IJSRD - International Journal for Scientific Research & Development| Vol. 3, Issue 04, 2015 | ISSN (online): 2321-0613 All rights reserved by www.ijsrd.com 3234 Performance Analysis of Discrete Fourier Transform based Channel Estimation in MIMO-OFDM System Raspinderjit Kaur Kahlon 1 Gurpreet Singh Walia 2 Anu Sheetal 3 1 Student 2,3 Assistant Professor 1,2,3 Department of Electronics & Communication Engineering 1,2,3 GNDU Regional Campus Gurdaspur, India Abstract— Today wireless communication systems is using OFDM combined with MIMO known as MIMO-OFDM system providing higher spectrum efficiency and robustness. The main challenge in this is to get accurate channel estimation to detect the channel state information to process and equalize the received signal. The main objective of this paper is to give some techniques and analysis for channel estimation in MIMO-OFDM systems, regarding the influence of various system parameters on the channel estimation error and the final performance of the system. Key words: MIMO-OFDM, LS, MMSE, DFT, Channel estimation I. INTRODUCTION High data rate demands in wireless communication have gained interest nowadays. Orthogonal Frequency Division Multiplexing (OFDM) has attained a lot of importance due to its high data rate transmission with high bandwidth efficiency, simple implementation and robustness against frequency-selective fading and multi-path delay. Inter Symbol Interference (ISI) introduced in multipath channel is overcome by OFDM. This technique is used in wireless LAN standards such as American IEEE802.11a and European HIPERLAN/2 , in several digital multimedia communications standards like WiFi , LTE(Long Term Evolution) , DVB-T(Digital Video Broadcasting – Terrestrial)DVB-T2, Wi-Ma(Worldwide Interoperability for Microwave Access) and others [1]. Combining OFDM with multiple antennas has provided increase in capacity i.e transmitter and receiver diversity known as MIMO-OFDM [2][3]. MIMO (multiple Inputs and Multiple Outputs) use multiple antennas for transmission and multiple antennas for reception of signal. Design scheme depends upon system using MIMO-OFDM provides robustness against frequency-selective and/or obtaining multiplexing gain and time-variant channels. Such systems rely upon the prior knowledge of channel estimation information (CSI) at the receiver before transmission of channel. The main target of the paper is to analysis the present channel estimation techniques in MIMO-OFDM system and to evaluate the performance of the channel estimation technique. All the performance will be evaluated using MATLAB. Parameters which are used to evaluate the performance are SNR (Signal to Noise Ratio) and Symbol Error Rate. II. MIMO-OFDM SYSTEM MODEL MIMO system employs multiple antennas at the transmitter and receiver side. The system has   transmitter antennas and   receiver antennas in the figure. The signal transmitted by   transmitter antennas is received by   receiver antennas. Data symbols are mapped considering modulation type at the transmitter side. To estimate channels pilot symbols are inserted and at each transmitter antenna IFFT is taken .Then to prevent inter symbol interference (ISI) cyclic prefix is added. The   transmitter antenna of the transmitted symbol includes pilot tones,   (k), and data symbols. After removing cyclic prefix at the   receiver antenna and taking FFT, the channel is estimated in the channel estimation block and the signal is demodulated. Detection in MIMO requires the knowledge of channel. Practically the channel estimation is done by transmitting training pilot symbols which are known by the receiver. The performance of the system depends on the channel estimation and on the number of pilot symbols being transmitted. Different channel estimation techniques are used to obtain the channel state information (CSI). The different techniques are training based channel estimation, blind channel estimation and semi blind channel estimation. Fig. 1: Simplified block diagram of MIMO-OFDM system.