A NOVEL TWO STAGE CARRIER FREQUENCY OFFSET ESTIMATION AND COMPENSATION SCHEME IN MULTIPLE INPUT MULTIPLE OUTPUT-ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING SYSTEM USING EXPECTATION AND MAXIMIZATION ITERATION

Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing (MIMO-OFDM) is a promising technique to handle impairments of multipath channel. Alternatively, one of its major drawbacks is drift in carrier frequency, called Carrier Frequency Offset (CFO). Due to CFO, Inter Carrier Interference (ICI) occurs and results in a large performance degradation. The study proposes a novel two stage CFO estimation and compensation technique based on Expectation and Maximization (EM) algorithm with an iterative scheme. Unlike other CFO estimation algorithm, in our proposed CFO estimator a search interval is computed in two stages, hence the estimated offset is more optimal. In the first stage, coarse CFO estimation is done whereas fine estimation is performed in the second stage. This two stage computation results in more accurate and faster convergent estimate. From the simulation results it is proved that the Bit Error Rate (BER) performance of proposed method is more close to ideal Cramer-Rao Lower Bound (CRLB) curve."