Mobile Communication: Source Coding, Speech Processing, and Channel Coding, Slides of Mobile Communication Systems

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Mobile Communication

Physical Layer-

Lecture by

TODAY’S SESSION

Source coding and speech processing Source coding Channel coding Convolution coding interleaving

SOURCE CODING AND SPEECH PROCESSING

Speech compression Process

• Regular Pulse Excitation Long-Term Prediction (RPE-LTP)
• Partial speech signal is encoded according to wave encoding
• Rest of the speech signal is transmitted as parameters
• Receiver reconstructs the signal through speech synthesis
• Wave encoding example : PCM

SIMPLIFIED RPE-LTP

LPC-Filter Parameters LTP – Filer Parameter RPE Signal

• 160 samples per 20 ms are received at the coder,
• Speech signal decomposed into three parts
• 36 parameters are generated by the filters,
• RPE signal is compressed by removing redundancy
• 160 samples are compressed to 260 bits
• Data rate: 260 bits per 20 ms, or 13 kbps

CHANNEL CODING

Block coding

• Input data blocks are added with parity and extra zeros to achieve a suitable size for the next step i.e. convolution coding

Convolution coding Convolution codes add redundancy to the original data, A puncturing code can also be used , that deletes some of the extra bits added by convolution code Convolution codes are used for error detection

SPEECH TRAFFIC CHANNEL CODING

Input 260 bits of speech data (full rate) 120 bits of speech data (half rate) The speech input data is divided into two classes Class-I 182 bits , these bits are of high impact on speech need better protection and are encoded differently 95 bits for half rate Class-II 78 bits are of less importance and are not protected 17 bits for half rate

BLOCK CODING FOR LOGICAL CHANNEL

INTERLEAVING