Abstract
Channel estimation and synchronization are considered the most challenging issues in Orthogonal Frequency Division Multiplexing (OFDM) system. OFDM is highly affected by synchronization errors that cause reduction in subcarriers orthogonality, leading to significant performance degradation. The synchronization errors cause two issues: Symbol Time Offset (STO), which produces inter symbol interference (ISI) and Carrier Frequency Offset (CFO), which results in inter carrier interference (ICI). The aim of the research is to simulate Comb type pilot based channel estimation for OFDM system showing the effect of pilot numbers on the channel estimation performance and propose a modified estimation method for STO with less number of pilot to mitigate ISI effect. Channel estimation is simulated for different pilot number with 16QAM modulation in Ped-A Rayleigh channel. The STO effect assumed less than the cyclic prefix length to minimize ISI and maintain the orthogonality between subcarriers. The simulation results show that the high number of pilots are needed to achieve good channel estimation in case no synchronization used while similar results are achieved with smaller number of pilots if the propose modification on the synchronization method are used aligned with the channel estimation. The proposed system is evaluated in terms of BER and SNR.
Highlights
For wireless systems, the transmitted signal is passed through the radio channel and it reached the receiver side after scattering in frequency and time domains because of the channel characteristics such as path loss, Intersymbol interference (ISI), multipath fading and doppler shift
The simulation results show that the high number of pilots are needed to achieve good channel estimation in case no synchronization used while similar results are achieved with smaller number of pilots if the propose modification on the synchronization method are used aligned with the channel estimation
SIMULATION RESULTS In this research, first LS and MMSE channel estimation techniques are applied to ITU-R Pedestrian-A Model (Ped-A) Rayleigh channel that described in (Cho et al, 2010)
Summary
The transmitted signal is passed through the radio channel and it reached the receiver side after scattering in frequency and time domains because of the channel characteristics such as path loss, Intersymbol interference (ISI), multipath fading and doppler shift. These characteristics are considered as critical challenges in the OFDM systems as the channel is changing rapidly depending on the environments (Nadar, Koti and Jayaswal, 2014). The STO effect represents a delay between the transmitted symbol to the received symbol, while the CFO represents a shift in the frequency domain of the subcarriers
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