Abstract
A cooperative cognitive radio scheme exploiting primary signals for energy harvesting is proposed. The relay sensor node denoted as the secondary transmitter (ST) harvests energy from the primary signal transmitted from the primary transmitter, and then uses it to transmit power superposed codes of the secrecy signal of the secondary network (SN) and of the primary signal of the primary network (PN). The harvested energy is split into two parts according to a power splitting ratio, one for decoding the primary signal and the other for charging the battery. In power superposition coding, the amount of fractional power allocated to the primary signal is determined by another power allocation parameter (e.g., the power sharing coefficient). Our main concern is to investigate the impact of the two power parameters on the performances of the PN and the SN. Analytical or mathematical expressions of the outage probabilities of the PN and the SN are derived in terms of the power parameters, location of the ST, channel gain, and other system related parameters. A jointly optimal power splitting ratio and power sharing coefficient for achieving target outage probabilities of the PN and the SN, are found using these expressions and validated by simulations.
Highlights
Cognitive radio (CR), which involves cognitive sensing, has been proposed to increase spectrum utilization of the licensed frequency band [1,2,3]
The power splitting ratio indicates the fraction of radio frequency (RF) power harvested for battery charging, while the power sharing coefficient represents the fraction of power allocated to the primary signal in power superposition coding
The signals received by the primary receiver (PR) and the secondary receiver (SR) in the second phase from the secondary transmitter (ST) can be expressed as yST − PR = xc × h2 + n PR =
Summary
Cognitive radio (CR), which involves cognitive sensing, has been proposed to increase spectrum utilization of the licensed frequency band [1,2,3]. A CC scheme exploiting energy harvesting and power superposition coding is explored, considering a sensor network coexisting with a communication network. The power splitting ratio indicates the fraction of RF power harvested for battery charging, while the power sharing coefficient represents the fraction of power allocated to the primary signal in power superposition coding. Energy harvesting in combination with power superposition coding, both performed by the ST for the CC scheme, is considered for the first time. Optimal power allocation schemes aretoinrelay relation to relay selection, which employs a single relay sensor to execute power superposition coding. Unlike ours, which employs a single relay sensor to execute power superposition coding.
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