PN sequence based Doppler and channel estimation for underwater acoustic OFDM communication

Liu, Lanjun; Zhang, Yonglei; Zhang, Pengcheng; Zhou, Lin; Li, Jianfen; Jin, Jiucai; Zhang, Jie; Lv, Zhichao

doi:10.1109/icspcc.2016.7753719

“…A PN sequence based Doppler estimation method is proposed by Liu et al 29 The orthogonality of the PN sequence is used for the estimation of Doppler shift by delay cross–correlation method. The authors have proved through simulations that the method is two orders of magnitude better at estimating Doppler spread compared to LFM signals.…”

Section: Doppler Estimationmentioning

confidence: 99%

Synchronization techniques for underwater acoustic communications

Babu

¹

,

Ameer

²

,

Koilpillai

³

2023

Int J Communication

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SummaryUnderwater acoustic channel is a challenging medium for communication due to the presence of significant multipath, high noise, frequency‐dependent propagation loss, and high and non‐uniform Doppler spread. Doppler shift is non‐negligible in underwater communication due to the low velocity of underwater signals. Synchronization and Doppler estimation are important requirements for achieving good performance in this channel. Synchronization algorithms that give good performance in radio communication do not work well in underwater communication. Hence, this area has received a lot of attention from researchers. This paper surveys important works in the area. The techniques proposed in the literature for frame synchronization, frequency and phase synchronization, and timing synchronization in single carrier communications are reviewed here. The synchronization techniques proposed for OFDM, MIMO OFDM, and spread spectrum communication are also surveyed. Doppler estimation methods proposed in the literature are also reviewed. It is found that most of the recent works in underwater acoustic communication focus on OFDM synchronization. Deep learning‐based methods proposed in the literature are also reviewed. Key open problems and areas that require future research attention in the field of synchronization and Doppler estimation in underwater communications are highlighted in this paper. The area needing most attention of underwater communication researchers was found to be MIMO OFDM due to the difficulty in synchronization in such systems while used in underwater communication. Reducing the computational complexity of the algorithms used is also important for future work. Schemes that work with Doppler due to relative velocity over 10 m/s also need to be developed.

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“…where, T is the duration of prefix signal and Tg is the guard interval. On substituting (19) in (20), we get:…”

Section: Correlation Based Detectormentioning

confidence: 99%

A Prefix Based Approach for Joint Doppler and Channel Estimation in Underwater Communication

Bhadouria

¹

,

Agrawal

²

,

Kumar

³

2022

Preprint

0

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Developing a reliable and robust underwater acoustic communication system is a difficult task, due to the complicated nature of the underwater channel, non-stationary noise, and a number of other factors. Indeed, channel estimation or equalization presents numerous challenges in this non-stationary, highly Doppler, multipath environment; as a result, traditional equalizers and PLL-based methods have limited performance. Generally, communication over such time-varying channels is accomplished via packets that contain a prefix/preamble signal for training, a payload containing the actual data, and a silent period for proper alignment. The prefix signal must be designed properly because it is used to estimate the channel and also to determine the start of packet. This paper proposes a novel prefix signal based on the hyperbolic chirp signal, where its Doppler invariance properties enable the extraction of the entire packet even when Doppler and severe multipath are present. Additionally, this proposed prefix enables an efficient and accurate method for fully characterising an underwater channel. The proposed prefix signal is used to estimate the multipath delay and amplitude, and different Doppler scales. Extensive simulations using various channel models are used to determine the proposed method robustness and efficacy under a wide range of conditions. Additionally, the proposed algorithm has been validated on a real-world channel.

show abstract

“…where, T is the duration of prefix signal and T g is the guard interval. On substituting (19) in (20), we get:…”

Section: Correlation Based Detectormentioning

confidence: 99%

A Prefix Based Approach for Joint Doppler and Channel Estimation in Underwater Communication

Bhadouria

¹

,

Agrawal

²

,

Kumar

³

2021

Preprint

1

0

View full text Add to dashboard Cite

Developing a reliable and robust underwater acoustic communication system is a difficult task, due to the complicated nature of the underwater channel, non-stationary noise, and a number of other factors. Indeed, channel estimation or equalization presents numerous challenges in this non-stationary, highly Doppler, multipath environment; as a result, traditional equalizers and PLL-based methods have limited performance. Generally, communication over such time-varying channels is accomplished via packets that contain a prefix/preamble signal for training, a payload containing the actual data, and a silent period for proper alignment. The prefix signal must be designed properly because it is used to estimate the channel and also to determine the start of packet. This paper proposes a novel prefix signal based on the hyperbolic chirp signal, where its Doppler invariance properties enable the extraction of the entire packet even when Doppler and severe multipath are present. Additionally, this proposed prefix enables an efficient and accurate method for fully characterising an underwater channel. The proposed prefix signal is used to estimate the multipath delay and amplitude, and different Doppler scales. Extensive simulations using various channel models are used to determine the proposed method robustness and efficacy under a wide range of conditions. Additionally, the proposed algorithm has been validated on a real-world channel.

show abstract

PN sequence based Doppler and channel estimation for underwater acoustic OFDM communication

Cited by 15 publications

References 7 publications

Synchronization techniques for underwater acoustic communications

Synchronization techniques for underwater acoustic communications

A Prefix Based Approach for Joint Doppler and Channel Estimation in Underwater Communication

A Prefix Based Approach for Joint Doppler and Channel Estimation in Underwater Communication

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