一, X2 interface general principles
? ? 1, the X2 interface should be open
? ? 2, the X2 interface shall support the exchange of signalling information between two eNBs, in addition the interface shall support the forwarding of PDUs to the respective tunnel endpoints
? ? 3, from a logical standpoint, the X2 is a point-to-point interface between two eNBs within the E-UTRAN, A point-to-point logical interface should be feasible event in the absence of a physical direct connection between the two eNBs
二, X2 Function?
? ? 1, Intra LTE-Access-System Mobility Support for ECM-CONNECTED UE
?? ?? ? 1), Context transfer from source eNB to target eNB;
?? ?? ? 2), Control of user plane transport bearers betwen source eNB and target eNB;
?? ?? ? 3), Handover cancellation? ? (交接取消)
?? ?? ? 4), UE context release in source eNB
?? ?? ? 5), Dual Connectivity? ? ? ? (雙連通性)
?? ?? ? 6), Handover Success Indication
?? ?? ? 7), Conditional Handover cancellation? (有條件的交接取消)
? ? 2, Load Management
? ? 3, Inter-cell Interference Coordination? ? (小區(qū)間干擾協(xié)調(diào))
?? ?? ? 1), Uplink Interference Load Management
?? ?? ? 2), Downlink interference avoidance? ? ?(下行干擾避免)
? ? 4, General X2 Management and error handling function
?? ?? ? 1), Error indication
?? ?? ? 2), Reset
? ? 5, Application level data exchange between eNBs
? ? 6, Trace functions
? ? 7, Data exchange for self-optimisation
? ? 8, EN-DC? (MeNB and en-gNB to support Dual Connectivity)
三, X2AP Functions
? ? 1, Mobility Management.
? ? 2, Dual Connectivity
? ? 3, E-UTRA-NR Dual Connectivity
? ? 4, Load Management
? ? 5, Reporting of General Error Situations
? ? 6, Resetting the X2
? ? 7, Setting up the X2
? ? 8, eNB Configuration Update
? ? 9, Mobility Parameters Management
? ? 10, Mobility Robestness Optimisation
? ? 11, Energy Saving
? ? 12, X2 Release
? ? 13, Message Transfer
? ? 14, Registration?
? ? 15, Removing the X2
? ? 16, Inter-eNB UE Context Retrieval
? ? 17, Secondary RAT Data Usage Report
? ? 18, E-UTRA-NR Spectrum Sharing
? ? 19, EN-DC Configuration Transfer
? ? 20, EN-DC Load Management
? ? 21, UE Radio Capability ID Mapping
