A Study On Roles And Applications Of Cyclic Prefix In OFDM System

Data transmission in mobile channel with high speed and reliability is required in future mobile communication system. The 4th mobile communication system is expected to provide high-quality broadband services using the minimum possible resources (bandwidth, power, complexity). Toward this end, an appropriate transmission technique that matches the mobile channel characteristics is required. Taking many uncertain factors in mobile communication channel into account, OFDM (orthogonal frequency-division multiplexing) is one of the promising techniques that meet such requirements with reasonable complexity. OFDM is one of multi-carrier digital modulation techniques, in which a single high data rate data stream is transmitted using a number of lower data rate sub carriers, it has many properties, such as robustness to multi-path fading, high data rate transmission capability with high bandwidth efficiency, and so on.This paper introduces the principle, the merit and shortcoming of OFDM and analyzes some key technologies in OFDM system. Then analyzes the performance of overcoming inter symbol interference (ISI) and inter channel interference (ICI) of the guard interval (GI) and the cyclic prefix (CP). At the same time, It emphasizes application of cyclic prefix in signal recovery. In a traditional OFDM system, during signal detection at the receiver, the cyclic prefix is simply deleted and the remaining portion of the received signal used for processing. hence, some useful information in the CP is not used. In this paper, we propose a LS-based method that uses the CP to help signal recovery and present its simulation result. As it turns out, for long CP, our method produces lower symbol error rate than the traditional method.