Multi-Band Excitation (MBE) is a series of proprietary

speech coding Speech coding is an application of data compression to digital audio signals containing speech. Speech coding uses speech-specific parameter estimation using audio signal processing techniques to model the speech signal, combined with generic da ...

standards developed by Digital Voice Systems, Inc. (DVSI).

Overview

In 1967 Osamu Fujimura (

MIT The Massachusetts Institute of Technology (MIT) is a private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of modern technology and sc ...

) 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 1997 (now expired) by founders of DVSI as "Multi-Band Excitation" (MBE). All consequent improvements known as ''Improved Multi-Band Excitation'' (IMBE), ''Advanced Multiband Excitation'' (AMBE), AMBE+ and AMBE+2 are based on this MBE method. AMBE is a

codebook A codebook is a type of document used for gathering and storing cryptography codes. Originally, codebooks were often literally , but today "codebook" is a byword for the complete record of a series of codes, regardless of physical format. Cr ...

-based

vocoder A vocoder (, a portmanteau of ''vo''ice and en''coder'') is a category of speech coding that analyzes and synthesizes the human voice signal for audio data compression, multiplexing, voice encryption or voice transformation. The vocoder wa ...

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 In computing, telecommunication, information theory, and coding theory, forward error correction (FEC) or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels. The centra ...

data, producing a total RF bandwidth of approximately 2,250 Hz (compared to 2,700–3,000 Hz for an analogue single sideband transmission). Lost frames can be masked by using the parameters of the previous frame to fill in the gap.

Usage

AMBE is used by the

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and

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satellite telephony A satellite telephone, satellite phone or satphone is a type of mobile phone that connects to other phones or the telephone network by radio link through satellites orbiting the Earth instead of terrestrial cell sites, as cellphones do. Therefor ...

systems and certain channels on

XM Satellite Radio XM Satellite Radio Holdings Inc. (XM) was one of the three satellite radio ( SDARS) and online radio services in the United States and Canada, operated by Sirius XM Holdings. It provided pay-for-service radio, analogous to subscription cable ...

and is the speech coder for OpenSky

Trunked radio system A Trunked Radio System (TRS) is a two-way radio system that uses a control channel to automatically assign frequency channels to groups of user radios. In a traditional half-duplex land mobile radio system a group of users (a ''talkgroup'') w ...

s. AMBE is used in D-STAR

amateur radio Amateur radio, also known as ham radio, is the use of the radio frequency radio spectrum, spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emer ...

digital voice communications. It has met criticism from the amateur radio community because the nature of its

patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an sufficiency of disclosure, enabling discl ...

and licensing runs counter to the openness of amateur radio, as well as usage restriction for being "undisclosed digital code" under FCC rule 97.309(b) and similar national legislation. System Fusion, open specification from

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, also uses AMBE codec with C4FM modulation. 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 2 trunked radio systems also use the AMBE+2 codec, while older Phase 1 radios such as the

Motorola Motorola, Inc. () was an American multinational telecommunications company based in Schaumburg, Illinois. It was founded by brothers Paul and Joseph Galvin in 1928 and had been named Motorola since 1947. Many of Motorola's products had been ...

XTL and XTS series use the earlier IMBE codec. Newer Phase 1 capable radios such as the APX series radios use the AMBE+2 codec, which is backwards compatible with Phase 1.

Digital Mobile Radio Digital Mobile Radio (DMR) is a digital radio Technical standard, standard for voice and data transmission in non-public Radio network, radio networks. It was created by the European Telecommunications Standards Institute (ETSI), and is designed t ...

(DMR) and Motorola's MOTOTRBO use the AMBE+2 codec.

Licensing

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 MP3 (formally MPEG-1 Audio Layer III or MPEG-2 Audio Layer III) is a coding format for digital audio developed largely by the Fraunhofer Society in Germany under the lead of Karlheinz Brandenburg. It was designed to greatly reduce the amount ...

standard started at $15,000. For small-scale use and prototyping, the only option is to purchase a dedicated hardware IC from DVSI. These ICs can be purchased for less than $100 in small quantities. DSP Innovations Inc. offers a software implementation of APCO P25 Phase 1 (Full-Rate) and Phase 2 (Half-Rate) codecs as well as DMR and dPMR codecs. A technology licence from DVSI is required. The patent for IMBE has expired.

Alternatives

Codec2 is an open source alternative which uses half of the bandwidth of AMBE to encode speech of similar quality, created by David Rowe and lobbied by

Bruce Perens Bruce Perens (born around 1958) is an American computer programmer and advocate in the free software movement. He created ''The Open Source Definition'' and published the first formal announcement and manifesto of open source. He co-founded the ...

. Codec2 still continues to evolve, with additional "modes" being developed, refined and made available on a continuous basis. This has resulted in an open source codec that has progressively increased its robustness and performance – when subjected to some of the most challenging RF and acoustic environments.

References

External links