In wireless communication, orthogonal frequency division multiplexing (OFDM) plays a major role because of its high transmission rate. Channel estimation and tracking have many different techniques available in OFDM systems. Among them, the most important techniques are least square (LS) and minimum mean square error (MMSE). In least square channel estimation method, the process is simple but the major drawback is it has very high mean square error. Whereas, the performance of MMSE is superior to LS in low SNR, its main problem is it has high computational complexity. If the error is reduced to a very low value, then an exact signal will be received. In this paper an extensive review on different channel estimation methods used in MIMO-OFDM like pilot based, least square (LS) and minimum mean square error method (MMSE) and least minimum mean square error (LMMSE) methods and also other channel estimation methods used in MIMO-OFDM are discussed.
Most of the commercial goods are transported using railway trains and therefore, any problem in above network has the capacity to incur damage to the economy of that country. This model illustrates a cost effective yet robust solution to the issues related to railway crack detection. The project discusses the technical and design aspects in details alongside a better crack detection algorithm. The model also presents data related to all the components used in this system. The currently prevailing solution in the detection of cracks in rails involve periodic maintenance connected to occasional monitoring method like visual inspection, ultrasonic inspection, eddy current and laser methods
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