As some MNOs prepare for 5G, many others have not even deployed voice over LTE (VoLTE) yet. While LTE addressed many of 3G’s shortcomings in the mobile data experience, it dropped the ball when it came to voice. The move to an IP network meant traditional circuit-switched voice could not be supported on 4G, but the complexities of deploying VoLTE are significant, requiring investment in an IMS (IP Multimedia Subsystem) and extensive end-to-end optimization to deliver an experience that matched, let alone surpassed, that on 2G and 3G. The result was that most operators moved slowly towards VoLTE, and some of them – particularly smaller MNOs without an IMS, and with no urgent need to refarm 2G/3G spectrum yet –…