WO2019101032A1 - 一种基于子带选择激活的多带双曲调频扩频水声通信方法 - Google Patents

一种基于子带选择激活的多带双曲调频扩频水声通信方法 Download PDF

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WO2019101032A1
WO2019101032A1 PCT/CN2018/116144 CN2018116144W WO2019101032A1 WO 2019101032 A1 WO2019101032 A1 WO 2019101032A1 CN 2018116144 W CN2018116144 W CN 2018116144W WO 2019101032 A1 WO2019101032 A1 WO 2019101032A1
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sub
band
group
frequency
hyperbolic
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余华
周永进
季飞
陈芳炯
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South China University of Technology SCUT
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B11/00—Transmission systems employing ultrasonic, sonic or infrasonic waves
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B13/00—Transmission systems characterised by the medium used for transmission, not provided for in groups H04B3/00 - H04B11/00
    • H04B13/02—Transmission systems in which the medium consists of the earth or a large mass of water thereon, e.g. earth telegraphy
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
    • H04L27/103—Chirp modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
    • H04L27/12—Modulator circuits; Transmitter circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
    • H04L27/14—Demodulator circuits; Receiver circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2626—Arrangements specific to the transmitter only
    • H04L27/2627—Modulators
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2649—Demodulators
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
    • H04L27/2695—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation with channel estimation, e.g. determination of delay spread, derivative or peak tracking
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/28—Systems using multi-frequency codes with simultaneous transmission of different frequencies each representing one code element
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

  • the present invention relates to the field of underwater acoustic communication, and in particular to a method for multi-band hyperbolic frequency modulation (Hyperbolic Frequency Modulated) underwater acoustic communication based on sub-band selection activation.
  • Hyperbolic Frequency Modulated Hyperbolic Frequency Modulated
  • the underwater acoustic channel has its particularity and complexity, which is manifested in its serious multi-path effects, time-varying characteristics and band-limited characteristics.
  • the continuous development of underwater acoustic coherent communication has obvious advantages over non-coherent communication in improving the frequency band utilization and information transmission rate.
  • severe multipath and time-varying are the main constraints of underwater acoustic coherent communication.
  • Spread spectrum (SS) technology is a technology that can effectively resist interference.
  • the communication system needs to have strong robustness.
  • the spread spectrum communication method is a kind of Better choice.
  • the conventional spread spectrum methods include direct sequence spread spectrum, hopping frequency spread spectrum, hopping time spread spectrum, and hybrid spread spectrum.
  • Linear Frequency Modulated spread spectrum and hyperbolic frequency modulation spread have been proposed.
  • a hyperbolic FM signal is selected as the spread spectrum signal.
  • Hyperbolic FM has its unique advantages as an underwater acoustic spread spectrum communication.
  • hyperbolic FM signal model is as follows:
  • Hyperbolic Frequency Modulation (HFM) signal which can be defined as
  • the instantaneous frequency of the HFM signal is the phase-to-time derivative.
  • the hyperbolic FM signal has good pulse compression and Doppler tolerance.
  • the pulse compression is embodied in the fact that the received signal can be matched and filtered to form a sharp pulse with a sharp main lobe and a weak side lobe, so it has good anti-noise performance.
  • the signal will produce temporal compression or expansion due to the Doppler effect caused by relative motion. After the signal has experienced the Doppler effect, the receiver can still form a good pulse through matched filtering, and the signal is considered to have Doppler tolerance.
  • HFM signal For an HFM signal, if you experience a Doppler spread or compression of the scale ⁇ . Receiving the HFM signal can be expressed as
  • the delay ⁇ t is a constant determined by the scale factor and independent of time.
  • a hyperbolic frequency modulation spread spectrum communication scheme combining multi-band transmission and carrier combination according to the present invention is proposed based on the signal model and background as described above.
  • the object of the present invention is to propose a multi-band hyperbolic frequency-modulated spread-frequency underwater acoustic communication method based on sub-band selective activation based on HFM signals, by extending single-band transmission to multi-band transmission, and simultaneously in one frequency modulation period.
  • the sub-bands are grouped, and each sub-band group selects different sub-bands for transmission to form different sub-band combination schemes for carrying information, thereby improving frequency band utilization.
  • the available bandwidth of the system is used for a single HFM frequency modulated signal, and the frequency modulated signal is used for the spread spectrum modulation carrying information in each frequency modulation period, so that the frequency band utilization ratio of the system is relatively low.
  • a multi-band hyperbolic frequency-modulated spread-frequency underwater acoustic communication method based on sub-band selective activation mainly comprises the following steps:
  • the receiving end performs pre-processing, synchronization, and channel estimation on the received signal.
  • the above method specifically includes the following steps:
  • the hyperbolic frequency modulation signal corresponding to the kth (1 ⁇ k ⁇ K) subbands is
  • Each K bits in the transmitted data is modulated onto a multi-band hyperbolic FM spread symbol.
  • Each K bits are divided into Q groups, corresponding to Q subband groups, each group of 2 bits.
  • the 2 bits of each group are used to control the activation of the group of sub-band carriers and the modulation of each activated sub-band carrier.
  • the activation scheme is as follows.
  • the second of each set of 2 bits is modulated using BPSK symbol mapping to the activated sub-band carrier signal.
  • S3 add a frame header.
  • the frame header adopts the LFM signal, and the entire signal frame is composed of a frame header, a guard interval, and data, and the length of each part can be adjusted according to actual needs. Then, after DA conversion and analog transmission, the front end power is amplified and then transmitted in the underwater acoustic channel.
  • the receiving end preprocesses the received signal. First, band-pass filtering is performed, and then the frame header is used for synchronization and channel estimation.
  • the present invention does not specifically discuss synchronization and channel estimation, and a general synchronization and channel estimation algorithm can be used.
  • f k0 represents the starting frequency of the kth subband
  • the first sub-band of the sub-band group is considered to be an active sub-band, and according to the modulation regulation in S2, it can be determined that the sub-band group corresponds to the transmitted symbol.
  • the second sub-band of the sub-band group is considered to be an active sub-band, and according to the modulation regulation in S2, it can be determined that the sub-band group corresponds to the transmitted symbol.
  • the despreading of the j-th sub-band group is completed, and demodulation of the two symbols b j1 b j2 transmitted by the sub-band group is obtained.
  • the present invention has the following advantages and technical effects:
  • the sequence number of the inactive subband also transmits information, and the system energy consumption is saved under the premise of transmitting the same amount of data.
  • FIG. 1 is a schematic structural diagram of a hydroacoustic hyperbolic frequency modulation spread spectrum communication scheme combining multi-band transmission and carrier combination according to the present invention.
  • FIG. 2 is a flow chart of subband group spread spectrum modulation, taking the first subband group as an example.
  • FIG. 3 is a flowchart of a subband group despreading process, taking the first subband group as an example.
  • Figure 4 is a diagram of a signal frame structure.
  • FIG. 5 is a simulation diagram of bit error rate of a specific embodiment.
  • FIG. 1 is a schematic structural diagram of a system of the present invention.
  • T L LFM frame header duration
  • ⁇ k The modulation frequency of the hyperbolic FM signal.
  • f k0 indicates the starting frequency of the kth subband.
  • a hydroacoustic hyperbolic frequency modulation spread spectrum communication scheme combining multi-band transmission and carrier combination includes the following steps:
  • a multi-band hyperbolic FM spread symbol is modulated with every K bits in the transmitted data.
  • Each K bits are divided into Q groups, corresponding to Q subband groups, each group of 2 bits.
  • the 2 bits of each group are used to control the activation of the group of sub-band carriers and the modulation of each activated sub-band carrier.
  • the second of each set of 2 bits is modulated using BPSK symbol mapping to the activated sub-band carrier signal.
  • the M multi-band hyperbolic frequency modulation symbols are modulated by the above signal modulation method to form a 1-frame signal.
  • N L T L *f s .
  • T L , T G , and T H can be adjusted according to actual needs.
  • the above data frame is transmitted in the underwater acoustic channel after DA conversion and analog transmission front end power amplification.
  • the first sub-band group is taken as an example.
  • f k0 represents the starting frequency of the kth subband
  • the activated sub-band of the sub-band group is considered to be the first sub-band, and according to the modulation regulation in S2, it can be determined that the sub-band group corresponds to the transmitted symbol.
  • the activated sub-band of the sub-band group is considered to be the second sub-band, and according to the modulation regulation in S2, it can be determined that the sub-band group corresponds to the transmitted symbol.
  • the activated subband sequence number k is determined according to the detection result of S6, and the subband is subjected to symbol demodulation.
  • the maximum merge ratio criterion is used to combine the peaks of the L paths and perform symbol decision.
  • the despreading of one subband group is completed, and the demodulation of the two symbols b 11 b 12 transmitted by the subband group is obtained.
  • the remaining sub-band groups are processed accordingly.
  • the invention divides the available bandwidth of the system into multiple sub-bands, performs data transmission, and improves the frequency band utilization of the entire system. By selecting the method of activating sub-bands, the system energy consumption is saved under the premise of transmitting the same amount of data. It can also be seen from the bit error rate simulation diagram of FIG. 5 that this embodiment can still maintain a good bit error rate BER performance at a lower signal to noise ratio SNR after the Doppler spread of the signal, and by selecting an activator. Carrier mode reduces energy loss and interference between adjacent carriers.

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  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

本发明公开了一种基于子带选择激活的多带双曲调频扩频水声通信方法。本发明提出了将水声系统可用带宽划分为多个子带，每个子带分别进行双曲调频，在同一个调频周期内，对多个子带进行扩频调制，实现多带并行传输。在此基础之上，在每个调频周期内，将划分的多个子带进行分组，每个子带组根据传输数据的不同选择激活不同的子带进行传输。相对于其他的水声双曲调频通信方案，本发明进一步提高了系统的频带利用率，同时能量效率也有所改善。

Description

一种基于子带选择激活的多带双曲调频扩频水声通信方法 技术领域
本发明涉及水声通信领域，具体涉及一种基于子带选择激活(Sub-band selection activation)的多带双曲调频扩频(Hyperbolic Frequency Modulated)水声通信方法。
背景技术
水声信道具有其特殊性和复杂性，表现在其严重的多途效应、时变特性以及带限特性等方面。近年来持续发展的水声相干通信在提高频带利用率和信息传输速率上，较非相干通信有着较明显的优势。然而严重的多径与时变性，是水声相干通信主要的制约因素，与此同时在信噪比较低的环境下，较难确保通信的可靠性。
扩展频谱(spread spectrum,SS)技术是一种能有效对抗干扰的技术，在信道多径严重的环境中，要求通信系统要具备较强的鲁棒性，此时采用扩频通信方式是一种较好的选择。传统的扩频方式有直接序列扩频，跳变频率扩频，跳变时间扩频以及混合扩频等。后续，又有人提出了线性调频(Linear Frequency Modulated)扩频以及双曲调频扩频。本发明中选取双曲调频信号作为扩频信号。双曲调频作为水声扩频通信(Underwater acoustic spread spectrum communication)方式，具备其独特的优势。
为了便于对后续算法的理解，双曲调频信号模型如下所示：
双曲调频(HFM)信号，可以定义为
Figure PCTCN2018116144-appb-000001
其中
Figure PCTCN2018116144-appb-000002
表示调频率，B表示带宽(调频区间)，f 0表示起始频率，f 1＝f 0+B 表示终止频率，T表示HFM信号持续周期。HFM信号的瞬时频率为相位对时间取导数，
Figure PCTCN2018116144-appb-000003
这是一个关于时间t的双曲函数，因此该信号被称为双曲调频信号。双曲调频信号具有良好的脉冲压缩性和多普勒宽容性。其脉冲压缩性体现在，接收信号经过匹配滤波能够形成主瓣尖锐、旁瓣迅速衰弱的脉冲，因此具备良好的抗噪性能。与此同时，在信号传输过程中，由于相对运动会造成多普勒效应，信号会产生时间上的压缩或者扩展。在信号经历了多普勒效应之后，接收端经过匹配滤波依旧可以较好的形成脉冲，则认为该信号具有多普勒宽容性。
对于一个HFM信号而言，假如经历一个尺度为α的多普勒扩展或者压缩。接收HFM信号可以表达为
Figure PCTCN2018116144-appb-000004
此时信号的瞬时频率变为
Figure PCTCN2018116144-appb-000005
这里我们可以找到一个合适的Δt，使得f'(t-Δt)＝f(t)，即
Figure PCTCN2018116144-appb-000006
Figure PCTCN2018116144-appb-000007
由此可见时延Δt是一个由尺度因子决定并与时间无关的常数，如此一来，HFM信号在经历了多普勒效应之后，只是产生了一个时间上的平移，这样在接收端进行匹配滤波，依旧可以形成良好的脉冲，只是脉冲的位置会平移Δt，因此HFM信号具备多普勒宽容性。
使用HFM进行扩频通信虽然能增强抗干扰能力和抗多普勒效应，但是面临的一个比较严重的问题是频带利用率比较低，因此如何提高HFM扩频通信的 频带利用率是值得研究的问题。
本发明所述的一种结合多带传输与载波组合的双曲调频扩频通信方案，正是基于如上所述的信号模型和背景所提出的。
发明内容
本发明的目的在于基于HFM信号提出了一种基于子带选择激活的多带双曲调频扩频水声通信方法，通过将单带传输扩展到多带传输，同时在一个调频周期内，将多个子带进行分组处理，每个子带组选择激活不同的子带用于传输，以形成不同的子带组合方案用于携带信息，以此提高频带利用率。
对一般的HFM扩频通信方案而言，把系统可用带宽用于单个HFM调频信号，每个调频周期内，利用该调频信号进行扩频调制携带信息，这样系统的频带利用率比较低。
本发明的目的通过以下技术方案实现。
一种基于子带选择激活的多带双曲调频扩频水声通信方法，主要包括以下步骤：
S1、将通信系统带宽分为多个子带，分别进行双曲调频；
S2、数据、子带进行分组，确定子带激活方案，并进行信号调制；
S3、对完成调制的信号添加帧头；
S4、接收端对接收信号进行预处理，同步，信道估计；
S5、计算子带检测与解调所需要的相关值；
S6、激活子带检测；
S7、激活子带解调。
上述方法中，具体包括如下步骤：
S1、首先将系统可用带宽B＝f 1-f 0(最高频率-最低频率)分为K个子带，每个子带带宽为
Figure PCTCN2018116144-appb-000008
分别对每个子带进行双曲调频，后续用于扩频调制。第 k(1≤k≤K)个子带对应的双曲调频信号为。
Figure PCTCN2018116144-appb-000009
其中
Figure PCTCN2018116144-appb-000010
S2、确定子带激活方案，并进行信号调制。将发送数据中每K个比特调制一个多带双曲调频扩频符号上。每K个比特分成Q组，与Q个子带组相对应，每组2个比特。每组的2个比特用于控制该组子带载波的激活以及每个激活子带载波的调制，激活方案如下。
每组2个比特中的第1个比特为0时，激活每组的第1个子带进行传输，当该比特为1时激活该组第2个子带进行传输。
每组2个比特中的第2个比特则采用BPSK符号映射，对该激活的子带载波信号进行调制。
记第j(j＝1,…,Q)组的2个比特为b j1b j2，则当前多带双曲调频扩频符号帧的发送信号表示为
Figure PCTCN2018116144-appb-000011
其中k j＝2j+b j1-1为第j组激活的子带编号，上式中2b j2-1表示对第j组的第2个比特则采用BPSK符号映射。
S3、添加帧头。对完成扩频调制的信号进行添加帧头。帧头采用LFM信号，整个信号帧由帧头，保护间隔，以及数据组成，其中每部分的长度均可以根据实际需要做出调整。然后经过DA转换和模拟发送前端功率放大后在水声信道中发射。
S4、接收端，对接收信号进行预处理。首先进行带通滤波，然后利用帧头进行同步和信道估计，本发明不对同步和信道估计做专门探讨，可以采用通常的同步与信道估计算法。
假设完成同步的信号表达式为r[n]，信道估计后的结果为：多径数为L条，每条路径对应的参数为幅度
Figure PCTCN2018116144-appb-000012
时延
Figure PCTCN2018116144-appb-000013
多普勒因子
Figure PCTCN2018116144-appb-000014
S5、子带激活检测与解调所需要的相关量计算。
S51、计算相关峰值偏移量。根据S4的信道估计参数，分别计算每条路径的峰值偏移量。对于一个数据帧当中的第m(1,....,M)个符号，其第l(1,..,L)条路径的峰值偏移量Δn k,m,l
Figure PCTCN2018116144-appb-000015
其中
Figure PCTCN2018116144-appb-000016
为多普勒扩展导致的偏置，f k0表示第k个子带的起始频率，
Figure PCTCN2018116144-appb-000017
为经过多普勒扩展补偿后一个双曲调频符号的点数。
S52、进行相关运算，获取峰值。根据Δn k,m,l，分别用每个子带x k[n]与r[n]对应位置进行相关运算获得峰值。对于每个数据帧，第k个子带，第m个符号，第l条路径的峰值I k,m,l可以表示为
Figure PCTCN2018116144-appb-000018
S6、激活子带的检测。根据S5中相关所获得的峰值I k,m,l进行激活子带的判决，对数据帧中的任意第m个符号，第j组(j＝1,…,Q)激活子带的判决准则如下：
若
Figure PCTCN2018116144-appb-000019
则认为该子带组的第1个子带为激活子带，同时根据S2中的调制规定，可以判定该子带组对应传输的符号中
Figure PCTCN2018116144-appb-000020
第j组激活子带编号为k j＝2j-1。
若
Figure PCTCN2018116144-appb-000021
则认为该子带组的第2个子带为激活子带，同时根据S2中的调制规定，可以判定该子带组对应传输的符号中
Figure PCTCN2018116144-appb-000022
第j组 激活子带编号为k j＝2j。
S7、激活子带的解调。第j组(j＝1,…,Q)激活子带上传输符号的解调利用最大合并比准则，对L条路径的相关峰值进行合并处理并进行符号判决：
Figure PCTCN2018116144-appb-000023
而后进行BPSK符号解映射
Figure PCTCN2018116144-appb-000024
自此，完成第j个子带组的解扩，获得该子带组传输的2个符号b j1b j2的解调。
与现有技术相比，本发明具有如下优点和技术效果：
1、将系统可用带宽划分为多个子带，进行数据传输，提高了整个系统的频带利用率。
2、通过选择激活子带的方式，非激活子带的序号也传输了信息，在传输同样多数据的前提下，节省了系统能量消耗。
附图说明
图1为本发明一种结合多带传输与载波组合的水声双曲调频扩频通信方案结构示意图。
图2为子带组扩频调制流程图，以第1子带组为例。
图3为子带组解扩处理流程图，以第1子带组为例。
图4为信号帧结构图。
图5为具体实施方案的误比特率仿真图。
具体实施方式
为使本发明的目的、技术方案及优点更加清楚、明确，以下参照附图并举实施例对本发明进一步详细说明。应当理解，此处所描述的具体实施例仅仅用 以解释本发明，并不用于限定本发明。
请参见图1，图1是本发明的系统结构示意图。
各标号的含义如下：
B：带宽，本实例取B＝6KHz。
f 0：带宽的起始频率，本实例取f 0＝9KHz。
f 1：带宽的终止频率，本实例取f 1＝15KHz。
T H：双曲调频信号的符号周期，本实例取T H＝10ms。
T G：零符号保护间隔周期，本实例取T G＝20ms。
T L：LFM帧头持续时间，本实例取T L＝20ms。
f s：双曲调频信号的采样率，本实例取f s＝100KHz。
N：双曲调频信号一个周期的样点数，N＝T H*f s本实例中N＝1000。
α k：双曲调频信号的调频率。
f k0：表示第k个子带的起始频率。
K：子带的个数，本实例取K＝8。
Q：子带分成Q个组，本实例取Q＝4。
M：每一帧信号中包含的多带双曲调频符号个数，本实例取M＝10
本实施例中一种结合多带传输与载波组合的水声双曲调频扩频通信方案包括以下步骤：
S1、生成双曲调频扩频子带载波信号并分组。将B＝f 1-f 0分为K＝8个子带，每个子带带宽为
Figure PCTCN2018116144-appb-000025
分别对每个子带进行双曲调频，用于扩频调制。第k(k＝1,Λ,K)个子带对应的双曲调频载波信号为
Figure PCTCN2018116144-appb-000026
其中
Figure PCTCN2018116144-appb-000027
为第k个子带的双曲调频率，
Figure PCTCN2018116144-appb-000028
为第k个子带的起始频率。
同时，将K个子带分成Q＝4组，每组2个子带。
S2、信号调制。用发送数据中每K个比特调制一个多带双曲调频扩频符号。每K个比特分成Q组，与Q个子带组相对应，每组2个比特。每组的2个比特用于控制该组子带载波的激活以及每个激活子带载波的调制，具体实现方式如下：
每组2个比特中的第1个比特为0时，激活每组的第1个子带进行传输，当该比特为1时激活该组第2个子带进行传输。
每组2个比特中的第2个比特则采用BPSK符号映射，对该激活的子带载波信号进行调制。
记第j(j＝1,…,Q)组的2个比特为b j1b j2，则当前多带双曲调频扩频符号帧的发送信号表示为
Figure PCTCN2018116144-appb-000029
其中k j＝2j+b j1-1为第j组激活的子带编号，上式中2b j2-1表示对第j组的第2个比特则采用BPSK符号映射。
采用上述信号调制方式调制M个多带双曲调频符号构成1帧信号。
S3、添加帧头。对完成扩频调制的信号进行添加帧头。帧头采用LFM信号，LFM信号可以表示为
Figure PCTCN2018116144-appb-000030
其中N L＝T L*f s。
信号帧结构如图4所示，T L，T G，T H均可以根据实际需要做出调整。上述数据帧经过DA转换和模拟发送前端功率放大后在水声信道中发射。
S4、接收预处理。信号经历水声信道中的多径和多普勒影响之后，在接收端，首先进行带通滤波，然后利用帧头进行同步和信道估计，本发明不对同步和信道估计做专门探讨，可以采用通常的同步与信道估计算法。将完成同步的接收信号记为r[n]，假设信道估计后的结果为，多径数为L条，每条路径对应的参数为幅度
Figure PCTCN2018116144-appb-000031
时延
Figure PCTCN2018116144-appb-000032
多普勒因子
Figure PCTCN2018116144-appb-000033
S5、子带检测与解调的相关量计算。这里以第一个子带组为例。
S51、计算相关峰值偏移量。根据S4的信道估计参数，分别计算每条路径的峰值偏移量。对于一个数据帧当中的第m(1,Λ,M)个符号，其第l(1,Λ,L)条路径的峰值偏移量应为
Figure PCTCN2018116144-appb-000034
其中
Figure PCTCN2018116144-appb-000035
为多普勒扩展导致的偏置，f k0表示第k个子带的起始频率，
Figure PCTCN2018116144-appb-000036
为经过多普勒扩展补偿后一个双曲调频符号的点数。
S52、进行相关运算，获取峰值。根据Δn k,m,l，分别用每个子带的双曲调频载波信号x k[n]与接收信号r[n]对应位置进行相关运算获得峰值。对于每个数据帧，第k个子带，第m个符号，第l条路径的峰值I k,m,l可以表示为
Figure PCTCN2018116144-appb-000037
S6、激活子带检测。根据S5中相关所获得的峰值I k,m,l进行激活子带的判决，对数据帧中的任意第m个符号，激活子带的判决准则如下(这里以第一个子带组为例)
若
Figure PCTCN2018116144-appb-000038
则认为该子带组的激活的子带为第1个子带，同时根据S2中的调制规定，可以判定该子带组对应传输的符号中
Figure PCTCN2018116144-appb-000039
若
Figure PCTCN2018116144-appb-000040
则认为该子带组的激活的子带为第2个子带，同 时根据S2中的调制规定，可以判定该子带组对应传输的符号中
Figure PCTCN2018116144-appb-000041
S7、激活子带解调。根据S6的检测结果确定激活的子带序号k，对该子带进行符号解调。这里利用最大合并比准则，对L条路径的峰值进行合并处理并进行符号判决
Figure PCTCN2018116144-appb-000042
而后进行BPSK符号解映射
Figure PCTCN2018116144-appb-000043
自此，完成一个子带组的解扩，获得该子带组传输的2个符号b 11b 12的解调。其余子带组依此处理。
本发明将系统可用带宽划分为多个子带，进行数据传输，提高了整个系统的频带利用率。通过选择激活子带的方式，在传输同样多数据的前提下，节省了系统能量消耗。由图5的误比特率仿真图也可知，本实施方案在信号发生多普勒扩展之后，依旧可以在较低信噪比SNR下，保持较好的误码率BER性能，并且通过选择激活子载波的方式，降低能量损耗以及相邻载波间的干扰。

Claims (7)

  1. 一种基于子带选择激活的多带双曲调频扩频水声通信方法，其特征在于包括以下步骤：
    S1、将通信系统带宽分为多个子带，分别进行双曲调频；
    S2、数据、子带进行分组，确定子带激活方案，并进行信号调制；
    S3、对完成调制的信号添加帧头；
    S4、接收端对接收信号进行预处理，同步，信道估计；
    S5、计算子带检测与解调所需要的相关值；
    S6、激活子带检测；
    S7、激活子带解调。
  2. 根据权利要求1所述的一种基于子带选择激活的多带双曲调频扩频水声通信方法，其特征在于：在所述步骤S1中，将系统可用带宽B＝f 1-f 0，即最高频率f 1与最低频率f 0的差，分为K个子带，K的值为2的整数倍；每个子带带宽为
    Figure PCTCN2018116144-appb-100001
    分别对每个子带进行双曲调频，调频周期为T，后续用于扩频调制；第k(1≤k≤K)个子带对应的双曲调频信号为：
    Figure PCTCN2018116144-appb-100002
    其中
    Figure PCTCN2018116144-appb-100003
  3. 根据权利要求1所述的一种基于子带选择激活的多带双曲调频扩频水声通信方法，其特征在于：在所述步骤S2中，数据、子带进行分组，分组具体为：
    将每K个比特分成Q个数据组，Q的取值为子带个数除以2，即
    Figure PCTCN2018116144-appb-100004
    同时 将K个子带也分成Q个子带组，每个数据组与每个子带组对应构成一组，这里分组的结果为，每组2个子带传输2个比特。
  4. 根据权利要求1所述的一种基于子带选择激活的多带双曲调频扩频水声通信方法，其特征在于：在所述步骤S2中，确定子带激活方案并进行信号调制具体为：
    每组2个比特中的第1个比特为0时，激活每组的第1个子带进行传输，当该比特为1时激活该组第2个子带进行传输；
    每组2个比特中的第2个比特则采用BPSK符号映射，对该激活的子带载波信号进行调制；
    记第j(j＝1,…,Q)组的2个比特为b j1b j2，则当前多带双曲调频扩频符号帧的发送信号表示为
    Figure PCTCN2018116144-appb-100005
    其中k j＝2j+b j1-1为第j组激活的子带编号，上式中2b j2-1表示对第j组的第2个比特则采用BPSK符号映射。
  5. 根据权利要求1所述的一种基于子带选择激活的多带双曲调频扩频水声通信方法，其特征在于：在所述步骤S5中，子带检测与解调所需要的相关量运算，实现流程如下：
    S51、计算相关峰值偏移量，假设步骤S4信道估计结果为：多径数为L条，每条路径对应的参数为时延
    Figure PCTCN2018116144-appb-100006
    多普勒因子
    Figure PCTCN2018116144-appb-100007
    计算第k个子带，第m个符号，第l条路径的峰值偏移量
    Figure PCTCN2018116144-appb-100008
    其中N为一个双曲调频符号的点数；f s为信号采样率，
    Figure PCTCN2018116144-appb-100009
    为多普勒扩展导 致的偏置，f k0表示第k个子带的起始频率，
    Figure PCTCN2018116144-appb-100010
    为经过多普勒扩展补偿后一个双曲调频符号的点数；
    S52、进行相关运算，获取峰值；根据Δn k,m,l，分别用每个子带与接收信号对应位置进行相关运算获得峰值；第k个子带，第m个符号，第l条路径的峰值I k,m,l表示为
    Figure PCTCN2018116144-appb-100011
    其中x k[n]与为第k子带的扩频符号，r[n]代表接收端的信号。
  6. 根据权利要求5所述的一种基于子带选择激活的多带双曲调频扩频水声通信方法，其特征在于：在S6中，令j＝1,…,Q，第j组激活子带的检测具体包括：
    若
    Figure PCTCN2018116144-appb-100012
    则认为该子带组的第1个子带为激活子带，同时根据S2中的调制规定，可以判定该子带组对应传输的符号中
    Figure PCTCN2018116144-appb-100013
    激活子带编号为k j＝2j-1；
    若
    Figure PCTCN2018116144-appb-100014
    则认为该子带组的第2个子带为激活子带，同时根据S2中的调制规定，能判定该子带组对应传输的符号中
    Figure PCTCN2018116144-appb-100015
    激活子带编号为k j＝2j。
  7. 根据权利要求1所述的一种基于子带选择激活的多带双曲调频扩频水声通信方法，其特征在于：在S7中，令j＝1,…,Q，第j组激活子带上传输符号解调的具体实现如下：利用最大合并比准则，对L条路径的相关峰值进行合并处理并进行符号判决
    Figure PCTCN2018116144-appb-100016
    其中
    Figure PCTCN2018116144-appb-100017
    是第l条路径估计的幅度，而后进行BPSK符号解映射，即
    Figure PCTCN2018116144-appb-100018
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US11463178B2 (en) 2017-11-22 2022-10-04 South China University Of Technology Sub-band selection activation-based multi-band hyperbolic frequency modulation spread spectrum underwater acoustic communication method
CN115022139A (zh) * 2022-05-27 2022-09-06 中国人民解放军63921部队 一种基于双曲调频信号的相位预调制方法及系统
CN117792849A (zh) * 2022-09-27 2024-03-29 中国科学院声学研究所 一种基于频域均衡的gmsk水声通信方法及系统

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