【摘要】：相比于陸地上的無線電通信,水聲通信的通信速率還很低,由于聲波在水中傳播速率較低,水聲信道多徑效應嚴重,高速水聲通信面臨嚴重的碼間干擾。以正交頻分復用(Orthogonal Frequency Division Multiplexing,OFDM)為代表的多載波調制技術通過將數(shù)據(jù)調制到多路載波上并行發(fā)送,降低了碼元速率,能有效對抗多徑干擾�，F(xiàn)有的水聲OFDM調制系統(tǒng),對于IFFT得到的兩路數(shù)據(jù),大多數(shù)通過I-Q正交調制將兩路數(shù)據(jù)都發(fā)送傳輸,其系統(tǒng)的成本和復雜度都較高;少數(shù)采取頻域補零取實部發(fā)送的方法進行傳輸,但這會占用額外的子載波頻率,同時造成了發(fā)射功率的浪費。對此,本文對比研究現(xiàn)有的水聲OFDM調制方案,提出了通過頻域補零、補共軛再經IFFT處理后取實部發(fā)送的調制傳輸方案。同時,依據(jù)實際情況擬定了水聲OFDM通信系統(tǒng)的參數(shù),并完成了發(fā)射機的FPGA設計實現(xiàn)及片上驗證。為了在接收端精準定位OFDM符號的起始位置,研究了水聲OFDM通信過程中的同步技術,提出了通過混沌角調制序列相關檢測,來完成幀同步的方法,并設計生成了混沌角調制同步序列。為了能正確接收、恢復出發(fā)送數(shù)據(jù),研究了水聲OFDM通信的信道估計與補償技術,選擇了適合本文的塊狀導頻估計方案,并對LS、MMSE、LMMSE三種信道估計算法的估計效果進行仿真,最終選定用LMMSE來估計本文的信道頻率響應函數(shù),完成補償處理。最后,搭建了完整的水聲OFDM通信試驗系統(tǒng),進行了通信實驗,實驗結果表明,依據(jù)本文擬定調制傳輸方法及參數(shù),實現(xiàn)了水聲OFDM通信,傳輸距離為1.3m,頻譜效率為0.74bps/Hz,誤碼率為0.074,驗證了所提出的調制傳輸方案的有效性。
[Abstract]:Compared with the radio communication on land, the communication rate of underwater acoustic communication is still very low. Due to the low rate of acoustic wave propagation in the water, the multipath effect of underwater acoustic channel is serious, and the high-speed underwater acoustic communication faces serious inter-symbol interference. The multicarrier modulation technology, represented by orthogonal Frequency Division Multiplexing (Orthogonal Frequency Division Multiplexing,OFDM), reduces the symbol rate by modulating the data to the multi-channel carrier and can effectively resist the multipath interference. In the existing underwater acoustic OFDM modulation system, most of the two channels of data obtained by IFFT are transmitted through I-Q quadrature modulation, and the cost and complexity of the system are high. A few methods are used to transmit in frequency domain zero compensation and real part, but this will take up extra subcarrier frequency, and cause a waste of transmission power at the same time. In this paper, the existing underwater acoustic OFDM modulation schemes are compared and studied, and a modulation and transmission scheme is proposed, which is transmitted by adding zero in frequency domain, adding conjugate and then being processed by IFFT. At the same time, according to the actual situation, the parameters of underwater acoustic OFDM communication system are worked out, and the FPGA design and on-chip verification of the transmitter are completed. In order to accurately locate the starting position of OFDM symbols at the receiving end, the synchronization technology in underwater acoustic OFDM communication is studied, and a method to complete frame synchronization through correlation detection of chaotic angle modulation sequences is proposed. The chaotic angle modulation synchronization sequence is designed and generated. In order to receive and recover the transmitted data correctly, the channel estimation and compensation technology of underwater acoustic OFDM communication is studied, and the block pilot estimation scheme suitable for this paper is selected, and the estimation effect of the three channel estimation algorithms of LS,MMSE,LMMSE is simulated. Finally, LMMSE is selected to estimate the channel frequency response function to complete the compensation process. Finally, a complete underwater acoustic OFDM communication test system is built. The experimental results show that according to the modulation transmission method and parameters, the underwater acoustic OFDM communication is realized, and the transmission distance is 1.3 m. The spectral efficiency is 0.74 BP / Hz and the bit error rate is 0.074, which proves the effectiveness of the proposed modulation and transmission scheme.
【學位授予單位】：中北大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TN929.3

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