The rate-allocation problem for turbo codes

In this letter, we view the implicit unequal error protection observed in the asymptotic performance of most turbo codes as an impetus to the formulation of a rate-allocation problem, associated with the distribution of a fixed quota of coded bits in the trellis sections of the upper and lower recursive systematic convolutional codes of the turbo-code structure. We then present an effective greedy approach for solving this rate-allocation problem via a two-phase process of puncturing and repetition coding, resulting in the improvement of the asymptotic performance of the code and lowering of its error floor. Sample simulation results are presented, confirming the potential gains of the approach.