14 research outputs found
Secure Transmission in NOMA-enabled Industrial IoT with Resource-Constrained Untrusted Devices
The security of confidential information associated with devices in the
industrial Internet of Things (IIoT) network is a serious concern. This article
focuses on achieving a nonorthogonal multiple access (NOMA)-enabled secure IIoT
network in the presence of untrusted devices by jointly optimizing the
resources, such as decoding order and power allocated to devices. Assuming that
the devices are resource-constrained for performing perfect successive
interference cancellation (SIC), we characterize the residual interference at
receivers with the linear model. Firstly, considering all possible decoding
orders in an untrusted scenario, we obtain secure decoding orders that are
feasible to obtain a positive secrecy rate for each device. Then, under the
secrecy fairness criterion, we formulate a joint optimization problem of
maximizing the minimum secrecy rate among devices. Since the formulated problem
is non-convex and combinatorial, we first obtain the optimal secure decoding
order and then solve it for power allocation by analyzing Karush-Kuhn-Tucker
points. Thus, we provide the closed-form global-optimal solution of the
formulated optimization problem. Numerical results validate the analytical
claims and demonstrate an interesting observation that the conventional
decoding order and assigning more power allocation to the weak device, as
presumed in many works on NOMA, is not an optimal strategy from the secrecy
fairness viewpoint. Also, the average percentage gain of about 22.75%, 50.58%,
94.59%, and 98.16%, respectively, is achieved by jointly optimized solution
over benchmarks ODEP (optimal decoding order, equal power allocation), ODFP
(optimal decoding order, fixed power allocation), FDEP (fixed decoding order,
equal power allocation), and FDFP (fixed decoding order, fixed power
allocation).Comment: 10 pages and 6 figure
Untrusted NOMA with Imperfect SIC: Outage Performance Analysis and Optimization
Non-orthogonal multiple access (NOMA) has come to the fore as a
spectral-efficient technique for fifth-generation and beyond communication
networks. We consider the downlink of a NOMA system with untrusted users. In
order to consider a more realistic scenario, imperfect successive interference
cancellation is assumed at the receivers during the decoding process. Since
pair outage probability (POP) ensures a minimum rate guarantee to each user, it
behaves as a measure of the quality of service for the pair of users. With the
objective of designing a reliable communication protocol, we derive the
closed-form expression of POP. Further, we find the optimal power allocation
that minimizes the POP. Lastly, numerical results have been presented which
validate the exactness of the analysis, and reveal the effect of various key
parameters on achieved pair outage performance. In addition, we benchmark
optimal power allocation against equal and fixed power allocations with respect
to POP. The results indicate that optimal power allocation results in improved
communication reliability.Comment: 6 pages, 5 figures, WCNC 202
Subcarrier Pairing as Channel Gain Tailoring: Joint Resource Allocation for Relay-Assisted Secure OFDMA with Untrusted Users
Joint resource allocation involving optimization of subcarrier allocation,
subcarrier pairing (SCP), and power allocation in a cooperative secure
orthogonal frequency division multiple access (OFDMA) communication system with
untrusted users is considered. Both amplify and forward (AF), and decode and
forward (DF) modes of operations are considered with individual power budget
constraints for source and relay. After finding optimal subcarrier allocation
for an AF relayed system, we prove the joint power allocation as a generalized
convex problem, and solve it optimally. Compared to the conventional channel
gain matching view, the optimal SCP is emphasized as a novel concept of channel
gain tailoring. We prove that the optimal SCP pairs subcarriers such that the
variance among the effective channel gains is minimized. For a DF relayed
system, we show that depending on the power budgets of source and relay, SCP
can either be in a subordinate role where it improves the energy efficiency, or
in a main role where it improves the spectral efficiency of the system. In an
AF relayed system we confirm that SCP plays a crucial role, and improves the
spectral efficiency of the system. The channel gain tailoring property of SCP,
various roles of SCP in improving the spectral and the energy efficiency of a
cooperative communication system are validated with the help of simulation
results
User-Pair Selection for QoS-Aware Secrecy Rate Maximization in Untrusted NOMA
Non-orthogonal multiple access (NOMA) has been recognized as one of the key
enabling technologies for future generation wireless networks. Sharing the same
time-frequency resource among users imposes secrecy challenges in NOMA in the
presence of untrusted users. This paper characterizes the impact of user-pair
selection on the secrecy performance of an untrusted NOMA system. In this
regard, an optimization problem is formulated to maximize the secrecy rate of
the strong user while satisfying the quality of service (QoS) demands of the
user with poorer channel conditions. To solve this problem, we first obtain
optimal power allocation in a two-user NOMA system, and then investigate the
user-pair selection problem in a more generalized four user NOMA system.
Extensive performance evaluations are conducted to validate the accuracy of the
proposed results and present valuable insights on the impact of various system
parameters on the secrecy performance of the NOMA communication system
Secrecy Outage Probability Analysis for Downlink NOMA with Imperfect SIC at Untrusted Users
Non-orthogonal multiple access (NOMA) has come to the fore as a spectrally
efficient technique for fifth-generation networks and beyond. At the same time,
NOMA faces severe security issues in the presence of untrusted users due to
successive interference cancellation (SIC)-based decoding at receivers. In this
paper, to make the system model more realistic, we consider the impact of
imperfect SIC during the decoding process. Assuming the downlink mode, we focus
on designing a secure NOMA communication protocol for the considered system
model with two untrusted users. In this regard, we obtain the power allocation
bounds to achieve a positive secrecy rate for both near and far users.
Analytical expressions of secrecy outage probability (SOP) for both users are
derived to analyze secrecy performance. Closed-form approximations of SOPs are
also provided to gain analytical insights. Lastly, numerical results have been
presented, which validate the exactness of the analysis and reveal the effect
of various key parameters on achieved secrecy performance.Comment: 5 pages, 5 figures, and EUSIPCO 202
Secrecy Outage Probability Analysis for Downlink Untrusted NOMA Under Practical SIC Error
Non-orthogonal multiple access (NOMA) serves multiple users simultaneously
via the same resource block by exploiting superposition coding at the
transmitter and successive interference cancellation (SIC) at the receivers.
Under practical considerations, perfect SIC may not be achieved. Thus, residual
interference (RI) occurs inevitably due to imperfect SIC. In this work, we
first propose a novel model for characterizing RI to provide a more realistic
secrecy performance analysis of a downlink NOMA system under imperfect SIC at
receivers. In the presence of untrusted users, NOMA has an inherent security
flaw. Therefore, for this untrusted users' scenario, we derive new analytical
expressions of secrecy outage probability (SOP) for each user in a two-user
untrusted NOMA system by using the proposed RI model. To further shed light on
the obtained results and obtain a deeper understanding, a high signal-to-noise
ratio approximation of the SOPs is also obtained. Lastly, numerical
investigations are provided to validate the accuracy of the desired analytical
results and present valuable insights into the impact of various system
parameters on the secrecy rate performance of the secure NOMA communication
system.Comment: 6 pages, 5 figures, GLOBECOM 202