Coding Strategies and Standards - Digital Speech: Coding for Low Bit Rate Communication Systems - page 13

Table 2.2 ETSI speech coding standards for GSM mobile communications
Bit rate Noise Delay

Speech coder (kb/s) VAD reduction (ms) Quality Year

FR (RPE-LTP) 13 Yes No 40 Near-toll 1987

HR (VSELP) 5.6 Yes No 45 Near-toll 1994

EFR (ACELP) 12.2 Yes No 40 Toll 1998

AMR (ACELP) 12.2/10.2/7.95/ Yes No 40/45 Toll 1999

7.4/6.7/5.9/ ∼ Communi-

5.15/4.75 cation

interference reduction as well as battery life time extension for mobile com-
munications. Standard speech coders for European mobile communications
are summarized in Table 2.2.

2.4.3 NorthAmericanDigitalCellularTelephonyStandards
In North America, the Telecommunication Industries Association (TIA) of
the Electronic Industries Association (EIA) has been standardizing mobile
communication based on Code Division Multiple Access (CDMA) and Time
Division Multiple Access (TDMA) technologies used in the USA. TIA/EIA
adopted Qualcomm CELP (QCELP) [39] for Interim Standard-96-A (IS-96-A),
operating at variable bit rates between 8 kb/s and 0.8 kb/s controlled by a
rate determination algorithm. Subsequently, TIA/EIA released IS-127 [40],
the enhanced variable rate coder, which features a novel function for noise
reduction as a preprocessor to the speech compression module. Under noisy
background conditions, noise reduction provides a more comfortable speech
quality by enhancing noisy speech signals. For personal communication
systems, TIA/EIA released IS-733 [41], which operates at variable bit rates
between 14.4 and 1.8 kb/s. For North American TDMA standards, TIA/EIA
released IS-54 and IS-641-A for full rate and enhanced full rate speech coding,
respectively [42, 43]. Standard speech coders for North American mobile
communications are summarized in Table 2.3.

2.4.4 SecureCommunicationTelephony
Speech coding is a crucial part of a secure communication system, where
voice intelligibility is a major concern in order to deliver the exact voice
commands in an emergency.
Standardization has mainly been organized by the Department of Defense
(DoD) in the USA. The DoD released Federal Standard-1015 (FS-1015) and FS-
1016, called 2.4 kb/s LPC-10e and 4.8 kb/s CELP coders, respectively [44-46].
The DoD also standardized a more recent 2.4 kb/s speech coder [47], based