Speech detector marks frames whether they contain speech. This provides a speech quality which is acceptable for mobile telephony and comparable with wireline pstn phones. Instead of using bits per sample as in ad conversion, gsm speech coding uses 260 bits. A cascade of 3 different types of coding are adopted in the gsmdcs system parity code cyclic code linear block code. As a result, some auditory information which is relevant in audio. Gsm operates on the 900 mhz, 1800 mhz and 1900 mhz. Speech coding means the rate at which speech data is converted into digital data by maintaining acceptable speech quality and mapping fewer bits for. Basic speech coding methods and codec functionalities are outlined in sec.
Speech coding refers to a process that reduces the bit rate of a speech file speech coding enables a telephone company to carry more voice calls in a single fiber or cable speech coding is necessary for cellular phones, which has limited data rate for each user gsm is95 cellular cdma telcom 2720 4 gsm. The voice compression coding technique is widely used in. Gsm speech coder rpeltp speech coding similar to pstn 19feb04 norsk regnesentral wolfgang leister sender functionality control process speech encoder background noise speech detector to channel codes speech encoder receivespcm coded speech. For speech coding or processing, gsm uses linear predictive coding lpc. This page on gsm tutorial covers gsm speech processing modules at layer1 i. It is a high integration of digital speech, chinese short messages, studymode wireless coding, longdistance home. Gsm global system for mobile communications is the paneuropean cellular mobile standard. When the audio signal passes through a filter, it mimics the vocal tract. Source coding to reconstruct a signal based on the production model of lpc vocoder fs1015 2,4 kbs, melp 2,4 kbs 3. Gsm coding is used for both training and testing for the results in row 3. Gsm speech coding lowpass filter analog speech ad rpeltp speech encoder channel encoder 8000 sampless, bitssample 104 kbps kbps. Vocals gsm speech coder optimized source code provides performance and portability. Duplex distance is the space between the uplink and.
Speech coding jari hagqvist research manager speech coding nokia research center speech and audio systems lab. The adaptive digital gsm full rate gsm fr vocoder is a realtime implementation of the etsi gsm 06. Digital cellular systems worldwide gsm damps japan digital pcs 1900. Dcs 1900 is considered the gsm standard for north america and is called north american gsm. When the fcc issued 1900 mhz to pcs in the united states it was based on gsm. Speech coding tutorial speech coding basic techniques. Da bad frame handling speech decoding comfort noise demodulation deinterleaving channel decoding downlink. Speech processing in gsm mobiles ad speech coding vaddtx channel coding interleaving burst building modulation gmsk rf uplink. Gsmfr was adopted by the 3gpp for mobile telephony in the early 1990s. With 20ms as the unit, the voice coder outputs 260bits after compressed coding. Gsm speech processing steps speech compressed using a predictive coding scheme divided into blocks, each of which is protected partly by crc and partly by a convolutional code interleaving to protect against burst errors encryption for providing privacy assembled into time slots modulated for analog transmission using fsk. Speech coding differs from other forms of audio coding in that speech is a simpler signal than most other audio signals, and a lot more statistical information is available about the properties of speech. Speech coding methods, standards, and applications jerry d.
Three speech coding algorithms are part of this standard. The purpose of these coders is to compress the speech signal before its transmission, reducing the number of bits needed. If the vocal chords vibrate, voiced sounds such as a and o are produced. Speech coding is fundamental to the operation of the public switched telephone network pstn, videoconferencing systems, digital cellular communications, and emerging voice over internet protocol voip applications. Abstract this paper investigates the influence of gsm speech coding on text independent speaker recognition performance. Waveform coding to reconstruct a signal waveform similar to the original one pcm g. The whole timit database was passed through these coders, obtaining three transcoded databases. The goal of speech coding is to represent speech in digital form with as few bits as. This tutorial describes speech coding basics and covers various speech codec techniques such as pcm, adpcm, celp,evrc employed in todays wireless networks such as gsm, cdma and more speech coding basics. Speech coding for speech coding or processing, gsm uses linear predictive coding lpc. The voice coder is based on the residual excited linear prediction reip coder.
Channel spacing indicates the spacing between adjacent carrier frequencies. The received signal at the gsm speech decoder is passed through a. This subnetwork takes 160 speech samples in bit uniform pcm format as input. Gsm speech processing gsm layer1 gsm physical layer. Speech coding refers to a process that reduces the bit. The windowing technique used for speech coding in gsm codec is a. With vocals proprietary techniques, gsm speech coders are optimized to support modern processors including dsps and conventional processors from amd, intel, adi, ti and other vendors. This paper investigates the influence of gsm speech coding on text independent speaker recognition performance.
Speech coding facilitates speech compression without perceptual loss that results in the elimination or deterioration of both speech and speaker specific features used for a wide range of. Moreover, the long term predictor ltp is used to enhance the compression effect. Gsm traffic band, traffic channel, timeslot, channel mode, halfrate speech subchannel, ms tx level gprs traffic band, traffic channel, coding scheme, multislot configuration, p0, ms tx level burst 1 to 6 egprs traffic band, traffic channel, downlink modulation coding scheme, uplink. The three existing gsm speech coder standards were considered. Ltp can make the coding of residual data more advantageous by removing the vowels from the voice. Speech technologies speech coding speech coding classification 1.
Gsm uses digital communication system or dcs 1800 and is the worlds main 2g standard. Hence, the gsm coding algorithm produces a gross bit rate. The global system for mobile communications gsm overview. There was almost an exponential growth of speech coding standards in the 1990s for a wide. Gsm converts bit digital signals sampled at 8 khz into blocks of 260 bits for every 160 original samples. Speech is generated by pumping air from the lung through the vocal tract consisting of throat, nose, mouth, palate, tongue, teeth and lips. The transcoded data was obtained by passing speakers speech files through the gsm coderdecoder. For the creation of nasal sounds, the nasal cavity can be. Gsm speech codec the fullrate gsm speech codec 2 is a lossy speech codingdecoding algorithm based on a regular pulse excited long term prediction scheme 5.