VoWiFi may at first glance appear very similar to Further, VoWiFi can reduce cost for an operator as it VoIP, but there are two critical differences. Firstly it is enables traffic to be off-loaded to another network. a network operator managed and controlled service, The cost savings could be significant: a US carrier with which, for users, should mean that the call is less likely 15 percent VoWiFi penetration and a national footprint to be dropped. So other activity on the same network is could enjoy spectrum and capacity savings per year of 352 less likely to disrupt a voice call than would be the case approaching half a billion dollars . on a VoIP call, which is carried on a best efforts basis. For carriers, being in charge of the service also means Long term, most operators will likely launch both that they have more control over the revenue stream. services as a natural evolution towards IP-based-only Secondly, VoWiFi offers native calling: there is no need communication. However, short term some carriers to open an app to make or receive calls. A VoIP call can may decide to launch one of the two services first. only be received when that specific app is open. The decision will likely be influenced by three main factors: the potential cost savings, the need to improve VoWiFi extends reach at a relatively low marginal cost. indoor coverage, and the customers’ interest in Operators need to deploy an IP multimedia subsystem enhanced communication services. (IMS). If they already have VoLTE, this will already have been paid for. In some regards VoWiFi may even reduce operator costs, as calls placed on a smartphone would be carried over the consumer’s broadband network, freeing up some cellular capacity. Bottom line 353 Operators need to weigh up benefits against the cost of deploying an IMS . One analyst firm has calculated that the cost of deploying and operating an IMS solution could be up to $10 million with a VoLTE subscriber base of around 2.5 million. If the base rose to 75 million, there would be significant 354 economies of scale, with the annual operating cost estimated at about $45 million . In the short term, device and network interoperability may be a barrier for uptake. VoWiFi and VoLTE support varies by handset, and each carrier has enabled a different set of these devices. In some cases, VoWiFi may be supported on a consumer all-you-can-eat tariff, but not on the enterprise tariff. Furthermore, packet-based calls may require calling and called devices to have the same software version enabled. For VoLTE, both parties need to have compatible handsets, be in 4G range, be subscribed to 4G (rather than just having 4G capability), and, for a period of time, be on the same 355 network . Carriers should also bear in mind the potential cost implications for incorporating emergency service support (providing a user’s location) into VoLTE and VoWiFi. The IMS signaling system needs to support the Emergency IMS subsystem to ensure that the call goes through. Consumers have high expectations for voice quality: operators should only launch VoLTE and VoWiFi services when the service is stable. The network should be configured so as to prioritize voice packets. Real-time monitoring and auctioning of network performance KPIs such as bit-rate, latency, jitter and packet loss are also recommended. Operators should include a fallback for non-native VoLTE calls, or 356 calls in areas where 4G coverage is lacking or limited . Operators should also advise on some of the quirks of the service at this stage: for example a VoWiFi call cannot roam onto a circuit-based 2G or 3G call when out of WiFi range: it can only move onto a VoLTE network. Carriers should determine how best to advertise the two services so that consumers value the quality of voice call and perceive the enhancements provided as value added services. This could counteract the declining trend of smartphone users not making phone calls and moving to OTT alternatives. 58