3GPP AMR协议：GSM、UMTS与LTE应用的关键编解码标准

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3GPP-AMR协议是3rd Generation Partnership Project (3GPP) 发布的一项关键技术，它是一种专为移动通信系统设计的高效、适应性强的音频编解码标准。AMR（Adaptive Multi-Rate）在2G（GSM）系统以及早期的3G系统，如UMTS（Universal Mobile Telecommunications System）中得到了广泛应用，尤其是在语音编码和传输方面，它能够提供多种比特率选项以适应不同的网络条件和终端性能。这个标准定义了Mandatory Speech Codec speech processing functions，即强制性的语音编码器和解码器功能，旨在优化音频质量的同时减小数据流量。AMR通过动态调整采样率和量化位数，实现了在不同带宽环境下对语音信号进行有效的压缩和还原，确保了在有限的网络资源下实现清晰的语音通话。 3GPP TS 26.090 V9.0.0 Release 9（2010年版本）是关于AMR编码的详细技术规范，它详细阐述了编码器的设计原理、编码流程、以及与GSM、UMTS和后续的演进技术如LTE（Long-Term Evolution）的兼容性。这份文档还提到了编码的 transcoding functions，即编码过程中的转换能力，使得同一份语音数据可以在不同的编解码器之间无缝切换，提高了系统的灵活性。 ETSITS126090 V9.0.0文档由欧洲电信标准化协会（ETSI）发布，并强调了版权和获取方式，指出个人可以下载PDF格式的副本，同时声明如有内容差异，应以ETSI官方发布的PDF版本为准。该文档的发行地址和联系方式也一并给出，以供用户查询或获取更新信息。 3GPP-AMR协议对于移动通信领域的语音通信质量提升起到了关键作用，其适应性和效率是推动早期移动网络向更高带宽、更高质量服务演进的重要技术支撑。随着技术发展，AMR的后续版本和演进还在不断优化，以满足不断变化的无线通信需求。

ETSI

ETSI TS 126 090 V9.0.0 (2010

01)

3GPP TS 26.090 version 9.0.0 Release 9

()

Impulse response of the tilt compensation filter

n() The AGC-controlled gain scaling factor of the adaptive postfilter

α The AGC factor of the adaptive postfilter

()

Pre-processing high-pass filter

(), wn

() LP analysis windows

()

Length of the first part of the LP analysis window

()

Length of the second part of the LP analysis window wn

()

Length of the first part of the LP analysis window wn

()

Length of the second part of the LP analysis window wn

()

() The auto-correlations of the windowed speech

(

)

()

lag

Lag window for the auto-correlations (60 Hz bandwidth expansion)

The bandwidth expansion in Hz

The sampling frequency in Hz

'()

The modified (bandwidth expanded) auto-correlations

()

The prediction error in the ith iteration of the Levinson algorithm

The ith reflection coefficient

i()

The jth direct form coefficient in the ith iteration of the Levinson algorithm

()

′

Symmetric LSF polynomial

()

′

Antisymmetric LSF polynomial

()

Polynomial

()

′

with root

=−

eliminated

()

Polynomial

()

′

with root

eliminated

The line spectral pairs (LSPs) in the cosine domain

An LSP vector in the cosine domain

()

The quantified LSP vector at the ith subframe of the frame n

The line spectral frequencies (LSFs)

() A

th order Chebyshev polynomial

fi fi

(), () The coefficients of the polynomials Fz

()and Fz

()

fifi

(), () The coefficients of the polynomials

()

′

and

()

′

fi() The coefficients of either

()

Cx Sum polynomial of the Chebyshev polynomials

Cosine of angular frequency

Recursion coefficients for the Chebyshev polynomial evaluation

The line spectral frequencies (LSFs) in Hz

[]

ff f=

12 10

K The vector representation of the LSFs in Hz

()

()1

n ,

()

()2

n The mean-removed LSF vectors at frame n

()

()1

n ,

()

()2

n The LSF prediction residual vectors at frame n

(

)

The predicted LSF vector at frame n

()

1n − The quantified second residual vector at the past frame

The quantified LSF vector at quantization index k

LSP

The LSP quantization error

,,,,= 110K LSP-quantization weighting factors

ETSI

ETSI TS 126 090 V9.0.0 (2010

01)

3GPP TS 26.090 version 9.0.0 Release 9

The distance between the line spectral frequencies f

i+1

and f

i−1

()

hn The impulse response of the weighted synthesis filter

The correlation maximum of open-loop pitch analysis at delay k

,,,=13K

The correlation maxima at delays ti

,,,= 13K

()

Mt i

,, ,,=13K The normalized correlation maxima M

and the corresponding delays ti

,,,= 13K

HzWz

AzAz

() ()

(

)

() ( / )

The weighted synthesis filter

()

The numerator of the perceptual weighting filter

()

The denominator of the perceptual weighting filter

The integer nearest to the fractional pitch lag of the previous (1

or 3

) subframe

(

)

The windowed speech signal

()

The weighted speech signal

()

sn Reconstructed speech signal

()

′

The gain-scaled post-filtered signal

()

Post-filtered speech signal (before scaling)

()

The target signal for adaptive codebook search

()

The target signal for algebraic codebook search

res n

() The LP residual signal

()

cn The fixed codebook vector

()

vn The adaptive codebook vector

yn vn hn()= () ()∗ The filtered adaptive codebook vector

()

The past filtered excitation

()

The excitation signal

()

The emphasized adaptive codebook vector

'( )un The gain-scaled emphasized excitation signal

The best open-loop lag

min

Minimum lag search value

max

Maximum lag search value

()

Rk Correlation term to be maximized in the adaptive codebook search

The FIR filter for interpolating the normalized correlation term

()

The interpolated value of

()

Rk for the integer delay k and fraction t

The FIR filter for interpolating the past excitation signal

()

un to yield the adaptive codebook

vector

()

Correlation term to be maximized in the algebraic codebook search at index k

The correlation in the numerator of A

at index k

The energy in the denominator of A

at index k

dHx=

The correlation between the target signal

()

and the impulse response

()

hn, i.e., backward

filtered target

The lower triangular Toepliz convolution matrix with diagonal

()

h 0 and lower diagonals

() ( )

hh139,,K

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