  In this paper the throughput and energy efficiency of an unlicensed machine
type communications network is studied. If an outage event happens in the
network, there is a possibility for packet retransmissions in order to obtain a
lower error probability. The model consist of a network with two types of
users, Licensed and unlicensed users. The licensed users allocated uplink
channel is also used by the unlicensed users. However, it is done in a way that
no harm is done to the licensed users' transmission from sharing the same
channel with the unlicensed users. However, licensed users' transmission causes
interference on the unlicensed network. Poisson point process is used here to
model the location of the nodes and the effect of interference on the network.
We study how different factors such as number of retransmissions, SIR threshold
and outage can effect the throughput and energy efficiency of the network.
Throughput and energy efficiency are also both studied in constrained
optimization problems where the constraints are the SIR threshold and number of
retransmission attempts. We also show why it is important to use limited
transmissions and what are the benefits.
