| The IRA codes introduced by Jin et al. are known to reach rates which are quite close to capacity on the AWGN channel, can be both encoded and decoded in linear time, are perceived to be low complexity codes, and have been adopted into recent standards. In this paper we introduce irregular designs for Systematic with Serially Concatenated Parity codes (SSCPs) and show that both for near-capacity and more practical lower-complexity designs, irregular two-state SSCPs can be designed which achieve the performance of IRA codes at lower complexity. Additionally, we introduce a low-complexity incremental redundancy scheme for irregular SSCPs. |