A recent spate of VoLTE launches has put the technology under the spotlight, but its lengthy absence on any meaningful scale – with the possible exception of South Korea – may seem troubling to some industry watchers.
When the original LTE specifications were drawn up, the circuit-switched (CS) domain used in 2G and 3G was dispensed with in favour of an all-IP environment. All well and good, but no provision was made as to how voice and texting – still the two mainstays of a mobile operator’s business – would be delivered over a spanking new all-IP data network.
Circuit-switched fallback (CSFB) is a possible ‘interim’ solution that WCDMA operators can deploy, but it’s hardly ideal. Lengthier call set-up times of around 1-2 seconds probably won’t upset high-spending LTE customers, but call-set up times may be longer if there’s no 3G signal and the call is then directed onto 2G. The 4G voice experience, in such scenarios, is worse than 3G. (more…)