1. PHY designates the lowest protocol layer specified by the OSI Network Model. It deals primarily with transmission of the raw bit stream over the PHYsical transport medium. In the case of wireless LANs, the transport medium is free space. The PHY defines such parameters as data rates, modulation method, signaling parameters and transmitter/receiver synchronization. Within an actual radio implementation, the PHY corresponds to the radio front end and baseband signal processing sections.