  Massive Machine-Type Communications (mMTC) are one of the three types of
services that should be supported by 5G networks. These are distinguished by
the need to serve a large number of devices which are characterized by
nonintensive traffic and low energy consumption. While the sporadic nature of
the mMTC traffic does not pose an exertion to efficient network operation,
multiplexing the traffic from a large number of these devices within the cell
certainly does. Therefore, planning carefully the network resources for this
traffic is of paramount importance. To do this, the statistics of the traffic
pattern that arrives at the base station should be known. To this end, in this
paper, we derive the distribution of the inter-arrival times of the traffic at
the base station from a general number of mMTC users within the cell, assuming
a generic distribution of the traffic pattern by individual users. We validate
our results on traces. Results show that adding more mMTC users in the cell
increases the variability of the traffic pattern at the base station almost
linearly, which is not the case with increasing the traffic generation rates.
