【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(yīng)嚴(yán)重,高速水聲通信面臨嚴(yán)重的碼間干擾。以正交頻分復(fù)用(Orthogonal Frequency Division Multiplexing,OFDM)為代表的多載波調(diào)制技術(shù)通過將數(shù)據(jù)調(diào)制到多路載波上并行發(fā)送,降低了碼元速率,能有效對(duì)抗多徑干擾�，F(xiàn)有的水聲OFDM調(diào)制系統(tǒng),對(duì)于IFFT得到的兩路數(shù)據(jù),大多數(shù)通過I-Q正交調(diào)制將兩路數(shù)據(jù)都發(fā)送傳輸,其系統(tǒng)的成本和復(fù)雜度都較高;少數(shù)采取頻域補(bǔ)零取實(shí)部發(fā)送的方法進(jìn)行傳輸,但這會(huì)占用額外的子載波頻率,同時(shí)造成了發(fā)射功率的浪費(fèi)。對(duì)此,本文對(duì)比研究現(xiàn)有的水聲OFDM調(diào)制方案,提出了通過頻域補(bǔ)零、補(bǔ)共軛再經(jīng)IFFT處理后取實(shí)部發(fā)送的調(diào)制傳輸方案。同時(shí),依據(jù)實(shí)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(jī)的FPGA設(shè)計(jì)實(shí)現(xiàn)及片上驗(yàn)證。為了在接收端精準(zhǔn)定位OFDM符號(hào)的起始位置,研究了水聲OFDM通信過程中的同步技術(shù),提出了通過混沌角調(diào)制序列相關(guān)檢測,來完成幀同步的方法,并設(shè)計(jì)生成了混沌角調(diào)制同步序列。為了能正確接收、恢復(fù)出發(fā)送數(shù)據(jù),研究了水聲OFDM通信的信道估計(jì)與補(bǔ)償技術(shù),選擇了適合本文的塊狀導(dǎo)頻估計(jì)方案,并對(duì)LS、MMSE、LMMSE三種信道估計(jì)算法的估計(jì)效果進(jìn)行仿真,最終選定用LMMSE來估計(jì)本文的信道頻率響應(yīng)函數(shù),完成補(bǔ)償處理。最后,搭建了完整的水聲OFDM通信試驗(yàn)系統(tǒng),進(jìn)行了通信實(shí)驗(yàn),實(shí)驗(yàn)結(jié)果表明,依據(jù)本文擬定調(diào)制傳輸方法及參數(shù),實(shí)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(yàn)證了所提出的調(diào)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(xué)位授予單位】：中北大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN929.3

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