To meet the higher data rate requirement of emerging wireless communication technology, numerous parallel turbo decoder architectures have been developed. However, the interleaver has become a major bottleneck that limits the achievable throughput in the parallel decoders due to the massive memory conflicts. In this paper, we propose a flexible Double-Buffer based Contention-Free (DBCF) interleaver architecture that can efficiently solve the memory conflict problem for parallel turbo decoders with very high parallelism. The proposed DBCF architecture enables high throughput concurrent interleaving for multi-standard turbo decoders that support UMTS/HSPA+, LTE and WiMAX, with small datapath delays and low hardware cost. We implemented the DBCF interleaver with a 65nm CMOS technology. The implementation of this highly efficient DBCF interleaver architecture shows significant improvement in terms of the maximum throughput and occupied chip area compared to the previous work.