ver to UTRAN (or GERAN) is included. The handover message also includes configuration for ciphering in the target network. Once UE has received the handover command, it will not acknowledge the reception of the message to the LTE network, but will tune to the target network frequency immediately and synchronizes with it. Let us assume here that the target network is UTRAN. Once the UE has synchronized with the target network it will send a Handover Complete message to UTRAN. This message is already ciphered but not yet integrity protected, but contains the information for enabling integrity protection. After UTRAN receives the Handover to UTRAN Complete message from the UE it sends Security Mode Command to the UE in order to activate integrity protection for CS domain and it also sends Relocation Complete/Handover Complete message to the target MSC, which then sends SES to the MSC server. The speech circuit gets connected in MSC Server. After UE has processed the integrity protection information it should now be able to receive and transmit voice. UE responds with security mode complete message; the new ciphering key and Hyper Frame Number are used to calculate the RRC sequence number. MSC server sends SRVCC PS to CS Complete Notification message to the source MME which acknowledges with SRVCC PS to CS Complete Acknowledge message. The MME then deactivates the voice bearer with Delete Bearer Command message to S-GW/P-GW and sets PS-to-CS handover indicator. LTE Small Cell Optimization Establishing Connection with PS Domain and Releasing the Resources from EUTRAN At this stage the UTRAN sends Mobility Information message to provide CN system infor- mation of the PS domain. Typically also a Routing Area Update is performed and if the HLR is to be updated because the IMSI is authenticated but unknown in the VLR, the MSC Server performs a TMSI reallocation towards the UE after which the MSC Server performs a MAP Update Location to the HSS/HLR. In case the security context was not transferred, UTRAN performs Authentic