CN110324844A - A kind of Secondary Users' soaking power distribution method shared based on cooperation NOMA and collaboration frequency spectrum - Google Patents

Abstract

The invention relates to a secondary user strong incentive power allocation method based on cooperative NOMA and cooperative spectrum sharing. The invention maximizes the transmission rate of the SU as a relay by optimizing the power allocation factor of the secondary user NOMA transmission. It can not only effectively increase the total rate of the primary user PU and secondary user SU, improve the spectral efficiency of the system, but also encourage more secondary user SUs to act as the forwarding relay of the primary user PU at the same time, solving the problem of primary user PU and secondary user SU. The conflict of user interests among users SU.

Description

A secondary user strong excitation power distribution based on cooperative NOMA and cooperative spectrum sharing recipe

technical field

The invention relates to a secondary user strong excitation power allocation method based on cooperative NOMA (non-orthogonal multiple access technology) and cooperative spectrum sharing, and belongs to the technical field of communication systems.

Background technique

With the emergence of 5G, the number of mobile devices has increased sharply, and the demand for user access has increased exponentially. However, spectrum resources have become very scarce nowadays. Therefore, the scarcity of spectrum resources and the increasing demand for speed of users have become Now there is a pair of main contradictions in the strategic design of the communication system.

Cooperative spectrum sharing techniques are a promising approach to address spectrum scarcity in wireless communications and have attracted increasing research interest from both industry and academia. In the cooperative spectrum sharing system, a secondary user (SU) without a spectrum access license can obtain a certain spectrum access time by sending a signal of the secondary user (SU) as a relay. Therefore, the spectrum utilization of the entire communication system can be improved through the cooperation between the PU and the SU.

In most existing works related to cooperative spectrum sharing techniques, secondary users (SUs) acting as relays during the cooperative phase mostly work in orthogonal mode. That is, the secondary user (SU) divides the allocated resource (time slot or frequency band resource) into two parts, one part is used for its own transmission, and the other part is dedicated to forwarding information from the primary user (PU). As a result, the secondary user (SU) cannot fully utilize the given spectrum or access time to meet his own needs.

In order to further improve the efficiency of spectrum sharing, non-orthogonal multiple access technology (NOMA) is introduced. Non-orthogonal multiple access (NOMA) is considered to be one of the most attractive technologies in fifth-generation mobile communications (5G), allowing users to share the same frequency spectrum or time slot simultaneously. The basic idea of non-orthogonal multiple access technology (NOMA) is to use non-orthogonal transmission at the transmitting end, different users at the receiving end show different power differences, actively introduce interference information, and then use serial interference cancellation (SIC ) to achieve correct demodulation of different user information. And due to the adoption of continuous interference cancellation at the receiving end, NOMA is very suitable for cooperative communication. Therefore, it is necessary to combine NOMA with cooperative spectrum sharing techniques in an appropriate manner to better utilize spectrum resources.

On the other hand, another important issue in cooperative spectrum sharing technology is relay selection and power allocation. However, most of the existing work adopting cooperative theory to formulate and solve the relay selection or power allocation problem in the downlink NOMA system is to maximize the sum rate, throughput or outage probability of the whole system through a certain optimization strategy Minimization, insufficient consideration of the fairness of resource allocation among users, and does not take into account the unique user requirements of the secondary user (SU) and primary user (PU), resulting in a waste of communication resources. Considering the different needs of users in different scenarios, this is of great research significance at the moment when communication resources are scarce and the number of users is growing rapidly.

Nowadays, there are some studies on cooperative NOMA and cooperative spectrum sharing, and there are also a few studies that consider the behavior between users in combination with related game theory. The principle of NOMA technology is to perform non-orthogonal multiplexing on different user-related communication resources, and use SIC for demodulation at the receiving end, so that more users can share the current communication resources and improve the overall spectrum efficiency of the system. The introduction of the resource allocation must have certain user behavior contradictions. The secondary user as a relay is often selfish. While forwarding information for the primary user, it also wants to meet its own forwarding rate requirements as much as possible. Therefore, primary users need to develop an incentive system to enable more secondary users to actively participate in the forwarding work, while ensuring that their own interests are not lost. Research on user behavior issues is also a focus of NOMA's future research.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a secondary user strong incentive power allocation method based on cooperative NOMA and cooperative spectrum sharing environment;

The present invention studies the performance of the multi-user relay communication system under the cooperative NOMA environment. The present invention mainly studies the problems of power optimization and relay selection in the system. By utilizing the NOMA technology, the present invention effectively improves the total rate of PU and SU, designs a strong incentive system to solve the conflict of interests between SU and PU, and proposes a power allocation algorithm to ensure the basic transmission of PU Based on the rate requirement, the transmission rate of the SU acting as a relay is maximized.

Assuming that the channel state information (CSI) is known, compared with the traditional NOMA static power allocation strategy, the present invention considers the channel condition of downlink transmission to optimize the power allocation factor and forwarding power of the secondary user. And set the minimum transmission rate threshold of the main user to ensure that the performance obtained by the cooperation of the PU as the spectrum resource provider is better than the direct transmission condition. By optimizing the power allocation factor of secondary user NOMA transmission, the transmission rate of SU as a relay can be maximized. It can not only effectively increase the total rate of PUs and SUs, improve the spectral efficiency of the system, but also encourage more SUs to act as forwarding relays of PUs at the same time, and solve the conflict of user interests between PUs and SUs.

Technical scheme of the present invention is:

A secondary user strong incentive power allocation method based on cooperative NOMA and cooperative spectrum sharing, which operates in a cooperative NOMA-based multi-user relay communication system. The cooperative NOMA-based multi-user relay communication system includes a primary user system and a secondary user system, the primary user system refers to the primary user PU, the primary user PU includes a primary transmitter PT and a primary receiver PR, the secondary user system includes K secondary users SU, each secondary user SU includes a transmitter and a A receiver, forming a transmitter-receiver pair, denoted as ST _k -SR _k , the primary user PU is always in the communication state;

The primary user PU has the right to use the access bandwidth, but the channel condition for direct transmission between the PT and the PR is poor. On the other hand, each SU wants to get spectrum access time to send its own signal. But the primary user PU controls the allocation right of the access bandwidth. Therefore, the SU must help the PU to retransmit in order to have a chance to send its own signal. In order to make better use of bandwidth resources, a cooperative transmission strategy is used, which includes two transmission stages: the direct transmission stage and the NOMA cooperative forwarding stage, including the following steps:

(1) The direct transmission stage is carried out in the first half cycle of the cooperative communication period;

For the convenience of analysis, the present invention assumes that any secondary user SU, that is, ST _k -SR _k , is selected as a relay, and the primary transmitter PT of the primary user PU broadcasts its data to the primary receiver PR and the selected secondary user SU as the relay. the transmitter ST _k of the user SU;

The main receiver PR receives the signal y _{PT, PR} , as shown in formula (I):

y _{PT, PR} = h _{PT, PR} x _P + ω _{PT, PR} (I)

In formula (Ⅰ), h _{PT, PR} is the channel gain between the main transmitter PT and the main receiver PR, ω _{PT, PR} is the Gaussian white noise between the main transmitter PT and the main receiver PR, x _P is The signal of the main user PU;

The direct transfer rate achieved by the main receiver PR is:

SNR _{PT, PR} represents the signal-to-noise ratio of the signal sent from the main transmitter PT to the main receiver PR, since the channel condition from the main transmitter PT to the main receiver PR is very poor, resulting in a very small direct transmission rate R _d , so The SU must be selected as a relay for the PU's transmission. The present invention considers that the direct transmission rate R _d realized by the main receiver PR is negligible;

The transmitter ST _k of the secondary user SU receives the signal As shown in formula (II):

In formula (Ⅱ), Gaussian white noise between primary transmitter PT and transmitter ST _k , channel gain between primary transmitter PT and transmitter ST _k ;

(2) The NOMA cooperative forwarding stage is carried out in the second half period of the cooperative communication period;

For the secondary users SU, the invention assumes that each SU successfully decodes the signal received from the primary user PU in the first phase; therefore, the invention focuses more on the secondary user transmitter ST and the primary user receiver PR, Relay procedure between secondary user receivers STk. The transmitter ST _k of the secondary user SU decodes the signal received in the direct transmission phase, and superimposes with its own signal to generate a non-orthogonal signal. The transmitter ST _k of the secondary user SU uses the NOMA transmission method to share the frequency band and time resources, according to the channel gain conditions of the primary user PU and the secondary user SU, the optimal secondary user SU forwarding power Assign different power allocation factors to primary user PU and secondary user SU To distinguish the signals of different users, the upcoming Assigned to the secondary user SU, the distributed to the primary user PU; at the same time, the superimposed non-orthogonal signal is forwarded to the receiver PR of the primary user PU and the receiver SR _k of the secondary user SU, and the receiver SR _k of the secondary user SU and the primary user PU The serial interference cancellation (SIC) method is used at the receiver PR to perform demodulation, and the demodulation includes: first taking the information of the secondary user SU as interference, decoding the information of the primary user PU, and then decoding the information of the secondary user SU; However, there is a certain conflict of interests in this demodulation process. Since the SU is selfish, the SU will not actively consume its own forwarding power to help the PU forward. Therefore, the PU needs to formulate a certain incentive mechanism to induce the SU to forward. The present invention In this demodulation process, the primary user PU rewards SU's forwarding by sharing the authorized spectrum with the secondary user SU and formulating power allocation factors; thus solving the conflict of interests between the two.

The goal of the proposed cooperative NOMA system is to maximize the utility value of selected SUs while satisfying the basic transmission rate condition of PUs. The invention proposes an optimization algorithm for joint optimization of transmission power and power division factor. The objective function and constraints C1-C3 of maximizing the utility value of the selected secondary user SU while satisfying the basic transmission rate condition of the primary user PU are shown in formula (Ⅲ):

In formula (Ⅲ), U _SU refers to the utility value of the secondary user SU, refers to the transmission rate obtained by the receiver SR _k of the kth secondary user, α _1k refers to the power allocation factor of the primary user PU, α _2k refers to the power allocation factor of the secondary user SU, λ _k refers to the secondary user The unit power consumption cost of the SU, P _k is the forwarding power of the secondary user SU in the transmission, P _MAX is the power limit of the secondary user’s forwarding power; U _PU is the utility value of the primary user PU, and R _V is the The primary user PU obtains the required rate through NOMA cooperative transmission during the NOMA cooperative forwarding phase;

C1 indicates that the utility value obtained by the primary user PU in the multi-user relay communication system based on cooperative NOMA is greater than its own required transmission rate R _V ; C2 indicates that the power allocation factor is reasonable and the power allocation factor of the primary user PU is always greater than The power allocation factor of the secondary user SU; C3 indicates that the forwarding power of the secondary user SU does not exceed P _MAX ;

Calculate the optimal secondary user SU forwarding power by formula (Ⅲ) The optimal power allocation factor of the primary user PU and the power allocation factor of the secondary user SU Power allocation factor Respectively as shown in formula (IV), (V), (VI):

In formulas (Ⅳ), (Ⅴ) and (Ⅵ), γ refers to the transmission signal-to-interference ratio required by the primary user PU itself, Denotes the ratio of channel gain to noise power between the transmitter ST _k of the secondary user SU and the primary receiver PR of the primary user PU, Indicates the ratio of channel gain to noise power between the transmitter ST _k of the secondary user SU and the receiver SR _k of the secondary user SU.

The present invention solves the optimal SU forwarding power when selecting any SU as a relay Optimal Power Allocation Factor for Primary User PU and the power allocation factor of the secondary user SU Power allocation factor The optimal resource allocation scheme of the system when each SU as a relay relay is cooperatively transmitted can be obtained.

The specific process is as follows:

1. Assuming that the channel state is known, the primary user PU broadcasts a cooperative forwarding request to all secondary users SU that can be used as alternate relays, indicating that they need to seek a relay for cooperative NOMA transmission. According to formula (Ⅴ), (Ⅵ) Give a power allocation factor scheme

2. If the kth secondary user SU wants to perform cooperative transmission, according to formula (IV), calculate the optimal secondary user SU forwarding power And report the PU.

3. The primary user PU receives the best secondary user SU forwarding power reported by all k secondary user SUs Select the cooperative NOMA-based multi-user relay communication system and the secondary user SU with the highest rate as the relay.

Preferably, according to the present invention, in the NOMA cooperative forwarding stage, the reasoning process of the objective function is as follows:

Sequential Interference Cancellation (SIC) is applied to the primary receiver PR and receiver SR to decode non-orthogonal NOMA signals. For the primary user PU, the information transmission rate obtained at the primary receiver PR is shown in Equation (VII):

In formula (Ⅶ), σ ² is the noise power, is the channel gain from the transmitter ST _k to the primary receiver PR, α _1k is the power allocation factor of the primary user PU, and α _2k is the power allocation factor of the secondary user SU; P _k is the power allocation factor of the secondary user SU in this transmission forwarding power;

For the primary user PU, due to the poor channel condition between PT and PR, the present invention considers that the direct transmission rate R _d is negligible, and the primary user PU needs to obtain the required rate through NOMA cooperative transmission in the NOMA cooperative forwarding stage as R _V ,definition γ is the required SINR (signal to interference plus noise ratio) of the primary user PU;

The utility function of the primary user PU is shown in formula (Ⅷ):

It can be seen that only when the direct transfer rate is small, the PU will seek relay transfer.

For the secondary user SU, the information transmission rate obtained at the receiver SR _k is shown in equation (IX):

In formula (Ⅸ), ^σ2 is the noise power, is the channel gain from transmitter ST _k to receiver SR _k ;

Therefore, the utility function of the secondary user SU is shown in formula (Ⅹ):

In formula (Ⅹ), λ _k is the unit power consumption cost of SU;

Since SU is selfish and rational, there is no obligation to waste power resources to help PU forward information. In the proposed system, in order to motivate the SU, the present invention maximizes the utility value of the secondary user SU, while for the primary user PU, it only needs to satisfy the transmission rate of the PU to reach the requirement R _V , and R _V is always greater than the direct transmission rate R _d ;

The goal of the proposed cooperative NOMA system is to maximize the utility value of the selected secondary user SU while satisfying the basic transmission rate condition of the primary user PU. The present invention proposes an optimization algorithm that jointly optimizes the transmission power and power division factor. The objective function and restrictive conditions C1-C3 are shown in formula (Ⅲ):

According to the preferred and optimal SU forwarding power of the present invention The optimal power allocation factor of the primary user PU and the power allocation factor of the secondary user SU Power allocation factor That is, the reasoning process of formulas (Ⅳ), (Ⅴ) and (Ⅵ) is as follows:

Substituting the constraint condition C2 into U _PU and U _SU , the formulas (Ⅺ) and (Ⅻ) are obtained:

The utility function of the secondary user SU is increasing with respect to α _2k , obtained according to formula (Ⅺ) Therefore, the secondary user SU is only available on Only when there is the maximum utility value, at this time, the income of PU is equal to R _V ;

Although the revenue of PU is equal to R _V at this time, PU still gets a higher transfer rate than direct transfer. So the PU can still gain from cooperative transmission. The present invention can simplify optimization problem formula (Ⅲ), obtain formula (ⅩⅢ):

stP _{k ≤} P _MAx

Best SU forwarding power , the maximum utility of the secondary user SU is shown in formula (ⅩⅣ):

The first-order reciprocal and the second-order reciprocal of formula (XIV) are solved, respectively, as shown in formula (XV) (XVI):

Equation (XVI) is always negative, and it can be concluded that when Equation (XV) is zero, the maximum utility value is obtained. Therefore, the optimal SU forwarding power is calculated The optimal power allocation factor of the primary user PU and the power allocation factor of the secondary user SU Power allocation factor As shown in formulas (IV), (V), and (VI):

Preferably according to the present invention, in order to maximize the throughput of the entire system, select the secondary user SU _select that makes the sum rate maximum as a relay, so as to achieve the purpose of improving the overall system performance, as shown in formula (XVII):

In the formula (XVII), κ={1, 2, ..., K} represents the set of K secondary users who can be selected as relays, Refers to the utility value obtained by the primary user PU when the kth secondary user is selected as the relay, refers to the utility value obtained by the secondary user SU when the kth secondary user is selected as the relay.

The beneficial effects of the present invention are:

1. The power-optimized relay selection method in the cooperative NOMA cooperative spectrum sharing system of the present invention, by analyzing the transmission rate of the cooperative NOMA system and utilizing the properties of the logarithmic function, a corresponding utility function and an optimization problem are constructed, and the The optimization problem studied obtains the optimal solution through a low-complexity solving algorithm, and finally achieves the goal of maximizing the sum rate of the system.

2. The present invention considers the fairness and balance of resource allocation between users, fully considers the unique user needs of secondary users (SU) and primary users (PU), and gives sufficient incentives to SUs to make SUs actively strive for The right to act as a relay makes the design of the communication system more reasonable.

Description of drawings

Fig. 1 is a schematic diagram of a multi-user relay communication system model based on cooperative NOMA in the present invention;

Fig. 2 is a schematic diagram of the simulation results of the ideal power allocation factor changing with the SINR demanded by the primary user PU;

Fig. 3 is a schematic diagram of the simulation results of the ideal SU relay power changing with the SINR demanded by the primary user PU;

Figure 4 is a schematic diagram of the comparison of the total utility value and the random strategy.

Detailed ways

The present invention will be further limited below in conjunction with the accompanying drawings and embodiments, but not limited thereto.

Example 1

A secondary user strong incentive power allocation method based on cooperative NOMA and cooperative spectrum sharing, which operates in a multi-user relay communication system based on cooperative NOMA, as shown in Figure 1, the multi-user relay communication system based on cooperative NOMA includes the main The user system and the secondary user system, the primary user system refers to the primary user PU, the primary user PU includes a primary transmitter PT and a primary receiver PR, the secondary user system includes K secondary users SU, each secondary user SU includes a transmitter and a receiver, forming a transmitter-receiver pair, denoted as ST _k -SR _k , and the primary user PU is always in the communication state;

The primary user PU has the right to use the access bandwidth, but the channel condition for direct transmission between the PT and the PR is poor. On the other hand, each SU wants to get spectrum access time to send its own signal. But the primary user PU controls the allocation right of the access bandwidth. Therefore, the SU must help the PU to retransmit in order to have a chance to send its own signal. In order to make better use of bandwidth resources, a cooperative transmission strategy is used, which includes two transmission stages: the direct transmission stage and the NOMA cooperative forwarding stage, including the following steps:

(1) The direct transmission stage is carried out in the first half cycle of the cooperative communication period;

For the convenience of analysis, the present invention assumes that any secondary user SU, that is, ST _k -SR _k , is selected as a relay, and the primary transmitter PT of the primary user PU broadcasts its data to the primary receiver PR and the selected secondary user SU as the relay. the transmitter ST _k of the user SU;

The main receiver PR receives the signal y _{PT, PR} , as shown in formula (I):

y _{PT, PR} = h _{PT, PR} x _P + ω _{PT, PR} (I)

In formula (Ⅰ), h _{PT, PR} is the channel gain between the main transmitter PT and the main receiver PR, ω _{PT, PR} is the Gaussian white noise between the main transmitter PT and the main receiver PR, x _P is The signal of the main user PU;

The direct transfer rate achieved by the main receiver PR is:

SNR _{PT, PR} represents the signal-to-noise ratio of the signal sent from the main transmitter PT to the main receiver PR, since the channel condition from the main transmitter PT to the main receiver PR is very poor, resulting in a very small direct transmission rate R _d , so The SU must be selected as a relay for the PU's transmission. The present invention considers that the direct transmission rate R _d realized by the main receiver PR is negligible;

The transmitter ST _k of the secondary user SU receives the signal As shown in formula (II):

In formula (Ⅱ), Gaussian white noise between primary transmitter PT and transmitter ST _k , channel gain between primary transmitter PT and transmitter ST _k ;

(2) The NOMA cooperative forwarding stage is carried out in the second half period of the cooperative communication period;

For the secondary users SU, the invention assumes that each SU successfully decodes the signal received from the primary user PU in the first phase; therefore, the invention focuses more on the secondary user transmitter ST and the primary user receiver PR, Relay procedure between secondary user receivers STk. The transmitter ST _k of the secondary user SU decodes the signal received in the direct transmission phase, and superimposes with its own signal to generate a non-orthogonal signal. The transmitter ST _k of the secondary user SU uses the NOMA transmission method to share the frequency band and time resources, according to the channel gain conditions of the primary user PU and the secondary user SU, the optimal secondary user SU forwarding power Assign different power allocation factors to the secondary user SU and the primary user PU To distinguish the signals of different users, the upcoming Assigned to the secondary user SU, the distributed to the primary user PU; at the same time, the superimposed non-orthogonal signal is forwarded to the receiver PR of the primary user PU and the receiver SR _k of the secondary user SU, and the receiver SR _k of the secondary user SU and the primary user PU The serial interference cancellation (SIC) method is used at the receiver PR to perform demodulation, and the demodulation includes: first taking the information of the secondary user SU as interference, decoding the information of the primary user PU, and then decoding the information of the secondary user SU; However, there is a certain conflict of interests in this demodulation process. Since the SU is selfish, the SU will not actively consume its own forwarding power to help the PU forward. Therefore, the PU needs to formulate a certain incentive mechanism to induce the SU to forward. The present invention In this demodulation process, the primary user PU rewards SU's forwarding by sharing the authorized spectrum with the secondary user SU and formulating power allocation factors; thus solving the conflict of interests between the two.

The goal of the proposed cooperative NOMA system is to maximize the utility value of selected SUs while satisfying the basic transmission rate condition of PUs. The invention proposes an optimization algorithm for joint optimization of transmission power and power division factor. The objective function and constraints C1-C3 of maximizing the utility value of the selected secondary user SU while satisfying the basic transmission rate condition of the primary user PU are shown in formula (Ⅲ):

In formula (Ⅲ), U _SU refers to the utility value of the secondary user SU, refers to the transmission rate obtained by the receiver SR _k of the kth secondary user, α _1k refers to the power allocation factor of the primary user PU, α _2k refers to the power allocation factor of the secondary user SU, λ _k refers to the secondary user The unit power consumption cost of the SU, P _k is the forwarding power of the secondary user SU in the transmission, P _MAX is the power limit of the secondary user’s forwarding power; U _PU is the utility value of the primary user PU, and R _V is the The primary user PU obtains the required rate through NOMA cooperative transmission during the NOMA cooperative forwarding phase;

C1 indicates that the utility value obtained by the primary user PU in the multi-user relay communication system based on cooperative NOMA is greater than its own required transmission rate R _V ; C2 indicates that the power allocation factor is reasonable and the power allocation factor of the primary user PU is always greater than The power allocation factor of the secondary user SU; C3 indicates that the forwarding power of the secondary user SU does not exceed P _MAX ;

Calculate the optimal secondary user SU forwarding power by formula (Ⅲ) The optimal power allocation factor of the primary user PU and the power allocation factor of the secondary user SU Power allocation factor Respectively as shown in formula (IV), (V), (VI):

In formulas (Ⅳ), (Ⅴ) and (Ⅵ), γ refers to the transmission signal-to-interference ratio required by the primary user PU itself, Denotes the ratio of channel gain to noise power between the transmitter ST _k of the secondary user SU and the primary receiver PR of the primary user PU, Indicates the ratio of channel gain to noise power between the transmitter ST _k of the secondary user SU and the receiver SR _k of the secondary user SU.

The present invention solves the optimal SU forwarding power when selecting any SU as a relay Optimal Power Allocation Factor for Primary User PU and the power allocation factor of the secondary user SU Power allocation factor The optimal resource allocation scheme of the system when each SU as a relay relay is cooperatively transmitted can be obtained.

The specific process is as follows:

1. Assuming that the channel state is known, the primary user PU broadcasts a cooperative forwarding request to all secondary users SU that can be used as alternate relays, indicating that they need to seek a relay for cooperative NOMA transmission. According to formula (Ⅴ), (Ⅵ) Give a power allocation factor scheme

2. If the kth secondary user SU wants to perform cooperative transmission, according to formula (IV), calculate the optimal secondary user SU forwarding power And report the PU.

3. The primary user PU receives the best secondary user SU forwarding power reported by all k secondary user SUs Select the cooperative NOMA-based multi-user relay communication system and the secondary user SU with the highest rate as the relay.

In the NOMA cooperative forwarding stage, the reasoning process of the objective function is as follows:

Sequential Interference Cancellation (SIC) is applied to the primary receiver PR and receiver SR to decode non-orthogonal NOMA signals. For the primary user PU, the information transmission rate obtained at the primary receiver PR is shown in Equation (VII):

In formula (Ⅶ), σ ² is the noise power, is the channel gain from the transmitter ST _k to the primary receiver PR, α _1k is the power allocation factor of the primary user PU, and α _2k is the power allocation factor of the secondary user SU; P _k is the power allocation factor of the secondary user SU in this transmission forwarding power;

For the primary user PU, due to the poor channel condition between PT and PR, the present invention considers that the direct transmission rate R _d is negligible, and the primary user PU needs to obtain the required rate through NOMA cooperative transmission in the NOMA cooperative forwarding stage as R _V ,definition γ is the required SINR (signal to interference plus noise ratio) of the primary user PU;

The utility function of the primary user PU is shown in formula (Ⅷ):

It can be seen that only when the direct transfer rate is small, the PU will seek relay transfer.

For the secondary user SU, the information transmission rate obtained at the receiver SR _k is shown in equation (IX):

In formula (Ⅸ), ^σ2 is the noise power, is the channel gain from transmitter ST _k to receiver SR _k ;

Therefore, the utility function of the secondary user SU is shown in formula (Ⅹ):

In formula (Ⅹ), λ _k is the unit power consumption cost of SU;

Since SU is selfish and rational, there is no obligation to waste power resources to help PU forward information. In the proposed system, in order to motivate the SU, the present invention maximizes the utility value of the secondary user SU, while for the primary user PU, it only needs to satisfy the transmission rate of the PU to reach the requirement R _V , and R _V is always greater than the direct transmission rate R _d ;

The goal of the proposed cooperative NOMA system is to maximize the utility value of the selected secondary user SU while satisfying the basic transmission rate condition of the primary user PU. The present invention proposes an optimization algorithm that jointly optimizes the transmission power and power division factor. The objective function and restrictive conditions C1-C3 are shown in formula (Ⅲ):

Best SU forwarding power The optimal power allocation factor of the primary user PU and the power allocation factor of the secondary user SU Power allocation factor That is, the reasoning process of formulas (Ⅳ), (Ⅴ) and (Ⅵ) is as follows:

Substituting the constraint condition C2 into U _PU and U _SE , formula (Ⅺ) and formula (Ⅻ) are obtained:

The utility function of the secondary user SU is increasing with respect to α _2k , obtained according to formula (Ⅺ) Therefore, the secondary user SU is only available on Only when there is the maximum utility value, at this time, the income of PU is equal to R _V ;

Although the revenue of PU is equal to R _V at this time, PU still gets a higher transfer rate than direct transfer. So the PU can still gain from cooperative transmission. The present invention can simplify optimization problem formula (Ⅲ), obtain formula (ⅩⅢ):

stP _{k ≤} P _MAX

Best SU forwarding power , the maximum utility of the secondary user SU is shown in formula (ⅩⅣ):

The first-order reciprocal and the second-order reciprocal of formula (XIV) are solved, respectively, as shown in formula (XV) (XVI):

Equation (XVI) is always negative, and it can be concluded that when Equation (XV) is zero, the maximum utility value is obtained. Therefore, the optimal SU forwarding power is calculated The optimal power allocation factor of the primary user PU and the power allocation factor of the secondary user SU Power allocation factor As shown in formulas (IV), (V), and (VI):

The performance of a system based on cooperative NOMA and cooperative spectrum sharing proposed in this embodiment is shown in FIGS. 2 , 3 and 4 . By comparing with random relay selection, 5 SU relays are taken as an example. Figure 2 shows the ideal power distribution factor for the system Variation of SINR with PU demand. It can be observed that a PU with a high demand rate will get a larger power allocation factor and assign a smaller factor to SU In Figure 3, the present invention illustrates the required SINR of the PU versus the contribution of the SU to the relay power The relationship between. The higher the transmission required by the PU itself, the power consumed by SU forwarding less. Even though the PU will allocate a larger power allocation factor when it needs a larger rate, the SU will reduce the To reduce their own losses, which also reflects SU's selfishness. This also shows the conflict of interests between PU and SU, and the most favorable point of both is found in the mutual game between the two. In Fig. 4, the present invention compares the sum utility values of the proposed scheme and the random scheme. It can be seen that the total utility value of PU and SU is always higher than that of the random scheme. This proves that the scheme of the present invention can solve the optimal power allocation factor and SU forwarding power To make the whole system get better performance.

Example 2

According to Embodiment 1, a secondary user strong incentive power allocation method based on cooperative NOMA and cooperative spectrum sharing, the difference is that in order to maximize the throughput of the entire system, the secondary user SU _select that maximizes the sum rate is selected As a relay, the purpose of improving the overall system performance can be achieved, as shown in formula (XVII):

In the formula (XVII), κ={1, 2, ..., K} represents the set of K secondary users who can be selected as relays, Refers to the utility value obtained by the primary user PU when the kth secondary user is selected as the relay, refers to the utility value obtained by the secondary user SU when the kth secondary user is selected as the relay.

Claims (4)

1. a kind of Secondary Users' soaking power distribution method shared based on cooperation NOMA and collaboration frequency spectrum, is run on based on conjunction The multi-user's relay communications system for making NOMA, based on cooperation NOMA multi-user's relay communications system include main users system and Secondary Users' system, main users system refer to that primary user PU, primary user PU include a master transmitter PT and a main reception Machine PR, Secondary Users' system include that K Secondary Users SU, each Secondary Users SU include a transmitter and a receiver, Transmitter-receiver pair is formed, ST is expressed as_k-SR_k, primary user PU is in communications status always；It is characterised in that it includes two The transmission stage: directly the transmission stage cooperates the forwarding stage with NOMA, comprises the following steps that

(1) stage is directly transmitted, is carried out in the preceding half period of collaboration communication period；

Select any one Secondary Users SU i.e. ST_k-SR_kAs relaying, the master transmitter PT of primary user PU arrives its data broadcasting The transmitter ST of main receiver PR and the selected Secondary Users SU as relaying_k；

Main receiver PR receives signal y_{PT, PR}, as shown in formula (I):

y_{PT, PR}=h_{PT, PR}x_P+ω_{PT, PR}(I)

In formula (I), h_{PT, PR}For the channel gain between master transmitter PT and main receiver PR, ω_{PT, PR}For master transmitter PT and master White Gaussian noise between receiver PR, x_PFor the signal of primary user PU；

The direct transmission rate R that main receiver PR is realized_dIt ignores；

The transmitter ST of Secondary Users SU_kReceive signalAs shown in formula (II):

In formula (II),For master transmitter PT and transmitter ST_kBetween white Gaussian noise,For master transmitter PT With transmitter ST_kBetween channel gain；

(2) NOMA cooperates the forwarding stage, carries out in the second half of the cycle of collaboration communication period；

Assuming that each Secondary Users SU is successfully decoded in the first phase from primary user's PU received signal；The hair of Secondary Users SU Send machine ST_kTo in the direct transmission stage received signal be decoded, and with the Signal averaging of oneself generate non-orthogonality signal, The transmitter ST of Secondary Users SU_kUsing the transmission mode of NOMA, share frequency band and time resource, by according to primary user PU and The channel gain condition of Secondary Users SU, by optimal Secondary Users SU repeating powerTo primary user PU and Secondary Users SU points With different power allocation factorsIt distinguishes the signal of different user, i.e., willSecondary Users SU is distributed to, it willDistribute to primary user PU；The non-orthogonality signal that superposition generates is forwarded to the receiver PR of primary user PU and secondary simultaneously The receiver SR of user SU_k, and in the receiver SR of Secondary Users SU_kWith at the receiver PR of primary user PU use serial interference The method of elimination is demodulated, and demodulation includes: to decode the information of primary user PU first by the information of Secondary Users SU as interference, The information of further decoding Secondary Users SU；In this demodulating process primary user PU pass through and the shared authorization frequency spectrum of Secondary Users SU and Power allocation factor is formulated to reward the forwarding of SU；

The target letter of the value of utility of selected Secondary Users SU is maximized while meeting the basic transmission rate condition of primary user PU Shown in several and restrictive condition C1-C3 such as formula (III):

In formula (III), U_SURefer to the value of utility of Secondary Users SU,Refer to the receiver SR in k-th user_kIt obtains Transmission rate, α_1kRefer to the power allocation factor of primary user PU, α_2kRefer to the power allocation factor of Secondary Users SU, λ_kRefer to The unit work consumptiom cost of Secondary Users SU, P_kFor the repeating power of the Secondary Users SU in the transmission, P_MAXRefer to that Secondary Users turn Send out the power limit of power；U_PURefer to the value of utility of primary user PU, R_VRefer to that primary user PU passes through in the NOMA cooperation forwarding stage NOMA cooperation transmission obtains required rate；

C1 indicates that the value of utility that primary user PU is obtained in multi-user's relay communications system based on cooperation NOMA is greater than itself institute The transmission rate R needed_V；C2 indicates that power allocation factor is reasonable and the power allocation factor of primary user PU is always greater than secondary Want the power allocation factor of user SU；C3 indicates that the repeating power of Secondary Users SU is no more than P_MAX；

Optimal Secondary Users SU repeating power is calculated by formula (III)The power allocation factor of optimal primary user PUAnd the power allocation factor power allocation factor of Secondary Users SURespectively as shown in formula (IV), (V), (VI):

Formula (IV), (V), in (VI), γ refers to transmission letter drying ratio required for primary user PU itself,It indicates The transmitter ST of Secondary Users SU_kThe ratio of channel gain and noise power between the main receiver PR of primary user PU,Indicate the transmitter ST of Secondary Users SU_kWith the receiver SR of Secondary Users SU_kBetween channel gain and make an uproar The ratio of acoustical power.

2. a kind of Secondary Users' soaking power point shared based on cooperation NOMA and collaboration frequency spectrum according to claim 1 Method of completing the square, which is characterized in that selection is so that with the maximum Secondary Users SU of rate_selectAs relaying, as shown in formula (X VII):

In formula (X VII),Indicate the set of the K alternative Secondary Users for relaying,Refer to selection kth The value of utility that main users PU is obtained when a Secondary Users are as relaying,Refer to select k-th of Secondary Users as relaying when The value of utility that Secondary Users SU is obtained.

3. a kind of Secondary Users' soaking power point shared based on cooperation NOMA and collaboration frequency spectrum according to claim 1 Method of completing the square, which is characterized in that NOMA cooperates the forwarding stage, the rate of information throughput such as formula (VII) institute obtained at main receiver PR Show:

In formula (VII),σ²For noise power,For from transmitter ST_kTo the channel of main receiver PR Gain, α_1kIt is the power allocation factor of primary user PU, α_2kIt is the power allocation factor of Secondary Users SU；P_kFor time in the transmission Want the repeating power of user SU；

For primary user PU, direct transmission rate R_dIt ignores, setting primary user PU needs to pass through in the NOMA cooperation forwarding stage Rate needed for NOMA cooperation transmission obtains is R_V, definitionγ is the required of primary user PU SINR；

Shown in the utility function of primary user PU such as formula (VIII):

For Secondary Users SU, in receiver SR_kShown in the rate of information throughput that place obtains such as formula (IX):

In formula (IX),σ²It is noise power,For from transmitter ST_kTo receiver SR_kChannel Gain；

Shown in the utility function of Secondary Users SU such as formula (X):

In formula (X), λ_kFor the unit work consumptiom cost of SU；

The value of utility of Secondary Users SU is maximized, and for primary user PU, it is only necessary to the transmission rate for meeting PU reaches demand R_V, And R_VAlways greater than direct transmission rate R_d；

The value of utility of selected Secondary Users SU, target letter are maximized while the basic transmission rate condition for meeting primary user PU Shown in number, restrictive condition C1-C3 such as formula (III):

4. a kind of Secondary Users' soaking shared based on cooperation NOMA and collaboration frequency spectrum according to claim 1 to 3 Power distribution method, which is characterized in that restrictive condition C2 is updated to U_PUAnd U_SU, obtain formula (XI), formula (XII):

The utility function of Secondary Users SU is about α_2kIncremental, it is obtained according to formula (XI)Therefore, secondary User SU is wanted only to existShi Caiyou maximum utility value, at this point, the income of PU is equal to R_V；

Simplify optimization problem formula (III), obtain formula (XIII):

Optimal SU repeating powerUnder, shown in the maximum utility of Secondary Users SU such as formula (Ⅹ IV):

Its single order inverse is solved to formula (Ⅹ IV) and second order is reciprocal, respectively as shown in formula (Ⅹ V) (Ⅹ VI):

Formula (Ⅹ VI) perseverance is negative, it was therefore concluded that: maximum value of utility is obtained when formula (Ⅹ V) is zero, therefore, is calculated Optimal SU repeating powerThe power allocation factor of optimal primary user PUAnd the power allocation factor of Secondary Users SU Power allocation factorAs shown in formula (IV), (V), (VI):