Wikipedia
PDC-EFR
PDC Enhanced Full Rate is a speech coding standard that was developed by ARIB in Japan and used in PDC mobile networks in Japan. The carriers use one of those codecs as PDC-EFR: CS-ACELP 8 kbit/s (aka NTT DoCoMo Hypertalk) and ACELP 6.7 kbit/s (aka J-PHONE Crystal Voice).
The PDC-EFR CS-ACELP uses G.729. The PDC-EFR ACELP is compatible with the AMR mode AMR_6.70.