CN113630189A - Information transmission device and method of terahertz multi-input multi-output system - Google Patents

Information transmission device and method of terahertz multi-input multi-output system Download PDF

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CN113630189A
CN113630189A CN202010388522.9A CN202010388522A CN113630189A CN 113630189 A CN113630189 A CN 113630189A CN 202010388522 A CN202010388522 A CN 202010388522A CN 113630189 A CN113630189 A CN 113630189A
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戴凌龙
谭竞搏
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Tsinghua University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/80—Optical aspects relating to the use of optical transmission for specific applications, not provided for in groups H04B10/03 - H04B10/70, e.g. optical power feeding or optical transmission through water
    • H04B10/85—Protection from unauthorised access, e.g. eavesdrop protection
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming

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Abstract

The embodiment of the invention provides an information transmission device and method of a terahertz multi-input multi-output system, wherein the device consists of a multi-path radio frequency link, a delay network formed by a plurality of delay units, a phase shifter network formed by a plurality of shifting units and an antenna unit; each radio frequency link passes through the delay network and then is connected with the phase shifter network, and signals are sent through the antenna units; each delay unit is used for carrying out delay operation on an input bandwidth signal; the phase shifter network is configured to perform a shift operation on the signal. According to the embodiment of the invention, the traditional one-dimensional phase shift regulation is converted into the two-dimensional time delay phase shift combined regulation by introducing the time delay network, so that the wave beam splitting problem of the terahertz broadband large-scale multi-input multi-output system can be effectively solved, and huge performance loss caused by the wave beam splitting phenomenon is avoided.

Description

Information transmission device and method of terahertz multi-input multi-output system
Technical Field
The present invention relates to the field of wireless mobile communications technologies, and in particular, to an information transmission apparatus and method for a mimo system.
Background
In order to meet the increasing business requirements, the mobile communication by using the extremely high bandwidth provided by the terahertz (0.1-10 THz) high frequency band becomes an important technical means of the future mobile communication network. However, in the terahertz frequency band with rich spectrum resources, there is a serious path loss in wireless transmission, and for example, in the terahertz signal of the 0.16THz frequency band, the transmission process will experience a serious path loss as high as 80 dB/km. Massive MIMO (multiple-input multiple-output) technology is recognized as one of the key technologies to overcome this challenge. By configuring a super-large-scale antenna array (for example, 256 antennas), the massive MIMO technology forms a directional beam with extremely high array gain, which can compensate the path loss of a high frequency band and improve the spectral efficiency of the system. Since the introduction in 2010, massive MIMO technology has become a research hotspot in both academic and industrial circles, and the latest 3GPP R15 standard has adopted the formal 5G physical layer technology.
However, in the conventional all-digital MIMO architecture, each antenna needs a dedicated rf link (including mixer, digital-to-analog converter, etc.) for supporting, and the power consumption is often large and the price is not very high. If the conventional structure is directly applied to a massive MIMO system configured with hundreds of antennas, a huge radio frequency network will be required, and the power consumption and cost thereof will be unacceptable. For example, a massive MIMO base station with 256 antennas will consume up to 128 watts in the rf network portion alone, while the total power consumption of the femtocell base station in the current 4G system is not more than ten watts.
In order to reduce the number of radio frequencies of the system and alleviate the bottleneck problems of high power consumption and high cost, the hybrid precoding structure is considered to be a feasible solution for the practical application of massive MIMO. The hybrid precoding structure decomposes the traditional high-dimensional all-digital precoding into two steps, namely firstly carrying out high-dimensional analog beamforming (realized by a phase shifting network) to obtain array gain, and then carrying out low-dimensional digital precoding on a baseband after a small amount of radio frequency sampling to eliminate interference among data streams. Numerous studies have demonstrated that the system is capable of achieving near-optimal and rate performance.
However, for a large-scale MIMO system with a large terahertz frequency band bandwidth, the spatial direction of the channel path component of the large-scale MIMO system is drastically changed with the frequency, and even the same path component at different frequencies is completely split into different spatial directions, i.e. a severe beam splitting phenomenon is generated. Under the beam splitting, because the analog part of the hybrid precoding structure is realized by a phase shifting network, only frequency non-selective phase regulation and control can be carried out, the beam generated by the hybrid precoding structure can only aim at a user at the central frequency, and other frequency bands deviate or even deviate from the user, thereby causing serious array gain and reachable rate loss. The performance loss caused by the beam splitting is particularly prominent under the condition of a terahertz extremely high bandwidth, and even the performance gain caused by the adoption of a high bandwidth can be compensated. At present, although some schemes based on hybrid precoding structures alleviate the performance loss caused by the beam splitting phenomenon, none of the schemes can fundamentally solve the problem.
Disclosure of Invention
The embodiment of the invention provides an information transmission device and method of a terahertz multi-input multi-output system, which are used for solving the problem of performance loss caused by broadband beam splitting.
The embodiment of the invention provides an information transmission device of a terahertz multi-input multi-output system, which comprises:
the antenna comprises a multi-path radio frequency link, a delay network formed by a plurality of delay units, a phase shifter network formed by a plurality of moving units and an antenna unit; each radio frequency link passes through the delay network and then is connected with the phase shifter network, and signals are sent through the antenna units;
each delay unit is used for carrying out delay operation on an input bandwidth signal; the phase shifter network is used for realizing the shift operation on the signal; each radio frequency link is connected with K delay units, and each delay unit is connected with P ═ N/K phase shift units; k delay units connected with different radio frequency links are not overlapped, and P phase shifting units connected with the K delay units corresponding to the same radio frequency link are not overlapped; the P (P is 1,2, … P) th phase shift unit connected with the K (K is 1,2, … K) th delay unit corresponding to different radio frequency links is connected with the (K-1) P + P antenna units through an adder, wherein N is the number of antennas, and N is the number of antennasRFIs the number of rf links.
Optionally, the connection mode between the radio frequency link and the delay network is full connection, sub-connection or dynamic connection; the connection mode between the delay network and the phase shifter network is full connection, sub-connection or dynamic connection.
Optionally, the delay unit is a delay unit or a baseband signal processor.
Optionally, the phase shifter network is a phase shifter, a switch, or an inverter.
The invention also provides an information transmission method of the terahertz multiple-input multiple-output system, which is applied to any one of the information transmission devices of the multiple-input multiple-output system, and the method comprises the following steps:
the precoding design of the phase shifter network and the delay network is divided into NRFEach layer sequentially generates frequency selective beams pointing to the direction of the channel path components according to the sequence of the channel path component energy;
in layer l, the phase shifter network depends on the spatial angle θ of the channel path component at the center frequencyl，cUsing a direction vector a (theta)l，c) Beamforming; the delay network is connected according to the number K of phase shifters and the central frequency space angle theta of each radio frequency linkl，cDesigning time delay to enable the wave beam to be aligned to a corresponding space angle on each subcarrier frequency;
repeating the operation until NRFFrequency selective beams are generated;
and obtaining an equivalent channel based on the designed phase shifter network and delay network parameters, and decomposing the singular value of the equivalent channel to obtain a digital precoding matrix.
Optionally, sequentially generating, by each layer, a frequency selective beam pointing to the direction of the channel path component according to the order of the energy of the channel path component includes:
obtaining channel H by channel estimationmAnd spatial angle thetal，cThe spatial angles theta of the different path componentsl，cAccording to path gain g1|≥|g2|≥…≥|gLI is arranged in sequence;
each layer generates a frequency selective beam directed to the l-th path component.
Optionally, the spatial angle θ at the center frequency according to the channel path componentl，cUsing a direction vector a (theta)l，c) The beamforming comprises the following steps:
spatial angle theta at center frequency according to path componentl，cGenerating a precoding matrix A implemented by a phase shifter networku，l，
Figure BDA0002484752760000031
Wherein,
Figure BDA0002484752760000032
p phase shifter implemented precoding vectors representing the kth delay element corresponding to the l radio frequency link,
Figure BDA0002484752760000033
according to the spatial angle thetal，cAnd the delay unit number K designs the delay of each unit of the delay network to compensate the beam splitting, so that the beam can be aligned to the space direction of the channel path at each subcarrier frequency, and the process is as follows:
Figure BDA0002484752760000041
Figure BDA0002484752760000042
Figure BDA0002484752760000043
wherein s islNumber of cycles, T, representing delay to be compensated for the l-th beamcRepresenting the period of the centre frequency signal, Tc＝1/fcRepeating operation NRFThen, N is generatedRFBeams directed to different path components, tl＝[tl，1，tl，2，…，tl，K]Delay direction provided for K delay units connected with the first radio frequency linkQuantity, i is the delayer number, tl，iRepresenting the delay provided by the ith delay timer of the ith radio link connection.
Optionally, the obtaining an equivalent channel based on the designed phase shifter network and delay network parameters, and the obtaining a digital precoding matrix by singular value decomposition of the equivalent channel includes:
calculating an equivalent channel through the designed phase shifter network and delay network precoding parameters, and calculating a digital precoding matrix through singular value decomposition, wherein the process is as follows:
Figure BDA0002484752760000044
Figure BDA0002484752760000045
where μ is the energy normalization parameter, Hm，eqIn order to be an equivalent channel,
Figure BDA0002484752760000046
for conjugate transpose of the channel matrix, AuIs NxKNRFA phase shift matrix of a dimension phase shifter network, N being the number of antenna elements,
Figure BDA0002484752760000047
is KNRF×NRFDimensional delay network delay matrix, DmIs NRF×NsDimensional digital precoding matrix, NsIn order to realize the purpose,
Figure BDA0002484752760000048
first N of right singular vector matrix of equivalent channelRFColumn, Um，eqIs the left singular vector matrix of the equivalent channel,
Figure BDA0002484752760000049
is the conjugate transpose of the right singular vector matrix of the equivalent channel.
The information transmission device and the method of the terahertz multi-input multi-output system provided by the embodiment of the invention are characterized in that the device consists of a multi-path radio frequency link, a delay network formed by a plurality of delay units, a phase shifter network formed by a plurality of mobile units and an antenna unit; each radio frequency link passes through the delay network and then is connected with the phase shifter network, and signals are sent through the antenna units; each delay unit is used for carrying out delay operation on an input bandwidth signal; the phase shifter network is configured to perform a shift operation on the signal. According to the embodiment of the invention, the traditional one-dimensional phase shift regulation is converted into the two-dimensional time delay phase shift combined regulation by introducing the time delay network, so that the beam splitting problem of a broadband large-scale multi-input multi-output system can be effectively solved, and huge performance loss caused by the beam splitting phenomenon is avoided.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an embodiment of an information transmission apparatus of a terahertz mimo system according to the present invention;
fig. 2 is a flowchart of an embodiment of an information transmission method of a terahertz mimo system according to an embodiment of the present invention;
fig. 3 is a schematic diagram illustrating an embodiment of an information transmission method of a terahertz mimo system according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a beam gain performance of an information transmission scheme of a terahertz mimo system according to the present invention;
fig. 5 is a schematic diagram of the achievable rate performance of the information transmission scheme of the terahertz mimo system according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. 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 invention.
Fig. 1 shows a schematic structural diagram of an embodiment of an information transmission apparatus of a terahertz mimo system, where the apparatus specifically includes:
the antenna comprises a multi-path radio frequency link, a delay network formed by a plurality of delay units, a phase shifter network formed by a plurality of moving units and an antenna unit; each radio frequency link passes through the delay network and then is connected with the phase shifter network, and signals are sent through the antenna units;
each delay unit is used for carrying out delay operation on an input bandwidth signal; the phase shifter network is used for realizing the shift operation on the signal; each radio frequency link is connected with K delay units, and each delay unit is connected with P ═ N/K phase shift units; k delay units connected with different radio frequency links are not overlapped, and P phase shifting units connected with the K delay units corresponding to the same radio frequency link are not overlapped; the P (P is 1,2, … P) th phase shift unit connected with the K (K is 1,2, … K) th delay unit corresponding to different radio frequency links is connected with the (K-1) P + P antenna units through an adder, wherein N is the number of antennas, and N is the number of antennasRFIs the number of rf links.
Each delay unit can delay an input broadband signal, and assuming that the input signal is s (t) and the delay is delta, the output signal is s (t-delta). If s (t) is Fourier transformed and denoted as S (f), the output signal at frequency f may be denoted as S (f) e-j2πfδThat is, the delay unit may generate frequency-selective phase shifts for different frequency signals. Each phase shift unit can generate frequency non-selective phase shift to input broadband signal, and output signal if input signal spectrum S (f) and phase shift is betaThe number may be expressed as S (f) e at frequency f-jβNamely, the phase shift unit generates frequency non-selective phase shift for signals with different frequencies.
In the embodiment of the invention, a delay network connected with a phase shifter network is introduced between a radio frequency link and the phase shifter network of the traditional hybrid precoding structure, and the frequency selective precoding is realized by using the delay provided by the delay network. The connection mode between the radio frequency link and the delay network includes but is not limited to full connection, sub-connection or dynamic connection; the connection between the delay network and the phase shifter network includes, but is not limited to, full connection, sub-connection, or dynamic connection.
As a specific embodiment, the delay unit is used for delaying the signal, and there may be various implementations in hardware, including but not limited to a delay unit or a baseband signal processor, which can generate a hardware structure equivalent to the time-domain delay.
As a specific embodiment, the phase shifter network is used to implement a shift operation on a signal, and there may be various implementations of the phase shifter network in hardware, including but not limited to phase shifters, switches, or inverters with different precision, which can generate a hardware structure equivalent to a frequency domain phase shift.
A flowchart of a specific implementation of a method for transmitting information in a terahertz mimo system according to an embodiment of the present invention is shown in fig. 2, where the method is applicable to any one of the above-mentioned information transmission apparatuses in the mimo system, and the method includes:
step S201: the precoding design of the phase shifter network and the delay network is divided into NRFEach layer sequentially generates frequency selective beams pointing to the direction of the channel path components according to the sequence of the channel path component energy;
step S202: in layer l, the phase shifter network depends on the spatial angle θ of the channel path component at the center frequencyl，cUsing a direction vector a (theta)l，c) Beamforming;
step S203: the delay network is connected according to the number K of phase shifters and the central frequency space angle theta of each radio frequency linkl，cDesigning time delay to enable the wave beam to be aligned to a corresponding space angle on each subcarrier frequency;
step S204: operations S202-S203 are repeated until NRFFrequency selective beams are generated;
step S205: and obtaining an equivalent channel based on the designed phase shifter network and delay network parameters, and decomposing the singular value of the equivalent channel to obtain a digital precoding matrix.
Considering a terahertz wideband massive MIMO system employing OFDM modulation, where the number of subcarriers is M, for the mth (M ═ 1,2, … M) subcarrier, the transmission model may be expressed as
Figure BDA0002484752760000071
Wherein y ismIs NsX 1 received signal vector; n is a radical ofsIs the number of transmission streams; hmIs NsA xN channel matrix; n is the number of antenna units of massive MIMO at the base station end; a. theuIs NxKNRFDimensional phase shifter network phase shift matrix, where NRFFor base station radio frequency number, K is the number of delay units per radio frequency connection, one
Figure BDA0002484752760000072
While
Figure BDA0002484752760000073
Wherein
Figure BDA0002484752760000074
The precoding vectors realized by P phase shifters representing the kth delay unit corresponding to the l radio frequency link are
Figure BDA0002484752760000075
Figure BDA0002484752760000076
Is KNRF×NRFDimension delay network delay matrix, having
Figure BDA0002484752760000077
Wherein t isl＝[tl，1，tl，2，…，tl，K]Representing delay vectors provided by K delay units of the first radio frequency link; dmIs NRF×NsA dimensional digital precoding matrix; s is NsX 1 signal vector to be transmitted; n is NsX 1 additive noise, variance σ2. In the high-frequency bands such as millimeter wave and terahertz, it can be generally considered that the channel is formed by overlapping channel components of different paths, and then H ismCan be expressed as
Figure BDA0002484752760000078
Wherein f ismDenotes the frequency of the M (M is 1,2, … M) th subcarrier, and defines the center frequency as fcThe bandwidth f is
Figure BDA0002484752760000081
L is the number of paths, glAnd τlRespectively, the path gain and delay of the L (1, 2, … L) th path component, ft(θl，m) And fr(φl，m) Respectively representing transmit and receive direction vectors, wherel，mAnd phil，mRespectively representing the spatial directions of the first path component at the transmitting end and the receiving end, which can be expressed as
Figure BDA0002484752760000082
The target for designing the precoding matrix in the embodiment of the present invention is to maximize the achievable rate R, which can be expressed as
Figure BDA0002484752760000083
The theory proves that because the high-frequency channel such as millimeter wave and terahertz has sparsity L & lt & ltN & gt in the space domain, the analog precoding generates wave beams pointing to different path component space directions to obtain the channel array gain, and the digital precoding eliminates the inter-flow interference, thus achieving the quasi-optimal achievable rate performance. Thus, in the conventional precoding structure, the direction vector f is usedt(θl，c) As an analog precoding vector, where θl，cRepresenting the spatial angle of the ith path component at the center frequency. However, in high frequency bands such as millimeter wave and terahertz, the extremely high bandwidth may cause a serious beam splitting phenomenon, specifically, for the l-th path component, the spatial angle thereof is dependent on the frequency fmThe change is that the number of the first and second,
Figure BDA0002484752760000084
under the beam splitting phenomenon, the traditional precoding structure can only realize frequency non-selective phase regulation and control, so that the beams can not be aligned to the space direction of a path on all subcarriers, and serious array gain and reachable rate loss are caused.
Fig. 3 is a schematic diagram of a specific implementation of the information transmission method of the terahertz mimo system according to the embodiment of the present invention, in which a channel H is initially obtained through channel estimationmAnd spatial angle thetal，c. Wherein a channel H is obtainedmAnd spatial angle thetal，cThe process of (a) can be implemented by a variety of existing methods. And the spatial angle theta of the different path componentsl，cAccording to path gain g1|≥|g2|≥…≥|gLI is arranged in sequence; then, precoding design of phase shifter network and delay network is carried out, and the process is decomposed into NRFLayer by layer, each layer generating a beam pointing to the l-th path component; in each layer, the spatial angle θ at the center frequency according to the path component is firstl，cGenerating a precoding matrix A implemented by a phase shifter networku，l，
Figure BDA0002484752760000091
Then, according to the space angle thetal，cAnd the delay unit number K designs the delay of each unit of the delay network to compensate the beam splitting, so that the beam can be aligned to the space direction of the channel path at each subcarrier frequency, and the process is as follows:
Figure BDA0002484752760000092
Figure BDA0002484752760000093
Figure BDA0002484752760000094
wherein s islNumber of cycles, T, representing delay to be compensated for the l-th beamcRepresenting the period of the central frequency signal, having Tc＝1/fc. Repeating the above steps by NRFAfter that, N can be generatedRFBeams directed to different path components, tl＝[tl，1，tl，2，…，tl，K]Delay vectors provided for K delay units of the first radio frequency link, i being the delayer number, tl，iRepresenting the delay provided by the ith delay timer of the ith radio link connection. And finally, calculating an equivalent channel through the designed phase shifter network and delay network precoding parameters, and calculating a digital precoding matrix through singular value decomposition, wherein the process is as follows:
Figure BDA0002484752760000095
Figure BDA0002484752760000096
where μ is the energy normalization parameter, Hm，eqIn order to be an equivalent channel,
Figure BDA0002484752760000097
for conjugate transpose of the channel matrix, AuIs NxKNRFA phase shift matrix of a dimension phase shifter network, N being the number of antenna elements,
Figure BDA0002484752760000098
is KNRF×NRFDimensional delay network delay matrix, DmIs NRF×NsDimensional digital precoding matrix, NsIn order to realize the purpose,
Figure BDA0002484752760000099
first N of right singular vector matrix of equivalent channelRFColumn, Um，eqIs the left singular vector matrix of the equivalent channel,
Figure BDA00024847527600000910
is the conjugate transpose of the right singular vector matrix of the equivalent channel.
The scheme provided by the invention can effectively solve the performance loss caused by the wave beam splitting phenomenon, and improve the array gain and the reachable rate performance. Referring to fig. 4 and fig. 5, fig. 4 shows a schematic diagram of a beam gain performance of an information transmission scheme of a mimo system provided by the present invention, and fig. 5 shows a schematic diagram of a achievable rate performance of an information transmission scheme of a mimo system provided by the present invention, in which compared with a conventional scheme, a precoding scheme provided by the present invention can improve a wideband average beam gain by more than 50%, and improve a achievable rate performance of a wideband large-scale mimo system by more than 30%.
In the embodiment of the invention, the phase shifter network carries out beam forming by using the channel path space angle of the central frequency, the delay network designs delay based on parameters such as subcarrier frequency, path physical angle and the like to compensate beam splitting, and then digital precoding is obtained by decomposing equivalent channel singular values. The time delay-phase shift combined regulation and control pre-coding structure and the corresponding mixed pre-coding scheme provided by the invention can effectively compensate the beam gain loss of a broadband large-scale multi-input multi-output system caused by the broadband beam splitting phenomenon, and improve the beam gain and the achievable rate performance.
The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. Meanwhile, it should be noted that although the present solution is described by taking a terahertz system with a serious beam splitting phenomenon as an example, the present solution can be applied to a millimeter wave and low frequency band system with a less serious beam splitting phenomenon. One of ordinary skill in the art can understand and implement it without inventive effort.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods described in the embodiments or some parts of the embodiments.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (8)

1. An information transmission apparatus of a terahertz multiple-input multiple-output system, comprising:
the antenna comprises a multi-path radio frequency link, a delay network formed by a plurality of delay units, a phase shifter network formed by a plurality of moving units and an antenna unit; each radio frequency link passes through the delay network and then is connected with the phase shifter network, and signals are sent through the antenna units;
each delay unit is used for carrying out delay operation on an input bandwidth signal; the phase shifter network is used for realizing the shift operation on the signal; each radio frequency link is connected with K delay units, and each delay unit is connected with P ═ N/K phase shift units; k delay units connected with different radio frequency links are not overlapped, and P phase shifting units connected with the K delay units corresponding to the same radio frequency link are not overlapped; the P (P is 1,2, … P) th phase shift unit connected with the K (K is 1,2, … K) th delay unit corresponding to different radio frequency links is connected with the (K-1) P + P antenna units through an adder, wherein N is the number of antennas, and N is the number of antennasRFIs the number of rf links.
2. The information transmission apparatus of the terahertz mimo system as claimed in claim 1, wherein the connection between the rf link and the delay network is full connection, sub-connection or dynamic connection; the connection mode between the delay network and the phase shifter network is full connection, sub-connection or dynamic connection.
3. The information transmission apparatus of the terahertz multiple-input multiple-output system according to claim 2, wherein the delay unit is a delayer or a baseband signal processor.
4. The information transmission apparatus of the terahertz multiple-input multiple-output system according to claim 3, wherein the phase shifter network is a phase shifter, a switch, or an inverter.
5. An information transmission method of a terahertz multiple-input multiple-output system, applied to the information transmission apparatus of the multiple-input multiple-output system according to any one of claims 1 to 4, the method comprising:
the precoding design of the phase shifter network and the delay network is divided into NRFEach layer sequentially generates frequency selective beams pointing to the direction of the channel path components according to the sequence of the channel path component energy;
in layer l, the phase shifter network depends on the spatial angle θ of the channel path component at the center frequencyl,cUsing a direction vector a (theta)l,c) Beamforming;
the delay network is connected according to the number K of phase shifters and the central frequency space angle theta of each radio frequency linkl,cDesigning time delay to enable the wave beam to be aligned to a corresponding space angle on each subcarrier frequency;
repeating the operation until NRFFrequency selective beams are generated;
and obtaining an equivalent channel based on the designed phase shifter network and delay network parameters, and decomposing the singular value of the equivalent channel to obtain a digital precoding matrix.
6. The method of claim 5, wherein sequentially generating, by each layer, frequency-selective beams pointing in the direction of the channel path component in order of the energy of the channel path component comprises:
obtaining channel H by channel estimationmAnd spatial angle thetal,cThe spatial angles theta of the different path componentsl,cAccording to path gain g1|≥|g2|≥…≥|gLI is arranged in sequence;
each layer generates a frequency selective beam directed to the l-th path component.
7. The information transmission method of the terahertz multiple-input multiple-output system according to claim 5 or 6, wherein the spatial angle θ at the center frequency according to the channel path componentl,cUsing a direction vector a (theta)l,c) The beamforming comprises the following steps:
spatial angle theta at center frequency according to path componentl,cGenerating a precoding matrix A implemented by a phase shifter networku,l，
Figure FDA0002484752750000021
Wherein,
Figure FDA0002484752750000022
p phase shifter implemented precoding vectors representing the kth delay element corresponding to the l radio frequency link,
Figure FDA0002484752750000023
according to the spatial angle thetal,cAnd the delay unit number K designs the delay of each unit of the delay network to compensate the beam splitting, so that the beam can be aligned to the space direction of the channel path at each subcarrier frequency, and the process is as follows:
Figure FDA0002484752750000024
Figure FDA0002484752750000025
Figure FDA0002484752750000026
wherein s islNumber of cycles, T, representing delay to be compensated for the l-th beamcRepresenting the period of the centre frequency signal, Tc＝1/fcRepeating operation NRFThen, N is generatedRFBeams directed to different path components, tl＝[tl,1,tl,2,…,tl,K]Delay vectors provided for K delay units of the first radio frequency link, i being the delayer number, tl,iRepresenting the delay provided by the ith delay timer of the ith radio link connection.
8. The method of claim 7, wherein obtaining an equivalent channel based on the designed parameters of the phase shifter network and the delay network, and obtaining a digital precoding matrix by singular value decomposition of the equivalent channel comprises:
calculating an equivalent channel through the designed phase shifter network and delay network precoding parameters, and calculating a digital precoding matrix through singular value decomposition, wherein the process is as follows:
Figure FDA0002484752750000031
Figure FDA0002484752750000032
where μ is the energy normalization parameter, Hm,eqIn order to be an equivalent channel,
Figure FDA0002484752750000033
for conjugate transpose of the channel matrix, AuIs NxKNRFA phase shift matrix of a dimension phase shifter network, N being the number of antenna elements,
Figure FDA0002484752750000034
is KNRF×NRFDimensional delay network delay matrix, DmIs NRF×NsDimensional digital precoding matrix, NsIn order to realize the purpose,
Figure FDA0002484752750000035
first N of right singular vector matrix of equivalent channelRFColumn, Um,eqIs the left singular vector matrix of the equivalent channel,
Figure FDA0002484752750000036
is the conjugate transpose of the right singular vector matrix of the equivalent channel.
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