Security Performance of Underlay Cognitive Relaying Networks with Energy Harvesting

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An unlicensed relay is located between an unlicensed sender and an unlicensed recipient for securing the sender’s message against a wire-tapper in underlay cognitive networks when the sender–recipient channel is inaccessible. The energy in the sender’s signals is harvested by the relay which utilizes that harvested energy for its signal transmission. To assess expeditiously the security capability, a precise formula of secrecy outage probability is suggested. This formula is then substantiated by computer simulations. Notably, the appropriate selection of system specifications including the time percentage, the relay’s location, the power percentage can drastically enhance the security capability of underlay cognitive relaying networks with energy harvesting. Also, the security capability is constant when one of two power curtailments of unlicensed senders (interference power curtailment and peak transmit power curtailment) is relaxed.

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  1. 1.

    In this paper, “transmitter”, “receiver”, “sender”, “recipient” are the short forms of “licensed transmitter”, “licensed receiver”, “unlicensed sender”, “unlicensed recipient”, respectively.

  2. 2.

    The possibility which the signal-to-noise ratio (SNR) is lower than a preset level is called the COP.

  3. 3.

    The PSCP is the likelihood which the secrecy capacity is positive [10].

  4. 4.

    The SOP is the likelihood which the secrecy capacity is lower than a predetermined security level [10].

  5. 5.

    In this paper, “direct transmission” or “direct communication” refers to the communication paradigm in which no relay is employed to connect the sender with the recipient.

  6. 6.

    It is assumed that the energy consumption of the message decoder is neglected, which is a common assumption in most published works (e.g., [8, 9, 11,12,13,14,15] and references therein).

  7. 7.

    In underlay cognitive networks, licensed transmitters beget interferences on unlicensed recipients. These interferences are ignorable because either they are assumed to follow the Gaussian distribution or the transmitter–recipient distance is sufficiently distant. The assumption on ignoring these interferences is quite common in researching the cognitive radio technology (e.g., [18,19,20] and references therein).


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This research is funded by Vietnam National University HoChiMinh City (VNU-HCM) under grant number B2019-20-01.

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Correspondence to Thiem Do-Dac.

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Ho-Van, K., Do-Dac, T. Security Performance of Underlay Cognitive Relaying Networks with Energy Harvesting. Wireless Pers Commun 110, 829–846 (2020).

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  • Energy harvesting
  • Relaying
  • Secrecy
  • Cognitive radio