On the contention-free and spread characteristics of serially-pruned interleavers

Serial pruning of turbo interleavers have been proposed in the literature as a simple scheme to provide more flexible codeword lengths. In this paper, we prove two important attributes about serially pruned interleavers. First, we show that serially pruned interleavers inherit the content-free property of their mother interleaver, and hence they remain parallelizable. An example serially-pruned QPP LTE interleaver is parallelized. Second, the minimum spread factor of a serially-pruned interleaver closely matches the spread factor of its mother interleaver for small pruning gaps with minimal impact on BER performance, and degrades gracefully with the pruning length. Simulation results of practical pruned LTE turbo interleavers demonstrate the graceful degradation of spread characteristics and BER performance of serially pruned interleavers.