On the Decoding of Certain Generalized Concatenated Convolutional Codes

Two classes of generalized concatenated (GC) codes with convolutional outer codes are studied. The first class is based on the classical Plotkin ja \Phi bjbj construction. A new suboptimal multi-stage soft decision algorithm is proposed and the corresponding performance bounds are obtained. These codes are shown to achieve better performance than conventional convolutional codes with equal or less decoding complexity, and are capable of unequal error protection. The Plotkin construction is then generalized using an inner differential encoding structure to obtain a second class of GC codes. A low-complexity two-iteration decoding algorithm using traditional hard-output Viterbi decoders is proposed. Numerical results show that the new coding systems can achieve comparable and sometimes superior performance to low-complexity turbo codes with similar computational complexity. Index Terms: Iterative decoding, concatenated codes, turbo codes. Revised draft of June 1, 1997 for IEEE Journal on..