ers (avg), normal day Figure 13.59 Average and maximum RRC-connected users during event day and normal day with the increase ratio between normal and event day. Hourly statistics is used for the highest loaded cells within the mass event cluster LTE Small Cell Optimization PDCCH capacity limited. Typically the cells become end-user throughput limited and that can be improved only by performing physical layer optimization or adding more cells or increasing the carrier bandwidth or adding more carriers. It should be, however, noted that adding extra capacity does not improve spectral efficiency but rather only the physical layer optimization can improve the spectral efficiency. Correct parameter set during mass event is also extremely important for good performance and especially the uplink power control should be properly set and all unnecessary signalling should be avoided as much as possible. References C.U. Castellanos, D. L. Villa, C. Rosa, K. L. Pedersen, F. D. Calabrese, P.-H. Michaelsen, J. Michel, 'Performance of Uplink Fractional Power Control in UTRAN LTE', IEEE Vehicular Technology Conference (VTC), Spring 2008. [2] 3GPP TS 36.213, 'Physical Layer Procedures', v.10.9.0, 2013. [3] 3GPP TSG RAN R1-072261, 'LTE Performance Evaluation - Uplink Summary', May 2007. [4] H. Holma and A.Toskala. LTE for UMTS - OFDMA and SC-FDMA Based Radio Access, John Wiley & Sons (2009). [5] 3GPP TR 37.868, 'RAN Improvements for Machine-Type Communications', v.1.0.0, October 2011. [6] 3GPP TSG RAN R1-072444, 'Summary of Downlink Performance Evaluation', May 2007. [7] F. Capozzi, D. Laselva, F. Frederiksen, J. Wigard, I. Z. Kovacs, and P.E. Mogensen, 'UTRAN LTE Downlink System Performance Under Realistic Control Channel Constraints', IEEE Vehicular Technology Conference Fall (VTC 2009-Fall), 2009. [8] 3GPP TS 36.331, 'Radio Resource Control (RRC); Protocol Specification', v.10.11.0, 2013. VoLTE Optimization Riku Luostari, Jari Salo, Jussi Reunanen and Harri Holma 14.1 Introduction Voice Options for LTE Smartphones Circuit Switc