Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: NOMA Aided Narrowband IoT for Machine Type Communications with User
  Clustering   To support Machine Type Communications (MTC) in next generation mobile
networks, NarrowBand-IoT (NB-IoT) has been released by the Third Generation
Partnership Project (3GPP) as a promising solution to provide extended coverage
and low energy consumption for low cost MTC devices. However, the existing
Orthogonal Multiple Access (OMA) scheme in NB-IoT cannot provide connectivity
for a massive number of MTC devices. In parallel with the development of
NB-IoT, Non-Orthogonal Multiple Access (NOMA), introduced for the fifth
generation wireless networks, is deemed to significantly improve the network
capacity by providing massive connectivity through sharing the same spectral
resources. To leverage NOMA in the context of NB-IoT, we propose a power domain
NOMA scheme with user clustering for an NB-IoT system. In particular, the MTC
devices are assigned to different ranks within the NOMA clusters where they
transmit over the same frequency resources. Then, we formulate an optimization
problem to maximize the total throughput of the network by optimizing the
resource allocation of MTC devices and NOMA clustering while satisfying the
transmission power and quality of service requirements. We prove the
NP-hardness of the proposed optimization problem. We further design an
efficient heuristic algorithm to solve the proposed optimization problem by
jointly optimizing NOMA clustering and resource allocation of MTC devices.
Furthermore, we prove that the reduced optimization problem of power control is
a convex optimization task. Simulation results are presented to demonstrate the
efficiency of the proposed scheme.

22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
0
The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an
32
The categories of this paper are: atom-ph
23
The categories of this paper are: solv-int
25
The categories of this paper are: patt-sol
2
The categories of this paper are: math
6
The categories of this paper are: astro-ph
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio