  Voice over Long-Term Evolution (VoLTE) has been witnessing a rapid deployment
by network carriers worldwide. During the phases of VoLTE deployments, carriers
would typically face challenges in understanding the factors affecting the
VoLTE performance and then optimizing it to meet or exceed the performance of
the legacy circuit switched (CS) network (i.e., 2G/3G). The main challenge of
VoLTE service quality is the LTE network optimization and the performance
aspects of the service in different LTE deployment scenarios. In this paper, we
present a detailed practical performance analysis of VoLTE based on
commercially deployed 3GPP Release-10 LTE networks. The analysis evaluates
VoLTE performance in terms of real-time transport protocol (RTP) error rate,
RTP jitter and delays, block error rate (BLER) in different radio conditions
and VoLTE voice quality in terms of mean opinion score (MOS). In addition, the
paper evaluates key VoLTE features such as RObust Header Compression (ROHC) and
transmission time interval (TTI) bundling. This paper provides guidelines for
best practices of VoLTE deployment as well as practical performance evaluation
based on field measurement data from commercial LTE networks.
