Apple appears to be gearing up for high-definition voice-over-LTE (HD VoLTE) support in future mobile products
The company is currently advertising for a cellular systems protocol engineer, calling for experience with "VoLTE" and "IMS." Other positions are calling for experience with the Session Initiation Protocol (SIP) protocol.
VoLTE uses SIP to initiate the 4G calls, which are transmitted in data packets, with the IP Multimedia Subsystem (IMS) in the core network controlling the call session. There's a useful primer on how this all works here.
Apple is also looking for a senior baseband engineer to work on "cutting-edge" audio for its devices, which will include the Adaptive Multi-Rate Wideband (AMR-WB) speech compression codec, which is part of the VoLTE specification. The engineer will help to "implement, port, and deploy AMR-WB, AMR-NB, CELP, EVRC-B, EVRC, EVS Vocoders, and Jitter Buffers on Mobile devices," according to the ad.
The VoLTE timing could make sense for the iPhone 6, which is expected to be unveiled in September, since Apple's largest US carrier partners are launching limited service now or are expected to go live with VoLTE on their networks later this year.
So far, 66 service providers spanning 35 countries have invested in VoLTE studies, trials or deployments, with 10 operators in Hong Kong, Japan, Singapore, South Korea and the US having actually launched an HD VoLTE service. (See VoLTE Gains Velocity: GSA.)
VoLTE specialists Mavenir Systems Inc. recently stated that there are 92 VoLTE-capable devices on the market now, some of which will require a software upgrade to use the technology. "Apple has rumored that iPhone 6 and iOS 8 might both support VoLTE," said Mavenir CEO Pardeep Kohli on an earnings call, according to a Seeking Alpha transcript. "This will be the first Apple phone to support VoLTE, and its introduction this fall is expected to further the progress of VoLTE."
Apple typically doesn't reveal new features of its devices ahead of launch.
— Dan Jones, Mobile Editor, Light Reading