Practical Performance Analyses of Circuit Switched Fallback (CSFB) and Voice over LTE (VoLTE)

Abstract— IP Multimedia Subsystem (IMS) is a framework for delivering all-IP based services. Voice via IMS has been defined as a possible solution from 3GPP Release 5, prior to LTE. However, the cost and immediate need of IMS services prevented operators from migration to IMS-based services, especially with the widely presence of Circuit Switched (CS) services offered in GSM and UMTS networks. CS Fallback (CSFB), introduced in 3GPP Release 8, enables the support of voice service without IMS. This is the common deployed scenario for many exiting LTE networks. Voice over LTE (VoLTE) is compulsory to offer rich communication services (RCS) via IMS in addition to improving the performance of the already deployed CSFB voice solution. However, CSFB and VoLTE are still deployed concurrently, where operators can gradually roll out an LTE/IMS system while still supporting 2G/3G fallback mechanism. It is therefore important to benchmark the performance of both solutions, highlight the deployment challenges and study the impacts on the end-user experience. This paper provides performance analysis, deployment challenges, and comparisons between these voice solutions. The paper presents practical performance analysis including end-to-end assessment of call setup delay in different radio conditions, main challenges impacting the in-call performance as well as performance aspects of Single Radio Voice Call Continuity (SRVCC) and its evolution releases.IEEE Explorer

Authors: 

Ayman Elnashar, Mohamed A. El-Saidny, Mohamed Mahmoud