Strong Security Polar Coding with Delayed Wiretap Channel State Information
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Secure and reliable communication over the wiretap channel of delayed channel state information (CSI) is an important realistic subject for the study of physical layer secure coding. In this paper a communication model of this delay CSI assumption is presented on the basis of a simplified symmetric compound wiretap channel. Then on this delay CSI communication model, a secure scheme of polar coding based one time pad chaining structure is proposed which successfully achieves the weak security and reliability for the degraded wiretap channel cases but fails to achieve either weak or strong security for the non-degraded cases, due to the unidentifiable problem of the neither secure nor reliable polarized subset. To solve this remaining problem of achieving the strong security in non-degraded delay CSI cases, a new solution call modified multi-block chaining structure is presented in which the original subset of frozen bit is constructed for conveying functional random bits securely. Finally by combining this modified multi-block chaining structure with the one time pad chaining structure, an explicit strong security polar coding scheme is proposed which has almost achieved the average secrecy capacity of perfect CSI assumption under the delay CSI assumption with both reliability and strong security.
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