Abstract
Non-orthogonal multiple access (NOMA) has been proposed as a promising technology that is capable of improving the spectral efficiency of fifth-generation wireless networks and beyond. However, in practical communication scenarios, transceiver architectures inevitably suffer from radio frequency (RF) front-end related impairments that cause non-negligible performance degradation. This issue can be addressed by analog and digital signal processing algorithms, however, inevitable aspects of this approach such as time-varying hardware characteristics and imperfect compensation schemes result to detrimental residual distortions. In the present contribution we investigate the physical layer security of NOMA-based amplify-and-forward relay systems under such realistically incurred residual hardware impairment (RHI) effects. Exact and asymptotic analytic expressions for the corresponding outage probability (OP) and intercept probability (IP) of the considered setup over multipath fading channels are derived and corroborated by respective simulation results. Based on this, it is shown that RHI affects both the legitimate users and eavesdroppers by increasing the OP and decreasing the IP. For a fixed OP, RHI generally increases the corresponding IP, thereby reducing the secure performance of the system. Further interesting insights are provided, verifying the importance of the offered results for the effective design and deployment of secure cooperative communication systems.
Highlights
The increasing number of connected devices and the continuously increasing quality of service (QoS) requirementsThe associate editor coordinating the review of this manuscript and approving it for publication was Zhu Han.pose several theoretical and technological challenges on the effective design and deployment of fifth-generation (5G) networks and beyond [1]
NUMERICAL AND SIMULATION RESULTS Considering the C-non-orthogonal multiple access (NOMA) approach described above and utilizing the derived analytical expressions and their respective computer simulations, this section quantifies the effect of TX and/or RX residual hardware impairment (RHI) on the performance of communication systems based on cooperative NOMA (C-NOMA) with an eavesdropper (C-NOMA-E)
RHI causes a significant increase in the average outage probability (OP) of the system, which greatly depends on the power allocation between the NOMA users, with an OP floor observed in some cases
Summary
The increasing number of connected devices and the continuously increasing quality of service (QoS) requirements. In contrast to OMA, NOMA does not allocate orthogonal resources to the different users, instead successive interference cancellation (SIC) is performed As a result, it provides better spectral efficiency, supports more connected devices, achieves reduced transmission latency, higher cell-edge throughput and relaxed channel feedback because only the received signal strength is required [2]–[4]. We investigate how TX RHI only, receiver (RX) RHI only and joint TX/RX RHI at the source, relay, legitimate users, and eavesdropper, affect the secure performance of cooperative multi-user NOMA systems This is realized in terms of the corresponding IP and OP for which, exact analytical expressions are derived for the above impairment scenarios.
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