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==An example encoder==
There are many different instances of turbo codes, using different component encoders, input/output ratios, interleavers, and [[Punctured code|puncturing patterns]]. This example encoder implementation describes a classic turbo encoder, and demonstrates the general design of parallel turbo codes.
This encoder implementation sends three sub-blocks of bits. The first sub-block is the ''m''-bit block of payload data. The second sub-block is ''n/2'' parity bits for the payload data, computed using a recursive systematic [[convolutional code]] (RSC code). The third sub-block is ''n/2'' parity bits for a known [[permutation]] of the payload data, again computed using an RSC code. Thus, two redundant but different sub-blocks of parity bits are sent with the payload. The complete block has {{nowrap|''m'' + ''n''}} bits of data with a code rate of {{nowrap|''m''/(''m'' + ''n'')}}. The [[permutation]] of the payload data is carried out by a device called an [[interleaver]].
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