Software-defined radio implementation of OFDM

Abstract

Wireless communications is by any measure the fastest growing segment of the communications industry. Cellular phones, Wireless Local Area Networks (WLANs), Smart Homes and telemedicine are some applications that make extensive use of wireless communications.

Orthogonal Frequency Division Multiplexing (OFDM) is a modulation that has been applied to a wide variety of applications and is adopted in many recently standardized broadband communication systems. OFDM is an appealing technique for achieving high-bit-rate data transmision, due to its robustness against the multipath fading and Inter Symbol Interference. Since the OFDM transmission is vulnerable to time and frequency offsets, accurate estimation of these parameters is one of the most important tasks of the OFDM receiver. In this thesis, we implement a time synchronization algorithm based on correlation of two identical parts of an OFDM pilot symbol. In addition, knowledge of the channel in the transmitter is very useful for effective transmission and/or interference mitigation (especially in static environments). Thus, channel feedback is utilized throughout the experiments conducted for this thesis. The experiments were conducted on a software-defined-radio (SDR) testbed based on the Universal Software Radio Peripheral (USRP).