Massive Machine-Type Communications (mMTC) are one of the service types supported by 5G. These are characterized by the need to serve a large number of devices that have only sporadic traffic and which have low-energy consumption. While the non-intensive nature of the traffic does not pose much strain on efficient network planning, the requirement to serve a large number of devices certainly does. With the network resources being limited and the competition between users in the cell, an important question that arises is that of admission control, so that the admitted users can be successfully served by the network. To this end, in this paper, we provide the analysis that leads to an admission control policy. We do this for two types of users in terms of their traffic intensities and channel conditions: 1) homogeneous users, and 2) heterogeneous users. We validate our results on a trace. Results show that the number of admitted users depends on the traffic pattern but not on the channel conditions. An increase in traffic intensity by 15 times can decrease the number of admitted users by 15 times.