Temporal resolutions of time-reversal and passive-phase conjugation for underwater acoustic communications

Yang, T. C.

doi:10.1109/joe.2003.811895

Cited by 127 publications

(76 citation statements)

References 15 publications

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“…In general, communication BER increases as the side-lobe magnitude and the main-lobe width of the q-function increase [18,19]. The higher side lobes and wider main-lobe width augment the energy fraction of q-function positioning outside of one symbol duration and consequently create a significant ISI.…”

Section: Parameter E Qmentioning

confidence: 99%

“…Although the time reversal technique also employs an array of spatially separated receivers, it is relatively simple, effectively reduces the ISI in a multipath environment, and restores the original communication signal, thereby increasing the signal-to-noise ratio (SNR). Recently, passive time reversal processes have been widely used in underwater communication due to the simplicity of the system, in which an array is required only at the receiver [17][18][19]. Passive time reversal is related to the reciprocity of the active time reversal.…”

Section: Introductionmentioning

confidence: 99%

“…The performance of the time reversal can be characterized by the behavior of the q-function, which is the sum of the autocorrelation of each channel impulse response (CIR) for each receiver [18,19]. The passive time reversal y(t) is expressed by the equation below.…”

Section: Introductionmentioning

confidence: 99%

“…In general, the q-function depends on the complexity of the communication channel, the number of receivers in the array, and their spacing [19]. In an ideal case in which the estimated CIR has infinite bandwidth and no multipath, the q-function becomes a delta function, and the time reversal process recovers the exact original communication signal [14][15][16][17][18][19]. However, in a real ocean waveguide, the q-function is no longer the delta function, but has a main lobe and side lobes, producing a residual ISI of time compressed signal.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, if the residual ISI is not negligible even after the time reversal process, additional equalization processes, such as an adaptive decision feedback equalizer, are needed to eliminate the residual ISI. Such properties of the q-function affecting communication performance were investigated by Yang [18]. However, the parameter describing quantitatively the relation between the q-function and communication performance was not proposed in his work.…”

Section: Introductionmentioning

confidence: 99%

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Estimate of Passive Time Reversal Communication Performance in Shallow Water

et al. 2017

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Time reversal processes have been used to improve communication performance in the severe underwater communication environment characterized by significant multipath channels by reducing inter-symbol interference and increasing signal-to-noise ratio. In general, the performance of the time reversal is strongly related to the behavior of the q-function, which is estimated by a sum of the autocorrelation of the channel impulse response for each channel in the receiver array. The q-function depends on the complexity of the communication channel, the number of channel elements and their spacing. A q-function with a high side-lobe level and a main-lobe width wider than the symbol duration creates a residual ISI (inter-symbol interference), which makes communication difficult even after time reversal is applied. In this paper, we propose a new parameter, E q , to describe the performance of time reversal communication. E q is an estimate of how much of the q-function lies within one symbol duration. The values of E q were estimated using communication data acquired at two different sites: one in which the sound speed ratio of sediment to water was less than unity and one where the ratio was higher than unity. Finally, the parameter E q was compared to the bit error rate and the output signal-to-noise ratio obtained after the time reversal operation. The results show that these parameters are strongly correlated to the parameter E q .

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Section: Parameter E Qmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Estimate of Passive Time Reversal Communication Performance in Shallow Water

et al. 2017

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References

2014

OFDM for Underwater Acoustic Communications

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A novel time reversal sub-group imaging method with noise suppression for damage detection of plate-like structures

Gao

Zhang

et al. 2017

Struct Control Health Monit

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Summary In this paper, a new time reversal imaging (TRI) algorithm with noise suppression is developed for the application of imaged based structural damage detection of plate‐like structures. The conventional TRI method suffers from performance degradation in high noise condition. The proposed method addresses the aforementioned issues. First, an array of detection transducers is used and is divided into several subgroups. Then, the echo signals of the subgroups are time reversed and reemitted via numerical computation. Finally, the cross‐correlation functions of the summation of refocused time reversed signals in each subgroup are obtained to locate damages. The time reversed signals at the reference time are irrelevant to the noise, meanwhile, the multiple refocused signals in each subgroup are first added and then cross‐correlated. Therefore, the proposed method can effectively suppress noise. To validate the effectiveness of proposed method, 2 experiments were performed. The 2 experiments involved 2 aluminum plate specimens. Each specimen was equipped with 4 surface‐bonded lead zirconate titanate transducers. One specimen involved a simulated damage (an addition of a mass), and the other one involved an actual through‐hole damage. The experimental performances of the proposed method are compared to those of the conventional TRI method. The imaging results demonstrated that the damage on both specimens was clearly displayed with high spatial resolution by the proposed method even under the low signal‐to‐noise ratio condition. On the contrary, the location of the damage computed by the conventional TRI method was submerged in noise and cannot be distinguished.

show abstract

Temporal resolutions of time-reversal and passive-phase conjugation for underwater acoustic communications

Cited by 127 publications

References 15 publications

Estimate of Passive Time Reversal Communication Performance in Shallow Water

Estimate of Passive Time Reversal Communication Performance in Shallow Water

References

A novel time reversal sub-group imaging method with noise suppression for damage detection of plate-like structures

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