CN110324844B - Secondary user strong excitation power distribution method based on cooperative NOMA and cooperative spectrum sharing - Google Patents

Secondary user strong excitation power distribution method based on cooperative NOMA and cooperative spectrum sharing Download PDF

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CN110324844B
CN110324844B CN201910609094.5A CN201910609094A CN110324844B CN 110324844 B CN110324844 B CN 110324844B CN 201910609094 A CN201910609094 A CN 201910609094A CN 110324844 B CN110324844 B CN 110324844B
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周晓天
文玉杰
张海霞
袁东风
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Shandong University
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    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W24/00—Supervisory, monitoring or testing arrangements
    • H04W24/02—Arrangements for optimising operational condition
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W40/00—Communication routing or communication path finding
    • H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
    • H04W40/22—Communication route or path selection, e.g. power-based or shortest path routing using selective relaying for reaching a BTS [Base Transceiver Station] or an access point
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/04—Wireless resource allocation
    • H04W72/044—Wireless resource allocation based on the type of the allocated resource
    • H04W72/0473—Wireless resource allocation based on the type of the allocated resource the resource being transmission power
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Abstract

The invention relates to a secondary user strong excitation power distribution method based on cooperative NOMA and cooperative spectrum sharing. The method not only can effectively improve the total rate of the primary user PU and the secondary user SU and improve the spectrum efficiency of the system, but also can simultaneously stimulate more secondary user SUs to serve as the forwarding relays of the primary user PU, and solve the problem of contradiction of user benefits between the primary user PU and the secondary user SU.

Description

Secondary user strong excitation power distribution method based on cooperative NOMA and cooperative spectrum sharing
Technical Field
The invention relates to a secondary user strong excitation power distribution method based on cooperative NOMA (non-orthogonal multiple access technology) and cooperative spectrum sharing, belonging to the technical field of communication systems.
Background
With the emergence of 5G, the number of mobile devices is increased sharply, and the demand of user access is increased exponentially, but now spectrum resources are in short supply, so the scarcity of spectrum resources and the demand of users for increasing speed are a pair of main contradictions in the policy design of communication systems at present.
Cooperative spectrum sharing technology is a promising approach to the problem of spectrum scarcity in wireless communications, and has attracted increasing research interest from the industry and academia. In the cooperative spectrum sharing system, a Secondary User (SU) having no spectrum access grant can obtain a certain spectrum access time by transmitting a signal of the Secondary User (SU) as a relay. Therefore, the frequency spectrum utilization rate of the whole communication system can be improved through cooperation between the PU and the SU.
In most existing work related to cooperative spectrum sharing techniques, Secondary Users (SUs) acting as relays during the cooperative phase are mostly operated in an orthogonal mode. That is, the Secondary User (SU) divides the allocated resources (time slot or frequency band resources) into two parts, one part for its own transmission and the other part dedicated to forwarding information from the Primary User (PU). As a result, a Secondary User (SU) cannot fully utilize a given spectrum or access time to meet his own needs.
To further improve the efficiency of spectrum sharing, non-orthogonal multiple access techniques (NOMA) were introduced. Non-orthogonal multiple access technology (NOMA) is considered one of the most attractive technologies for fifth generation mobile communications (5G), allowing users to share the same frequency spectrum or time slot at the same time. The basic idea of non-orthogonal multiple access (NOMA) is to use non-orthogonal transmission at the transmitting end, different users present different power differences at the receiving end, actively introduce interference information, and then utilize Successive Interference Cancellation (SIC) to achieve correct demodulation of different user information. And since successive interference cancellation is employed at the receiving end, NOMA is well suited for cooperative communication. Therefore, it is necessary to combine NOMA with cooperative spectrum sharing techniques in an appropriate way 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 of adopting the cooperation theory to make and solve the relay selection or power allocation problem in the downlink NOMA system is to maximize the sum rate and throughput or minimize the interruption probability of the whole system through a certain optimization strategy, and the fairness of resource allocation among users is not fully considered, and the unique user requirements of a Secondary User (SU) and a Primary User (PU) are not considered, so that the waste of communication resources is caused. Considering different requirements of users under different scenes, the method has great research significance when communication resources are scarce and the quantity of the users is rapidly increased.
There are some studies on cooperative NOMA and cooperative spectrum sharing today, and there are also a few studies that consider behavior between users in conjunction with the relevant game theory. The principle of the NOMA technology is to perform non-orthogonal multiplexing on related communication resources of different users, and demodulate by using the SIC at a receiving end, so that more users can share the current communication resources, the spectrum efficiency of the whole system is improved, and a certain user behavior contradiction problem inevitably exists in resource allocation due to introduction of multiple users. The secondary users as relays are usually selfish, and the secondary users want to satisfy their own forwarding rate requirements as much as possible while performing information forwarding work for the primary users. Therefore, the primary user needs to make an incentive system to make more secondary users actively participate in the forwarding work, and simultaneously, the benefit of the primary user is not lost. The research on the aspect of user behavior problems is also a key point of future research of NOMA.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a secondary user strong excitation power distribution method based on a cooperative NOMA and cooperative spectrum sharing environment;
the invention researches the performance of a multi-user relay communication system in a cooperative NOMA environment. The invention mainly researches the problems of power optimization and relay selection in the system. By utilizing the NOMA technology, the invention effectively improves the total rate of the PU and the SU, designs a strong excitation system to solve the benefit contradiction between the SU and the PU, and provides a power distribution algorithm to maximize the transmission rate of the SU used as the relay on the basis of ensuring the basic transmission rate requirement of the PU.
Given that Channel State Information (CSI) is known, compared to the conventional NOMA static power allocation strategy, the present invention optimizes the power allocation factor and forward power of the secondary user in consideration of the channel condition of downlink transmission. And a minimum rate requirement threshold of main user transmission is set to ensure that the performance of the PU as a frequency spectrum resource provider obtained by cooperation is better than that of a direct transmission condition. The rate of SU transmission as a relay is maximized by optimizing the power allocation factor for the secondary user NOMA transmission. The method can effectively improve the total rate of the PU and the SU and improve the spectrum efficiency of the system, and can simultaneously stimulate more SUs to be used as the forwarding relays of the PU, thereby solving the problem of the contradiction between the user benefits between the PU and the SU.
The technical scheme of the invention is as follows:
a secondary user strong excitation power distribution method based on cooperation NOMA and cooperation spectrum sharing is operated in a multi-user relay communication system based on cooperation NOMA, the multi-user relay communication system based on cooperation NOMA comprises a primary user system and a secondary user system, the primary user system refers to a primary user PU, the primary user PU comprises a primary transmitter PT and a primary receiver PR, the secondary user system comprises K secondary users SU, each secondary user SU comprises a transmitter and a receiver, and a transmitter-receiver pair is formed and is represented as STk-SRkThe master user PU is always in a communication state;
the primary user PU has access to bandwidth, but the channel conditions for direct transmission between the PT and PR are poor. On the other hand, each SU wants to get spectrum access time to transmit its own signal. But the primary user PU controls the allocation of access bandwidth. Therefore, the SU must assist the PU in forwarding in order to have an opportunity to send its own signal. To make better use of bandwidth resources, a cooperative transmission strategy is used, comprising two transmission phases: the direct transmission stage and the NOMA cooperative forwarding stage comprise the following steps:
(1) a direct transmission phase, which is carried out in the first half cycle of the cooperative communication period;
Figure BDA0002121758550000031
for ease of analysis, the present invention assumes that any one of the secondary users SU, ST, is selectedk-SRkAs a relay, the primary transmitter PT of the primary user PU broadcasts its data to the primary receiver PR and the transmitter ST of the secondary user SU selected as a relayk；
The primary receiver PR receives a signal yPT，PRAs shown in formula (I):
yPT，PR＝hPT，PRxP+ωPT，PR (Ⅰ)
in the formula (I), hPT，PRFor the channel gain, ω, between the primary transmitter PT and the primary receiver PRPT，PRIs white gaussian noise, x, between the primary transmitter PT and the primary receiver PRPIs a signal of a master user PU;
the direct transmission rate achieved by the primary receiver PR is:
Figure BDA0002121758550000032
SNRPT，PRindicating the signal-to-noise ratio of the signal sent from the primary transmitter PT to the primary receiver PR, resulting in a very small direct transmission rate R due to very poor channel conditions from the primary transmitter PT to the primary receiver PRdTherefore, SU must be selected as a relay for the PU's transmission. The invention considers the direct transmission rate R achieved by the primary receiver PRdNeglect;
transmitter ST of a secondary user SUkReceiving a signal
Figure BDA0002121758550000033
As shown in formula (II):
Figure BDA0002121758550000034
in the formula (II), the compound is shown in the specification,
Figure BDA0002121758550000035
for main transmitters PT and STkWhite gaussian noise in between, and the white gaussian noise,
Figure BDA0002121758550000036
for main transmitters PT and STkA channel gain in between;
(2) the NOMA cooperation forwarding stage is carried out in the second half period of the cooperation communication time interval;
for the secondary users SU, the invention assumes that each secondary user SU successfully decodes the signal received from the primary user PU in the first phase; therefore, the present invention is more focused onA relay process between the secondary user transmitter ST and the primary user receiver PR, secondary user receiver STk. Transmitter ST of a secondary user SUkA transmitter ST for a secondary user SU for decoding the signal received in the direct transmission phase and for superimposing it on the signal itself to generate a non-orthogonal signalkUsing NOMA transmission scheme, sharing frequency band and time resource, and forwarding power to optimal secondary user SU according to channel gain conditions of primary user PU and secondary user SU
Figure BDA0002121758550000037
Allocating different power allocation factors to primary user PU and secondary user SU
Figure BDA0002121758550000038
To distinguish signals of different users, i.e. to be
Figure BDA0002121758550000039
To a secondary user SU, will
Figure BDA0002121758550000041
Allocating to a master user PU; simultaneously forwarding non-orthogonal signals generated by superposition to receiver PR of primary user PU and receiver SR of secondary user SUkAnd at the receiver SR of the secondary user SUkAnd demodulating by a Serial Interference Cancellation (SIC) method at a receiver PR of the primary user PU, wherein the demodulation comprises the following steps: firstly, the information of the secondary user SU is taken as interference, the information of the primary user PU is decoded, and then the information of the secondary user SU is decoded; in the invention, a primary user PU and a secondary user SU share an authorized spectrum and formulate a power distribution factor to reward the forwarding of the SU in the demodulation process; thereby resolving the conflict of interests between the two.
The goal of the proposed cooperative NOMA system is to maximize the utility value of the selected SU while satisfying the basic transmission rate condition of the PU. The invention provides an optimization algorithm for jointly optimizing transmission power and power division factors. The objective function and the limiting conditions C1-C3 which satisfy the basic transmission rate condition of the primary user PU and simultaneously maximize the utility value of the selected secondary user SU are as shown in formula (III):
Figure BDA0002121758550000042
in the formula (III), USURefers to the utility value of the secondary user SU,
Figure BDA0002121758550000043
receiver SR at k-th secondary userkResulting transmission rate, α1kRefers to the power allocation factor, alpha, of the primary user PU2kRefers to the power allocation factor, λ, of the secondary user SUkRefers to the unit power consumption cost, P, of the secondary user SUkFor the forward power, P, of the secondary users SU in the transmissionMAXRefers to the power limit of the secondary user forwarding power; u shapePUMeans the utility value, R, of the primary user PUVThe method comprises the steps that a primary user PU obtains a required rate through NOMA cooperative transmission in an NOMA cooperative forwarding stage;
c1 shows that the utility value obtained by the main user PU in the multi-user relay communication system based on the cooperative NOMA is larger than the transmission rate R required by the main user PUV(ii) a C2 indicates that the power allocation factor is reasonable and that the power allocation factor of the primary user PU is always larger than that of the secondary user SU; c3 indicates that the forwarding power of the secondary user SU does not exceed PMAX；
Calculating the optimal SU forwarding power of the secondary user according to formula (III)
Figure BDA0002121758550000044
Optimal power allocation factor for primary user PU
Figure BDA0002121758550000045
And power allocation factor of secondary user SU
Figure BDA0002121758550000046
Respectively shown in formulas (IV), (V) and (VI):
Figure BDA0002121758550000051
Figure BDA0002121758550000052
Figure BDA0002121758550000053
in the formulas (IV), (V) and (VI), gamma refers to the transmission signal-to-interference-noise ratio required by the main user PU,
Figure BDA0002121758550000054
transmitter ST representing a secondary user SUkAnd the ratio of the channel gain and the noise power between the primary receivers PR of the primary users PU,
Figure BDA0002121758550000055
transmitter ST representing a secondary user SUkReceiver SR for secondary user SUkThe ratio of channel gain and noise power.
The invention solves the problem of selecting any SU as the best SU forwarding power when relaying
Figure BDA0002121758550000056
Optimal power allocation factor for primary user PU
Figure BDA0002121758550000057
And power allocation factor of secondary user SU
Figure BDA0002121758550000058
Can obtain each as a preparationAnd selecting the optimal resource allocation scheme of the system when the relay SU performs cooperative transmission.
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 act as alternative relays, indicating that it needs to seek a relay for cooperative NOMA transmission, and a power allocation factor scheme is given according to equations (v), (vi)
Figure BDA0002121758550000059
2. If the kth secondary user SU wants to perform cooperative transmission, the optimal secondary user SU forward power is calculated according to equation (IV)
Figure BDA00021217585500000510
And reporting the PU.
3. The PU of the master user receives the best SU forwarding power of the secondary users reported by all the k SU of the secondary users
Figure BDA00021217585500000511
The secondary user SU that maximizes the cooperative NOMA based multi-user relay communication system and rate is selected as the relay.
According to the invention, preferably, the inference process of the objective function in the NOMA cooperative forwarding stage is as follows:
successive Interference Cancellation (SIC) is applied to the primary receiver PR and the receiver SR for decoding non-orthogonal NOMA signals, and for the primary user PU, the information transmission rate obtained at the primary receiver PR is as shown in equation (vii):
Figure BDA00021217585500000512
in the formula (VII), the reaction mixture is,
Figure BDA0002121758550000061
σ2in order to be able to measure the power of the noise,
Figure BDA0002121758550000062
for the slave transmitter STkChannel gain, alpha, to the primary receiver PR1kIs the power allocation factor, alpha, of the primary user PU2kIs the power allocation factor of the secondary user SU; pkThe forward power of the secondary user SU in the transmission;
for the primary user PU, the present invention considers the direct transmission rate R due to the poor channel condition between PT and PRdNeglecting, setting the rate R required by the PU of the primary user through the NOMA cooperative transmission in the NOMA cooperative forwarding stageVDefinition of
Figure BDA0002121758550000063
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 as formula (VIII):
Figure BDA0002121758550000064
it can be seen that the PU will seek to relay transmissions only when the direct transmission rate is small.
For secondary users SU, at the receiver SRkThe obtained information transmission rate is shown as formula (IX):
Figure BDA0002121758550000065
in the formula (IX),
Figure BDA0002121758550000066
σ2is the power of the noise or noise,
Figure BDA0002121758550000067
for the slave transmitter STkTo the receiver SRkThe channel gain of (a);
thus, the utility function of the secondary user SU is shown in formula (x):
Figure BDA0002121758550000068
in the formula (X), λkIs the unit power cost of the SU;
since the SU is selfish and rational, there is no obligation to waste power resources to help the PU forward information. In the proposed system, the invention maximizes the utility value of the secondary user SU in order to excite the SU, whereas for the primary user PU, it is only necessary to satisfy the PU's transmission rate to reach the requirement RVAnd R isVAlways greater than the direct transmission rate Rd；
The objective 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 objective function, constraint C1-C3 is shown as equation (III):
Figure BDA0002121758550000071
optimized SU forward power according to the invention
Figure BDA0002121758550000072
Optimal power allocation factor for primary user PU
Figure BDA0002121758550000073
And power allocation factor of secondary user SU
Figure BDA0002121758550000074
The reasoning process of the formulae (IV), (V), (VI) is as follows:
substituting restriction condition C2 into UPUAnd USUObtaining the formula (XI) or (XII):
Figure BDA0002121758550000075
Figure BDA0002121758550000076
the utility function of the secondary users SU is with respect to α2kIncrementally, obtained according to formula (XI)
Figure BDA0002121758550000077
Therefore, the secondary users SU are only present
Figure BDA0002121758550000078
Then there is a maximum utility value, at which time the yield of PU equals RV；
Although the yield of PU is equal to R at this timeVHowever, the PU still obtains a higher transmission rate than the direct transmission. The PU can still gain from cooperative transmission. The invention can simplify the optimization problem formula (III) and obtain the formula (XIII):
Figure BDA0002121758550000079
s.t.Pk≤PMAx
optimal SU forward power
Figure BDA00021217585500000713
The maximum utility of the secondary user SU is shown in formula (xiv):
Figure BDA00021217585500000710
solving the first and second reciprocal of formula (XIV), respectively as shown in formulas (XV) (XVI):
Figure BDA00021217585500000711
Figure BDA00021217585500000712
formula (xvi) is constantly negative, leading to the conclusion that: the maximum utility value is obtained when formula (XV) is zero, and thus the optimum SU forward power is calculated
Figure BDA0002121758550000081
Optimal power allocation factor for primary user PU
Figure BDA0002121758550000082
And power allocation factor of secondary user SU
Figure BDA0002121758550000083
As shown in formulas (IV), (V) and (VI):
Figure BDA0002121758550000084
Figure BDA0002121758550000085
Figure BDA0002121758550000086
preferably according to the invention, in order to maximize the throughput of the whole system, the secondary user SU is selected that maximizes the sum rateselectAs a relay, the purpose of improving the overall system performance can be achieved, as shown in formula (xvii):
Figure BDA0002121758550000087
in formula (xvii), K ═ 1, 2, K represents the K secondary relays that are candidates for relayingA set of users is provided with a user profile,
Figure BDA0002121758550000088
refers to the utility value obtained by the primary user PU when the kth secondary user is selected as the relay,
Figure BDA0002121758550000089
which means the utility value obtained by the secondary user SU when the kth secondary user is selected as the relay.
The invention has the beneficial effects that:
1. according to the power optimization relay selection method in the cooperative NOMA cooperative spectrum sharing system, the transmission rate of the cooperative NOMA system is analyzed, the properties of a logarithmic function are utilized, a corresponding utility function and an optimization problem are constructed, the optimized problem is researched, an optimal solution is obtained through a low-complexity solving algorithm, and the goal of maximizing the sum rate of the system is finally achieved.
2. The invention considers the fairness and the compatibility of resource allocation among users, fully considers the unique user requirements of a Secondary User (SU) and a Primary User (PU), and gives enough excitation to the SU to make the SU actively strive for the right of serving as a relay, so that the design of a communication system is more reasonable.
Drawings
FIG. 1 is a schematic representation of a cooperative NOMA based multi-user relay communication system model of the present invention;
FIG. 2 is a diagram illustrating simulation results of variation of ideal power allocation factors with SINR required by a primary user PU;
FIG. 3 is a diagram of simulation results of ideal SU relay power variation with the SINR required by a primary user PU;
FIG. 4 is a diagram illustrating a comparison of total utility values and a random strategy.
Detailed Description
The invention is further defined in the following, but not limited to, the figures and examples in the description.
Example 1
Secondary user strong incentive based on cooperative NOMA and cooperative spectrum sharingA power allocation method for operating in a cooperative NOMA based multi-user relay communication system, as shown in FIG. 1, the cooperative NOMA based multi-user relay communication system comprises a primary user system and a secondary user system, the primary user system is a primary user PU, the primary user PU comprises a primary transmitter PT and a primary receiver PR, the secondary user system comprises K secondary users SU, each secondary user SU comprises a transmitter and a receiver, forming a transmitter-receiver pair, denoted STk-SRkThe master user PU is always in a communication state;
the primary user PU has access to bandwidth, but the channel conditions for direct transmission between the PT and PR are poor. On the other hand, each SU wants to get spectrum access time to transmit its own signal. But the primary user PU controls the allocation of access bandwidth. Therefore, the SU must assist the PU in forwarding in order to have an opportunity to send its own signal. To make better use of bandwidth resources, a cooperative transmission strategy is used, comprising two transmission phases: the direct transmission stage and the NOMA cooperative forwarding stage comprise the following steps:
(1) a direct transmission phase, which is carried out in the first half cycle of the cooperative communication period;
Figure BDA0002121758550000091
for ease of analysis, the present invention assumes that any one of the secondary users SU, ST, is selectedk-SRkAs a relay, the primary transmitter PT of the primary user PU broadcasts its data to the primary receiver PR and the transmitter ST of the secondary user SU selected as a relayk；
The primary receiver PR receives a signal yPT，PRAs shown in formula (I):
yPT，PR＝hPT，PRxP+ωPT，PR (Ⅰ)
in the formula (I), hPT，PRFor the channel gain, ω, between the primary transmitter PT and the primary receiver PRPT，PRIs white gaussian noise, x, between the primary transmitter PT and the primary receiver PRPIs a signal of a master user PU;
the direct transmission rate achieved by the primary receiver PR is:
Figure BDA0002121758550000092
SNRPT，PRindicating the signal-to-noise ratio of the signal sent from the primary transmitter PT to the primary receiver PR, resulting in a very small direct transmission rate R due to very poor channel conditions from the primary transmitter PT to the primary receiver PRdTherefore, SU must be selected as a relay for the PU's transmission. The invention considers the direct transmission rate R achieved by the primary receiver PRdNeglect;
transmitter ST of a secondary user SUkReceiving a signal
Figure BDA0002121758550000093
As shown in formula (II):
Figure BDA0002121758550000101
in the formula (II), the compound is shown in the specification,
Figure BDA0002121758550000102
for main transmitters PT and STkWhite gaussian noise in between, and the white gaussian noise,
Figure BDA0002121758550000103
for main transmitters PT and STkA channel gain in between;
(2) the NOMA cooperation forwarding stage is carried out in the second half period of the cooperation communication time interval;
for the secondary users SU, the invention assumes that each secondary user SU successfully decodes the signal received from the primary user PU in the first phase; the invention therefore focuses more on the relay process between the secondary user sender ST and the primary user receiver PR, the secondary user receiver STk. Transmitter ST of a secondary user SUkDecoding the signal received in the direct transmission phase and superimposing it with the own signalTransmitter ST for secondary users SU, which are non-orthogonal signalskUsing NOMA transmission scheme, sharing frequency band and time resource, and forwarding power to optimal secondary user SU according to channel gain conditions of primary user PU and secondary user SU
Figure BDA0002121758550000104
Allocating different power allocation factors to secondary user SU and primary user PU
Figure BDA0002121758550000105
To distinguish signals of different users, i.e. to be
Figure BDA0002121758550000106
To a secondary user SU, will
Figure BDA0002121758550000107
Allocating to a master user PU; simultaneously forwarding non-orthogonal signals generated by superposition to receiver PR of primary user PU and receiver SR of secondary user SUkAnd at the receiver SR of the secondary user SUkAnd demodulating by a Serial Interference Cancellation (SIC) method at a receiver PR of the primary user PU, wherein the demodulation comprises the following steps: firstly, the information of the secondary user SU is taken as interference, the information of the primary user PU is decoded, and then the information of the secondary user SU is decoded; in the invention, a primary user PU and a secondary user SU share an authorized spectrum and formulate a power distribution factor to reward the forwarding of the SU in the demodulation process; thereby resolving the conflict of interests between the two.
The goal of the proposed cooperative NOMA system is to maximize the utility value of the selected SU while satisfying the basic transmission rate condition of the PU. The invention provides an optimization algorithm for jointly optimizing transmission power and power division factors. The objective function and the limiting conditions C1-C3 which satisfy the basic transmission rate condition of the primary user PU and simultaneously maximize the utility value of the selected secondary user SU are as shown in formula (III):
Figure BDA0002121758550000108
in the formula (III), USURefers to the utility value of the secondary user SU,
Figure BDA0002121758550000109
receiver SR at k-th secondary userkResulting transmission rate, α1kRefers to the power allocation factor, alpha, of the primary user PU2kRefers to the power allocation factor, λ, of the secondary user SUkRefers to the unit power consumption cost, P, of the secondary user SUkFor the forward power, P, of the secondary users SU in the transmissionMAXRefers to the power limit of the secondary user forwarding power; u shapePUMeans the utility value, R, of the primary user PUVThe method comprises the steps that a primary user PU obtains a required rate through NOMA cooperative transmission in an NOMA cooperative forwarding stage;
c1 shows that the utility value obtained by the main user PU in the multi-user relay communication system based on the cooperative NOMA is larger than the transmission rate R required by the main user PUV(ii) a C2 indicates that the power allocation factor is reasonable and that the power allocation factor of the primary user PU is always larger than that of the secondary user SU; c3 indicates that the forwarding power of the secondary user SU does not exceed PMAX；
Calculating the optimal SU forwarding power of the secondary user according to formula (III)
Figure BDA0002121758550000111
Optimal power allocation factor for primary user PU
Figure BDA0002121758550000112
And power allocation factor of secondary user SU
Figure BDA0002121758550000113
Respectively shown in formulas (IV), (V) and (VI):
Figure BDA0002121758550000114
Figure BDA0002121758550000115
Figure BDA0002121758550000116
in the formulas (IV), (V) and (VI), gamma refers to the transmission signal-to-interference-noise ratio required by the main user PU,
Figure BDA0002121758550000117
transmitter ST representing a secondary user SUkAnd the ratio of the channel gain and the noise power between the primary receivers PR of the primary users PU,
Figure BDA0002121758550000118
transmitter ST representing a secondary user SUkReceiver SR for secondary user SUkThe ratio of channel gain and noise power.
The invention solves the problem of selecting any SU as the best SU forwarding power when relaying
Figure BDA0002121758550000119
Optimal power allocation factor for primary user PU
Figure BDA00021217585500001110
And power allocation factor of secondary user SU
Figure BDA00021217585500001111
The optimal resource allocation scheme of the system when each SU as an alternative relay performs cooperative transmission can be obtained.
The specific process is as follows:
1. assuming the channel conditions are known, the primary user PU broadcasts to all available usersSending a cooperative forwarding request for the secondary users SU of the alternative relay indicating that they need to seek a relay for cooperative NOMA transmission, and providing a power allocation factor scheme according to equations (V), (VI)
Figure BDA00021217585500001112
2. If the kth secondary user SU wants to perform cooperative transmission, the optimal secondary user SU forward power is calculated according to equation (IV)
Figure BDA0002121758550000121
And reporting the PU.
3. The PU of the master user receives the best SU forwarding power of the secondary users reported by all the k SU of the secondary users
Figure BDA0002121758550000122
The secondary user SU that maximizes the cooperative NOMA based multi-user relay communication system and rate is selected as the relay.
In the NOMA cooperative forwarding phase, the reasoning process of the objective function is as follows:
successive Interference Cancellation (SIC) is applied to the primary receiver PR and the receiver SR for decoding non-orthogonal NOMA signals, and for the primary user PU, the information transmission rate obtained at the primary receiver PR is as shown in equation (vii):
Figure BDA0002121758550000123
in the formula (VII), the reaction mixture is,
Figure BDA0002121758550000124
σ2in order to be able to measure the power of the noise,
Figure BDA0002121758550000125
for the slave transmitter STkChannel gain, alpha, to the primary receiver PR1kIs the power allocation factor, alpha, of the primary user PU2kIs the power allocation factor of the secondary user SU; pkThe forward power of the secondary user SU in the transmission;
for the primary user PU, the present invention considers the direct transmission rate R due to the poor channel condition between PT and PRdNeglecting, setting the rate R required by the PU of the primary user through the NOMA cooperative transmission in the NOMA cooperative forwarding stageVDefinition of
Figure BDA0002121758550000126
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 as formula (VIII):
Figure BDA0002121758550000127
it can be seen that the PU will seek to relay transmissions only when the direct transmission rate is small.
For secondary users SU, at the receiver SRkThe obtained information transmission rate is shown as formula (IX):
Figure BDA0002121758550000128
in the formula (IX),
Figure BDA0002121758550000129
σ2is the power of the noise or noise,
Figure BDA00021217585500001210
for the slave transmitter STkTo the receiver SRkThe channel gain of (a);
thus, the utility function of the secondary user SU is shown in formula (x):
Figure BDA0002121758550000131
in the formula (X), λkIs a unit of SUA power consumption cost;
since the SU is selfish and rational, there is no obligation to waste power resources to help the PU forward information. In the proposed system, the invention maximizes the utility value of the secondary user SU in order to excite the SU, whereas for the primary user PU, it is only necessary to satisfy the PU's transmission rate to reach the requirement RVAnd R isVAlways greater than the direct transmission rate Rd；
The objective 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 objective function, constraint C1-C3 is shown as equation (III):
Figure BDA0002121758550000132
optimal SU forward power
Figure BDA0002121758550000133
Optimal power allocation factor for primary user PU
Figure BDA0002121758550000134
And power allocation factor of secondary user SU
Figure BDA0002121758550000135
The reasoning process of the formulae (IV), (V), (VI) is as follows:
substituting restriction condition C2 into UPUAnd USEObtaining the formula (XI) or (XII):
Figure BDA0002121758550000136
Figure BDA0002121758550000137
for secondary useThe utility function of the user SU is with respect to alpha2kIncrementally, obtained according to formula (XI)
Figure BDA0002121758550000138
Therefore, the secondary users SU are only present
Figure BDA0002121758550000139
Then there is a maximum utility value, at which time the yield of PU equals RV；
Although the yield of PU is equal to R at this timeVHowever, the PU still obtains a higher transmission rate than the direct transmission. The PU can still gain from cooperative transmission. The invention can simplify the optimization problem formula (III) and obtain the formula (XIII):
Figure BDA00021217585500001310
s.t.Pk≤PMAX
optimal SU forward power
Figure BDA0002121758550000141
The maximum utility of the secondary user SU is shown in formula (xiv):
Figure BDA0002121758550000142
solving the first and second reciprocal of formula (XIV), respectively as shown in formulas (XV) (XVI):
Figure BDA0002121758550000143
Figure BDA0002121758550000144
formula (xvi) is constantly negative, leading to the conclusion that: when formula (XV) is zeroTo the maximum utility value, and thus, calculating the optimal SU forwarding power
Figure BDA0002121758550000145
Optimal power allocation factor for primary user PU
Figure BDA0002121758550000146
And power allocation factor of secondary user SU
Figure BDA0002121758550000147
As shown in formulas (IV), (V) and (VI):
Figure BDA0002121758550000148
Figure BDA0002121758550000149
Figure BDA00021217585500001410
the performance of a system based on cooperative NOMA and cooperative spectrum sharing proposed by the present embodiment is shown in fig. 2, 3 and 4. By comparison with random relay selection, take 5 SU relays as an example. FIG. 2 shows the ideal power division factor of the system
Figure BDA00021217585500001411
SINR as required by PU varies. It can be observed that a PU with a high required rate will achieve a greater power division factor
Figure BDA00021217585500001412
And assigns a smaller factor to SU
Figure BDA00021217585500001413
In FIG. 3, the invention illustrates the SIN of the desired PUContributing relay power of R and SU
Figure BDA00021217585500001414
The relationship between them. The higher the transmission required by the PU itself, the power consumed by SU forwarding
Figure BDA00021217585500001415
The less. Even if the PU allocates a greater power allocation factor when a greater rate is required, the SU will decrease the rate by decreasing the rate
Figure BDA00021217585500001416
To reduce its own losses, which also reflects the selfishness of the SU. This also represents a contradiction in the interests between the PU and SU, finding the most favorable points for both in the two mutual games. 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 values of PU and SU are always higher than the random scheme. This demonstrates that the scheme of the present invention can be used to solve the optimal power allocation factor
Figure BDA00021217585500001417
And SU forward power
Figure BDA00021217585500001418
To achieve better performance of the overall system.
Example 2
The strong excitation power allocation method for the secondary users based on cooperative NOMA and cooperative spectrum sharing in embodiment 1 is characterized by comprising the following steps: to maximize the throughput of the overall system, the secondary user SU that maximizes the sum rate is selectedselectAs a relay, the purpose of improving the overall system performance can be achieved, as shown in formula (xvii):
Figure BDA0002121758550000151
in formula (xvii), K ═ {1, 2., K } represents the set of K secondary users that are candidates for relaying，
Figure BDA0002121758550000152
Refers to the utility value obtained by the primary user PU when the kth secondary user is selected as the relay,
Figure BDA0002121758550000153
which means the utility value obtained by the secondary user SU when the kth secondary user is selected as the relay.

Claims (4)

1. A secondary user strong excitation power distribution method based on cooperation NOMA and cooperation spectrum sharing is operated in a multi-user relay communication system based on cooperation NOMA, the multi-user relay communication system based on cooperation NOMA comprises a primary user system and a secondary user system, the primary user system refers to a primary user PU, the primary user PU comprises a primary transmitter PT and a primary receiver PR, the secondary user system comprises K secondary users SU, each secondary user SU comprises a transmitter and a receiver, and a transmitter-receiver pair is formed and is represented as STk-SRkThe master user PU is always in a communication state; it is characterized by comprising two transmission stages: the direct transmission stage and the NOMA cooperative forwarding stage comprise the following steps:
(1) a direct transmission phase, which is carried out in the first half cycle of the cooperative communication period;
selecting any one of the secondary users SU, STk-SRkAs a relay, the primary transmitter PT of the primary user PU broadcasts its data to the primary receiver PR and the transmitter ST of the secondary user SU selected as a relayk；
The primary receiver PR receives a signal yPT，PRAs shown in formula (I):
yPT，PR＝hPT，PRxP+ωPT，PR(I)
in the formula (I), hPT，PRFor the channel gain, ω, between the primary transmitter PT and the primary receiver PRPT，PRIs white gaussian noise, x, between the primary transmitter PT and the primary receiver PRPIs a signal of a master user PU;
direct transmission rate R achieved by the primary receiver PRdNeglect;
transmitter ST of a secondary user SUkReceiving a signal
Figure FDA0002121758540000011
As shown in formula (II):
Figure FDA0002121758540000012
in the formula (II), the compound is shown in the specification,
Figure FDA0002121758540000013
for main transmitters PT and STkWhite gaussian noise in between, and the white gaussian noise,
Figure FDA0002121758540000014
for main transmitters PT and STkA channel gain in between;
(2) the NOMA cooperation forwarding stage is carried out in the second half period of the cooperation communication time interval;
assuming that each secondary user SU successfully decodes the signal received from the primary user PU in the first phase; transmitter ST of a secondary user SUkA transmitter ST for a secondary user SU for decoding the signal received in the direct transmission phase and for superimposing it on the signal itself to generate a non-orthogonal signalkUsing NOMA transmission scheme, sharing frequency band and time resource, and forwarding power to optimal secondary user SU according to channel gain conditions of primary user PU and secondary user SU
Figure FDA0002121758540000015
Allocating different power allocation factors to the primary user PU and the secondary user SU
Figure FDA0002121758540000016
To distinguish the signals of the different users from each other,that is to say, the
Figure FDA0002121758540000017
To a secondary user SU, will
Figure FDA0002121758540000018
Allocating to a master user PU; simultaneously forwarding non-orthogonal signals generated by superposition to receiver PR of primary user PU and receiver SR of secondary user SUkAnd at the receiver SR of the secondary user SUkAnd demodulating by a serial interference elimination method at a receiver PR of the main user PU, wherein the demodulation comprises the following steps: firstly, the information of the secondary user SU is taken as interference, the information of the primary user PU is decoded, and then the information of the secondary user SU is decoded; in the demodulation process, a primary user PU rewards the forwarding of SU by sharing a licensed spectrum with a secondary user SU and formulating a power allocation factor;
the objective function and the limiting conditions C1-C3 that maximize the utility value of the selected secondary users SU while satisfying the basic transmission rate condition of the primary user PU are shown in equation (III):
Figure FDA0002121758540000021
in the formula (III), USURefers to the utility value of the secondary user SU,
Figure FDA0002121758540000022
receiver SR at k-th secondary userkResulting transmission rate, α1kRefers to the power allocation factor, alpha, of the primary user PU2kRefers to the power allocation factor, λ, of the secondary user SUkRefers to the unit power consumption cost, P, of the secondary user SUkFor the forward power, P, of the secondary users SU in the transmissionMAXRefers to the power limit of the secondary user forwarding power; u shapePUMeans the utility value, R, of the primary user PUVThe method comprises the steps that a primary user PU obtains a required rate through NOMA cooperative transmission in an NOMA cooperative forwarding stage;
c1 shows that the utility value obtained by the main user PU in the multi-user relay communication system based on the cooperative NOMA is larger than the transmission rate R required by the main user PUV(ii) a C2 indicates that the power allocation factor is reasonable and that the power allocation factor of the primary user PU is always larger than that of the secondary user SU; c3 indicates that the forwarding power of the secondary user SU does not exceed PMAX；
Calculating the optimal SU forwarding power of the secondary user by formula (III)
Figure FDA0002121758540000023
Optimal power allocation factor for primary user PU
Figure FDA0002121758540000024
And power allocation factor of secondary user SU
Figure FDA0002121758540000025
Respectively shown in formulas (IV), (V) and (VI):
Figure FDA0002121758540000026
Figure FDA0002121758540000027
Figure FDA0002121758540000028
in the formulas (IV), (V) and (VI), gamma refers to the transmission signal-to-interference-noise ratio required by the PU of the main user,
Figure FDA0002121758540000031
transmitter ST representing a secondary user SUkAnd the ratio of the channel gain and the noise power between the primary receivers PR of the primary users PU,
Figure FDA0002121758540000032
transmitter ST representing a secondary user SUkReceiver SR for secondary user SUkThe ratio of channel gain and noise power.
2. The method of claim 1, wherein the secondary users SU with the highest sum rate are selected to use strong excitation power allocation for secondary users sharing cooperative spectrum based on cooperative NOMAselectAs a relay, as shown in formula (xvii):
Figure FDA0002121758540000033
in the formula (XVII), the compound (VII),
Figure FDA0002121758540000034
representing a set of K secondary users that are alternatives to a relay,
Figure FDA0002121758540000035
refers to the utility value obtained by the primary user PU when the kth secondary user is selected as the relay,
Figure FDA0002121758540000036
which means the utility value obtained by the secondary user SU when the kth secondary user is selected as the relay.
3. The method for allocating strong excitation power to secondary users based on cooperative NOMA and cooperative spectrum sharing of claim 1, wherein in the NOMA cooperative forwarding stage, the information transmission rate obtained at the primary receiver PR is as shown in formula (vii):
Figure FDA0002121758540000037
in the formula (VII), the reaction mixture is,
Figure FDA0002121758540000038
σ2in order to be able to measure the power of the noise,
Figure FDA0002121758540000039
for the slave transmitter STkChannel gain, alpha, to the primary receiver PR1kIs the power allocation factor, alpha, of the primary user PU2kIs the power allocation factor of the secondary user SU; pkThe forward power of the secondary user SU in the transmission;
for the master user PU, direct transmission rate RdNeglecting, setting the rate R required by the PU of the primary user through the NOMA cooperative transmission in the NOMA cooperative forwarding stageVDefinition of
Figure FDA00021217585400000310
Gamma is the required SINR of the primary user PU;
the utility function of the primary user PU is shown as formula (VIII):
Figure FDA00021217585400000311
for secondary users SU, at the receiver SRkThe obtained information transmission rate is as shown in formula (IX):
Figure FDA0002121758540000041
in the formula (IX), the compound (I),
Figure FDA0002121758540000042
σ2is the power of the noise or noise,
Figure FDA0002121758540000043
for the slave transmitter STkTo the receiver SRkThe channel gain of (a);
the utility function of the secondary user SU is shown as equation (X):
Figure FDA0002121758540000044
in the formula (X), λkIs the unit power cost of the SU;
the utility value of the secondary user SU is maximized, and for the primary user PU, the transmission rate of the PU only needs to be met to reach the requirement RVAnd R isVAlways greater than the direct transmission rate Rd；
The utility value of the selected secondary user SU is maximized while the basic transmission rate condition of the primary user PU is met, and an objective function and a limiting condition C1-C3 are shown as formula (III):
Figure FDA0002121758540000045
4. method for strong excitation power allocation to secondary users based on cooperative NOMA and cooperative spectrum sharing according to any of claims 1-3, characterized in that the constraint C2 is substituted into UPUAnd USUTo obtain the formula (XI) and the formula (XII):
Figure FDA0002121758540000046
Figure FDA0002121758540000047
the utility function of the secondary users SU is with respect to α2kIncrementally, obtained according to formula (XI)
Figure FDA0002121758540000048
Therefore, the secondary users SU are only present
Figure FDA0002121758540000049
Then there is a maximum utility value, at which time the yield of PU equals RV；
Simplifying the optimization problem formula (III) to obtain formula (XIII):
Figure FDA0002121758540000051
optimal SU forward power
Figure FDA0002121758540000052
The maximum utility of the secondary user SU is shown in formula (xiv):
Figure FDA0002121758540000053
solving the first and second reciprocal of formula (XIV), respectively as shown in formulas (XV) (XVI):
Figure FDA0002121758540000054
Figure FDA0002121758540000055
formula (xvi) is constantly negative, leading to the conclusion that: the maximum utility value is obtained when formula (XV) is zero, and thus the optimum SU forward power is calculated
Figure FDA0002121758540000056
Optimal power allocation factor for primary user PU
Figure FDA0002121758540000057
And power allocation factor of secondary user SU
Figure FDA0002121758540000058
As shown in formulas (IV), (V) and (VI):
Figure FDA0002121758540000059
Figure FDA00021217585400000510
Figure FDA00021217585400000511
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