scholarly journals Pilot Based Channel Estimation and Synchronization in OFDM System

2020 ◽  
Vol 26 (6) ◽  
pp. 50-59
Author(s):  
Mahmood Mohmmmed saeed Abdul Majed ◽  
Buthaina Mosa Omran
Keyword(s):  
Channel Estimation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Carrier Frequency Offset ◽  
Estimation Method ◽  
Frequency Division ◽  
Ofdm System ◽  
Synchronization Errors ◽  
Rayleigh Channel ◽  
Significant Performance ◽  
Time Offset

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.

scholarly journals Pilot Sequence Assisted Channel Estimation in MIMO/SIMO/SISO-OFDM Systems

2020 ◽  
Author(s):  
Xiao Zhou ◽  
Chengyou Wang ◽  
Qun Wu
Keyword(s):  
Channel Estimation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Estimation Method ◽  
High Order ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Ofdm System ◽  
Input Multiple Output ◽  
Mimo Ofdm ◽  
Single Input

Abstract For improving the communication system performance in multiple input multiple output- orthogonal frequency division multiplexing (MIMO-OFDM) system, single input multiple output-orthogonal frequency division multiplexing (SIMO-OFDM) system, single input single output-orthogonal frequency division multiplexing (SISO-OFDM) system, this paper introduces a pilot assisted channel estimation method. The proposed method is a combination of pilots and channel estimation based on known channel state information (CSI). First, the pilots are used to maintain the orthogonality characteristics of space time block coding (STBC). By designing the interference-free pilots we estimating the channel, and then with the pre-estimated channel characteristics data is decoded at the MIMO-OFDM system receiver. In this paper, we proposed four kinds of comb-type pilot sequences with interference-free pilots designing among consecutive subcarriers. The proposed pilot assisted channel estimation method in MIMO/SIMO/SISO-OFDM systems could be well adopted with different low and high order modulations. This flexible transmission mechanism can save pilot overhead and has strong anti-interference ability in dynamic channels. Moreover, high-order constellation modulation level will enhance the channel capacity in MIMO/SIMO/SISO-OFDM system. Therefore, it can be used as a candidate technology for 5G or 6G MIMO/SIMO/SISO-OFDM system.

scholarly journals Channel estimation of OFDM in C-band communication systems under different distribution conditions

2021 ◽  
Vol 23 (3) ◽  
pp. 1778
Author(s):  
Heba Abdul-Jaleel Al-Asady ◽  
Hassan Falah Fakhruldeen ◽  
Mustafa Qahtan Alsudani
Keyword(s):  
Fourier Transform ◽  
Channel Estimation ◽  
Fast Fourier Transform ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Ofdm System ◽  
High Data ◽  
High Efficient

<p>Orthogonal frequency division multiplexing (OFDM) is a transmission system that uses multiple orthogonal carriers that are sent out at the same time. OFDM is a technique for mobile and wireless communication that has high-efficient frequency utilization, high data-rate transmission, simple and efficient implementation using the fast Fourier transform (FFT) and the inverse fast Fourier transform (IFFT), and reduces inter symbol interference (ISI) by inserting cyclic prefix (CP). One of the most important approaches in an OFDM system is channel estimation. In this paper, the orthogonal frequency division multiplexing system with the Rayleigh channel module is analyzed for different areas. The proposed approach used large numbers of subcarriers to transmit the signals over 64-QAM modulation with pilot add channel estimation. The accuracy of the OFDM system is shown in the measuring of the relationships of peak power to the noise ratio and bit error rate.</p>

scholarly journals Carrier Frequency Offset Effects on OFDM System over Rayleigh Fading Channel

2020 ◽  
Vol 3 (2) ◽  
pp. 45
Author(s):  
N. M. A. E. Dewi Wirastuti ◽  
I.G.A.K. Diafari Djuni Hartawan ◽  
I Made Arsa Suyadnya ◽  
Duman Care Khrisne
Keyword(s):  
Fourier Transform ◽  
Fading Channel ◽  
Orthogonal Frequency Division Multiplexing ◽  
Rayleigh Fading ◽  
Carrier Frequency Offset ◽  
Rayleigh Fading Channel ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Ofdm System ◽  
Modulation And Demodulation

Orthogonal Frequency Division Multiplexing (OFDM) system showed the use of Discrete Fourier Transform (DFT) and Inverse Discrete Fourier Transform (IDFT) to perform the baseband modulation and demodulation. So that, it can increase and improve the efficiency of the modulation and demodulation. Currently, the OFDM is being utilized in the field of broadband wireless communication, which transmit signals orthogonally, that increases speed of information transmission. It also has high proficiency with high bandwidth and provide large data rates and robust against the multipath delay spread. On the other hand, there are some issues faced OFDM system which are high Peak Average Power Ratio (PAPR), and sensitive to Phase Noise (PN) and Carrier Frequency Offset (CFO). This paper presents Orthogonal Frequency Division Multiplexing (OFDM) performance evaluation in the presence of CFO with two different environment scenarios were used: an AWGN channel and a Rayleigh fading channel. The simulation was performed to evaluate the effects of CFO based on Bit Error Rate (BER) vs. Energy Bit per Noise Ratio (Eb/No). The results showed that for BER degradation caused by CFO effects have presented in our simulation for both AWGN and Rayleigh fading channel.

scholarly journals Comparison of SPS and FA methods for Blind Carrier Frequency Offset Estimation in OFDM systems

2022 ◽  
Vol 16 ◽  
pp. 7-11
Author(s):  
K. Seshadri Sastry ◽  
K. Baburao ◽  
A.V. Prabu ◽  
G.Naveen Kumar
Keyword(s):  
Carrier Frequency ◽  
Orthogonal Frequency Division Multiplexing ◽  
Carrier Frequency Offset ◽  
Frequency Offset ◽  
Intercarrier Interference ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Frequency Offset Estimation ◽  
Synchronization Errors ◽  
Carrier Frequency Offset Estimation

In orthogonal frequency-division multiplexing (OFDM) systems, synchronization issues are of great importance since synchronization errors might destroy the orthogonality among all subcarriers and, therefore, introduce intercarrier interference (ICI) and intersymbol interference (ISI). Several schemes of frequency offset estimation in OFDM systems have been investigated. This paper compares performance and computational complexity of Smoothing Power Spectrum (SPS) and Frequency Analysis (FA) methods for blind carrier frequency offset (CFO) estimation in OFDM systems.

Multiple-Input-Single-Output Based a Novel Pilot-Aided Channel Estimation for Cyclic Delay Diversity Orthogonal Frequency Division Multiplexing Frameworks

2019 ◽  
Vol 16 (2) ◽  
pp. 697-701
Author(s):  
D. Jagadeesan ◽  
K. Palani ◽  
G. Asha
Keyword(s):  
Channel Estimation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Low Complexity ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Cyclic Delay Diversity ◽  
Single Output ◽  
Estimation Scheme ◽  
Significant Performance ◽  
Delay Diversity

A low-complexity standard transmit diversity scheme for coded orthogonal frequency division multiplexing (OFDM) frameworks is cyclic delay diversity (CDD). As the cyclic delay esteem expands the diversity effect also increases. However, the channel estimation turns out to be more troublesome because of increased frequency selectivity as the increased cyclic delay value. In this paper we discussed about dissimilar channel estimation schemes and to conclude we proposed a novel pilot-aided channel estimation scheme for CDD to estimate the channel in an enhanced way. Our scheme estimates each channel separately and achieves significant performance improvement.

The Study of Interpolation Algorithms in OFDM Systems

2013 ◽  
Vol 321-324 ◽  
pp. 2837-2840
Author(s):  
Xi Jun Zhang ◽  
Jian Bin Xue ◽  
Ying Lin ◽  
Ji Ai He
Keyword(s):  
Channel Estimation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Ofdm System ◽  
Simulation Process ◽  
Interpolation Algorithms ◽  
Simulation Results

Orthogonal frequency division multiplexing (OFDM) is a kind of highly transmission technology. It has been taken more and more attention in many ways. In this paper it mainly discussed the simulation process and several interpolation algorithms in OFDM system. Using computer we simulate the interpolation algorithms in OFDM channel estimation. Through the simulation results we compare the advantage and disadvantage of the interpolation algorithms. At last we can use the conclusion to choose the correct interpolation algorithms in OFDM channel estimation.

scholarly journals Improved Interference Cancelation Channel Estimation Method in OFDM/OQAM System

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Shangfei Qiu ◽  
Lunsheng Xue ◽  
Peng Wu
Keyword(s):  
Channel Estimation ◽  
Spectral Efficiency ◽  
Orthogonal Frequency Division Multiplexing ◽  
Estimation Method ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Estimation Performance ◽  
Interference Cancelation ◽  
Simulation Results ◽  
Method Show

To the significant amount of pilot overhead of the interference cancelation methods in orthogonal frequency division multiplexing (OFDM) based on offset quadrature amplitude modulation (OFDM/OQAM) system, we proposed an improved interference cancelation method (ICM) for OFDM/OQAM system in this paper. In this method, we use the auxiliary pilot (AP) to eliminate the influence of the intersymbol interference on channel estimation, which can reduce the pilot overhead of OFDM/OQAM system significantly. At the same time, to improve the channel estimation performance, we analyze the source of the intrinsic interference of system and its distribution in time and frequency domain, then, we reset the interference cancelation range of AP, which can cancel more intrinsic interference for OFDM/OQAM system. According to the results of performance analysis, compared to the conventional interference cancelation methods, the proposed method performs better in terms of energy efficiency and spectral efficiency. Also, the simulation results of the proposed method show that the proposed method can outperform traditional interference cancelation methods in channel estimation performance.

scholarly journals An Algorithm Combining Synchronization and Channel Estimation for OFDM Systems

2009 ◽  
Author(s):  
Pham Hong Lien ◽  
Nguyen Duy Lai
Keyword(s):  
Channel Estimation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Carrier Frequency Offset ◽  
Multipath Fading ◽  
Frequency Offset ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Clock Frequency ◽  
Close Relationship ◽  
Ofdm Signals

OFDM (Orthogonal Frequency Division Multiplexing) is more and more popular in applications of digital communications because of the effective spectrum and less impacts  of multipath fading. However, beside these advantages, OFDM signals are destroyed easily by errors such as CFO (Carrier Frequency Offset), SFO (Sampling Clock Frequency Offset). Thus, it’s necessaryto have robustly offset algorithms to overcome these disadvantages. Studies about OFDM we just examined channel estimation with assumptions that synchronization is perfect, and vice versa. However, they have a close relationship, channel estimation can be restricted if synchronization is bad, and vice versa. This paper presents an algorithm combining synchronization and channel estimation in OFDM systems. The algorithm is compared with other proposed algorithms by simulation. The simulation result of the algorithm combining synchronization and channel estimation is close to that of ideal conditions: perfect channel estimation and synchronization.

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