CN106656297A - Cognitive orthogonal cooperative transmission method in the presence of primary user interference - Google Patents

Abstract

The invention discloses a cognitive orthogonal cooperative transmission method when primary user interference exists, and mainly solves the problem of low transmission reliability in the prior art when primary user interference exists. The implementation steps are: 1) the source node of the secondary user broadcasts the pilot signal; 2) the destination node of the secondary user decodes the received signal, and checks the decoded signal: if the verification is successful, the data is sent; otherwise, the relay node decodes If the decoding fails, the relay node will no longer forward the information; otherwise, the relay node will send a pilot signal, and the destination node will reply with a response signal; 3) The relay node will The interference-to-noise ratio selects the best relay decoding, and forwards the orthogonal copy of the source node information to the destination node; 4) The destination node combines the signals of two time slots to complete the cognitive orthogonal cooperative transmission. The invention can save transmission power while meeting communication quality requirements, and can be used in a cooperative relay system.

Description

Cognitive Orthogonal Cooperative Transmission Method in the Existence of Primary User Interference

technical field

The invention belongs to the technical field of communication, relates to cooperative relay technology, and further relates to a cognitive orthogonal cooperative transmission, which can be used for cognitive radio communication when there is interference to a primary user.

Background technique

The rapid development of wireless communication and the emergence of a large number of new wireless applications provide people with increasingly rich and convenient services for their work and life. However, with the rapid growth of mobile communication systems and wireless devices, available spectrum becomes increasingly tight, which cannot meet people's increasingly complex wireless application requirements. At the same time, according to the statistical results of the FCC of the US Federal Communications Commission, most of the authorized spectrum is often idle in different regions or time periods, resulting in an actual average utilization rate of spectrum resources of only about 30%. In order to alleviate the contradiction between the ever-increasing demand for wireless communication and the shortage of spectrum resources, cognitive radio CR technology came into being. In actual cognitive radio communication, due to factors such as power limitation, multipath fading, shadow shading, and interference noise, the existing "point-to-point" communication performance deteriorates, which reduces the single-point signal transmission and reception in the cognitive network. reliability.

Compared with the direct transmission system, the system in which the relay node assists the source node in transmission can obtain capacity gain. The most typical cooperative relay transmission is a three-node single-relay two-hop cooperative relay transmission including the source node, the relay node and the destination node. . In single-relay cooperative transmission, different transmission nodes share each other's antennas to form a virtual multiple-input multiple-output MIMO antenna array, so that single-antenna nodes can also obtain space diversity gain to achieve resistance to wireless communication channel fading Effect. Compared with MIMO technology, cooperative relay transmission technology does not need to equip multiple antennas on wireless terminals, which provides a feasible way to increase channel capacity for handheld terminals and sensor nodes that are not suitable for installing multiple antennas.

Therefore, the study of cognitive transmission theory based on the idea of cooperative relay has important research significance and research value for ensuring the high reliability transmission of wireless communication systems.

In a traditional cooperative diversity system based on time division multiplexing, a typical two-user cooperation scenario is: each user uses half of its own available time slot to send local information, and the other half to send partner relay information. Obviously, this kind of cooperative resource allocation method is not optimal, and it will lead to the expansion of system bandwidth and the rate loss of cooperative users. Therefore, how to design a more efficient cooperative resource allocation method is an important research direction in the field of cooperative diversity.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art, and propose a cognitive orthogonal cooperative transmission method in the presence of primary user interference, so as to perform cooperative transmission without increasing the system bandwidth, and at the same time reduce the rate of cooperative users loss.

To achieve the above object, technical solutions of the present invention include as follows:

(1) The secondary user source node s estimates the instantaneous channel state information a _q between itself and the primary user receiver v _q , determines its own transmission power P _s , and broadcasts the pilot signal with the transmission power P _s , 1≤q≤ M, M represents the number of primary user receivers;

(2) The secondary user destination node d estimates the instantaneous channel state information e _j between the primary user transmitter and the secondary user destination node, and at the same time estimates its received SINR ε _j according to the received signal quality, and according to the estimated signal The interference-to-noise ratio ε _j decodes the received signal, 1≤j≤N, and N represents the number of transmitters of the primary user;

(3) The secondary user destination node performs cyclic redundancy check on the decoded signal, and if the verification is successful, the secondary user source node starts to send data; if the verification fails, then perform step 4;

(4) All relay nodes estimate the received signal-to-interference-noise ratio γ _i according to the received pilot signal of the secondary user source node, and decode the received signal according to the received signal-to-interference-noise ratio γ _i estimated by themselves, 1≤i ≤K, K represents the number of relay nodes;

(5) All relay nodes perform cyclic redundancy check on the decoded signal:

If it fails to pass the verification, it is regarded as a decoding failure, and the relay node will no longer forward the source node information to the secondary user's destination node;

If the verification is passed, it is considered that the decoding is successful, and step (6) is performed;

(6) The relay node estimates the channel state information f _iq between itself and the primary user receiver, determines the transmission power P _i , and sends the pilot signal to the secondary user destination node with the transmission power P _i , and the secondary user destination node is receiving Reply a response signal after receiving the pilot signal sent by the relay node;

(7) Each relay node estimates the channel state information h _i between itself and the secondary user destination node according to the response signal received from the secondary user destination node, and combines the instantaneous channel state between the primary user transmitter and the secondary user destination node information e _j , to obtain the receiving SINR δ _i of each relay at the destination node of the secondary user;

(8) Based on the method of distributed timer, the relay node whose 1/δ _i in the timer decreases to 0 first is selected as the best relay r _b , and it forwards the recoded secondary user source node information Orthogonal replica to the secondary user destination node;

(9) The destination node of the secondary user uses the maximum ratio combining method to combine the signals of the source node of the secondary user received in two time slots to complete the cognitive orthogonal cooperative transmission.

Compared with the prior art, the present invention has the following advantages:

1. The present invention considers the cognitive orthogonal cooperative transmission when there is primary user interference, and selects the optimal relay to send orthogonal information under the primary user communication constraints, compared with the existing cooperative transmission method that does not consider the primary user communication constraints The secondary user cooperative communication can be realized on the premise of satisfying the requirement of user outage probability.

2. The present invention uses relay cooperative transmission, and different transmission nodes share each other's antennas, so that single-antenna nodes can also obtain the space diversity gain of multi-antenna nodes, while avoiding the impact of multi-antenna spatial correlation on system performance , and then improve the performance and capacity of the system, not only suitable for broadband cellular networks, but also suitable for wireless Ad-Hoc networks and wireless sensor networks.

3. In the whole coordinated transmission process, the present invention determines whether to use the relay coordinated transmission according to the channel quality of the direct transmission link, which not only meets the communication quality requirements, but also saves transmission power.

Description of drawings

Fig. 1 is a model diagram of the cognitive cooperative transmission relay network used in the present invention;

Fig. 2 is the realization flowchart of the present invention;

Fig. 3 is the change curve of the outage probability with the system signal-to-noise ratio SNRγ when there are multiple primary user interferences in the present invention;

Fig. 4 is the relationship between the outage probability and the number N of primary user transmitters when there are multiple primary user interferences in the present invention;

Fig. 5 is the relationship between the outage probability and the number M of primary user receivers when there are multiple primary user interferences in the present invention;

Fig. 6 is a variation curve of the outage probability with the outage threshold ξ of the primary user when there are multiple primary user interferences in the present invention.

detailed description

As shown in Figure 1, the latent cognitive cooperative transmission relay network in the Rayleigh fading environment and the presence of primary user interference includes the primary user network and the secondary user network. Among them, the primary user network consists of N primary user transmitters u _j and M primary user receivers v _q , 1≤q≤M, 1≤j≤N; the secondary user network consists of secondary user source nodes s, K It consists of the successor node r _i and the secondary user destination node d, 1≤i≤K.

In the secondary user network, the secondary user source node s tries to communicate with the secondary user destination node with the help of the direct link between the secondary user source node and the secondary user destination node or with the K selection cooperative decoding, forwarding relay. In Fig. 1, the solid line represents the transmission link of the secondary user source node, the dotted line represents the transmission link of the primary user transmitter, and the dotted line represents the transmission link of the relay node. All nodes in the network are equipped with a single omnidirectional antenna and work in half-duplex mode. The entire cognitive cooperative relay transmission process is divided into two time slots. Assume that the background noise of the receiver obeys additive white Gaussian noise with mean value 0 and variance N ₀ .

In the present invention, direct transmission or relay transmission is adaptively selected according to the channel quality between the secondary user source node and the secondary user destination node. In the first time slot of transmission, the source node of the secondary user broadcasts information to the destination node of the secondary user and all the relay nodes. According to the receiving SINR of the destination node of the secondary user, the destination node of the secondary user decides whether the relay node needs to coordinate transmission Secondary user source node information. If the receiving SINR of the secondary user destination node exceeds the threshold γ _s ′=2 ^Rs -1, the secondary user destination node sends positive feedback information, and the secondary user source node sends new information in the next time slot, where R _s represents the transmission rate of the secondary user; otherwise, the destination node of the secondary user sends negative feedback information, and selects the best relay from the source node information that can correctly decode the secondary user in the second time slot of the cognitive cooperative relay transmission. The good relay forwards the secondary user source node information to the secondary user destination node. For the latter case, the destination node of the secondary user uses the maximum ratio combining method to combine the signals of the source node of the secondary user received in two time slots.

Referring to Fig. 1, the present invention is based on the steps of performing cognitive orthogonal cooperative transmission in the presence of primary user interference in the above-mentioned network as follows:

Step 1, the secondary user source node s determines its own transmission power P _s , and broadcasts a pilot signal.

(1a) The secondary user source node s estimates the instantaneous channel state information a _q between itself and the primary user receiver v _q through the frequency band management device between the primary user and the secondary user or a channel estimator that does not need feedback;

(1b) According to the estimated instantaneous channel state information a _q , the secondary user source node s determines the transmit power P _s :

In the formula, M represents the number of primary user receivers, ξ represents the outage threshold of the primary user, that is, the maximum outage probability in the transmission of the primary user, where R _p represents the transmission rate of the primary user, N ₀ represents the variance of receiver additive white Gaussian noise, P _q represents the transmit power of the transmitter corresponding to the primary user receiver v _q , Represents the variance of the Rayleigh channel fading coefficient between the transmitter corresponding to the primary user receiver v _q and the primary user receiver v _q , Represents the variance of the Rayleigh fading coefficient of the instantaneous channel state information a _q between the secondary user source node s and the primary user receiver v _q .

(1c) The secondary user source node broadcasts the pilot signal with transmit power P _s .

Step 2, the secondary user destination node estimates the received SINR ε _j and decodes the received signal.

Since the signal received by the secondary user destination node includes the signal sent by the primary user transmitter in addition to the pilot signal broadcast by the secondary user source node, it is necessary to estimate the instantaneous channel state information between the primary user transmitter and the secondary user destination node.

(2a) Estimate the instantaneous channel state information e _j between the primary user transmitter and the secondary user destination node using the same method as obtaining a _q in step (1a) or by listening to the pilot signal sent by the primary user transmitter;

(2b) The secondary user destination node estimates its received SINR ε _{j according to the received signal quality and instantaneous channel state information e j ;}

(2c) The secondary user destination node decodes the received signal according to the estimated SINR ε _j .

In step 3, the destination node of the secondary user performs a cyclic redundancy check on the decoded signal.

At the beginning of the transmission, the source node of the secondary user and the destination node of the secondary user agree on a generator polynomial. If the code word polynomial after decoding can be divisible by the agreed generator polynomial, the verification is successful, indicating that the direct connection between the source node of the secondary user and the destination node of the secondary user If the quality of the transmission channel is good, the relay node does not need cooperative transmission, and the source node of the secondary user starts to send data; otherwise, the verification fails, and step 4 is performed.

Step 4, the relay node estimates the received SINR γ _i and decodes the received signal.

The signal received by the relay node includes the signal sent by the primary user transmitter in addition to the signal of the secondary user source node, so it is necessary to estimate the instantaneous channel state information between the primary user transmitter and the relay node.

(4a) The relay node estimates the instantaneous channel state information between the primary user transmitter and the relay node using the same method as obtaining e _j in step (2a);

(4b) The relay node estimates its received SINR γ _i according to the received signal quality and the instantaneous channel state information between the primary user transmitter and the relay node, 1≤i≤K;

(4c) The relay node decodes the received signal according to the received SINR γ _i estimated by itself.

Step 5, all relay nodes perform cyclic redundancy check on the decoded signal.

At the beginning of the transmission, the source node of the secondary user and the relay node agree on a generator polynomial. If the decoded code word polynomial cannot be divisible by the agreed generator polynomial, it will be regarded as a decoding failure, and the relay node will no longer forward the information of the source node to the destination of the secondary user. node; if it can be divisible, the decoding is considered successful, and step (6) is performed.

Step 6, the relay node sends a pilot signal with transmission power _Pi , and the secondary user destination node replies with a response signal;

(6a) The relay node estimates the channel state information f _iq between itself and the primary user receiver using the same method as obtaining a _q in step (1a);

(6b) According to the estimated channel state information, the relay node determines the transmit power P _i :

In the formula, M represents the number of primary user receivers, ξ represents the outage threshold of the primary user, that is, the maximum outage probability in the transmission of the primary user, where R _p represents the transmission rate of the primary user, N ₀ represents the variance of receiver additive white Gaussian noise, P _q represents the transmit power of the transmitter corresponding to the primary user receiver v _q , Represents the variance of the Rayleigh channel fading coefficient between the transmitter corresponding to the primary user receiver v _q and the primary user receiver v _q , Represents the variance of the Rayleigh fading coefficient of the channel state information f _iq between the relay node r _i and the primary user receiver v _q ;

(6c) The relay node sends the pilot signal to the secondary user destination node with the transmit power _Pi ;

(6d) The destination node of the secondary user replies with a response signal after receiving the pilot signal sent by the relay node;

In step 7, each relay node that successfully decodes obtains its received SINR δ _i at the destination node of the secondary user.

(7a) The relay node estimates the channel state information h _i between it and the secondary user destination node according to the received response signal from the secondary user destination node;

(7b) The relay node combines the channel state information h _i and the instantaneous channel state information e _j between the primary user transmitter and the secondary user destination node to obtain the receiving SINR δ _i of each relay at the secondary user destination node:

In the formula, P _i represents the transmission power of the secondary user relay node r _i , h _i represents the channel state information between the relay node r _i and the secondary user destination node, P _j represents the transmission power of the primary user transmitter u _j , ε _j represents the channel state information between the primary user transmitter u _j and the secondary user destination node d, and N ₀ represents the variance of receiver additive white Gaussian noise.

Step 8: Select the best orthogonal copy of relay decoding and forwarding source node information.

Based on the method of distributed timer, the relay node whose 1/δ _i decreases to 0 first in the timer is selected as the best relay r _b , and the best relay r _b re-encodes the secondary user source node information, and the An orthogonal copy of the information is forwarded to the secondary user destination node.

In step 9, the destination node of the secondary user combines the signals received from the source node of the secondary user in two time slots by using the maximum ratio combination method to complete the cognitive orthogonal cooperative transmission.

Effect of the present invention can be further illustrated by simulation:

A. Simulation conditions

suppose P _j =P _q =P _u , 1≤q≤M, 1≤j≤N, 1≤i≤K, where, Represents the variance of the Rayleigh channel fading coefficient between the transmitter corresponding to the primary user receiver v _q and the primary user receiver v _q , Denotes the variance of the Rayleigh channel fading coefficient between the secondary user source node s and the primary user receiver v _q , Denotes the variance of the Rayleigh channel fading coefficient between the relay node r _i and the primary user receiver v _q , Represents the variance of the Rayleigh channel fading coefficient of the secondary user source node s and the relay node r _i , Represents the variance of the Rayleigh channel fading coefficient between the secondary user source node s and the secondary user destination node d, Represents the variance of the Rayleigh channel fading coefficient between the relay node r _i secondary user destination node d, Denotes the variance of the Rayleigh channel fading coefficient between the primary user transmitter u _j and the relay node r _i , Represents the variance of the Rayleigh channel fading coefficient between the primary user transmitter u _j and the secondary user destination node d, P _j represents the transmission power of the primary user transmitter u _j , and P _q represents the transmission power of the primary user receiver v _q .

Assuming the average channel gain of primary user transmission link, secondary user direct link and relay transmission link with Relatively large, while the average channel gain between the secondary user node and the primary user node and between the primary user node and the secondary user node with Relatively small.

There are three existing methods used in the simulation: 1. Selective cooperative relay transmission when the direct transmission link between the secondary user source node and the secondary user destination node is unavailable, abbreviated as no direct link scenario; 2. Secondary user source node The direct transmission link with the secondary user destination node is available and uses SC to combine the signals received by the secondary user destination node for selective cooperative relay transmission, abbreviated as SC; 3. The secondary user destination node adopts MRC to combine through the direct transmission link Selective coordinated relay transmission of the received signal and the signal received via the relay transmission link, abbreviated as MRC.

B. Simulation content

Simulation 1: Under the condition that the system SNR γ=1/N ₀ changes, take P _u = 3dB, R _p = 1bit/s/Hz, R _s = 1bit/s/Hz, ξ=0.1, K=3, N=2, M=2, simulate the variation curves of the outage probability of the present invention and the existing three methods with the system SNR, and the results are shown in FIG. 3 .

Simulation 2: When the number of primary user transmitters is 2 and 8, take P _u = 3dB, R _p = 1bit/s/Hz, R _s = 1bit/s/Hz, ξ=0.1, K=6, M=2, simulate the influence of the change of the number of primary user transmitters on the outage probability of the present invention and the three existing methods, and the results are shown in FIG. 4 .

Simulation 3: When the number of primary user receivers is 2 and 8, take P _u = 3dB, R _p = 1bit/s/Hz, R _s = 1bit/s/Hz, ξ=0.1, K=6, N=2, simulate the influence of the change of the number of primary user receivers on the outage probability of the present invention and the three existing methods, and the results are shown in FIG. 5 .

Simulation 4: When the interrupt threshold ξ of the primary user changes, take P _u = 3dB, R _p = 1bit/s/Hz, R _s = 1bit/s/Hz, N ₀ = 0dB, K = 3, N = 2, M = 2, simulate the interruption of the present invention and the existing three methods The change curve of the probability with the interruption threshold ξ of the primary user is shown in Figure 6.

C. Simulation results

It can be seen from Figure 3 that with the increase of SNRγ, the outage probability of cognitive secondary users decreases when γ is relatively small, however, when γ is relatively large, the outage probability of cognitive secondary users remains basically unchanged. It can be seen that the outage performance of the scenario where the direct link of the secondary user is available is better than the outage probability of the scenario where the direct link of the secondary user is unavailable, and the performance of the present invention is the best among the four selective cooperative relay transmission strategies. This is because the received signal strength of the secondary user destination node is enhanced by combining the signal from the direct link of the secondary user and the signal from the relay link received by the destination node of the secondary user by adopting a combining technique. Figure 3 also shows the simulation results and asymptotic results of the outage probability, and the simulation results and theoretical analysis results completely coincide, and the asymptotic value in the high SNR area is very close to the theoretical value.

It can be seen from Fig. 4 that when the number of transmitters of the primary user increases, more interference will be brought to the received signals of the relay node and the target node of the secondary user, thus resulting in a decrease in the performance of recognizing the secondary user. In addition, it can be found through careful observation that the performance of the present invention is better in a scenario where the number of primary user receivers is large.

It can be seen from Fig. 5 that when the number of primary user receivers increases, the transmit power of the transmitting nodes in the secondary user network is restricted more strictly, and therefore, the outage probability of cognitive secondary users increases. Same as in Fig. 4, the outage probability difference between selective cooperative relay transmission using MRC and orthogonal cooperative transmission increases with the increase of the number of primary user receivers, and the performance of the present invention is comparatively better.

It can be seen from Figure 6 that the outage probability performance of the cognitive secondary user increases with the weakening of the interference limit of the primary user, that is, the outage probability of the cognitive secondary user decreases with the increase of the primary user outage threshold ξ; it can also be seen that The average channel gain between a primary user's transmitter and its corresponding receiver given the primary user's outage threshold The larger the , the smaller the outage probability of the cognitive secondary user is, because the transmit power of the cognitive secondary user varies with The increase increases, comparatively speaking, the performance of the present invention is still better.

In summary, the performance of the method of the present invention is better than that of the existing method in cognitive orthogonal cooperative transmission when there is primary user interference.

Claims (4)

1. A cognitive orthogonal cooperative transmission method when there is primary user interference, comprising the steps of: (1) The secondary user source node s estimates the instantaneous channel state information a _q between itself and the primary user receiver v _q , determines its own transmission power P _s , and broadcasts the pilot signal with the transmission power P _s , 1≤q≤ M, M represents the number of primary user receivers; (2) The secondary user destination node d estimates the instantaneous channel state information e _j between the primary user transmitter and the secondary user destination node, and at the same time estimates its received SINR ε _j according to the received signal quality, and according to the estimated signal The interference-to-noise ratio ε _j decodes the received signal, 1≤j≤N, and N represents the number of transmitters of the primary user; (3) The secondary user destination node performs cyclic redundancy check on the decoded signal, and if the verification is successful, the secondary user source node starts to send data; if the verification fails, then perform step 4; (4) All relay nodes estimate the received signal-to-interference-noise ratio γ _i according to the received pilot signal of the secondary user source node, and decode the received signal according to the received signal-to-interference-noise ratio γ _i estimated by themselves, 1≤i ≤K, K represents the number of relay nodes; (5) All relay nodes perform cyclic redundancy check on the decoded signal: If the verification fails, it will be deemed as a decoding failure, and the relay node will no longer forward the source node information to the secondary user's destination node; If the verification is passed, it is considered that the decoding is successful, and step (6) is performed; (6) The relay node estimates the channel state information f _iq between itself and the primary user receiver, determines the transmission power P _i , and sends the pilot signal to the secondary user destination node with the transmission power P _i , and the secondary user destination node is receiving Reply a response signal after receiving the pilot signal sent by the relay node; (7) Each relay node estimates the channel state information h _i between itself and the secondary user destination node according to the response signal received from the secondary user destination node, and combines the instantaneous channel state between the primary user transmitter and the secondary user destination node information e _j , to obtain the receiving SINR δ _i of each relay at the destination node of the secondary user; (8) Based on the method of distributed timer, the relay node whose 1/δ _i in the timer decreases to 0 first is selected as the best relay r _b , and it forwards the recoded secondary user source node information Orthogonal replica to the secondary user destination node; (9) The destination node of the secondary user uses the maximum ratio combining method to combine the signals of the source node of the secondary user received in two time slots to complete the cognitive orthogonal cooperative transmission. 2. The cognitive orthogonal cooperative transmission method when there is primary user interference according to claim 1, wherein the transmit power P _s of determining the secondary user source node s in step (1) is selected according to the following formula: ${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \&lsqb;</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&xi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; q</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; \&rsqb;</span>$ In the formula, M represents the number of primary user receivers, ξ represents the outage threshold of the primary user, that is, the maximum outage probability in the transmission of the primary user, where R _p represents the transmission rate of the primary user, N ₀ represents the variance of receiver additive white Gaussian noise, P _q represents the transmit power of the transmitter corresponding to the primary user receiver v _q , Represents the variance of the Rayleigh channel fading coefficient between the transmitter corresponding to the primary user receiver v _q and the primary user receiver v _q , Indicates the variance of the Rayleigh channel fading coefficient between the secondary user source node s and the primary user receiver v _q . 3. The cognitive orthogonal cooperative transmission method when there is primary user interference according to claim 1, wherein the transmit power P _i of the secondary user relay node r _i is determined in step (6), and is selected by the following formula: ${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \&lsqb;</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&xi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; q</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; \&rsqb;</span>$ In the formula, M represents the number of primary user receivers, ξ represents the outage threshold of the primary user, that is, the maximum outage probability in the transmission of the primary user, where R _p represents the transmission rate of the primary user, N ₀ represents the variance of receiver additive white Gaussian noise, P _q represents the transmit power of the transmitter corresponding to the primary user receiver v _q , Represents the variance of the Rayleigh channel fading coefficient between the transmitter corresponding to the primary user receiver v _q and the primary user receiver v _q , Denotes the variance of the Rayleigh channel fading coefficient between the relay node _ri and the primary user receiver _vq . 4. The cognitive orthogonal cooperative transmission method when there is primary user interference according to claim 1, wherein in step (7), the receiving signal-to-interference-noise ratio δ _i of each relay at the secondary user destination node is obtained by the following formula : ${\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}$ In the formula, P _i represents the transmission power of the secondary user relay node r _i , h _i represents the channel state information between the relay node r _i and the secondary user destination node, P _j represents the transmission power of the primary user transmitter u _j , ε _j represents the channel state information between the primary user transmitter u _j and the secondary user destination node d, and N ₀ represents the variance of receiver additive white Gaussian noise.