Blind carrier frequency offset estimation for multicarrier systems
Abstract
A Multicarrier Communication (MCM) system such as an Orthogonal Frequency
Division Multiplexing OFDM or Discrete Multi Tone (DMT) system has been shown to be an
effective technique to combat multipath fading in wireless communications. OFDM is a
modulation scheme that allows digital data to be efficiently and reliably transmitted over a radio
channel, even in multipath environments. OFDM transmits data by using a large number of
narrow bandwidth carriers. These carriers are regularly spaced in frequency, forming a block of
spectrum. The frequency spacing and time synchronization of the carriers is chosen in such a
way that the carriers are orthogonal, meaning that they do not cause interference to each other. In
spite of the success and effectiveness of the OFDM systems, it suffers from two well known
draw backs: large Peak to Average Power Ratio (PAPR) and high sensitivity to Carrier
Frequency Offset (CFO). The presence of the CFO in the received carrier will lose orthogonality
among the carriers and because the CFO causes a reduction of desired signal amplitude in the
output decision variable and introduces Inter Carrier Interference (ICI). It then brings up an
increase of Bit Error Rate (BER). This makes the problem of estimating the CFO an attractive
and necessary research problem. In this dissertation blind estimation techniques will be proposed
to estimate the offset parameter.
Description
Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Electrical and Computer Engineering