CN114629539A - RIS-based high-energy-efficiency resource allocation method in multi-user millimeter wave non-orthogonal multiple access system - Google Patents
RIS-based high-energy-efficiency resource allocation method in multi-user millimeter wave non-orthogonal multiple access system Download PDFInfo
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- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
- H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
- H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
- H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/04013—Intelligent reflective surfaces
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- H—ELECTRICITY
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- H04B17/00—Monitoring; Testing
- H04B17/30—Monitoring; Testing of propagation channels
- H04B17/382—Monitoring; Testing of propagation channels for resource allocation, admission control or handover
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- H—ELECTRICITY
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- H04B17/00—Monitoring; Testing
- H04B17/30—Monitoring; Testing of propagation channels
- H04B17/391—Modelling the propagation channel
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
- H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
- H04B7/0842—Weighted combining
- H04B7/086—Weighted combining using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
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Abstract
The invention discloses a high energy efficiency resource allocation method in a multi-user millimeter wave non-orthogonal multiple access system based on RIS, which performs joint optimization on user power allocation, mixed beam forming of a base station and passive beam forming of a reconfigurable intelligent reflecting surface, maximizes system energy efficiency under the condition of meeting minimum rate constraint, maximum power constraint and constant modulus constraint, and provides a joint optimization algorithm based on alternative optimization to obtain high energy efficiency resource allocation; the joint resource allocation method provided by the invention is effective.
Description
The technical field is as follows:
the invention belongs to the field of mobile communication, relates to a resource allocation method of a mobile communication system, and particularly relates to an energy efficiency optimization method in a multi-user mmWave-NOMA system based on RIS.
Background art:
mobile communication networks gradually step into the 5G era, 5G communication devices gradually come into the market, and in order to achieve exponential growth of system capacity, requirements for Spectrum Efficiency (SE), transmission rate, and time delay are gradually increased. However, if only SE is considered, the high density of mobile devices also puts a great pressure on energy consumption, which is not favorable for promoting the development of green communication. Therefore, in order to achieve both resource utilization and energy consumption reduction, taking EE into consideration, it is necessary to develop and utilize various innovative technologies, such as (mmWave) communication, or combination of NOMA technology, Reconfigurable Intelligent Surface (RIS), and the like.
With the progress and development of mobile communication technology, radio services on the traditional communication frequency band become more and more abundant and gradually saturate, and it is difficult to meet the increasing user requirements. The mmWave working in the high frequency band has a large amount of idle spectrum resources, and the development and utilization of the mmWave spectrum resources become the key point of the current mobile communication network. Compared with the traditional wave band, the mmWave frequency band is wide, and more devices can be supported to access a communication network, so that the transmission rate of the SE and the signal is improved.
The NOMA can provide service for a plurality of users at the same frequency band or the same time slot, thereby realizing the purpose of improving the performance of the communication system. By increasing the number of accessible users, a system employing the NOMA technology has higher resource utilization efficiency, and is considered as a multiple access technology having great potential in a future mobile communication system. Among them, one of the commonly used NOMA techniques is mainly power domain based NOMA. The NOMA technology allocates different powers to each user according to different channel qualities among the users, so that a plurality of data streams are transmitted simultaneously on the same time domain, frequency domain or code domain, in other words, the NOMA can realize simultaneous communication of a plurality of users on the same wireless resource, thereby improving the SE or EE of the system.
The RIS is an emerging technology at the time, and can greatly improve system performance. The RIS is made up of a large number of low cost passive reflective elements, each of which is capable of individually controlling the amplitude and/or phase changes of the incident signal, does not require any radio frequency link and increases SE, enabling dense deployment in wireless networks at low cost.
The invention content is as follows:
aiming at an RIS-assisted mmWave-NOMA system, in order to improve the energy efficiency of the system, the invention maximizes the energy efficiency of all users, jointly optimizes the power distribution of the users, the HBF of a base station and the PBF of the RIS, provides a multi-user energy efficiency optimization method in the RIS-based mmWave-NOMA system, and can obtain a better energy efficiency optimization scheme with polynomial time complexity.
The technical scheme adopted by the invention is as follows: a multi-user RIS-based mmWave-NOMA system energy efficiency optimization method comprises the following steps:
step S1: the multi-user mmWave-NOMA system based on RIS is established and consists of K single-antenna users and one mmWave Base Station (BS), wherein the BS adopts a Hybrid Beam Forming (HBF) framework and is provided with N antennas and NRFStrip radio frequency link, N low noise amplifiers and NNRFA phase shifter, each antenna passing through a low noise amplifier and NRFA phase shifter connected to the radio frequency link; dividing K single-antenna users into G groups, wherein NOMA is adopted in the groups; the HBF of the base station includes an Analog Beamforming (ABF) matrixAnd a digital beamforming matrixDefinition setThe RIS consists of M reflecting elements, the reflecting phase vector of whichWherein theta ism∈[0,2π]Definition set It represents the group of the g-th group,indicating the number of its users and,representing channels between the kth user of the g-th group, BS-RISRIS andmmWave channel betweenAnd BS andmmWave channel betweenIs modeled as a millimeter-wave channel and,indicating that the base station passes through RIS toThe cascade channel of (2);
step S2: after the grouping of the users is performed,the received signal of (a) may be expressed as:
wherein xg,k,pg,kRespectively representThe transmission signal, the power allocation of the network,is BS andthe equivalent channel between the two channels,representing complex white gaussian noise in the received signal, according to the NOMA protocol, in descending order of channel gain for example,has an achievable rate of
Where ζ represents the power amplifier coefficient, PC=PBB+NRFPRF+NNRFPPS+NPLNARepresenting fixed circuit power consumption, PBB,PRF,PPS,PLNARespectively, baseband power consumption, radio frequency link power consumption, phase shifter power consumption and low noise amplifier power consumption, C1Represents a minimum rate constraint, rg,kDenotes the minimum rate, C2For maximum power constraint, PmaxDenotes maximum power consumption, C3、C4Is a normal mode constraint of ABF matrix and PBF vector, C5A decoding condition for successive interference cancellation;
step S3: the optimization problem in the step S2 belongs to a non-convex fractional programming problem, and auxiliary variables are introducedwg=AdgAndthenHas an achievable rate of
Introducing an auxiliary variable gammag,k,ug,k,P and eta, by using penalty function method, the problem is converted into
step S4: aiming at the optimization problem in the step S3, the optimization problem is converted into four sub-problems according to an alternative optimization method: fixing { A, D, theta } solving chi subproblems and adopting SCA algorithm to approximate into
Solving by adopting a convex optimization tool to obtain chiopt(ii) a Fixing { χ, A, D, } to solve theta, and making u equal to theta*,Problem is equivalent to
WhereinGiven u(s-1)The value of u at the s-th iteration of the MM algorithm is then the optimal solution
Whereinλmax(V) represents the maximum eigenvalue of V,to representPhase of (1) isFixing { χ, A, θ } the sub-problem of solving D is
Splitting it into g subproblems and expanding, similar to the PBF subproblem, we can solve:
the invention has the following beneficial effects: the energy efficiency optimization method in the multi-user RIS-based mmWave-NOMA system can effectively improve the energy efficiency of the system. The method fully considers the internal structure of the original optimization problem, firstly introduces auxiliary variables to obtain a punishment form of the original problem, equivalently converts the problem into a beam forming subproblem and a power distribution subproblem which are easier to solve by alternative optimization, provides an energy efficiency optimization algorithm of an AO algorithm, a penalty function method, an SCA, an MM and an RMO algorithm, can converge to a feasible suboptimal solution, and finally obtains an effective energy efficiency optimization scheme.
Description of the drawings:
FIG. 1 is a flow chart of a system in an embodiment of the invention.
FIG. 2 is a diagram of a system in an embodiment of the invention.
FIG. 3 is a simulation graph of the NOMA scheme proposed in the embodiment of the present invention and the conventional OMA.
Fig. 4 is a simulation graph of the proposed PBF scheme and two other optimization schemes in an embodiment of the present invention.
The specific implementation mode is as follows:
the invention will be further described with reference to the accompanying drawings.
First, system model
The model of the system involved in the multi-user RIS-based mmWave-NOMA system of the present invention is shown in FIG. 2, and the system consists of K single-antenna users and onemmWave Base Station (BS) with Hybrid Beamforming (HBF) architecture, N antennas, and N antennasRFStrip radio frequency link, N low noise amplifiers and NNRFA phase shifter, each antenna passing through a low noise amplifier and NRFA phase shifter connected to the radio frequency link; dividing K single-antenna users into G groups, wherein NOMA is adopted in the groups; the HBF of the base station includes an Analog Beamforming (ABF) matrixAnd a digital beamforming matrixDefinition setThe RIS consists of M reflecting elements, the reflecting phase vector of whichWherein theta ism∈[0,2π]Definition setIt represents the group of the g-th group,indicating the number of its users and,representing channels between the kth user of the g-th group, BS-RISRIS andmmWave channel betweenAnd BS andmmWave channel betweenIs modeled as a millimeter-wave channel and,indicating that the base station passes through RIS toThe cascade channel of (2);
wherein xg,k,pg,kRespectively representThe transmission signal, the power allocation of the network,is BS andthe equivalent channel between the two channels,representing complex white gaussian noise in the received signal, according to the NOMA protocol, in descending order of channel gain for example,has an achievable rate of
Second, energy efficiency optimization problem modeling and solving process
In order to improve the energy efficiency of the system, a corresponding maximum energy efficiency optimization problem is established, and the optimization aim is to maximize the energy efficiency of all usersThe system energy efficiency optimization problem is modeled as
Where ζ represents the power amplifier coefficient, PC=PBB+NRFPRF+NNRFPPS+NPLNARepresents the fixed circuit power consumption, PBB,PRF,PPS,PLNARespectively, baseband power consumption, radio frequency link power consumption, phase shifter power consumption and low noise amplifier power consumption, C1Represents a minimum rate constraint, rg,kDenotes the minimum rate, C2For maximum power constraint, PmaxDenotes maximum power consumption, C3、C4Is a normal mode constraint of ABF matrix and PBF vector, C5A decoding condition for successive interference cancellation;
Introducing auxiliary variablesγg,k,ug,k,P and eta, by means of penalty functions, into which the problem is transformed
according to the alternative optimization method, the penalty problem is converted into four sub-problems: fixing { A, D, theta } solving chi subproblems and adopting SCA algorithm to approximate into
Solving by adopting a convex optimization tool to obtain chiopt(ii) a Fixing { χ, A, D, } to solve theta, and making u equal to theta*,Problem is equivalent to
WhereinGiven u(s-1)The value of u at the s-th iteration of the MM algorithm is then the optimal solution
Whereinλmax(V) represents the maximum eigenvalue of V,to representPhase of (1) isFixing { χ, A, θ } the sub-problem of solving D is
Splitting the problem into g subproblems and expanding the problem, similar to the PBF subproblem, a solution can be obtained:
in summary, the invention provides an energy efficiency optimization algorithm using a penalty function method, an alternative optimization algorithm, a continuous convex approximation algorithm and an MM algorithm, and the energy efficiency of the algorithm provided by the invention is verified through Matlab simulation. Wherein the base station and the RIS are located at (0m, 0m) and (80m, 5m), respectively. All users are uniformly distributed in a range which takes (150m, 0m) as a center and 5m as a radius, the carrier frequency of the base station is 28GHz, and default parameter settings are listed in the following table:
FIG. 3 compares the energy efficiency performance of the NOMA scheme proposed by the present invention, which is exemplified by time division multiple access, with the conventional OMA scheme, in which "NOMA scheme" represents the energy efficiency optimization scheme proposed by the present invention; the 'TDMA scheme' means that a TDMA technology is adopted to maximize energy efficiency, the executed user grouping strategy is the same as the algorithm 'NOMA scheme', and users in each group are accessed in a time division multiple access mode with equal time slots. It can be seen from the figure that the NOMA-based algorithm achieves EE significantly better than the TDMA-based algorithm, thereby illustrating the advantages of the NOMA technique.
FIG. 4 is a graph comparing the RIS-mmWave-NOMA system energy efficiency performance under different PBF optimization algorithms proposed by the present invention. The PSO algorithm-based PSO PBF, Random PBF based on Random phase and the algorithm 'Designed PBF' proposed by the invention are included. As can be seen from the figure, the EE performance obtained by the PBF algorithm adopted by the invention is close to that of the PSO PBF, the complexity of the particle swarm optimization is higher, and the EE obtained by the Random PBF is lowest, because the PBF of the Random PBF is randomly generated and is not subjected to joint optimization, and the result shows the effectiveness of the proposed PBF algorithm.
In conclusion, the energy efficiency method provided by the invention can effectively improve the energy efficiency performance of the RIS-assisted mmWave-NOMA system, and meanwhile, the steps for realizing the method are simple, so that the effectiveness of the energy efficiency optimization method in the multi-user RIS-based mmWave-NOMA system provided by the invention is fully demonstrated.
The foregoing is only a preferred embodiment of this invention and it should be noted that modifications can be made by those skilled in the art without departing from the principle of the invention and these modifications should also be considered as the protection scope of the invention.
Claims (1)
1. A multi-user millimeter wave mmWave non-orthogonal multiple access system NOMA high energy efficiency resource allocation method based on reconfigurable intelligent reflecting surface RIS is characterized in that: the method comprises the following steps:
step S1: the multi-user mmWave-NOMA system based on RIS is established, and consists of K single-antenna users and an mmWave base station BS, wherein the base station adopts a hybrid beam forming HBF framework and is provided with N antennas and NRFStrip radio frequency link, N low noise amplifiers and NNRFA phase shifter, each antenna passing through a low noise amplifier and NRFA phase shifter connected to the radio frequency link; dividing K single-antenna users into groups, wherein NOMA is adopted in each group; HBF of base station includes analog beamforming ABF matrixAnd a digital beamforming matrixWherein N issRepresenting the number of data streams; definition setDue to the analog beamformer, A satisfies a constant modulus constraint, i.e.And, users are divided into G groups, and in order to guarantee spatial multiplexing gain, G ═ N is sets≤NRFWhen D is ═ D1,...,dG]WhereinThe RIS consists of M reflecting elements, the reflecting phase vector of whichCorresponding reflection phase matrix isWherein theta ism∈[0,2π]Definition set It represents the group of the g-th group,indicating the number of its users and,representing channels between the kth user of the g-th group, BS-RISRIS andmmWave channel betweenAnd BS andmmWave channel betweenIs modeled as a millimeter-wave channel and,indicating that the base station passes through RIS toThe cascade channel of (2);
step S2: establishing an energy efficiency optimization problem under given constraint conditions, wherein the optimization target is to maximize the system energy efficiencyOptimizing the transmission power p of a variable to a userg,kThe HBF of the base station and the passive beamforming PBF vector of the RIS are optimized and constrained to the minimum speed and the maximum power of a user, the normal mode constraint of an ABF matrix, the normal mode constraint of the PBF vector and the decoding condition of serial interference elimination; wherein R isg,kFor the userIs the achievable rate, ξ represents the power amplifier coefficient, PCExpressed as fixed circuit power consumption;
step S3: the optimization problem in the step S2 belongs to a non-convex fractional programming problem, and auxiliary variables are introducedAnd using a penalty function method to constrain the equation to wg=AdgAndtransferring to a target function to obtain a punishment form of the problem;
step S4: aiming at the optimization problem in the step S3, letIt is decomposed into a series of sub-problems using alternating optimization: fixing { A, D, theta } solves the sub-problem of χ, fixing { χ, A, D } solves the sub-problem of theta, fixing { χ, A,theta solves the subproblem of D and the subproblem of A by fixing x, D and theta, and the subproblems are respectively solved by using a continuous convex approximation algorithm, an optimization minimization algorithm, a derivation algorithm and an alternative optimization algorithm in sequence, and a corresponding optimization algorithm is given;
step S5: and based on the obtained solution of the optimization variable, providing a high-energy-efficiency joint resource allocation method.
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CN115426024B (en) * | 2022-11-03 | 2023-01-10 | 鹏城实验室 | Phase adjusting method of intelligent reflecting surface capable of spatial multiplexing |
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