CN107623653B - Four-dimensional wireless communication method combining frequency spectrum and space point focusing wave transmission - Google Patents
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Abstract
The invention provides a four-dimensional wireless communication method combining frequency spectrum and space point focused wave transmission, which is used for meeting the requirement of high-capacity ultrahigh-speed communication and belongs to the technical field of wireless communication. The method uses one-dimensional frequency spectrum resources and three-dimensional space resources to simultaneously carry digital information: on a frequency domain, carrying digital information by utilizing an OFDM orthogonal subcarrier frequency spectrum; on a space domain, generating three-dimensional space position carrying digital information of a focused spot by using a time reversal signal; compared with the traditional communication system, the four-dimensional wireless communication technology fully utilizes space domain resources, not only utilizes the time reversal technology to generate space diversity to increase channel capacity on a fixed frequency spectrum, but also can transmit information through the space position of the base station antenna array element, and has great technical advantages in the aspects of improving the utilization rate of the frequency spectrum resources, the system capacity and the wireless communication speed.
Description
Technical Field
The invention belongs to the technical field of wireless communication, and particularly relates to a four-dimensional wireless communication method for combining frequency spectrum and space point focused wave transmission.
Background
From 2G communication to 5G communication, mobile communication has been developed from simple transmission of voice information to pictures, videos, and the like, and with the arrival of the big data era, the amount of information that various communication devices need to transmit is increasing dramatically, and the requirements for wireless communication rate and channel capacity are also increasing. However, due to the limited physical bandwidth of electronic devices and the limited spectrum resources due to the regulations for allocating Communication spectrum in various countries, attempts have been made to apply new frequency bands for wireless Communication, such as the documents "Wolfgang gerstar, Josep Miquel joint. The terahertz communication is mentioned, the radio frequency communication frequency is expanded to a terahertz frequency band, but the terahertz communication has the problems of low radiation power, serious atmospheric attenuation, difficult modulation and demodulation and the like and is difficult to apply. Therefore, it is difficult to implement a scheme that improves the performance of a wireless communication system such as a data transmission rate and a spectrum utilization rate by simply spreading the spectrum width. Therefore, searching for a new wireless communication scheme based on the existing spectrum resources has become an important research subject in the wireless communication field.
The ofdm (orthogonal Frequency Division multiplexing) technology is a multi-carrier modulation technology that improves the spectrum utilization efficiency on the existing spectrum resources. The main idea of OFDM technology is to divide a given channel into many orthogonal sub-channels in the frequency domain, to modulate with one sub-carrier on each sub-channel, and to transmit the sub-carriers in parallel. Because the carriers of each sub-channel are orthogonal in the OFDM system, the frequency spectrums of the carriers are mutually overlapped, so that the mutual interference among the sub-carriers is reduced, and the frequency spectrum utilization rate is greatly improved. Since this technique has the capability of transmitting signals under clutter interference, it is often used in a transmission environment that is easily interfered by or has poor capability of resisting external interference, and is a frequency domain modulation technique widely applied in the frequency domain. In recent years, the rapidly developed mimo (Multiple Input and Multiple output) technology has attracted more attention to the development and utilization of spatial domain resources. The spatial multiplexing technique is a MIMO technique that can increase system throughput by transmitting and receiving through paired transmit and receive antennas without increasing bandwidth and transmit power. G. shell Layered Space-Time Architecture (BLAST) proposed by fosschini is a technique of coding in both spatial and temporal dimensions, which is one of the Space-Time codes; as described in the literature "V-BLAST: a vertical layered space-time coding (V-BLAST) method proposed in the innovative Symposium on Signals, Systems, and Electronics, 1998.295-300, p.wolnianky, g.fosschii, g.golden and r.valenzelela. The BLAST coding is to divide the data stream to be transmitted into Nt sub-data streams, and then to transmit these sub-data streams by using different antennas, so as to realize simultaneous transmission of multiple data streams, effectively improve the transmission rate of the system, and improve the spectrum utilization rate without increasing the system bandwidth. For example, the document "Shixin, Lihao. wireless MIMO-OFDM communication system principle and its key technology [ J ]. foreign electronic measurement technology, 2010, (02): 32-35' narrow beams are formed in space by mainly utilizing beam forming technology, and space resource utilization of limited frequency spectrum is realized. However, the narrow beam belongs to a fan beam, and occupies a very large space resource, that is, the space resource utilization efficiency is not high, and it is difficult to further improve the space resource utilization efficiency. And the coding and decoding are complex, and the system is difficult to realize.
In recent years, researchers have attempted to combine digital wireless communication with transmit antennas, and proposed a new scheme for digital wireless communication systems, namely Spatial Modulation (SM) Technology, such as the literature "Spatial Modulation" (IEEE Transactions on.2008: 2228-. Spatial Modulation is a novel application form of multi-antenna transmission technology, and is different from Modulation modes such as traditional multi-Phase Shift Keying (MPSK) and multi-Quadrature Amplitude Modulation (MQAM) which map a certain number of information bits to a constellation point on a two-dimensional signal space, and the SM increases spatial dimension on the basis of the traditional Modulation modes, namely, the spatial position is used as an information source to transmit information, so that a three-dimensional constellation diagram is constructed. Because SM introduces the space domain into the modulation category, increases the modulation degree of freedom, and utilizes the index of the transmitting antenna to transmit a part of information, the information transmission rate and the frequency spectrum utilization rate are improved, and the system capacity is enlarged. However, in each working period, because only one antenna works at the system transmitting end and other antennas are in an idle state, although mutual interference among the antennas is effectively avoided and the number of radio frequency modules is also reduced, obviously, the utilization efficiency of the antennas is low, and the effect of improving various performances of a communication system is very limited.
The patent "a 2D-SPM digital wireless communication method based on time reversal electromagnetic wave lattice focusing CN 105827288A" proposes a two-dimensional spatial position modulation (2D-SPM) digital wireless communication method based on time reversal electromagnetic wave lattice focusing, the method combines the antenna array technology and the space-time 'punctiform' focusing principle of TR electromagnetic waves, at the system transmitting end, the multi-channel binary bit sequence to be transmitted is 'mapped' to a plurality of TR carriers corresponding to the array antenna in parallel, and the parallel two-dimensional spatial position modulation of the multi-channel binary digital signals is realized; at a receiving end of the system, based on a TR electromagnetic wave focusing transmission mechanism, a synchronous focusing dot matrix is formed at an expected two-dimensional grid point position, the demodulation of 2D-SPM information is realized by observing the existence of a focusing point at each grid point position by adopting a signal peak intensity judgment criterion, and the method effectively utilizes space domain resources but does not fully utilize frequency spectrum resources.
Through research on the existing literature and patent technologies, it can be found that the utilization of space resources is the most effective technical approach for solving the contradiction between the shortage of spectrum resources and the system capacity. By utilizing spatial resources, the capacity of the wireless communication system can be remarkably improved, such as technologies of MIMO-OFDM, SM, 2D-SPM and the like. However, these techniques fail to fully utilize three-dimensional space resources to increase the communication capacity of the wireless communication system. Although the beamforming technique of MIMO-OFDM can improve the spatial utilization of the spectrum resources. However, because the fan-shaped wave beam occupies a larger space area, the actual space utilization rate of the frequency spectrum resource is improved to a limited extent; compared with the MIMO-OFDM technology, the two-dimensional spatial position modulation (2D-SPM) digital wireless communication method has higher spatial utilization rate on spectrum resources, and can limit a spatial field in a point-shaped focus area through a time reversal point focusing technology, and the spectrum resources can be reused outside the focus area, so that the spatial utilization rate of the spectrum resources is greatly improved. However, the 2D-SPM only uses two-dimensional spatial resources and does not fully use three-dimensional spatial resources, and the transmission signal of the 2D-SPM is a pulse signal having a continuous spectrum, and the efficiency of spectrum utilization is lower in the frequency domain than the OFDM technique.
Disclosure of Invention
To solve the above problems in the prior art, it is an object of the present invention to provide a four-dimensional wireless communication method combining spectrum and spatial point focused wave transmission, which uses one-dimensional spectrum resources and three-dimensional spatial resources to simultaneously carry digital information. On a frequency domain, carrying digital information by utilizing an OFDM orthogonal subcarrier frequency spectrum; and on a space domain, generating a three-dimensional space position carrying digital information of a focused spot by using a time reversal signal.
The technical problem proposed by the invention is solved as follows:
a four-dimensional wireless communication method for combining spectrum and space point focused wave transmission comprises the following steps:
setting the volume of a communication area as V and a curved surface as S, wherein a base station antenna array is composed of M array element antennas, and the array element interval is set according to a space sampling law and is arranged on the curved surface S; the terminal antenna array is composed of N array element antennas (N is more than or equal to 2), is deployed in a three-dimensional space lattice form and is positioned in a communication area V;
the method comprises the following steps:
generating an OFDM signal: the OFDM signal to be generated in this step contains N1Sub-carriers of which there are M1Converting a serial bit stream b to be transmitted into two parallel bit streams by a serial-to-parallel converter for frequency domain modulation subcarriers, wherein the two parallel bit streams are respectively the bit streams b for frequency domain modulationfAnd a bit stream b with spatial modulationsWherein the bit stream bsNumber of bits of N1Bit stream bfHas a bit number of 2M1A bit stream bfQPSK modulation is carried out to obtain a frequency domain modulation signal constellation diagram and obtain a group of parallel data streams d0，
Through N1Sub-carriers
Carrying out carrier modulation to obtain an OFDM signal p (t) carrying frequency domain information;
step two: wireless channel detection: the ith (i is 1, … N) array element in the terminal antenna array transmits channel detection signal, i.e. OFDM signal p (t) carrying frequency domain information, and the jth (j is 1, … M) array element in the base station antenna array receives channel detection response yji(t); for channel sounding response yji(t) time reversal processing is carried out to obtain a time reversal signal y of channel detection responseji(t), amIs Sji(t); the base station antenna array has M array elements, and the time reversal signals from the ith array element in the terminal antenna array to the channel detection response of each array element in the base station antenna array form a matrix S1，i(t)S2，i(t)…SM，i(t)]T；
The terminal antenna array has N array elements, each array element carries on the above-mentioned wireless channel detection process, then as the carrier after carrying on time reversal processing to the channel detection response, thus get the carrier matrix:
step three: the carrier matrix and the spatial domain serial bit stream b in the step one are combineds＝[bs1 bs2 … bsN]Multiplication:
wherein the elements in X (t)
Is a terminal antenna array transmitting a bit stream bsWhen the signal is modulated, the modulated signal waveform to be transmitted by the jth array element in the base station antenna array is modulated onto a carrier wave to realize space domain modulation, and the base station antenna array transmits the modulated signal;
step four: the ith array element antenna in the terminal antenna array receives signals, and the peak value A of each array element receiving signal is obtained after signal peak value detectioniThen, the peak value of the signal is compared, and the maximum value of the peak value of the signal is taken as AmaxNormalizing the peak value of the received signal; receiving peak value A of signal from each array element of terminal antenna arrayiAre all reacted with AmaxDividing to obtain corresponding normalized signal peak value
Step five: root of herbaceous plantAccording to the decision rule: when etaiWhen the judgment threshold is greater than the rho, judging the judgment threshold as 1, otherwise, judging the judgment threshold as 0, namely:
the decision threshold rho is a sampling statistic value obtained after a communication system is tested in a fixed environment; recovering transmitted binary symbols, i.e. parallel spatial information bsr(ii) a Parallel spatial domain information bsrConversion into a serial bit information stream bs1；
Step six: time domain signals received by each antenna array element in the terminal antenna array all carry the same frequency domain information, so that time domain signals received by any array element in the terminal antenna array can be subjected to time reversal processing, and then fast Fourier transform is carried out; here, the first array element is selected to obtain frequency domain data symbol y (k) ( k 1, 2, 3.. M)1) Then, obtaining a constellation diagram of frequency domain information in the received signal through QPSK demodulation; demapping and recovering frequency domain serial bit information bfrSerial bit information of frequency domain bfrAnd spatial domain serial bit stream bs1Combined to generate a serial bit stream brAnd the transmission information is restored to realize four-dimensional digital wireless communication.
In free space, according to the diffraction limit theorem, the distance between two adjacent antenna array elements is larger than half wavelength, otherwise, focused spots are overlapped, and information demodulation is not facilitated. Meanwhile, the mutual coupling effect exists when the distance of the antenna array elements is less than half of the wavelength, in order to ensure the independence of the spatial positions of the array elements in the terminal antenna array and ensure that a receiving end can accurately demodulate the transmitted binary code elements, for the terminal antenna array in a free space environment, the distance between the adjacent array elements is more than half of the wavelength. In the strong scattering electromagnetic environment, the time reversal has a super-resolution characteristic, and the minimum array element interval of the terminal antenna array can be smaller than half of the working wavelength. However, due to different scattering environments and different time-reversal super-resolution distances, in order to reduce spatial overlapping of point focusing fields as much as possible and reduce spatial field crosstalk between adjacent array element antennas, the array element distance of the terminal antenna array can be set to be larger than the diameter of the time-reversal focusing field.
The invention has the beneficial effects that:
(1) compared with a sector narrow beam occupying large space resources by the MIMO-OFDM technology, the invention forms focusing at the receiving antenna, so that the antenna spacing can be smaller, and the space domain resources can be fully utilized;
(2) compared with the Space Modulation (SM) technology, the invention simultaneously utilizes a plurality of groups of antennas for receiving and transmitting, and the utilization efficiency of the antennas is higher;
(3) compared with a two-dimensional spatial position modulation (2D-SPM) digital wireless communication method, the method can realize the utilization of three-dimensional space resources;
(4) the invention also gives full play to the efficient utilization of frequency domain resources of the OFDM technology, and the channel capacity is far larger than that of a two-dimensional spatial position modulation (2D-SPM) digital wireless communication method;
(5) according to the invention, the space-time focusing characteristic due to time reversal is formed at the receiving antenna, each array element of the receiving antenna array can accurately receive corresponding digital information, and mutual interference among the information received by each array element is avoided, so that each array element can receive different information of the same frequency spectrum, the utilization rate of the frequency spectrum is greatly improved, and the information transmission capacity is greatly increased at a fixed frequency spectrum;
(6) the four-dimensional wireless communication technology simultaneously utilizes space resources to transmit wireless information by focusing the energy of the punctiform focal spot generated by the time reversal signal in a three-dimensional space, thereby realizing the parallel spatial transmission of the information;
(7) the sub-wavelength antenna array with super-resolution characteristic can be used as the array element antenna of the terminal antenna array, so that the diffraction limit can be broken through, the radius of the focusing spot can be further reduced, and the terminal antenna arrays can be arranged more densely. The spatial domain resource utilization rate is further increased in a limited space.
Drawings
FIG. 1 is a block diagram of a four-dimensional wireless communication method combining spectral and spatial point-focused wave transmission in accordance with the present invention;
fig. 2 is a structure diagram of a planar monopole antenna of the antenna array element of the present invention;
FIG. 3 is a schematic diagram of a four-dimensional wireless communication method combining spectrum and spatial point focused wave transmission according to the present invention;
FIG. 4 is a spatial energy focusing field diagram of a four-dimensional wireless communication method combining spectrum and spatial point focused wave transmission according to the present invention;
FIG. 5 is a constellation diagram after frequency domain information modulation according to an embodiment of the present invention;
fig. 6 is a waveform of an OFDM signal transmitted by a first array element of a terminal antenna array during channel sounding according to an embodiment of the present invention;
FIG. 7 is a waveform of an OFDM signal transmitted by a first array element of a base station antenna array when a sequence of symbols is transmitted according to an embodiment of the present invention;
FIG. 8 is a diagram illustrating the focusing time effect of the spatial domain communication electromagnetic wave according to an embodiment of the present invention;
fig. 9 is a constellation diagram for demodulation of the first array element of the terminal antenna array in the embodiment of the present invention.
Detailed Description
The invention is further described with reference to the following figures and specific examples.
The block diagram of the four-dimensional wireless communication system is shown in fig. 1, and the volume of a communication area is set as V, a curved surface is set as S, the communication area is a cubic free space, the origin of a coordinate system is taken as the center, and the side length is 9 x lambda (lambda represents the wavelength corresponding to the central working frequency of the free space); the base station antenna array and the terminal antenna array of this embodiment are both composed of a planar monopole antenna with a center frequency of 2.45GHz, the monopole antenna structure is shown in fig. 2, and the parameters are shown in the following table (unit: mm):
| W | W1 | W2 | W3 | W4 | L | L1 | L2 | L3 | L4 |
| 12 | 8 | 6 | 0.8 | 0.9 | 34 | 22 | 5.5 | 5 | 6 |
the base station antenna array is formed by arranging 56 array element antennas at equal intervals, the intervals among the 56 array element antennas are 8 lambda/3, the 56 array element antennas are distributed on six surfaces of a cube, the cube takes the origin of a coordinate system as the center, and the side length is 8 lambda; the terminal antenna array is composed of 27 array element antennas, is deployed in a three-dimensional space lattice mode, forms a 3 x 3 square antenna array with the origin of a coordinate system as the center, has array element intervals of lambda, and is deployed in a central area surrounded by the base station antenna array.
And the terminal antenna array is encoded from right to left and from bottom to top. The schematic perspective structure of the base station antenna array and the terminal antenna array is shown in fig. 3. The spatial energy focusing field diagram of the four-dimensional wireless communication method combining the frequency spectrum and the spatial point focusing wave transmission provided by the invention is shown in fig. 4.
The OFDM signal parameters applied in this embodiment are set as follows, with the number of subcarriers being N164 (16 of them are virtual subcarriers), the number of subcarriers for frequency domain information modulation is M148. The bandwidth of the signal is B-20 MHz, the frequency interval between carriers is 0.3125MHz, the length Nc of the cyclic prefix is 16, the total length of the OFDM symbol is 4 μ s, the transmission rate of the system is 24mbps (qpsk), and the channel is a gaussian additive white noise channel.
The method comprises the following steps: converting a serial bit stream b to be transmitted into two parallel bit streams by using a serial-to-parallel converter, wherein the two parallel bit streams are respectively bit streams b subjected to frequency domain modulationfAnd a bit stream b with spatial modulationsA bit stream bfQPSK modulation is performed to obtain a frequency domain modulation signal constellation diagram, as shown in FIG. 5, a bit stream bfHas a bit number of 96, resulting in a set of parallel data streams d0，d1，…，d47Passes through 64 sub-carriers f0，f1...f65Carrying out carrier modulation to obtain an OFDM signal p (t) carrying frequency domain information;
step two: wireless channel detection: the i (i ═ 1, …, 27) th array element in the terminal antenna array transmits a channel sounding signal, i.e. an OFDM signal p (t) carrying frequency domain information, as shown in fig. 6. The j (j is 1, …, 56) th array element in the base station antenna array receives the channel detection response yji(t); for channel sounding response yji(t) time reversal processing is carried out to obtain a time reversal signal y of channel detection responseji(-t) as Sji(t); the base station antenna array has 56 array elements, and the time reversal signals from the ith array element in the terminal antenna array to the channel detection response of each array element in the base station antenna array form a matrix S1，i(t)S2，i(t)…S56，i(t)]T；
The terminal antenna array has 27 array elements, each array element carries out the wireless channel detection process, and then the channel detection response is subjected to time reversal processing and then is used as a carrier, so that a carrier matrix is obtained:
step three: the carrier matrix and the spatial domain serial bit stream b in the step one are combineds＝[bs1 bs2 … bsN]Multiplication:
wherein the elements in X (t)
Is a terminal antenna array transmitting a bit stream bsWhen the signal is modulated, the modulated signal waveform to be transmitted by the jth array element in the base station antenna array is modulated onto a carrier wave to realize space domain modulation, and the base station antenna array transmits the modulated signal; fig. 7 shows a waveform of an OFDM signal to be transmitted by the 1 st element of the base station antenna array when transmitting a symbol sequence. Thus, binary information is modulated on a carrier, a base station antenna array is utilized to transmit modulated signals, electromagnetic wave focusing point distribution is obtained through simulation and is shown in figure 8, because the expected communication three-dimensional space is divided into a plurality of mutually independent blocks in the airspace to transmit airspace information, the electromagnetic wave focusing point distribution is compared with the code of a code element sequence according to the position numbering sequence, focusing points are found at the position of a terminal antenna array element corresponding to a code element '1', and no focusing point is found at the position of an array element corresponding to a code element '0', which indicates that electromagnetic field focusing point distribution consistent with the transmitted airspace code element sequence is obtained;
step four: the ith array element antenna in the terminal antenna array receives signals, and the peak value A of each array element receiving signal is obtained after signal peak value detectionmThe antenna array is characterized in a three-dimensional array form, and respectively corresponds to a plane formed by three 3 × 3 antenna arrays from top to bottom in the terminal antenna array:
comparing signal peak values, and taking the maximum value of the signal peak value as Amax1.74, normalizing the peak value of the received signal; receiving peak value A of signal from each array element of terminal antenna arrayiAre all reacted with AmaxDividing to obtain corresponding normalized signal peak value
Step five: according to the decision rule: when etaiIf the judgment threshold rho is greater than 0.5, the judgment is made as 1, otherwise, the judgment is made as 0, namely:
the decision threshold rho is 0.5, which is a sampling statistical value obtained after the communication system is tested in a fixed environment; recovering transmitted binary symbols, i.e. spatial information bsrComprises the following steps:
converting the recovered spatial three-dimensional matrix information (parallel information) into a serial bit information stream b in the order of spatial position numberss1；
Step six: time domain signals received by each antenna array element in the terminal antenna array all carry the same frequency domain information, so that the time domain signals received by any array element in the terminal antenna array can be subjected to fast Fourier transform; here, a first array element is selected to obtain a frequency domain data symbol y (k) ( k 1, 2.. multidot., 48), and then a constellation diagram of frequency domain information in a received signal is obtained through QPSK demodulation, as shown in fig. 9, comparing the constellation diagram information in fig. 5 and fig. 9 shows that the frequency domain information does not have too much distortion, so that the carried frequency domain information can be correctly demodulated; demapping and recovering frequency domain serial bit information bfrSerial bit information of frequency domain bfrAnd spatial domain serial bit stream bs1Combined to generate a serial bit stream brAnd the transmission information is restored to realize four-dimensional digital wireless communication.
Claims (3)
1. A four-dimensional wireless communication method combining spectrum and spatial point-focused wave transmission, comprising the steps of:
the base station antenna array is composed of M array element antennas, the array element interval is set according to the space sampling law and is deployed on the curved surface of the communication area; the terminal antenna array is composed of N array element antennas, is deployed in a three-dimensional space lattice form and is positioned in a communication area;
the method comprises the following steps: generating an OFDM signal: the OFDM signal to be generated in this step contains N1Sub-carriers of whichWith M1A sub-carrier wave for frequency domain modulation, a serial-to-parallel converter is adopted to convert the serial bit stream to be transmitted into two parallel bit streams, namely a bit stream b for frequency domain modulationfAnd a bit stream b with spatial modulationsWherein the bit stream bsNumber of bits of N1Bit stream bfHas a bit number of 2M1A bit stream bfQPSK modulation is carried out to obtain a frequency domain modulation signal constellation diagram, a group of parallel data streams are obtained, and N parallel data streams are processed1Carrying out carrier modulation on the subcarriers to obtain an OFDM signal p (t) carrying frequency domain information;
step two: wireless channel detection: the ith array element in the terminal antenna array transmits a channel detection signal, namely an OFDM signal p (t) carrying frequency domain information, wherein i is 1, … N, and the jth array element in the base station antenna array receives a channel detection response yji(t), wherein j is 1, … M; for channel sounding response yji(t) time reversal processing is carried out to obtain a time reversal signal y of channel detection responseji(-t) as Sji(t); the base station antenna array has M array elements, and the time reversal signals from the ith array element in the terminal antenna array to the channel detection response of each array element in the base station antenna array form a matrix S1，i(t)S2，i(t)…SM，i(t)]T；
The terminal antenna array has N array elements, each array element carries on the above-mentioned wireless channel detection process, then as the carrier after carrying on time reversal processing to the channel detection response, thus get the carrier matrix:
step three: the carrier matrix and the spatial domain serial bit stream b in the step one are combineds＝[bs1 bs2…bsN]Multiplication:
wherein the elements in X (t)
Is a terminal antenna array transmitting a bit stream bsWhen the signal is modulated, the modulated signal waveform to be transmitted by the jth array element in the base station antenna array is modulated onto a carrier wave to realize space domain modulation, and the base station antenna array transmits the modulated signal;
step four: the ith array element antenna in the terminal antenna array receives signals, and the peak value A of each array element receiving signal is obtained after signal peak value detectioniThen, the peak value of the signal is compared, and the maximum value of the peak value of the signal is taken as AmaxNormalizing the peak value of the received signal; receiving peak value A of signal from each array element of terminal antenna arrayiAre all reacted with AmaxDividing to obtain corresponding normalized signal peak value
Step five: according to the decision rule: when etaiWhen the judgment threshold is greater than the rho, judging the judgment threshold as 1, otherwise, judging the judgment threshold as 0, namely:
the decision threshold rho is a sampling statistic value obtained after a communication system is tested in a fixed environment; recovering the transmitted binary code elements, namely parallel space domain information; converting the parallel space domain information into a serial bit information stream according to the sequence of the spatial position numbers;
step six: time domain signals received by any array element in a terminal antenna array are subjected to time reversal processing, fast Fourier transform is carried out to obtain frequency domain data symbols, and then a constellation diagram of frequency domain information in the received signals is obtained through QPSK demodulation; de-mapping, recovering frequency domain serial bit information, combining the frequency domain serial bit information with space domain serial bit information flow to generate serial bit flow brReverting to emissionAnd information, and four-dimensional digital wireless communication is realized.
2. The method of claim 1, wherein adjacent array elements of the terminal antenna array are spaced apart by more than half a wavelength in free space.
3. The method of claim 1, wherein in a scattering environment, the array element spacing of the terminal antenna array is set to be larger than the diameter of the time-reversal focusing field.
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| CN103647741A (en) * | 2013-12-19 | 2014-03-19 | 电子科技大学 | Subcarrier Index Modulation (SIM)-Orthogonal Frequency Division Multiplexing (OFDM) based superposition coded modulation method |
| CN104331317A (en) * | 2014-08-29 | 2015-02-04 | 电子科技大学 | Space electromagnetic field shaping generating method based on time reversal electromagnetic wave transmission |
| CN105827288A (en) * | 2016-03-11 | 2016-08-03 | 电子科技大学 | 2D-SPM digital wireless communication method based on time-reversal electromagnetic wave dot matrix focusing |
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| US8543070B2 (en) * | 2006-04-24 | 2013-09-24 | Qualcomm Incorporated | Reduced complexity beam-steered MIMO OFDM system |
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| CN104331317A (en) * | 2014-08-29 | 2015-02-04 | 电子科技大学 | Space electromagnetic field shaping generating method based on time reversal electromagnetic wave transmission |
| CN105827288A (en) * | 2016-03-11 | 2016-08-03 | 电子科技大学 | 2D-SPM digital wireless communication method based on time-reversal electromagnetic wave dot matrix focusing |
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