CN105960008B

CN105960008B - Method for inhibiting interference of Femtocell on surrounding cells

Info

Publication number: CN105960008B
Application number: CN201610503952.4A
Authority: CN
Inventors: 陈文婕; 肖竹
Original assignee: Central South University of Forestry and Technology
Current assignee: Central South University of Forestry and Technology
Priority date: 2016-06-30
Filing date: 2016-06-30
Publication date: 2020-02-14
Anticipated expiration: 2036-06-30
Also published as: CN105960008A

Abstract

The invention discloses a method for inhibiting interference of Femtocell on surrounding cells, which comprises the following steps: 1) a new criterion is proposed: the larger the sum of the interference generated to the surrounding cells, the more severely the FemtoBS will be constrained in its transmit power. 2) Based on this criterion, a cost function proportional to the interference leakage is designed. 3) On the basis, a non-cooperative game power control model is provided based on a non-cooperative game theory, and an adaptive power control algorithm according to the game model is provided. When the Femtocell layout density is increased, the link capacity of a macrocell user is not reduced, and the capacity is 1.5-2.2 times that of the Femtocell adopting a constant power control algorithm, so that the interference of the Femtocell on the surrounding macrocell can be well inhibited by the algorithm. And the transmitting power of all Femtocell base stations can quickly reach a stable value, and the algorithm convergence speed is high.

Description

Method for inhibiting interference of Femtocell on surrounding cells

Technical Field

The invention mainly relates to a power control and interference suppression technology in the field of wireless communication, in particular to a method for suppressing interference of a Femtocell on surrounding cells by a Femtocell downlink power control algorithm based on a non-cooperative game, which covers cross-layer interference of a Femtocell network on a traditional macrocell network, co-channel interference suppression between femtocells and fairness for users.

Background

In the beginning of the twenty-first century, wireless communication technology has been continuously and rapidly developed, and data services and multimedia services supported by the wireless communication technology are increasing day by day. In the near future, over two-thirds of these rapidly increasing services will be voice services and 90% of data services will occur in indoor environments. Current cell structures (including macro cells and micro cells) can basically satisfy the seamless coverage of outdoor environments, but the signal coverage of indoor environments is poor. To address this problem, Femtocell (Femtocell) technology is on the rise and is becoming a solution to expanding the indoor coverage of mobile communications with much current interest. The Femtocell can connect to any existing IP network with its Home access point plug and play and is therefore also referred to as a Home-based Station.

One of the important problems with Femtocell is interference with surrounding cells. The invention aims at the problem of interference between Femtocell and Macrocell. Generally a Femtocell must satisfy: firstly, the interference on the conventional Macrocell cannot be caused, and then the interference caused by the Macrocell and the adjacent Femtocell must be overcome.

Over the years, researchers propose various solutions to the interference, such as describing various interference scenes of an uplink/downlink in a Macrocell-Femtocell two-layer network, and providing a method for quantifying and eliminating the interference degree for part of the scenes; researchers have also solved the cross-layer interference management problem from two ways, centralized and distributed processing of power control, respectively. The centralized processing mode solution needs centralized processing of global information and is difficult to realize in practice, while the distributed processing mode solution only needs local information but can only ensure the service quality of macro cell users; the scheme of self-correction of Femtocell transmitting power and automatic selection of carrier frequency is provided, the service quality of macro cell users can be effectively guaranteed, but the frequency spectrum utilization efficiency is low; regarding the Femtocell system as a Multi-agent (Multi-agent), i.e. the Femtocell is used as an agent responsible for Radio Resource allocation; the user selection and the distributed power distribution are carried out by utilizing a queuing theory to inhibit the cross-layer interference of the Femtocell on the Macrocell, and the sum of the transmitting power is minimized under the condition of meeting the requirement of the user data rate.

In recent years, the game theory is widely applied to power control and interference suppression research in the field of wireless communication. Some researchers are focused on analyzing the cross-layer interference of the Femtocell uplink, and introduce the Nash Equilibrium theory by defining the SINR (signal to interference plus noise ratio) of the edge user, so as to try to reduce the SINR of the Femtocell uplink which brings the maximum interference and ensure the link quality. The method also utilizes a game theory to carry out Femtocell downlink power control, pays attention to fairness among Femtocell users, and has the defects that the method cannot realize minimum interference sum to surrounding cells, and the Nash equilibrium solution of the method is obtained by searching, so that the convergence speed is low. Each FemtoBS wishes to enhance its link capacity by increasing its transmit power and of course interferes with surrounding cells to affect their link capacity, so that they compete with each other and couple to each other.

Disclosure of Invention

In order to solve the technical problem, the invention provides a method for inhibiting interference of Femtocell on surrounding cells by using a Femtocell downlink Power Control algorithm based on Non-cooperative Power Control (NPCG).

In order to effectively reduce the interference of the FemtoBS to the surrounding cells, the invention provides a new criterion: the larger the interference sum generated to the surrounding cells, the more severely the FemtoBS will be constrained in its transmit power. On the basis of the criterion, a cost function proportional to Interference Leakage (IL) is designed, and an adaptive Power Control algorithm based on NPCG (Non-coherent Power Control Gate) is further provided to inhibit cross-layer Interference of a Femtocell network to a traditional macrocell network and co-channel Interference between femtocells, and meanwhile, user fairness is considered.

In the game model of the invention, each femtocell can adaptively adjust the transmission power level thereof according to the interference degree of the femtocell on the surrounding cells and the received interference sum, and can rapidly reach stable transmission power, namely Nash equilibrium solution. Once the nash equilibrium solution is obtained, any user cannot change its own transmission power in a single way without affecting other users, i.e. the system algorithm reaches convergence. The invention also theoretically deduces and demonstrates the existence and uniqueness of the model Nash equilibrium solution.

Generally a Femtocell must satisfy: firstly, the interference on the conventional Macrocell cannot be caused, and then the interference caused by the Macrocell and the adjacent Femtocell must be overcome.

One of the important problems with Femtocell is interference with surrounding cells. The invention aims to solve the problem of interference between the Femtocell and the Macrocell.

In order to solve the technical problems, the technical scheme provided by the invention is as follows: a method for suppressing interference of Femtocell to surrounding cells by Femtocell (Femtocell) based on a Femtocell downlink power control algorithm of non-cooperative gaming power control (NPCG) comprises the following steps:

s1: under the criterion that the transmission power is more severely restricted based on the femtocell base station (femtocell bs) generating the larger sum of Interference to the surrounding cells, a cost function proportional to the Interference Leakage (IL) is designed. On the basis, a Non-cooperative Power Control (NPCG) model is provided based on a Non-cooperative Game theory;

s2: selecting link capacity as a payment function, and defining a net utility function of the FemtoBS as a difference value of the payment function and a cost function of the FemtoBS;

s3: and solving the FemtoBS transmission power based on the self-adaptive power level of the non-cooperative game power control model.

As a further improvement of the method, the non-cooperative game power control model adopts same-frequency networking in a Macrocell-Femtocell two-layer network.

Further, the non-cooperative game power control model in step S1 is:

wherein the content of the first and second substances,

represents a participant in the game, namely FemtoBS;

is the policy space of the ith FemtoBS; p in this_maxMaximum transmit power for each FemtoBS; and set of policy spacesIs a cartesian product space formed by each FemtoBS policy space; u shape_d(P_f,i) The penalized net utility function for the ith FemtoBS.

Further, in step S2, the link capacity formula based on the signal to interference plus noise ratio may obtain a payment function of the ith Femtocell base station:

U(P_f,i)＝log₂(1+SINR_i) (1)

wherein, the SINR_iIs the ithThe signal to interference plus noise ratio received by the Femtocell user.

Further, macrocell user 0 has a signal to interference and noise ratio of

In the formula P_m,0Refers to the transmit power of the central macrocell base station; h is_m,00Is the path gain from the central macrocell base station to its served target macrocell users; p_m,i(i ═ 1,2, L,6) refers to the transmit power of the ith interfering macrocell base station; h is_m,0i(i ═ 1,2, L,6) denotes the path gain from the i-th interfering macrocell base station to the target macrocell user 0; and P is_f,jRepresents the transmission power of the jth FemtoBS; h is_mf,ojMeans the path gain from the jth FemtoBS to the target macrocell user 0; n represents the background noise power;

and the signal-to-interference-and-noise ratio received by the ith Femtocell user is

In the formula P_f,iRepresents the transmission power of the ith FemtoBS; h is_ff,ijMeans the path gain from the jth Femtocell BS to the ith Femtocell user; p_m,kRepresents the transmission power of the kth macrocell base station; and h_fm,ikRepresenting the path gain from the kth macrocell base station to the ith Femtocell user; n is the noise power.

Further, the cost function in step S1 is proportional to the interference leakage; wherein, the interference leakage is the sum of interference generated by the ith Femtocell base station to the surrounding users, and the specific expression is

Wherein P is_f,iRefers to the transmission power, h, of the ith FemtoBS_ff,jiRepresents the path gain from the ith Femtocell BS to the jth Femtocell user, and h_mf,0iRepresenting the path gain from the ith femtocell to the reference macrocell user;

and the cost function is proposed to be proportional to the IL, but considering that cross-layer interference is to be reduced as much as possible, the Femtocell base station which generates interference to the macrocell user should be more severely constrained. In order to reflect that the punishment degrees of interference generated by different users are different, the interference leakage IL is adjusted, two punishment factors are introduced, and then the cost function of the ith Femtocell base station is

Lambda in the formula_i1，λ_i2Are penalty factors which are measures of the effectiveness of the cost function by adjusting lambda_i1，λ_i2The relative size of the Femtocell base station determines which layer of network interference the Femtocell base station is more sensitive to, and the absolute size is determined by the Femtocell base station according to the interference environment around the Femtocell base station.

Further, the net utility function of the FemtoBS in step S2 is a difference between the payment function and the cost function of the FemtoBS, and the net utility function of the ith FemtoBS can be given by using a specific expression of the net utility function of the FemtoBS

Wherein

The mathematical model of the non-cooperative game can be found as Objective by combining the above net utility function and the policy space: max { U }_d(P_f，i)＝U(P_f，i)-C(P_f，i)，i＝1，2，…，N}

s.t.0≤P_f，i≤P_max； (7)

Further, the step S3 includes:

s31: initializing the transmit power P of a FemtoBS_f，i，i＝[1，2，L，N]. Where N is in the Femtocell blockThe number of femtocells in the active state;

s32: the femto BS calculates the channel gain h from the femto BS to the macro cell user_mf，oiAnd channel gain h to other adjacent Femtocell users_ff，ji，j∈[1，N]，j≠i，i；

S33: the femto BS calculates the interference sum A from the surrounding cells;

s34: the relative penalty factor C and the comprehensive factor D of the FemtoBS are adaptively adjusted by the FemtoBS according to the surrounding interference environment;

s35: and (3) adaptively adjusting the transmission power in combination with the strategy space of the FemtoBS until the FemtoBS stops wireless connection.

The NPCG-based adaptive power level solves the FemtoBS transmit power.

First, the formula (6) is determined with respect to P_f，iIs derived from the first order

Wherein the content of the first and second substances,

the interference sum received by the ith Femtocell user comprises cross-layer interference of a macro cell base station to the ith Femtocell user, co-channel interference of an adjacent Femtocell base station to the ith Femtocell user and interference of background noise to the ith Femtocell user.

Order to

Can be solved about U_d(P_f,i) The stagnation point of (2):

in the formula

To facilitate the later simulation parameter settings, we rewrite this equation as:

B＝λ_i·(∑_i≠i·h_ff，ji+C·h_fm，0i) (10)

wherein λ_i＝λ_i1As an absolute penalty factor, C ═ λ_i2/λ_i1The relative penalty factor C is adjusted, so that the degree of protecting the macrocell users from interference can be effectively adjusted, and the larger the C is, the more serious the femtocell user is punished when the femtocell generates interference on the macrocell users; the smaller C, the smaller penalty the femto BS receives when generating interference to macro cell users. The adjusted stagnation point is then

In the formula

This is referred to herein as the integral factor for the ith FemtoBS. The Femtocell bs needs some local information to adaptively adjust its own transmit power level, and as can be seen from equation (11), it needs to know the sum a of the interference signal powers received by the Femtocell users. Since the Femtocell radius is relatively small, considering it approximately as a point, then there is a point where the sum of the interference received by the Femtocell user can be approximately equal to the sum of the interference received by the Femtocell user, so a can be determined by the sum of the interference received by the Femtocell user, and no user feedback is needed. While the path gain to other users for FemtoBS can be obtained as follows: the femto BS calculates the channel gain of a reverse link by receiving special training sequence signals of macro cell users around the femto BS, the distance between the macro cell users and the femto BS can be calculated according to the channel gain, and then the channel gain h of a forward link is calculated according to the distance_mf,0iOr by user feedback; the forward link gain and the reverse link gain between the Femtocell and the Femtocell are symmetrical, so that the channel gain h of the forward link can be calculated by receiving the pilot signal intensity of the surrounding Femtocell users_ff,ji,j∈[1,N],j≠i。

Combining the formula (11) with the strategy space of the Femtocell BS to obtain the transmission power of the ith Femtocell base station as

In the formulaThe sum of the interference received by the ith Femtocell is the sum of the interference received by the ith Femtocell, and the Femtocell radius is small relative to the radius of the macrocell, so that the interference received by the Femtocell base station is equal to the interference received by the Femtocell user by assuming that the Femtocell is a point.

Further, the basic criteria according to which the FemtoBS transmission power is solved in step S3 are: the method has the advantages that the interference of the Femtocell on the surrounding cells is minimized, the self transmitting power is improved to the greatest extent to optimize the self link capacity, and further, the net utility function of the system is optimized.

Further, the non-cooperative game power control model has a Nash equilibrium solution and can be guaranteed to be unique.

The nash equilibrium solution of the game model is a rational outcome after each competing individual game. In this rational conclusion, none of the competing individuals can obtain the benefit improvement by unilaterally changing their own policy space, i.e. if the power vector P_f ^*＝(P_f1 ^*,P_f2 ^*,L,P_fN ^*) Non-cooperative gamingFor Nash equilibrium of

Is always true, wherein

P_f,-iRepresenting transmit power vectors of FemtoBS other than the ith FemtoBS.

The existence and uniqueness of the nash equilibrium solution of this algorithm will be demonstrated in the form of theorem below.

Nash equilibrium solution exists the theorem: the power control game model has the following essential conditions of Nash equilibrium solution: (1) strategy space of ith FemtoBS

Is a non-empty, convex closed subset of the Euclidean space; (2) the net utility function of FemtoBS satisfies continuity in the above feasible domain and is a pseudo-convex (concave) function.

And (3) proving that: as can be seen from the foregoing, the strategy space of the ith FemtoBS is

Obviously satisfies the condition (1) of the nash equilibrium solution existence theorem; in addition, the net utility function U of the ith FemtoBS is known from equation (6)_d(P_f,i) For its policy space

Upper continuous function, so only U need be proved below_d(P_f,i) The degree of convexity of (1).

To pair

In respect of P_f,iWhen the first order partial derivative is obtained, there are

As is apparent from the formula (12),

always on, then U is known_d(P_f,i) Is its policy space

A convex function of (a). Since the convex function is certainly also a pseudo-convex function, U_d(P_f,i) And also its policy space

Above. Then is full ofSufficient condition (2) that the presence of nash equilibrium solution is warranted.

The uniqueness theorem proves that:

for formula (7) to determine P_f,iFirst order partial derivatives of (j ≠ i)

The fact that the formula (14) is less than zero constantly proves that the game model is an S-model, and the special property of the S-model is combined, namely that a unique Nash equilibrium solution exists, so that the non-cooperative game model provided by the invention has the Nash equilibrium solution and can ensure the uniqueness.

Compared with the prior art, the invention has the advantages that:

the invention relates to a method for inhibiting interference of Femtocell on surrounding cells based on a Femtocell downlink Power Control algorithm of Non-cooperative Game Power Control (NPCG). In the NPCG model, each FemtoBS is designed with a reasonable utility function and cost function to obtain a certain link capacity while constraining its transmit power, and the model relies on the new criteria set forth herein: the larger the sum of the interference generated to the surrounding cells, the more severely the FemtoBS will be constrained in its transmit power. The cost function proportional to interference leakage eliminates the leisurely of the FemtoBS, and the design of the utility function ensures the existence and uniqueness of the Nash equilibrium solution, and simultaneously enables the NPCG model to quickly converge to the Nash equilibrium solution. When the Femtocell layout density is increased, the link capacity of a macrocell user is not reduced, and the capacity is 1.5-2.2 times that of a Femtocell adopting a constant power control algorithm, so that the interference of the Femtocell on surrounding macrocells can be well inhibited by the algorithm. And the transmitting power of all Femtocell base stations can quickly reach a stable value, and the algorithm convergence speed is high.

Drawings

FIG. 1 is a schematic overall flow diagram of the present invention;

FIG. 2 is a schematic diagram of a process for solving the transmission power of the femtobS according to the present invention;

FIG. 3 is a schematic diagram of a Macrocell-Femtocell two-layer network model;

fig. 4 is a schematic diagram of the transmission power of the FemtoBS in the simulation scenario of type 1;

fig. 5 is a schematic diagram of the transmit power of the FemtoBS in the simulation scenario of fig. 5;

fig. 6 is a schematic diagram of the transmission power of the FemtoBS in the 8 th simulation scenario;

FIG. 7 is a schematic diagram of system capacity under different simulation scenarios;

fig. 8 is a schematic diagram showing the comparison of the user capacity of the macro cell under different power control algorithms in different simulation scenarios;

fig. 9 is a schematic diagram illustrating a comparison of user capacities of macro cells under different distances and different power control algorithms.

Detailed Description

The invention is further described below with reference to the drawings and specific preferred embodiments of the description, without thereby limiting the scope of protection of the invention.

Fig. 3 shows a Macrocell-Femtocell two-layer network model, which is a Macrocell network formed by 7 regular hexagonal macrocells and a Femtocell block embedded therein. For the sake of analysis, it is assumed that a certain number of femtocells are deployed only in the central macro cell, and that the femtocells are present in the form of clusters, i.e. Femtocell blocks (Femtocell blocks), and that only one user in communication state is present in each Femtocell cell in communication state at a certain time.

The invention performs static simulation aiming at the scene mode at a specific moment. The simulated cell structure model is shown in fig. 3, where the Femtocell Block (Femtocell Block) contains a maximum of 40 Femtocells, and the reference macrocell user is located near Femtocell 3. In order to analyze the problem more clearly, 5 Femtocell are randomly selected, and the serial numbers of the 5 Femtocell are recorded, and the serial numbers are as follows: 3. 19, 25, 30, 39 as a first simulation scenario. On the basis of the first simulation scene, 5, 10, 15, 20, 25, 30 and 35 different femtocells are respectively and randomly added to

form

2, 3, 4, 5, 6, 7 and 8 simulation scenes.

The radius of 7 macro cells in the cell structure model is 500m, and the Femtocell blocks formed by arranging 40 femtocells are formed by sub-Femtocell blocks which are distributed at two sides of a city street and respectively comprise 20 femtocells, and each sub-Femtocell block is provided with a corridor with the width of 1.5 m. In addition, a pedestrian passageway with the width of 1.5m is respectively arranged at the two sides of the street with the width of 7 m. The specific reference numbers for each Femtocell are shown in figure 3. Each Femtocell area shape here is assumed to be a square with a side length of 10 m. The base station is arranged at the center of the cell, and the user antenna and the cell base station antenna both adopt omnidirectional antennas.

Setting system simulation parameters: maximum transmit power P of each FemtoBS_max100mW, and 5 × 10 background noise power n^-13W is added. Suppose that each FemtoBS has the same combination factor D of 0.15 × 10^-11Relative penalty factor C ═ λ_i2/λ_i1Is determined by the number of femtocells around the reference macrocell user. The normalized link capacity is formulated asα dB are operands, and the value size is 3 dB.

Fig. 4, 5 and 6 show the transmission power of

FemtoBS

3, 19, 25, 30 and 39 in the first, fifth and eighth simulation scenarios, respectively. It can be seen that, as the Femtocell layout density increases, the transmit power of the Femtocell bs decreases, mainly because as the Femtocell density increases, the sum of the co-channel interference of each Femtocell to the surrounding cells becomes larger, and in order to decrease the sum of the interference, the Femtocell self-adaptively decreases its transmit power. Figures 4, 5 and 6 also show that the transmit power of the Femtocell bs 3 is the lowest, because as shown in figure 3, there is one macrocell user in the vicinity of the Femtocell 3 and that is closest to the Femtocell 3 and therefore more susceptible to interference from the Femtocell bs 3. In order to ensure that the service quality of macro cell users in a macro cell-Femtocell two-layer network is influenced as little as possible, the transmission power of the femto BS which generates interference on the macro cell users should be reduced by a certain penalty, and the larger the interference generated on the macro cell users is, the larger the penalty should be, the larger the penalty is, so that the penalty of the femto BS 3 is the largest, and the transmission power of the femto cell users is the smallest. In addition, the transmitting power of each femto BS reaches a stable value quickly, and the existence and the quick convergence of the algorithm Nash equilibrium solution are verified again.

Fig. 7 shows the link capacity of the reference macrocell user, the sum of all Femtocell link capacities, and the overall system capacity under different simulation scenarios. The figure shows that as the number of femtocells increases, the capacity of the whole system almost rises linearly and is far larger than that of the existing macro cell network system. In addition, the link capacity of the reference macro cell user is hardly influenced by the cross-layer interference of the Femtocell network layer under the action of the power control algorithm provided by the invention, and the user capacity is approximately kept at 1.55bits/s/Hz all the time. Therefore, on the premise of adopting an advanced cross-layer interference management technology, the harmonious fusion of the traditional macro cell network and the newly-intervened Femtocell network is possible, and the introduction of the Femtocell network can improve the system capacity of the whole system and hardly influence the user capacity of the original macro cell.

Fig. 8 shows the link capacity of the reference macrocell user as a function of the number of femtocells under different power control algorithm conditions. It can be seen from the figure that after the Femtocell network adopts the power control scheme proposed by the present invention, the link capacity of the macrocell users does not decrease with the increase of the Femtocell layout density, but when the equal power transmission scheme is adopted, and it is assumed that P is_sj＝0dB,j∈[1,N]The link capacity of macro cell users tends to decrease with the increase of Femtocell layout density, and the capacity of the macro cell users is 1.5-2.2 times that of the Femtocell users. In conclusion, it can be obtained that: the power control algorithm can well inhibit cross-layer interference of the Femtocell network to the traditional macrocell network, and effectively protects the service quality of macrocell users from being influenced by the Femtocell network.

Fig. 9 shows the maximum Femtocell layout density, i.e. the link capacity of the reference macrocell user under different power control algorithms varies with the distance from the reference macrocell base station when 40 femtocells are included in the Femtocell block. It is shown that as the reference macrocell user moves from the left-most to the right-most side of the street as shown in fig. 1, the link capacity of the reference macrocell user in both algorithms decreases, because the reference macrocell user is farther from the central macrocell base station, the power of the received signal from the central macrocell base station also decreases, and the variation of the received interference from the Femtocell network and the neighboring macrocells is small, which results in a decrease in the sir of the received signal, and thus a decrease in the user capacity of the macrocell. Although the user capacity of the macro cell under the two power control schemes is reduced, the link capacity of the macro cell based on the non-cooperative game power control algorithm is always about twice that of the link capacity of the macro cell during constant power transmission, and the effectiveness of the algorithm in suppressing cross-layer interference is demonstrated again.

Simulation results show that the algorithm reasonably allocates the transmitting power of the FemtoBS, the service quality of macro cell users is effectively guaranteed, and the transmitting power of each FemtoBS can be stabilized quickly. The effectiveness and fast convergence of the interference suppression algorithm is fully verified.

The foregoing is considered as illustrative of the preferred embodiments of the invention and is not to be construed as limiting the invention in any way. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make numerous possible variations and modifications to the present invention, or modify equivalent embodiments to equivalent variations, without departing from the scope of the invention, using the teachings disclosed above. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention should fall within the protection scope of the technical scheme of the present invention, unless the technical spirit of the present invention departs from the content of the technical scheme of the present invention.

Claims

1. A method for suppressing interference to surrounding cells from a Femtocell, comprising the steps of:

s1: under the criterion that the transmission power of the FemtoBS is more severely restricted based on the fact that the sum of the interference generated to the surrounding cells is larger, a cost function proportional to the interference leakage is set, and a non-cooperative game power control model is established, wherein the non-cooperative game power control model is as follows:

wherein the content of the first and second substances,representing the participants of the game, i.e. the Femtocell bs, N is the number of active femtocells in the Femtocell block;

is the ith FemtoBS policy space; p in this_maxMaximum transmit power for each FemtoBS; and set of policy spaces

Is a cartesian product space formed by each FemtoBS policy space; u shape_d(P_f，i) The net utility function of the ith FemtoBS subjected to punishment is obtained;

s2: selecting link capacity as a payment function, and obtaining the payment function of the ith Femtocell base station based on a link capacity formula of a signal-to-interference-and-noise ratio

U(P_f，i)＝log₂(1+SINR_i)

Wherein, the SINR_iThe signal to interference plus noise ratio received by the ith Femtocell user;

and defining the net utility function of the FemtoBS as the difference value of the payment function and the cost function of the FemtoBS, and giving the net utility function of the ith FemtoBS, wherein the specific expression of the net utility function is

Wherein1,2, …, N, the mathematical model of the non-cooperative game can be found by combining the above net utility function and policy space as

Objective：max{U_d(P_f，i)＝U(P_f，i)-C(P_f，i)，i＝1，2，…，N}

s.t.0≤P_f，i≤P_max；

Wherein the cost function

In the formula, P_f，iRefers to the transmission power of the ith Femtocell BS, N is the number of active femtocells in the Femtocell block, h_ff，jiRepresents the path gain from the ith Femtocell BS to the jth Femtocell user, and h_mf，0iDenotes the path gain, λ, of the ith FemtoBS to the reference macrocell user_i1，λ_i2Are all penalty factors;

2. The method for suppressing the interference of the Femtocell on the surrounding cells according to claim 1, wherein the non-cooperative game power control model adopts co-frequency networking in a Macrocell-Femtocell two-layer network.

3. The method as claimed in claim 1, wherein the signal to interference and noise ratio of macro cell user 0 is

In the formula P_m，0Refers to the transmit power of the central macrocell base station; h is_m，00Is the path gain from the central macrocell base station to its served target macrocell users; p_m，i(i-1, 2, …,6) isThe transmission power of the ith interference macro cell base station; h is_m，0i(i ═ 1,2, …,6) represents the path gain from the i-th interfering macrocell base station to the target macrocell user 0; and P is_f，jRepresents the transmission power of the jth FemtoBS; h is_mf，ojMeans the path gain from the jth FemtoBS to the target macrocell user 0; n represents the background noise power;

Table P in the formula_f，iIndicating the transmission power of the ith FemtoBS; h is_ff，ijMeans the path gain from the jth Femtocell BS to the ith Femtocell user; h is_ff，iiMeans the path gain from the ith Femtocell BS to the ith Femtocell user; p_m，kRepresents the transmission power of the kth macrocell base station; and h_fm，ikRepresenting the path gain from the kth macrocell base station to the ith Femtocell user; n is the noise power.

4. The method of claim 1, wherein the step S3 includes:

s31: initializing the transmit power P of a FemtoBS_f，i，i＝[1，2，…，N]；

S32: the femto BS calculates the channel gain h from the femto BS to the macro cell user_mf，oiAnd channel gain h to other adjacent Femtocell users_ff，ji，j∈[1，N]，j≠i；

S33: FemtoBS calculates the interference sum a from the surrounding cells, where,

it is the sum of the interference received by the ith Femtocell user;

s34: the FemtoBS adjusts the relative penalty factor C and the comprehensive factor D of the FemtoBS according to the interference environment around the FemtoBS, wherein C is lambda_i2/λ_i1Let us order

Can be solved about U_d(P_f，i) The stagnation point of (1);

in the formula

It is referred to herein as the integral factor of the ith FemtoBS, where λ_i＝λ_i1Is an absolute penalty factor; h is_ff，jiRepresenting the path gain from the ith Femtocell BS to the jth Femtocell user; h is_ff，iiMeans the path gain from the ith Femtocell BS to the ith Femtocell user;

5. The method of claim 1, wherein the basic criteria for solving the Femtocell transmit power in step S3 is that: the method has the advantages that the interference of the Femtocell on the surrounding cells is minimized, the self transmitting power is improved to the greatest extent to optimize the self link capacity, and further, the net utility function of the system is optimized.

6. The method for suppressing Femtocell interference on surrounding cells as recited in claim 1, wherein the non-cooperative game power control model has nash equilibrium solution and can be guaranteed to be unique.