A cr_noma-based enhanced multiple access method and system

Abstract

The application discloses an enhanced multiple access method and system based on CR_NOMA, and belongs to the technical field of multiple access technology of wireless communication systems, and comprises the following steps: a secondary user SU in a cognitive radio network senses the spectrum state of a primary user PU, and initiates a spectrum access request to a fusion center FC; the FC determines an optimal spectrum hole access scheme after comprehensively deciding by applying an AI-based learning algorithm and feeds back to each requesting SU; finally, the SU communicates using the indicated hole spectrum according to the feedback result. The base station receiving end, all users under the same frequency band apply a mixed serial interference cancellation SIC decoding mechanism to separate users. Compared with other multiple access methods, the application has the advantages of significant spectrum efficiency improvement and small calculation complexity. Not only can it be applied to the scene of multiple users simultaneously requesting access, but also in the special scene of single user requesting access, through the application of the "mutual interference" index, the same system performance can be obtained with lower calculation complexity.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of multiple access technology of wireless communication system, and more particularly, relates to an enhanced multiple access method and system based on CR_NOMA. BACKGROUND

[0002] It is known that the next generation of mobile communication (6G) will open up the era of everything intelligent connection, and it is expected that the number of device connections will be 10 times more than in 2020 by 2030. In order to support such a large number of connections, higher requirements will be put forward for the next generation of multiple access. At the same time, in the face of the emergence of more new applications in 6G, strict requirements are put forward for rate, delay and reliability. Therefore, in the future 6G network, how to meet the above requirements while improving the spectrum efficiency under the increasingly scarce spectrum resources will be the research focus of the next generation of multiple access technology.

[0003] The existing methods are divided into two categories: one is based on orthogonal multiple access (OMA), such as TDMA, FDMA, CDMA, OFDMA, which can only serve one user on one basic communication resource block. In contrast, the other is based on non-orthogonal multiple access (NOMA), which can serve multiple users on one basic communication resource block, thereby achieving significant performance gains in terms of spectrum efficiency, maximum number of connections, and delay compared to traditional orthogonal multiple access systems. As for the research on NOMA, it is divided into two directions: one is based on hybrid multiple access technology, which integrates existing multiple access technologies such as OMA, power domain NOMA, and spatial domain NOMA, dynamically switches multiple access technology application according to application requirements and network conditions, reduces excessive power consumption caused by single NOMA application, and avoids unnecessary non-orthogonality. However, this type of scheme is only a dynamic switching of existing multiple access technologies (OMA, power domain NOMA, and spatial domain NOMA), and essentially does not apply new technologies to improve spectrum efficiency, nor does it consider the reuse of idle resources. The other is to study CR_NOMA, which regards NOMA as a special CR and studies it in two paradigms of traditional CR. The research on CR_NOMA mainly focuses on: spectrum sensing problem research, maximum number of secondary users (SU) access research, resource allocation problem research of shared spectrum cluster, and power allocation problem research within secondary user cluster. For the research on spectrum hole allocation, the current research assumes that the spectrum hole is continuous or discrete orthogonal unit idle spectrum, which obviously does not conform to the current 5G system based on NOMA shared spectrum scheme.

[0004] A reasonable and effective spectrum hole access scheme can help users to reasonably occupy spectrum holes, otherwise, low spectrum efficiency, serious user interference or multiple users competing for the same hole will occur. However, the applicant has not found a multi-access method that can simultaneously guarantee large connection support and guarantee the QoS requirements of each user for 6G. SUMMARY

[0005] In view of the defects of the prior art and the need for improvement, the present application provides an enhanced multi-access method and system based on CR_NOMA, aiming to solve the technical problems of unreasonable PU user access structure, high SU user interruption probability, difficult to guarantee the QoS requirements of each user, and high computational complexity in the prior art.

[0006] To achieve the above-mentioned purpose, in a first aspect, the present application provides an enhanced multi-access method based on CR_NOMA, comprising:

[0007] The secondary user SU in the cognitive radio network senses the spectrum state of the primary user PU, and initiates a spectrum access request to the fusion center FC; wherein the licensed spectrum is divided into multiple orthogonal sub-bands, and the PUs in a single sub-band share the spectrum in the form of NOMA, and the requesting SU is one or more;

[0008] The FC obtains all the spectrum hole sets at the current time, and determines the optimal spectrum hole access strategy based on the criterion of maximizing the total spectrum efficiency of the system after each requesting SU accesses, and feeds back to each requesting SU; wherein the SIC decoding mechanism based on QoS is applied to separate users between PUs and SUs in the same frequency band, and the SIC decoding mechanism based on CSI is applied to separate users within PUs and PUs, and SUs and SUs;

[0009] Each requesting SU communicates using the indicated hole spectrum according to the feedback.

[0010] Further, the optimal spectrum hole access strategy B oas is represented as:

[0011]

[0012] Wherein, B = {B1, B2,..., B n} represents the set of spectrum hole access strategies, n represents the total number of access strategies, b represents a certain access strategy, and u represents a certain user in the access strategy b; represents that under the i-th access strategy, the SU accesses N i sub-bands, i = 1,..., n; represents the user set in the k-th sub-band under the i-th access strategy, which includes S q busy PUs and Sp SINR of the user u under the access strategy b. b,u SINR of the user u under the access strategy b.

[0013] SINR of the user u under the access strategy b. b,u SINR of the user u under the access strategy b.

[0014]

[0015] SINR of the user u under the access strategy b. b,u SINR of the user u under the access strategy b. b,u SINR of the user u under the access strategy b. b,j SINR of the user u under the access strategy b.

[0016] Further, when the hole PU activates the reuse spectrum, the SU unconditionally forces to quit and give up the right to use the spectrum; after the interval period time T, the SU initiates the next round of sensing request again.

[0017] In a second aspect, the application provides an enhanced multiple access method based on CR_NOMA, comprising:

[0018] The secondary user SU in the cognitive radio network senses the spectrum state of the primary user PU, and initiates a spectrum access request to the fusion center FC; wherein the licensed spectrum is divided into multiple orthogonal sub-bands, and the PU shares the spectrum in the form of NOMA in a single sub-band, and the requesting SU is one;

[0019] The FC obtains all the spectrum hole sets at the current time, and determines the optimal spectrum hole access strategy according to the criterion that the sum of mutual interference values between the requesting SU and all other users in the same frequency band after the SU accesses is minimum, and feeds back to the requesting SU; wherein the SIC decoding mechanism based on QoS is applied to separate users between the PU and the SU among all users in the same frequency band, and the SIC decoding mechanism based on CSI is applied to separate users among the PU and the PU, and the SU and the SU.

[0020] Each requesting SU communicates using the indicated hole spectrum according to the feedback.

[0021] Further, the mutual interference value between the user u1 and the user u2 is The mutual interference value between the user u1 and the user u2 is

[0022]

[0023] The mutual interference value between the user u1 and the user u2 is b,u1 and H b,u2 respectively represent the channel vectors of the user u1 and the user u2 under the access strategy b.

[0024] Further, when the hole PU activates the reuse spectrum, the SU unconditionally forces the exit, giving up the right to use the spectrum; after the interval period time T, the SU initiates the next round of sensing request again.

[0025] In a third aspect, the present application provides an enhanced multiple access system based on CR_NOMA, characterized in that it comprises a computer readable storage medium and a processor.

[0026] The computer readable storage medium is used to store executable instructions.

[0027] The processor is used to read the executable instructions stored in the computer readable storage medium, and execute the enhanced multiple access method based on CR_NOMA as described in the first aspect or the second aspect.

[0028] Overall, the above technical solutions conceived by the present application can achieve the following beneficial effects:

[0029] 1. The SU accesses the spectrum resource by multiplexing the idle PU spectrum hole, which is based on the hybrid paradigm of CR_NOMA on the basis of the underlay and overlay paradigms of the existing CR_NOMA. To avoid the high SU interruption probability and large PU interference caused by the hybrid paradigm access method, the present application accesses the idle spectrum resource by multiplexing the PU spectrum hole. Compared with other multiple access methods, the design method of the present application not only supports large connection demand, but also guarantees the QoS demand of each user.

[0030] 2. Compared with other multiple access methods, the design method of the present application not only applies to the spectrum hole allocation scheme for multiple users to access at the same time, but also for the special scene of single user access, through the application of "mutual interference" index, the same system performance can be obtained with lower computational complexity.

[0031] 3. The multiple access method proposed by the present application has certain implementability and practical popularization value, and belongs to an open framework scheme, which can be applied together with other types of cluster allocation technology, power allocation technology, etc. It can be determined that under the multiple access method designed by the present application, the waste of spectrum resources can be effectively avoided, and additional performance improvement can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 A flowchart of an enhanced multiple access method based on CR_NOMA provided for the first embodiment of the present application is shown in the figure.

[0033] Figure 2 A flowchart of another enhanced multiple access method based on CR_NOMA provided for the second embodiment of the present application is shown in the figure.

[0034] Fig. 3(a) and Fig. 3(b) are respectively a SU access whole process state transition diagram and an interaction timing diagram;

[0035] Figure 4 Fig. 2 is a cognitive radio system uplink communication model schematic diagram provided for Embodiment 3 of the present application;

[0036] Figure 5 Fig. 3 is a CR_NOMA-based enhanced multiple access and existing CR_NOMA technology comparison schematic diagram provided for Embodiment 3 of the present application;

[0037] Figure 6 Fig. 4 is a multi-user simultaneous access scheme in the design method of the present application and other multiple access methods comparison diagram provided for Embodiment 3 of the present application;

[0038] Figure 7 Fig. 5 is a single-user access scheme in the design method of the present application and other multiple access methods (NOMA and OMA) system spectrum efficiency comparison diagram provided for Embodiment 3 of the present application. DETAILED DESCRIPTION

[0039] In order to make the purpose, system composition, technical scheme and advantages of the present application more clear and understandable, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not used to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0040] In the present application, the terms "first", "second", etc. (if any) in the present application and the drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence.

[0041] Embodiment 1

[0042] Referring to Figure 1 , in combination with Fig. 3(a) and Fig. 3(b), the present application provides a CR_NOMA-based enhanced multiple access method, including operations S1 to S3.

[0043] Operation S1, a secondary user SU in a cognitive radio network senses the spectrum state of a primary user PU, and initiates a spectrum access request to a fusion center FC; wherein the licensed spectrum is divided into a plurality of orthogonal sub-bands, and the PU in a single sub-band shares the spectrum in the form of NOMA, and the requesting SU is one or more.

[0044] In this embodiment, the SU initiates a sensing request, and simultaneously sends a self-demand data packet (including: self-CSI, self-QoS) to the fusion center FC.

[0045] The Subscriber (SU) accesses and uses spectrum resources by reusing idle PU spectrum holes. Based on the existing CR_NOMA underlay and overlay paradigms, this invention innovatively studies a hybrid paradigm based on CR_NOMA. To avoid the drawbacks of high SU outage probability and significant PU interference caused by the hybrid paradigm access method, this invention accesses idle spectrum resources by reusing PU spectrum holes.

[0046] Since the PU (Power Utility) belongs to the licensed spectrum, it exists in two states: busy and idle. When the PU is not using its own spectrum resources, the PU is in an idle state, and its spectrum resources can be reused by the SU (Subscriber Unit) requesting access in the cognitive radio network.

[0047] The licensed spectrum is divided into multiple orthogonal sub-bands, which exist in an orthogonal relationship and do not interfere with each other; and multiple PUs within a sub-band reuse the spectrum through power domain NOMA. When there are PU spectrum holes, the SU access spectrum holes share the spectrum with other PUs in the same frequency band through NOMA.

[0048] Among them, the SU access spectrum hole and other PUs in the same frequency band share the spectrum through NOMA. This means that in a single sub-band, the existing busy-time PU still exists in the form of NOMA, and the access SU reuses the spectrum hole of the idle PU. This method is different from the existing CR_NOMA method, which assumes that the busy-time PU exists in a single orthogonal manner.

[0049] Operation S2: FC obtains the set of all spectrum holes at the current time, and determines the optimal spectrum hole access strategy based on maximizing the total spectrum efficiency of the system after each requesting SU accesses, and feeds it back to each requesting SU; among all users in the same frequency band, PU and SU are separated by a QoS-based SIC decoding mechanism, and PU and SU are separated by a CSI-based SIC decoding mechanism.

[0050] In this embodiment, the FC actively acquires the set of all spectrum holes at the current time (including: idle PU spectrum, CSI of other busy PUs in the same sub-band).

[0051] Optimal Spectrum Hole Access Strategy B oas Represented as:

[0052]

[0053] Where, B = {B1, B2, ..., B} n} represents the spectrum hole access policy set, n represents the total number of access policies, b represents a certain access policy, and u represents a certain user in access policy b; This indicates that under the i-th access strategy, SU has accessed N in total. isub-bands, i = 1,..., n; S k i represents the set of users in the kth sub-band under the ith access strategy, which includes S q busy PUs and S p accessed SUs; SINR b,u SINR u b represents the signal-to-interference-and-noise ratio of user u under the access strategy b.

[0054] SINR u b represents the signal-to-interference-and-noise ratio of user u under the access strategy b. b,u SINR u b is represented as:

[0055]

[0056] where p b,u P u b represents the transmission power of user u under the access strategy b, H b,u H u b represents the normalized channel gain of user u under the access strategy b, N is a Gaussian white noise, and I b,j I u b represents the interference value of user u from all other users in the same sub-band.

[0057] The specific steps are as follows: in the initial stage of the iteration process, first randomly allocate the SUs requesting access to the currently available spectral holes. Then randomly exchange the SUs or keep them unchanged without exchange. The principle of deciding whether to exchange the SUs is: when the allocated spectral holes make the total spectral efficiency of the system only increase but not decrease, keep them unchanged without exchange; if the total spectral efficiency of the system decreases, exchange the SUs to different spectral holes. The finally output spectral hole allocation scheme is the allocation strategy with the maximum total spectral efficiency of the system at the access moment.

[0058] After the SU accesses the spectral hole, in order to ensure the quality of service of the busy PUs in the sub-band, the interference of the accessed SU to the PUs in the same sub-band should be within the tolerable threshold value. At the same time, in order to ensure the QoS requirement of the accessed SU itself, when all users in the same sub-band apply the NOMA decoding mechanism, an adaptive hybrid successive interference cancellation (SIC) decoding scheme is adopted: a CSI-based SIC decoding scheme and a QoS-based SIC decoding scheme.

[0059] The specific steps are as follows:

[0060] 1) Apply the QoS-based SIC decoding mechanism between the PUs and the SUs: decode the PU users first, and decode the SU users last;

[0061] 2) PU and PU, SU and SU respectively apply CSI_SIC decoding mechanism: that is, the receiving end receives multi-user signals, sorts them according to signal power; then, the data is judged, the signals of the larger power users are processed preferentially, and the multi-access interference of one user signal is subtracted after the judgment; then the amplitude is recovered, and the remaining users are judged again; repeat the operation until all the multi-access interference of the signals is removed.

[0062] Operation S3, each requested SU uses the indicated spectral hole according to the feedback for communication.

[0063] In this embodiment, after receiving the feedback, the SU decides whether to access the indicated spectral hole.

[0064] 1) No available spectral hole

[0065] After the interval period time T, the SU initiates the next round of sensing request again.

[0066] 2) SU accesses the spectral hole

[0067] Method one: the SU keeps the data communication task, uses it up, and actively releases it.

[0068] Method two: the hole PU activates the reuse of the spectrum, and the SU unconditionally forces to exit, giving up the right to use the spectrum; and after the interval period time T, the SU initiates the next round of sensing request again.

[0069] 3) SU is not satisfied and refuses to access the spectral hole

[0070] After the interval period time T, the SU initiates the next round of sensing request again.

[0071] For example, the SU is not satisfied means that the spectral bandwidth of the spectral hole is not enough.

[0072] Embodiment 2

[0073] For the single SU to initiate sensing and request to access the spectrum, the spectral hole allocation scheme in embodiment 1 is certainly applicable to the criterion of maximizing the total spectral efficiency of the system, however, in this special scenario, this embodiment further proposes a single-user access scheme, which can achieve the optimal hole selection case and further simplify the calculation complexity.

[0074] Referring to Figure 2 , combined with FIG. 3(a) and FIG. 3(b), the application further provides an enhanced multi-access method based on CR_NOMA, which comprises operations S1' to S3'.

[0075] Operation S1', a secondary user (SU) in a cognitive radio network senses a spectrum state of a primary user (PU) and initiates a spectrum access request to a fusion center (FC); wherein the licensed spectrum is divided into multiple orthogonal sub-bands, and the PUs share the spectrum in a NOMA form in a single sub-band, and the requesting SU is one.

[0076] Operation S2', the FC obtains all spectrum hole sets at the current time, and determines an optimal spectrum hole access strategy according to the criterion that the sum of mutual interference values between the requesting SU and all other users in the same frequency band after the SU accesses the spectrum hole, and feeds back the optimal spectrum hole access strategy to the requesting SU; wherein the SIC decoding mechanism based on QoS is applied to separate users between the PU and the SU among all users in the same frequency band, and the SIC decoding mechanism based on CSI is applied to separate users among the PUs and among the SUs.

[0077] Operation S3', each requesting SU accesses the spectrum hole according to the feedback.

[0078] Different from embodiment 1, in this embodiment, the optimal spectrum hole access strategy is determined according to the criterion that the sum of mutual interference values between the requesting SU and all other users in the same frequency band after the SU accesses the spectrum hole, and the remaining operations are the same as those in embodiment 1.

[0079] In this embodiment, the "mutual interference" index (which refers to the mutual interference between the accessing SU and other users in the same frequency band) is introduced, and the AI-based random learning algorithm is used to design the spectrum hole allocation scheme according to the criterion that the system "mutual interference" index value is minimum. This is because, the smaller the mutual interference value between multiple users, the more suitable it is for these users to share the spectrum; on the contrary, if the mutual interference value between the accessing SU and other users in the same frequency band becomes larger, it is not suitable.

[0080] The specific steps are as follows: the fusion center (FC) traverses all current holes, finds the hole with the minimum "mutual interference" value after the SU accesses the hole, and considers it as the optimal access hole. The mutual interference value between any two users u1 and user u2 is represented as:

[0081]

[0082] wherein H b,u1 and H b,u2 represent the channel vectors of the user u1 and the user u2 under the access strategy b, respectively.

[0083] Embodiment 3

[0084] Figure 4Fig. 1 is a schematic diagram of an uplink communication model of a cognitive radio system provided by the embodiment, and the CR_NOMA-based enhanced multiple access method of the application is applied to the system and a multipath Rayleigh fading channel to improve the overall spectral efficiency of the system. In the embodiment, there is a fusion center (FC), P primary users (PUs) and S secondary users (SUs). The PUs communicate with the base station through licensed spectrum, which is orthogonal between different sub-bands, and multiple PUs in a sub-band multiplex the spectrum through power domain NOMA. The base station receiver separates the superimposed signals of multiple PU users through a CSI-based SIC decoding mechanism.

[0085] Unlike the enhanced multiple access method based on CR_NOMA proposed by the application, the existing enhanced multiple access method based on CR_NOMA regards NOMA as a special case of CR and studies two paradigms of traditional CR, such as Figure 5 Fig. 2 is a schematic diagram of the comparison between the enhanced multiple access based on CR_NOMA and the CR_NOMA technology. Specifically,

[0086] 1) In the overlay mode, the secondary user (SU) can only access the spectrum when it is confirmed that the current spectrum is not occupied by the primary user (PU). Therefore, there is an orthogonal relationship between the PU and the SU, and the SU accesses the idle frequency band in the form of NOMA. When the idle PU needs to use the spectrum again, all the accessed SUs need to exit immediately, so the interruption probability of the SU is generally high, and the application value is low.

[0087] 2) In the underlay mode, the SU does not need to wait for the PU to exit the channel, but can access the channel on the premise that the interference to the PU is controlled within a certain threshold. In this mode, the PU exists in the form of OMA, and NOMA is applied to the access of multiple SUs in the same frequency band. Since the number of SUs accessing in this mode increases, the interference to the PU in the same frequency band also greatly increases, and the QoS of the PU may be difficult to guarantee.

[0088] Figure 6 In the scenario, the number of PUs in the busy state is 14, the number of spectral holes is 9, the maximum number of allowed SUs is 9, and the number of base station antennas is 6. From Figure 6It can be seen from the figure that, the spectrum efficiency can be improved significantly by constantly learning and searching for more suitable spectrum holes, and the total spectrum efficiency and the convergence times are reduced synchronously with the decrease of the number of SUs. Only by reasonably and sufficiently reusing the spectrum holes can the maximum system spectrum efficiency be achieved. Different from the existing CR-NOMA multiple access technology, the existing CR-NOMA technology takes NOMA as a special case of CR, studies the spectrum shared by PUs and SUs, and selects the decoding order according to the QoS. However, the existing CR-NOMA technology does not involve the research on the multiple PUs sharing NOMA. Therefore, in the current 5G communication environment dominated by NOMA, the design method of the present application can improve the spectrum efficiency significantly compared with the CR-NOMA. From Figure 6 It can also be seen from the figure that, when the design method of the present application achieves the optimal allocation, the system spectrum efficiency is improved by 17.4% compared with the CR-NOMA, and is improved by 25.7% compared with the NOMA with spectrum resource vacancy.

[0089] Figure 7 Four groups of single-user access scenarios with different numbers of users are shown, and the average spectrum efficiency of different schemes is calculated under 100 independent random tests. Figure 7 It can be seen that:

[0090] (1) The spectrum efficiency of the single-user optimal spectrum hole access method proposed in the present application is better than that of the random spectrum hole access scheme.

[0091] (2) Reusing the spectrum holes can indeed improve the overall system spectrum efficiency and reduce the waste of spectrum vacancy resources.

[0092] (3) The scheme of selecting the minimum value of mutual interference instead of directly calculating the spectrum efficiency is better than the scheme of randomly selecting the spectrum hole access. It can also be proved that the smaller the mutual interference between users, the more suitable it is to share the spectrum, thereby improving the overall spectrum efficiency.

[0093] (4) As can be seen from the comparison chart of the above four groups of independent single-user access scenarios, with the decrease of the number of PUs and the number of selectable spectrum holes, the difference between the system spectrum efficiency after reusing the spectrum holes in the design method of the present application and the spectrum efficiency of NOMA without reusing the spectrum holes becomes more and more significant. Therefore, it also shows that, in the case of small number of users, reusing the spectrum holes in single-user access can indeed significantly reduce the waste of spectrum resources and indirectly improve the system spectrum efficiency.

[0094] Those skilled in the art will readily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An enhanced multiple access method based on CR_NOMA, characterized in that, include: In a cognitive radio network, a secondary user (SU) senses the spectrum status of a primary user (PU) and initiates a spectrum access request to the convergence center (FC). The licensed spectrum is divided into multiple orthogonal sub-bands, and multiple PUs in a single sub-band share the spectrum in a NOMA (Normally Orthogonal Array) configuration. The requesting SU can be one or more SUs. The FC obtains the set of all spectrum holes at the current moment, and determines the optimal spectrum hole access strategy based on maximizing the total spectrum efficiency of the system after each requesting SU accesses, and feeds it back to each requesting SU. Among all users in the same frequency band, users are separated between PU and SU using a QoS-based SIC decoding mechanism, and users are separated between PU and PU, and between SU ​​and SU using a CSI-based SIC decoding mechanism. Each requesting SU communicates using the indicated hole spectrum based on the feedback; The optimal spectrum hole access strategy Represented as: in, Represents the spectrum hole access strategy set. n Indicates the total number of access policies. b This indicates a specific access policy. u Indicates access policy b A certain user in China; Indicates the first i Under this access strategy, SU has accessed a total of Sub-band ; Indicates the first i Under the first access strategy, the second k The set of users within each sub-band, including A busy-time PU and One access SU; Indicates access policy b Next user u The signal-to-interference-to-noise ratio.

2. The enhanced multiple access method based on CR_NOMA according to claim 1, characterized in that, Access strategy b Next user u Signal-to-interference-to-noise ratio Represented as: in, Indicates access policy b Next user u Transmission power, Indicates access policy b Next user u Normalized channel gain, It is Gaussian white noise. This indicates that all other users in the same frequency band are connected to the user. u The interference value.

3. The enhanced multiple access method based on CR_NOMA according to claim 1 or 2, characterized in that, When the hole PU is activated and reuses the spectrum, the SU is forced to exit unconditionally, relinquishing the right to use the spectrum; after an interval of period T, the SU initiates the next round of sensing requests.

4. An enhanced multiple access method based on CR_NOMA, characterized in that, include: In a cognitive radio network, a secondary user (SU) senses the spectrum status of a primary user (PU) and initiates a spectrum access request to the convergence center (FC). The licensed spectrum is divided into multiple orthogonal sub-bands, and the PUs in a single sub-band share the spectrum in a NOMA (Normally Orthogonal Array) configuration. Only one SU requests access. The FC obtains the set of all spectrum holes at the current moment, and determines the optimal spectrum hole access strategy based on the criterion of minimizing the sum of mutual interference values ​​between the requested SU and all other users in the same frequency band, and feeds it back to the requesting SU. Among all users in the same frequency band, the QoS-based SIC decoding mechanism is used to separate users between PU and SU, and the CSI-based SIC decoding mechanism is used to separate users between PU and PU, and between SU ​​and SU. Each requesting SU communicates using the indicated hole spectrum based on the feedback; user u 1 and users u Mutual interference value between 2 Represented as: in, and Representing users respectively u 1 and users u 2. In access strategy b The channel vector below.

5. The enhanced multiple access method based on CR_NOMA according to claim 4, characterized in that, When the hole PU is activated and reuses the spectrum, the SU is forced to exit unconditionally, relinquishing the right to use the spectrum; after an interval of period T, the SU initiates the next round of sensing requests.

6. An enhanced multiple access system based on CR_NOMA, characterized in that, include: Computer-readable storage media and processors; The computer-readable storage medium is used to store executable instructions; The processor is configured to read executable instructions stored in the computer-readable storage medium and execute the enhanced multiple access method based on CR_NOMA as described in any one of claims 1-3.

7. An enhanced multiple access system based on CR_NOMA, characterized in that, include: Computer-readable storage media and processors; The computer-readable storage medium is used to store executable instructions; The processor is used to read executable instructions stored in the computer-readable storage medium and execute the enhanced multiple access method based on CR_NOMA as described in claim 4 or 5.

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