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I need to construct channel code for 5 bits of information for a wireless channel. Possible code rate could be as low as 1/128 (very reliable). At decoder I assume to use channel LLRs as decoder input to take into account channel conditions. At a first glance I'd use a repetition code (or spreading sequence) thus there will be 2^5 coded word in total and use ML decoder (correlation with each code word). These seems to be simple in realization. Are there any other types of channel codes for such requirements.

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    $\begingroup$ "Are there any types of channel codes for such requirements.", I think there are quite a few different codes you can use. What is the application where you need to send 5 bits to be "very reliable"? $\endgroup$ – BryanEhlers Apr 18 at 14:05
  • $\begingroup$ It's supposed to be a wireless packet transmission. I'd like to transmit 5 bits of control information in each packet. Data has another coding scheme and is not an issue. $\endgroup$ – Dmitriy Apr 19 at 9:23
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Since you say you want to take the channel conditions into account, one thing that immediately comes to mind is to suggest an adaptive link. Assuming you have access to the channel conditions, you can do two things to adjust the link:

  1. Change the modulation: for example, think about using a higher order scheme like 16 QAM for "clear" channel conditions and using QPSK or BPSK for worse channel conditions.

  2. Change the code rate of the channel code: this can be done by choosing a code with some rate, then depending on the channel you can perform puncturing to remove some parity bits (thus increase rate) when the channel is "clear".

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  • $\begingroup$ I can't find it related to my question. I'd like to find out are there any better channel codes than repetition code. E.g. a concatenation of convoultional code and repetition code, etc $\endgroup$ – Dmitriy Apr 22 at 15:11

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