Secrecy Outage Capacity of Fading Channels

• Published in: IEEE transactions on information theory 2013-09, Vol.59 (9), p.5379-5397
• Main Authors: Gungor, Onur, Jian Tan, Koksal, Can Emre, El-Gamal, Hesham, Shroff, Ness B.
• Format: Article
• Language: English
• Subjects: Applied sciences; Block fading channels; channel state information; Communication; Delays; Electronic eavesdropping; Exact sciences and technology; Fading; information theoretic secrecy; Information theory; Information, signal and communications theory; key queue; Power control; Privacy; Radiocommunications; Receivers; Resource management; secrecy outage capacity; Secret; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmission and modulation (techniques and equipments); Transmitters; Transmitters. Receivers
• ISSN: 0018-9448; 1557-9654
• DOI: 10.1109/TIT.2013.2265691

This paper considers point-to-point secure communication over flat fading channels under an outage constraint. More specifically, we extend the definition of outage capacity to account for the secrecy constraint and obtain sharp characterizations of the corresponding fundamental limits under two different assumptions on the transmitter channel state information (CSI). First, we find the outage secrecy capacity assuming that the transmitter has perfect knowledge of the legitimate and eavesdropper channel gains. In this scenario, the capacity achieving scheme relies on opportunistically exchanging private keys between the legitimate nodes. These keys are stored in a key buffer and later used to secure delay sensitive data using the Vernam's one time pad technique. We then extend our results to the more practical scenario where the transmitter is assumed to know only the legitimate channel gain. Here, our achievability arguments rely on privacy amplification techniques to generate secret key bits. In the two cases, we also characterize the optimal power control policies which, interestingly, turn out to be a judicious combination of channel inversion and the optimal ergodic strategy. Finally, we analyze the effect of key buffer overflow on the overall outage probability.