Time: 1:15 PM to 2:15 PM
Venue: ESB 244
Speaker: Sridhan K S (EE13S068)
Guide: Dr. Sheetal Kalyani
GTC Members :
ABSTRACT: OFDM is one of the most important multi-carrier techniques in communications with the latest standards like LTE, LTE-Advanced communicating over OFDM. Many OFDM systems have large number of null sub-carriers called the Virtual Sub-carriers (VS’s) on either side of the frequency band to avoid power leakage into adjacent channels. The presence of these VS’s leads to loss of orthogonality and causes leakage of non-zero taps onto the zero-valued taps in channel estimation. Hence, obtaining accurate estimate of non-zero tap locations is tough. In this work, we try to understand how the VS’s affect channel estimation and try to overcome its effects. We propose to use a preamble symbol obtained by Discrete Prolate Spheroidal Sequence (DPSS) transformation instead of the DFT. The preamble symbol is designed so that leakage onto the VS’s can be controlled. With this preamble symbol, we obtain an unbiased channel estimate, which in-turn by thresholding, enables us to obtain accurate tap location estimates. We analytically show that as SNR increases our scheme accurately estimates the location of non-zero channel taps. This helps in obtaining accurate channel estimates. In the later part of this work, we explore the possibility of obtaining non-sample spaced channel estimation.