The basic structure of the UAN framework is shown below:
The Mac and Phy layers are the lower layers of each node. Multiple nodes all will link to the same channel, and the channel is associated with a propagation model. In the UAN framework, the channel will compute the path loss and noise associated with itself. Thus, the channel will report a packet with a valid SNR to the PHY. The PHY layer is responsible for determining SINR and wether the detected packet is able to be successfully received. Packets received successfully are then reported to the MAC layer. This is a departure from standard NS2 where MAC layers detect collisions and all arriving packets are reported to the higher level.
1.5.1