  Cellular network technology based device-to-device communication attracts
increasing attention for use cases such as the control of autonomous vehicles
on the ground and in the air. LTE provides device-to-device communication
options, however, the configuration options are manifold (leading to 150+
possible combinations) and therefore the ideal combination of parameters is
hard to find. Depending on the use case, either throughput, reliability or
latency constraints may be the primary concern of the service provider. In this
work we analyze the impact of different configuration settings of unsupervised
LTE device-to-device (sidelink) communication on the system performance. Using
a simulative approach we vary the length of the PSCCH period and the number of
PSCCH subframes and determine the impact of different combinations of those
parameters on the resulting latency, reliability and the interarrival times of
the received packets. Furthermore we examine the system limitations by a
scalability analysis. In this context, we propose a modified HARQ process to
mitigate scalability constraints. Our results show that the proposed reduced
HARQ retransmission probability can increase the system performance regarding
latency and interarrival times as well as the packet transmission reliability
for higher channel utilization.
