Robust Preamble-Based Timing Synchronization for OFDM Systems

Liu, Yun; Ji, Fei; Yu, Hua; Wan, Dehuan; Chen, Fangjiong; Yang, Ling

doi:10.1155/2017/9319272

Cited by 4 publications

(6 citation statements)

References 16 publications

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“…Due to the inherent averaging over several subcarriers, Timothy M. Schmidl and Donald C. developed techniques for frequency shift estimation that operate close to the Cram'er-Rao minimum of variance [14].…”

Section: Related Workmentioning

confidence: 99%

“…We notice in the figure above that the signal sent from the satellite (the transmitter) to the vehicle (the receiver) passed two paths, the first is a direct path without any obstacle, and the second path collided with an obstacle which is the building, so the signal in the first path will arrive faster from the second with a lower attenuation rate, and then the signal from the second path arrives late, and therefore the received signal will be calculated by summing the signals through the two paths, taking into account the path gain and path delay [11,14], and as in the following equation: frequency selective fading will cause inter symbol interference, as the late version will overlap the adjacent symbols. As shown in the accompanying image, we will utilize a cyclic prefix to overcome this issue by lengthening the symbol period by duplicating the tail and adhering it to the front:…”

Section: Figure 5 -Multi-path Effectsmentioning

confidence: 99%

“…It is still feasible to retrieve the proper signal in the frequency domain by correcting for this rotation since the delay in the time domain that results from CP corresponds to the rotation in the frequency domain [12][13] [14].…”

Section: Figure 5 -Multi-path Effectsmentioning

confidence: 99%

“…DAC (at Tx) and ADC (at Rx) never have exactly the same sampling period, and this results in what is known as a "slow shift of the symbol timing point," which rotates the carriers. Subcarriers that induce inter-carrier interference (ICI), which results in the loss of the subcarriers' orthogonality, will interfere with those channels and lose their orthogonality, which is their most crucial characteristic [12] [14].…”

Section: Synchronization Problem In Ofdmmentioning

confidence: 99%

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A New Approach to Improve Transmitting and Receiving Timing in Orthogonal Frequency Division Multiplexing (OFDM) Systems

Abed

2023

ijcsm

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Nowadays, most wireless communications employ OFDM technology to reduce signal interference. Its sensitivity to timing faults, however, can cause a severe performance reduction. This study suggests a new approach to enhance communication systems' transmitting and receiving time. Although OFDM is a widely used modulation strategy in communication systems, it is vulnerable to timing faults, which can seriously affect performance. A frequency interference processing method is created that uses OFDM technology and goes through numerous steps, such as correcting CFO, adding a periodic prefix to prevent frequency distortion, calculating the time delay between transmission and reception, and spotting timing mistakes. It is clear that the lack of synchronization between the transmitter and channel interference has caused the Signal-to-Noise Ratio (SNR) to decline correspondingly. The initial approach had a piece of code that computed the transmission and reception times while recording their differences. As a result, it handles signal interference and frequency and temporal synchronization, two key aspects of OFDM. Timing precision varies from 0 to 1, and the time gap between transmission and reception is only a fraction of a second. When the SNR was available, timing errors and the lag between transmission and reception timing were seen, which suggests that there is a small probability of having too many locks or losing codes while utilizing OFDM. Simulation exercises show that the suggested method considerably enhances the system's Bit Error Rate (BER) performance in a variety of time offset conditions. The outcomes imply that the suggested strategy could be a workable remedy for OFDM systems with timing issues.

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Section: Related Workmentioning

confidence: 99%

Section: Figure 5 -Multi-path Effectsmentioning

confidence: 99%

Section: Figure 5 -Multi-path Effectsmentioning

confidence: 99%

Section: Synchronization Problem In Ofdmmentioning

confidence: 99%

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A New Approach to Improve Transmitting and Receiving Timing in Orthogonal Frequency Division Multiplexing (OFDM) Systems

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2023

ijcsm

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“…The time synchronization process at the receiver can be considered as the detection of the start of an OFDM package. The key to this stage is based on three fundamental concepts: auto-correlation, cross-correlation and metric [11], [12], [13], [21], [23], [26].…”

Section: Proposed Time Synchronization Techniquementioning

confidence: 99%

Time Synchronization Technique Hardware Implementation for OFDM Systems With Hermitian Symmetry for VLC Applications

2023

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The main contribution of this work is the proposal and hardware implementation of an algorithm for the time synchronization of orthogonal frequency division multiplexing (OFDM) modulation with Hermitian symmetry for visible light communications (VLC) systems, using only the real component of the transmitted signal. OFDM systems with Hermitian Symmetry are able to satisfy the high data rates demanded by many VLC systems, as well as deal with inter-symbol interference (ISI). However, these systems are characterized by being very vulnerable to synchronization problems in both time and frequency. Time synchronization being the most critical. In this paper, a novel time synchronization technique for OFDM systems with Hermitian Symmetry is proposed. This technique is based on the inclusion of a post-FFT synchronization stage to achieve time synchronization with one-sample precision. For this purpose, the relationship that exists between an offset in the frequency domain with an offset in the time domain is used, and with this information the correction of the frequency offset from the time domain is performed. An original and novel algorithm has been designed and implemented in hardware, which uses the cyclic prefix (CP) elimination stage to perform the time correction. The performance validation of the proposed technique is done with the implementation, using the ZYBO ™ development board, of a complete OFDM system applied to a real VLC system.INDEX TERMS Visible light communication (VLC), orthogonal frequency division multiplexing (OFDM), time synchronization, Hermitian symmetry.

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