Nowadays, a revolutionary change has occurred in the technology especially in the communication technology. The entire system of communication has undergone a paradigm shift. It has evolved from the age of face to face communication to wired and finally to wireless one. Today's world is relying on wireless communication which requires no wire as such to connect to people all over the world. The wired networks are gradually transforming into wireless network; Wi-Fi (Wireless Fidelity) network is an example of such a network. Wi-Fi is a wireless communication system that uses the Orthogonal Frequency Division Multiplexing (OFDM) modulation scheme for digital transmission. OFDM is a type of multi-carrier modulation.Wireless digital communications is rapidly expanding, resulting in a demand for wireless systems that are reliable and have a high spectral efficiency. OFDM has a high tolerance to multi-path signals and is spectrally efficient making it a good candidate for future wireless communication systems. The aim of this project is to model and assess the performance of OFDM modulation scheme using Advanced Design System (ADS) tools. First of all, design a signal source using OFDM modulation. Then, this signal source is used to transmit through phase noise channel. At the receiver, measurement for bit error rate (BER) can be obtained. Compare the result obtained from ADS simulation with reference result or theory result. The results are fine and acceptable.