Secure HARQ communication protocols based on Turbo Codes

In this paper a secure Incremental Redundancy - Hybrid Automatic Repeat Request (IR-HARQ) scheme, based on Turbo Codes (TC), is proposed. Typical drawbacks of HARQ systems, such as spectral efficiency, latency unpredictability, correct packet delivery control (under fixed dead-line time) are definitively minimized thanks to a mathematical approach that exploits the statistical property of Additive Gaussian White Noise (AWGN) and the theoretical evaluation of Turbo Codes performance (in terms of symbol and codeword error probability). In order to decide if the received frame is correct and authentic, or a NACK (Non ACKnowledgment) packet must be forwarded to the sender, the codeword is examined through a verification test based on an adaptive threshold that: 1) depends on channel condition; 2) takes into account the error probability associated with of the current re-transmission step turbo code redundancy amount; 3) verifies if the sender is authentic (i.e. if he/she makes use of the correct turbo encoding parameters).