Research Of Vertical Handoff In Heterogeneous Network Based On SCTP

With the rapidly growth of mobile communications industry, the development of a variety of emerging wireless network access technology meets the different distance, speed and service level of communications needs. To meet the people's expanding ubiquitous communication needs, mobility management technology, which could provide the seamless service in heterogeneous wireless networks and support seamless roaming and vertical handoff in heterogeneous networks, must be addressed in the future of all IP architecture next-generation networks. IETF Signaling Transport (IETF SigTran) working group developed SCTP (Stream Control Transmission Protocol) technology standard, and its multi-homing feature provides transport layer solutions to vertical handoff for heterogeneous network. SCTP is running on infrastructure network without need for additional support services, and it keeps transparent interfaces to the upper and lower service. For these advantages, it gives the ideal solution to the seamless operations for the implementation of the heterogeneous network.In this new field, the most current domestic and abroad research is still on the theory and simulation stage. Research for the promotion and optimization on SCTP in practical network still lags behind, which is shown in the following aspects:(1) Test-bed platform is still required for optimization of handoff execution process and handoff decision design in practical physical network. (2) Path bandwidth is required as important parameters in some transport layer congestion control mechanisms; optimization of handoff execution process and handoff decision design, but the typical SCTP protocol stack implementation is still lack of path bandwidth estimating mechanism. (3) NAT (Network Address Translation) devices, normally existing in the current IP network, are mostly not available on the SCTP protocol support, resulting in SCTP packet transmission blocking problems, which affect the promotion of SCTP protocol.In this thesis, the source code of Linux kernel SCTP stack is modified to achieve the above solution to the problem. The results of this thesis could make a positive contribution to the promotion and optimization in heterogeneous SCTP-based network solutions in the practical network system.Chapter 1 states development background of vertical handoff for heterogeneous network, analyze and discuss the strengths and weaknesses of solutions in various network layers, and then states the main contributions and organizational structure of this thesis. Chapter 2 describes main background knowledge and key issues of vertical handoff for heterogeneous network and SCTP protocol. Chapter 3 discusses the SCTP-based test bed for heterogeneous network, especially on its architecture design and function implementation. Chapter 4 analyzes the two available kinds of bandwidth estimation model in SCTP, and implements them as expansion of LKSCTP projects. Chapter 5 analyzes and solves the three problems in SCTP packets traversing through the NAT device, and give implementations in the Linux platform. At last, the full thesis is concluded, and the future work is proposed.