7 research outputs found
A Two-Phase Power Allocation Scheme for CRNs Employing NOMA
In this paper, we consider the power allocation (PA) problem in cognitive
radio networks (CRNs) employing nonorthogonal multiple access (NOMA) technique.
Specifically, we aim to maximize the number of admitted secondary users (SUs)
and their throughput, without violating the interference tolerance threshold of
the primary users (PUs). This problem is divided into a two-phase PA process:
a) maximizing the number of admitted SUs; b) maximizing the minimum throughput
among the admitted SUs. To address the first phase, we apply a sequential and
iterative PA algorithm, which fully exploits the characteristics of the
NOMA-based system. Following this, the second phase is shown to be quasiconvex
and is optimally solved via the bisection method. Furthermore, we prove the
existence of a unique solution for the second phase and propose another PA
algorithm, which is also optimal and significantly reduces the complexity in
contrast with the bisection method. Simulation results verify the effectiveness
of the proposed two-phase PA scheme
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
Bandwidth allocation in cooperative wireless networks: Buffer load analysis and fairness evaluation.
In modern cooperative wireless networks, the resource allocation is an issue of major significance. The cooperation of source and relay nodes in wireless networks towards improved performance and robustness requires the application of an efficient bandwidth sharing policy. Moreover, user requirements for multimedia content over wireless links necessitate the support of advanced Quality of Service (QoS) features. In this paper, a novel bandwidth allocation technique for cooperative wireless networks is proposed, which is able to satisfy the increased QoS requirements of network users taking into account both traffic priority and packet buffer load. The performance of the proposed scheme is examined by analyzing the impact of buffer load on bandwidth allocation. Moreover, fairness performance in resource sharing is also studied. The results obtained for the cooperative network scenario employed, are validated by simulations. Evidently, the improved performance achieved by the proposed technique indicates that it can be employed for efficient traffic differentiation. The flexible design architecture of the proposed technique indicates its capability to be integrated into Medium Access Control (MAC) protocols for cooperative wireless networks