Advanced Multi-Band Excitation (AMBE) is a proprietary speech coding standard developed by Digital Voice Systems, Inc.
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AMBE is a codebook-based vocoder that operates at bitrates of between 2 and 9.6 kbit/s, and at a sampling rate of 8 kHz in 20-ms frames. The audio data is usually combined with up to 7 bit/s of forward error correction data, producing a total RF bandwidth of approximately 2250 Hz (compared to 2700–3000 Hz for an analog single sideband transmission). Lost frames can be masked by using the parameters of the previous frame to fill in the gap.
In 1967 Osamu Fujimura (MIT) showed basic advantages of the multi-band representation of speech ("An Approximation to Voice Aperiodicity", IEEE 1968). This work gave a start to development of the "multi-band excitation" method of speech coding, that was patented in 1988 by founders of DVSI as "Multi-Band Excitation" (MBE). All consequent improvements known as Improved Multi-Band Excitation (IMBE), AMBE, AMBE+ and AMBE+2 are based on this MBE method.
It is used by the Inmarsat and Iridium satellite telephony systems and certain channels on XM Satellite Radio and is the speech coder for OpenSky Trunked radio systems.
AMBE is used in D-STAR amateur radio digital voice communications. It has met criticism because the nature of its patent and licensing runs counter to the openness of amateur radio.[1]
The NXDN digital voice and data protocol uses the AMBE +2 codec. NXDN is implemented by Icom in the IDAS system and by Kenwood as NEXEDGE.
APCO Project 25 Phase 1 and Phase 2 trunked radio systems also use the AMBE+2 codec.
Use of the AMBE standard requires a license from Digital Voice Systems, Inc. While a licensing fee is due for most codecs, DVSI does not disclose software licensing terms. Anecdotal evidence suggests that licensing fee begin from between $100,000 to $1 million. For purposes of comparison, licensing fees for use of the MP3 standard starts at $15,000. For small-scale use and prototyping, the only option is to purchase a dedicated hardware IC from DVSI.
In spite of the fact that a license from DVSI is required in any case (for usage of technology), the software implementations of the MBE vocoders from DSPINI opens wide possibilities for developers and manufacturers of radio and of other equipment where a usage of these vocoders is needed. High quality, high optimization level, high reliability and reasonable prices are basic advantages of these implementations.
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