Research On Key Techniques Of User Mobility Support In Satellite Networks

In recent years,the vigorous development and convergence of network technologies and satellite technologies have created satellite network,a new type of network system.The integrated network based on satellite network,which has the advantages of wide coverage,unconstrained deployment and access,has become an important part of the future global communication infrastructure.On the other hand,the current users of the Internet are undergoing profound changes from fixed and wired users to mobile and wireless users: the number of mobile users and the traffic generated by mobile users have greatly exceeded that of wired users.In this context,it is of profound practical significance to study the key technologies that adapt to the characteristics of the satellite network and essentially support the user mobility.The research on user mobility support technology of current satellite networks mainly refers to related technologies of terrestrial wireless Internet.These techniques usually use an identifier to simultaneously represent the user's identity and the user's current network location,which adversely affects the user's high mobility(fixed identity,frequently changing network locations).In addition,the classic user mobility support technologies,such as mobile IP,shield the user's movements with a stationary home agent,but potentially cost the routing expansion,poor scalability,and poor robustness.Therefore,in the design of terrestrial next-generation wireless networks,the identifier-location separation technology is widely believed to be helpful to provide users with high mobility support essentially.Towards the special background of satellite networks,this paper is based on the idea of identifier-location separation and conducts in-depth research on the key technologies involved.The main research contents include:(1)A satellite network architecture based on identifier-location separation is proposed.The architecture adopts the idea of identifier-location separation,which clearly separates the user's identifier from its network location,and essentially supports the user's mobility.When the user initiates a connection with the correspondent node,the mapping resolution system is first queried to obtain the identifier-location binding of the destination.Then the packets are encapsulated and entered into the satellite network for routing.The support for user mobility is also based on the identifier-location separation strategy.The user's movement is tracked by the mapping resolution system,and the latest network location after the user's movement can be obtained by querying it.In addition,for the control plane,an efficient control framework based on single-layer heterogeneous satellite networks is also proposed.Different from the traditional GEO satellite-based multi-layer satellite control framework,the theoretical analysis and performance evaluation prove that the framework can reduce the transmission delay of control messages,improve the control network capacity,and enhance the reliability of the control network.(2)An indirect binding method based on virtual attachment point is proposed.The relative movement between satellite network attachment points and terrestrial users is a special phenomenon in the LEO satellite network.The use of terrestrial mobile IP technology and unmodified identity-location separation technology to provide user mobility support will result in a large number of binding update messages,potentially affecting the performance of such user mobility support technologies.By introducing the concept of virtual attachment points,the relative movement of satellite and user can be logically divided into independent movements.That is,the binding of the satellite and the user is divided into the binding of the satellite and the virtual attachment point and the binding of the user to the virtual attachment point.Because the orbit movement of the satellite is deterministic and predictable,the virtual attachment point can be time-varyingly embodied by different physical satellites.The binding of the user and the virtual attachment point adopts the identifier-location separation strategy and is maintained by the mapping resolution system.Theoretical analysis and performance evaluation prove that the proposed scheme is greatly reduced in terms of the update overhead compared to the mobile IP-based scheme.Therefore,it can provide important support for the identifier-location separation in satellite networks.(3)A vertical binding update method based on a multi-layer service area is proposed.The indirect binding method based on virtual attachment point can significantly reduce the frequency of binding updates,but potentially introduce a new problem called the ”ping-pong effect”,that is,the user's round-trip movement at the boundary of the service area will produce a large number of additional binding updates.Therefore,further optimization is needed to alleviate the binding updates caused by ping-pong effect.Based on the support of mega-constellations,the structure of a multi-layer service area can be constructed.By staggering the multi-layer service domains in a“half-coverage”manner,users can be rebound to the center of the service area of another layer after the vertical binding update.Therefore,the time when the next binding update occurs may be delayed to achieve the purpose of reducing the frequency of binding update.The theoretical analysis and performance evaluation prove that the proposed multi-layer scheme is further reduced in terms of the binding update frequency compared to the single-layer scheme,and has a mitigated effect on the frequent binding updates caused by the ping-pong effect.(4)A mapping resolution system design for high-mobility satellite networks is proposed.The existing mapping resolution systems have the disadvantages of passive caching,static placement,long query latency,and large update overhead in supporting user mobility of satellite networks.Therefore,it is necessary to design a mapping resolution system achieving goals such as low query latency,low update cost,and high availability.The proposed mapping resolution system mainly includes the replica placement controllers and the mapping resolution servers.The replica placement controllers are responsible for determining the number and locations of the replicas,while the mapping resolution servers are responsible for responding to the user's mapping resolution request.The replica placement controllers use the dynamic replica placement algorithm to determine the number of replicas to balance the query latency and update overhead,and place the limited replicas to the areas with high demand for that mapping in a demand-driven way.Theoretical analysis and performance evaluation prove that the proposed scheme has lower query latency and lower update overhead.