A multi-mode 3GPP-LTE/HSDPA turbo decoder

The LTE standard supports a maximum throughput of 300MBit/s using 4×4 MIMO and a channel bandwidth of 20 MHz. At the same time the latest HSDPA technology supports 82MBit/s using 2×2 MIMO and Dual Cell techniques. While LTE uses a conflict-free interleaver, which allows highly efficient implementation of parallel decoders for such throughputs, HSDPA uses the UMTS interleaver that causes memory access conflicts. A combined turbo decoder is presented which supports both HSDPA and LTE with an overhead of only 11.5 % over an optimized LTE-only decoder. Its area is 1.46 mm² in 40nm low power CMOS. Its power consumption is only 452 mW. State-of-the-art approaches utilizing design time conflict resolution require 9MB of storage for permutation tables. Our decoder achieves a reduction to 32kB by combining a hybrid technique with compression of the permutation vectors.