Impact of robust channel estimation for high mobility systems

Emerging technologies like LTE (long term evolution) and WiMAX (Worldwide Interoperability for Microwave Access) are advancing in order to respond the needs for future mobile wireless access systems, whereas the demand is continuously increasing the requirement on high data rate on every mobile application. In the third generation Partnership project -Long Term Evolution (3GPP LTE) of Fourth Generation (4G) provides greater speed compare with it is predecessor 3G and 2G. The higher data rate is achieved in the wireless environment by deployed OFDM (Orthogonal Frequency Division Multiple) and MIMO (Multiple Inputs and Multiple Outputs) technique. It employs smart selection and combining techniques in the receiver end to improve the signal quality. The sub-carrier fluctuates in different time slots with in an OFDM symbol as a cause of multipath fading (color noise environment). Here the priority is given to minimize the interference occurred among the symbols in the channels and compress the data stream for high speed digital data transmission. Estimating the channel as accurately as possible is essential. This paper constitutes for different channel estimation technique is implemented with OFDM and MIMO for high mobility. In this work an iterative channel estimation scheme is introduced that makes use of pilot symbols, Doppler spread information and previously estimated data symbols are utilized to estimate the channel accurately. The channel estimation techniques as Maximum Likelihood (ML), Minimum Mean Square (MMSE) and Zero Forcing (ZF) are utilized. ML estimation is used to estimate even the channel is in worst condition. If any symbol occurs with error then, the PIC-DSC (Parallel Interference Cancellation - Decision Statically combining) is involved in removing the unnecessary interference produced in the channel. The Performance and result analysis is done using MATLAB simulation.