriously affects network performance. For the above problems, many new programs are derived from Mobile IP, such as solving routing of triangle routing issues Mobile IP scheme [4], optimized hierarchical mobile IP solutions [5], more solutions [6]. Mobile IP is applied to the wireless honeycomb network, and it is also necessary to make changes based on the network and terminals. This solution has Cellular IP [7] in which mobile management and Mobile IP in the cellular system.
Mobile IPv6 supports the idea of hosting the host, MOBILE IP works, MH works like any fixed host and router when its local network, when MH enters the field network, use IPv6-defined address automatic configuration method to get new COA, MH The COA notified HA with CH, the CH sent by the COA of MH, first routed to the local network of MH, and HA sent these packets to MH through the tunnel, when MH received a tunnel packet forwarded from HA After that, it knows that the original sender of the packet does not have MH COA, MH will send a binding update message to the CH, inform CH, you can send the packet directly to MH after receiving the binding update message. . In the opposite direction, the packet sent out directly from the MH to CH. Mobile IPv6 relative to Mobile IP has the following features:
l Canceled FA. In the Mobile IP, there may be multiple MH sharing a FA IP address, that is, the COA of FA to alleviate the IPv4 address resource tight problem. In this case, the Data reported by HA is also transferred to MH after FA. In IPv6, MH can find a default router to provide routing services, rich address resources, and IPv6 address automatic configuration functions, so that FA can be easily obtained, so that FA can no longer need FA, so that FA can no longer need FA, so that it can be reduced One forwarded.
l Routing optimization. Mobile IPv6 defines the routing header such that CH can directly utilize routing headers to MH, so that routing is part of the mobile IPv6.
l Security function. The enhancement of security features is the significant improvement of IPv6 on IPv4. Mobile IPv6 uses the features provided by IPV6 in IPv6, while Mobile IP must be responsible for security issues.
The above mentioned is a single layer of terminal mobility solution, multi-layer composite mobility solution can be found [8], [9], mainly based on mobile IP and SIP network layers and application layer composite solutions [10] refers to the idea of composite solutions that use all layers contribute.
Personal mobility and conveyance mobility
Personal mobility means that users can use any terminal to access the same business through personal identity, and user access services is independent of the terminal, the network has the ability to identify and locate users, and the support for personal mobility is mainly used as a network. Business implementation. Universal Personal Communication (UPT, Universal Personal Telecommunication) is such a business that supports personal mobility, UPT users use a unique personal communication number to access any network and can span multiple networks and accept any type of call The personal communication number can be translated into the corresponding communication number and perform routing according to the user's request, and will come to the place specified by the user in the future. UPT implementation is generally based on smart network, UPT is also one of the main services supported by intelligent network [11]. Due to the characteristics and defects of the intelligent network itself, the UPT function is limited, and the support for personal mobility is mainly reflected in the telephone call class business, and the business of other emails is actually a business that supports personal mobility.
Session mobility refers to the user can hang a service session between different terminals during use, and the user can move between terminals during the service. Session mobility is actually reflected in N-ISDN. The N-ISDN terminal implemented as a supplementary service can carry the service to allow a call from one terminal from one terminal in a given access port. To another terminal. Of course, this session mobility is also a functional or applicable range.
Session Initiation Protocol (SIP, Session Initiation Protocol) is an application layer multimedia signaling protocol proposed by IETF. The session supported by SIP can be an Internet multimedia conference, telephone call or multimedia information flow allocation, which can be unicast, or group broadcast. SIP defines the establishment, termination, and modification process of the session, and the media control part is responsible for the session description protocol (SDP, Session Description Protocol). The SIP itself has the ability to support mobility, in addition to the expansion of the SIP is used to implement terminal mobility, SIP can be an important method for supporting personal mobility, session mobility. SIP support for personal mobility can be explained by the following example:
User B moves between the company and the residential, he posted his personal address outside Userb@corporation.com. And when he was at home, he sent Register messages to his company's SIP server (1), and put his residential address userb@Home.com as the forward address. And register (2) in the SIP server at the residential. There is a user uses a call to the userb@corporation.com, parsing Corporation.com to the company's SIP server IP address to the call to the Corporation.com (3) to the Corporation. SIP server corporation.com Check the user registration information, turn the call request to the SIP server home.com (4). The SIP server home.com checks the user registration information to turn the call request to the SIP user agent (5) of the user B. User B accepts a call request, the SIP user agent returns a call acceptance response to the SIP server home.com, and the SIP server home.com returns a call to the SIP server corporation.com (7), SIP server Corporation.com to the caller Usera@a.com Returns the call response (8). Direct sessions between users A and User B can be established later. The SIP server here includes a registration server and a proxy server.
SIP supports session mobility in the SIP session attribute adjustment and flexible message. With the SIP protocol, the initiator of the session mobility can notify the information such as the peer communication host to save the past target terminal from the existing terminal. At the same time, the peer communication host he will use the new terminal address and other information. This will complete the session switching, and the properties of the session, such as the media encoding type, and format, session occupation bandwidth, etc. will be adjusted and modified, and the smoothing of the session is guaranteed.
Other mobility
In addition to the terminal mobility, personal mobility, and session mobility of the terminal, mode mobility, AD HOC mobility, etc. Business mobility means that users can use business regardless of the network business providers accessible. Ad hoc mobility refers to the node mobility in the Ad hoc network because the Ad hoc network does not implement communication between nodes without any fixed basic network facility, so the Node mobility of the Ad hoc network has its own special. Mobility refers to the terminals to switch access networks between multiple communication modes, such as switching between GPRS and WLANs, and literature [12] analyzes the use of MOILE IP to provide mobility between GPRS and WLANs. Switching problem.
Support and research on mobility in the next generation network
The next generation network is not a new network, but based on the existing variety of network evolution, it is because the next generation of network is a variety of networks that are fused, so all-round mobility support is in the next generation network. It is possible and necessary. We believe that on the basis of current research on mobility, the next-generation network will focus on both directions below. 1) Support for various mobility such as end mobility, personal mobility, session mobility, and the like will be further enhanced and various mobility will be integrated to provide users with real seamless services. 2) The meaning of mobility further breaks through the next generation of networks will have a variety of voice, data, multimedia, etc. provided by the network operator and value-added business provider (VaSP, Value Added Service Provider). Diversified business form, terminal diversification, personalization of business use, etc., resulting in the generation of personal business environments, 3GPP defines personalized information for user business ordering and service, personal business environment can be used Or multiple user profiles to define [13]. Personal Business Environment As the end movement and personal movement requires corresponding movement, this mobility can be called personal business environment mobility, support for personal environment mobility makes the user's business environment change is limited to terminals and network capabilities. Not because of moving. Personal Business Environment Mobility is a new mobility that needs to be supported in the next generation network. Virtual Home Environment (Vhe, Virtual Home Environment) is a concept present in the next generation of mobile communication network services. ITU / IMT2000, UMTS Forum gives VHE definitions, 3GPP is defined as: "In which network of VHE users, no matter which terminal, no matter where it is, it can always feel the same Personalized features, user interface and business, and proposes VHE as a service providing method on the next generation of mobile communication system UMTS [14]. Vhe supports personal business environment mobility, the personal business environment will move between networks and terminals, and Vhe also contains terminal mobility, personal mobility, session mobility, etc., so Vhe is the next generation network, especially mobile communications. Research focus of mobility support in the network. Current international and VHE-related major research projects include: 1) the EU-funded IST (Information Society Technology) Program VESPER (Virtual home Environment for Service PErsonalization and Roaming users); 2) the EU-funded ACTS (Advanced Communications Technologies and Services ) Plan project Cameleon (Communication Agents for Mobility Enhancements in a logical environment of open networks); 3) European Telecommunication Strategic Planning and Research Association (EURESCOM) supported project P920 "UMTS NetWork aspects". Through the study of Vhe, we believe that the key to realizing VHE is the standardization of the terminal business executive environment, and the distributed storage management of User Profiles, the three aspects of the adaptation of the media. VHE supports the mobility of personal business environment is also reflected in these three aspects. The standardization of the terminal business execution environment makes the user's personal mobility is further enhanced, providing a foundation for personal business environments in different terminals.
User profiles is the information definition of personal business environment, mainly including user basic information (name, gender, user ID, etc.), user interface related information (terminal screen font, language settings, etc.), business-related information (user favorite business List, business status), network related information (network configuration, network capabilities, etc.), user terminal capabilities (screen size, screen resolution, etc.). User profile distributed storage in the network, terminal, VASP, whether the user uses the network and what terminal, guarantees that the user can access user profiles and maintain the synchronization of USER Profiles. The adaptation of the media is to ensure that the media stream of the business can accommodate the mobile phone between users and terminals, and the business environment can be smooth and not interrupted. The implementation of VHE has not been standardized, and key technologies that may be applied include Camel, Mexe, SAT / USAT, PARLAY / OSA, etc. CAMEL (CUSTOMIZED Application for Mobile Network Enhanced Logic) is a suggestion that solves the mobile communication network and intelligent network interconnection, and Camel provides a mechanism for the same GSM service as the home network while achieving roaming. MEXE (Mobile Execution Environment) is a technology that provides a standard execution environment on the user terminal. SAT / USAT is a technology for providing standard execution environments for business logic stored on SIM or USIM. With Mexe / SAT / USAT technology, business logic with specific terminals can be downloaded to the terminal and executed there. PARLAY / OSA is an API specification for open network resources and capabilities, allowing the upper application to secure access to network resources and capabilities through the API, and the business based on PARLAY / OSA API is independent of the specific bearer network. References [1] D.a.maltz and P.Bhagwat, Msocks: an Architecture for Transport Layer Mobility, In Proceedings of infocom, 1998
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[13] 3GPP TR 21.905 V6.2.0 (2003-03), Technical Specification Group Services and System Aspects; Vocabulary for 3GPP Specifications, Release 6
[14] 3GPP TR 22.121 V5.3.1 (2002-06), Technical Specification Group Services and System Aspects; Service Aspects; The Virtual Home Environment, Release 5
