t voice call setup delay can be quite significant causing degraded end-user experience. VoLTE requires new core network, that is, IMS and new interoperability in terms of SRVCC handover between the LTE packet switched voice and target system CS voice. SRVCC handover triggering points need to be carefully designed in order to maintain the high voice quality, low handover delay and high success rates. References [1] 3GPP TS 23.221, 'Technical Specification Group Services and System Aspects; Architectural Requirements', v.9.5.0, December 2012. [2] 3GPP TS 23.272, 'Technical Specification Group Services and System Aspects; Circuit Switched (CS) Fallback in Evolved Packet System (EPS); Stage 2', v.9.14.0. [3] M. Poikselkä, H. Holma, J. Hongisto, J. Kallio, and A. Toskala. Voice over LTE (VoLTE), Wiley (2012). [4] A. Catovic, M. Narang, A. Taha, 'Impact of SIB Scheduling on the Standby Battery Life of Mobile Devices in UMTS', Mobile and Wireless Communications Summit, 2007, 16th IST, IEEE, 2007. [5] 3GPP TS 24.008 Mobile radio interface Layer 3 specification; Core network protocols; Stage 3V8.6.0, June 2009. [6] ITU Recommendation P.863, September 2014, Retrieved from http://www.itu.int/rec/T-REC-P.863 (accessed February 2015) [7] POLQA, September 2014, Retrieved from www.polqa.info/ (accessed February 2015) [8] The Internet Engineering Task Force (IETF), RFC3550, May 2003, Retrieved from www.ietf.org (accessed February 2015) [9] 3GPP TS 23.216, 'Single Radio Voice Call Continuity (SRVCC); Stage 2', v.10.6.0, June 2013. [10] 3GPP TS 24.237, 'Technical Specification Group Core Network and Terminals; IP Multimedia (IM) Core Network (CN) Subsystem IP Multimedia Subsystem (IMS) Service Continuity; Stage 3', v.11.13.0, December 2014. Inter-layer Mobility Optimization Jari Salo and Jussi Reunanen Introduction Inter-layer Idle Mode Mobility and Measurements Inter-layer Connected Mode Measurements Inter-layer Mobility for Coverage-Limited Network Inter-layer Mobility for Capacity-Limited Networks 15.6 Summary References 15.1 I