  In the design of closed-loop networked control systems (NCSs), induced
transmission delay between sensors and the control station is an often-present
issue which compromises control performance and may even cause instability. A
very relevant scenario in which network-induced delay needs to be investigated
is costly usage of communication resources. More precisely, advanced
communication technologies, e.g. 5G, are capable of offering latency-varying
information exchange for different prices. Therefore, induced delay becomes a
decision variable. It is then the matter of decision maker's willingness to
either pay the required cost to have low-latency access to the communication
resource, or delay the access at a reduced price. In this article, we consider
optimal price-based bi-variable decision making problem for single-loop NCS
with a stochastic linear time-invariant system. Assuming that communication
incurs cost such that transmission with shorter delay is more costly, a
decision maker determines the switching strategy between communication links of
different delays such that an optimal balance between the control performance
and the communication cost is maintained. In this article, we show that, under
mild assumptions on the available information for decision makers, the
separation property holds between the optimal link selecting and control
policies. As the cost function is decomposable, the optimal policies are
efficiently computed.
