A D2D communication channel allocation method in ultra-dense scenarios

Abstract

The present invention proposes a D2D communication channel allocation method in an ultra-dense scenario, and the steps are: constructing a D2D communication system model; determining the channel allocation priority according to the QoS requirements and transmission performance of cellular users; cellular users traverse all discrete transmission powers and the maximum number of D2D users that can be reused by the channel; determining the allocation priority of the D2D user; performing D2D user channel allocation, and allocating D2D users to cellular user channels in the order of allocation priority until the allocated D2D users reach the maximum number of D2D users that can be reused by the channel; comparing the system performance benefits, determining the channel allocation scheme and the cellular user power selection; eliminating the D2D users and corresponding channels that have completed the channel allocation, updating the queue, traversing all channels, and outputting the channel allocation result. The present invention can simply and quickly realize the D2D communication channel allocation in an ultra-dense scenario when the number of D2D users is much larger than the number of available channels in the network, and can also improve the access rate of D2D users and the system spectrum efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of mobile communication system resource management, and in particular to a D2D communication channel allocation method in an ultra-dense scenario. Background Art

[0002] With the rapid development of Internet services, the amount of mobile data has exploded, making mobile communication systems face more severe challenges. In the field of industrial Internet of Things, a large number of mobile intelligent terminals represented by intelligent manufacturing, industrial robots, wireless sensor networks, etc. are widely used. In addition, emerging technologies such as networked drones, smart homes, autonomous driving, smart cities, and mobile wearable devices will also be widely used in the next few years. All of the above new applications require mobile communication networks to have higher spectrum efficiency, lower transmission latency, more device connections, and higher transmission energy efficiency. Device-to-device (D2D) communication, as a short-range wireless communication technology, allows users who are close to communicate data directly without forwarding through base stations. Compared with the traditional cellular network technology that relies on uplink and downlink forwarding, D2D communication has the advantages of short transmission distance, small path loss, higher channel gain and faster transmission rate, which makes D2D communication have broad application prospects in responding to the business requirements of future mobile communication networks for high energy efficiency, high spectrum efficiency, high number of node access per unit area, and low latency. It is considered to be one of the key technologies in future mobile communication systems.

[0003] When the number of users waiting to establish data transmission in a mobile communication system is far greater than the number of available channels in a resource pool, that is, an ultra-dense scenario, the base station cannot provide service transmission for most users at this time, and the users waiting to transmit can use D2D communication technology to establish a connection and access the network by reusing the channel resources of existing cellular users. Since the number of D2D users in this ultra-dense scenario is far greater than the number of available channels in the system, a pair of D2D users reuses a cellular user's channel alone, which cannot solve the access rate problem of D2D users. It is necessary to use multiple pairs of D2D users to reuse a cellular user's channel at the same time, that is, a multiple-to-one reuse mode. However, since the ultra-dense scenario makes the cellular user subject to cross-layer interference from multiple different D2D users, the quality of service (QoS) of the cellular user as the main user cannot be guaranteed. Therefore, it is necessary to design a reasonable channel allocation method for D2D users to ensure that the cellular user is not subject to more cross-layer interference, while giving full play to the performance advantages brought by D2D communication, and improving the system spectrum efficiency and the access rate of D2D users. The present invention mainly relates to the research in the field of mobile communication system resource management, and specifically studies a D2D communication channel allocation method in an ultra-dense scenario.

[0004] At present, domestic and foreign scholars have conducted some research on the D2D communication channel allocation method in ultra-dense scenarios. The patent with the authorization number CN 106954269 B proposes a QoS-based cluster channel allocation method. This method first constructs an interference graph between D2D users, uses graph coloring theory to allocate channels for D2D users, and clusters D2D users on this basis. D2D users in the same cluster can share the channels of cellular users. However, this method requires continuous addition of edges to remove the D2D users with the greatest interference during the channel allocation process, which is too computationally intensive in ultra-dense scenarios. In the article "Interference-constrained pricing for D2D networks" published by Yuan Liu in the journal "IEEE Transactions on Wireless Communications" No. 1, Volume 16, the author proposed modeling the D2D communication resource allocation problem in ultra-dense scenarios as a Stackelberg game. Assuming that the base station is the leader of the game, it sets an interference price for each cellular user's channel and publishes it to the D2D users. The D2D users adjust their transmission power on the cellular user channel by observing the interference price of the multiplexed channel. However, the above method is only applicable to flat fading channel environment, and cannot achieve channel allocation in frequency selective channel environment. In the article "Potential Game Resource Allocation Algorithm for High-Density D2D Users" published by Lan Bing in the 43rd volume of the 1st issue of Journal of South China University of Technology (Natural Science Edition), the author proposed to take the total interference received and generated by D2D users as the user's utility function, and use this to construct a game model, and pointed out that the game model is a potential game model, and further pointed out that the potential game will always converge to a Nash equilibrium. Summary of the invention

[0005] In view of the technical problem of large amount of calculation in channel allocation for D2D users in existing ultra-dense scenarios, the purpose of the present invention is to provide a D2D communication channel allocation method in ultra-dense scenarios, which can effectively solve the problem of high complexity of channel allocation calculation while ensuring the QoS requirements of cellular users as primary users, and at the same time improve the access rate of D2D users and the system spectrum efficiency in ultra-dense scenarios.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for allocating D2D communication channels in an ultra-dense scenario comprises the following steps:

[0008] Step 1: Construct a D2D communication system model in an ultra-dense scenario: Set the number of D2D users to be connected to be much larger than the number of cellular users, and the cellular users have discrete transmission power options. Set different channels according to the transmission power options of the cellular users. The maximum number of D2D users that can be multiplexed;

[0009] Step 2: Determine channel allocation priority: Determine channel allocation priority based on QoS requirements and transmission performance of cellular users and the multiplexing interference that cellular users can bear;

[0010] Step 3: The cellular user traverses all discrete transmit powers: According to the order of channel allocation priority in step 2, the cellular user traverses all transmit powers and the maximum number of multiplexable D2D users of the channel;

[0011] Step 4: Determine the allocation priority of D2D users: Determine the allocation priority of D2D users based on the channel gain from the D2D user transmitter to the cellular user transmission receiver;

[0012] Step 5: Execute D2D user channel allocation: According to the determined allocation priority of the D2D user, the cellular user transmission power, and the maximum number of multiplexed D2D users of the channel, the D2D users are allocated to the cellular user channels in the order of allocation priority until the allocated D2D users reach the maximum number of multiplexed D2D users of the channel;

[0013] Step 6: Compare the system performance benefits, determine the channel allocation scheme and cellular user power selection, and select the channel allocation scheme and cellular user power selection that bring the most spectrum efficiency increase;

[0014] Step 7: Remove the D2D users and corresponding channels that have completed channel allocation from the queue to be allocated, update the queue, and loop through steps 2 to 6 until all channels are traversed and the channel allocation result is output.

[0015] The D2D communication system model in step 1 sets discrete transmission powers for cellular users, and sets different maximum numbers of D2D users that can be multiplexed on different channels according to the transmission powers selected by the cellular users.

[0016] The channel allocation constraints of the D2D communication system model in the ultra-dense scenario in step 1 are as follows:

[0017]

[0018] in, is the discrete transmission power used by cellular user i, L is the number of discrete transmission powers that the cellular user can choose, and P l is the lth selectable discrete transmit power, l represents the index of the discrete transmit power, PL is the Lth selectable discrete transmit power, num i,l is the maximum number of D2D users that can be reused by a cellular user, is the minimum number of D2D users multiplexing the same channel. is a rounding function, N is the total number of cellular users, M is the total number of D2D users, and M>>N; is the signal-to-interference-and-noise ratio of cellular user i, The minimum signal-to-interference-noise ratio to meet the QoS requirements of cellular user i, g i,B is the channel gain from cellular user i to the base station, represents the noise power, represents the transmission power of the D2D user j, represents the channel gain from the transmitter of D2D user j to the base station, f(i,j) represents the channel allocation indicator function, C={i|i=1,2,...,N} represents the set of cellular users, and D={j|j=1,2,...,M} represents the set of D2D users.

[0019] In step 2, the channel priority factor is set according to the QoS requirements and transmission performance of the cellular user. in, is the minimum signal-to-interference-noise ratio, channel quality And g i,B is the channel gain from cellular user i to the base station, Represents the noise power.

[0020] Channel priority factor x i Perform the following operations to obtain the priority of channel assignment: Eliminate x i Channel i ≤ 1; x i The smaller the value, the higher the allocation priority of channel i.

[0021] The method for optimizing the channel allocation priority sequence X is: eliminating priority x i ≤1 cellular user i; the remaining cellular users are arranged in ascending order of priority to obtain a new channel allocation priority sequence n represents the number of priority sequences after optimization, is the modified i-th priority.

[0022] In step 4, for cellular user channel i, the base station compares the channel gain of D2D user j to the base station The D2D users are sorted in descending order to determine the allocation priority of D2D user j, that is, a D2D user with a smaller interference channel gain has a higher allocation priority.

[0023] The implementation method of step 5 is: when cellular user i selects the transmission power P 1 When transmitting, according to the allocation priority of the D2D user, find the c with the highest allocation priority size D2D users are assigned to cellular user i; when the cellular user transmits with power P 2 When used as the transmission power, find the 2c with the highest allocation priority size D2D users are assigned to cellular user i, then 2c size D2D users simultaneously reuse the channel of cellular user i; the cycle continues until the cellular user uses the maximum transmission power P L , now find the Lc with the highest priority size D2D users are assigned to cellular user i, then Lc size D2D users simultaneously multiplex the channel of cellular user i.

[0024] In step 6: cellular user i compares the increase in spectrum efficiency brought by all possible channel allocation schemes, selects the D2D user that brings the most spectrum efficiency increase, and determines the corresponding discrete transmission power and channel allocation scheme;

[0025] The increase in spectral efficiency ΔR i The calculation method is:

[0026]

[0027] in, Spectral efficiency when multiplexing cellular user channels for D2D user j, is the difference in spectrum efficiency between cellular user i in non-multiplexing mode and multiplexing mode;

[0028] By comparing all possible discrete transmit power and channel allocation schemes, the optimization problem is solved:

[0029]

[0030] Among them, f * (i,j) and The channel allocation indicator function value f(i,j) and the transmission power are argmax is the optimal value of the independent variable function that makes the function reach the maximum value.

[0031] The spectral efficiency Spectral efficiency difference

[0032] in, is the transmission power of D2D user j, is the signal-to-interference-to-noise ratio of D2D user j, and its expression is:

[0033]

[0034] in, is the channel gain from the transmitter to the receiver when D2D user j multiplexes the channel of cellular user i, h i,j is the channel gain from cellular user i to D2D user j at the receiving end, D i represents the set of D2D users that reuse the same cellular user i channel, m represents other D2D users that reuse the same channel, represents the transmit power of D2D user m, It represents the channel gain received by D2D user j from the transmitting end of other D2D user m that multiplexes the same channel.

[0035] Beneficial effects of the present invention: The present invention can solve the problem of D2D user channel allocation in ultra-dense scenarios. By utilizing a discrete power control method and a method for setting allocation priorities for cellular user channels and D2D users, simple and fast channel allocation is achieved, the computational complexity of channel allocation is reduced, and under the premise of ensuring the QoS requirements of cellular users, performance improvements in aspects such as D2D user access rate and system spectrum efficiency are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 It is a schematic diagram of the process of the present invention.

[0038] Figure 2 Schematic diagram of the D2D communication system model of the present invention.

[0039] Figure 3 It is a comparison curve of system spectrum efficiency performance under different cellular user QoS requirements of the present invention.

[0040] Figure 4 It is a comparison curve of D2D user access rate performance comparison under different cellular user QoS requirements of the present invention.

[0041] Figure 5 It is a comparison curve of the system spectrum efficiency performance under different D2D user densities of the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] like Figure 1 As shown, a D2D communication channel allocation method in an ultra-dense scenario, the steps are as follows:

[0044] Step 1: Construct a D2D communication system model in an ultra-dense scenario. Set the number of D2D users to be connected to be much larger than the number of cellular users, and the cellular users have discrete transmission power options, and set different maximum channel multiplexing D2D user numbers according to the transmission power options of the cellular users.

[0045] Taking the uplink as an example, the D2D communication system model in ultra-dense scenarios is as follows: Figure 2 As shown, the number of D2D users to be accessed is set to be much larger than the number of cellular users. Assume that there are N cellular users and M pairs of D2D users in the uplink of the cellular cell, and M>>N. The sets C={i|i=1,2,...,N} and D={j|j=1,2,...,M} represent cellular users and D2D users respectively. And consider the resource allocation problem under full load, that is, N cellular users occupy all available uplink channel resources, and the channel allocation of cellular users has been completed. At the same time, the spectrum between uplink channels is orthogonal and equally divided, and there is no co-channel interference problem between cellular users. Assume that the channel resources of each cellular user can be reused by multiple pairs of D2D users at the same time, and each pair of D2D users reuses the channel resources of at most one cellular user. Cellular users use discrete transmission power in, is the discrete transmission power used by cellular user i, L is the number of discrete transmission powers that the cellular user can choose, and P l is the lth selectable discrete transmit power, l represents the index of the discrete transmit power, P L is the Lth selectable discrete transmit power.

[0046] According to the number of discrete powers that can be selected by cellular users, the maximum number of D2D users that can be reused on the corresponding channel is set. When cellular users select different fixed powers, in order to suppress the cross-layer interference from D2D users to cellular users and to ensure the QoS requirements of cellular users, the maximum number of D2D users that can be reused by cellular users is limited to different numbers of levels num i,l ∈[c size ,2c size ,…,lc size,…,Lc size ],in, is the minimum number of D2D users multiplexing the same channel. is a round-up function. The channel allocation constraint described by the system model is shown in formula (1):

[0047]

[0048] in, is the signal-to-interference-and-noise ratio of cellular user i, The minimum signal-to-interference-noise ratio to meet the QoS requirements of cellular user i, g i,B is the channel gain from cellular user i to the base station, represents the noise power, represents the transmission power of the D2D user j, represents the channel gain from the transmitter of D2D user j to the base station. f(i,j) represents the channel allocation indicator function, and its construction method is shown in formula (2):

[0049]

[0050] Step 2: Determine channel allocation priority: According to the QoS requirements and transmission performance of cellular users, the channel allocation priority is determined based on the multiplexing interference that the cellular users can bear.

[0051] The cellular user channels that can withstand less multiplexing interference have higher priority, while the cellular user channels that can withstand greater multiplexing interference have lower priority. First, the signal-to-noise ratio of the cellular user is used to represent the channel quality between it and the base station. Channel Quality The construction method of is shown in formula (3):

[0052]

[0053] Secondly, the channel quality Minimum Signal to Interference and Noise Ratio The ratio of i , its construction method is shown in formula (4):

[0054]

[0055] Priorities are set based on the QoS requirements and transmission performance of cellular users; cellular users with high QoS requirements or poor transmission performance have higher priorities.

[0056] Then, the channel priority factor x i To get the priority of channel assignment, do the following:

[0057] 1. Eliminate x i Channel i ≤ 1,

[0058] 2.x i The smaller the value, the higher the allocation priority of channel i.

[0059] Step 3: The cellular user traverses all discrete transmission powers: According to the order of channel allocation priority in step 2, the cellular user traverses all its discrete transmission powers and determines the corresponding maximum number of multiplexable D2D users.

[0060] Assign priority sequence to new channels in turn The cellular users in the traverse all their discrete transmission powers And the corresponding maximum number of multiplexed D2D users num i,l ∈[c size ,2c size ,…,lc size ,…,Lc size ].by For example, at this time, cellular user i selects the transmission power P 1 is its own transmission power, and the corresponding maximum number of D2D users that can be multiplexed on its channel is num i,l =c size and so on.

[0061] Step 4: Determine the allocation priority of D2D users: Determine the allocation priority of D2D users based on the channel gain from the D2D user transmitter to the cellular user transmission receiver.

[0062] Taking cellular user i as an example, the base station compares the channel gain of the D2D user to the base station The D2D users are sorted in descending order, so that the cellular users with poor transmission performance will give priority to D2D users with smaller interference channel gain for channel multiplexing. In addition, in the uplink, the base station acts as the signal receiving end of the cellular user, and the base station obtains No additional signaling overhead is required.

[0063] The allocation priority of D2D users is determined according to the channel gain of the interference link of D2D users to the main user; the higher the channel gain of the interference link to the main user, the lower the priority of D2D users, and vice versa. Setting the priority in this way can make each cellular user channel access as many D2D users as possible while ensuring its own QoS requirements, thereby improving the access rate of D2D users and improving the spectrum efficiency of the system.

[0064] Step 5: Execute D2D user channel allocation: According to the determined allocation priority of D2D users, cellular user transmission power, and the maximum number of multiplexed D2D users of the channel, D2D users are allocated to cellular user channels in the order of allocation priority until the allocated D2D users reach the maximum number of multiplexed D2D users of the channel.

[0065] When cellular user i chooses the transmission power P 1 When transmitting, according to the allocation priority of D2D users, find the c with the highest priority size D2D users are assigned to cellular user i, and c size D2D users simultaneously reuse the channel of cellular user i. Since cellular user i traverses all possible discrete powers, when the cellular user transmits with power P 2 When used as the transmission power, find the 2c with the highest allocation priority size D2D users are assigned to cellular user i, then 2c size D2D users simultaneously reuse the channel of cellular user i. The above operation is repeated until the cellular user uses the maximum transmission power P L , now find the Lc with the highest priority size D2D users are assigned to cellular user i, then Lc size D2D users simultaneously multiplex the channel of cellular user i.

[0066] Step 6: Compare the system performance benefits, determine the channel allocation scheme and cellular user power selection, and select the channel allocation scheme and cellular user power selection that brings the most spectrum efficiency increase.

[0067] The present invention measures the system performance benefit according to the growth of the system spectrum efficiency. The channel allocation and discrete power scheme that brings the highest system performance benefit is selected. Cellular user i compares the spectrum efficiency growth brought by all possible channel allocation schemes, selects the allocation user that brings the most spectrum efficiency growth, and determines the discrete transmission power and channel allocation scheme.

[0068] Increase in spectral efficiency ΔR i It can be calculated using the following method:

[0069]

[0070] in, Spectral efficiency when multiplexing cellular user channels for D2D user j, is the difference in spectrum efficiency between cellular user i in non-multiplexing mode and multiplexing mode. The calculation formulas for the two are as follows:

[0071]

[0072]

[0073] in, is the transmission power of D2D user j, is the signal-to-interference-to-noise ratio of D2D user j, and its calculation formula is as follows:

[0074]

[0075] in, is the channel gain from the transmitter to the receiver when D2D user j multiplexes the channel of cellular user i, h i,j is the channel gain from cellular user i to D2D user j at the receiving end, D i represents the set of D2D users that reuse the same cellular user i channel, m represents other D2D users that reuse the same channel, represents the transmit power of D2D user m, It represents the channel gain received by D2D user j from the transmitting end of other D2D user m that multiplexes the same channel.

[0076] By comparing all possible discrete transmission power and channel allocation schemes, find the channel allocation indicator function value f(i,j) and the transmission power The optimal value of is expressed as follows:

[0077]

[0078] Among them, f * (i,j) and The channel allocation indicator function value f(i,j) and the transmission power are argmax is the optimal value of the independent variable function whose output makes the function reach the maximum value.

[0079] It should be pointed out that the present invention mainly relates to the power control of cellular users and the channel allocation method of D2D users, which does not involve the power control problem of D2D users. The D2D user transmission power selection in the specific implementation mode of the present invention can adopt a fixed transmission power or an existing technology for realizing power control.

[0080] Step 7: Remove the D2D users and corresponding channels that have completed channel allocation from the queue to be allocated, and update the queue. Loop through steps 2 to 6 until all channel allocations are completed. End the operation and output the channel allocation result.

[0081] The beneficial effects of the present invention are further illustrated below in conjunction with specific embodiments.

[0082] Under MATLAB simulation conditions, it is assumed that the simulation environment is a single cell uplink, the base station is located in the center of the cell, and the cell coverage radius is 1 km. All cellular users and D2D user transmitters are randomly distributed at any radius and angle in the cell. At the same time, the D2D user's receiver is randomly distributed at any radius and angle in a circle with the D2D user transmitter as the center and a maximum transmission distance of 100 meters. The discrete transmission power of cellular users is [10, 15, 18, 20, 23] dBm, where dBm is the unit of power. The calculation method is to take 10 times the logarithm of the ratio of the transmission power to 1 milliwatt. The calculation expression is: The maximum transmission power of D2D users is set to 21dBm, and its power control adopts adaptive power control. The number of D2D users is set to 100, the number of cellular users, that is, the number of channels, is set to 20, and the minimum SINR (signal to interference plus noise ratio) requirement of cellular users is set to 0dB~20dB. The channel model is modeled as a frequency selective channel, and the channel gain is modeled as a large-scale path loss model based on the transmission distance and a small-scale fading model caused by multipath transmission and Doppler effect. The path loss model between D2D users is modeled as 148+40lg(d), in dB, where d is the distance between the transmitting user and the receiving user, in kilometers. The path loss model between other users is modeled as 128.1+37.6lg(d), in dB. Small-scale fading is modeled as an exponential distribution with a mean of 1. The noise power is set to -114dBm.

[0083] like Figure 3 and Figure 4 As shown, compared with other existing algorithms, the method of the present invention greatly improves the access rate and spectrum efficiency performance of the D2D communication system in ultra-dense scenarios while ensuring the QoS requirements of cellular users. Among them, the existing algorithm 1 adopts a random channel allocation algorithm that allows multiple D2D users to reuse the same channel resources, and the existing algorithm 2 is a Hungarian allocation algorithm that only allows a single D2D user to reuse the cellular user channel. At the same time, Figure 5 It shows that as the density of D2D users increases, the method of the present invention has more advantages than the existing algorithms, which further proves the superiority of the method of the present invention in ultra-dense D2D communication scenarios.

[0084] The present invention can simultaneously meet the performance requirements of high access rate and high spectrum efficiency of the D2D communication system in ultra-dense scenarios when the number of D2D users to be accessed is far greater than the number of available channels in the network.

[0085] The present invention utilizes a discrete power control method, sets discrete transmission power selection for cellular users, and sets the maximum number of D2D users that can be reused in the channel according to the transmission power of the cellular users; when the cellular users transmit data at a lower transmission power, in order to protect their QoS requirements, the base station will allocate fewer D2D users for channel reuse, and vice versa, more D2D users will be allowed to reuse the channel; then, by using the priority setting, different allocation priorities are set for cellular users and D2D users, respectively, and allocation performance is guaranteed on the basis of reducing the computational complexity. The present invention can solve the D2D user channel allocation problem in ultra-dense scenarios, and achieve beneficial effects in terms of guaranteeing the QoS requirements of the main users, the D2D user access rate, and the system spectrum efficiency. The present invention can solve the D2D user channel allocation problem in ultra-dense scenarios when the number of D2D users is much larger than the number of available channels in the network, realize simple and fast channel allocation, and realize the high access rate of D2D users and the improvement of the system spectrum efficiency; it has a wide range of application value and is of great significance to the field of mobile cellular communication technology resource management.

[0086] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A D2D communication channel allocation method in an ultra-dense scenario, characterized in that: The steps are as follows: Step 1: Build a D2D communication system model in ultra-dense scenarios; Step 2: Determine channel allocation priority: Determine channel allocation priority based on QoS requirements and transmission performance of cellular users and the multiplexing interference that cellular users can bear; Step 3: The cellular user traverses all discrete transmit powers: According to the order of channel allocation priority in step 2, the cellular user traverses all transmit powers and the maximum number of multiplexed D2D users of the channel; Step 4: Determine the allocation priority of D2D users: Determine the allocation priority of D2D users based on the channel gain from the D2D user transmitter to the cellular user transmission receiver; Step 5: Execute D2D user channel allocation: According to the determined allocation priority of the D2D user, the cellular user transmission power, and the maximum number of multiplexed D2D users of the channel, the D2D users are allocated to the cellular user channels in the order of allocation priority until the allocated D2D users reach the maximum number of multiplexed D2D users of the channel; Step 6: Compare system performance benefits and determine channel allocation scheme and cellular user power selection; Step 7: Remove the D2D users and corresponding channels that have completed channel allocation from the queue to be allocated, update the queue, and loop through steps 2 to 6 until all channels are traversed and the channel allocation result is output.

2. The D2D communication channel allocation method in an ultra-dense scenario according to claim 1, characterized in that: The D2D communication system model in step 1 sets discrete transmission powers for cellular users, and sets different maximum numbers of D2D users that can be multiplexed on different channels according to the transmission powers selected by the cellular users.

3. The D2D communication channel allocation method in an ultra-dense scenario according to claim 2, characterized in that: The channel allocation constraints of the D2D communication system model in the ultra-dense scenario in step 1 are as follows: in, is the discrete transmission power used by cellular user i, L is the number of discrete transmission powers that the cellular user can choose, and P l is the lth selectable discrete transmit power, l represents the index of the discrete transmit power, P L is the Lth selectable discrete transmission power, num i,l is the maximum number of D2D users that can be reused by a cellular user, is the minimum number of D2D users multiplexing the same channel. is a rounding function, N is the total number of cellular users, M is the total number of D2D users, and M>>N; is the signal-to-interference-and-noise ratio of cellular user i, The minimum signal-to-interference-noise ratio to meet the QoS requirements of cellular user i, g i,B is the channel gain from cellular user i to the base station, represents the noise power, represents the transmission power of the D2D user j, represents the channel gain from the transmitter of D2D user j to the base station, f(i,j) represents the channel allocation indicator function, C={i|i=1,2,...,N} represents the set of cellular users, and D={j|j=1,2,...,M} represents the set of D2D users.

4. The D2D communication channel allocation method in an ultra-dense scenario according to any one of claims 1 to 3, characterized in that: In step 2, the channel priority factor is set according to the QoS requirements and transmission performance of the cellular user. in, is the minimum signal-to-interference-noise ratio, channel quality And g i,B is the channel gain from cellular user i to the base station, Represents the noise power.

5. The D2D communication channel allocation method in an ultra-dense scenario according to claim 4, characterized in that: Channel priority factor x i Perform the following operations to obtain the priority of channel assignment: Eliminate x i Channel i ≤ 1; x i The smaller the value, the higher the allocation priority of channel i.

6. The D2D communication channel allocation method in an ultra-dense scenario according to claim 5, characterized in that: In step 4, for cellular user channel i, the base station compares the channel gain of D2D user j to the base station The D2D users are sorted in descending order to determine the allocation priority of D2D user j, that is, a D2D user with a smaller interference channel gain has a higher allocation priority.

7. The D2D communication channel allocation method in an ultra-dense scenario according to claim 1 or 6, characterized in that: The implementation method of step 5 is as follows: when cellular user i selects the transmission power P1 to transmit, according to the allocation priority of the D2D user, find the c with the highest allocation priority. size D2D users are assigned to cellular user i; when the cellular user uses the transmission power P2 as the transmission power, find the 2c with the highest allocation priority. size D2D users are assigned to cellular user i, then 2c size D2D users simultaneously reuse the channel of cellular user i; the cycle continues until the cellular user uses the maximum transmission power P L , now find the Lc with the highest priority size D2D users are assigned to cellular user i, then Lc size D2D users simultaneously multiplex the channel of cellular user i.

8. The D2D communication channel allocation method in an ultra-dense scenario according to claim 7, characterized in that: In step 6, the cellular user i compares the increase in spectrum efficiency brought by all possible channel allocation schemes, selects the D2D user that brings the most spectrum efficiency increase, and determines the corresponding discrete transmission power and channel allocation scheme; The increase in spectral efficiency ΔR i The calculation method is: in, Spectral efficiency when multiplexing cellular user channels for D2D user j, is the difference in spectrum efficiency between cellular user i in non-multiplexing mode and multiplexing mode; By comparing all possible discrete transmit power and channel allocation schemes, the optimization problem is solved: Among them, f * (i,j) and The channel allocation indicator function value f(i,j) and the transmission power are argmax is the optimal value of the independent variable function that makes the function reach the maximum value.

9. The D2D communication channel allocation method in an ultra-dense scenario according to claim 8, characterized in that: The spectral efficiency Spectral efficiency difference in, is the transmission power of D2D user j, is the signal-to-interference-to-noise ratio of D2D user j, and its expression is: in, is the channel gain from the transmitter to the receiver when D2D user j multiplexes the channel of cellular user i, h i,j is the channel gain from cellular user i to D2D user j at the receiving end, D i represents the set of D2D users that reuse the same cellular user i channel, m represents other D2D users that reuse the same channel, represents the transmit power of D2D user m, It represents the channel gain received by D2D user j from the transmitting end of other D2D user m that multiplexes the same channel.

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