Physical Layer Modeling

The Physical Layer (PHY) is serving as the interface between the Data Link Layer (DLL) and the environment. Accordingly, it defines the relation between the device and the physical medium. In wireless systems, the general task of the PHY is to convert bit streams into radio waves and vice versa. Though the transmitter and the receiver are dual, they are comprised of different components in the physical layer. The transmitter takes digital input in form of (payload) bits and converts them into an analog signal, generally around a given carrier frequency which is then radiated via the antenna. At the receiver, this analog signal which has been distorted during the propagation is then converted back into a (payload) bit stream. The general goal of the PHY is to ensure that the bit stream at the transmitter and at the receiver are identical. This is a very challenging task as the wireless channel (see Section 11) can distort and corrupt the analog signal in many different, random ways. In the following, we first provide an overview of the different functionalities of the PHY at the transmitter and receiver as applied in most common standards today like for cellular networks (such as Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS), Long Term Evolution (LTE)) or local/metropolitan area networks (e.g. IEEE 802.11, IEEE 802.16) as well as for broadcast networks (Digital Audio Broadcasting (DAB), Digital Video Broadcasting (DVB)). Then we discuss common simulation approaches used in the PHY and their shortcomings for network simulation. Finally, we comment on ways to include selected aspects of the PHY in network simulation models.