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Adaptive Tuning of (Wideband) AMR Codec Frames for Lookup Tables

IP.com Disclosure Number: IPCOM000019954D
Published in the IP.com Journal: Volume 3 Issue 11 (2003-11-25)
Included in the Prior Art Database: 2003-Nov-25
Document File: 2 page(s) / 69K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

In the UMTS (Universal Mobile Telecommunications System) traffic signals are generated in the Media Gateway (MGW). Some traffic generation can be performed using a lookup table as shown in figure 1 where the lookup table sends out a sequence of AMR (Adaptive Multi-Rate) codec frames y(m) that is detected at the receiver side and decoded into an audible signal z(n). Lookup tables can be easily generated using the AMR encoder and producing codec frames based on a given ideal signal x(k) as shown in figure 2. In consequence one can derive the following equation:

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© SIEMENS AG 2003 file: 2002J08407.doc page: 1

Adaptive Tuning of (Wideband) AMR Codec Frames for Lookup Tables

Idea: Dr. Bart Baekelandt, BE-Herentals; Kurt Smet, BE-Herentals

In the UMTS (Universal Mobile Telecommunications System) traffic signals are generated in the Media Gateway (MGW). Some traffic generation can be performed using a lookup table as shown in figure 1 where the lookup table sends out a sequence of AMR (Adaptive Multi-Rate) codec frames y(m) that is detected at the receiver side and decoded into an audible signal z(n).

Lookup tables can be easily generated using the AMR encoder and producing codec frames based on a given ideal signal x(k) as shown in figure 2. In consequence one can derive the following equation:

)))

(

 
n
[g61]z [g61] ,

where D( ) and E( ) are the decoder respectively encoder functions. Because the encoder function E( ) is not the exact inverse of the decoder function D( ), the produced signal z(n) at the decoder side deviates from the original signal. In the worst case this deviation can exceed acceptable limits. Up to now no solution is known.

Therefore it is proposed to use a feedback mechanism to automatically tune the lookup table to minimize the difference between z( ) and x( ). Mathematically speaking, this means that the difference between the input signal and the output signal is minimized for a certain cost function. Applied to the above equation we get:

)

( k x


)


D

D

(


y

(


m


))


(

E

(

 
n
[g61]z [g174] as T(E( )) approa...