What isAdaptive Multi-Rate (AMR)

Adaptive Multi-Rate (AMR) is a speech codec that compresses audio files to transmit over cellular networks. It can transmit both waveform signals and speech parameters, making it a hybrid of speech codes. AMR is mandatory for most third-generation (3G) cellular systems and is preferred for the Global System for Mobile Communications (GSM) standard, as it provides superior audio performance, better coverage and quality, and is easier to implement than previous codecs.

Features of Adaptive Multi-Rate Codec

The Adaptive Multi-Rate Codec offers speech rates from 4.75 to 12.2 kbits/s, with a sampling frequency of 8 kHz and speech coding performed in 20ms frames. It uses technologies such as comfort noise generation, discontinuous transmission, and voice activity detection to reduce bandwidth usage during idle periods. Adaptive Multi-Rate is unique in its ability to adapt to the radio channel environment and select optimal speech, unlike other speech codecs that operate with a fixed level of error protection and a fixed rate.

Advantages of Adaptive Multi-Rate

Compared to other codecs, Adaptive Multi-Rate has many advantages. It can be tailored to meet the different needs of operators, and codec mode adaptation can be used to improve voice quality, even in half-rate mode. It offers better power control and handover, and is also more resistant to interference and errors.


What is a speech codec?

A speech codec is a technology used to compress audio files before transmitting them over a network. It is used to reduce the bandwidth required to transmit audio signals and improve the quality of a user’s voice call.

What is the sampling frequency used in Adaptive Multi-Rate Codec?

The Associated sampling frequency of Adaptive Multi-Rate Codec is 8 kHz.

Final thoughts

Adaptive Multi-Rate Codec is a crucial technology to transmit audio files in cellular systems. It compresses the audio file while maintaining the quality of voice and offers several advantages over other codecs. The technology is continuously evolving, and new codecs are being developed to meet the changing needs of consumers.

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