51 research outputs found
Blockchain based secure data handover scheme in non-orthogonal multiple access
Non-orthogonal multiple access (NOMA) with successive interference
cancellation receiver is considered as one of the most potent multiple access
techniques to be adopted in future wireless communication networks. Data
security in the NOMA transmission scheme is on much attention drawing issue.
Blockchain is a distributed peer-to-peer network enables a way of protecting
information from unauthorized access, tempering etc. By utilizing encryption
techniques of blockchain, a secured data communication scheme using blockchain
in NOMA is proposed in this paper. A two-phase encryption technique with key
generation using different parameter is proposed. In the first-phase data is
encrypted by imposing users' public key and in the second phase, a private key
of the base station (BS) is engaged for encryption. Finally, the superiority of
the proposed scheme over existing scheme is proven through a comparative study
based on the different features.Comment: Published in 2018 4th International Conference on Wireless and
Telematics (ICWT
User Clustering for STAR-RIS Assisted Full-Duplex NOMA Communication Systems
In contrast to conventional reconfigurable intelligent surface (RIS),
simultaneous transmitting and reflecting reconfigurable intelligent surface
(STAR-RIS) has been proposed recently to enlarge the serving area from 180o to
360o coverage. This work considers the performance of a STAR-RIS aided
full-duplex (FD) non-orthogonal multiple access (NOMA) communication systems.
The STAR-RIS is implemented at the cell-edge to assist the cell-edge users,
while the cell-center users can communicate directly with a FD base station
(BS). We first introduce new user clustering schemes for the downlink and
uplink transmissions. Then, based on the proposed transmission schemes
closed-form expressions of the ergodic rates in the downlink and uplink modes
are derived taking into account the system impairments caused by the self
interference at the FD-BS and the imperfect successive interference
cancellation (SIC). Moreover, an optimization problem to maximize the total
sum-rate is formulated and solved by optimizing the amplitudes and the
phase-shifts of the STAR-RIS elements and allocating the transmit power
efficiently. The performance of the proposed user clustering schemes and the
optimal STAR-RIS design are investigated through numerical resultsComment: arXiv admin note: text overlap with arXiv:2309.1503
Fairness Comparison of Uplink NOMA and OMA
In this paper, we compare the resource allocation fairness of uplink
communications between non-orthogonal multiple access (NOMA) schemes and
orthogonal multiple access (OMA) schemes. Through characterizing the
contribution of the individual user data rate to the system sum rate, we
analyze the fundamental reasons that NOMA offers a more fair resource
allocation than that of OMA in asymmetric channels. Furthermore, a fairness
indicator metric based on Jain's index is proposed to measure the asymmetry of
multiuser channels. More importantly, the proposed metric provides a selection
criterion for choosing between NOMA and OMA for fair resource allocation. Based
on this discussion, we propose a hybrid NOMA-OMA scheme to further enhance the
users fairness. Simulation results confirm the accuracy of the proposed metric
and demonstrate the fairness enhancement of the proposed hybrid NOMA-OMA scheme
compared to the conventional OMA and NOMA schemes.Comment: 6 pages, accepted for publication, VTC 2017, Spring, Sydne
User Pairing and Power Allocation for IRS-Assisted NOMA Systems with Imperfect Phase Compensation
In this letter, we analyze the performance of the intelligent reflecting
surface (IRS) assisted downlink non-orthogonal multiple access (NOMA) systems
in the presence of imperfect phase compensation. We derive an upper bound on
the imperfect phase compensation to achieve minimum required data rates for
each user. Using this bound, we propose an adaptive user pairing algorithm to
maximize the network throughput. We then derive bounds on the power allocation
factors and propose power allocation algorithms for the paired users to achieve
the maximum sum rate or ensure fairness. Through extensive simulations, we show
that the proposed algorithms significantly outperform the state-of-the-art
algorithms
Outage-constrained robust power allocation for downlink MC-NOMA with imperfect SIC
In this paper, we study power allocation for downlink multi-carrier non-orthogonal multiple access (MC-NOMA) systems and examine the effects of residual cancellation errors resulting from imperfect successive interference cancellation
(SIC) on the system performance. In the presence of random SIC errors, we study outage probability of minimum reserved rate for individual user and formulate outage-constrained robust optimization
to minimize the total transmit power. Since the problem is non-convex due to probabilistic constraints, complementary geometric programming (CGP) and arithmetic geometric mean approximation (AGMA) technique are employed to transform
it into a convex form. An efficient iterative algorithm with low computational complexity is developed to solve the optimization problem. Simulation results demonstrate the performance of
robust MC-NOMA with imperfect SIC and compare that to non-robust MC-NOMA and orthogonal multiple access (OMA) schemes
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