387 research outputs found
Capacity Comparison between MIMO-NOMA and MIMO-OMA with Multiple Users in a Cluster
In this paper, the performance of multiple-input multiple-output
non-orthogonal multiple access (MIMO-NOMA) is investigated when multiple users
are grouped into a cluster. The superiority of MIMO-NOMA over MIMO orthogonal
multiple access (MIMO-OMA) in terms of both sum channel capacity and ergodic
sum capacity is proved analytically. Furthermore, it is demonstrated that the
more users are admitted to a cluster, the lower is the achieved sum rate, which
illustrates the tradeoff between the sum rate and maximum number of admitted
users. On this basis, a user admission scheme is proposed, which is optimal in
terms of both sum rate and number of admitted users when the
signal-to-interference-plus-noise ratio thresholds of the users are equal. When
these thresholds are different, the proposed scheme still achieves good
performance in balancing both criteria. Moreover, under certain conditions,it
maximizes the number of admitted users. In addition, the complexity of the
proposed scheme is linear to the number of users per cluster. Simulation
results verify the superiority of MIMO-NOMA over MIMO-OMA in terms of both sum
rate and user fairness, as well as the effectiveness of the proposed user
admission scheme.Comment: accepted IEEE Journal on Selected Topics in Communications, June
2017, Keywords: Non-orthogonal multiple access (NOMA), multiple-input
multiple-output (MIMO), channel capacity, sum rate, fairness, user admission,
power allocatio
A Fair Individual Rate Comparison between MIMO-NOMA and MIMO-OMA
In this paper, we compare the individual rate of MIMO-NOMA and MIMO-OMA when
users are paired into clusters. A power allocation (PA) strategy is proposed,
which ensures that MIMO-NOMA achieves a higher individual rate for each user
than MIMO-OMA with arbitrary PA and optimal degrees of freedom split. In
addition, a special case with equal degrees of freedom and arbitrary PA for OMA
is considered, for which the individual rate superiority of NOMA still holds.
Moreover, it is shown that NOMA can attain better fairness through appropriate
PA. Finally, simulations are carried out, which validate the developed
analytical results
Securing Downlink Massive MIMO-NOMA Networks with Artificial Noise
In this paper, we focus on securing the confidential information of massive
multiple-input multiple-output (MIMO) non-orthogonal multiple access (NOMA)
networks by exploiting artificial noise (AN). An uplink training scheme is
first proposed with minimum mean squared error estimation at the base station.
Based on the estimated channel state information, the base station precodes the
confidential information and injects the AN. Following this, the ergodic
secrecy rate is derived for downlink transmission. An asymptotic secrecy
performance analysis is also carried out for a large number of transmit
antennas and high transmit power at the base station, respectively, to
highlight the effects of key parameters on the secrecy performance of the
considered system. Based on the derived ergodic secrecy rate, we propose the
joint power allocation of the uplink training phase and downlink transmission
phase to maximize the sum secrecy rates of the system. Besides, from the
perspective of security, another optimization algorithm is proposed to maximize
the energy efficiency. The results show that the combination of massive MIMO
technique and AN greatly benefits NOMA networks in term of the secrecy
performance. In addition, the effects of the uplink training phase and
clustering process on the secrecy performance are revealed. Besides, the
proposed optimization algorithms are compared with other baseline algorithms
through simulations, and their superiority is validated. Finally, it is shown
that the proposed system outperforms the conventional massive MIMO orthogonal
multiple access in terms of the secrecy performance
Performance analysis of spatial modulation aided NOMA with full-duplex relay
A spatial modulation aided non-orthogonal multiple access with full-duplex relay (SM-NOMA-FDR) scheme is proposed for the coordinated direct and relay transmission in this paper. Specifically, the signal of the near user is mapped to an M-ary modulated symbol and the signal of the far user is mapped to an SM symbol. The base station first transmits signals to the near user and relay via SM-NOMA, and then the relay decodes and retransmits the signal of the far user. An SM-assisted FDR is used in this scheme to improve the spectral efficiency while reducing energy consumption and making full use of the antenna resources at the relay, since SM only activates one antenna in each transmission. We derive the ergodic capacity and bit error rate of the proposed scheme over independent Rayleigh fading channels. Numerical results validate the accuracy of the theoretical analysis and show the superior performance of the proposed SM-NOMA-FDR scheme
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