本文選題：擴(kuò)展譜 + CDMA�。� 參考：《浙江大學(xué)》2014年博士論文

【摘要】：本文瞄準(zhǔn)不確實(shí)信道下的有效、可靠通信,以信號(hào)處理、信息理論和傳播物理為支柱,在廣義似然比檢驗(yàn)(Generalized Likelihood Ratio Test, GLRT)框架下,進(jìn)行聯(lián)合的信道估計(jì)、均衡和符號(hào)檢測,以設(shè)計(jì)擴(kuò)展譜碼分多址(Code Division Multiple Address, CDMA)水下空時(shí)陣通信系統(tǒng)。 擴(kuò)展譜調(diào)制,在發(fā)射端,將待傳輸?shù)男畔⒂门c所傳輸?shù)男畔⑾嗒?dú)立的偽隨機(jī)碼擴(kuò)展成為寬帶信號(hào),即使信號(hào)所占用的帶寬遠(yuǎn)遠(yuǎn)超過所傳信息的必需帶寬；在接收端,使用完全相同的碼進(jìn)行同步相關(guān)／匹配接收以解擴(kuò),進(jìn)而恢復(fù)所傳送的信息。固有冗余偽隨機(jī)碼的引入不僅使發(fā)射信號(hào)為大時(shí)間帶寬乘積信號(hào),而且還讓發(fā)射信號(hào)呈現(xiàn)類噪聲性,以至于擴(kuò)展譜通信具有抗干擾、低截獲、高隱蔽等特性。在多用戶通信中,還可在每一發(fā)送信號(hào)中疊加不同的偽隨機(jī)碼來區(qū)分彼此,形成CDMA技術(shù)。 擴(kuò)展譜調(diào)制在實(shí)現(xiàn)形式上主要分為直接序列擴(kuò)展譜和跳頻擴(kuò)展譜兩種。直接序列擴(kuò)展譜利用偽隨機(jī)碼調(diào)制相移鍵控(Phase Shift Keying, PSK)信號(hào)進(jìn)行譜的擴(kuò)展；跳頻擴(kuò)展譜是在一個(gè)發(fā)射信號(hào)間隔內(nèi),按照偽隨機(jī)碼在一組預(yù)先規(guī)定的頻隙上隨機(jī)選擇一個(gè)或數(shù)個(gè)頻隙。與無擴(kuò)展調(diào)制方式相比,擴(kuò)展譜調(diào)制是以寬帶譜為代價(jià)來提高系統(tǒng)的可靠性的,利用CDMA技術(shù),盡管相對于單用戶擴(kuò)展譜通信而言,譜有效性／每碼片的總?cè)萘康玫搅颂岣?但采用隨機(jī)擴(kuò)展的CDMA技術(shù)相對于確定性擴(kuò)展的CDMA技術(shù)／無擴(kuò)展多用戶時(shí)的譜有效性仍存在損失。 水聲通信中,我們面臨的海洋波導(dǎo)環(huán)境,特別是淺海波導(dǎo)環(huán)境,由于其邊界及介質(zhì)起伏效應(yīng),造成時(shí)延和多普勒擴(kuò)展及其變化嚴(yán)重,致使經(jīng)海洋介質(zhì)傳播的聲信號(hào)呈現(xiàn)出時(shí)間和頻率選擇性衰落。其次,海洋信道還存在多用戶干擾、有意干擾及帶寬嚴(yán)重受限等問題。因此,要想實(shí)現(xiàn)遠(yuǎn)距離且有效可靠的水下通信必須采用空時(shí)陣通信。 時(shí)域模糊度函數(shù)在大時(shí)間帶寬乘積波形下低旁瓣,且波形“越亂越好”,時(shí)間上波形頻率無序?qū)で髸r(shí)延-多普勒集中。因此,本文在調(diào)制器端施加偽隨機(jī)碼以發(fā)射信號(hào),解調(diào)器端利用同步偽隨機(jī)碼解調(diào)接收信號(hào)。 利用空時(shí)對偶性,空域模糊度函數(shù)在大空間帶寬乘積陣形下低旁瓣,且陣形“越亂越好”,空間上陣幾何取向無序?qū)で箨図憫?yīng)向量集中。因此,本文收發(fā)端均采用“偽隨機(jī)”雙螺旋線陣(Double Spiral Line Array, DSLA)來作收發(fā)波束形成,以實(shí)現(xiàn)有效接收和有效照射。 借助于信號(hào)的幾何表征和信號(hào)空間分析,在發(fā)射信號(hào)先驗(yàn)等可能情況下,最小差錯(cuò)概率準(zhǔn)則導(dǎo)出的白高斯信道下的最佳符號(hào)檢測器為最大似然檢測器或最小距離檢測器,相應(yīng)的接收機(jī)為相關(guān)接收機(jī)及其等效的匹配濾波器。實(shí)際水聲通信中,反映信道傳播變化的測量模型中會(huì)存在未知參數(shù)如信道,因此,若采用先對未知參數(shù)作估計(jì),然后選擇最有可能的假設(shè),則構(gòu)成GLRT檢測器,其表現(xiàn)為：聯(lián)合的信道估計(jì)、均衡和符號(hào)檢測。為了跟蹤信道變化,應(yīng)采用自適應(yīng)均衡／濾波,如基于遞歸最小二乘(Recursive Least Square, RLS)的均衡／濾波。先驗(yàn)信息與數(shù)據(jù)信息具有相加性,在基于數(shù)據(jù)信息的基礎(chǔ)上,根據(jù)信道的空時(shí)演化特性構(gòu)建狀態(tài)-空間模型,然后在GLRT框架下,利用序貫貝葉斯濾波——卡爾曼／質(zhì)點(diǎn)濾波將先驗(yàn)信息規(guī)則化地嵌入到算法設(shè)計(jì)中,通過反饋,改善迭代過程的收斂,形成寬容性處理方法。 為了設(shè)計(jì)低復(fù)雜度擴(kuò)展譜CDMA序貫GLRT空時(shí)陣通信系統(tǒng),本文首先著重對空時(shí)匹配濾波／時(shí)反技術(shù)進(jìn)行了研究,提出了循環(huán)平穩(wěn)時(shí)反技術(shù)、時(shí)反-正交空時(shí)塊編碼技術(shù)和時(shí)反波束形成技術(shù)。鑒于被動(dòng)時(shí)反是時(shí)+空處理,本文又提出采用空時(shí)聯(lián)合的陣處理方法——空-時(shí)最小均方誤差(Minimum Mean Square Error, MMSE)來進(jìn)一步提高通信系統(tǒng)的可靠性。然后,本文將時(shí)反和空-時(shí)MMSE分別與卡爾曼／質(zhì)點(diǎn)濾波相結(jié)合設(shè)計(jì)了低復(fù)雜度的單載波／多載波擴(kuò)展譜CDMA水下空時(shí)陣通信系統(tǒng)。本文的研究內(nèi)容按三個(gè)部分展開。第一部分：水聲通信源-信道和空-時(shí)四維陣擴(kuò)展譜GLRT;第二部分：單載波擴(kuò)展譜通信GLRT;第三部分：多載波擴(kuò)展譜通信GLRT.在第二三部分又有層次地對兩個(gè)子內(nèi)容進(jìn)行研究：(1)時(shí)反擴(kuò)展譜通信GLRT;(2)空-時(shí)MMSE擴(kuò)展譜通信GLRT.最后,仿真和實(shí)驗(yàn)數(shù)據(jù)分別證實(shí)了上述研究內(nèi)容的可行性。
[Abstract]:This article aims at the effective and reliable communication under the uncertain channel, with signal processing, information theory and communication physics as the pillar, under the framework of Generalized Likelihood Ratio Test (GLRT), the joint channel estimation, equalization and symbol detection are used to design the extended spectrum code division multiple access (Code Division Multiple Address, CDMA). Underwater space-time array communication system.
Extended spectrum modulation, at the transmitter, the information to be transmitted is extended into a wideband signal with a pseudo random code independent of the transmitted information, even if the bandwidth occupied by the signal is far more than the required bandwidth of the transmitted information; at the receiving end, the same code is used to carry out the synchronization phase close / match reception to despread, and then restore the transmission. The introduction of inherent redundant pseudorandom code not only makes the transmitting signal a large time bandwidth product signal, but also makes the transmitting signal present noise like, so that the spread spectrum communication has the characteristics of anti-jamming, low interception and high concealment. In the multiuser communication, the different pseudo random codes can be superimposed on each sending signal to distinguish each other. CDMA technology is formed.
The spread spectrum modulation is divided into two kinds: direct sequence spread spectrum and frequency hopping spread spectrum. The direct sequence extension spectrum is extended by pseudo random code modulation phase shift keying (Phase Shift Keying, PSK). The frequency hopping spread spectrum is in a set of signal intervals, in a set of predetermined frequency gaps according to pseudorandom code There is a random selection of one or several frequency gaps. Compared with the non extended modulation, the extended spectrum modulation improves the reliability of the system at the cost of the broadband spectrum. Using the CDMA technology, the spectrum effectiveness / the total volume of each chip is improved compared to the single user extended spectrum communication, but the CDMA technique with random expansion is relative accurate. The spectral efficiency of the CDMA technology extended by nature is not lost.
In underwater acoustic communication, we face the marine waveguide environment, especially the shallow sea waveguide environment. Due to its boundary and medium fluctuation effect, the time delay and Doppler expansion and its change are serious. The acoustic signals transmitted through the ocean media show time and frequency selective fading. Secondly, there are multi user interference and intentional interference in the ocean channel. And the bandwidth is severely limited. Therefore, space time array communication must be used to achieve long distance and reliable underwater communication.
The time domain ambiguity function is low sidelobe in the large time bandwidth product waveform, and the waveform is "more chaotic, the better", and the time waveform frequency disorder seeks time delay - Doppler concentration. Therefore, this paper applies pseudo random code to transmit signal at the modulator end and demodulates the received signal using synchronous pseudorandom code.
By using space-time duality, the spatial ambiguity function is low sidelobe under the large space bandwidth product formation, and the formation is "more chaotic, the better", and the space array geometry orientation is disordered to seek the array response vector concentration. Therefore, the transceiver ends of this paper use "pseudo random" double spiral linear array (Double Spiral Line Array, DSLA) for sending and receiving beamforming. Effective reception and effective irradiation.
With the aid of geometric representation and signal spatial analysis of signals, the best symbol detector under the minimum error probability criterion derived from the minimum error probability criterion is the maximum likelihood detector or the minimum distance detector, and the corresponding receiver is the related receiver and the equivalent matching filter. In the letter, there will be unknown parameters such as channel in the measurement model that reflects the variation of channel propagation. Therefore, if the unknown parameter is estimated first and then the most probable hypothesis is selected, the GLRT detector is composed of the joint channel estimation, equalization and symbol detection. In order to track channel changes, adaptive equalization / filtering should be used. For example, equalization / filtering based on recursive least squares (Recursive Least Square, RLS). The priori information and data information are additive. Based on the data information, the state space model is constructed based on the spatial time evolution characteristics of the channel. Then the sequential Bayesian filtering, Calman / particle filter, will be used in the GLRT framework. The information is regularly embedded in the algorithm design, and the feedback process is adopted to improve the convergence of the iterative process and form a tolerance processing method.
In order to design a low complexity extended spectrum CDMA sequential GLRT space-time array communication system, this paper first focuses on the study of space-time matched filtering / time inverse technology, and proposes a cyclostationary time inverse technology, time inverse orthogonal space-time block coding and time inverse beamforming. The joint array processing method, Minimum Mean Square Error (MMSE), is used to further improve the reliability of the communication system. Then, a low complexity single carrier / multicarrier extended spectrum CDMA space time array communication system is designed by combining time and space time MMSE with Calman / particle filter, respectively. The research content of this paper is carried out in three parts. The first part: the underwater acoustic communication source channel and the space-time four-dimensional array extension spectrum GLRT; the second part: the single carrier spread spectrum communication GLRT; the third part: the multi carrier spread spectrum communication GLRT. studies the two sub content in the two or three part again: (1) the inverse spread spectrum communication GLRT; (2) empty. Time MMSE spread spectrum communication GLRT. finally, simulation and experimental data confirm the feasibility of the above research contents.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN929.3

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 張翔;水聲通信中多普勒頻移補(bǔ)償?shù)姆抡嫜芯縖J];系統(tǒng)仿真學(xué)報(bào);2005年05期

相關(guān)博士學(xué)位論文 前1條

1 夏夢璐;淺水起伏環(huán)境中模型—數(shù)據(jù)結(jié)合水聲信道均衡技術(shù)[D];浙江大學(xué);2012年

，

本文編號(hào)：1993843