Apparatuses, methods, computer programs, and computer-readable media are disclosed. A network node defines two or more user device groups, one of the user device groups using a licensed frequency band and another using an unlicensed frequency band. Timing advance parameters of user devices are determined. The user devices are assigned into one of the user device groups based on comparison of the timing advance parameters in such a manner that if a magnitude of differences of timing advance parameters of the user devices having mutual machine-to-machine communications exceeds the a timing advance parameter of at least one user device communicating with the network node, the user devices having the mutual machine-to-machine communications are directed into the user device group using the unlicensed frequency band for decreasing interference.