CN115765926A - Progressive coding spatial modulation method based on intelligent reflecting surface - Google Patents
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Abstract
A step-by-step coding spatial modulation method based on an intelligent reflecting surface comprises the following steps: the method comprises the steps of sending end space modulation, RIS space modulation, receiving end space modulation and detection decoding. A transmitting terminal divides information bits to be transmitted into a plurality of information blocks with the same length, the information blocks are divided into three information sub-blocks, and the transmitting terminal selects a corresponding active antenna to transmit a specific signal according to a first information sub-block; the RIS selects an active virtual antenna according to the second information subblock, and opens an active reflection element corresponding to the active virtual antenna; the receiving end determines the index of the active antenna according to the third information sub-block; and finally, adopting maximum likelihood detection decoding at a receiving end to recover the original information bits. The invention combines RIS and progressive coding space modulation scheme, realizes the joint space modulation of the transmitting end, RIS and the receiving end, effectively utilizes respective space freedom degree and improves the transmission rate of the system.
Description
Technical Field
The invention belongs to the technical field of wireless communication, and particularly relates to a step-by-step coding spatial modulation method based on an intelligent reflector.
Background
In future Generation-6 g wireless networks, higher Spectral Efficiency (SE) and Energy Efficiency (EE) are receiving increasing attention as communication devices are explosively increasing. Index Modulation (IM) is one of the enabling techniques to meet these requirements of 6G. Index modulation transmits information bits by indexes of space, frequency, or polarization, which can provide higher spectral efficiency and energy efficiency. Among all forms of index modulation, spatial modulation is one of the most widely used techniques.
The spatial modulation technique is a modulation mode based on a multi-antenna architecture. The space domain is added on the basis of the traditional constellation modulation, and extra information bits are transmitted through the indexes of active antennas, so that the method is a very promising wireless physical layer modulation technology. In a spatial modulation system, the number of radio frequency links can be much less than the number of transmit antennas, which greatly reduces the hardware cost and power consumption of the system. Meanwhile, in the spatial modulation system, only one or more antennas are activated to transmit signals in a time slot, so that the interference of adjacent antennas is effectively reduced, and the requirement on strict synchronization of the transmitted signals is lowered. Many spatial modulation schemes have been proposed, for example: space Shift keying Modulation (SSK), space Modulation (SM), generalized Spatial Modulation (GSM), orthogonal Spatial Modulation (QSM), and progressive Coded Spatial Modulation (SC-SM).
Recently, researchers are inspired by Intelligent super-surface, and utilize the Intelligent super-surface to reconstruct wireless transmission channel to improve the spectrum efficiency and service quality of the existing communication system, and propose the concept of Intelligent reflecting surface (RIS). The RIS can enhance signal coverage, improve signal transmission quality, and improve wireless transmission environment, and thus is called one of alternative technologies of the future 6G. In fact, the RIS is made up of a large number of passive and low-cost reflective elements that improve transmission quality by changing the amplitude, phase or frequency of the incident signal to reconstruct the transmission environment. Based on the advantages, the method combines the RIS and the spatial modulation technology, utilizes the RIS to assist the spatial modulation system, and constructs a high-efficiency and reliable communication transmission system.
Currently, much research has been conducted on RIS assisted spatial modulation systems. In these studies, researchers often combine RIS with traditional spatial modulation schemes, such as: SSK scheme and SM scheme, etc., without combining RIS with spatial modulation schemes with higher spectral efficiency and higher reliability performance, such as: QSM scheme or SC-SM scheme, etc. Meanwhile, in the existing research, spatial modulation is often only performed on the transmitting end, the RIS or the receiving end independently, and the joint spatial modulation of the transmitting end, the RIS and the receiving end is not realized, so that the transmission rate of the system is limited to a certain extent.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the defects of the prior art, the invention provides a progressive coding spatial modulation method based on an intelligent reflecting surface, which combines an RIS and a progressive coding spatial modulation technology and realizes the joint spatial modulation of a sending end, the RIS and a receiving end, so as to solve the technical problem of limiting the transmission rate of a system in the traditional spatial modulation.
The technical scheme is as follows: in order to solve the technical problem, the specific technical scheme of the step-by-step coding spatial modulation method based on the intelligent reflecting surface is as follows:
a step-by-step coding spatial modulation method based on an intelligent reflector is characterized by comprising the following steps: transmitting end spatial modulation, RIS spatial modulation, receiving end spatial modulation and detection decoding:
the method needs to perform joint spatial modulation on the transmitting end, the RIS and the receiving end, thereby improving the transmission rate of the system. The system comprises a transmitting end, a RIS and a receiving end, wherein, progressive coding spatial modulation is carried out on the transmitting end and the RIS, and progressive coding space shift keying is carried out on the receiving end.
The sending end divides information bits to be sent into a plurality of information blocks with the same length, each information block comprises a plurality of information subblocks, and each information subblock at least comprises a first information subblock, a second information subblock and a third information subblock; the information subblocks are loaded on the sending end, the RIS and the receiving end respectively and sent; based on a progressive coding spatial modulation principle, the transmitting end selects an active antenna to transmit signals according to the first information subblock, and spatial modulation of the transmitting end is achieved;
dividing all elements on the RIS into a plurality of non-uniform groups, wherein each group is used as a virtual antenna; based on a spatial modulation principle, the RIS selects an active virtual antenna according to the second information subblock, a reflection element corresponding to the active virtual antenna selected by the second information subblock is called as an active reflection element, and the active reflection element is opened to reflect an incident signal; the reflection elements corresponding to the virtual antenna which is not selected by the second information subblock are inactive reflection elements, and the inactive reflection elements are closed to realize spatial modulation on the RIS;
determining the index of the active antenna of the receiving end according to the third information sub-block based on a progressive coding space shift keying principle, wherein a group of reflection elements corresponding to each active virtual antenna on the RIS respectively serve each active antenna of the receiving end; and the receiving end recovers the original information bits by adopting a maximum likelihood detection algorithm according to the received signal vectors and based on a decoding principle of step-by-step coding spatial modulation.
Preferably, the length of the information block is obtained by the dimension of the total spatial pattern; the length of the information subblocks is obtained through the dimensions of the space patterns on the transmitting end, the RIS and the receiving end; the spatial pattern is a combination of selected active antennas and selected transmit constellation points.
Preferably, when all elements on the RIS are divided into a plurality of non-uniform groups, the number of elements in each group after division is different from each other. And the optimal division mode is to make the number difference of the reflecting elements in different groups as large as possible.
Preferably, when spatial modulation is implemented on the RIS, spatial domain modulation and constellation domain modulation are included;
when the space domain modulation is carried out, according to space information bits in the second information subblock, based on a step-by-step coding space modulation principle, selecting a plurality of active virtual antennas, opening a plurality of groups of corresponding active reflection elements to reflect incident signals, and closing non-reflected signals by the non-active reflection elements;
when constellation domain modulation is carried out, phase modulation coefficients are selected for a group of active reflection elements corresponding to each active virtual antenna according to constellation information bits in the second information subblock, and the constellation domain modulation is carried out.
Each group of elements divided on the RIS is used as a virtual antenna, and the intelligent reflecting surface can be equivalent to a part of a transmitting end with a plurality of virtual antennas.
Preferably, the number of virtual antennas active on said RIS is the same as the number of antennas active on the receiving end; a group of active reflection element service receiving end first active antennas with the largest number of elements is arranged on the RIS, and the signal power on the first active receiving antenna is maximized by adjusting the phases of all reflection elements in the group to form a beam pointing to the receiving end first active antenna; a group of active reflection elements with the second largest number of elements serves the second active antenna at the receiving end, and so on. The power on the first active antenna on the receiving end is the largest, the second time, and so on. The power of the inactive antenna on the receiving end is far less than that of the active antenna, so that subsequent detection and decoding are facilitated.
Preferably, the reflection element on the RIS has an amplitude modulation coefficient of 1, and the final phase of the active reflection element is the sum of the phase of the constellation domain modulation and the beamforming phase on the RIS.
Preferably, the transmitting end is equipped with N t Root antenna, said receiving end being equipped withN r A root antenna, K reflective elements on the RIS, the reflective elements divided into P t Group (d);
the channel matrix from sender to RIS is
The channel matrix from the intelligent reflecting surface to the receiving end is
The RIS corresponds to a reflection matrix of Θ = diag (θ), where
The direct path from the sending end to the receiving end is blocked, and the RIS obtains the state information of the ideal channel.
Preferably, the RIS corresponds to a reflection matrix Θ, which is composed of three parts:
Θ＝Θ 1 ·Θ 2 ·Θ 3 , (1)
wherein, theta 1 ＝diag(θ 1 )，
θ 1 Determined by the spatial information bits of the second information subblock: when the virtual antenna corresponding to a group of elements on the RIS is an inactive antenna, the group of elements is at θ 1 All values in (1) are 0; when the virtual antenna corresponding to a group of elements on the RIS is an active antenna, the group of elements is at θ 1 All values in (1) are 1;
Θ 2 ＝diag(θ 2 )，
θ 2 and the constellation domain information bits of the second information subblock are used for determining: when the virtual antenna corresponding to a group of elements on the RIS is an inactive antenna, the group of elements is at θ 2 All values in (1) are 0; when a certain set of elements is on the RISThe set of elements is at θ when the corresponding virtual antenna is an active antenna 2 The values in the step (a) are all specific phase modulation coefficients selected for the group based on constellation domain information bits;
Θ 3 ＝diag(θ 3 )，
θ 3 determining from the third information subblock: when the ith reflection element on the RIS is an inactive reflection element, theta 3 The ith element in (1) is 0; when the jth reflection element on the RIS is an active reflection element, theta 3 The j-th element value is obtained by calculating the power of a specific receiving antenna of a receiving end to the maximum by the group where the element is positioned, and the module value is 1;
preferably, the sending end sends out the signal, reflects to the receiving end by RIS, and the receiving end detects, decodes to it after receiving the signal that contains the noise. The signal vector received by the receiving end is:
y＝G·Θ·H·x+n, (2)
wherein:
y is the signal vector received by the receiving end and has a dimension of N r X 1; x is the signal vector sent by the sending end and has the dimension of N t X 1; n is an additive white Gaussian noise vector with dimension N r X 1, each component obeys a mean of zero and a variance of σ n 2 Complex gaussian distribution.
Preferably, the maximum likelihood detection algorithm is:
wherein: i | · | live through F Represents the Frobenius norm; x is the number of i The ith sending signal vector is represented and carries the bit information of the first information subblock; theta j The j reflection matrix representing the RIS carries the bit information of the second information sub-block and the third information sub-block;
are each x i And Θ j Estimation under maximum likelihood detection.
The invention has the beneficial effects that:
1. the invention combines RIS and progressive coding space modulation scheme, and fully utilizes the technical advantages of the RIS and the progressive coding space modulation scheme. On one hand, the performance of the existing spatial modulation system is further enhanced by using the RIS; on the other hand, compared with the traditional spatial modulation scheme, the progressive coding spatial modulation scheme can achieve higher transmission rate and has better error code performance under the same condition, and is a more efficient and reliable spatial modulation scheme.
2. The invention transmits information bits on the sending end, the RIS and the receiving end jointly, realizes the joint space modulation of the sending end, the RIS and the receiving end, effectively utilizes the respective space freedom degrees of the three, and greatly improves the transmission rate of the system.
Drawings
FIG. 1 is a schematic block diagram of the present invention;
fig. 2 is a schematic block diagram of an embodiment of 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.
A step-by-step coding spatial modulation method based on an intelligent reflecting surface comprises a sending end spatial modulation process, a RIS upper spatial modulation process, a receiving end spatial modulation process and a detection decoding process.
Firstly, dividing information bits to be transmitted into a plurality of information blocks, dividing one information block into three information sub-blocks, respectively loading the information sub-blocks on a transmitting end, an intelligent reflecting surface and a receiving end for transmitting, and based on a spatial modulation principle, selecting an active antenna by the transmitting end according to a first information sub-block to transmit signals to realize spatial modulation of the transmitting end; then, dividing all elements on the intelligent reflecting surface into a plurality of non-uniform groups, wherein all elements in each group are used as a virtual antenna, based on a spatial modulation principle, the intelligent reflecting surface selects an active virtual antenna according to a second information sub-block, the active reflecting element corresponding to the selected active virtual antenna is opened to reflect an incident signal, the inactive reflecting elements corresponding to the other virtual antennas are closed to not reflect an external signal, and spatial modulation on the intelligent reflecting surface is realized; then, determining the index of an active antenna at the receiving end according to a third information sub-block to be sent, adjusting the phase of an incident signal by using all active reflection elements on an intelligent reflection surface based on prior channel state information, forming a directional beam pointing to the active antenna at the receiving end, and realizing the spatial modulation of the receiving end; and finally, the receiving end adopts a maximum likelihood detection algorithm to estimate the transmitted pattern according to the received signal vector, and recovers the original information bit according to the estimated parameters based on a demodulation algorithm of the step-by-step coding spatial modulation.
The invention will be further described with reference to the accompanying drawings.
As shown in fig. 1, the transmitting end is equipped with N t Root antenna, receiving end equipped with N r A root antenna with K reflecting elements on RIS, which is unevenly divided into P t Groups, each group containing L 1 ,L 2 ,…,L Pt An element of, wherein, L 1 ＜L 2 ＜…＜L Pt-1 ＜L Pt . The channel matrix from sender to RIS is
The channel matrix from the RIS to the receiving end is
The RIS corresponds to a reflection matrix Θ = diag (θ), where
The step-by-step coding spatial modulation carried out by the transmitting end comprises n t The method comprises the following steps: in the first step, the first N antennas at the transmitting end are regarded as a first group, wherein N is an integral power of 2 and is according to log 2 (N) bit information selects one antenna from the first group as an active antenna and based on log 2 (M) bit information from Ψ 1 Middle selection signal s 1 Sending s by the selected active antenna 1 (ii) a In the second step, the N inactive antennas in the first N +1 antennas at the transmitting end are regarded as the second group, namely the first active antenna is excluded, and the second group is based on log 2 (N) bits of information selecting one antenna from the second group as an active antenna and based on log 2 (M) bit information from Ψ 2 Middle selection signal s 2 Sending s by the selected active antenna 2 . In the (j + 1) th step, taking N inactive antennas in the front (N + j) antennas of the sending end as a (j + 1) th group, namely excluding j active antennas, and according to log 2 (N) bit information selects one antenna from the j +1 th group as an active antenna and according to log 2 (M) bit information from Ψ j+1 Middle selection signal s j+1 Sending s by the selected active antenna j+1 Through n, by t The final sending end has n t The root active antenna transmits a signal and has N t ＝N+n t -1。n t The signals transmitted on the root active antenna are respectively
They are respectively from
Selecting. Therein, Ψ i Is a signal set comprising M constellation points, an
And i ≠ j. n is t The indexes of the root active antenna at the transmitting end are respectively
All elements on the RISDividing into several groups with different numbers of elements, using each group as a virtual antenna, RIS can be equivalent to P t The part of the transmitting end of the virtual antenna, which is subjected to the step-by-step coding spatial modulation on the RIS, comprises p t Step, the modulation process is the same as that of the sending end, in each step, one virtual antenna is selected from P virtual antennas as an active virtual antenna, wherein P is an integral power of 2 and passes through P t Sub-selection, final selection of p t Root active virtual antenna and has P t ＝P+p t -1，p t Root active virtual antenna correspondence p t Each active virtual antenna corresponds to a reflection element group, and all reflection element values in each group are respectively
They are respectively from
Selecting. Wherein phi i Is a set containing Q Phase Shift Keying (PSK) signals, and
and i ≠ j. p is a radical of t The indexes of the root active virtual antenna on the RIS are respectively
When the receiving end carries out the step-by-step coding space shift keying, the method can be equivalent to only carrying out the space domain modulation in the step-by-step coding space modulation, but not carrying out the constellation domain modulation, namely only determining the index of the active antenna, but not carrying out the selection of the signal. The receiving end carries out progressive coding space shift keying and comprises n r And each step selects one antenna from R antennas as an active antenna, wherein R is an integral power of 2. Through n r Sub-selecting, finally selecting n r Root active antenna and has N r ＝R+n r -1。n r The indexes of the root active antenna at the receiving end are respectively
And n is r ＝p t 。
In this embodiment, it is assumed that a direct path from a transmitting end to a receiving end is blocked, and an RIS can obtain ideal channel state information, and the progressive coding spatial modulation method based on an intelligent reflecting surface disclosed by the present invention includes the following processes and steps:
(1) Transmitting end spatial modulation process
Step 1) dividing information bits to be transmitted into a plurality of information blocks with the same length, wherein each information block comprises a plurality of information sub-blocks, and each information sub-block at least comprises a first information sub-block, a second information sub-block and a third information sub-block;
the length of the information block is obtained by the dimension of the total spatial pattern; one of the information blocks represents the total bits that the current communication system can transmit in one transmission;
the three information subblocks respectively represent information bits loaded on the transmitting end, the RIS and the receiving end, and the lengths of the information subblocks are respectively determined by the dimensions of the spatial patterns on the transmitting end, the RIS and the receiving end;
the spatial pattern is a combination of selected active antennas and selected transmission constellation points:
the lengths of the information blocks and the information sub-blocks are calculated and obtained on the basis of a progressive coding spatial modulation principle and are as follows:
step 2) based on the progressive coding spatial modulation principle, the sending end selects n according to the first information subblock t Transmitting signals separately from the corresponding antennas
The antenna sending the signal is the active antenna;
transmitting signal vector
Can be expressed as:
(2) Spatial modulation procedure over RIS
Step 3) partitioning all elements on the RIS into non-uniform P t Groups, each group acting as a virtual antenna, the RIS can be equivalently equipped with P t A portion of the transmitting end of the root virtual antenna. Selecting several active virtual antennas according to the second information sub-block, opening several groups of active reflection elements corresponding to the active virtual antennas, and selecting a specific phase modulation coefficient for each group of active elements;
the reflection matrix Θ corresponding to RIS is composed of three parts:
Θ＝Θ 1 ·Θ 2 ·Θ 3 , (6)
wherein, theta 1 ＝diag(θ 1 )，
θ 1 And the spatial domain information bit of the second information subblock in the divided information block is determined, wherein each element takes the value of 0 or 1. When the virtual antenna corresponding to a group of elements on the RIS is an inactive antenna, the group of elements is at θ 1 All values in (1) are 0; when the virtual antenna corresponding to a group of elements on the RIS is an active antenna, the group of elements is at θ 1 All values in (1) are 1. Theta 2 ＝diag(θ 2 )，
θ 2 And the constellation domain information bit of the second information subblock in the divided information block. When the virtual antenna corresponding to a group of elements on the RIS is an inactive antenna, the group of elements is at θ 2 All values in (1) are 0; when the virtual antenna corresponding to a certain group of elements on the RIS is the active antennaThe element of this group being at θ 2 The values in (1) are all specific phase modulation coefficients selected for the group based on constellation domain information bits. Note that θ 2 Wherein the values of the reflection elements belonging to the same group are the same.
Θ 3 ＝diag(θ 3 )，
θ 3 Determined by the third information sub-block in the divided information block. Theta when the ith reflecting element on the RIS is an inactive reflecting element 3 The ith element in (1) is 0; when the jth reflection element on the RIS is an active reflection element, theta 3 The value of the jth element is obtained by maximizing the power of a specific receiving antenna of a receiving end by the grouping of the jth element, and the module value is 1.
Partitioning all elements on the RIS into non-uniform P t And (4) grouping. Based on the grouping result, the reflection vector
Can be expressed as:
each group of reflection elements is used as a virtual antenna, and the RIS can be equivalently provided with P t A portion of the transmitting end of the root virtual antenna. At this time, the reflection vector may be rewritten as:
wherein,
is the equivalent sending signal vector of the sending end, the ith element gamma in gamma i Corresponding to group i in theta.
Based on the progressive coding spatial modulation principle, an active virtual antenna is selected according to a second information sub-block in the divided information blocks, a plurality of groups of active reflection elements corresponding to the active virtual antenna are opened, and a specific phase modulation coefficient is selected for each group of active elements. The modulated transmit signal vector γ can be expressed as:
after determining the location of the active virtual antenna, θ 1 Can be expressed as:
after determining the phase modulation factor for each group, θ 2 Can be expressed as:
the reflection matrix Θ by the spatial modulation process on the RIS 1 、Θ 2 May be determined.
(3) Receiver side spatial modulation process
And 4) determining the index of the active antenna at the receiving end according to the third information sub-block in the divided information blocks based on a progressive coding space shift keying scheme. A set of reflection elements corresponding to each active virtual antenna on the RIS respectively serve each active antenna of the receiving end, that is: a group of active reflection elements with the largest number of elements on the RIS serves a first active antenna of a receiving end, and the phases of all reflection elements in the group are adjusted to maximize the signal power on the first active receiving antenna, so that a beam is formed to point to the first active antenna of the receiving end; the RIS has a group of active reflection element service receiving ends with the second largest number of elements, and so on.
After the index of the active antenna of the receiving end is determined, the active reflection elements on the RIS group respectively serve each specific active antenna of the receiving end, and the signal power on each active antenna of the receiving end is maximizedThe target determines the value of the reflection element. Theta 3 Can be expressed as:
wherein σ k Denotes the k-th reflection element on the RIS at theta 3 Wherein, i, j, m, n respectively represent the
The index of the first reflection element in the set on the RIS, and has i < j < m < n.
In the following by i Calculate θ for an example 3 And (4) the value of the middle reflection element. Transmitting terminal n t Root active antenna sends n respectively t The signal is sent to the ith reflection element on the RIS, and the signal received by the ith reflection element can be expressed as:
wherein,
is the ith row l in H q Column element, indicating the l-th of the sender q The channel coefficients of the root antenna to the ith reflection element on the RIS.
Suppose the v' th on the RIS 1 All reflection elements in the group serve the Wth receiving end j And the signal received by the antenna is:
wherein
Indicates the w-th of the receiving end j A signal received by a root antenna;
is w in G j Row and column elements, representing the p-th reflection element on the RIS to the w-th receiving end j Channel coefficients of the root antennas; theta p Indicating the reflection coefficient of the p-th element on the RIS.
In order to make the receiving end w j The received signal power at the root antenna is maximized,
(4) Detecting a decoding process
And step 5) the receiving end adopts maximum likelihood detection decoding according to the received signal vector to recover the original information bit.
The signal vector received by the receiving end can be expressed as:
y＝G·Θ·H·x+n, (15)
wherein: y is the vector of the signal received by the receiving end with dimension N r X 1; x is the signal vector sent by the sending end and has the dimension of N t X 1; n is an additive white Gaussian noise vector with dimension N r X 1, where each component obeys a mean of zero and a variance of
Complex gaussian distribution.
The maximum likelihood detection algorithm may be expressed as follows:
after the maximum likelihood detection is carried out at the receiving end, based on the decoding principle of the step-by-step coding spatial modulation, according to the estimated parameters
The original information bits are recovered.
The step-by-step coding spatial modulation method based on the intelligent reflecting surface of the present invention is further described in a specific embodiment with reference to fig. 2.
As shown in fig. 2, the transmitting end is equipped with 3 antennas, the receiving end is equipped with 3 antennas, and there are 24 reflection elements on the RIS, which are divided into three groups, each group consisting of 4,8 and 12 reflection elements.
A channel matrix representing the sender to the RIS,
and representing a channel matrix from the RIS to the receiving end, and assuming that a direct path from the sending end to the receiving end is blocked. s i Is the signal transmitted by the ith active antenna of the transmitting end from psi i ＝{s i1 ,s i2 And (6) selecting.
Is the phase modulation coefficient determined by the ith active group on RIS in constellation modulation
To select.
From the above, N t ＝3，N＝2，n t ＝2，M＝2；P t ＝3，P＝2，p t ＝2，Q＝2；N r =3, R =2, and n r And (5) =2. As can be seen from the formula (4), the length of one information block is 10bits, and the lengths of three sub information blocks are 4bits,4bits and 2bits respectively.
A progressive coding spatial modulation method based on an intelligent reflector can be implemented through the following four processes:
(1) Transmit end spatial modulation process
Based on the step-by-step coding spatial modulation principle, the sending end selects two active antennas to respectively send s according to a first information sub-block in the information block 1 ,s 2 Wherein s is 1 ,s 2 From Ψ respectively 1 ,Ψ 2 Is selected from (1). The modulation of the transmitting end comprises two steps, in each step, the transmitting end selects one antenna from two antennas as an active antenna, selects one signal from two signals, and uses the active antennaAnd (5) sending. Therefore, there are 2 × 2 × 2 × 2=16 types of transmission patterns on the transmitting side, each pattern is mapped with 4-bit information, and the mapping relationship is shown in table one.
Table one: mapping relation between information bit and sending end sending pattern
(2) Spatial modulation over RIS
According to the second information sub-block in the information block, based on the progressive coding spatial modulation principle, the RIS selects two active virtual antennas, corresponding to two groups of active reflection elements, opens the active reflection elements to reflect signals, and closes the non-reflection elements. At the same time, each group of reflection elements has a phase modulation factor of
From phi, respectively 1 ,Φ 2 To select. Since the RIS can be equivalent to a part of the transmitting end equipped with 3 virtual antennas at this time, as with the transmitting end, there are 2 × 2 × 2 × 2=16 types of RIS-side transmission patterns in total, each pattern is mapped with 4-bit information, and the mapping relationship is as shown in table two.
Table two: mapping relation between information bits and RIS side transmission pattern
(3) Receiver side spatial modulation process
And according to a third information sub-block in the information block, based on a progressive coding space shift keying principle, the receiving end selects two antennas as active antennas. Two sets of active reflecting elements on the RIS serve the two active antennas separately, each forming a beam pointing towards them, thus maximizing the power on the two receiving antennas. The receiving end modulation comprises two steps, and in each step, the receiving end selects one antenna from two antennas as an active antenna. Therefore, there are 2 × 2=4 types of receiving-side transmission patterns in total, each pattern is mapped with 2-bit information, and the mapping relationship is shown in table three.
A third table: mapping relation between information bit and receiving end sending pattern
Through the three processes, joint spatial modulation of a transmitting end, a RIS and a receiving end can be realized, 16 × 16 × 4=1024 joint patterns exist in total, and each joint pattern is mapped with 4+2=10 bits of information.
(4) Detecting a decoding process
When the information bit in the information block is 0001110100, the information bit of the first information sub-block is 0001, and according to the mapping relation of the table one, the sending end selects the first antenna and the second antenna as active antennas to respectively send s 11 ,s 22 Sending a signal vector
Can be expressed as:
x＝[s 11 ,s 22 ,0] T . (17)
the information bit of the second information subblock is 1101, according to the mapping relation of a table two, the RIS selects a second virtual antenna and a third virtual antenna as active antennas, the active antennas correspond to a second group and a third group of reflection elements on the RIS, and the phase modulation coefficients of the second virtual antenna and the third virtual antenna are respectively phase modulation coefficients
Reflection vector
And
can be written as:
and the information bit of the third information subblock is 00, and the first antenna of the receiving end is determined to be the first active antenna and the second antenna is determined to be the second active antenna according to the mapping relation of the table III. Since the number of the third set of reflective elements is greater than the number of the second set of reflective elements on the RIS, the third set of reflective elements serves the first receive antenna and the second set of reflective elements serves the second receive antenna. Reflection vector
Can be written as:
wherein σ k Denotes the k-th reflection element on the RIS at theta 3 The value of (1).
The k-th reflection element on the RIS receives the signal from the transmitting end as
Wherein h is k,i And the element of the k row and the i column in the H represents the channel coefficient from the ith antenna of the transmitting end to the kth reflection element on the RIS.
And the element in the j row and the k column in G represents the channel coefficient from the k reflecting element on RIS to the j antenna at the receiving end. Suppose the k-th on the RISThe reflection element serves the jth antenna at the receiving end, and in order to maximize the signal power on the jth antenna, the value of the kth reflection element on the RIS is:
at this time, the reflection vector
Can be rewritten as:
finally, the signal vector y received by the receiving end is:
y＝G·Θ·H·x+n, (22)
wherein the reflection matrix Θ = Θ 1 ·Θ 2 ·Θ 3 And theta 1 ＝diag(θ 1 ),Θ 2 ＝diag(θ 2 ),Θ 3 ＝diag(θ 3 )。
The maximum likelihood detection algorithm can be expressed as:
after the maximum likelihood detection is carried out at the receiving end, based on the decoding principle of the step-by-step coding spatial modulation, according to the estimated parameters
The original information bits are recovered.
It is to be understood that the present invention has been described with reference to certain embodiments, and that various changes in the features and embodiments, or equivalent substitutions may be made therein by those skilled in the art without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (10)
1. A step-by-step coding spatial modulation method based on an intelligent reflector is characterized by comprising the following steps: the method comprises the following steps of sending end spatial modulation, RIS upper spatial modulation, receiving end spatial modulation and detection decoding:
the method comprises the steps that information bits to be sent are divided into a plurality of information blocks with the same length by a sending end, each information block comprises a plurality of information sub-blocks, and each information sub-block at least comprises a first information sub-block, a second information sub-block and a third information sub-block; the information subblocks are loaded on the sending end, the RIS and the receiving end respectively and sent; based on a progressive coding spatial modulation principle, the sending end selects an active antenna to send signals according to the first information subblock, and spatial modulation of the sending end is achieved;
dividing all elements on the RIS into a plurality of non-uniform groups, wherein each group is used as a virtual antenna; based on a spatial modulation principle, the RIS selects an active virtual antenna according to the second information subblock, a reflection element corresponding to the active virtual antenna selected by the second information subblock is called as an active reflection element, and the active reflection element is opened to reflect an incident signal; the reflection elements corresponding to the virtual antenna which is not selected by the second information subblock are inactive reflection elements, and the inactive reflection elements are closed to realize spatial modulation on the RIS;
determining the index of the active antenna of the receiving end according to the third information sub-block based on a progressive coding space shift keying principle, wherein a group of reflection elements corresponding to each active virtual antenna on the RIS respectively serve each active antenna of the receiving end; and the receiving end recovers the original information bits by adopting a maximum likelihood detection algorithm according to the signal vector received by the receiving end and based on a decoding principle of step-by-step coding spatial modulation.
2. A progressive spatial modulation method according to claim 1, wherein the length of the information block is obtained by the dimension of the total spatial pattern; the length of the information subblocks is obtained through the spatial style dimensions on the sending end, the RIS and the receiving end.
3. A progressive spatial modulation method based on intelligent reflector according to claim 1 wherein when all elements on the RIS are divided into non-uniform groups, the number of elements in each group after division is different from each other.
4. The progressive spatial modulation method according to claim 3, wherein the spatial modulation over the RIS includes spatial domain modulation and constellation domain modulation;
when the space domain modulation is carried out, according to space information bits in the second information subblock, based on a step-by-step coding space modulation principle, selecting a plurality of active virtual antennas, opening a plurality of groups of corresponding active reflection elements to reflect incident signals, and closing non-reflected signals by the non-active reflection elements;
and when the constellation domain modulation is carried out, according to the constellation information bits in the second information subblock, selecting a phase modulation coefficient for a group of active reflection elements corresponding to each active virtual antenna to carry out the constellation domain modulation.
5. A progressive encoding spatial modulation method based on intelligent reflector according to claim 1 characterized in that the number of active virtual antennas on the RIS is the same as the number of active antennas on the receiving end; a group of active reflection element service receiving end first active antennas with the largest number of elements is arranged on the RIS, and the signal power on the first active receiving antenna is maximized by adjusting the phases of all reflection elements in the group to form a beam pointing to the receiving end first active antenna; the other groups of active reflection elements sequentially serve active antennas of the receiving end; the power on the inactive antennas at the receiving end is less than the power on the active antennas.
6. The progressive spatial modulation method according to claim 1, wherein the reflection element on the RIS has an amplitude modulation factor of 1, and the final phase of the active reflection element is the sum of the phase of constellation domain modulation and the beamforming phase on the RIS.
7. A progressive spatial modulation method according to claim 1, wherein said sender is equipped with N t Root antenna, the receiving end is equipped with N r A root antenna, K reflective elements on the RIS, the reflective elements divided into P t Group (d);
the channel matrix from sender to RIS is
The channel matrix from RIS to receiver is
The RIS corresponds to a reflection matrix of Θ = diag (θ), where
The direct path from the sending end to the receiving end is blocked, and the RIS obtains the ideal channel state information.
8. The progressive spatial modulation method according to claim 7, wherein the RIS corresponds to a reflection matrix Θ, and the reflection matrix is composed of three parts:
Θ＝Θ 1 ·Θ 2 ·Θ 3 , (1)
wherein, theta 1 ＝diag(θ 1 )，
θ 1 Determined by the spatial information bits of the second information subblock: when the virtual antenna corresponding to a group of elements on the RIS is an inactive antenna, the group of elements is at θ 1 All values in (1) are 0; when the virtual antenna corresponding to a group of elements on the RIS is an active antenna, the group of elements is at θ 1 All values in (1) are 1;
Θ 2 ＝diag(θ 2 )，
θ 2 the constellation domain information bits of the second information subblock are used for determining: when the virtual antenna corresponding to a group of elements on the RIS is an inactive antenna, the group of elements is at θ 2 All values in (1) are 0; when the virtual antenna corresponding to a group of elements on the RIS is an active antenna, the group of elements is at θ 2 The values in the step (a) are all specific phase modulation coefficients selected for the group based on constellation domain information bits;
Θ 3 ＝diag(θ 3 )，
θ 3 and the third information sub-block determines that: theta when the ith reflecting element on the RIS is an inactive reflecting element 3 The ith element in (1) is 0; when the jth reflection element on the RIS is an active reflection element, theta 3 The value of the jth element is obtained by calculating the power of a specific receiving antenna of a receiving end to the maximum by the grouping of the jth element, and the module value is 1.
9. The progressive spatial modulation method according to claim 7, wherein the signal vectors received by the receiving end are:
y＝G·Θ·H·x+n, (2)
wherein:
y is the vector of the signal received by the receiving end with dimension N r X 1; x is the signal vector sent by the sending end and has the dimension of N t ×1；
N is an additive white Gaussian noise vector with dimension N r X 1, each component obeys a mean of zero and a variance of σ n 2 Complex gaussian distribution.
10. A progressive encoding spatial modulation method according to claim 8 based on intelligent reflector, wherein the maximum likelihood detection algorithm is:
wherein: i | · | live through F Represents a Frobenius norm; x is the number of i The ith sending signal vector is represented and carries the bit information of the first information subblock; theta j The j reflection matrix representing the RIS carries the bit information of the second information sub-block and the third information sub-block;
are each x i And Θ j Estimation under maximum likelihood detection.
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