CN112865893A - Intelligent reflector assisted SM-NOMA system resource allocation method - Google Patents
Intelligent reflector assisted SM-NOMA system resource allocation method Download PDFInfo
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Abstract
The invention relates to an intelligent reflector assisted SM-NOMA system resource allocation method, which belongs to the technical field of communication and comprises the following steps: for the intelligent reflector assisted SM-NOMA system, dynamic user grouping is carried out by considering the effective channel gain of each user; and establishing a power distribution model with the aim of maximizing the system and the speed according to the maximum transmitting power constraint of the base station and the user and the incident signal phase shift constraint of the intelligent reflection unit. The system resource allocation algorithm can effectively improve the system and the rate and reduce the system error rate on the premise of ensuring the maximum difference of each group of user channels.
Description
Technical Field
The invention belongs to the technical field of communication, and relates to an intelligent reflector assisted SM-NOMA system resource allocation method.
Background
With the gradual deployment of 5G network commercialization, 6G communication technologies are also under investigation. An Intelligent Reflection Surface (IRS) is used as a passive reflection array, and by adjusting a wireless propagation environment, the frequency spectrum and energy efficiency of a system are further improved, and meanwhile, energy consumption and hardware cost are reduced, which has attracted extensive attention of people. The intelligent reflecting surface is composed of a large number of small-sized and low-cost reflecting units made of thin-layer electromagnetic materials, is controlled by a programmable intelligent device, and simultaneously realizes the reflection of incident signals by adjusting the phase of the reflecting units. The biggest difference from the traditional communication system is that the propagation environment is improved by the reflection unit, only the propagation direction of the signal is changed, and the amplitude of the incident signal is not influenced. In order to improve the frequency spectrum utilization rate of a cellular network and reduce energy consumption, the service quality of each user is ensured by adjusting the phase offset of an intelligent reflecting surface and the transmitting power of a base station in an intelligent reflecting surface system.
Non-Orthogonal Multiple Access (NOMA) technology is a key technology of 5G. The principle of the technology is as follows: carrying out superposition coding at a transmitting end to form a superposition signal; serial Interference Cancellation (SIC) is performed at the receiving end, and the original signal is recovered. In addition, the NOMA technology allows multiple users to share the same time domain, frequency domain and code domain resources, and realizes multiplexing of the power domain. However, as the number of antennas at the transmitting end of the base station increases, there is a large interference between the antennas. Since the Spatial Modulation (Spatial Modulation) technique has the advantages of low complexity and no inter-antenna interference, the effect of the inter-antenna interference on the system can be reduced, and the Spatial Modulation technique has gradually become a research hotspot in recent years. Resource allocation based on non-orthogonal multiple access plays an important role in wireless communication networks, and each user is guaranteed to have good sum rate by performing power allocation on the base station side.
Currently, research on the combination of intelligent reflective surfaces with NOMA networks has yielded some valuable research results. The document "ZHEN B, WU Q and ZHANG R. Intelligent deflecting surface-assisted multiple access with user pairing: NOMA or OMA [ J ]. IEEE Communications Letters,2020,24(4): 753-. The literature, "DING Z and VINCENTENT POOR H.A Simple design of IRS-NOMA Transmission [ J ]. IEEE Communications Letters,2020,24 (5): 1119-. The documents "SHI Y J, FANG. F, ZHOU X T, et al. Joint beamforming and phase shift design in downlink UAV Networks with IRS-assisted NOMA [ J ]. Journal of Communications and Information Networks,2020,5(2): 138-149" propose a resource allocation problem in the communication scene of IRS assisted unmanned aerial vehicle, considering the joint optimization problem of the beamforming vector at the base station and the phase offset of IRS. And the minimum rate of the edge users is improved and the fairness of the users is ensured through resource allocation. To overcome the hardware limitation, the document "WANG H, LIU C, SHI Z, et al. on power minimization for IRS-aided downlink NOMA systems [ J ]. IEEE Wireless Communications Letters,2020,9(11): 1808-NOMA 1811" designs an IRS-NOMA transmission system, and derives a closed solution of the interruption probability of a single user by controlling IRS through a switch, and the result shows that the Intelligent reflector-Non-Orthogonal frequency division Multiple Access (IRS-NOMA) has better interruption rate capability than the Intelligent reflector-Orthogonal Multiple Access (IRS-OMA). However, the IRS-NOMA system has large interference at the transmitting end, and the receiving end needs a complex SIC detection technology, which affects the overall performance of the system.
To solve the above problems, the spatial modulation based NOMA system starts to receive a great attention from the academic world. The literature "WANG X, WANG J, HE L, et al, on the spatial modulation aid Non-Orthogonal multiple access [ J ]. IEEE Communications Letters,2017,21(9): 1937-. Compared with the traditional NOMA system, the technology has remarkable improvement in spectral efficiency. The document "ZHU X, WANG Z and CAO J. NOMA-based modulation [ J ]. IEEE Access,2017,5(99): 3790-. However, no spatial modulation technique has been studied for the intelligent reflector based NOMA system.
Disclosure of Invention
In view of the above, the present invention aims to provide a resource allocation method for an intelligent reflector-assisted SM-NOMA system, which provides a scheme for dynamic user grouping by considering the effective channel gain (i.e. the sub-channel corresponding to the transmit antenna selected by spatial modulation) of each user. And establishing a power distribution model aiming at maximizing the system and the speed by considering the maximum transmitting power constraint of the base station and the user and the incident signal phase shift constraint of the intelligent reflection unit. Since the constructed problem is a non-convex problem, it is difficult to solve directly. The problem of maximizing the sum rate is first translated into the problem of maximizing the signal to interference plus noise ratio according to the criterion of maximizing the minimum. And then decomposing the original problem into two non-convex sub-problems based on the grouping result: (1) fixing a power distribution coefficient, and converting a non-convex sub problem based on the maximum channel gain into a convex problem by using a semi-definite relaxation algorithm; (2) and fixing the phase shift of the intelligent reflecting surface, and converting the non-convex power distribution subproblem of multiple users into a convex optimization problem to solve by introducing auxiliary variables.
In order to achieve the purpose, the invention provides the following technical scheme:
a resource allocation method of an intelligent reflector assisted SM-NOMA system comprises the following steps:
for the intelligent reflector assisted SM-NOMA system, dynamic user grouping is carried out by considering the effective channel gain of each user; and establishing a power distribution model taking a maximized system and speed as targets according to the maximum transmitting power constraint of the base station and the user and the incident signal phase shift constraint of the intelligent reflection unit.
Further, the intelligent reflecting surface assisted SM-NOMA system comprises a base station transmitting end, an intelligent reflecting surface and a user receiving end; wherein:
the user connectsThe receiving end includes: w users are divided equally into T groups, each group has K users, the channel state information is known; users in each groupm belongs to {1,2,. T } as the serial number of the group, i belongs to {1,2, …, K } as the serial number of the user in the group;
equipping N at the transmitting end of a base stationtA transmitting antenna, a receiving end having NrA root receiving antenna; selecting a transmitting antenna at a transmitting end of a base station through spatial modulation, transmitting a superposed signal at the same time and at the same frequency, reflecting the superposed signal through an intelligent reflector IRS (infrared receiver) and reaching a receiving end of a user;
the IRS consists of N passive reflective elements, each of which changes the phase shift of the incident signal by reflection, thereby assisting NOMA transmission.
Further, at the transmitting end of the base station, the bit stream transmitted by each time slot is divided into two blocks, which are log in total2(Nt)+log2(M) bits; wherein log2(M) bits are used to determine a corresponding transmitted symbol in a signal constellation, where M represents a modulation order; log (log)2(Nt) The bits are used for determining the serial number of the transmitting antenna in the space constellation diagram; the total power of the transmitted signal is P, and the power occupied by each data stream is PWherein the content of the first and second substances,is a userPower allocation factor, the transmitted superimposed signal is:
wherein the content of the first and second substances,representing a userThe serial number of the selected antenna is selected,indicating the modulated transmission symbols.
Further, based on the intelligent reflector assisted SM-NOMA system, a channel is divided into two parts, wherein one part is a direct channel from a base station to a user, and the other part is a reflection channel from the base station to the intelligent reflector to the user; rayleigh fading channels subject to independent equal distribution between base station and user i, i.e.The channel of the base station-intelligent reflecting surface is a Rice channel, and the channel vector isWherein N is the number of intelligent plane of reflection, then:
wherein eta is1Is the rayleigh fading coefficient of the channel f,anddirect-view path and non-direct-view path, respectively;each element in (a) is independent and follows a distribution with a mean of 0 and a variance of 1;
the phase shift matrix theta of the intelligent reflecting surface is expressed by a diagonal matrix, namelyWherein theta isn∈[0,2π](ii) a Intelligent reflecting surface to userIs a channel ofUser' sThe channel description of (c) is:
the channel gain order is:andrayleigh channels representing user 1, user 2, user 3 and user K, respectively, whereinUser' sThe received signals are:
whereinIs a userOf the received signal, n0Is additive white Gaussian noise, obeys a mean value of 0 and has a variance of sigma2Complex Gaussian distribution of jiRepresenting a userIs subject to spatial modulation of the selected jth antenna,representing a userAnd the jth transmit antenna.
Further, the dynamic user grouping comprises the steps of:
user pre-allocation: there are W alternative users, and the user set is divided into 3 types according to the distance between the base station and each user: near users, center users, and far users;
sorting in descending order of users: sorting the alternative users of each initial set in a descending order according to the effective channel gain;
and (3) selecting by the user: and selecting the users with the largest difference of effective channel gains from the corresponding initial set, grouping the users into one group, and returning all grouping conditions until all the users finish grouping. After the optimization of the reflecting surface is finished, carrying out one iteration on the reflecting surface;
the channel gain referenced when users are grouped is: channels before IRS optimization, i.e.First, only one transmitting antenna is selected from IRS-SM-NOMA, and consideration is given toEffective direct channel gain for the ith user, i.e.
Further, the power allocation model targeted to maximize system and rate includes:
each group has K usersWhen decoding the signal, the signal from other weak users is regarded as interference, and the userThe Signal to Interference plus Noise Ratio (SINR) of (1) is expressed as:
according to equation (11), an optimization scheme is adopted to maximize the SINR, i.e. by jointly optimizing the power distribution coefficients of the usersAnd the phase shift Θ of IRS, maximizing user and rate:
optimal maximization-the minimum SINR is Q, where Q is a relaxation variable, i.e.The optimization problem is then transferred to:
under the condition of a given signal-to-noise ratio, the power is assumed to have a determined value to optimize theta so as to achieve the aim of maximizing channel gain; and then, carrying out power distribution according to the number of users in the group, determining beta, and dividing (P1) into two optimization problems to maximize the sum rate of the users, namely a phase shift optimization sub-problem and a power distribution optimization sub-problem.
Further, the phase shift optimization sub-problem comprises:
for the userGiven a fixed power distribution coefficient, and then splitting (P2) into two parts, the channel gain is maximized by optimizing the intelligent reflector phase, starting with the following problem:
let I ═ l1,…,lN]H,And isFurther orderThenTo obtainTherefore (P3)The optimization problem is equivalent to:
(P3) is a problem of non-convex quadratic constraints, restated (P3) as a non-convex homogeneous problem by introducing an auxiliary variable t, (P4) transforms the equivalent write:
wherein the content of the first and second substances,due to the fact thatWhen L satisfies L ≧ 0 andwhen, defineThe first constraint is non-convex, and the semi-definite relaxation (SDR) method is used to relax this constraint, and the problem (P5) is simplified as:
rank of L is reduced to 1 by using semi-deterministic relaxation techniques and gaussian randomization:
(1) decomposing L as characteristic value, L being U ∑ UHWhere U is a unitary matrix and Σ is a diagonal matrix, both of which have dimensions of (N +1) × (N + 1);
(3) to obtainWherein [ X ]](1:N)Represents the vector of [ X ]]The first N elements of (a); obtaining an optimized reflecting surface; by generating enough random variables r, an approximation of (P3) is optimized using the SDR method.
Further, in the power allocation optimization sub-problem, for power allocation of two users, a channel model is a rayleigh channelWherein d isiIs a base station and a userDistance between, path loss is denoted by α;is the Rayleigh fading coefficient, and the noise power of all users is σ2;
For an SM-NOMA system of two users, a sending symbol is a traditional APM symbol, and one antenna is selected at a sending end through spatial modulation, so that the reachable rates of the two users are represented as Rsum=R1+R2:
The power allocation optimization problem of the two users is converted into:
F(β1,β2) SINR for two users, and beta1+β 21 is ═ 1, i.e:
For F (. beta.)1,β2) Beta inside1The partial derivative is calculated and then the first derivative is made equal to 0 as follows:
The power distribution coefficient of the far user isThe power distribution coefficient of the near user is (1-beta)*)。
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.
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For purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a model of an intelligent reflector assisted SM-NOMA communication system;
FIG. 2 is a diagram of two single antenna user systems and rate performance for different signal-to-noise ratios;
fig. 3 is a diagram of the bit error rate performance of two single antenna user systems under different signal-to-noise ratios.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.
Wherein the showings are for the purpose of illustrating the invention only and not for the purpose of limiting the same, and in which there is shown by way of illustration only and not in the drawings in which there is no intention to limit the invention thereto; to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not intended to indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and are not to be construed as limiting the present invention, and it is possible for a person having ordinary skill in the art to understand the specific meaning of the above terms according to specific circumstances.
Consider a multi-user SM-NOMA network downlink communication system model based on intelligent reflective surfaces, as shown in fig. 1. It is assumed that W users are divided equally into T groups, thereby guaranteeing K users per group, and that the channel state information is known. For users in each groupIndicating that the rank of the group is m e {1, 2.. T }, and the rank of the user in the group is i e {1,2, …, K }. Further, assume that N is provided on the base station sidetA transmitting antenna and a receiving end NrThe root receives the antenna. A transmitting antenna is selected at a transmitting end through spatial modulation, a superposed signal is transmitted at the same time and within the same frequency, and the superposed signal is reflected through an IRS and reaches a receiving end. The IRS consists of N passive reflective elements, each of which, by reflection, can change the phase shift of the incident signal, thereby assisting NOMA transmission.
At the transmitting end of the base station, dividing the bit stream transmitted by each time slot into two blocks, wherein the total number is log2(Nt)+log2(M) bits. Wherein log2(M) bits are used to determine a corresponding transmitted symbol in a signal constellation, where M represents a modulation order; log (log)2(Nt) The bits are used to determine the serial number of the transmit antenna in the spatial constellation. Assuming that the total power of the transmitted signal is P, the power occupied by each data stream is P
Wherein the content of the first and second substances,is a userA power allocation factor. Thus, the transmitted superimposed signal can be described as:
wherein the content of the first and second substances,representing a userThe serial number of the selected antenna is selected,indicating the modulated transmission symbols.
Based on an IRS-SM-NOMA system, a channel is divided into two parts, wherein one part is a direct channel from a base station to a user, and the other part is a reflection channel from the base station, an intelligent reflecting surface and the user. Assuming independent identically distributed Rayleigh fading channels between base station and user i, i.e.Assuming that the channel of the base station-intelligent reflecting surface is a Rice channel and the channel vector isWherein N is the number of the intelligent reflecting surfaces, then
Wherein eta is1Is the rayleigh fading coefficient of the channel f,andrespectively a direct-view path and a non-direct-view path.Each element in (a) is independent and follows a distribution with a mean of 0 and a variance of 1. Further, the phase shift matrix theta of the intelligent reflecting surface is expressed by a diagonal matrix, namelyWherein theta isn∈[0,2π]. Intelligent reflecting surface to userIs a channel ofThus usersThe channels of (a) may be described as:
since IRS channels have uncertainty before optimization, it is assumedAnd the order of the channel gains is:herein, theAndrayleigh channels representing user 1, user 2, user 3 and user K, respectively, since here single antenna users are considered, i.e. users with single antennaSo that the userThe received signals are:
herein, theIs a userOf the received signal, n0Is additive white Gaussian noise, obeys a mean value of 0 and has a variance of sigma2Complex gaussian distribution. j is a function ofiRepresenting a userIs subject to spatial modulation of the selected jth antenna,representing a userAnd the jth transmit antenna.
The user grouping algorithm based on the effective channel gain comprises the following steps:
the channel gain referenced when users are grouped is: channels before IRS optimization, i.e.First, only one transmit antenna is selected in the IRS-SM-NOMA, because the effective channel gain is different from the overall channel gain,so only the effective direct channel gain of the ith user needs to be considered, i.e.The steps of grouping users are as follows:
(1) user pre-allocation: assuming that there are W alternative users, according to the distance between the base station and each user, the user set is divided into 3 types: near users, center users, and far users.
(2) Sorting in descending order of users: and each alternative user of the initial set is sorted in a descending order according to the effective channel gain.
(3) And (3) selecting by the user: the users with the largest difference in effective channel gain can be selected from the corresponding initial set to be grouped, and all grouping conditions are returned until all users complete grouping. And after the optimization of the reflecting surface is finished, performing iteration once again.
Constructing a joint optimization model of intelligent reflecting surface phase shift and power distribution:
suppose there are K users per group, usersWhen decoding the signal, the signals from other weak users are regarded as interference, and in this time, the usersThe Signal to Interference Noise Ratio (SINR) of (1) can be expressed as:
in order to maximize the transmission rate of the system while ensuring fairness for each user, an optimization scheme for maximizing SINR (by jointly optimizing power allocation coefficients of users) is adopted according to equation (11)And IRS, to maximize user and rate).
Thus, the optimal maximization is assumed-the minimum SINR is Q, where Q is a relaxation variable, i.e.The optimization problem can be transferred as:
the method comprises the following steps: under the condition of a given signal-to-noise ratio, the power is assumed to have a determined value to optimize theta so as to achieve the purpose of maximizing channel gain; then, power allocation is performed (determining β) according to the number of users in the group, so that (P1) is divided into two optimization problems, and the sum rate of the users is maximized.
Wherein the phase shift optimization sub-problem solving comprises:
in accordance with the foregoing, for the userGiven a fixed power distribution coefficient and then splitting (P2) into two parts, the channel gain can be maximized by optimizing the intelligent reflector phase, starting with the following problem:
let I ═ l1,…,lN]H,And isFurther orderThenThus, can obtainThe optimization problem of (P3) can be equivalent to:
(P3) is a problem of non-convex quadratic constraints, (P3) can be restated as a non-convex homogeneous problem by introducing an auxiliary variable t, so (P4) can be transformed into equivalent write:
wherein the content of the first and second substances,however, it is difficult to solve the problem (P5) directly. Due to the fact thatWhen L satisfies L ≧ 0 andwhen, defineBecause the first constraint is non-convex, the semi-definite relaxation (SDR) method is used to relax this constraint, so the problem (P5) can be simplified as:
it can be seen that (P6) is non-convex, but since rank (l) ≠ 1, the optimal value of (P6) does not satisfy the optimization target of (P3), but only satisfies the upper bound of (P5). Therefore, in order to obtain a condition satisfying the first-stage optimization, the rank of L needs to be reduced to 1, and a semi-definite relaxation technique and a gaussian randomization scheme are adopted:
(1) decomposing L as characteristic value, L being U ∑ UHWhere U is a unitary matrix and Σ is a diagonal matrix, both of which have dimensions of (N +1) × (N + 1).
(2) At this time, the process of the present invention,a random vector can be obtainedWhere r is a random variable, r-CN (0, 1).
(3) Thus can obtainWherein [ X ]](1:N)Represents the vector of [ X ]]The first N elements in (a). An optimized reflecting surface can be obtained. In summary, by generating enough random variables r, an approximation of (P3) can be optimized using the SDR method.
Wherein, the power distribution optimization sub-problem solution comprises two-user power distribution and multi-user power distribution, and the two-user power distribution comprises:
consider first the case where there are two users in a group. Assuming the channel model as a Rayleigh channelWherein d isiIs a base station and a userDistance between, path loss is denoted by α;is the rayleigh fading coefficient. In general, the noise power of all users is σ2。
For the two-user NOMA-SM system, the transmit symbols are conventional APM symbols. When one antenna is selected by spatial modulation at the transmitting end, the reachable rate of two users can be represented as Rsum=R1+R2:
In order to guarantee the service quality of each user and simultaneously realize the maximum sum rate of the users, the power allocation scheme of the double users in the SM-NOMA system is applied to the IRS-SM-NOMA system, but the current selected antenna is only considered for the narrow-band channel gain, and other antennas are not considered. Thus, the power allocation optimization problem for dual users can be translated into:
F(β1,β2) SINR for two users, and beta1+β 21, namely:
by mathematical analysis, for F (. beta.)1,β2) Beta inside1Calculating a deviation, thenLet the first derivative equal 0, as follows:
and c ═ σ2,q=cb2-cb1,p=cb1+c2。
It is obvious thatB is obtained according to the distance relation between the user and the base station1>b2And q is less than 0. Therefore, the temperature of the molten metal is controlled,the feasible region of beta is exceeded, so it is discarded. Therefore, the power distribution coefficient of the far user isThe power distribution coefficient of the near user is (1-beta)*)。
In this embodiment, the validity of the algorithm will be verified by simulation. The proposed IRS-SM-NOMA scheme is verified in simulation in FIG. 2 to be superior to conventional SM-NOMA, SM-OMA, MISO-NOMA, which compared to SM-OMA, demonstrates the effectiveness of the power allocation scheme IRS-SM-NOMA over SM-NOMA because the effective channel gain becomes large.
In FIG. 3, the error rate performance of IRS-SM-NOMA and conventional SM-NOMA are compared. As can be seen from the figure: the error rate of the IRS-SM-NOMA scheme is superior to that of the traditional SM-NOMA scheme.
Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all that should be covered by the claims of the present invention.
Claims (8)
1. An intelligent reflector assisted SM-NOMA system resource allocation method is characterized in that: the method comprises the following steps:
for the intelligent reflector assisted SM-NOMA system, dynamic user grouping is carried out by considering the effective channel gain of each user; and establishing a power distribution model with the aim of maximizing the system and the speed according to the maximum transmitting power constraint of the base station and the user and the incident signal phase shift constraint of the intelligent reflection unit.
2. The intelligent reflector assisted SM-NOMA system resource allocation method according to claim 1, characterized in that: the intelligent reflecting surface assisted SM-NOMA system comprises a base station transmitting end, an intelligent reflecting surface and a user receiving end; wherein:
the user receiving end includes: w users are divided equally into T groups, each group has K users, the channel state information is known; users in each groupIs the serial number of the group, i belongs to {1,2, …, K } is the serial number of the user in the group;
equipping N at the transmitting end of a base stationtA transmitting antenna, a receiving end having NrA root receiving antenna; selecting a transmitting antenna at a transmitting end of a base station through spatial modulation, transmitting a superposed signal at the same time and at the same frequency, reflecting the superposed signal through an intelligent reflector IRS (infrared receiver) and reaching a receiving end of a user;
the IRS consists of N passive reflective elements, each of which, by reflection, changes the phase shift of the incident signal, thereby assisting NOMA transmission.
3. The intelligent reflector assisted SM-NOMA system resource allocation method according to claim 2, characterized in that: at the transmitting end of the base station, dividing the bit stream transmitted by each time slot into two blocks, wherein the total number is log2(Nt)+log2(M) bits; wherein log2(M) bits are used to determine a corresponding transmitted symbol in a signal constellation, where M represents a modulation order; log (log)2(Nt) The bits are used for determining the serial number of the transmitting antenna in the space constellation diagram; the total power of the transmitted signal is P, and the power occupied by each data stream is PWherein the content of the first and second substances,is a userPower allocation factor, the transmitted superimposed signal is:
4. The intelligent reflector assisted SM-NOMA system resource allocation method according to claim 3, characterized in that: based on the intelligent reflector assisted SM-NOMA system, a channel is divided into two parts, wherein one part is a direct channel from a base station to a user, and the other part is a reflection channel from the base station to the intelligent reflector to the user; rayleigh fading channels subject to independent equal distribution from base station to user i, i.e.The channel of the base station-intelligent reflecting surface is a Rice channel, and the channel vector isWherein N is the number of intelligent plane of reflection, then:
wherein eta is1Is the rayleigh fading coefficient of the channel f,anddirect-view path and non-direct-view path, respectively;each element in (a) is independent and follows a distribution with a mean of 0 and a variance of 1;
the phase shift matrix theta of the intelligent reflecting surface is expressed by a diagonal matrix, namelyWherein theta isn∈[0,2π](ii) a Intelligent reflecting surface to userIs a channel ofUser' sThe channel description of (c) is:
the channel gain order is: andrayleigh channels representing user 1, user 2, user 3 and user K, respectively, whereinUser' sThe received signals are:
5. The intelligent reflector assisted SM-NOMA system resource allocation method according to claim 1, characterized in that: the dynamic user grouping comprises the steps of:
user pre-allocation: there are W alternative users, and the user set is divided into 3 types according to the distance between the base station and each user: near users, center users, and far users;
sorting in descending order of users: sorting the alternative users of each initial set in a descending order according to the effective channel gain;
and (3) selecting by the user: selecting the users with the largest difference of effective channel gains from the corresponding initial set to divide the users into a group, and returning all grouping conditions until all the users finish grouping; after the optimization of the reflecting surface is finished, carrying out one iteration on the reflecting surface;
6. The intelligent reflector assisted SM-NOMA system resource allocation method according to claim 1, characterized in that: the power allocation model targeted to maximize system and rate includes:
each group has K usersWhen decoding the signal, the signal from other weak users is regarded as interference, and the userThe signal to interference plus noise ratio SINR of (signal to interference plus noise ratio) is expressed as:
according to equation (11), an optimization scheme is adopted to maximize the SINR, i.e. by jointly optimizing the power allocation coefficients of the usersAnd the phase shift Θ of IRS, maximizing user and rate:
optimal maximization-the minimum SINR is Q, where Q is a relaxation variable, i.e.The optimization problem is then transferred to:
under the condition of a given signal-to-noise ratio, the power is assumed to have a determined value to optimize theta so as to achieve the purpose of maximizing channel gain; and then, carrying out power distribution according to the number of users in the group, determining beta, and dividing (P1) into two optimization problems to maximize the sum rate of the users, namely a phase shift optimization sub-problem and a power distribution optimization sub-problem.
7. The intelligent reflector assisted SM-NOMA system resource allocation method according to claim 6, characterized in that: the phase shift optimization sub-problem comprises:
for the userGiven a fixed power distribution coefficient, and then splitting (P2) into two parts, the channel gain is maximized by optimizing the intelligent reflector phase, starting with the following problem:
let I ═ l1,…,lN]H,And isFurther orderThenTo obtainThe optimization problem of (P3) is equivalent to:
(P3) is a problem of non-convex quadratic constraints, restated (P3) as a non-convex homogeneous problem by introducing an auxiliary variable t, (P4) transforms the equivalent write:
wherein the content of the first and second substances,due to the fact thatWhen L satisfies L ≧ 0 andwhen, defineThe first constraint is non-convex and is relaxed using a semi-deterministic relaxation SDR methodThis constraint, the problem (P5), reduces to:
(P6) is non-convex, processed by reducing the rank of L to 1, by using a semi-deterministic relaxation technique and a gaussian randomization scheme:
(1) decomposing L as characteristic value, L being U ∑ UHWhere U is a unitary matrix and Σ is a diagonal matrix, both of which have dimensions of (N +1) × (N + 1);
8. The intelligent reflector assisted SM-NOMA system resource allocation method according to claim 6, characterized in that: in the power allocation optimization sub-problem, for power allocation of two users, the channel model is a rayleigh channelWherein d isiIs a base station and a userDistance between, path loss is denoted by α;is the Rayleigh fading coefficient, and the noise power of all users is sigma2;
For an SM-NOMA system of two users, a sending symbol is a traditional APM symbol, and one antenna is selected at a sending end through spatial modulation, so that the reachable rates of the two users are represented as Rsum=R1+R2:
The power allocation optimization problem of the two users is converted into:
F(β1,β2) SINR for two users, and beta1+β21, namely:
for F (. beta.)1,β2) Beta inside1The partial derivative is calculated and then the first derivative is made equal to 0 as follows:
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