Abstract- In wireless communication, higher data rates can be achieved by increased or more efficient use of bandwidth and transmitting power. A key technique for spectral optimization is Orthogonal Frequency Division Multiplexing (OFDM). OFDM is a technique proposed for high-speed wireless LAN by the European Telecommunication Standards Institute and IEEE which is being considered for 4G mobile. OFDM technology is described for physical layer of proposed WirelessLAN standard whose data rate ranges from 6 to 54 Mbit/s depending on Quality of Service (QoS). It is designed to provide Wireless Local Loop (WLL) to core networks, e.g. Asynchronous Transfer Mode, GSM/UMTS or any IP-based multimedia network. Data rate, coding rate and modulation type are determined by the link adoption scheme automatically depending on the channel conditions. There are several ways to utilize the frequency band in a flexible way so that the available bandwidth is utilized to maximal efficiency. These access techniques uses a small portion of available energy with low power spectral density, high data transmission rates, less intercarrier interference and efficient use of bandwidth. The main cause of interference in OFDM system is channel fading, and all the errors are in transmission occurred due to effects of channel. One method that can be implemented to overcome this problem is by introducing channel coding. Channel encoding is applied by adding redundant bits to the transmitted data. The redundant bits increase raw data used in the link and therefore, increase the bandwidth requirement. So, if noise or fading occurred in the channel, some data may still be recovered at the receiver. While at the receiver, channel decoding is used to detect or correct errors that are introduced to the channel. To design an WLAN system with Rectangular QAM Baseband Modulator and OFDM as a multiple access technique. Then, analyze this system with to reduce the interference and improve the BER of system.

Keywords- WLAN, BER, OFDM.

| DOI: 10.17148/IARJSET.2021.8323