Last night at CES 2013, T-Mobile CTO Neville Ray announced that AMR-WB (Adaptive Multi Rate Wideband) was enabled on the operator's network, instantly allowing capable phones to place higher quality voice calls over the cellular network between T-Mobile customers. This announcement makes T-Mobile the first GSM/UMTS based network in the US to enable AMR-WB, but not the first operator in the US to deploy "HD Voice," as Sprint has been rolling out 1x-Advanced's EVRC-NW (EVRC-Narrowband Wideband) wherever their network modernization and LTE upgrades are.
HD Voice enables calls with a much wider dynamic range. AMR-WB is a direct successor to AMR-NB (narrowband) and offers higher frequency bandwidth of up to about 8 kHz (16 kHz sampling) as opposed to AMR-NB's 4 kHz. I'm unclear what bitrate or coding mode T-Mobile US is using, however I'd be willing to suspect that T-Mobile has probably gone for enabling the full AMR-WB range of bitrates. I have to say I'm impressed with T-Mobile US' constant leadership over AT&T with UMTS upgrades in the US. AT&T currently runs AMR-NB at 5.9 kbps for comparison, not even the full allocation AMR-NB bitrate. Update: It's possible that T-Mobile is using the 12.65 kbps AMR-WB bitrate.
This upgrade was made active last night, and all mobile-originated and mobile-terminated calls on T-Mobile between phones that support AMR-WB should now use the mode, subject to other factors that normally affect multirate codecs such as coverage profile and network load. T-Mobile has called out the Samsung Galaxy S 3 and HTC One S as being examples of two such phones that definitively already include AMR-WB support, although any phone that exposes the capability on network attach should work just fine.
I placed a number of calls between T-Mobile users last night to try and gauge any perceptible difference. I've previously heard AMR-WB demos and run loopback calls on the Anritsu base station emulator, and there is a perceptible difference. I originated a call on a Nexus 4 and terminated it on a Nexus 4 with both on T-Mobile, which sounded excellent, and then between an iPhone 5 (attached to PCS WCDMA here in Las Vegas) and a Nexus 4, which also sounded very different than an AT&T AMR-NB originated and terminated call. I need to do more testing back home, but T-Mobile's claims that this is live right now and working seem credible, calls sounded crisp and much more intelligible than some of the AMR-NB calls I've been on.
Source: T-Mobile
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