阅读说明：本技术 一种基于智能反射面的功率域noma通信系统设计方法 (Power domain NOMA communication system design method based on intelligent reflecting surface ) 是由 岳新伟 刘元玮 李学华 刘荣科 康绍莉 于 2020-12-25 设计创作，主要内容包括：本发明属于无线通信技术领域,本发明提出一种智能反射面辅助的功率域NOMA通信系统设计方法,通过引入超材料智能反射面来协助基站发送信息给非正交用户,所述设计方法包括建立智能反射面辅助NOMA系统模型、给出用户接收信号表达式和检测信噪比,提出1-bit编码随机相移机制将智能反射面的连续相移转变为随机相移,通过“1”和“0”开关对反射单元进行控制,推导出用户的中断概率理论表达式。本发明方法相对于传统译码转发中继、放大转发中继以及智能反射面辅助的OMA系统,提高了中断概率性能和系统频谱效率,具有较好的应用价值。(The invention belongs to the technical field of wireless communication, and provides a design method of an intelligent reflecting surface assisted power domain NOMA communication system, which assists a base station to send information to a non-orthogonal user by introducing a metamaterial intelligent reflecting surface, wherein the design method comprises the steps of establishing an intelligent reflecting surface assisted NOMA system model, giving a user received signal expression and a detection signal-to-noise ratio, providing a 1-bit coding random phase shift mechanism to convert continuous phase shift of an intelligent reflecting surface into random phase shift, controlling a reflecting unit through a '1' switch and a '0' switch, and deducing an interruption probability theoretical expression of the user. Compared with the traditional OMA system with decoding forwarding relay, amplifying forwarding relay and intelligent reflecting surface assistance, the method improves the interrupt probability performance and the system spectrum efficiency and has better application value.)

1. A design method of a power domain NOMA communication system based on an intelligent reflecting surface is characterized in that: the method comprises the following steps:

the method comprises the following steps: establishing an intelligent reflector auxiliary power domain NOMA communication system model, and writing a receiving signal expression of a user;

step two: the near-end user deletes the signal of the far-end user by using serial interference deletion and then detects the signal of the near-end user; the far-end user directly takes the signal of the near-end user as an interference decoding self signal;

step three: processing the user detection signal-to-interference-and-noise ratio given in the second step, and converting the continuous phase shift of the intelligent reflecting surface into random phase shift by using a 1-bit coding mechanism;

step four: and defining the interruption events of users in the intelligent reflector auxiliary power domain NOMA communication system, and deducing the interruption probability closed solution expression of non-orthogonal users.

2. The design method of the intelligent reflecting surface-based power domain NOMA communication system, according to claim 1, is characterized in that: the communication system specifically comprises a base station, an intelligent reflecting surface and M ground users, wherein the base station sends the superposed information of the M users to the ground users under the assistance of the intelligent reflecting surface, and a communication link between the base station and the users in the system is blocked by a building and cannot be directly communicated with each other, but can be completed only through the assistance of the reflecting surface;

the intelligent reflecting surface comprises K reflecting units, and the complex channel coefficients from the base station to the reflecting surface and from the reflecting surface to the mth user are respectively used by h_srAnd h_rmExpressed and modeled as a rayleigh fading channel. Without loss of generality, the cascade channel gains from the base station to the intelligent reflecting surface and then to the user are sequenced, that is to sayIs a diagonal matrix, beta is an element [0,1 ]]Denotes the fixed magnified reflectance, θ, of the reflecting surface_kE [0,2 π) represents the phase shift of the kth reflecting element; at this time, the reception signal of the mth user can be expressed as

Wherein x is_iNormalized energy signal representing the ith user, a_iRepresents the power distribution factor of the ith user and satisfies the relation a₁≥a₂≥…a_m≥…≥a_MAndP_srepresents the normalized transmit power at the base station,whereinRepresenting the complex channel coefficients from the base station to the k-th reflecting element,wherein the content of the first and second substances,representing the complex channel coefficient, n, from the k-th reflecting unit to the m-th user_mRepresenting white gaussian noise at the mth user.

3. The design method of the intelligent reflecting surface-based power domain NOMA communication system, according to claim 1, is characterized in that: the second step specifically comprises: according to the NOMA decoding order criterion, the corresponding signal-to-interference-and-noise ratio when the near-end user (mth user) decodes the far-end user (qth user) signal is expressed as

Wherein the content of the first and second substances,indicating the signal-to-noise ratio at the transmitting end,in particular whenAndrespectively indicating that the mth user uses an ideal serial interference deletion mechanism and a non-ideal serial interference deletion mechanism;

for the Mth user, the SINR after deleting the previous M-1 users using the successive interference deletion mechanism can be expressed as

4. The design method of the intelligent reflecting surface-based power domain NOMA communication system, according to claim 1, is characterized in that: the third step specifically comprises:

from the analysis of an application angle, continuously changing the amplitude and the phase of a reflecting unit of an intelligent reflecting surface is beneficial to enhancing the network performance, but an accurately designed and expensive hardware architecture is needed, which brings higher cost to the deployment of the intelligent reflecting surface, the intelligent reflecting unit can be realized by embedding a PIN diode on the surface of each element, the bias voltage of the intelligent reflecting surface is controlled by a direct current feed line, the state is equivalent to switching between a state of '1' (on) and a state of '0' (off) so as to generate a phase difference, a variable resistance load can be used for effectively controlling a reflection amplification factor, the randomness of the reflection phase and the amplification factor on the intelligent reflecting surface is realized by programmable software control, the random phase shift control on the intelligent reflecting surface is realized by using a 1-bit coding random phase shift strategy, and the specific realization process is as follows: definition ofWhere K is PQ, P and Q are integers, I_PIs a P × P unit array, 1_QIs a Q x 1 column vector with elements all being 1，Expressed as the inner product of Kronecker, v_pColumn p (dimension K × 1) representing V, it can be seen that under the condition of p ≠ l,by simple arithmetic operations, randomly selecting a column v_pThe detection signal-to-interference-and-noise ratio of the user is maximized, so that the purpose of enhancing the communication performance of the user is realized; after using the 1-bit coding method, the signal-to-interference-and-noise ratio when the mth user decodes the qth user signal can be expressed as:

the SINR of the Mth user decoding its signal can be expressed as

5. The design method of the intelligent reflecting surface-based power domain NOMA communication system, according to claim 1, is characterized in that:

the fourth step specifically comprises: when the mth user cannot detect that the communication interruption occurs to the information of the qth user, the corresponding interruption event can be written as:

further, the interruption probability of the mth user is represented by a complementary event as follows:

P_m＝Pr[min(E_m,1,E_m,2,…,E_m,m)] (6)

the expressions of the interruption probability of the mth user under the non-ideal/ideal successive interference cancellation mechanism can be obtained through theoretical derivation, and are respectively:

wherein the content of the first and second substances, and is R_mRepresenting the m-th user detection signal x_mThe target rate of time.Weighting coefficient, r, representing the Gauss-Laguerre integral_uRespectively zero of the laguerre polynomials. U represents a compromise parameter between complexity and accuracy.

Technical Field

The invention relates to a design method of a power domain NOMA communication system based on an intelligent reflecting surface, belongs to the technical field of wireless communication, and particularly relates to a 1-bit coding method for converting continuous phase shift of reflection on the reflecting surface into random phase shift.

Background

With the rapid increase of the mobile communication data service demand, higher requirements are put forward on key technical indexes such as spectrum efficiency, user connection density and the like of the next generation mobile communication system. Multiple access has historically received much attention as a landmark technology for the evolution of mobile communication systems. The traditional OMA scheme is adopted from the first generation to the fourth generation, that is, the degree of freedom of wireless resources in the time domain, the frequency domain or the space domain is limited by the orthogonality of the access scheme. This not only results in inefficient use of radio resources, but also limits the number of users accessing it. In the face of explosive increase of wireless communication traffic and wireless device access volume, the power domain NOMA technology can effectively improve the spectrum efficiency and user connection density of a wireless communication system, and has become one of the key technologies of the next generation communication network.

As an emerging wireless technology, the intelligent reflecting surface is an artificial electromagnetic surface structure with programmable electromagnetic characteristics, which is used for designing coded metamaterials by arranging a group of small scattering or aperture in a regular array in the whole space region, and can be applied to various frequency bands from microwave to visible light. The programming control is carried out by means of the digital sequence, the real-time regulation and control of electromagnetic parameters such as the amplitude, the phase position, the frequency and the like of electromagnetic waves are realized, the reconfiguration of a wireless transmission environment is completed, and the borrowing of the physical electromagnetic world of the intelligent reflecting surface and the digital world of information science is provided. The intelligent reflecting surface can break through the uncontrollable limitation of the traditional wireless channel, realize the regulation, enhancement or elimination of the signal propagation direction in a three-dimensional space, inhibit interference and enhance signals, and can be proved to be used as an electromagnetic relay to improve the system performance of a network. The use of the intelligent reflecting surface brings new communication resource dimensionality and shows strong advantages in the aspects of improving system throughput, diversity gain and the like. Currently, the intelligent transmitting surface auxiliary NOMA wireless communication becomes a research hotspot of academic circles.

Disclosure of Invention

The invention aims to introduce an intelligent reflecting surface into a power domain NOMA system, fully excavate and utilize limited communication resources of the system and design an efficient communication transmission scheme.

A design method of a power domain NOMA communication system based on an intelligent reflecting surface comprises the following steps:

the method comprises the following steps: establishing an intelligent reflector auxiliary power domain NOMA communication system model, and writing a receiving signal expression of a user;

step two: the near-end user deletes the signal of the far-end user by using serial interference deletion and then detects the signal of the near-end user; the far-end user directly takes the signal of the near-end user as an interference decoding self signal;

step three: processing the user detection signal-to-interference-and-noise ratio given in the second step, and converting the continuous phase shift of the intelligent reflecting surface into random phase shift by using a 1-bit coding mechanism;

step four: and defining the interruption events of users in the intelligent reflector auxiliary power domain NOMA communication system, and deducing the interruption probability closed solution expression of non-orthogonal users.

Further, the communication system specifically comprises a base station, an intelligent reflecting surface and M ground users, wherein the base station sends the superposed information of the M users to the ground users under the assistance of the intelligent reflecting surface, and a communication link between the base station and the users in the system is blocked by a building and cannot be directly communicated with the ground users, but can be completed only through the assistance of the reflecting surface;

assuming that the intelligent reflecting surface comprises K reflecting units, the complex channel coefficients from the base station to the reflecting surface and from the reflecting surface to the mth user are respectively h_srAnd h_rmIndicating that the cascade channel gains from the base station to the intelligent reflecting surface and then to the user are sequenced without loss of generality, that is to say Is a diagonal matrix, beta is an element [0,1 ]]Denotes the fixed magnified reflectance, θ, of the reflecting surface_kE [0,2 π) represents the phase shift of the kth reflecting element; at this time, the received signal of the mth user can be expressed as:

wherein x is_iNormalized energy signal representing the ith user, a_iRepresents the power distribution factor of the ith user and satisfies the relation a₁≥a₂≥…a_m≥…≥a_MAndP_srepresents the normalized transmit power at the base station,whereinRepresenting the complex channel coefficients from the base station to the k-th reflecting element,wherein the content of the first and second substances,representing the complex channel coefficient, n, from the k-th reflecting unit to the m-th user_mRepresenting white gaussian noise at the mth user.

Further, the second step specifically comprises: according to the NOMA decoding order criterion, the corresponding signal-to-interference-and-noise ratio when the near-end user (mth user) decodes the far-end user (qth user) signal is expressed as:

wherein the content of the first and second substances,indicating transmit end signal-to-noiseThe ratio of the amount of the acid to the amount of the water,in particular whenAndrespectively indicating that the mth user uses an ideal serial interference deletion mechanism and a non-ideal serial interference deletion mechanism;

for the mth user, the sir after deleting the previous M-1 users using the successive interference cancellation mechanism can be expressed as:

further, the third step specifically comprises:

from the practical application perspective, continuously changing the amplitude and phase of the reflection unit of the intelligent reflection surface is beneficial to enhancing the network performance, but requires a precisely designed and expensive hardware architecture, which brings higher cost to the deployment of the intelligent reflection surface, the intelligent reflection unit can be realized by embedding a PIN diode on the surface of each element, the bias voltage is controlled by a direct current feed line, equivalently, the state is switched between a state of "1" (on) and a state of "0" (off) so as to generate a phase difference, a variable resistance load can be used for effectively controlling a reflection amplification factor, so that the randomness of the reflection phase and the amplification factor on the intelligent reflection surface is realized by programmable software control, and the random phase shift control on the intelligent reflection surface is realized by using a 1-bit coding random phase shift strategy, and the specific realization process is as follows: definition ofWhere K is PQ, P and Q are integers, I_PIs a P × P unit array, 1_QIs a Q x 1 column vector with elements all 1,expressed as the inner product of Kronecker, v_pColumn p (dimension K × 1) representing V, it can be seen that under the condition of p ≠ l,by simple arithmetic operations, randomly selecting a column v_pAfter a 1-bit coding strategy is used, the SINR when the mth user decodes the qth user signal can be expressed as:

the signal-to-interference-and-noise ratio of the mth user decoding its own signal can be expressed as:

further, the fourth step specifically includes: when the mth user cannot detect that the communication interruption of the information of the qth user occurs, the corresponding interruption event can be written as a communication interruption event by using a mathematical expression

Further, the interruption probability of the mth user is represented by a complementary event as follows:

P_m＝Pr[min(E_m,1,E_m,2,…,E_m,m)] (6)

further, the expressions of the interruption probability of the mth user under the non-ideal/ideal successive interference cancellation mechanism can be obtained through theoretical derivation, and are respectively:

wherein the content of the first and second substances, and is R_mRepresenting the m-th user detection signal x_mThe target rate of time.Weighting coefficient, r, representing the Gauss-Laguerre integral_uRespectively zero of the laguerre polynomials. U represents a compromise parameter between complexity and accuracy.

The technical effects are as follows:

the invention uses 1-bit coding method to convert continuous reflection amplitude and phase shift into discrete form in power domain NOMA communication system based on intelligent reflector, which is convenient to provide maximum detection signal-to-noise ratio of non-orthogonal user, and easy to solve interruption probability expression of user.

Drawings

FIG. 1 is a model diagram of a power domain NOMA communication system based on an intelligent reflecting surface according to the invention;

FIG. 2 is a graph comparing interrupt performance for the intelligent reflector auxiliary power domain NOMA, the intelligent reflector auxiliary OMA, and a conventional cooperative communication system;

FIG. 3 is a graph comparing interruption performance of a NOMA system under a non-ideal/ideal successive interference cancellation scheme;

FIG. 4 is a schematic diagram of the impact of the deployment position of a reflecting surface between a base station and a user on interruption performance in an intelligent reflecting surface auxiliary power domain NOMA system;

FIG. 5 is a flow chart of a design method of an intelligent reflector assisted power domain NOMA communication system.

Detailed Description

The present invention is further described with reference to the following examples and the accompanying drawings, which are not intended to limit the scope of the invention as claimed.

The invention aims to introduce an intelligent reflecting surface into a power domain NOMA system, fully excavate and utilize limited communication resources of the system and design an efficient communication transmission scheme.

Firstly, modeling a power domain NOMA system model based on an intelligent reflecting surface, and providing a received signal expression, a detection signal-to-noise ratio and a signal-to-interference-and-noise ratio of a non-orthogonal user; then, converting the continuous phase shift of the reflecting surface into discrete phase shift by using a 1-bit coding method, and solving the optimal detection signal-to-noise ratio and the signal-to-interference-and-noise ratio of the mth user under the discrete phase shift; and finally, defining the interruption event of the user according to the optimal detection signal-to-noise ratio and the signal-to-interference-and-noise ratio and deducing an interruption probability expression under an ideal/non-ideal serial interference deletion mechanism. Compared with the traditional decoding forwarding relay, the amplifying forwarding relay and the OMA system assisted by the intelligent reflecting surface, the method improves the interrupt probability performance, reduces the cost of the intelligent reflecting surface in actual deployment, and is simple and easy to operate.

A design method of a power domain NOMA communication system based on an intelligent reflecting surface comprises the following steps:

the method comprises the following steps: establishing an intelligent reflector auxiliary power domain NOMA communication system model, and writing a receiving signal expression of a user;

step two: the near-end user deletes the signal of the far-end user by using serial interference deletion and then detects the signal of the near-end user; the far-end user directly takes the signal of the near-end user as an interference decoding self signal;

step three: processing the user detection signal-to-interference-and-noise ratio given in the second step, and converting the continuous phase shift of the intelligent reflecting surface into random phase shift by using a 1-bit coding mechanism;

step four: and defining the interruption events of users in the intelligent reflector auxiliary power domain NOMA communication system, and deducing the interruption probability closed solution expression of non-orthogonal users.

Further, the communication system specifically comprises a base station, an intelligent reflecting surface and M ground users, wherein the base station sends the superposed information of the M users to the ground users under the assistance of the intelligent reflecting surface, and a communication link between the base station and the users in the system is blocked by a building and cannot be directly communicated with the ground users, but can be completed only through the assistance of the reflecting surface;

assuming that the intelligent reflecting surface comprises K reflecting units, the complex channel coefficients from the base station to the reflecting surface and from the reflecting surface to the mth user are respectively h_srAnd h_rmIndicating that the cascade channel gains from the base station to the intelligent reflecting surface and then to the user are sequenced without loss of generality, that is to say Is a diagonal matrix, beta is an element [0,1 ]]Denotes the fixed magnified reflectance, θ, of the reflecting surface_kE [0,2 π) represents the phase shift of the kth reflecting element; at this time, the received signal of the mth user can be expressed as:

wherein x is_iNormalized energy signal representing the ith user, a_iRepresents the power distribution factor of the ith user and satisfies the relation a₁≥a₂≥…a_m≥…≥a_MAndP_srepresents the normalized transmit power at the base station,whereinRepresenting the complex channel coefficients from the base station to the k-th reflecting element,wherein the content of the first and second substances,representing the complex channel coefficient, n, from the k-th reflecting unit to the m-th user_mRepresenting white gaussian noise at the mth user.

Further, the second step specifically comprises: according to the NOMA decoding order criterion, the corresponding signal-to-interference-and-noise ratio when the near-end user (mth user) decodes the far-end user (qth user) signal is expressed as:

wherein the content of the first and second substances,indicating the signal-to-noise ratio at the transmitting end,in particular whenAndrespectively indicating that the mth user uses an ideal serial interference deletion mechanism and a non-ideal serial interference deletion mechanism;

for the mth user, the sir after deleting the previous M-1 users using the successive interference cancellation mechanism can be expressed as:

further, the third step specifically comprises:

from the practical application perspective, continuously changing the amplitude and phase of the reflection unit of the intelligent reflection surface is beneficial to enhancing the network performance, but requires a precisely designed and expensive hardware architecture, which brings higher cost to the deployment of the intelligent reflection surface, the intelligent reflection unit can be realized by embedding a PIN diode on the surface of each element, the bias voltage is controlled by a direct current feed line, equivalently, the state is switched between a state of "1" (on) and a state of "0" (off) so as to generate a phase difference, a variable resistance load can be used for effectively controlling a reflection amplification factor, so that the randomness of the reflection phase and the amplification factor on the intelligent reflection surface is realized by programmable software control, and the random phase shift control on the intelligent reflection surface is realized by using a 1-bit coding random phase shift strategy, and the specific realization process is as follows: definition ofWhere K is PQ, P and Q are integers, I_PIs a P × P unit array, 1_QIs an element of all 1The number of column vectors is such that,expressed as the inner product of Kronecker, v_pColumn p (dimension K × 1) representing V, it can be seen that under the condition of p ≠ l,by simple arithmetic operations, randomly selecting a column v_pAfter a 1-bit coding strategy is used, the SINR when the mth user decodes the qth user signal can be expressed as:

the signal-to-interference-and-noise ratio of the mth user decoding its own signal can be expressed as:

the fourth step specifically comprises: when the mth user cannot detect that the communication interruption occurs to the information of the qth user, the corresponding interruption event can be written as:

further, the interruption probability of the mth user is represented by a complementary event as follows:

P_m＝Pr[min(E_m,1,E_m,2,…,E_m,m)] (6)

further, the expressions of the interruption probability of the mth user under the non-ideal/ideal successive interference cancellation mechanism can be obtained through theoretical derivation, and are respectively:

wherein the content of the first and second substances, and isR_mRepresenting the m-th user detection signal x_mThe target rate of time.Weighting coefficient, r, representing the Gauss-Laguerre integral_uRespectively zero of the laguerre polynomials. U represents a compromise parameter between complexity and accuracy.

The invention provides a power domain NOMA communication system based on an intelligent reflecting surface. The interruption probability performance of the intelligent reflector auxiliary power domain NOMA communication system is verified through simulation. Suppose that there are three users, user 1, user 2 and user 3, in the system, and their corresponding power factors are set as a₁＝0.5、a₂0.4 and a₃The target rates are set to R, 0.1, respectively₁＝0.6、R₂1.6 and R₃2 BPCU; without loss of generality, the distance from the base station to the user is normalized to 1, parameterAndwherein d is_sr、d_r1、d_r2And d_r3Respectively, the distances from the base station to the reflecting surface and from the reflecting surface to the three users, and alpha represents a path loss index.

In the power domain NOMA communication system based on the intelligent reflecting surface, the interruption probability of a user under the condition of using non-ideal/ideal serial interference deletion can be calculated according to the equations (7) and (8). As can be seen from fig. 2, the interrupt performance of three users of the intelligent transmitting surface auxiliary power domain NOMA system is superior to that of the traditional transcoding forwarding relay, the amplifying forwarding relay and the intelligent reflecting surface auxiliary OMA system. The main reasons for this phenomenon are: for a plurality of users, the intelligent reflecting surface-based power domain NOMA communication system can achieve better user fairness compared with an OMA system; (2) because the full-duplex decoding forwarding relay is influenced by a loop interference signal, an advanced loop interference elimination technology is required to be used, and the cost is higher; (3) compared with the decoding forwarding relay working in the half-duplex mode, the power domain NOMA system based on the intelligent reflecting surface works in the full-duplex mode and is not influenced by loop interference, and the frequency spectrum efficiency is higher.

Fig. 3 presents a comparison of outage probability performance using non-ideal/ideal successive interference cancellation conditions for users of a power domain NOMA communication system based on intelligent reflective surfaces. As can be seen, user 2 and user 3 have better outage performance than non-ideal serdes under conditions where ideal serdes are used. In addition, as the interference value is increased, the interruption probability of the user is increased. This is mainly because the non-ideal serial interference cancellation process is affected by factors such as error propagation.

Fig. 4 presents the effect of the deployment location of the reflective surfaces of a smart reflective surface-based power domain NOMA communication system on user interruption performance. The results show that when the intelligent reflecting surface is deployed at the base station and the user side, the interruption performance of the non-orthogonal user is the best. This phenomenon can be explained as when the reflecting surface is deployed near the base station, the received direct path signal from the base station can be totally reflected to the user; when the position of the reflecting surface is gradually far away from the base station, the interruption performance of the user is gradually deteriorated due to the deterioration of the direct path signal, and when the reflecting surface is between the base station and the user, the interruption performance of the user is the worst; when the arrangement of the reflecting surface is gradually close to the user side, the signal received by the user is enhanced, and better user interruption performance is brought.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.