Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On Constellations for Physical Layer Network Coded Two-Way Relaying   Modulation schemes for two-way bidirectional relay network employing two
phases: Multiple access (MA) phase and Broadcast (BC) phase and using physical
layer network coding are currently studied intensively. Recently, adaptive
modulation schemes using Latin Squares to obtain network coding maps with the
denoise and forward protocol have been reported with good end-to-end
performance. These schemes work based on avoiding the detrimental effects of
distance shortening in the effective receive constellation at the end of the MA
phase at the relay. The channel fade states that create such distance
shortening called singular fade states, are effectively removed using
appropriate Latin squares. This scheme as well as all other known schemes
studied so far use conventional regular PSK or QAM signal sets for the end
users which lead to the relay using different sized constellations for the BC
phase depending upon the fade state. In this work, we propose a 4-point signal
set that would always require a 4-ary constellation for the BC phase for all
the channel fade conditions. We also propose an 8-point constellation that
gives better SER performance (gain of 1 dB) than 8-PSK while still using 8-ary
constellation for BC phase like the case with 8-PSK. This is in spite of the
fact that the proposed 8-point signal set has more number of singular fade
states than for 8-PSK.

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The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
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The categories of this paper are: q-fin
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The categories of this paper are: cond-mat
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The categories of this paper are: physics
19
The categories of this paper are: eess
0
The categories of this paper are: hep-ph
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The categories of this paper are: dg-ga
14
The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc
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The categories of this paper are: hep-ex
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The categories of this paper are: supr-con
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The categories of this paper are: nucl-ex
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The categories of this paper are: alg-geom
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The categories of this paper are: adap-org
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The categories of this paper are: funct-an