G.728 is an ITU-T speech coding  standard that uses Low Delay Code Excited Linear Prediction (LD-CELP) operating at 16 kbit/s compression at a sampling rate of 8,000 samples per second. The algorithmic coding delay of G.728 is 0.625 ms. G.728, when compared to G.726 delivers close to the same voice quality but uses only one-half the bandwidth.

See G.7xx for more information on how these standards are used in telephony networks.
See also LD-CELP.

Enterprise VoIP Planet
The IT Manager's Guide to Voice over IP

ITU Recommendation G.728
Coding of speech at 16 kbit/s using low-delay code excited linear prediction

Six Steps to Getting Your Network Ready for Voice over IP
Using low bandwidth CODECs helps reduce bandwidth requirements however due to the overhead of IP, UDP and RTP protocols, such reduction is limited.

The International Telecommunication Union
The International Telecommunication Union is an international organization within which governments and the private sector coordinate global telecom networks and services. This home page offers numerous links to highlights and current topics, standardization, radiocommunication, telecommunication, and general secretariat sectors.