Underwater acoustic communication system based on filter bank joint sub-carrier multidimensional index modulation and method thereof

Abstract

Disclosed is an underwater acoustic communication system based on a filter bank joint sub-carrier multidimensional index modulation and a method thereof. The system includes a transmitting terminal and a receiving terminal, the method is: conducting a joint index modulation at the transmitting terminal, firstly selecting an activated prototype pulse index by using a part of bits of a FBMC symbol, grouping the remaining transmitted information bits and all sub-carriers; using a part of the bits in each group to select the activated sub-carrier index, modulating the remaining bits to the activated sub-carriers by a constellation symbol mapping, forming a transmission signal after a filter bank modulation; and demodulating three parts of transmitted bits at a receiving terminal after an action of underwater acoustic channel, and recovering the original data bits by combining each part of decoding results.

Claims

1. An underwater acoustic communication system based on a filter bank joint sub-carrier multidimensional index modulation, comprising a transmitting terminal and a receiving terminal; the transmitting terminal includes a prototype pulse index module, a bit shunt, a carrier state index module, a constellation mapping module, a Filter bank multi-carrier (FBMC) block generator and a filter bank modulation module; the receiving terminal includes an equalizer, a detector, a decoder and a bit combiner; bit input signals are taken as input signals of the prototype pulse index module and input signals of the bit shunt, respectively; output signals of the prototype pulse index module are transmitted to the filter bank modulation module; output signals of the bit shunt are transmitted to the carrier state index module and the constellation mapping module, respectively; output signals of the carrier state index module and output signals of the constellation mapping module are all transmitted to the FBMC block generator; output signals of the FBMC block generator are transmitted to the filter bank modulation module; output signals of the filter bank modulation module are taken as output signals of the transmitting terminal; and the output signals of the transmitting terminal are taken as input signals of the equalizer; output signals of the equalizer are transmitted to the detector; output signals of the detector are transmitted to the decoder, output signals of the decoder are transmitted to the bit combiner, and output signals of the bit combiner are taken as output signals of the receiving terminal.

2. The underwater acoustic communication system based on the filter bank joint sub-carrier multidimensional index modulation according to claim 1, wherein the detector includes a prototype pulse detection module, a sub-carrier basis function module, a FBMC block classifier, a carrier state detection module, and a symbol detection module; the decoder includes a filter index decoding module, a sub-carrier index decoding module and a constellation symbol decoding module; and the output signals of the equalizer are transmitted to the prototype pulse detection module, output signals of the prototype pulse detection module are transmitted to the sub-carrier basis function module; output signals of the sub-carrier basis function module are transmitted to the FBMC block classifier and the filter index decoding module, respectively; output signals of the FBMC block classifier are transmitted to the carrier state detection module; output signals of the carrier state detection module are transmitted to the symbol detection module; output signals of the symbol detection module are transmitted to the sub-carrier index decoding module and the constellation symbol decoding module, respectively; and output signals of the sub-carrier index decoding module, output signals of the constellation symbol decoding module and output signals of the filter index decoding module are all transmitted to the bit combiner.

3. A communication method for the underwater acoustic communication system based on the filter bank joint sub-carrier multidimensional index modulation according to claim 1, comprising a transmitting method and a receiving method; wherein steps of the transmitting method are that: Step 1, selecting, by a part of bits in a transmitted binary bit stream, an activated prototype pulse index, evenly grouping, through a bit shunt and all sub-carriers, remaining bits, selecting, by a part of bits in each group, an activated sub-carrier index, mapping, after a quadrature amplitude modulation, the part of bits to activated sub-carriers, and forming complete transmission data by each group of data after passing through a FBMC block generator; and Step 2, interleaving, for a 1/2 period, a real part and an imaginary part of a mapped complex constellation symbol with each other, conducting, through a filter selected by the prototype pulse index in the Step 1, a filter bank multi-carrier modulation, forming transmission signals and sending the transmission signals into an underwater acoustic channel for transmission; and steps of the receiving method are that: Step 3, demodulating and decoding, at a receiving terminal, received symbols after a channel equalization, and eventually combining outputs to restore an original transmitted binary bit stream.

4. The communication method for the underwater acoustic communication system based on the filter bank joint sub-carrier multidimensional index modulation according to claim 3, in the Step 1, a total number of the sub-carriers M and a total number of input bits A in a system are determined according to communication requirements, wherein p.sub.1 bits are for selecting an activated filter prototype pulse index, and remaining B bit information is divided into G groups through the bit shunt and the sub-carriers, bit information p=p.sub.2+p.sub.3 in each group is mapped to a sub-carrier group with a length of K, A=p.sub.1+B=p.sub.1+(p.sub.2+p.sub.3)G, G=M/K=B/p; only L sub-carriers in each group are activated for transmitting a constellation symbol, and remaining silent sub-carriers are zeroed, p.sub.2 bits are for select the activated sub-carriers index, and p.sub.3 bits are modulated to active sub-carriers after being formed into a complex symbol through a constellation mapping.

5. The communication method for the underwater acoustic communication system based on the filter bank joint sub-carrier multidimensional index modulation according to claim 4, wherein each part of the bits are p.sub.1=log.sub.2 N.sub.f, p.sub.2=log.sub.2 C.sub.K.sup.L, p.sub.3=L log.sub.2Q, where represents a floor function, that is a bit number of p.sub.1 depends on all alternative prototype filter types N.sub.f, a bit number of p.sub.2 depends on all possible sub-carrier combinations C.sub.K.sup.L, a bit number of p.sub.3 depends on a number L of the active sub-carriers in each group and a modulation dimension Q of the constellation mapping.

6. The communication method for the underwater acoustic communication system based on the filter bank joint sub-carrier multidimensional index modulation according to claim 4, wherein the p.sub.1 bits are output as an activated filter serial number F.sub.H [1,2,K,N.sub.f] of a n-th FBMC symbol after passing through the prototype pulse index module; the p.sub.2 bits are output as an activated sub-carrier serial number I.sub.g={i.sub.g,1,i.sub.g,2,K, i.sub.g,L}, i.sub.g,l[1,2,L,K], g=1,K,G and l=1,K,L after passing through the carrier state index module; and the p.sub.3 bits are output as L symbols s.sub.g={s.sub.g,1,s.sub.g,2,K,s.sub.g,L}, s.sub.g,l, g=1,K,G and l=1,K,L after the constellation mapping, where represents a Q-dimensional constellation set.

7. The communication method for the underwater acoustic communication system based on the filter bank joint sub-carrier multidimensional index modulation according to claim 3, wherein output data for the FBMC block generator in the Step 1 are x=[x(0),K,x (M1)], x(m){0,} and m=0,K,M1.

8. The communication method for the underwater acoustic communication system based on the filter bank joint sub-carrier multidimensional index modulation according to claim 3, wherein composite index modulated transmission signals modulated by a basis function g.sub.n(t) of a No. F.sub.n filter in the Step 2 are represented as $s\left(t\right)=\underset{m=0}{\overset{M-1}{.Math.}}\underset{n=0}{\overset{+}{.Math.}}{e}^{j2\mathrm{mvt}}{e}^{j{}_{m,n}}\left\{a_{m,n}{g}_n\left(t-\mathrm{nT}\right)+{\mathrm{jb}}_{m,n}{g}_n\left(t-\frac{T}{2}-\mathrm{nT}\right)\right\},$ where an additional phase is ${}_{m,n}=\frac{}{2}m,$ a sub-carrier interval v and a symbol period T satisfy v=1/T, a.sub.m,n and b.sub.m,n are a real part and an imaginary part of x(m), a part of a.sub.m,n and b.sub.m,n are capable of being 0 because of an introduction of the silent sub-carriers.

9. The communication method for the underwater acoustic communication system based on the filter bank joint sub-carrier multidimensional index modulation according to claim 3, wherein in Step 3, an equalization result y of received signals is sent to the detector, and a detection process is divided into following steps: Step 1, conducting a prototype pulse detection, determining, by a maximum likelihood detection, filter bank basic function index information {circumflex over (F)}.sub.n, and conducting a filter bank demodulation on ; Step 2, obtaining, through a FBMC block classifier, each group of the received signals y.sub.1y.sub.G; and Step 3, conducting, by grouping, a sub-carrier state detection, determining, by a maximum likelihood criterion, active sub-carrier index information .sub.g in each group, and taking data symbols carried on active sub-carriers as a constellation symbol .sub.g to be decoded at the same time.

10. The communication method for the underwater acoustic communication system based on the filter bank joint sub-carrier multidimensional index modulation according to claim 3, in Step 3, {circumflex over (F)}.sub.n, .sub.g and .sub.g are inputted to the filter index decoding module, the sub-carrier index decoding module and the constellation symbol decoding module respectively to obtain corresponding bits, the corresponding bits are combined through the bit combiner to obtain a restored transmitted bit stream.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates a schematic diagram of a filter bank joint sub-carrier multidimensional index modulation method.

(2) FIG. 2 illustrates a block diagram of a transmitting terminal in an underwater acoustic communication system based on a filter bank joint sub-carrier multidimensional index modulation.

(3) FIG. 3 illustrates a block diagram of a receiving terminal in the underwater acoustic communication system based on the filter bank joint sub-carrier multidimensional index modulation.

(4) FIG. 4 illustrates a communication mode of a traditional communication system with spectrum interferences in one embodiment of the present disclosure.

(5) FIG. 5 illustrates an anti-interference communication mode after sub-carrier index modulation in one embodiment of the present disclosure.

(6) FIG. 6 illustrates is a schematic diagram of a matching of prototype pulses and channel expansion characteristics in one embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(7) In order to further clarify the objectives, the technical solutions and the advantages of the embodiments in the present disclosure, the technical solutions in the embodiments of the present disclosure will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present disclosure, and it will be apparent that the described embodiments are some, but not all embodiments of the present disclosure. Based on the embodiments of the present disclosure, all other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present disclosure.

(8) Provided is an underwater acoustic communication system based on a filter bank joint sub-carrier multidimensional index modulation and a method thereof. As illustrated in FIG. 1, the multi-dimensional index modulation method disclosed in the present disclosure combines the prototype pulse index mapping of the filter bank and the sub-carrier state index mapping, which is an index modulation with a combination of the spatial domain and the frequency domain. The communication system includes a transmitting terminal and a receiving terminal.

(9) As illustrated in FIG. 2, the transmitting terminal includes a prototype pulse index module, a bit shunt, a carrier state index module, a constellation mapping module, a FBMC block generator and a filter bank modulation module. A total number of the sub-carriers M and a total number of input bits A in a system are determined according to communication requirements.

(10) The binary bit stream has p.sub.1 bits, which are for selecting the activated filter prototype pulse index, where p.sub.1=log.sub.2 N.sub.f, and represents a floor function, that is the bit number of the p.sub.1 depends on all alternative prototype filter types N.sub.f. The p.sub.1 bits are output as an activated filter serial number F.sub.n[1,2,K,N.sub.f] of a n-th FBMC symbol after passing through the prototype pulse index module.

(11) The remaining B bit information is evenly divided into G groups through the bit shunt and the sub-carriers, bit information p=p.sub.2+p.sub.3 in each group is mapped to a sub-carrier group with a length of K, A=p.sub.1+B=p.sub.1+(p.sub.2+p.sub.3)G, G=M/K=B/p; only L sub-carriers in each group are activated for transmitting a constellation symbol, and remaining silent sub-carriers are zeroed, p.sub.2 bits are for selecting the activated sub-carriers index, and p.sub.3 bits are modulated to active sub-carriers after being formed into the complex symbols through a constellation mapping. p.sub.2=log.sub.2 C.sub.K.sup.L and p.sub.3=L log.sub.2 Q, where the bit number of p.sub.2 depends on all possible sub-carrier combinations C.sub.K.sup.L, the bit number of p.sub.3 depends on the number L of the active sub-carriers in each group and a modulation dimension Q of the constellation mapping. The p.sub.2 bits are output as an activated sub-carrier serial number I.sub.g={i.sub.g,1,i.sub.g,2,K,i.sub.g,L}, i.sub.g,l[1,2,L,K], g=1,L,G and l=1,K,L after passing through the carrier state index module. The p.sub.3 bits are output as L symbols s.sub.g={s.sub.g,1,s.sub.g,2K,s.sub.g,L}, s.sub.g,l, g=1,K,G and l=1K,L after the constellation mapping, where represents a Q-dimensional constellation set

(12) TABLE-US-00001 TABLE 1 A table of the prototype pulse index mapping when N.sub.f = 4 in the embodiments of the present disclosure p.sub.1 F.sub.n Prototype pulse 00 1 PHYDYAS filter 01 2 EGF filter ( < 1 ) 10 3 IOAT filter 11 4 EGF filter ( > 1 )

(13) TABLE-US-00002 TABLE 2 A table of the carrier state index mapping when C.sub.K.sup.L = C.sub.4.sup.2 in the embodiments of the present disclosure Combination serial number p.sub.2 I.sub.g Carrier states C.sub.1 00 {1, 2} [s.sub.g,1, s.sub.g,2, 0, 0].sup.T C.sub.2 01 {1, 3} [s.sub.g,1, 0, s.sub.g,2, 0].sup.T C.sub.3 10 {1, 4} [s.sub.g,1, 0, 0, s.sub.g,2].sup.T C.sub.4 11 {2, 3} [0, s.sub.g,1, s.sub.g,2, 0].sup.T C.sub.5 [0, s.sub.g,1, 0, s.sub.g,2].sup.T C.sub.6 [0, 0, s.sub.g,1, s.sub.g,2].sup.T

(14) Considering the prototype pulse index mapping N.sub.f=4 as shown in Table 1 and the carrier state index mapping situation N.sub.f=4 as shown in Table 2 (selecting C.sub.1C.sub.4 from six types of the carrier combinations), each FBMC symbol contains M=512 sub-carriers and the constellation symbol adopts the 4QAM modulation. At this time, p.sub.1=2, p.sub.2=2, p.sub.3=4 and G=128, which is capable of calculating that 770 bit information is needed to be transmitted to generate one FBMC symbol by the transmitting terminal.

(15) Output data for the FBMC block generator is x= [x(0),K,x(M1)], x(m)={0,} and m=0,K,M1. Composite index modulated transmission signals modulated by a basis function g.sub.n(t) of a No. F.sub.n filter are represented as

(16) $s\left(t\right)=\underset{m=0}{\overset{M-1}{.Math.}}\underset{n=0}{\overset{+}{.Math.}}{e}^{j2\mathrm{mvt}}{e}^{j{}_{m,n}}\left\{a_{m,n}{g}_n\left(t-\mathrm{nT}\right)+{\mathrm{jb}}_{m,n}{g}_n\left(t-\frac{T}{2}-\mathrm{nT}\right)\right\},$
where an additional phase is

(17) ${}_{m,n}=\frac{}{2}m,$
a sub-carrier interval v and a symbol period T satisfy v=1/T, a.sub.m,n and b.sub.m,n are a real part and an imaginary part of x(m), a part of a.sub.m,n and b.sub.m,n are capable of being 0 because of an introduction of the silent sub-carriers.

(18) As illustrated in FIG. 3, the receiving terminal includes an equalizer, a detector, a FBMC block classifier, a decoder and a bit combiner. The detector includes a prototype pulse detection module, a sub-carrier basis function module, a carrier state detection module, and a symbol detection module. The decoder includes a filter index decoding module, a sub-carrier index decoding module and a constellation symbol decoding module. An equalization result y of received signals is sent to the detector at the receiving terminal. Firstly, a prototype pulse detection is conducted, and filter bank basic function index information {circumflex over (F)}.sub.n is determined by a maximum likelihood detection,

(19) $\left\{{\hat{F}}_n\right\}=\arg \underset{g_n}{\min }{.Math.\stackrel{\_}{y}-x*g_n.Math.}^2,$
where is a set of N.sub.f prototype filter bank basis functions. A demodulation is conducted on y by a {circumflex over (F)}.sub.n analysis filter bank to obtain y. Each group of the received signals y.sub.1y.sub.G is obtained through a FBMC block classifier. A sub-carrier state detection is conducted by grouping. Active sub-carrier index information .sub.g in each group is determined by a maximum likelihood criterion. The carried symbols have values of 0 and non-0 are considered by the maximum likelihood detection, and the index position is determined by comparing the posterior probability. L sub-carriers with a higher posterior probability are determined as activated sub-carriers, and the remaining sub-carriers are silent sub-carriers. Data symbols carried on the active sub-carriers are taken as a constellation symbol .sub.g to be decoded at the same time.

(20) {circumflex over (F)}.sub.n, .sub.g and .sub.g are transmitted to the filter index decoding module, the sub-carrier index decoding module and the constellation symbol decoding module respectively to obtain corresponding bits, the corresponding bits are combined through the bit combiner to obtain a restored transmitted bit stream.

(21) In the embodiments of the present disclosure, the communication scenario with multi-band narrowband interference is further considered as illustrated in FIG. 4, the unprocessed communication signals overlap with the spectrum of the interference signals, which causes interference and reduces the quality of the communication. As illustrated in FIG. 5, a multi-band narrowband interference avoidance is capable of being implemented by using the sub-carrier index modulation, which improves the effectiveness and reliability of the underwater acoustic communication. The filter bank prototype pulse adaptation is further considered as illustrated in FIG. 6, so that the dispersion characteristics of the current filter bank pulse cover the dispersion characteristics of the current underwater acoustic channel. To sum up, the underwater acoustic communication system based on the filter bank joint sub-carrier multidimensional index modulation adopted by the present disclosure has a great improvement on the performance thereof.

(22) Although the embodiments of the present disclosure are described in combination with the drawings, for a person skilled in the art, some modifications and variations can be made without departing from the concept of the present disclosure, which are all within the protection scope of the present disclosure.