Preamble Design and Iterative Channel Estimation for OFDM/Offset QAM System

Abstract

In present of multi-path effect, the inter symbol interference (ISI) always exists in the OFDM/OQAM system and the preamble based channel estimation for the conventional orthogonal frequency division multiplex with cyclic prefix (CP-OFDM) is not feasible any more. Considering the characteristic of the extended Gaussian function (EGF), we propose two modified preamble based channel estimation by adding zero-value guard symbols, which are located at both sides (method A) and the left side (method B) of preamble reference symbol. Compared with the CP-OFDM system, the proposed preamble based channel estimation achieves 2dB improvement. Furthermore, we shorten the preamble without zero-value guard symbol to improve the spectrum efficiency. Unfortunately, the residual inter symbol interference (ISI) from neighbor symbols degrade the channel estimation performance. We propose an iterative channel estimation method for OFDM/OQAM system to remove the residual ISI. Simulation results demonstrate that those proposed preamble design and iterative channel estimation methods are effective for OFDM/OQAM system.