38 research outputs found
On the Performance of NOMA with Hybrid ARQ
In this paper, we investigate the outage performance of hybrid automatic
repeat request with chase combining (HARQ-CC) assisted downlink non-orthogonal
multiple access (NOMA) systems. A closed-form expression of the individual
outage probability and the diversity gain are obtained firstly. Based on the
developed analytical outage probability, a tradeoff between the minimum number
of retransmissions and the transmit power allocation coefficient is then
provided for a given target rate. The provided simulation results demonstrate
the accuracy of the developed analytical results. Moreover, it is shown that
NOMA combined with the HARQ-CC can achieve a significant advantage when only
average channel state information is known at the transmitter. Particularly,
the performance of the user with less transmit power in NOMA systems can be
efficiently improved by utilizing HARQ-CC
Enabling Technologies for Ultra-Reliable and Low Latency Communications: From PHY and MAC Layer Perspectives
© 1998-2012 IEEE. Future 5th generation networks are expected to enable three key services-enhanced mobile broadband, massive machine type communications and ultra-reliable and low latency communications (URLLC). As per the 3rd generation partnership project URLLC requirements, it is expected that the reliability of one transmission of a 32 byte packet will be at least 99.999% and the latency will be at most 1 ms. This unprecedented level of reliability and latency will yield various new applications, such as smart grids, industrial automation and intelligent transport systems. In this survey we present potential future URLLC applications, and summarize the corresponding reliability and latency requirements. We provide a comprehensive discussion on physical (PHY) and medium access control (MAC) layer techniques that enable URLLC, addressing both licensed and unlicensed bands. This paper evaluates the relevant PHY and MAC techniques for their ability to improve the reliability and reduce the latency. We identify that enabling long-term evolution to coexist in the unlicensed spectrum is also a potential enabler of URLLC in the unlicensed band, and provide numerical evaluations. Lastly, this paper discusses the potential future research directions and challenges in achieving the URLLC requirements
Dynamic Non-Orthogonal Multiple Access (NOMA) and Orthogonal Multiple Access (OMA) in 5G Wireless Networks
In this paper, facilitated via the flexible software defined structure of the
radio access units in 5G, we propose a novel dynamic multiple access technology
selection among orthogonal multiple access (OMA) and non-orthogonal multiple
access (NOMA) techniques for each subcarrier. For this setup, we formulate a
joint resource allocation problem where a new set of access technology
selection parameters along with power and subcarrier are allocated for each
user based on each user's channel state information. Here, we define a novel
utility function taking into account the rate and costs of access technologies.
This cost reflects both the complexity of performing successive interference
cancellation and the complexity incurred to guarantee a desired bit error rate.
This utility function can inherently demonstrate the trade-off between OMA and
NOMA. Due to non-convexity of our proposed resource allocation problem, we
resort to successive convex approximation where a two-step iterative algorithm
is applied in which a problem of the first step, called access technology
selection, is transformed into a linear integer programming problem, and the
nonconvex problem of the second step, referred to power allocation problem, is
solved via the difference-of-convex-functions (DC) programming. Moreover, the
closed-form solution for power allocation in the second step is derived. For
diverse network performance criteria such as rate, simulation results show that
the proposed new dynamic access technology selection outperforms
single-technology OMA or NOMA multiple access solutions.Comment: 28 pages, 6 figure
Dynamic non-orthogonal multiple access (NOMA) and orthogonal multiple access (OMA) in 5G wireless networks
In this paper, a novel dynamic multiple access
technology selection among orthogonal multiple access (OMA)
and non-orthogonal multiple access (NOMA) techniques is proposed. For this setup, a joint resource allocation problem is
formulated in which a new set of access technology selection
parameters along with power and subcarrier are allocated for
each user based on each user’s channel state information. Here,
a novel utility function is defined to take into account the
rate and costs of access technologies. This cost reflects both
the complexity of performing successive interference cancellation
and the complexity incurred to guarantee a desired bit error
rate. This utility function can inherently capture the tradeoff
between OMA and NOMA. Due to non-convexity of the proposed
resource allocation problem, a successive convex approximation
is developed in which a two-step iterative algorithm is applied. In
the first step, called access technology selection, the problem is
transformed into a linear integer programming problem, and
then, in the second step, a nonconvex problem, referred to
power allocation problem, is solved via the difference-of-convexfunctions (DC) programming. Moreover, the closed-form solution
for power allocation in the second step is derived. For diverse
network performance criteria such as rate, simulation results
show that the proposed new dynamic access technology selection
outperforms single-technology OMA or NOMA multiple access
solutions