Vector sum excited linear prediction (VSELP) is a

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 ...

method used in several cellular standards. The VSELP algorithm is an analysis-by-synthesis coding technique and belongs to the class of speech coding algorithms known as

CELP Code-excited linear prediction (CELP) is a linear predictive speech coding algorithm originally proposed by Manfred R. Schroeder and Bishnu S. Atal in 1985. At the time, it provided significantly better quality than existing low bit-rate algori ...

(Code Excited Linear Prediction).ETSI
EN 300 969 - Half rate speech transcoding (GSM 06.20 version 8.0.1 Release 1999)
Retrieved on 2009-07-11 Variations of this

codec A codec is a computer hardware or software component that encodes or decodes a data stream or signal. ''Codec'' is a portmanteau of coder/decoder. In electronic communications, an endec is a device that acts as both an encoder and a decoder o ...

have been used in several 2G cellular telephony standards, including IS-54, IS-136 (D-AMPS),

GSM The Global System for Mobile Communications (GSM) is a family of standards to describe the protocols for second-generation (2G) digital cellular networks, as used by mobile devices such as mobile phones and Mobile broadband modem, mobile broadba ...

(

Half Rate Half Rate (HR or GSM-HR or GSM 06.20) is a speech coding system for GSM, developed in the early 1990s. Since the codec, operating at 5.6 kbit/s, requires half the Bandwidth (computing), bandwidth of the Full Rate codec, network capacity for v ...

speech) and

iDEN Integrated Digital Enhanced Network (iDEN) is a mobile telecommunications technology, developed by Motorola, which provides its users the benefits of a Trunked radio system, trunked radio and a mobile phone, cellular telephone. It was called ...

. It was also used in the first version of

RealAudio RealAudio, also spelled Real Audio, is a proprietary audio format developed by RealNetworks and first released in April 1995. It uses a variety of audio codecs, ranging from low-bitrate formats that can be used over dialup modems, to high-fidelit ...

for audio over the

Internet The Internet (or internet) is the Global network, global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a internetworking, network of networks ...

. The IS-54 VSELP standard was published by the

Telecommunications Industry Association The Telecommunications Industry Association (TIA) is accredited by the American National Standards Institute (ANSI) to develop voluntary, consensus-based industry standards for a wide variety of information and communication technology (Informat ...

in 1989. D-AMPS (IS-54 and IS-136) VSELP specifies an encoding of each 20 ms of speech into 159-bit frames, thus achieving a raw data rate of 7.95 kbit/s. In an actual TDMA cell phone, the

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 ...

output is packaged with error correction and signaling information, resulting in an over-the-air data rate of 16.2 kbit/s. For internet audio, each 159-bit frame is stored in 20 bytes, leaving 1 bit unused. The resulting file thus has a data rate of exactly 8 kbit/s. GSM half-rate VSELP (GSM 06.20) uses 20 ms frames with 112 bits per frame, giving a raw data rate of 5.6 kbit/s. The iDEN VSELP coder has three modes: * 30 ms frames at 126 bits per frame with a raw data rate of 4.2 kbit/s, * 22.5 ms frames at 99 bits per frame with a raw data rate of 4.4 kbit/s and * 22.5 ms frames at 180 bits per frame with a raw data rate of 8.0 kbit/s. A major drawback of VSELP is its limited ability to encode non-speech sounds, so that it performs poorly when encoding speech in the presence of background noise. For this reason, use of VSELP has been gradually phased out in favor of newer codecs. VSELP is also the proprietary digital vocoder used in early Motorola ASTRO products. It was phased out in favor of the newer

IMBE Multi-Band Excitation (MBE) is a series of proprietary speech coding standards developed by Digital Voice Systems, Inc. (DVSI). Overview In 1967 Osamu Fujimura (MIT) showed basic advantages of the multi-band representation of speech ("An App ...

method used for P25.

References

* Ira A. Gerson and Mark A. Jasiuk, ''Vector Sum Excited Linear Prediction (VSELP),'' IEEE Workshop on Speech Coding for Telecommunications, September 1989, pp. 66–68 * Ira A. Gerson and Mark A. Jasiuk, ''Vector sum excited linear prediction (VSELP) speech coding at 8 kbps,'' Proceedings of the 1990 IEEE

International Conference on Acoustics, Speech, and Signal Processing ICASSP, the International Conference on Acoustics, Speech, and Signal Processing, is an annual flagship conference organized by IEEE Signal Processing Society. Ei Compendex has indexed all papers included in its proceedings. The first ICASSP w ...

(ICASSP-90), April 1990, pp. 461–464 {{reflist

External links

Telecommunications Industry Association web site
Speech codecs