  Successful network deployment of the Internet of Things (IoT) requires many
critical system design considerations. This paper highlights how an LTE system
supporting Cat-M devices can be engineered to deal with the numerous
constraints the 3GPP standard imposes for this new device type. Fundamental
changes to the control channels, control and data timing relationships, the
need to support half-duplexing, and variable repetition lengths pose
non-trivial challenges, particularly when attempting to satisfy the critical
coverage KPI for Cat-M devices while at the same time preserving the capacity
KPI for legacy LTE devices. In addition, the nature of IoT traffic is
fundamentally different than legacy LTE data, requiring changes to existing
system parameters and MAC algorithms. Finally, we will touch upon the topic of
supporting voice over IP traffic on Cat-M devices and the challenges therein.
