OFDM systems are sensitive to front-end imperfections including CFO, IQ imbalance and phase noise. In practice, these imperfections are inevitable and would lead to significant performance degradation. In this paper, ...
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OFDM systems are sensitive to front-end imperfections including CFO, IQ imbalance and phase noise. In practice, these imperfections are inevitable and would lead to significant performance degradation. In this paper, a general closed-form expression on average signal-to-interference-and-noise ratio (SINR) over multipath fading channels is derived for performance evaluation. When additive white Gaussian noise channels and flat fading channels are considered, the expression reduces to an exact expression and a tight upper bound, respectively. Our results show that the average SINR is inversely proportional to these front-end non-idealities.
We propose a three-stage cross correlation-based timing synchronization algorithm for multiband-OFDM UWB systems. By utilizing the time-domain base sequence of the packet/frame synchronization preamble, the proposed a...
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We propose a three-stage cross correlation-based timing synchronization algorithm for multiband-OFDM UWB systems. By utilizing the time-domain base sequence of the packet/frame synchronization preamble, the proposed algorithm first performs a coarse estimation on the reference symbol boundary, followed by a fine estimation on locating the exact boundary of the FFT window for the symbol, and a final check if the exact boundary is within an intersymbol interference-free zone. Numerical results reveal the effectiveness of the proposed algorithm in terms of mean square error and synchronization probability with respect to prior works.
Drillstring acoustic telemetry is an effective transmission method to retrieve downhole data. In this paper, finite-difference algorithm is used for acoustic wave propagation prediction along the drillstring. An impul...
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ISBN:
(纸本)9781457721182
Drillstring acoustic telemetry is an effective transmission method to retrieve downhole data. In this paper, finite-difference algorithm is used for acoustic wave propagation prediction along the drillstring. An impulse excitation signal of time duration 30.87 μs is transmitted from the downhole and the wave displacement at the receiver is found using finite-difference algorithm. The resultant impulse and frequency responses are plotted and compared for different segments. It is found that the selection and arrangement of downhole pipes plays a vital role in improving the transmission efficiency of extensional waves transmitted through the drillstring for acoustic telemetry, particularly in the high-frequency bands. In order to find the optimal pipe arrangement order, 4 segments of drillstring with lengths d_(11) to d_(14) (in increasing length between 9.3434 m and 9.8185 m) are arranged in all 24 possible permutations. The energy of the frequency response is found for each of the six pass bands for the twenty four arrangements. It is concluded from the findings that placing the shortest pipe at the downhole first, followed by the longest pipe, then the next longest pipe and so on, produces the best possible telemetry performance in terms of optimal acoustic energy transfer.
In this paper, a novel time-of-arrival estimation algorithm is proposed for impulse radio-based UWB systems in dense multipath environment. In particular, a dedicated ranging sequence with good cross-correlation prope...
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In this paper, a novel time-of-arrival estimation algorithm is proposed for impulse radio-based UWB systems in dense multipath environment. In particular, a dedicated ranging sequence with good cross-correlation property is proposed and a threshold-based search-back unit is introduced, with the purpose of supporting high-precision ranging even at low signal-to-noise ratio. An approximate closed-form expression on the optimal threshold is derived based on the Rayleigh statistical analysis, and its accuracy and tightness are verified by simulations. Results show that the proposed ranging scheme achieves an excellent mean absolute error performance in the order of nanoseconds without introducing too much latency.
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