  Real-time monitoring applications have Internet-of-Things (IoT) devices sense
and communicate information (status updates) to a monitoring facility. Such
applications desire the status updates available at the monitor to be fresh and
would like to minimize the age of delivered updates. Networks of such devices
may share wireless spectrum with WiFi networks. Often, they use a CSMA/CA based
medium access similar to WiFi. However, unlike them, a WiFi network would like
to provide high throughputs for its users. We model the coexistence of such
networks as a repeated game with two players, an age optimizing network (AON)
and a throughput optimizing network (TON), where an AON aims to minimize the
age of updates and a TON seeks to maximize throughput. We define the stage
game, parameterized by the average age of the AON at the beginning of the
stage, and derive its mixed strategy Nash equilibrium (MSNE). We study the
evolution of the equilibrium strategies over time, when players play the MSNE
in each stage, and the resulting average discounted payoffs of the networks. It
turns out that it is more favorable for a TON to share spectrum with an AON in
comparison to sharing with another TON. The key to this lies in the MSNE
strategy of the AON that occasionally refrains all its nodes from transmitting
during a stage. Such stages allow the TON competition free access to the
medium.
