Low Complexity Channel Equalization in OFDM for High Speed Mobility System with High Frequency Mobile Network Technologie

In a traditional orthogonal frequency division multiplexing (OFDM) wireless communication system, a guard interval using cyclic prefix is injected to avoid an inter-symbol interference (ISI) and an inter-carrier interference (ICI). This approach has been proven to work well, however, only with time-invariant channels wherein a high speed mobility element is not considered. Furthermore, a transmission in the OFDM system is considered a low efficiency due to the use of a large percentage of pilot data for channel estimation.;In this research, an enhanced channel equalization in a multi-path propagation environment at a high frequency mobile network technologies is proposed. The multi-path propagation resulting from the variety of signal paths that may exist between the transmitter and receiver can give a rise to an interference in a variety of ways including distortion of the signal, loss of data and fading. These paths are created as a result of reflections from buildings, mountains, or other reflective surfaces. Having a high speed mobility system with high frequency mobile network technologies such as but not limited to 4G network lead to a frequency selective channel in the frequency domain and Inter-symbol Interference in the time domain. Furthermore, this phenomenon, i.e.high speed mobility causes a Doppler shift in which results into a time variant and frequency selective channel.;Thus, we present a wireless communication channel scenario that is characterized and modeled by a high relative velocity between transmitter and receiver, and fast changes of environment conditions for wave propagation. Furthermore, we present a method for enhancing the equalization of such dynamic channel. Thus a dynamic channel is developed utilizing Jakes and an auto-regressive models (AR). More specifically, the enhanced equalization method we are proposing is a combination of a multi-stage time and frequency domain equalizer with a feed-forward loop. Inserting pilot data at the transmitter and using said pilot data to estimate the channel in time domain. The addition of the feed-forward is utilized to capture a part of the received signal, then extracting the channel information while the signal is being delayed until the information is obtained. The estimated channel is forwarded to the MMSE equalizer. The first stage of the multi-stage equalizer is using pilot data as measurement data in the frequency domain. The second stage is to convert the measurement data to the time domain. In the third stage, we estimate the channel using the pilot data and use it as measurement data in the time domain, i.e. input to a Kalman filter. In OFDM system, the consecutive blocks for the channel coefficients for each tap in time domain are not totally independent, but partially correlated. Such correlation can improve the channel estimation when taken into an account. Using the Kalman filter, we can extract this information from previous blocks and use them for the newly arrived one, and perform a betterchannelestimation. Inthefourthstage,weusetheoutputoftheKalman filter as a feed-forward to the frequency equalizer for each subcarrier in which the data is converted from time domain to frequency domain.;The underlying wok presents a unified approach to the equalization approach that employs both time and frequency domains data to enhance the equalization scheme. In order to reduce the complexity of the system model, we utilize the autocorrelation and Doppler frequency to dynamically select the previous OFDM symbols that will be stored in the memory. In addition to deriving earlier results in a unified manner, the approach presented also leads to an enhanced performance results without imposing any restrictions or limitations on the OFDM system such as increasing the number of pilots or cyclic prefix.