CHANNEL CODING

GSM Glossary

GSM — Channel Coding

 

 

 

 

 

 

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Information on Channel Coding

Channel coding is the technique of protecting message signals from signal impairments by adding redundancy to the message signal. In a communications system, error control is necessary for messages that require high reliability, or if the transmission medium is prone to error. Messages requiring high reliability include data with no internal redundancy, control signals, and voice or video signals that have undergone efficient source coding.
     Channel coding in GSM operates by coding each 240 bit block of data in a GSM full-rate data channel with a half-rate punctured convolutional code to produce 456 bits that are interleaved across four 114-bit time division multiple access (TDMA) frames.The interleaving used in GSM:

  • spreads burst errors (due to Raleigh fading) over a longer period, reducing the reduce peak bit error rate, and
  • allows the channel coding to correct the (now) randomly spaced bit errors.


    • Other topics in our resources on GSM related to Channel Coding include: 
     
  • convolutional coding
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  • punctured convolutional code

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