Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Cooperative Non-Orthogonal Multiple Access in 5G Systems   Non-orthogonal multiple access (NOMA) has recently received considerable
attention as a promising candidate for 5G systems. A key feature of NOMA is
that users with better channel conditions have prior information about the
messages of the other users. This prior knowledge is fully exploited in this
paper, where a cooperative NOMA scheme is proposed. Outage probability and
diversity order achieved by this cooperative NOMA scheme are analyzed, and an
approach based on user pairing is also proposed to reduce system complexity in
practice.

20
The categories of this paper are: acc-phys
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
16
The categories of this paper are: stat
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
21
The categories of this paper are: adap-org
6
The categories of this paper are: astro-ph
13
The categories of this paper are: quant-ph
27
The categories of this paper are: comp-gas
5
The categories of this paper are: gr-qc
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int
7
The categories of this paper are: hep-th