CN112087791A - Optimal power distribution method and system - Google Patents

Abstract

The invention relates to an optimal power distribution method and a system, wherein the method comprises the steps of firstly, establishing a multi-user TWR-AF cooperation time division duplex system which operates in a half-duplex mode, and respectively analyzing an accumulative probability density function of a signal and interference plus noise ratio processed by a base station and a selected mobile station under the conditions of channel estimation error and outdated channel state information by mainly considering the multi-user TWR-AF cooperation time division duplex system with adaptive modulation. Then, an accurate approximate form of the average spectrum efficiency and the interruption probability is obtained, and the progressive performance of the self-adaptive system is further provided. And finally, based on the criterion of maximizing the approximate average throughput, an optimal power distribution scheme is provided, and the influence of channel estimation errors and outdated channel state information is reduced. Numerical results show that the power distribution scheme provided by the invention is superior to the common power distribution scheme.

Description

Optimal power distribution method and system

Technical Field

The invention relates to an optimal power distribution method and system, and belongs to the technical field of communication.

Background

In modern wireless communication networks, higher throughput is increasingly required while ensuring the required quality of service. Adaptive bi-directional relaying is a promising technique to meet such demands because it can overcome the spectral efficiency loss due to half-duplex transmission and adaptively select modulation and coding levels according to time-varying channel conditions.

In the signal transmission process, no matter what kind of transmission is, the source end needs to perform self-interference elimination on the received signal to obtain the signal of the opposite side, but in an actual communication system, the influence of channel estimation errors and outdated channel state information on the performance of a multi-user TWR-AF system with adaptive modulation is not solved.

Disclosure of Invention

The purpose of the invention is as follows: the method and the system for reducing the influence of the system performance caused by the channel estimation error are provided to solve the problems in the prior art, and the further aim is to provide a criterion based on the maximized approximate average throughput, provide an optimal power distribution scheme and reduce the influence of the channel estimation error and the outdated channel state information.

The technical scheme is as follows: an optimal power distribution method and system, wherein the optimal power distribution method comprises the following steps:

step one, establishing a multi-user TWR-AF cooperation time division duplex system which runs in a half-duplex mode, wherein the system consists of a base station, a fixed amplification forwarding relay node and a plurality of mobile stations;

all terminals are equipped with a single antenna, and information is transmitted and interacted between a base station BS and a mobile station MS through a fixed amplifying forwarding relay node R in a half-duplex mode, wherein the information interaction consists of two stages which are respectively a multi-user selection stage and a data interaction stage, and the data interaction stage is divided into two time slots.

Respectively analyzing the changes generated in the multi-user selection stage and the data interaction stage, judging and finding the system performance by means of the average spectrum efficiency and the interruption probability of the multi-user TWR-AF system modulated by the self-adaptive discrete rate through the presentation of the cumulative probability density function and the probability density function, and reducing the influence of the system performance by utilizing an optimal power distribution technology based on channel statistical information;

in the multi-user selection stage, the relay R uses an estimator to estimate a channel between the relay R and the mobile station MS according to a pilot signal received from the mobile station MS, then the relay R selects a mobile station according to the estimated channel and a multi-user scheduling standard, the mobile station and a base station carry out information interaction, the relay R broadcasts a scheduling instruction to inform the selected mobile station to prepare for data transmission, and other unselected mobile stations keep a silent state;

in the data interaction stage, the communication between the base station and the mobile station is specified in two time slots, in the time slot 1, the base station and the mobile station respectively transmit pilot signals and data to the relay station, and the relay station R estimates channels of a BS-R link and an R-MS link according to the received signals; in the time slot 2, the received signal on the relay station is amplified by a gain G and then forwarded to the base station and the selected mobile station through an error-free feedback channel;

BS and MS_kIs dependent on the link R-MS_kChannel gain increases, which stimulates R to select the MS with the largest estimated channel gain to the largest sum capacity; MS (Mass Spectrometry)_kA time delay is required to know that it is selected to exchange messages with the BS; by using inequality, C can be maximized_p(γ₀,γ₁,γ₂) To obtain the best power allocation, i.e. the optimal problem can be expressed as:

s.t.γ₀+γ₁+γ₂＝γ_tot

wherein

Relative to gamma₀,γ₁,γ₂Is/are as follows

The second derivative of (a) is positive and thus it is a concave function, and by applying the KKT condition, we can obtain the best through some mathematical operations,

and step three, broadcasting and transmitting the processed signals.

An optimal power distribution method and system, wherein an optimal power distribution system comprises:

the first module is used for establishing a multi-user TWR-AF cooperation time division duplex system which runs in a half-duplex mode and consists of a base station, a fixed amplification forwarding relay node and a plurality of mobile stations;

a second module, which analyzes the changes generated in the multi-user selection stage and the data interaction stage, judges and discovers the system performance by the average spectrum efficiency and the interruption probability of the multi-user TWR-AF system modulated by the self-adaptive discrete rate through the presentation of the cumulative probability density function and the probability density function, and reduces the influence of the system performance by utilizing the optimal power distribution technology based on the channel statistical information;

and the third module is used for broadcasting and transmitting the processed signals.

Has the advantages that: the present invention analyzes the cumulative probability density function of the signal to interference plus noise ratio of the base station and the selected mobile station processing under the channel estimation error and the outdated channel state information, respectively, mainly by considering the multi-user TWR-AF system with adaptive modulation. Then, an exact approximation of the average spectral efficiency and outage probability is derived. The progressive performance of the adaptive system is further proposed. And finally, based on the criterion of maximizing the approximate average throughput, an optimal power distribution scheme is provided, and the influence of channel estimation errors and outdated channel state information is reduced. Numerical results show that our proposed power allocation scheme is superior to the common power allocation scheme.

Drawings

FIG. 1 is a diagram of a two-stage system model of a multiuser TWR-AF system according to the present invention.

Figure 2 is an ASE plot of a multi-user TWR-AF system under CEE and outdated CSI.

FIG. 3 is a graph of the OP variation of a multiuser TWR-AF system.

FIG. 4 is a graph of ASE of a multi-user TWR-AF system versus the number of MSs with best PA and unified PA.

Detailed Description

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the invention.

The invention relates to an optimal power distribution method, which comprises the following steps:

step one, establishing a multi-user TWR-AF cooperation time division duplex system which runs in a half-duplex mode, wherein the system consists of a base station, a fixed amplification forwarding relay node and a plurality of mobile stations.

As shown in fig. 1, all terminals are equipped with a single antenna, and perform information transmission and interaction between a base station BS and a mobile station MS in a half-duplex mode through a fixed amplify-and-forward relay node R, where the information interaction consists of two phases, which are a multi-user selection phase and a data interaction phase.

Respectively analyzing the changes generated in the multi-user selection stage and the data interaction stage, judging and finding the system performance by means of the average spectrum efficiency and the interruption probability of the multi-user TWR-AF system modulated by the self-adaptive discrete rate through the presentation of the cumulative probability density function and the probability density function, and reducing the influence of the system performance by utilizing an optimal power distribution technology based on channel statistical information;

wherein, in the multi-user selection phase, the relay R uses an estimator, and the channel between the relay R and the mobile station MS is

Estimating a channel between a relay R and a mobile station MS from a pilot signal received from the mobile station MS

The relay R then estimates the channel based on the estimated channelAnd selecting one mobile station according to the multi-user scheduling standard, performing information interaction between the mobile station and the base station, broadcasting a scheduling instruction by the relay R to inform the selected mobile station to prepare for data transmission, and keeping the other unselected mobile stations in a silent state.

In the data interaction phase, the communication between the base station and the mobile station is specified in two time slots, in the time slot 1, the base station and the mobile station respectively transmit pilot signals and data to the relay station, and the relay station R estimates channels of a BS-R link and an R-MS link according to the received signals. In time slot 2, the received signal at the relay station is amplified by gain G and then forwarded to the base station and selected mobile stations via an error-free feedback channel. Wherein

Are respectively as

Is estimated as having

Wherein

Is h₁And

relative parameter between u₁Is a variance of

A gaussian error with a mean of 0;

is h_2,kAnd

related parameter of (u)_2,kIs a variance of

Zero mean unit gauss ofAnd (4) error. x is the number of₁And x_2,kIndicating passing through BS and MS_kDuring the transmitted data, the signals received by the relay are:

wherein P is₁And P₂Is BS and MS_kThe transmit power of. n is₀～CN(0,N₀) Is additive white gaussian noise at the relay. In the second slot, the received signal at the relay station is amplified by a gain G and then broadcast. BS and MS_kThe received signals of (A) are respectively represented as

Wherein n is₁～CN(0,N₀) And n₂～CN(0,N₀) Respectively BS and MS_kAWGN of (a). Amplification factor

Wherein P is₀Is the transmitted power of the relay. E_x(. cndot.) indicates the expectation for a random variable in parentheses as x. According to the formula initially presented,

and

finally, the cancellation of the self-interference signal is performed at the base station and the selected mobile station, respectively, as follows:

when in use

Respectively relay, BS and MS_kThe average SNR of the received signal is,

and

is with links BS-R and R-MS_kIn the case of relative channel gain, the BS and the MS are obtained by the calculation of the mathematical expression_kThe post-processing SINR of (SINR) is:

and

wherein the content of the first and second substances,

from the above calculations, it can be seen that the BS and the MS_kEnd-to-end SINR of with g_2,kIncreases, this stimulates R to select the MS with the largest estimated channel gain to the largest sum capacity. MS (Mass Spectrometry)_kA time delay is required to know that it is being usedMessages are selected for exchange with the BS. Linking R-MS during data interaction phase_kHas changed, and therefore, performs the MUS based on the outdated estimated channel, this stage, link R-MS_kOf an outdated estimated channel

Estimated channel of sum link R-MSk

Has the following relationship:

where ρ is the channel dependent coefficient and v is the variance λ₂Is a 0 gauss random variable, the selected mobile station should satisfy

Wherein

Order to

g₂＝g_2,kWill be

Is set as a probability density function of

The conditional probability density function can be expressed as:

wherein I₀(x) Is a modified Bessel function of the first kind, g₂The PDF of (A) is calculated as:

can see f_g2(x) Is influenced by the number of mobile stations and p is ultimately also a factor that influences the average spectral efficiency and the probability of interruption.

The BER for coherent M-QAM modulation using gray mapping in AWGN channel can be roughly expressed as:

where M is 4 or more, set equal to the target BER,

to determine a reception SNR region using the M-QAM modulation method and the BS and MS. We denote the nth region as_n,_n+1. Since the BS and MS can select their modulation methods, respectively, the ASE of the multiuser TWR-AF system can be expressed as follows:

wherein Pr (n, gamma)_j) Is the probability of falling into the nth region, can be represented by γ_jThe CDF of (1). Gamma ray_jCDF of (A) is denoted as F_j(x) Is calculated as follows

Wherein g is₁Has the advantages of

The CDF of (a) may be further expressed as:

further comprises the following steps:

wherein

K_v(. cndot.) is a second v-order modified Bessel function.

The partition by inequality can be used to conclude that when either the end-to-end SINR of the base station or the mobile station falls to₁When the following, the nodes stop exchanging messages to reach the target BER, so we can obtain the lower bound OP of the system as follows:

further comprises the following steps:

wherein

The lower bound of the outage probability in the equation is close to the exact value over the entire SNR range. When rho₁＝ρ₂＝ρ₀，γ₁＝αγ₀，γ₂＝βγ₀In order to provide more insight, how CEE and outdated CSI will affect the performance of a multi-user TWR-AF system, the expression is extended to obtain ASE C at high signal-to-noise ratio_asyAnd OP P_asyIs represented as follows:

when no CEE is present, i.e.Say rho ₀1, one can obtain:

when CEE is present, we can obtain

In the presence of CEE and outdated CSI, the diversity order is zero, because the system is limited by interference and self-interference cannot be completely eliminated in the presence of CEE, which means that an erroneous basis occurs at high SNR when CSI is imperfect. The same holds for asymptotic values, where in the absence of CEE the ASE decreases with decreasing ρ, and where in the presence of CEE the ASE is arbitrarily chosen for ρ.

By using inequality, C can be maximized_p(γ₀,γ₁,γ₂) To obtain the best power allocation, i.e. the optimal problem can be expressed as:

s.t.γ₀+γ₁+γ₂＝γ_tot

relative to gamma₀,γ₁,γ₂Is/are as follows

The second derivative of (a) is positive and thus it is a concave function, and by applying the KKT condition, we can obtain the best through some mathematical operations,

step three, broadcasting and transmitting the processed signals

Monte Carlo (MC) simulation was used to illustrate CEE and outdated CSI versus multiuser TWR-AF systems with ADR modulationAnd the influence of ASE and OP, and the realizability of the invention is verified. Furthermore, we consider the maximum constellation size M_NIs 2¹⁶Object of

And ρ₁＝ρ₂＝ρ₀。

ASE of multiuser TWR-AF systems under CEE and expired CSI with average SNR set at γ as shown in FIG. 2₀. It can be seen that our analysis results are very consistent with the MC simulation results and that ASE is greatly reduced compared to the case without CEE and that the lower capacity limit occurs when CEE is present. This is because the system is interference limited and γ₁，γ₂The SNR region in which the maximum constellation modulation size is selected cannot be obtained. We can also see that outdated CSI exacerbates ASE performance degradation. However, CEE has a greater impact on degrading system performance.

Figure 3 illustrates the outage probability of a multiuser TWR-AF system. The result shows that the lower analysis bound of the interruption probability is basically consistent with the MC simulation result in the whole signal-to-noise ratio range. We can also see that the diversity order remains unity for any number of MS and p values when CEE is not present, while the diversity order of the system drops to zero when CEE is present, which corroborates our earlier analysis.

Fig. 4 shows the average spectral efficiency versus the number of mobile stations K for a multi-user TWR-AF system with optimal power allocation and average power allocation. When the circles represent the MC simulation results, the lines are analytic ASE. It can be seen that they have a good match and are found at ρ and ρ₀At different values, we propose an optimal PA scheme that is superior to the unified PA scheme. In the absence of CEE, the performance gap decreases as K or ρ increases. This can be explained by the channel link R-MS when K or p increases_kBecome better and perform to link R-MS_kIs more sensitive.

Based on the method, an optimal power distribution system can be constructed, and the method comprises the following steps:

the first module is used for establishing a multi-user TWR-AF cooperation time division duplex system which runs in a half-duplex mode and consists of a base station, a fixed amplification forwarding relay node and a plurality of mobile stations;

a second module, which analyzes the changes generated in the multi-user selection stage and the data interaction stage, judges and discovers the system performance by the average spectrum efficiency and the interruption probability of the multi-user TWR-AF system modulated by the self-adaptive discrete rate through the presentation of the cumulative probability density function and the probability density function, and reduces the influence of the system performance by utilizing the optimal power distribution technology based on the channel statistical information;

and the third module is used for broadcasting and transmitting the processed signals.

The present invention analyzes the cumulative probability density function of the signal to interference plus noise ratio of the base station and the selected mobile station processing under the channel estimation error and the outdated channel state information, respectively, mainly by considering the multi-user TWR-AF system with adaptive modulation. Then, an exact approximation of the average spectral efficiency and outage probability is derived. The progressive performance of the adaptive system is further proposed. And finally, based on the criterion of maximizing the approximate average throughput, an optimal power distribution scheme is provided, and the influence of channel estimation errors and outdated channel state information is reduced. Numerical results show that our proposed power allocation scheme is superior to the common power allocation scheme.

As noted above, while the present invention has been shown and described with reference to certain preferred embodiments, it is not to be construed as limited thereto. Various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (4)

1. An optimal power allocation method, comprising:

step one, establishing a multi-user TWR-AF cooperation time division duplex system which runs in a half-duplex mode, wherein the system consists of a base station, a fixed amplification forwarding relay node and a plurality of mobile stations;

respectively analyzing the changes generated in the multi-user selection stage and the data interaction stage, judging and finding the system performance by means of the average spectrum efficiency and the interruption probability of the multi-user TWR-AF system modulated by the self-adaptive discrete rate through the presentation of the cumulative probability density function and the probability density function, and reducing the influence of the system performance by utilizing an optimal power distribution technology based on channel statistical information;

and step three, broadcasting and transmitting the processed signals.

2. The method of claim 1, wherein the step one further comprises:

all terminals are equipped with a single antenna, and information is transmitted and interacted between a base station BS and a mobile station MS through a fixed amplifying forwarding relay node R in a half-duplex mode, wherein the information interaction consists of two stages which are respectively a multi-user selection stage and a data interaction stage, and the data interaction stage is divided into two time slots.

3. The method of claim 1, wherein the step one further comprises:

in the multi-user selection stage, the relay R uses an estimator to estimate a channel between the relay R and the mobile station MS according to a pilot signal received from the mobile station MS, then the relay R selects a mobile station according to the estimated channel and a multi-user scheduling standard, the mobile station and a base station carry out information interaction, the relay R broadcasts a scheduling instruction to inform the selected mobile station to prepare for data transmission, and other unselected mobile stations keep a silent state;

in the data interaction stage, the communication between the base station and the mobile station is specified in two time slots, in the time slot 1, the base station and the mobile station respectively transmit pilot signals and data to the relay station, and the relay station R estimates channels of a BS-R link and an R-MS link according to the received signals; in the time slot 2, the received signal on the relay station is amplified by a gain G and then forwarded to the base station and the selected mobile station through an error-free feedback channel;

BS and MS_kTo be terminated toEnd SINR all along with link R-MS_kChannel gain increases, which stimulates R to select the MS with the largest estimated channel gain to the largest sum capacity; MS (Mass Spectrometry)_kA time delay is required to know that it is selected to exchange messages with the BS;

by using inequality, C can be maximized_p(γ₀，γ₁，γ₂) To obtain the best power allocation, i.e. the optimal problem can be expressed as:

s.t.γ₀+γ₁+γ₂＝γ_tot

wherein

Relative to gamma₀，γ₁，γ₂Is/are as follows

The second derivative of (a) is positive and thus it is a concave function, and by applying the KKT condition, we can obtain the best through some mathematical operations,

4. an optimal power distribution system, comprising:

the first module is used for establishing a multi-user TWR-AF cooperation time division duplex system which runs in a half-duplex mode and consists of a base station, a fixed amplification forwarding relay node and a plurality of mobile stations;

a second module, which analyzes the changes generated in the multi-user selection stage and the data interaction stage, judges and discovers the system performance by the average spectrum efficiency and the interruption probability of the multi-user TWR-AF system modulated by the self-adaptive discrete rate through the presentation of the cumulative probability density function and the probability density function, and reduces the influence of the system performance by utilizing the optimal power distribution technology based on the channel statistical information;

and the third module is used for broadcasting and transmitting the processed signals.

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