Reverse Rate Matching for Low-Power LTE-Advanced Turbo Decoders

In this paper, a reverse rate matching method is presented for LTE-Advanced turbo decoders. In LTE-Advanced systems, the turbo codes are highly punctured to achieve high data rate when the channel is reliable. In that case, since only a small part of the input frame memory contains meaningful data, accessing all entries of the memory is redundant. To reduce the meaningless accesses, the proposed reverse rate matching method evaluates whether each code bit is punctured or not. As a result, more than 30% of the power consumed in accessing the input memory can be saved when the code rate is high. Furthermore, a low-complexity hardware architecture realizing the proposed method is presented for parallel-SISO decoding. By making use of a specific relationship resident in parallel input indexes, the hardware complexity of the reverse rate matching unit is reduced by 44%.