scholarly journals Time Synchronization and Ranging in OFDM Systems Using Time-Reversal

2013 ◽  
Vol 62 (12) ◽  
pp. 3276-3290 ◽  
Author(s):  
Traian E. Abrudan ◽  
Azadeh Haghparast ◽  
Visa Koivunen
Keyword(s):  
Time Reversal ◽  
Time Synchronization ◽  
Ofdm Systems

OFDM Demodulation Using Virtual Time Reversal Processing in Underwater Acoustic Communications

2015 ◽  
Vol 23 (04) ◽  
pp. 1540011 ◽  
Author(s):  
Yanling Yin ◽  
Songzuo Liu ◽  
Gang Qiao ◽  
Yue Yang ◽  
Yue Yang
Keyword(s):  
Time Reversal ◽  
Orthogonal Frequency Division Multiplexing ◽  
Estimation Methods ◽  
Delay Spread ◽  
Underwater Acoustic Communications ◽  
Ofdm Systems ◽  
Acoustic Communications ◽  
Underwater Acoustic ◽  
Single Input Single Output ◽  
Virtual Time

The extremely long underwater channel delay spread causes severe inter-symbol interference (ISI) for underwater acoustic communications. Passive time reversal processing (PTRP) can effectively reduce the channel time dispersion in a simple way via convolving the received packet with a time reversed probe signal (PS). However, the PS itself may introduce extra noise and interference (self-correlation of the PS). In this paper, we propose a virtual time reversal processing (VTRP) for single input single output (SISO) orthogonal frequency division multiplexing (OFDM) systems. It convolves the received packet with the reversed estimated channel, instead of the PS to reduce the interference. Two sparse channel estimation methods, matching pursuit (MP), and basis pursuit denoising (BPDN), are adopted to estimate the channel impulse response (CIR). We compare the performance of VTRP with the PTRP and without any time reversal processing through MATLAB simulations and the pool experiments. The results reveal that VTRP has outstanding performance over time-invariant channels.

Time and Frequency Synchronization for MIMO-OFDM Systems

2013 ◽  
Vol 321-324 ◽  
pp. 2888-2891
Author(s):  
Jing Peng Gao ◽  
Chao Qun Wu ◽  
Dan Feng Zhao
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Carrier Frequency Offset ◽  
Time Synchronization ◽  
Multiple Input Multiple Output ◽  
Frequency Offset ◽  
Time Instant ◽  
Frequency Synchronization ◽  
Ofdm Systems ◽  
Frequency Offset Estimation ◽  
Mimo Ofdm

Any carrier frequency offset will cause a loss of subcarrier orthogonality which results in ICI and hence performance degrades severely in MIMO-OFDM systems. In this paper, a time and frequency synchronization solution for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems is proposed. The synchronization is achieved using one Constant Amplitude Zero Auto Correlation (CAZAC) sequence-based preamble which is simultaneously transmitted from all transmit antennas in the same OFDM time instant. The synchronization is accomplished sequentially by coarse time synchronization, fractional frequency offset estimation, integral frequency offset estimation and fine time synchronization. The simulation shows that the proposed algorithm can estimate the timing and frequency offsets efficiently in MIMO-OFDM systems, especially in low signal-to-noise ratio condition.

scholarly journals Pilot-Less Time Synchronization for OFDM Systems: Application to Power Line Receivers

2016 ◽  
Vol 12 (1) ◽  
pp. 8532941 ◽  
Author(s):  
Aris S. Lalos ◽  
Athanasios Vgenis ◽  
Fotios Gioulekas ◽  
Michael Birbas
Keyword(s):  
Time Synchronization ◽  
Power Line ◽  
Ofdm Systems

scholarly journals Comparison Study of Time Synchronization in NC-OFDM Systems Based on Symmetric Correlator

2019 ◽  
Vol 19 (2) ◽  
pp. 57
Author(s):  
Tajul Miftahushudur ◽  
Suyoto Suyoto
Keyword(s):  
Cognitive Radio ◽  
Time Synchronization ◽  
Mean Squared Error ◽  
Test Method ◽  
Multipath Channel ◽  
Ratio Test ◽  
Ofdm Systems ◽  
Cognitive Radio Systems ◽  
Radio Systems ◽  
Synchronization Performance

NC-OFDM as one of the candidates for the Cognitive Radio (CR) system has many challenges in the synchronizing time. This is due to the frequency sharing which can cause Narrowband Interference (NBI), which causes a very significant time synchronization error. Large errors in time synchronization can reduce overall NCOFDM system performance. In this study, we evaluate the time synchronization performance of NC-OFDM systems on the multipath channel in the present of NBI. We provide an evaluation of the time synchronization performance by comparing the time synchronization algorithm that has a timing metric such as an impulse-like (Symmetric correlator). Here, we present three algorithms that use the symbol training to calculate the arrival time of the NC-OFDM symbol. The simulation conducted by considering the effects of multipath channel, Signal to Noise Ratio (SNR), Carrier Frequency Offset (CFO), and SIR (Signal to Interference Ratio). SIR is modeled with NBI. Algorithm performance is measured by MAE (Mean Absolute Error) and MSE (Mean Squared Error). Simulation results show that the autocorrelation-based method has very poor performance in MAE and MSE tests, so it is not suitable for NC-OFDMbased Cognitive Radio systems. The GLRT (Generalized Likelihood Ratio Test) method and Iterative Normalization method perform well in case the NC-OFDM Cognitive Radio systems.

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