785 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
On the Performance Gain of NOMA over OMA in Uplink Communication Systems
In this paper, we investigate and reveal the ergodic sum-rate gain (ESG) of
non-orthogonal multiple access (NOMA) over orthogonal multiple access (OMA) in
uplink cellular communication systems. A base station equipped with a
single-antenna, with multiple antennas, and with massive antenna arrays is
considered both in single-cell and multi-cell deployments. In particular, in
single-antenna systems, we identify two types of gains brought about by NOMA:
1) a large-scale near-far gain arising from the distance discrepancy between
the base station and users; 2) a small-scale fading gain originating from the
multipath channel fading. Furthermore, we reveal that the large-scale near-far
gain increases with the normalized cell size, while the small-scale fading gain
is a constant, given by = 0.57721 nat/s/Hz, in Rayleigh fading
channels. When extending single-antenna NOMA to -antenna NOMA, we prove that
both the large-scale near-far gain and small-scale fading gain achieved by
single-antenna NOMA can be increased by a factor of for a large number of
users. Moreover, given a massive antenna array at the base station and
considering a fixed ratio between the number of antennas, , and the number
of users, , the ESG of NOMA over OMA increases linearly with both and
. We then further extend the analysis to a multi-cell scenario. Compared to
the single-cell case, the ESG in multi-cell systems degrades as NOMA faces more
severe inter-cell interference due to the non-orthogonal transmissions.
Besides, we unveil that a large cell size is always beneficial to the ergodic
sum-rate performance of NOMA in both single-cell and multi-cell systems.
Numerical results verify the accuracy of the analytical results derived and
confirm the insights revealed about the ESG of NOMA over OMA in different
scenarios.Comment: 51 pages, 7 figures, invited paper, submitted to IEEE Transactions on
Communication
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
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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