The communication device can perform hierarchical transfer learning (TL). The communication device may comprise: receiving information about channel characteristics from a plurality of user equipments including a first user equipment; mapping the plurality of user equipments to a plurality of TL levels and a plurality of groups for each of the plurality of TL levels on the basis of the information about the channel characteristics; and training a neural network of the first user equipment on the basis of the TL levels and the groups to which the plurality of user equipments is mapped. Training of the neural network of the first user equipment can comprise training a training portion for a first TL level from among TL levels to which the first user equipment is mapped.