Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fronthauling for 5G LTE-U Ultra Dense Cloud Small Cell Networks   Ultra dense cloud small cell network (UDCSNet), which combines cloud
computing and massive deployment of small cells, is a promising technology for
the fifth-generation (5G) LTE-U mobile communications because it can
accommodate the anticipated explosive growth of mobile users' data traffic. As
a result, fronthauling becomes a challenging problem in 5G LTE-U UDCSNet. In
this article, we present an overview of the challenges and requirements of the
fronthaul technology in 5G \mbox{LTE-U} UDCSNets. We survey the advantages and
challenges for various candidate fronthaul technologies such as optical fiber,
millimeter-wave based unlicensed spectrum, Wi-Fi based unlicensed spectrum, sub
6GHz based licensed spectrum, and free-space optical based unlicensed spectrum.

23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
24
The categories of this paper are: dg-ga
20
The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph
13
The categories of this paper are: quant-ph
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
16
The categories of this paper are: stat