阅读说明：本技术 一种基于能量效率与频谱效率的联合折中优化方法 (Combined compromise optimization method based on energy efficiency and spectrum efficiency ) 是由 李同强 李璇 于 2018-07-02 设计创作，主要内容包括：本发明公开了一种基于能量效率与频谱效率的联合折中优化方法。采用一种基于合约制的协作频谱共享新模型。在该模型中当主用户信道质量较差时,次用户为其提供中继服务；作为回报,在主用户信道质量良好时,次用户可以在一定的干扰约束下以underlay的模式和主用户共享频谱。在此框架下引入合约理论,将主次用户间的协作问题建模为合约设计问题,并建立了主次用户评价合约收益的效用函数,将提高主用户的能效和谱效问题转换为设计合约使主用户获得最大效用的优化问题,并利用差分进化算法进行求解。(The invention discloses a joint compromise optimization method based on energy efficiency and spectrum efficiency. A cooperative spectrum sharing new model based on joint reduction is adopted. In the model, when the quality of a main user channel is poor, a secondary user provides relay service for the main user channel; in return, when the primary user channel quality is good, the secondary user may share the spectrum with the primary user in an underlay mode under a certain interference constraint. A contract theory is introduced under the framework, a cooperation problem between primary and secondary users is modeled into a contract design problem, a utility function of evaluating contract benefits of the primary and secondary users is established, the problems of improving the energy efficiency and the spectral efficiency of the primary user are converted into an optimization problem of designing a contract to enable the primary user to obtain the maximum utility, and a differential evolution algorithm is utilized to solve the optimization problem.)

1. A joint compromise optimization method based on energy efficiency and spectrum efficiency is characterized in that: the method comprises the following steps: the method comprises the steps of modeling a cooperation problem between primary and secondary users into a contract design problem by adopting a contract theory in economics, establishing a utility function for evaluating contract benefits of the primary and secondary users, converting the problem of improving the energy efficiency and the spectral efficiency of a primary user into an optimization problem for designing a contract to enable the primary user to obtain the maximum utility, and solving by adopting a differential evolution algorithm.

2. The method of claim 1, wherein the method comprises the following steps:

the model based on the contract theory is specifically as follows:

in a cooperative spectrum sharing mechanism, a primary user and a secondary user have resource exchange. The main factors influencing the income of both transaction parties are relay power, a channel gain threshold value of relay service and interference constraint of a secondary user on a primary user in a spectrum sharing stage. Due to the contradiction between the primary user and the secondary user, if the two cooperative parties want to achieve respective maximum utility in resource exchange, the two cooperative parties are attracted to active and active cooperation depending on whether an effective incentive mechanism exists or not. In a contract theory model, the problem that a primary user and a secondary user hope to obtain respective maximum utility from resource exchange is converted into the design problem of the optimal contract problem of the primary user. The secondary user passively selects the optimal contract, so that the optimal contract design problem is converted into the problem of how the primary user designs the contract to enable the primary user to obtain the maximum utility.

3. The joint compromise optimization method based on energy efficiency and spectral efficiency according to claim 2, characterized in that:

(1) the main user utility function is specifically:

in the cooperative relay stage 1, a master user sends data to a receiving end of the master user and a transmitting end of a secondary user, and an expected expression of a data transmission rate of the master user is as follows:

wherein, P₀As the transmission power of the primary user, n₀The noise power of a primary user receiving end and the Rayleigh distribution with the obeying parameter of sigma between the primary user and the secondary user are h^*The pr is the probability that the secondary user provides relay service for the primary user, which is the channel gain threshold.

In the cooperative relay stage 2, the secondary user provides a relay service for the primary user, and the data transmission rate of the primary user is as follows:

wherein, P is the power of the secondary user forwarding signal received by the primary user receiving end.

In the spectrum sharing stage, a master user sends data under the interference of a secondary user, and the expected data transmission rate R of the master user₃：

Wherein, α is the ratio of the interference power allowed by the primary user to the secondary user to the power of the secondary user transmitted signal received by the primary user receiving end.

The expectation of the average data transmission rate of the master user as a whole is:

defining the expectation of the data transmission rate of the main user as a utility function U of the main user_p

U_p＝R_E

(2) The secondary user utility function is specifically:

the secondary user sends information at the maximum power allowed by the primary user in the spectrum sharing stage, and the transmission rate expectation R of the data of the secondary user is sent in the whole process_sComprises the following steps:

wherein h is₁Channel gain h from the transmitting end of the secondary user to the receiving end of the primary user₂For the channel gain from the transmitting end of the secondary user to the receiving end of the secondary user, h₃Channel gain, n, for primary user transmitting end to secondary user receiving end₁Is the noise power at the receiving end of the secondary user.

In the whole process, the total power consumed by the main user is expected to be as follows:

wherein, P/(2 h)₁) Representing the average power of the secondary users during the writing phase, ap/h₁Indicating the transmission power of the secondary user for transmitting its own data.

Defining a transmission rate expectation R for a secondary user to send own data_sSubtracting cost of consumption as utility function U of secondary user_sThe expression is as follows:

where C represents the cost of the secondary user to consume a unit of energy, generally determined by the energy conversion efficiency of the battery.

(3) The optimization contract design function is:

the personal rational constraint means that the secondary user performs cooperative spectrum sharing with the primary user only under the condition that the secondary user obtains non-negative utility. Namely, the following conditions are satisfied:

Technical Field

The invention relates to the field of cognitive radio, in particular to a joint compromise optimization method based on energy efficiency and spectrum efficiency.

Background

With the rapid growth of wireless networks and services, whether for commercial or military applications, there is a need to achieve high data transmission rates with existing spectrum resources. Therefore, the scarcity of spectrum resources becomes a problem to be solved urgently. Spectral efficiency, defined as the net bit rate (useful information rate, excluding error correction codes) or maximum throughput divided by the bandwidth (in hertz) of a communication channel or data link, is higher, the higher the spectral efficiency the higher the data rate for a given spectral bandwidth. On the other hand, to quantify the power consumption of information transmission, the energy efficiency is defined as the number of information bits successfully transmitted from the transmitting end to the receiving end with unit energy consumption, and the higher the energy efficiency is, the more information can be transmitted for a fixed energy resource.

At present, mobile devices such as mobile phones, tablets and sensors, the number of which is continuously and rapidly increasing, need to transmit a large amount of data on one hand, and have higher requirements on size, weight, power consumption and the like in order to improve the adaptability of the mobile devices in different application scenarios on the other hand. To achieve higher spectral efficiency, efficient use of spectral resources, requires more packets to be successfully transmitted, but also consumes more energy, resulting in a loss of energy efficiency, and vice versa. Therefore, the optimization of the joint compromise between energy efficiency and spectrum efficiency becomes a problem worthy of study.

Disclosure of Invention

The invention aims to provide an optimal power allocation method aiming at maximizing the energy efficiency and the spectrum efficiency of a cognitive user in a cognitive radio network.

In order to achieve the purpose, the invention adopts the following technical scheme:

a combined compromise optimization method based on energy efficiency and spectrum efficiency is provided, and a cognitive radio network system comprises a master user and a cognitive user. In the time division duplex working mode, reciprocity exists between an uplink channel and a downlink channel, and a base station can estimate and precode the downlink channel according to a pilot frequency sequence of the uplink.

The method specifically comprises the following aspects:

(1) an initialization population is randomly generated. The group comprises a primary user and a secondary user, each communication link is provided with a pair of transceiving antennas, receiving antennas between the primary user and the secondary user are respectively counted as (PT, RT), and the channel quality between the PT and the RT obeys Rayleigh distribution. Then:

A. when the channel quality of the master user is lower than a certain threshold, the secondary user provides relay service for the master user, and reliable communication of a master user link is ensured;

B. as the reward of relay forwarding, when the channel quality of the primary user is higher than a threshold value, the primary user allows the secondary user to access the channel when a certain interference condition is met;

(2) evaluating the utility of the main user, namely calculating the objective function value of the main user:

A. assuming that the channel quality between PT and RT obeys Rayleigh distribution with parameter sigma, when the channel gain is lower than h^*The secondary user needs to provide relay service for the primary user, and the secondary user can share the frequency spectrum with the primary user;

B. in the cooperative relay stage 1, a master user sends data to a receiving end of the master user and a transmitting end of a secondary user;

C. in a cooperative relay stage 2, a secondary user provides relay service for a master user;

(3) in the cooperative spectrum sharing process, the secondary users consume energy to exchange spectrum resources so as to achieve the purpose of sending own data. And the secondary users transmit information at the maximum power allowed by the primary users in the spectrum sharing stage.

(4) Judging whether a termination condition is reached or an evolution algebra is maximized:

A. if so, terminating the evolution, and taking the best individual at the moment as an output solution;

B. if not, continuing the condition circulation;

(5) and carrying out mutation and cross operation, and processing the boundary conditions to obtain a temporary population.

(6) And evaluating the temporary population, and calculating the objective function value of each individual.

(7) And carrying out selection operation to obtain a new population.

(8) Evolution algebra and go to (3).

Drawings

FIG. 1 is a spectrum sharing system model of the present invention;

FIG. 2 is a flow chart of an optimization method of the present invention;

Detailed Description

The invention is further described with reference to the following figures and detailed description.

As shown in fig. 1, the spectrum sharing system model of the present invention includes 1 primary user and 1 secondary user communication links. In a frequency spectrum sharing model based on resource transaction, a secondary user provides relay service for a main user and obtains frequency spectrum resources released by the main user, and the main user obtains link reliable communication and saves transmitting power. Therefore, the frequency spectrum efficiency and the energy efficiency of the main user are effectively improved based on the resource transaction cooperative communication mechanism. Most of the existing cooperative spectrum sharing research focuses on sharing a spectrum by a primary user in an overlay mode, and the secondary user provides a relay service for the primary user and obtains a spectrum resource of a certain time slot. In its acquired slot, the primary user cannot use the band. In a coexisting sharing mode, the secondary user and the primary user can simultaneously use the authorized frequency band together as long as the interference of the secondary user to the primary user is lower than the interference limit condition tolerable by the primary user. Considering that the channel quality of the primary user has randomness in a time dimension, and when the channel quality of the primary user is not ideal, the secondary user provides relay service for the primary user; when the channel quality is good, the transmission requirement can be met under the condition of not adopting relay forwarding. Under certain interference constraint, the secondary users can share the frequency spectrum in an underlay mode, so that the special time slot reward for providing relay service for the secondary users is replaced, and more frequency spectrum resources can be saved. The method specifically comprises the following steps:

step (1), providing relay service for a primary user when the channel quality of the primary user is poor by the secondary user;

step (2), when the primary user channel is good, the secondary user can share the frequency spectrum resource with the primary user channel in an underlay manner, and the secondary user channel is modeled into a contract design problem by utilizing a contract theory;

step (3), establishing an optimized mathematical model for maximizing the utility of the main user by defining a utility function for evaluating the contract benefits;

step (4), solving by using a differential evolution algorithm;

and (5) obtaining a simulation result, and improving the energy efficiency and the spectrum efficiency of the main user.

As shown in fig. 2, the optimization method of the present invention specifically includes the following steps:

step (1), initializing working parameters of a primary user and a secondary user and an evolution algebra k being 0;

step (2), in the cognitive radio network, the transmitting end of the master user uses power P₀Sending data to a receiving end and a secondary user transmitting end for pairing;

step (3), the secondary user transmitting terminal decodes the data received in the step (2) and forwards the data to the primary user receiving terminal;

and (4) introducing a contract theory, and converting the problem that the primary user and the secondary user hope to obtain respective maximum utility from resource exchange into the optimal contract design problem of the primary user. The secondary user passively selects the optimal contract, so the optimal contract design problem becomes the problem of how the primary user designs the contract to obtain the maximum utility. The optimized mathematical model is as follows:

maxU_p(h^*,P)

wherein, U_pExpecting a utility function for the overall data transmission rate of the master user; h is^*Is a channel gain threshold; p is the rate of the primary user receiving end receiving the secondary user forwarding signal; u shape_sTransmission rate expectation R for transmitting self data by secondary user_sThe cost of consumption is subtracted as a utility function of the secondary user.

And (5) judging whether a termination condition is reached or the evolution algebra reaches the maximum. If so, terminating the evolution and taking the best individual at the moment as an output street; if not, continuing;

and (6) changing the evolution algebra k to k +1, and turning to the step (2).

It should be understood that this example is for illustrative purposes only and is not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.