One of the big, underrated challenges of 4G deployment was migrating cellular voice services to the IP network. Voice over LTE (VoLTE) proved difficult and expensive to deploy and optimize, requiring an IP Multimedia Subsystem (IMS) for which the ROI case was often dubious, given the way that voice and messaging usage was quickly shifting to Internet services. Yet few operators found themselves able to abandon voice and SMS altogether, nor to keep circuit-switched fallback in place for ever to support voice on the old 2G/3G systems. Now, we see the start of implementation of Voice over 5G (Vo5G) – easier this time, provided operators have the IMS in place, but even harder to justify in commercial terms. …