Handoff And Location Management Technology In Satellite-Terrestrial Integrated Wireless Networks

At present,the terrestrial mobile communication system is difficult to meet the communication coverage requirements in remote areas and natural disaster scenarios,and the communication vision of seamless airspace-ground-sea coverage cannot be realized.To this end,6G proposes the concept of satellite-terrestrial integration.Drawing on the terrestrial mobile communication system to enhance satellite communication,satellite-terrestrial integrated wireless networks can greatly expand the signal coverage of base stations on the basis of terrestrial networks,so as to realize global three-dimensional ubiquitous communication.As the key technologies in the field of mobile communication,handoff and location management directly impact user service experience and network operation efficiency.However,due to the high-speed moving and wide coverage characteristics of low-orbit satellites,in satellite-terrestrial integrated wireless networks,directly applying handoff and location management schemes of terrestrial communication networks will lead to problems,such as frequent handoff,inaccurate handoff trigger occasion,and large signaling overhead of location management.To this end,this paper carries out research on handoff and location management technology suitable for satellite-terrestrial integrated wireless networks.The main work and innovations are as follows:In terms of handoff management,there are many problems,such as high-speed satellite movement leading to frequent handoff,lag in user signal strength measurement,handoff failure caused by inaccurate handoff occasion,large handoff delay,and incorrect handoff object selection.In view of the above,a link handoff trigger scheme based on ephemeris-user location prediction and link handoff decision scheme based on multiple information are proposed.First,the current link remaining time based on the ephemeris and user location information is calculated as the handoff trigger condition,and the handoff link is selected based on the multi-attribute judgment,which takes the satellite elevation angle,the link remaining time,satellite idle resource and the link handoff delay into account.In addition,faced to on-board transparent forwarding and on-board processing architecture,the handover implementation process is sorted out.Finally,the handoff performance of the proposed scheme and multiple comparison schemes is evaluated through system simulation,and the proposed effectively improves the handoff success rate and reduces the inter-gNB handoff number,thereby reducing the handoff signaling cost.Meanwhile,the impacts of parameters such as minimum visible elevation angle,available satellite resources,and handoff triggered threshold on handoff performance are analyzed.In terms of location management,it is difficult to balance the location update and paging cost,and the total location management cost is large.Therefore,a location management solution is proposed,which integrates spatial and temporal dimensions,and perceives user movement and service characteristics.Specifically,the space-based location update trigger condition refers to moving out of the stationary tracking area list relative to the ground or crossing multiple tracking areas of satellite beams.The time-based location update is triggered by the location update timer.Under different location management schemes,the spherical tracking area,the relative movement of the user and the tracking area,and the arrival of user services are modeled.And the signaling cost of the location management is theoretically derived by the embedded Markov chain.Then,its accuracy is verified by simulation.Meanwhile,the proposed schemes reduce the signaling cost compared with other location management schemes.Further,the impacts of relevant parameters on the proposed solution performance are analyzed via simulation.Based on the simulation results,the appropriate tracking area division method is analyzed,along with the optimal spatial and time thresholds of the location update scheme.In summary,this paper studies the handoff and location management technology in satellite-terrestrial integrated wireless networks.It provides certain solution support for the engineering implementation of handoff and location management in satellite-terrestrial integrated wireless network.