An updated hacked carrier profile for AT&T unlocks early access to HD Voice for the iPhone 4S and 5, among other features, says developer iTweakiOS. The update
is moreover said to enable faster HSPA speeds on the iPhone 4S, up to 21Mbps down, as well as early access to disaster and Amber alert systems. Troubleshooting efforts deal with unstable HSPA+ connections and iPad users losing signal entirely with a previous update.
AT&T has previously announced plans to turn on HD Voice, but without providing any details beyond a 2013 launch window. The technology is an Apple-branded version of wideband audio, which improves the quality of voice calls. HD Voice was first announced alongside the iPhone 5, but only a relative handful of carriers have thrown their support behind it, such as T-Mobile