Channel Estimation In Mobile Wireless Systems

Nevertheless due to channel fading and the Doppler shifts caused by user mobility a common problem in wireless systems, additional technologies are needed to combat the multipath propagation fading and Doppler shifts. Time Variant channel estimation is one of such crucial method used to improve the performance of the modern wireless systems, including Doppler spread and multipath spread. Themost important of mobile channel is channel estimation which is a method used to significantly improve the performance of the system especially for4G and long Term Evolution (LTE) systems. This is one of the way to estimate the time varying channel frequency response for the OFDM symbol. The technique use in time variant channelfor estimation is using Discrete Prolate Spheroidal Sequences (DPSS) is a useful channel estimation method in mobile wireless communication for accurately estimating of transmitted information.The main advantage of Discrete ProlateS pheroidal Sequence or slepian basis expansion is allowing more precise representation of high mobility in mobile wireless channels with low complexity. Communication systems such as the fourth generation cellular wireless standard (4G) which has already introduced to different countries together with the long Term Evolution can use channel estimation techniques for providing high data rate in modern mobile wireless communication systems. The important of this paper is to Test the proposed method, Time Variant Channel Estimation using Discrete Prolate Spheroidal Sequence to model the WINNER Phase II Model. Time Variant subcarriers coefficients are expanded in terms of Orthogonal DPS Sequences, referred to as Slepian Basis Expansions. Both Slepian Basis expansion and DPS Sequence measuring range of the low dimensional subspace of time and band limited as itshowed. This can be measured by using just two system parameters the maximum Doppler frequency VDmax and K, where the number of basis function of length M=256. In this paper we are focused to investigate the Power Spectrum and Channel gain caused by Doppler spread of the WINNER Phase II Channel together with linear fitting of curves for both the Slepian and Fourier basis expansion models. It also investigates the Mean Square Error (MSE) using the least square (LS) method. The investigation was carried out by simulation, which shows that the spectrum of the maximum velocity of the user mobile wireless channel is upper bounded by the maximum normalized one sided Doppler Frequency. The value of the maximum Doppler bandwidthyVDmax of the WINNER model is exactly the same value as DPS Sequences. And also we take into consideration of the Power Spectrum of the WINNER model following the illustration that the slepian basis expansion is more applicable in the WINNER Model than that of the Fourier Basis Expansion.