VoLTE/CSFB Call Setup Delay and Handover Analysis

This chapter provides comprehensive analysis for call setup delay including circuit‐switched fallback (CSFB) and voice over LTE (VoLTE) with different scenarios including stationary and mobility scenarios, and handover analysis including single radio voice call continuity (SRVCC) in terms of data interruption time. Firstly, the CSFB call flow and relevant call setup KPIs are established and analyzed in detail for the redirection and packet system (PS) handover strategies. The second contribution is the analysis of the VoLTE call setup delay in a comparative manner with CSFB. VoLTE call setup involves different stages where each stage contributes to the call setup latency. Latency reductions may be achieved by protocol enhancements as well as shortened transmission time intervals (TTIs). The chapter also provides use cases and issues related to call setup and handover, and recommendations and resolutions for these cases.