Support of E-UTRAN-HRPD Inter-RAT SON as specified in TS 36.413 makes use of the RIM procedures described in clause 5.15 of TS 23.401. The architecture is depicted in Figure 17.1-1. The interfaces used are the S1 and the S121 interfaces. An eNodeB is addressed by the Target eNodeB Identifier. An HRPD Access Network is addressed by HRPD Sector ID as defined in TS 29.276. For messages transferred between E-UTRAN and HRPD Access Network, the source access network node sends a message to its MME including the source and destination addresses. The MME decides, which access network node to send the message to, based on the destination address. The MME performs relaying between S1 and S121 messages as described in TS 36.413 and TS 29.276.