Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Two-Dimensional Signal Space for Intensity-Modulated Channels   A two-dimensional signal space for intensity- modulated channels is
presented. Modulation formats using this signal space are designed to maximize
the minimum distance between signal points while satisfying average and peak
power constraints. The uncoded, high-signal-to-noise ratio, power and spectral
efficiencies are compared to those of the best known formats. The new formats
are simpler than existing subcarrier formats, and are superior if the bandwidth
is measured as 90% in-band power. Existing subcarrier formats are better if the
bandwidth is measured as 99% in-band power.

7
The categories of this paper are: hep-th
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph
29
The categories of this paper are: funct-an
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
3
The categories of this paper are: physics
16
The categories of this paper are: stat
0
The categories of this paper are: hep-ph
6
The categories of this paper are: astro-ph
26
The categories of this paper are: bayes-an
8
The categories of this paper are: hep-ex
32
The categories of this paper are: atom-ph