Bit-Level Extrinsic Information Exchange Method for Double-Binary Turbo Codes

Abstract

Abstract-Nonbinary turbo codes have many advantages over single-binary turbo codes, but their decoder implementations require much more memory, particularly for storing symbolic extrinsic information to be exchanged between two soft-input-softoutput (SISO) decoders. To reduce the memory size required for double-binary turbo decoding, this paper presents a new method to convert symbolic extrinsic information to bit-level information and vice versa. By exchanging bit-level extrinsic information, the number of extrinsic information values to be exchanged in doublebinary turbo decoding is reduced to the same amount as that in single-binary turbo decoding. A double-binary turbo decoder is designed for the WiMAX standard to verify the proposed method, which reduces the total memory size by 20%.Index Terms-Double-binary turbo codes, extrinsic information, maximum a posteriori algorithm, turbo decoding.

Reconfigurable Parallel Turbo Decoder Design for Multiple High-Mobility 4G Systems

“…To further increase the hardware usage of extrinsic buffer, Fig. 11(b) shows an efficient extrinsic buffer design by using the bit-level extrinsic information exchange method [22]. This method transfers the extrinsic information of radix-4 DB MAP decoding from symbol-level values to bit-level values and makes the extrinsic buffer access only two extrinsic information values.…”

Low complexity state metric compression technique in turbo decoder

“…Turbo decoder has been extensively investigated since the appearance of turbo code [4,5]. We just briefly review the turbo decoder structure in this section.…”

Memory reduced MAP decoding for double-binary turbo decoder

“…1, four processes require the accesses to the branch metric memory on their own window processing, simultaneously. Therefore, in hardware implementation, the branch metric memory consists of four memory banks [3,4]. In doublebinary turbo decoder implementation, since the branch metric memory increases four times compared to the classical single-binary turbo decoder, the total memory size required in the SISO decoder increases hugely as denoted in Table I.…”

“…The symbol-level extrinsic information required to recover the branch metrics can be obtained by simple bit-to-symbol conversion introduced in [3].…”

“…Although there are many implementations for classical single-binary turbo decoders, there has been little research dedicated to the hardware implementation of the double-binary turbo decoders [2,3]. Compared to the single-binary turbo code, the double-binary turbo code requires much more memory in decoding.…”