An OFDM System for Long-Range Underwater Acoustic Communications

2013 ◽  
Vol 321-324 ◽  
pp. 1274-1277 ◽  
Author(s):  
Xiao Lin Shi ◽  
Yi Xin Yang ◽  
Long Yang
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Data Stream ◽  
Underwater Acoustic Communications ◽  
Frequency Division ◽  
Ofdm System ◽  
Acoustic Communications ◽  
Underwater Acoustic ◽  
Frequency Domain Equalization ◽  
Convolutional Coding ◽  
Simulation Results

The Orthogonal Frequency Division Multiplexing (OFDM) technique is an effective method for suppressing multi-paths interference of underwater acoustic (UWA) channels. In this paper, a new communication system based on OFDM is presented, aiming at reliable 70km shallow water communications. The convolutional coding and frequency-domain equalization are also applied for the improvement of the OFDM system performance. The simulation results show that this proposed system can transmit data stream with low bit error rate (BER) in 70km UWA distance.

scholarly journals Downlink Power Allocation Strategy for Next-Generation Underwater Acoustic Communications Networks

Electronics ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 1297 ◽  
Author(s):  
Ahmad ◽  
Chang
Keyword(s):  
Power Allocation ◽  
Base Station ◽  
System Level ◽  
Underwater Acoustic Communications ◽  
Frequency Division ◽  
Next Generation ◽  
Acoustic Communications ◽  
Underwater Acoustic ◽  
Communications Networks ◽  
System Level Simulation

The increasing interest in next-generation underwater acoustic communications networks is due to vast investigation of oceans for oceanography, commercial operations in maritime areas, military surveillance, and more. A surface buoy or underwater base station controller (UBSC) communicates with either transceivers or underwater base stations (UBSs) via acoustic links. Transceivers further communicate with underwater sensor nodes using acoustic links. In this paper, we employ a downlink (DL) power allocation (PA) strategy using an orthogonal frequency-division multiple access (OFDMA) technique for underwater acoustic communications (UAC) networks. First, we present an approach to power offsets using three kinds of pilot spacing and apply the power boosting (PB) concept on orthogonal frequency-division multiplexing (OFDM) symbols for the UAC network. Secondly, we draw the block error rate (BLER) curves from link-level simulation (LLS) and analyze the signal-to-noise ratio (SNR) for both PA and non-PA strategies. Lastly, we adopt the best PB for system-level simulation (SLS) and compare the throughput and outage performance for PA and non-PA strategies. Hence, the simulation results confirm the effectiveness of the DL PA strategy for UAC networks.

scholarly journals A CCM-Based OFDM System with Low PAPR for Sparse Source

2018 ◽  
Vol 2018 ◽  
pp. 1-7
Author(s):  
Qinbiao Yang ◽  
Zulin Wang ◽  
Qin Huang
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Coded Modulation ◽  
High Peak ◽  
Frequency Division Multiplexing ◽  
Power Ratio ◽  
Frequency Division ◽  
Ofdm System ◽  
Simulation Results ◽  
Clipping And Filtering

Orthogonal frequency division multiplexing (OFDM) usually suffers high peak-to-average power ratio (PAPR). As shown in this paper, PAPR becomes even severe for sparse source due to many identical nonzero frequency OFDM symbols. Thus, this paper introduces compressive coded modulation (CCM) in order to restrain PAPR by reducing identical nonzero frequency symbols for sparse source. As a result, the proposed CCM-based OFDM system, together with iterative clipping and filtering, can efficiently restrain the high PAPR for sparse source. Simulation results show that it outperforms about 4 dB over the traditional OFDM system when source sparsity is 0.1.

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.

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