On the design of low rate turbo codes

Low rate codes can be used to achieve coding gain in spread spectrum applications such as direct-sequence code division multiple access. Super-orthogonal- and maximum free distance convolutional codes as well as super-orthogonal turbo codes have previously been reported to be suitable for such systems. We focus on the design of component codes for low rate turbo coding schemes targeting the frame-error rate at low signal-to-noise ratios. We present code search criteria which yield high performing turbo codes on the additive white Gaussian noise channel. Simulation results show that these codes perform better than other low rate turbo codes previously reported in the literature.