This is a suboptimal technique, since in fact both codes (Block and Convolutional codes) are working in tandem to reduce error probability.
- A concatenated code uses two levels of coding: an inner code and an outer code.
- The inner code is typically designed to remove most of the errors introduced by the channel. As shown in figure 6.4
- The outer code is typically a less powerful code that further reduces error probability when the received coded bits have a relatively low probability of error (since most errors are corrected by the inner code).
- Concatenated codes may have the inner and outer codes separated by an interleaver to break up, block errors introduced by the channel.
- Concatenated codes typically achieve very low error probability with less complexity than a single code with the same error probability performance
Block diagram of Concatenated coding
- The decoding of concatenated codes is typically done in two stages, as indicated in the block diagram
- First the inner code is decoded and then the outer code isdecoded separately.