CN107249213A - A kind of maximized power distribution method of D2D communication Intermediate Frequencies spectrum efficiency - Google Patents

Abstract

The invention discloses a power distribution method for maximizing spectrum efficiency in D2D communication. Through distributed optimization of the transmission power of cellular users and the transmission power of D2D user pairs, the minimum service quality requirements of macro users and the relationship between D2D users and cellular users are ensured. Maximize the spectral efficiency of D2D users under power constraints. In the case of given cellular frequency band resources, maximizing the spectral efficiency of D2D communication is equivalent to maximizing the sum rate of D2D communication. This method gives the optimal cellular user transmission power and D2D link transmission power under the condition that any D2D user can use all channels and any channel can be occupied by all D2D users at the same time. The non-convex problem is approximated as a solvable convex optimization problem by the convex approximation method, and the closed-form solution is used to quickly converge to the optimal solution of the convex problem. The invention has the advantages of fast convergence speed, small calculation amount, easy realization and high result precision.

Description

A Power Allocation Method to Maximize Spectrum Efficiency in D2D Communication

technical field

The present invention relates to a D2D communication technology, specifically a distributed optimization of the transmission power of cellular users and the transmission power of D2D users, in the case of ensuring the minimum service quality requirements of cellular users and the power limitation of D2D users and cellular users A fast optimization algorithm for maximizing spectrum efficiency of D2D users belongs to the technical field of mobile communication networks.

Background technique

D2D communication refers to a technology that directly uses cellular network resources to realize communication between adjacent users without passing through a base station. D2D technology is expected to reduce base station load, improve coverage, reduce energy efficiency, and improve cellular spectrum utilization. A large number of studies have shown that D2D communication based on cellular network can provide more stable and higher-speed wireless services in a local area. D2D technology has broad application prospects. For example, at a large-scale gathering, the organizer distributed a resource address to all participants to allow people to fund and obtain electronic resources. If all people send requests to the site through the cellular network at the same time, even if the server of the website can withstand such high concurrent visits, the cellular network carrying all these will cause network congestion due to limited spectrum resources. At this time, if the D2D sharing technology is introduced, the device that has downloaded the resource will share it with other nearby user devices through the D2D network, which will greatly reduce the network congestion time and improve the user experience.

Since D2D users and cellular users share spectrum resources, D2D users will inevitably interfere with cellular users while utilizing cellular network resources, and vice versa. Therefore, the key to realizing the advantages of D2D technology lies in the effective management of interference, which mainly includes the allocation of D2D users to cellular frequency bands, and the transmission power control of D2D users and base stations. An effective control method can maximize the communication rate of D2D users while ensuring the quality of service of cellular users, thereby improving the spectrum utilization of cellular resources.

In the traditional centralized algorithm, all D2D devices and cellular users measure and collect channel information and noise information, and then transmit them to the base station for centralized optimization, but the information interaction cost of this method is too high, and as D2D users Changes in channel conditions brought about by changes in relative positions lead to double calculations and inefficiencies. Now a method of coexistence of distributed optimization and a small amount of information interaction is advocated: firstly, the D2D device obtains interference information, channel state information, cellular system and other related information by comprehensively sensing the surrounding wireless environment, and then performs wireless communication autonomously. Resource management, supplemented by the base station to obtain global information, and realize distributed control through a small amount of information interaction.

Contents of the invention

Purpose of the invention: The purpose of the present invention is to provide a power allocation method for maximizing spectrum efficiency in D2D communication. By distributing and optimizing the transmit power of cellular users and the transmit power of D2D users, the minimum service quality requirements of cellular users and the communication between D2D users and cellular users are ensured. Maximize the spectral efficiency of D2D users in the case of user power constraints.

Technical solution: In order to achieve the above-mentioned purpose of the invention, the present invention adopts the following technical solutions:

A power allocation method for maximizing spectrum efficiency in D2D communication, through distributed optimization of the transmit power of cellular users and D2D user transmit power, the maximum Optimize the spectral efficiency of D2D users. Spectrum efficiency refers to the bit rate of data transmitted on a channel of unit bandwidth. In the case of given cellular frequency band resources, maximizing the spectral efficiency of D2D communication is equivalent to maximizing the sum rate of D2D communication. The method comprises the steps of:

(1) The base station sets the initial transmit power matrix z∈R ^N×K of the D2D communication device, where N and K are the total number of D2D user pairs and the total number of available carriers, respectively;

(2) Calculate the approximation coefficient matrix a, b according to z, where a, b∈R ^N×K and

in, is the channel gain from the transmitter of the i-th D2D user pair to the receiver of the i-th D2D user pair on the k-th carrier, is the equivalent channel gain from the transmitter of the jth D2D user pair to the receiver of the ith D2D user pair on the kth carrier, is the equivalent noise power received by the receiver of the i-th D2D user pair on carrier k;

(3) The base station broadcasts the approximation coefficient matrices a, b and the equivalent channel gain and noise to each D2D user pair, and each D2D user pair calculates the transmit power iteratively based on the Lagrangian multiplier method on the condition that the sum power does not exceed the maximum limit , the transmit power of the transmitter of the i-th D2D user pair on carrier k is:

in, is the channel gain from the transmitter of the i-th D2D user pair to the base station on carrier k, is the channel gain of the kth cellular user reaching the base station through carrier k, Indicates the maximum transmission power of the transmitter of the i-th D2D user pair on carrier k, represent numbers in space projection on respectively represent the i and k components of λ ⁿ and μ ⁿ , and λ ⁿ and μ ⁿ respectively represent the values of Lagrange multipliers λ and μ at the nth iteration;

(4) Each D2D user pair feeds back the calculated transmit power to the base station. The base station obtains the transmit power matrix p of the D2D user pair and compares it with the matrix z to determine whether it is converged. If not converged, set z=p and go to step (2 ), if it converges, the base station calculates the transmit power of each cellular user.

Further, the equivalent channel gain in step (2) and equivalent noise Calculate according to the following formula:

in, ρ _k is the QoS limit for the kth cellular user, is the channel gain from the transmitter of the jth D2D user pair to the receiver of the ith user pair on the kth carrier, is the channel gain from the k-th cellular user to the receiving end of the i-th D2D user pair via carrier k; is the noise power received by the receiver of the i-th D2D user pair on carrier k, is the noise power received by the base station on carrier k.

Further, the values of Lagrangian multipliers λ and μ in step (3) are updated according to the following formula:

in, is the step size of the nth iteration, is the maximum sum power limit of the i-th D2D device transmitter, is the maximum transmission power limit of the kth cellular user, [.] ₊ represents the projection on the positive real number space, ρ _k is the QoS limit for the kth cellular user, is the channel gain from the transmitter of the jth D2D user pair to the base station on carrier k, is the noise power received by the base station on carrier k.

Further, the transmit power of the kth cellular user in step (4) is calculated according to the following formula:

Among them, p _jk is the transmitting power of the transmitting end of the jth D2D user pair on the carrier k, is the channel gain from the transmitter of the jth D2D user pair to the base station on carrier k, is the noise power received by the base station on carrier k, ρk is the QoS limit for the _kth cellular user.

Beneficial effects: Compared with the prior art, the power allocation method for maximizing spectrum efficiency in D2D communication provided by the present invention has the following advantages: 1. The method proposed by the present invention can be applied to the scene of multiple D2D users and multiple channels, that is, Any D2D user can use all channels, and any channel can be occupied by all D2D users at the same time, which is universal; 2. The present invention uses a closed-form solution to represent the transmission power of a D2D user, and uses a convex approximation method to approximate a non-convex problem as a The convex optimization problem solved can quickly converge to the optimal solution of the convex problem; 3. The power allocation scheme adopted by the present invention can obtain a better power transmission scheme; 4. The power allocation scheme proposed by the present invention can obtain higher D2D communication Spectrum efficiency; 5. The present invention has the advantages of fast convergence speed, small amount of calculation, easy implementation and high result precision.

Description of drawings

FIG. 1 is a schematic diagram of interference to a D2D communication technology system based on a downlink of a cellular network, where the base station is at coordinates (0,0);

Fig. 2 is a schematic diagram of locations of cellular users and D2D users randomly distributed in a cell;

Fig. 3 is a brief flow chart of the inventive method;

Fig. 4 is the performance schematic diagram of the present invention;

Fig. 5 is a relationship diagram of D2D users and communication rate and service quality requirements of cellular users.

detailed description

The spectral efficiency optimization problem of D2D users is a complex non-convex nonlinear optimization problem. The cellular users targeted by the present invention are uplink multi-channel, and the distributed algorithm can be applied to cellular users with sum power limitation and independent power limitation. D2D In the case of users with combined power constraints, independent power constraints, and cellular users with QoS constraints, the transmit power q of the base station and the transmit power p of D2D users are optimized in a fast distributed manner. The transmission power obtained by adopting the method of the present invention can maximize the spectral efficiency of all D2D users, that is, the sum of the communication rate, under the condition of ensuring the communication rate of the cellular users. The present invention will be further described below.

Assuming that the cellular system has K cellular users and N pairs of D2D users, K cellular users correspond to K cellular frequency bands, and cellular user k corresponds to cellular frequency band k; channel parameters and interference parameters are described as follows:

The channel gain from the transmitter of the i-th D2D user pair to the base station on carrier k, and the cellular user occupying carrier k is also marked as k;

The channel gain of the kth cellular user reaching the base station through carrier k;

The channel gain on the k carrier from the transmitting end of the jth D2D user pair to the receiving end of the ith user pair;

The channel gain of the k-th cellular user reaching the receiving end of the i-th D2D user pair through carrier k;

The noise power received by the receiver of the i-th D2D user pair on carrier k;

The noise power received by the base station on carrier k.

Further define the following parameters:

q represents the transmit power vector of cellular user, q=[q ₁ ,q ₂ ,...,q _k ,...,q _K ], q _k represents the transmit power of cellular user k;

p represents the D2D user transmit power matrix, p=[p ₁₁ ,...,p _1K ; p ₂₁ ,...,p _2K ;...;p _N1 ,...,p _NK ], p _ik represents the D2D user i on the cellular frequency band k transmit power.

ρ _k represents the service quality requirement of cellular user k, that is, the minimum transmission rate;

Indicates the maximum transmission power of the transmitter of the i-th D2D user pair on carrier k;

Indicates the maximum sum power limit of the transmitter of the i-th D2D device;

Indicates the maximum transmission power limit of the kth cellular user;

Among the above parameters, It can be obtained by channel monitoring of the base station; It can be obtained by the receiving end of the D2D user pair through channel monitoring, and transmitted to the base station as required. ρ _k can be given by the base station, is the physical attribute of the D2D user to the i transmitter, is the physical attribute of cellular user k, which can be exchanged to the base station as needed.

As shown in Figure 1, the transmit power q _k of cellular user k and the communication rate of cellular user k are denoted as The communication rate of D2D user i on the cellular frequency band k is denoted as in,

In this system, our optimization goal is to maximize the sum communication rate of all D2D users, namely Since there are multiple users in the cellular network, a minimum quality of service requirement is considered for each cellular user For the uplink, the maximum transmit power of cellular user k is limited to The maximum transmit power of D2D user i on cellular frequency band k is limited to The sum power limit of the D2D user to i transmitter is

In this embodiment, it is assumed that the cell radius is 500 m, the cell frequency band width is 1 MHz, there are 4 cell users, and 2 pairs of D2D users. Set the D2D receivers to be randomly distributed within 20m from the D2D transmitter, the maximum transmit power of the uplink cellular user is 30dBm, the power limit of the D2D user transmit end is set to 20dBm, the D2D sum power limit is set to 25dBm, Gaussian white The noise power spectral density is -174dBm, and the exponential channel fading index is 3.5. As shown in Figure 2, a schematic diagram of random distribution of cellular users and D2D users in a cell.

For the uplink situation shown in Figure 1, we use the following method to obtain the transmit power q of the cellular user and the transmit power p of the D2D user, and obtain the corresponding communication rate of all D2D users

As shown in FIG. 3, a power allocation method for maximizing spectrum efficiency in D2D communication disclosed by an embodiment of the present invention includes the following steps:

Step 1: The base station sets the initial transmit power matrix z∈R ^N×K of the D2D communication device, where N and K are the total number of D2D user pairs and the total number of available carriers, respectively, and the setting accuracy ∈ ₁ = 10 ^-3 and the number of iterations r = 0 .

Step 2: According to the formula

Calculate equivalent channel gain and equivalent noise in the formula ρk is the QoS limit for the _kth cellular user. and is the channel gain from the transmitter of the i-th D2D user pair to the base station on carrier k, is the channel gain of the kth cellular user reaching the base station through carrier k, is the channel gain from the transmitter of the jth D2D user pair to the receiver of the ith user pair on the kth carrier, is the channel gain of the k-th cellular user reaching the receiving end of the i-th D2D user pair through carrier k; is the noise power received by the receiver of the i-th D2D user pair on carrier k, is the noise power received by the base station on carrier k.

Step 3: Calculate the approximation coefficient matrix a, b according to z, and broadcast a, b, where a,b∈R ^N×K and

Step 4: D2D users start to calculate their transmit power after docking with the information broadcast by the base station, set the accuracy ∈ ₂ = 10 ^-4 inner layer iterations n = 0, and initialize the Lagrangian multiplier λ ⁰ = 0(λ∈R ^N ), μ ⁰ =0(μ∈R ^K ). λ ⁿ , μ ⁿ represent the values of Lagrangian multipliers λ and μ at the nth iteration of the inner layer, respectively.

Step 5: According to the formula

Calculate the transmit power of the D2D communication device. in Indicates the maximum transmission power of the transmitter of the i-th D2D user pair on carrier k, represent numbers in space projection on . represent the i and k components of λ ⁿ and μ ⁿ respectively.

Step 6: n←n+1, update the values of λ and μ according to the formula

Wherein, α _n =2/(n+1) is the step size of the nth iteration, is the maximum sum power limit of the i-th D2D device transmitter, is the maximum transmit power limit of the kth cellular user. [.] ₊ denotes a projection onto the space of positive real numbers.

Step 7: If |(λ ⁿ ,μ ⁿ )-(λ ^n-1 ,μ ^n-1 )|<∈ ₁ , feed back transmit power information to the base station and go to step 8, otherwise go to step 5.

Step 8: The base station judges after receiving the power information fed back by all D2D users. If |pz|>∈ ₂ , then set z=p, r←r+1, and go to step 3; otherwise, output the results p and q, where q is the transmit power vector of cellular users, q _k represents the transmit power of the kth cellular user, and

D2D users only need to calculate their own transmission power, and the transmission power of cellular users is finally calculated by the base station and delivered to cellular users. For cellular users, according to the calculation formula, ω _k is a fixed value; is the channel gain of its communication, which can be measured by the base station through its own measuring device; Although it looks very complicated, it can be regarded as noise for the base station, and it can also be directly measured at one time. For D2D users, the above process shows that a distributed algorithm can be realized only by exchanging a, b and a small amount of control information.

As shown in Fig. 4, the method provided by the present invention can converge in about 30 steps, and has a relatively fast rate.

As shown in Figure 5, using the method provided by the present invention, the relationship between the sum communication rate of D2D users and the service quality requirements of cellular users, it can be seen that as the service quality requirements of cellular users continue to increase, the sum communication rate of D2D users keeps decreasing. At the same time, the total sum rate also has a linear relationship with the change of service quality requirements of cellular users.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (4)

1. A power allocation method for maximizing spectral efficiency in D2D communication, comprising: the method comprises the following steps:

(1) base station setting initial transmitting power matrix z ∈ R of D2D communication equipment^N×KN, K are the total number of D2D user pairs and the total number of available carriers, respectively;

(2) computing an approximation coefficient matrix a, b from z, where a, b ∈ R^N×KAnd is

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Wherein,is the channel gain on the kth carrier from the transmitting end of the ith D2D user pair to the receiving end of the ith D2D user pair,is the equivalent channel gain on the kth carrier from the transmitting end of the jth D2D user pair to the receiving end of the ith D2D user pair,the receiving end of the ith D2D user pair receives the equivalent noise power on the carrier k;

(3) the base station broadcasts the approximation coefficient matrixes a and b and equivalent channel gain and noise to each D2D user pair, each D2D user pair iteratively calculates the transmitting power based on a Lagrange multiplier method under the condition that the sum power does not exceed the maximum limit, and the transmitting power of the transmitting end of the ith D2D user pair on a carrier k is as follows:

<mrow> <msub> <mi>p</mi> <mrow> <mi>i</mi> <mi>k</mi> </mrow> </msub> <mo>=</mo> <msubsup> <mrow> <mo>&amp;lsqb;</mo> <mfrac> <msub> <mi>a</mi> <mrow> <mi>i</mi> <mi>k</mi> </mrow> </msub> <mrow> <mi>ln</mi> <mn>2</mn> <mrow> <mo>(</mo> <msubsup> <mi>&amp;lambda;</mi> <mi>i</mi> <mi>n</mi> </msubsup> <mo>+</mo> <mfrac> <mrow> <msubsup> <mi>&amp;mu;</mi> <mi>k</mi> <mi>n</mi> </msubsup> <msubsup> <mi>g</mi> <mrow> <mi>i</mi> <mi>k</mi> </mrow> <mi>c</mi> </msubsup> </mrow> <msubsup> <mi>h</mi> <mi>k</mi> <mi>c</mi> </msubsup> </mfrac> <mo>-</mo> <msubsup> <mi>&amp;Sigma;</mi> <mrow> <mi>j</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>N</mi> </msubsup> <msub> <mi>a</mi> <mrow> <mi>i</mi> <mi>k</mi> </mrow> </msub> <msub> <mi>b</mi> <mrow> <mi>i</mi> <mi>k</mi> </mrow> </msub> <msub> <mover> <mi>g</mi> <mo>~</mo> </mover> <mrow> <mi>i</mi> <mi>j</mi> <mo>,</mo> <mi>k</mi> </mrow> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>&amp;rsqb;</mo> </mrow> <mn>0</mn> <msubsup> <mi>p</mi> <mrow> <mi>i</mi> <mi>k</mi> </mrow> <mi>max</mi> </msubsup> </msubsup> </mrow>

wherein,is the channel gain on carrier k from the transmitting end of the ith D2D user pair to the base station,is the channel gain for the k-th cellular user to reach the base station over carrier k,represents the maximum transmit power on carrier k at the transmitting end of the ith D2D user pair,representing a number in spaceThe projection of the image onto the image plane is performed,respectively represent lambdaⁿ，μⁿThe ith, kComponent, λⁿ，μⁿRespectively representing the values of Lagrange multipliers lambda and mu in the nth iteration;

(4) and (3) feeding the calculated transmission power back to the base station by each D2D user pair, comparing the obtained transmission power matrix p of the D2D user pair with the matrix z by the base station to judge whether convergence occurs, if convergence does not occur, making z equal to p, turning to the step (2), and if convergence occurs, calculating the transmission power of each cellular user by the base station.

2. The method of claim 1, wherein the power allocation method for maximizing spectral efficiency in D2D communication comprises: equivalent channel gain in step (2)And equivalent noiseCalculated according to the following formula:

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wherein,ρ_kis the quality of service limit for the kth cellular user,is the channel gain on the kth carrier from the transmitting end of the jth D2D user pair to the receiving end of the ith user pair,is the channel gain from the kth cellular user over carrier k to the receiving end of the ith D2D user pair;is the noise power received on carrier k at the receiving end of the ith D2D user pair,is the noise power received by the base station on carrier k.

3. The method of claim 1, wherein the power allocation method for maximizing spectral efficiency in D2D communication comprises:

the values of the lagrange multipliers λ and μ in step (3) are updated according to the following formulas:

<mrow> <msubsup> <mi>&amp;lambda;</mi> <mi>i</mi> <mi>n</mi> </msubsup> <mo>=</mo> <msub> <mrow> <mo>&amp;lsqb;</mo> <msubsup> <mi>&amp;lambda;</mi> <mi>i</mi> <mrow> <mi>n</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <msub> <mi>&amp;alpha;</mi> <mi>n</mi> </msub> <mrow> <mo>(</mo> <msubsup> <mi>p</mi> <mi>i</mi> <mrow> <mi>s</mi> <mi>u</mi> <mi>m</mi> </mrow> </msubsup> <mo>-</mo> <munderover> <mi>&amp;Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>K</mi> </munderover> <msub> <mi>p</mi> <mrow> <mi>i</mi> <mi>k</mi> </mrow> </msub> <mo>)</mo> </mrow> <mo>&amp;rsqb;</mo> </mrow> <mo>+</mo> </msub> </mrow>

<mrow> <msubsup> <mi>&amp;mu;</mi> <mi>k</mi> <mi>n</mi> </msubsup> <mo>=</mo> <msub> <mrow> <mo>&amp;lsqb;</mo> <msubsup> <mi>&amp;mu;</mi> <mi>k</mi> <mrow> <mi>n</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mo>-</mo> <msub> <mi>&amp;alpha;</mi> <mi>n</mi> </msub> <mrow> <mo>(</mo> <mfrac> <msubsup> <mi>q</mi> <mi>k</mi> <mi>max</mi> </msubsup> <msub> <mi>&amp;omega;</mi> <mi>k</mi> </msub> </mfrac> <mo>-</mo> <mfrac> <msubsup> <mi>&amp;sigma;</mi> <mi>k</mi> <mi>c</mi> </msubsup> <msubsup> <mi>h</mi> <mi>k</mi> <mi>c</mi> </msubsup> </mfrac> <mo>-</mo> <munderover> <mo>&amp;Sigma;</mo> <mrow> <mi>j</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>N</mi> </munderover> <mfrac> <mrow> <msub> <mi>p</mi> <mrow> <mi>j</mi> <mi>k</mi> </mrow> </msub> <msubsup> <mi>g</mi> <mrow> <mi>j</mi> <mi>k</mi> </mrow> <mi>c</mi> </msubsup> </mrow> <msubsup> <mi>h</mi> <mi>k</mi> <mi>c</mi> </msubsup> </mfrac> <mo>)</mo> </mrow> <mo>&amp;rsqb;</mo> </mrow> <mo>+</mo> </msub> </mrow>

wherein,is the step size of the nth iteration,is the ith D2D device transmit end maximum and power limit,is the maximum transmit power limit for the kth cellular user.]₊Representing a projection onto a positive real space,ρ_kis the quality of service limit for the kth cellular user,is the channel gain on carrier k from the transmitting end of the jth D2D user pair to the base station,is the noise power received by the base station on carrier k.

4. The method of claim 1, wherein the power allocation method for maximizing spectral efficiency in D2D communication comprises: the transmission power of the kth cellular user in the step (4) is calculated according to the following formula:

<mrow> <msub> <mi>q</mi> <mi>k</mi> </msub> <mo>=</mo> <mfrac> <mrow> <msubsup> <mi>&amp;sigma;</mi> <mi>k</mi> <mi>c</mi> </msubsup> <mo>+</mo> <msubsup> <mi>&amp;Sigma;</mi> <mrow> <mi>j</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>N</mi> </msubsup> <msub> <mi>p</mi> <mrow> <mi>j</mi> <mi>k</mi> </mrow> </msub> <msubsup> <mi>g</mi> <mrow> <mi>j</mi> <mi>k</mi> </mrow> <mi>c</mi> </msubsup> </mrow> <msubsup> <mi>h</mi> <mi>k</mi> <mi>c</mi> </msubsup> </mfrac> <msub> <mi>&amp;omega;</mi> <mi>k</mi> </msub> </mrow>

wherein p is_jkIs the transmit power on carrier k of the transmit end of the jth D2D user pair,is the channel gain on carrier k from the transmitting end of the jth D2D user pair to the base station,is the noise power received by the base station on carrier k, ρ_kis the quality of service limit for the kth cellular user.