CN102546511A - Underwater sound communication device and method based on time reversal and orthogonal frequency division multiplexing (OFDM) combined treatment - Google Patents
Underwater sound communication device and method based on time reversal and orthogonal frequency division multiplexing (OFDM) combined treatment Download PDFInfo
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Abstract
本发明公开了一种基于时反和OFDM联合处理的水声通信装置包括信号发射机、功率放大器、发射换能器、接收水听器阵、信号接收机和信号处理器,其中,信号处理器包括宽带多普勒估计与补偿模块、时反处理模块、OFDM解调模块、信道估计与补偿模块和频偏估计与补偿模块。本发明利用时反的空时聚焦特性,来消除信道的多径影响,时反可以缩短脉冲信道响应长度,从而减少OFDM符号保护间隔的长度,提高了通信效率;由于减少了保护间隔,OFDM符号长度也可以缩短,这样增大了子载波频率间隔。本发明方法可以减少子载波间干扰,进一步提升OFDM水声通信的可用速率。
The invention discloses an underwater acoustic communication device based on joint processing of time inversion and OFDM, which includes a signal transmitter, a power amplifier, a transmitting transducer, a receiving hydrophone array, a signal receiver and a signal processor, wherein the signal processor It includes a wideband Doppler estimation and compensation module, a time inversion processing module, an OFDM demodulation module, a channel estimation and compensation module and a frequency offset estimation and compensation module. The present invention utilizes the space-time focusing characteristic of time inversion to eliminate the multipath influence of the channel, and time inverse can shorten the pulse channel response length, thereby reducing the length of the OFDM symbol guard interval and improving communication efficiency; due to the reduced guard interval, the OFDM symbol The length can also be shortened, which increases the subcarrier frequency spacing. The method of the invention can reduce the interference between sub-carriers, and further improve the available rate of OFDM underwater acoustic communication.
Description
技术领域 technical field
本发明涉及一种时反以及OFDM的水声通信装置及方法,属于水声通信技术领域。The invention relates to a time-reverse and OFDM underwater acoustic communication device and method, belonging to the technical field of underwater acoustic communication.
背景技术 Background technique
从上世纪90年代中后期开始,就有人逐步将正交频分利用(OrthogonalFrequency Division Multiplexing,简称“OFDM”)技术应用于水声通信中,由于OFDM技术频谱利用率高,通信速率快,发射和接收硬件实现简单,现在OFDM通信已成为水声通信领域研究的热点。为了实现可靠通信,OFDM的保护间隔长度要求大于信道最大时延扩展长度,而水声信道的时延扩展较严重,因此降低了OFDM水声通信的效率。现有的办法是提升OFDM符号的长度,这虽然提升了通信效率,但是也减少了OFDM符号的子载波频率间隔,在动态的水声信道中,增加了子载波间干扰(inter-carrier interference,简称“ICI”),降低了通信可靠性。Since the mid-to-late 1990s, some people have gradually applied Orthogonal Frequency Division Multiplexing ("OFDM") technology to underwater acoustic communications. The receiving hardware is simple to implement, and now OFDM communication has become a research hotspot in the field of underwater acoustic communication. In order to achieve reliable communication, the guard interval length of OFDM needs to be greater than the maximum channel delay extension length, and the delay extension of underwater acoustic channel is serious, thus reducing the efficiency of OFDM underwater acoustic communication. The existing method is to increase the length of the OFDM symbol. Although this improves the communication efficiency, it also reduces the subcarrier frequency interval of the OFDM symbol. In the dynamic underwater acoustic channel, the inter-carrier interference (inter-carrier interference, referred to as "ICI"), reducing communication reliability.
发明内容 Contents of the invention
本发明的目的是克服现有技术中OFDM水声通信保护间隔较长、子载波间干扰较大的缺陷,提供一种基于时反和OFDM联合处理的水声通信装置及方法。The purpose of the present invention is to overcome the disadvantages of long OFDM underwater acoustic communication protection interval and relatively large interference between subcarriers in the prior art, and provide an underwater acoustic communication device and method based on joint processing of time inversion and OFDM.
为实现上述目的,本发明所采取的技术方案是:For realizing above-mentioned purpose, the technical scheme that the present invention takes is:
本发明基于时反和OFDM联合处理的水声通信装置包括:The underwater acoustic communication device based on time-reversal and OFDM joint processing of the present invention includes:
信号发射机,用于形成通信信号,所述通信信号包括线性调频信号和OFDM信号,且在线性调频信号和OFDM信号之间插入有保护间隔,所述OFDM信号是通过将外部通信数据插入导频数据后经OFDM调制而成;a signal transmitter for forming a communication signal including a chirp signal and an OFDM signal with a guard interval inserted between the chirp signal and the OFDM signal, the OFDM signal being formed by inserting external communication data into a pilot After the data is modulated by OFDM;
功率放大器,用于将所述通信信号进行功率放大;a power amplifier, configured to amplify the power of the communication signal;
发射换能器,用于将放大后的通信信号转化为声信号,并将声信号发射至水中;a transmitting transducer for converting the amplified communication signal into an acoustic signal and transmitting the acoustic signal into the water;
接收水听器阵,用于接收发射换能器发射至水中的声信号,并将所述声信号转换为电信号;The receiving hydrophone array is used to receive the acoustic signal emitted by the transmitting transducer into the water, and convert the acoustic signal into an electrical signal;
信号接收机,用于将所述电信号转换为数字信号并存储;a signal receiver for converting said electrical signal into a digital signal and storing it;
信号处理器,该信号处理器包括:A signal processor, the signal processor includes:
——宽带多普勒估计与补偿模块,用于对信号接收机存储的数字信号进行多普勒因子的估计和宽带多普勒补偿;——Wideband Doppler estimation and compensation module, used for Doppler factor estimation and wideband Doppler compensation for the digital signal stored in the signal receiver;
——时反处理模块,用于对经过宽带多普勒补偿后的信号进行被动时反处理;——Time inversion processing module, used for passive time inversion processing on the signal after broadband Doppler compensation;
——OFDM解调模块,用于对经过被动时反处理的信号进行OFDM解调;——OFDM demodulation module, which is used to perform OFDM demodulation on the passively processed signal;
——信道估计与补偿模块,用于利用OFDM解调后的信号和采用最小二乘信道估计方法估计出水声信道的响应,以及消除水声信道对OFDM解调后的信号的影响;——The channel estimation and compensation module is used to estimate the response of the underwater acoustic channel by using the signal after OFDM demodulation and the least squares channel estimation method, and eliminate the influence of the underwater acoustic channel on the signal after OFDM demodulation;
——频偏估计与补偿模块,用于对经过信道估计与补偿模块处理后的信号进行频偏估计和补偿。——The frequency offset estimation and compensation module is used for estimating and compensating the frequency offset of the signal processed by the channel estimation and compensation module.
本发明利用以上装置进行时反和OFDM联合处理的水声通信方法包括如下步骤:The present invention utilizes the above device to carry out the underwater acoustic communication method of time-reversal and OFDM joint processing comprising the following steps:
1)信号发射机产生线性调频信号l(i),并在外部通信数据中插入导频数据而得到插有导频数据的通信数据x(k),将插有导频数据的通信数据x(k)经OFDM调制成第一OFDM信号s(j),然后在线性调频信号l(i)和OFDM信号s(j)之间插入保护间隔形成通信信号;其中i=1,2,…,I,I为线性调频信号的长度;k=1,2,…,K,K为插有导频数据的通信数据x(k)的长度;j=1,2,…,J,J为OFDM信号s(j)的长度,I、K、J均为大于1的正整数;1) The signal transmitter generates the chirp signal l(i), and inserts the pilot data into the external communication data to obtain the communication data x(k) with the pilot data inserted, and the communication data x(k) with the pilot data inserted k) The first OFDM signal s(j) is modulated by OFDM, and then a guard interval is inserted between the chirp signal l(i) and the OFDM signal s(j) to form a communication signal; wherein i=1, 2, ..., I , I is the length of the chirp signal; k=1, 2, ..., K, K is the length of the communication data x (k) inserted with the pilot data; j=1, 2, ..., J, J is the OFDM signal The length of s(j), I, K, J are all positive integers greater than 1;
2)所述通信信号经过功率放大器放大后发送到放置于水中的发射换能器;2) The communication signal is sent to the transmitting transducer placed in the water after being amplified by the power amplifier;
3)发射换能器将放大后的通信信号转化为声信号并发射至水中;3) The transmitting transducer converts the amplified communication signal into an acoustic signal and transmits it into the water;
4)利用放置于水中的接收水听器阵接收发射换能器发射至水中的声信号,并将所述声信号转换为电信号;4) Utilize the receiving hydrophone array placed in the water to receive the acoustic signal emitted by the transmitting transducer into the water, and convert the acoustic signal into an electrical signal;
5)信号接收机将接收水听器阵所转换的电信号转换为数字信号Y(n)并进行存储;5) The signal receiver converts the electrical signal converted by the receiving hydrophone array into a digital signal Y(n) and stores it;
6)信号处理器中的宽带多普勒估计与补偿模块先对所述数字信号Y(n)与线性调频信号l(i)进行相关运算,然后利用所述相关运算的结果估计出数字信号Y(n)中的所有相邻的两个线性调频信号之间的间隔时间T2,得到如式(1-1)所示的那多普勒因子α和式(1-2)所示的插值因子D:6) The wideband Doppler estimation and compensation module in the signal processor first performs a correlation operation on the digital signal Y(n) and the chirp signal l(i), and then uses the result of the correlation operation to estimate the digital signal Y The interval time T 2 between all adjacent two chirp signals in (n), get that Doppler factor α shown in formula (1-1) and the interpolation shown in formula (1-2) Factor D:
α=1-T2/T1 (1-1)α=1-T 2 /T 1 (1-1)
D=1+α (1-2)D=1+α (1-2)
式(1-1)中,T1表示信号发射机产生的两个相邻的线性调频信号的间隔时间;In formula (1-1), T represents the time interval between two adjacent chirp signals produced by the signal transmitter;
然后,利用所述插值因子D对所述数字信号Y(n)进行插值得到补偿后的信号Y1(n);Then, using the interpolation factor D to interpolate the digital signal Y(n) to obtain a compensated signal Y 1 (n);
7)信号处理器中的时反处理模块利用线性调频信号l(i)作为探测源,对所述补偿后的信号Y1(n)在频域上进行被动时反处理得到第二OFDM信号s1(j);7) The time-reversal processing module in the signal processor uses the chirp signal l(i) as a detection source, and performs passive time-reverse processing on the compensated signal Y 1 (n) in the frequency domain to obtain the second OFDM signal s 1 (j);
8)信号处理器中的OFDM解调模块对所述第二OFDM信号s1(j)进行解调,得到解调后的通信数据x1(k);8) The OFDM demodulation module in the signal processor demodulates the second OFDM signal s 1 (j) to obtain demodulated communication data x 1 (k);
9)信号处理器中的信道估计与补偿模块利用所述插有导频数据的通信数据x(k)中的导频数据和所述解调后的通信数据x1(k)中的导频位置的数据在频域上利用最小二乘法对水声信道进行估计,获得如式(2-1)所示的导频位置处的信道响应的估计值 9) The channel estimation and compensation module in the signal processor utilizes the pilot data in the communication data x(k) inserted with the pilot data and the data of the pilot position in the demodulated communication data x 1 (k) Use the least square method to estimate the underwater acoustic channel in the frequency domain, and obtain the estimated value of the channel response at the pilot position as shown in formula (2-1)
接着,利用式(2-2)所示的线性插值方法,在所述估计值的所有相邻的两个元素和之间进行线性插值,得到完整的信道响应h(k);Then, using the linear interpolation method shown in formula (2-2), in the estimated value All adjacent two elements of and Perform linear interpolation between to get the complete channel response h(k);
式(2-2)中,表示完整信道响应的第m×L个信道响应的估计值,表示完整信道响应的第m×L+L个信道响应的估计值,表示完整信道响应的第m×L+l个信道响应的估计值,m=1,2,…,M,l=1,2,…L,M表示插有导频数据的通信数据x(k)内的导频数据的数量,L表示插有导频数据的通信数据x(k)的导频间隔;In formula (2-2), represents the estimated value of the m×L channel response of the complete channel response, represents the estimated value of the m×L+L channel response of the complete channel response, Represents the estimated value of the m×L+l channel response of the complete channel response, m=1, 2,..., M, l=1, 2,...L, M represents the communication data x(k ), L represents the pilot interval of the communication data x(k) inserted with the pilot data;
然后,利用式(3)所示的方法消除水声信道对解调后的通信数据x1(k)的影响而得到经过信道补偿的通信数据x2(k),Then, the channel-compensated communication data x 2 (k) is obtained by eliminating the influence of the underwater acoustic channel on the demodulated communication data x 1 (k) by using the method shown in formula (3),
x2(k)=x1(k)/h(k) (3)x 2 (k) = x 1 (k)/h(k) (3)
10)信号处理器中的频偏估计与补偿模块利用式(4)所示的方法估计出经过信道补偿的通信数据x2(k)的频偏然后利用式(5)所示的方法对经过信道补偿的通信数据x2(k)进行频偏补偿而得到新的通信数据x3(k):10) The frequency offset estimation and compensation module in the signal processor uses the method shown in formula (4) to estimate the frequency offset of the channel-compensated communication data x 2 (k) Then use the method shown in formula (5) to perform frequency offset compensation on the channel-compensated communication data x 2 (k) to obtain new communication data x 3 (k):
式(4)中,xmL表示插有导频数据的通信数据x(k)中的第m个导频数据,为xmL的共轭,pmL表示经过信道补偿的通信数据x2(k)中的第m个导频位置的数据,angle表示取方括号内式子的相位角,T表示OFDM信号s(j)的持续时间;此处的式(5)中,j表示虚数符号。In formula (4), x mL represents the mth pilot data in the communication data x(k) inserted with pilot data, is the conjugate of x mL , p mL represents the data of the mth pilot position in the channel-compensated communication data x 2 (k), angle represents the phase angle of the formula in square brackets, and T represents the OFDM signal s( j) duration; in the formula (5) here, j represents an imaginary number sign.
优选地,本发明在步骤1)中,所述线性调频信号l(i)的时间长度和带宽的乘积大于100。Preferably, in step 1) of the present invention, the product of the time length and bandwidth of the chirp signal l(i) is greater than 100.
与现有技术相比,本发明的有益效果是:本发明利用时反的空时聚焦特性,消除了信道的多径影响,消除了信道的时延,时反可以缩短脉冲信道响应长度,缩短了OFDM信号s(j)保护间隔的长度,提高了通信效率;同时缩短了OFDM信号s(j)的长度,增大OFDM信号s(j)的子载波间隔,减少了子载波间干扰,进一步提升OFDM水声通信的可用速率,提高了通信性能。线性调频信号可以用来进行多普勒因子的估计,而且,用线性调频信号作为探测源,进行被动时反处理没有带来效率上的损失。Compared with the prior art, the beneficial effects of the present invention are: the present invention utilizes the space-time focusing characteristic of the time inverse, eliminates the multipath influence of the channel, eliminates the time delay of the channel, and the time inverse can shorten the pulse channel response length, shorten The length of the guard interval of the OFDM signal s(j) is improved, and the communication efficiency is improved; at the same time, the length of the OFDM signal s(j) is shortened, the subcarrier spacing of the OFDM signal s(j) is increased, and the inter-subcarrier interference is reduced, further The available rate of OFDM underwater acoustic communication is increased, and the communication performance is improved. The chirp signal can be used to estimate the Doppler factor, and, using the chirp signal as a detection source, passive time-reverse processing does not bring about loss of efficiency.
附图说明 Description of drawings
图1是本发明基于时反和OFDM联合处理的水声通信装置的结构框图;Fig. 1 is the structural block diagram of the underwater acoustic communication device based on time inverse and OFDM joint processing of the present invention;
图2是本发明的信号处理器的结构示意图;Fig. 2 is the structural representation of signal processor of the present invention;
图3是本发明的信号处理器中的时反处理模块的工作原理图;Fig. 3 is the working principle diagram of the time inversion processing module in the signal processor of the present invention;
图4是本发明的信号发射机所产生的通信信号的格式;Fig. 4 is the format of the communication signal that signal transmitter of the present invention produces;
图5是本发明的其中一个实施例的典型波导环境示意图;Fig. 5 is a schematic diagram of a typical waveguide environment according to one embodiment of the present invention;
图6是在图4所示格式下,信号发射机所产生的通信信号的时域图;Fig. 6 is a time-domain diagram of the communication signal generated by the signal transmitter under the format shown in Fig. 4;
图7是本发明中的宽带多普勒估计与补偿模块进行相关运算的结果图;Fig. 7 is the result figure that the wideband Doppler estimation and compensation module in the present invention carry out correlation operation;
图8经过时反和OFDM联合处理后的星座图。Figure 8 is the constellation diagram after joint processing of time inversion and OFDM.
具体实施方式Detailed ways
下面结合附图和具体实例对本发明做进一步的描述。The present invention will be further described below in conjunction with the accompanying drawings and specific examples.
如图1所示,本发明基于时反和OFDM联合处理的水声通信装置包括信号发射机、功率放大器、发射换能器、接收水听器阵、信号接收机和信号处理器。其中:As shown in Fig. 1, the underwater acoustic communication device based on time-reverse and OFDM joint processing of the present invention includes a signal transmitter, a power amplifier, a transmitting transducer, a receiving hydrophone array, a signal receiver and a signal processor. in:
信号发射机用于产生通信信号,所述通信信号包括线性调频信号和OFDM信号,且线性调频信号和OFDM信号之间插入有保护间隔,其中,OFDM信号是通过将外部通信数据插入导频数据后经OFDM调制而成;The signal transmitter is used to generate a communication signal, the communication signal includes a chirp signal and an OFDM signal, and a guard interval is inserted between the chirp signal and the OFDM signal, wherein the OFDM signal is obtained by inserting the external communication data into the pilot data Modulated by OFDM;
功率放大器用于将通信信号进行功率放大;The power amplifier is used to amplify the power of the communication signal;
发射换能器用于将放大后的通信信号转化为声信号,并将声信号发射至水中;The transmitting transducer is used to convert the amplified communication signal into an acoustic signal, and transmit the acoustic signal into the water;
接收水听器阵用于接收发射换能器发射至水中的通信声信号,并将所述声信号转换为电信号;The receiving hydrophone array is used to receive the communication acoustic signal emitted by the transmitting transducer into the water, and convert the acoustic signal into an electrical signal;
信号接收机用于将所述电信号转换为数字信号并存储;The signal receiver is used to convert the electrical signal into a digital signal and store it;
信号处理器包括宽带多普勒估计与补偿模块、时反处理模块、OFDM解调模块、信道估计与补偿模块和频偏估计与补偿模块。其中,宽带多普勒估计与补偿模块用于对信号接收机存储的电信号进行多普勒因子的估计和宽带多普勒补偿;时反处理模块用于对经过宽带多普勒补偿后的信号进行被动时反处理;OFDM解调模块用于对经过被动时反处理的信号进行OFDM解调;信道估计与补偿模块用于利用最小二乘信道估计方法和OFDM解调后的信号估计出水声信道的响应,并消除水声信道对OFDM解调后的信号的影响;频偏估计与补偿模块用于对经过信道估计与补偿模块处理后的信号进行频偏估计和补偿。The signal processor includes a wideband Doppler estimation and compensation module, a time inversion processing module, an OFDM demodulation module, a channel estimation and compensation module and a frequency offset estimation and compensation module. Among them, the wideband Doppler estimation and compensation module is used for Doppler factor estimation and wideband Doppler compensation for the electrical signal stored in the signal receiver; the time inversion processing module is used for the signal after wideband Doppler compensation Perform passive time inverse processing; OFDM demodulation module is used to perform OFDM demodulation on the passive time inverse processed signal; channel estimation and compensation module is used to estimate the underwater acoustic channel by using the least squares channel estimation method and the signal after OFDM demodulation response, and eliminate the influence of the underwater acoustic channel on the OFDM demodulated signal; the frequency offset estimation and compensation module is used to perform frequency offset estimation and compensation on the signal processed by the channel estimation and compensation module.
如图2所示,本发明的信号处理器主要由宽带多普勒估计与补偿模块、时反处理模块、OFDM解调模块、信道估计与补偿模块和频偏估计与补偿模块组成。As shown in Figure 2, the signal processor of the present invention is mainly composed of a wideband Doppler estimation and compensation module, a time inverse processing module, an OFDM demodulation module, a channel estimation and compensation module and a frequency offset estimation and compensation module.
本发明水声通信装置和方法可适用于各种环境,比如浅海、湖泊等环境的水声通信。本发明的外部通信数据包括语音、视频、文本等的编码数据。下面以图5所示的典型波导环境且以QPSK(四相相移键控)编码数据作为外部通信数据为例来详细说明本发明的技术方案。The underwater acoustic communication device and method of the present invention are applicable to various environments, such as underwater acoustic communication in environments such as shallow seas and lakes. The external communication data of the present invention includes coded data of voice, video, text, and the like. The technical solution of the present invention will be described in detail below by taking the typical waveguide environment shown in FIG. 5 and taking QPSK (Quadrature Phase Shift Keying) encoded data as the external communication data as an example.
在图5中,波导环境由两部分构成:水介质层和沉积层。并且,在本实施例中,水介质层的深度为1.42米,沉积层的深度为0.22米;接收水听器阵是一个有16个阵元的垂直阵,相邻两阵元的间距0.08米,最上面的阵元距水面0.04米;波导中的发射换能器距水面0.6米,发射换能器与接收水听器阵的水平距离为8米。此外,c表示声速,ρ表示介质密度,α表示介质的声吸收系数。以下具体说明进行时反和OFDM联合处理的水声通信步骤:In Figure 5, the waveguide environment consists of two parts: the aqueous medium layer and the sediment layer. And, in this embodiment, the depth of the water medium layer is 1.42 meters, and the depth of the sedimentary layer is 0.22 meters; the receiving hydrophone array is a vertical array with 16 array elements, and the distance between two adjacent array elements is 0.08 meters , the uppermost array element is 0.04 meters away from the water surface; the transmitting transducer in the waveguide is 0.6 meters away from the water surface, and the horizontal distance between the transmitting transducer and the receiving hydrophone array is 8 meters. In addition, c represents the speed of sound, ρ represents the density of the medium, and α represents the sound absorption coefficient of the medium. The following specifically describes the underwater acoustic communication steps for time-reversal and OFDM joint processing:
1.信号发射机产生通信信号:1. The signal transmitter generates a communication signal:
本发明需要对通信信号进行特别设计,图4示出了通信信号的一种具体的格式:从左到右依次为线性调频信号、保护间隔、OFDM信号、保护间隔、线性调频信号。图4所示通信信号的时域形式则如图6所示。作为本发明的优选方案,线性调频信号l(i)的时间长度与带宽的乘积大于100,这样可使多普勒因子估计误差少于1%。当然,在本发明中,线性调频信号l(i)的时间长度与带宽的乘积在发射换能器和接收水听器阵相对静止时也可以小于或等于100。The present invention requires a special design of the communication signal. FIG. 4 shows a specific format of the communication signal: from left to right, it is a chirp signal, a guard interval, an OFDM signal, a guard interval, and a chirp signal. The time domain form of the communication signal shown in FIG. 4 is shown in FIG. 6 . As a preferred solution of the present invention, the product of the time length and bandwidth of the chirp signal l(i) is greater than 100, so that the Doppler factor estimation error can be less than 1%. Of course, in the present invention, the product of the time length and bandwidth of the chirp signal l(i) may also be less than or equal to 100 when the transmitting transducer and the receiving hydrophone array are relatively stationary.
信号发射机产生线性调频信号l(i),并在外部通信数据中插入导频数据而得到插有导频数据的通信数据x(k),将插有导频数据的通信数据x(k)经OFDM调制成第一OFDM信号s(j),然后在线性调频信号l(i)和OFDM信号s(j)之间插入时间长度为T的保护间隔形成通信信号。本发明中,插入导频数据的间隔为L。其中,i=1,2,…I,k=1,2,…,K,j=1,2,…,J;I为线性调频信号l(i)的长度,K为插有导频数据的通信数据x(k)的长度,J为OFDM信号s(j)的长度,且I、K、J、L均为任意大于1的正整数,T为任意非负数。The signal transmitter generates the chirp signal l(i), and inserts the pilot data into the external communication data to obtain the communication data x(k) inserted with the pilot data, and the communication data x(k) inserted with the pilot data The first OFDM signal s(j) is modulated by OFDM, and then a guard interval of time length T is inserted between the chirp signal l(i) and the OFDM signal s(j) to form a communication signal. In the present invention, the interval for inserting pilot data is L. Wherein, i=1, 2, ... I, k=1, 2, ..., K, j=1, 2, ..., J; I is the length of the chirp signal l (i), and K is inserted with pilot data The length of communication data x(k), J is the length of OFDM signal s(j), and I, K, J, L are any positive integers greater than 1, and T is any non-negative number.
仅仅作为本发明的一个示例,在本实施例中,可将通信信号的有关参数作如下设定:线性调频信号l(i)的长度I=800,起始频率为6000赫兹,截止频率为14000赫兹,带宽8000赫兹,时间长度为0.02秒,线性调频信号l(i)的时间长度和带宽乘积为0.02×8000=160。在QPSK编码数据中插入导频后,所得到的插有导频数据的通信数据x(k)的长度K=600,且插入导频数据的间隔L=10。通信数据x(k)经OFDM调制所形成的OFDM信号s(j)的长度J=4096,OFDM信号s(j)的起始频率为7000赫兹,截止频率为13000赫兹,时间长度为0.1秒;在线性调频信号l(i)和OFDM信号s(j)之间插入时间长度T为0.02秒的0作为保护间隔而形成如图6所示的通信信号。Only as an example of the present invention, in this embodiment, the relevant parameters of the communication signal can be set as follows: the length I=800 of the chirp signal l(i), the starting frequency is 6000 Hz, and the cut-off frequency is 14000 Hertz, the bandwidth is 8000 Hz, the time length is 0.02 seconds, and the product of the time length and bandwidth of the chirp signal l(i) is 0.02×8000=160. After the pilot is inserted into the QPSK coded data, the length of the obtained communication data x(k) inserted with the pilot data is K=600, and the interval of inserting the pilot data is L=10. The length of OFDM signal s(j) formed by OFDM modulation of communication data x(k) is J=4096, the start frequency of OFDM signal s(j) is 7000 Hz, the cut-off frequency is 13000 Hz, and the time length is 0.1 second; A 0 with a time length T of 0.02 seconds is inserted between the chirp signal l(i) and the OFDM signal s(j) as a guard interval to form a communication signal as shown in FIG. 6 .
2.功率放大器将信号发射机产生的通信信号放大后输入到放置于水中的发射换能器中,再由发射换能器将其转换为声信号发射出去。2. The power amplifier amplifies the communication signal generated by the signal transmitter and inputs it into the transmitting transducer placed in the water, and then the transmitting transducer converts it into an acoustic signal and emits it.
3.接收水听器阵在水中将所接收到的发射换能器发送的声信号转换为电信号,信号接收机再将电信号转换为数字信号Y(n)并进行存储,并将数字信号Y(n)输入到信号处理器中进行处理。3. The receiving hydrophone array converts the received acoustic signal sent by the transmitting transducer into an electrical signal in the water, and the signal receiver converts the electrical signal into a digital signal Y(n) and stores it, and stores the digital signal Y(n) is input to the signal processor for processing.
4.信号处理器中的宽带多普勒估计和补偿模块对接收到的数字信号Y(n)进行宽带多普勒补偿。在图4所示的通信信号格式中,当线性调频信号l(i)的时间长度和带宽的乘积大于100时,可以利用数字信号Y(n)和线性调频信号l(i)进行如式(1)所示的相关运算,其结果xcor如图7所示,其峰值间隔就是数字信号Y(n)的两相邻线性调频信号的时间间隔T2。通过式(2)得到数字信号Y(n)中的各相邻的两个线性调频信号之间的多普勒因子α后,再根据式(3)相应得到各插值因子D。然后,利用各插值因子D分别在与其对应的两个相邻的线性调频信号之间进行插值,直至在所有相邻的两个线性调频信号间都进行了相应的插值,由此消除了信道对数字信号Y(n)的影响而得到补偿后的信号Y1(n)。以下以Y(n)中有三个线性调频信号为例进行具体的说明:4. The wideband Doppler estimation and compensation module in the signal processor performs wideband Doppler compensation on the received digital signal Y(n). In the communication signal format shown in Figure 4, when the product of the time length and bandwidth of the chirp signal l(i) is greater than 100, the digital signal Y(n) and the chirp signal l(i) can be used to perform the following equation ( For the correlation operation shown in 1), the result xcor is shown in Figure 7, and the peak interval is the time interval T 2 between two adjacent chirp signals of the digital signal Y(n). After the Doppler factor α between two adjacent chirp signals in the digital signal Y(n) is obtained through formula (2), each interpolation factor D is correspondingly obtained according to formula (3). Then, each interpolation factor D is used to perform interpolation between the corresponding two adjacent chirp signals until the corresponding interpolation is performed between all the adjacent two chirp signals, thereby eliminating the channel pair The compensated signal Y 1 (n) is obtained from the influence of the digital signal Y(n). The following takes three chirp signals in Y(n) as an example for specific description:
如果Y(n)中有三个线性调频信号,那么对数字信号Y(n)和线性调频信号l(i)进行如式(1)所示的相关运算,分别得到前两个相邻线性调频信号的间隔T2=b,后两个相邻线性调频信号的时间间隔T2=c。利用式(2)得到前两个相邻线性调频信号的多普勒因子α1=1-b/T1,再利用插值因子D1=1+α1在前两个相邻线性调频信号之间进行插值;同样,利用式(2)得到后两个相邻线性调频信号的多普勒因子α2=1-c/T1,再利用插值因子D2=1+α2在后两个相邻线性调频信号间插值。由此,在所有相邻两个线性调频信号间都进行了相应的插值后所得到的信号就是Y1(n)。当Y(n)中的线性调频信号的数量为其他数值时,按上述示例的方法在所有相邻的两个线性调频信号之间进行相应的插值即可。If there are three chirp signals in Y(n), then the correlation operation shown in formula (1) is performed on the digital signal Y(n) and the chirp signal l(i), and the first two adjacent chirp signals are respectively obtained The interval T 2 =b, and the time interval T 2 =c of the last two adjacent chirp signals. Use formula (2) to obtain the Doppler factor α1=1-b/T 1 of the first two adjacent chirp signals, and then use the interpolation factor D1=1+α1 to interpolate between the first two adjacent chirp signals ; Similarly, use formula (2) to obtain the Doppler factor α2=1-c/T 1 of the last two adjacent chirp signals, and then use the interpolation factor D2=1+α2 between the last two adjacent chirp signals interpolation. Thus, the signal obtained after corresponding interpolation is performed between all two adjacent chirp signals is Y 1 (n). When the number of chirp signals in Y(n) is other values, corresponding interpolation between all two adjacent chirp signals can be performed according to the method of the above example.
α=1-T2/T1 (2)α=1-T 2 /T 1 (2)
D=1+α (3)D=1+α
式(1)中,表示卷积运算,l*(-i)表示所述线性调频信号l(i)时反的共轭。式(2)中T1为信号发射机产生的两相邻线性调频信号l(i)的间隔。In formula (1), represents a convolution operation, and l * (-i) represents the conjugate of the inverse of the chirp signal l(i). T 1 in formula (2) is the interval between two adjacent chirp signals l(i) generated by the signal transmitter.
5.信号处理器中的时反处理模块对经过多普勒补偿的信号Y1(n)利用线性调频信号l(i)作为探查源,按照图3所示的流程对各路信号进行被动时反处理。其做法是:从经过多普勒补偿的信号Y1(n)中截取接收的线性调频信号lr(i)和OFDM信号sr(j)。利用式(4)所示方法,得到被动时反处理后的OFDM信号s1(j)。5. The time-reversal processing module in the signal processor uses the chirp signal l(i) as a probe source for the Doppler-compensated signal Y 1 (n), and passively time-modulates each signal according to the process shown in Figure 3. Anti-handling. The method is: intercept the received chirp signal l r (i) and OFDM signal s r (j) from the Doppler compensated signal Y 1 (n). Using the method shown in formula (4), the OFDM signal s 1 (j) after passive time inverse processing is obtained.
式(3)中,ifft表示傅立叶反变换,fft表示傅立叶变换,lqr(i)表示所述线性调频信号lr(i)的第q行信号,sqr(j)为所述OFDM信号sr(j)的第q行信号;l(i)表示信号发射机产生的线性调频信号,[fft(lqr(i))]*表示fft(lqr(i))的共轭,q为小于等于Q的正整数,Q为接收阵元个数,本实施实例中Q=16。由于本发明设有时反处理模块,因此允许信号发射机产生更短时间长度的OFDM信号s(j),增大所述OFDM信号s(j)的子载波间隔,减少了OFDM信号s(j)的子载波间干扰。而且线性调频信号在多普勒因子估计和补偿模块中用来估计多普勒因子α,又在时反处理模块中用作探查源,没有带来效率上的损失。In formula (3), ifft represents the inverse Fourier transform, fft represents the Fourier transform, l qr (i) represents the qth line signal of the chirp signal l r (i), and s qr (j) is the OFDM signal s The qth row signal of r (j); l(i) represents the chirp signal generated by the signal transmitter, [fft(l qr (i))] * represents the conjugate of fft(l qr (i)), and q is A positive integer less than or equal to Q, where Q is the number of receiving array elements, and Q=16 in this implementation example. Since the present invention is equipped with a time inverse processing module, the signal transmitter is allowed to generate OFDM signal s(j) with a shorter time length, the subcarrier spacing of said OFDM signal s(j) is increased, and the OFDM signal s(j) is reduced. inter-subcarrier interference. Moreover, the chirp signal is used to estimate the Doppler factor α in the Doppler factor estimation and compensation module, and is used as a probe source in the time inverse processing module, without loss of efficiency.
6.信号处理器中的OFDM解调模块对经过被动时反处理后的OFDM信号s1(j)进行解调操作,得到通信数据x1(k)。6. The OFDM demodulation module in the signal processor performs a demodulation operation on the OFDM signal s 1 (j) after passive time inverse processing to obtain communication data x 1 (k).
7.信号处理器中的信道估计与补偿模块利用插有导频数据的通信数据x(k)中的导频数据和通信数据x1(k)中的导频位置的数据在频域上利用式(5)所示的最小二乘法对水声信道进行估计,得到导频处的信道响应的估计值 7. The channel estimation and compensation module in the signal processor uses the pilot data in the communication data x(k) inserted with the pilot data and the data of the pilot position in the communication data x 1 (k) In the frequency domain, use the least square method shown in formula (5) to estimate the underwater acoustic channel, and obtain the estimated value of the channel response at the pilot
接着,在所述估计值的每相邻的两个元素和之间利用式(6)所示的线性插值方法分别进行插值,共经过M×L次插值后可得到完整的信道响应h(k),Next, in the estimated Every two adjacent elements of and The linear interpolation method shown in formula (6) is used to perform interpolation respectively, and the complete channel response h(k) can be obtained after a total of M×L times of interpolation.
式(6)中,表示完整信道响应的第m×L个信道响应估计值,表示完整信道响应的第m×L+L个信道响应估计值,表示完整信道响应的第m×L+l个信道响应估计值,m=1,2,…,M,l=1,2,…L;M表示插有导频数据的通信数据x(k)内的导频数据的数量,L为通信数据x(k)的导频间隔,M和L为任意大于1的正整数。在本实施例中,M=60,L=10。In formula (6), represents the m×Lth channel response estimate of the full channel response, represents the m×L+L channel response estimate of the complete channel response, Represents the m×L+l estimated channel response value of the complete channel response, m=1, 2,..., M, l=1, 2,...L; M represents the communication data x(k) inserted with pilot data The number of pilot data in , L is the pilot interval of the communication data x(k), M and L are any positive integer greater than 1. In this embodiment, M=60, L=10.
然后,利用式(7)所示的方法消除水声信道对解调后的通信数据x1(k)的影响而得到经过信道补偿的通信数据x2(k),Then, the channel-compensated communication data x 2 (k) is obtained by eliminating the influence of the underwater acoustic channel on the demodulated communication data x 1 (k) by using the method shown in formula (7),
x2(k)=x1(k)/h(k) (7)x 2 (k) = x 1 (k)/h(k) (7)
8.信号处理器中的频偏估计与补偿模块利用式(8)估计出频偏然后利用式(9)对经过信道补偿的通信数据x2(k)进行频偏补偿而得到通信数据x3(k):8. The frequency offset estimation and compensation module in the signal processor uses formula (8) to estimate the frequency offset Then use formula (9) to perform frequency offset compensation on the channel-compensated communication data x 2 (k) to obtain communication data x 3 (k):
式(4)中,xmL表示插有导频数据的通信数据x(k)中的第m个导频数据,为xmL的共轭,pmL表示经过信道补偿的通信数据x2(k)中的第m个导频位置的数据,angle表示取方括号内式子的相位角,T表示OFDM信号s(j)的持续时间;此处的式(9)中,j表示虚数符号。In formula (4), x mL represents the mth pilot data in the communication data x(k) inserted with pilot data, is the conjugate of x mL , p mL represents the data of the mth pilot position in the channel-compensated communication data x 2 (k), angle represents the phase angle of the formula in square brackets, and T represents the OFDM signal s( j) duration; in the formula (9) here, j represents the imaginary number sign.
为了验证本发明的效果,对经过信号处理器处理所得到的通信数据x3(k)与信号发射机产生的通信数据x(k)进行比较,其误码率为0,绘制星座图如图8所示。从图8所示的星座图可以看出,本发明的通信效果很好。In order to verify the effect of the present invention, the communication data x 3 (k) obtained through signal processor processing is compared with the communication data x(k) produced by the signal transmitter, and the bit error rate is 0, and the constellation diagram is drawn as shown in the figure 8. It can be seen from the constellation diagram shown in FIG. 8 that the communication effect of the present invention is very good.
Claims (3)
- One kind based on the time anti-and OFDM Combined Treatment the underwater sound communication device; It is characterized in that; Comprise: signal transmitter, be used to form signal of communication, said signal of communication comprises linear FM signal and ofdm signal; And be inserted with protection between Linear Frequency Modulation signal and the ofdm signal at interval, said ofdm signal is through the PERCOM peripheral communication data being inserted pilot data after the OFDM modulation forms.Power amplifier is used for said signal of communication is carried out power amplification;Transmitting transducer is used for the signal of communication after amplifying is converted into acoustical signal, and acoustical signal is emitted in the water;The receiving hydrophone battle array is used for receiving the acoustical signal that transmitting transducer is emitted to water, and converts said acoustical signal into the signal of telecommunication;Signal receiver, being used for said electrical signal conversion is digital signal and storage;Signal processor, this signal processor comprises:---broadband Doppler estimates and compensating module, is used for signal receiver stored numbers signal is carried out the estimation and the broadband Doppler effect correction of Doppler's factor;---the time anti-processing module, be used for carry out anti-processing when passive through the signal behind the Doppler effect correction of broadband;---the OFDM demodulation module is used for the anti-signal of handling when passive is carried out the OFDM demodulation;---channel estimating and compensating module, be used to utilize after the OFDM demodulation signal with adopt the least square channel estimation methods to estimate the response of underwater acoustic channel, and the influence of eliminating the signal of underwater acoustic channel after to the OFDM demodulation;---frequency offset estimating and compensating module are used for carrying out frequency offset estimating and compensation through the signal after channel estimating and the compensating module processing.
- 2. the underwater acoustic communication method of anti-and OFDM Combined Treatment is characterized in that comprising the steps: when a device that utilizes claim 1 carried out1) signal transmitter produces linear FM signal l (i); And externally insert pilot data in the communication data and obtain being inserted with the communication data x (k) of pilot data; The communication data x (k) that is inserted with pilot data is modulated into the first ofdm signal s (j) through OFDM, inserts protection then between Linear Frequency Modulation signal l (i) and the ofdm signal s (j) and form signal of communication at interval; I=1 wherein, 2 ..., I, I are the length of linear FM signal; K=1,2 ..., K, K are the length that is inserted with the communication data x (k) of pilot data; J=1,2 ..., J, J are the length of ofdm signal s (j), I, K, J are the positive integer greater than 1.2) said signal of communication sends to the transmitting transducer that is positioned in the water after amplifying through power amplifier;3) signal of communication after transmitting transducer will amplify is converted into acoustical signal and is emitted in the water;4) utilize the receiving hydrophone battle array that is positioned in the water to receive transmitting transducer and be emitted to the acoustical signal in the water, and convert said acoustical signal into the signal of telecommunication;5) signal receiver converts receiving hydrophone battle array institute electrical signal converted into digital signal Y (n) and stores;6) the broadband Doppler in the signal processor estimates earlier said digital signal Y (n) and linear FM signal l (i) to be carried out related operation with compensating module, utilizes the result of said related operation to estimate T blanking time between all two the adjacent linear FM signals among the digital signal Y (n) then 2, obtain suc as formula the interpolation factor D shown in that Doppler's factor-alpha shown in (1-1) and the formula (1-2):α=1-T 2/T 1 (1-1)D=1+α (1-2)In the formula (1-1), T 1The blanking time of two adjacent linear FM signals that the expression signal transmitter produces;Then, utilize said interpolation factor D that said digital signal Y (n) is carried out the signal Y after interpolation is compensated 1(n);7) the time anti-processing module in the signal processor utilizes linear FM signal l (i) as detection source, to the signal Y after the said compensation 1(n) carry out on frequency domain that anti-the processing obtains the second ofdm signal s when passive 1(j);8) the OFDM demodulation module in the signal processor is to the said second ofdm signal s 1(j) carry out demodulation, obtain the communication data x after the demodulation 1(k);9) channel estimating in the signal processor and compensating module utilize the pilot data among the said communication data x (k) that is inserted with pilot data With the communication data x after the said demodulation 1The data of the pilot frequency locations (k) On frequency domain, utilize least square method that underwater acoustic channel is estimated, obtain estimated value suc as formula the channel response at the pilot frequency locations place shown in (2-1)Then; Utilize the linear interpolation method shown in the formula (2-2); Between all two adjacent elements of said estimated value and , carry out linear interpolation, obtain complete channel response h (k);In the formula (2-2); The estimated value of the m * L channel response of the complete channel response of expression; The estimated value of the m * L+L channel response of the complete channel response of expression; The estimated value of the m * L+l channel response of the complete channel response of expression; M=1; 2;, M, l=1; 2; L, M represent to be inserted with the quantity of the pilot data in the communication data x (k) of pilot data, and L representes to be inserted with the pilot interval of the communication data x (k) of pilot data;Then, utilize the method shown in the formula (3) to eliminate the communication data x of underwater acoustic channel after to demodulation 1(k) influence and obtain the communication data x through channel compensation 2(k),x 2(k)=x 1(k)/h(k) (3)10) frequency offset estimating in the signal processor and compensating module utilize the method shown in the formula (4) to estimate the communication data x through channel compensation 2(k) frequency deviation Utilize the method shown in the formula (5) to communication data x then through channel compensation 2(k) carry out compensate of frequency deviation and obtain new communication data x 3(k):In the formula (4), x MLExpression is inserted with m pilot data among the communication data x (k) of pilot data, Be x MLConjugation, p MLExpression is through the communication data x of channel compensation 2The data of m pilot frequency locations (k), angle representes to get the phase angle of formula in the square brackets, and T representes the duration of ofdm signal s (j); In the formula (5), j representes imaginary symbols.
- 3. underwater acoustic communication method according to claim 2 is characterized in that: in step 1), the time span of said linear FM signal l (i) and the product of bandwidth are greater than 100.
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