A Review Based on Channel Estimation for Optical - Orthogonal Frequency Division Multiplexing

Abstract

Optical -Orthogonal Frequency Division Multiplexing (OFDM) system generally employ in several communication devices such as telephone, radio, television, internet and so on. In the present days, the optical OFDM is one of the significant methods for an effective communication system. In communication technique, the channel estimation plays a major role in finding the characteristics of the channel based on the received data value. In order to manage the communication data, most of the researchers focused on the channel estimation by using different techniques like Minimum Mean Square (MMSE), Least Square, blind, semi-blind and also developed new methodologies in the coherent optical OFDM. This review paper analysed the research works based on the channel estimation algorithms of an optical OFDM and also examined the major limitation of these techniques. This paper will help the researchers to give a better solution for the present drawbacks in the coherent optical OFDM system.Channel estimation techniques commonly categorize as semi-blind, blind, Pilot Aided (PA) channel estimations. The blind channel estimation performs by utilizing the statistics of received data, virtual carriers, cyclic prefix, and received diversity. That blind estimations commonly require the channel to be constant for a huge number of blocks. So, the blind channel estimation approach is not suitable for large mobility applications. The topmost communication standards such as Long-Term Evaluations (LTEs) and digital video broadcasting has increased the system efficiency by using the pilot channel estimation techniques. In large mobility channel estimation, each stage has individual challenges and features due to a long time dispersion, and the fast time-variation of the channels [11]. General procedure for the Channel EstimationPresently most of the communication systems require channel estimation for symbol detection and equalization process. It improves by employing dedicated pilot symbol, which consumes a non-negligible part of power resources and throughput for huge dimensional device/system. The LS approach based channel estimation technique is most suitable for other optical OFDM systems. The physical Visible Light Communication (VLC) channel scheme includes diffuse