Voice Evolution in 4G Networks

This chapter describes the main practical aspects for supporting voice services over LTE. An end‐to‐end approach is presented by outlining the requirements in the LTE radio access, EPC, the IMS core, and the voice application server. This chapter includes a description of the radio features for voice, how QoS is provisioned to support conversational speech, IMS features for voice telephony, media handling, roaming architecture, and how to take advantage of any existing circuit‐switched infrastructure. The main topics included in this chapter are voice options for LTE, the VoIP protocol stack, IMS single radio voice call continuity (SRVCC). In addition, key VoLTE features are presented: semi‐persistent scheduling (SPS), TTI bundling, VoIP with C‐DRX, robust header compression (RoHC), and VoLTE Vocoders and de‐jitter buffer. The chapter concludes with deployment considerations for VoLTE with examples of the advantages of different deployment scenarios.