CN111328052B - Channel resource allocation method in high-density wireless network - Google Patents

Abstract

The invention relates to the field of wireless network communication, in particular to a channel resource allocation method in a high-density wireless network; the method divides a channel into a plurality of sub-channels, namely resource units; dividing the channel into a plurality of stages including an uplink random access stage and an uplink resource allocation stage; in the uplink random access stage, the invention reduces the number of competition stations in the network, namely reduces the network density so as to reduce the conflict, and adjusts the optimal competition window value by maximizing the RU throughput in the uplink random access process so as to improve the MAC efficiency. In the uplink resource allocation stage, the uplink resource allocation efficiency is greatly improved by constructing the maximum independent set, so that the RU resources are multiplexed by the D2D link pairs as many as possible, and the channel resource multiplexing rate is greatly improved. During the uplink data transmission phase, the station and D2D link pair can achieve collision-free data transmission on its allocated RU resources, thereby improving channel utilization and system throughput.

Description

A kind of channel resource allocation method in high-density wireless network

technical field

The present invention relates to the field of wireless network communications, and in particular, to a method for channel resource allocation in a high-density wireless network.

Background technique

Nowadays, wireless communication technology has penetrated into all aspects of people's life and work, playing an increasingly important role. With the rapid development of wireless communication technology, wireless local area network has been widely used in residential, commercial and public services and other fields. Therefore, how to use new technologies to reduce network load, improve channel utilization, and reduce power consumption of user terminals has become the main challenge faced by wireless networks. More recently, the concept of D2D communication has emerged as a potential solution to the spectral efficiency problem in 5G. Thus, two users in close proximity can communicate directly in a simple and fast manner without relying on network infrastructure entities such as APs or base stations. Especially in high-density scenarios, D2D communication can greatly reduce the impact of data services on the network by reusing the resources of cellular users, alleviate the problem of wireless resource constraints, and improve the spectral efficiency of the system.

IEEE 802.11ax is the first Wi-Fi standard that draws on the Orthogonal Frequency Division Multiple Access (OFDMA) technology adopted by cellular networks. OFDMA divides the sub-carriers of all bandwidths in a WLAN into several sub-channels or RUs. Among them, the Wi-Fi channels of 20MHz, 40MHz, 80MHz and 160MHz can be divided into 9, 18, 37 and 74 RU resources respectively. Based on this, multiple sites can access different RUs at the same time to realize multi-user concurrent transmission. IEEE 802.11ax channel access includes two mechanisms: scheduled access and random access. In the scheduling access mode, after the AP receives a Buffer Status Report (BSR) frame from a station through a random access mechanism, it allocates RUs to users in a pre-defined manner. In the scheduling access mode, the data of the scheduling station can be transmitted without collision. However, due to the traditional random access mechanism, conflicts in the network are inevitable. Especially in high-density networks, a large number of sites competing for channels will lead to higher collisions, which will significantly reduce network performance.

SUMMARY OF THE INVENTION

Based on the problems existing in the prior art, the present invention is inspired by the D2D communication in the traditional cellular network, and introduces the D2D concept into the Wi-Fi network, which will greatly improve the network performance. In a Wi-Fi network, when some devices are located very close in space and the quality of the communication signal with the AP is poor, the use of D2D communication technology can improve the spectral efficiency and reduce the load on the AP. Therefore, it is of great significance to learn from and improve the D2D communication resource allocation algorithm suitable for the cellular network mode of 802.11ax.

The technical scheme adopted by the present invention to solve the above-mentioned technical problems includes:

In a first aspect of the present invention, a method for allocating channel resources in a high-density wireless network includes:

Divide the channel into multiple sub-channels, namely resource units; divide the channel into multiple stages, including the uplink random access stage and the uplink resource allocation stage; and divide the sites into D2D sites and non-D2D sites, namely Wi-Fi sites;

In the uplink random access phase, non-D2D stations, namely Wi-Fi stations, use the backoff mechanism to randomly access resource units and send BSR frames to compete for channel resources; when the number of stations successfully competing for resource units is greater than or equal to the number of RUs, or when the uplink When the cycle is reached,

Entering the uplink resource allocation stage, the AP models the interference relationship between D2D link pairs as an interference graph according to the pre-established D2D link pair information, and generates multiple maximum independent sets of MIS information including all D2D link pairs. and the interference relationship matrix LRSD between Wi-Fi sites and all D2D link pairs; the AP allocates RU resources to the Wi-Fi sites that successfully compete for the channel in turn, and according to the maximum independent set information and the interference relationship matrix information Allocate non-interfering D2D link pairs for each RU.

In the second aspect of the present invention, the present invention also provides a channel resource allocation method in a high-density wireless network suitable for data transmission, including:

Divide the channel into multiple resource units RU; and divide the channel into multiple phases, including uplink random access phase, uplink resource allocation phase and uplink data transmission phase;

In the uplink random access phase, non-D2D stations use the backoff mechanism to randomly access resource units and send BSR frames to compete for channel resources; when the number of stations that successfully compete for resource units is greater than or equal to the number of RUs, or when the uplink period is reached,

Entering the uplink resource allocation stage, the AP abstracts the interference relationship between D2D link pairs into an interference graph according to the pre-established D2D link pair information, and generates the maximum independent set information MIS containing all D2D link pairs, as well as site and The interference relationship matrix LRSD between all D2D link pairs; the AP allocates RU resources (channel resources) to the stations that successfully compete for the channel in turn, and allocates each RU according to the maximum independent set information and the interference relationship matrix information Interference-free D2D link pair;

In the uplink data transmission stage, the station and the D2D link perform conflict-free data transmission according to the resource allocation result in the TF frame.

Beneficial effects of the present invention:

In the uplink random access stage, the present invention reduces the number of contending sites in the network, that is, reduces the network density, thereby reducing the conflict, and in addition, adjusts the optimal contention window value by maximizing the RU (sub-channel) throughput of the uplink random access process, This improves the MAC efficiency. In the uplink resource allocation stage, by referring to the concept and characteristics of the largest independent set, the efficiency of uplink resource allocation is greatly improved, so that as many D2D link pairs as possible can reuse RU (sub-channel) resources, which greatly improves the channel resource reuse. Rate. In the uplink data transmission phase, the station and the D2D link pair can achieve conflict-free data transmission on their allocated RU resources, thereby improving channel utilization and system throughput.

Description of drawings

1 is an example of a network topology diagram provided by an embodiment of the present invention;

Fig. 2 is the overall structure diagram of the present invention;

3 is an example of an uplink access mechanism of the present invention;

FIG. 4 is a channel state description in the time domain according to an embodiment of the present invention;

Fig. 5 is the interference graph modeling process diagram of the D2D communication pair provided by the embodiment of the present invention;

Figure 5 (a) is a network topology diagram provided by the present invention; Figure 5 (b) is a schematic diagram of interference provided by the present invention; Figure 5 (c) is an interference diagram provided by the present invention;

Fig. 6 is the resource allocation flow chart of the present invention;

FIG. 7 is an example diagram of allocating RU resources to a D2D link pair according to the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and Not all examples.

A channel resource allocation method in a high-density wireless network proposed by the present invention mainly includes the following contents: uplink random access and uplink resource allocation in two stages, as well as the modeling of D2D link-to-interference graph and the generation of the maximum independent set and its update process.

Figure 1 shows a network architecture diagram of an embodiment of the present invention. The wireless access point AP is deployed in the geometric center of the basic service set BSS, and all sites (Wi-Fi sites and D2D link pairs, namely D2D sites) are randomly distributed in the AP's coverage area. Suppose there are m Wi-Fi stations and n D2D link pairs in the network under study, where Am represents the stations communicating through the Wi-Fi infrastructure, m = 1, 2, ..., m; Dn represents the direct D2D link of communication link conditions, n=1,2,...,n. Therefore, the present invention uses A={A1, A2,...,Am} and D={D1, D2,...,Dn} to represent the Wi-Fi station set and the D2D link pair set, respectively. In addition, IEEE 802.11ax adopts OFDMA technology in uplink transmission, which divides the entire channel into r RUs (resource units or sub-channels) to support simultaneous transmission by multiple users at low data rates. Therefore, the channel resource can be expressed as R={RU1, RU2, .

Based on the above-mentioned network architecture diagram, the main idea of the present invention is as follows:

i) According to the information of each station in the network, the AP establishes a D2D link pair for the stations that meet the link establishment conditions, and resets the power of the D2D link pair to minimize interference.

ii) Abstract the D2D link pair as an interference graph.

iii) Based on the generated interference map, a series of maximal independent sets are further generated and updated.

iv) The AP can schedule D2D link pairs belonging to the same MIS to multiplex the same RU, which avoids interference between D2D link pairs while ensuring higher resource multiplexing.

It can be understood that, in the present invention, if not explicitly referred to, the site generally refers to a Wi-Fi site, and only when no D2D site is selected, the site refers to all sites including Wi-Fi sites and D2D sites.

In one embodiment, a method for channel resource allocation in a high-density wireless network includes an uplink random access phase and an uplink resource allocation phase.

In another embodiment, the present invention also provides a channel resource allocation method in a high-density wireless network suitable for data transmission, including an uplink random access phase, an uplink resource allocation phase, and an uplink data transmission phase.

FIG. 2 shows the overall structure diagram of the present invention, which mainly includes three stages: uplink random access stage, uplink resource allocation stage and uplink data transmission stage.

Before the uplink random access phase, the entire channel is preferentially divided into multiple RUs; the uplink random access phase consists of multiple backoff phases. In order to improve spectrum utilization, stations perform double backoff in time domain and frequency domain to participate in medium competition. In addition, combined with the centralized control feature of the IEEE 802.11ax MAC layer, the embodiment of the present invention adjusts the optimal contention window by maximizing the RU throughput in the uplink random access process, thereby optimizing the MAC layer efficiency, that is, maximizing the RU throughput as the objective function to calculate the optimal contention window CW* value.

Figure 3 shows the back-off mechanism of the site in the process of uplink random access. The detailed process is as follows:

Step 1: The AP announces the optimal contention window value CW* value and the number r of available RUs in its Trigger Frame for Random Access (TF-R) frame.

Step 2: If the Wi-Fi station has data to send, it will randomly select a value from [0, CW*] as its OFDMA backoff count (OFDMA Backoff, OBO).

Step 3: The Wi-Fi station executes the backoff phase, and judges whether the backoff count OBO in the backoff phase is greater than 0. If it is greater than 0, the backoff count OBO in the backoff phase is decreased by r; otherwise, step 4 is performed;

Step 4: The Wi-Fi station will randomly select a RU from the r available RU resources and send its BSR frame to the AP; and reset the OBO value of the Wi-Fi station to CW*; that is, the Wi-Fi station is in This round of random access phase will no longer participate in medium competition;

Step 5: If the AP successfully receives BSR frames from Wi-Fi sites, it records the information of these Wi-Fi sites; when the number of Wi-Fi sites that successfully compete for RUs is greater than or equal to the number of RUs, the AP will send TF frames Notify the end of the uplink random access phase, otherwise enter the next backoff phase, and execute step 3.

Therefore, in the uplink random access stage, this embodiment accesses the channel through double backoff in the time domain and frequency domain, and optimizes the MAC efficiency based on maximizing resource unit (Resource Unit, RU) throughput as the objective function. The back-off mechanism proposed by the present invention can not only reduce conflicts by offloading nodes in the network to the D2D communication mode, but also improve MAC efficiency by optimizing the contention window (CW) value of each random access stage.

Relevant literature points out that optimizing the period of the uplink random access phase can obtain higher throughput, that is, by setting the optimal MAC parameters, the maximum throughput can be achieved in the uplink random access phase. Therefore, in this embodiment of the present invention, the optimal CW value is obtained by establishing the objective of maximizing the RU throughput. The theoretical model is as follows:

Let τ be the probability that a Wi-Fi station tries to randomly select a RU to send a packet at a random slot time, which can be expressed as formula (1).

Wherein, CW is the contention window in the uplink random access phase. CW also represents the uplink random access period and the backoff value of the AP, and r is the number of available RU resources. Ptr represents the transmission probability on a random RU in a random time slot, that is, the probability that at least one station is transmitting data in the considered RU, then Ptr is:

Ptr=1-(1-τ) ⁿ (2)

Pi is used to represent the probability when there is no station in the considered RU for data transmission, that is, the idle probability, then Pi is:

Pi=(1-τ) ⁿ (3)

Ps is used to indicate the success probability of selecting a random RU to transmit data in a random time slot, that is, only one station in the same time domain on the RU transmits data. Then the successful transmission probability Ps can be calculated by formula (4).

Similarly, the probability of collision on randomly selected RUs on random slots is Pc= _Ptr -PS. Therefore, the throughput SRU on each _RU can be calculated by Equation (5).

where E[p] represents the average length of the transmitted data packets. Ts and Tc are the average time for successful transmission and collision, respectively. _Ti channel idle time. Assuming that Ts is equal to Tc, its expression is as formula (6).

Tc=Ts=T _BSR +2*T _SIFS (6)

Among them, T _BSR represents the average time for successfully sending a BSR frame. T _SIFS is the short frame interval time. Therefore, bringing the above formula into formula (5), S _RU can be rewritten as:

To maximize the RU throughput in Equation (7), and since E[P] is constant, Equation (8) needs only to be maximized.

For a given n, there is an optimal CW that maximizes the throughput of the RU. To find CW*, the partial derivative of equation (8) with respect to τ needs to be calculated, where τ is a function of CW. Equation (9) gives the corresponding expression.

where k=Tc/Ti. Using the relevant simplification rules, equation (10) approximately derives an expression for τ.

Therefore, by substituting the τ value of formula (10) into formula (1), the approximate relationship between the optimal CW value and the number of stations can be obtained:

The present invention allows multiple users to transmit in parallel, where the number of available RUs is r. Therefore, the system throughput can be calculated by CW* derived from equation (11), then S is:

Among them, Ps' and Pi' are the probability of successful transmission and the probability of idle, respectively. The station adopts dual backoff mechanism in frequency domain and time domain, and adopts traditional backoff mechanism in time domain, then Ps' and Pi' are respectively:

Finally, the above related formula is brought into formula (7), and formula (12) is rewritten, the system throughput expression is shown in formula (15).

For ease of understanding, FIG. 4 is used to further illustrate the three channel states in the time domain, namely idle, successful transmission and collision.

In the uplink resource allocation phase, in order to avoid wasting channel utilization, the AP can schedule downlink transmissions at the same time. The goal of uplink resource allocation is to make the resource allocation algorithm simple and efficient. In the implementation of the present invention, the resource allocation model is mainly divided into three stages: modeling of D2D interference graph, generation of maximum independent set and resource allocation decision, as shown in FIG. 5 .

Sub-Phase 1: Modeling of D2D Interference Graphs

The first sub-phase of the uplink resource allocation phase is to construct an interference map according to the interference relationship of the D2D link pair. Figure 5 shows the process of modeling the network topology of the D2D link pair in the network as a corresponding interference graph, denoted by G=<V, E>. As shown in Figure 5(a), the network structure is centered on the AP, surrounded by multiple D2D link pairs; represented by D1, D2, ..., D12 respectively; the vertices in the set V represent D2D communication link pairs , so represented by D1, D2, ..., D12, while the elements in the edge set E represent the interference relationship between D2D pairs. The interference relationship is defined by the SINR values at the receivers of the two links. Figure 5(b) shows the case of interference when D2D1 and D2D2 use the same RU for data transmission. Figure 5(c) shows the interference diagram after modeling the interference relationship of the D2D link pair; among them, S1 (transmitter 1) to R1 (receive end 1) and S2 (transmitter 2) to R2 (receive end 1) The communication link of end 2) will cause two interfering links from S2 to R1 and S1 to R2, respectively. If the SINR of the receiving end of any link is less than the SINR threshold, it is considered that there is an interference relationship between the two communication links. The instantaneous SINR at the receiver is shown in Equation (16).

In the formula, P _D is the transmit power of the D2D communication device, β is the SINR threshold, and α _N→D is the path loss of the D2D communication link from the sender to the destination, which can be expressed by formula (17).

where ρ is the distance of the D2D communication link pair and λ is the wavelength of visible light in the ideal free-space transmission model.

In addition, once the D2D link is established, the transmit power of the D2D communication link is adjusted according to the maximum interference distance of the D2D communication pair to further reduce the interference between the D2D link pair and between the D2D link pair and the STA.

Sub-stage 2: Generate the largest independent set

In view of the implementation of the present invention, the goal is to find the best RU multiplexing scheme for D2D link pairs to maximize network performance. Therefore, the implementation of the present invention draws on the concept and characteristics of MIS in graph theory, that is, there is no neighbor relationship between any two nodes in the same MIS, which means that nodes in the same MIS can transmit data simultaneously without interfering with each other. Therefore, according to the D2D interference graph G<V, E> as described above, the D2D link pairs are divided into different MIS according to their interference relationship. Let S = [S1, S2, S3, . Sk stores the ID of the D2D link pair in the kth MIS. In addition, NR(n×n)=[NR _i,j ] is used to represent the interference relationship between D2D link pairs, and the value of nr _i,j (i, j∈n) is expressed as:

Sub-phase three: resource allocation

When the uplink random access phase ends. The AP will allocate RUs to stations and D2D link pairs based on the generated maximum independent set and the interference relationship between stations and D2D link pairs. Similarly, let LRSD=[l _ri,j ] denote the interference relationship of STA and D2D link pair, where i∈m, j∈n. Therefore, lr _i,j can be expressed as

The main contribution of the embodiments of the present invention is to achieve efficient RU resource allocation. The core idea is to ensure that the sites competing for the RU can successfully transmit data, and at the same time, schedule non-interfering D2D link pairs to multiplex non-interfering RU resources to achieve the same RU Parallel transfers on resources. Therefore, based on MIS and LRSD information, not only the goal of resource reuse can be achieved, but also the efficiency of resource allocation can be improved.

FIG. 6 shows a flowchart of uplink resource allocation. This embodiment describes that the AP performs resource allocation based on the information of the sites that successfully compete for channel resources, the generated maximum independent set information, and the interference relationship between the sites and the D2D link pair. Distribution process flow, the method includes:

Step 1: The AP obtains the interference relationship matrix information of the Wi-Fi sites competing for RU resources;

Step 2: The AP allocates RU resources to the Wi-Fi stations competing for the channel in turn, and initializes the RU index i=1;

Step 3: Match the interference relationship matrix of the Wi-Fi site competing for the i-th RU resource with the largest independent set with the most elements;

Step 4: Determine whether there is no interference between the D2D link and the site in the current maximum independent set, if there is no interference, go to Step 5; otherwise, go to Step 6;

Step 5: Allocate the i-th RU to a non-interfering D2D link, delete the D2D link that has been allocated to the RU from the maximum independent set, and update the maximum independent set;

Step 6: Match the interference relationship matrix of the Wi-Fi site with the remaining maximum independent set with the largest number of elements;

Step 7: Determine whether all RU allocations are completed or all maximum independent sets are empty, if the allocation is completed or the maximum independent sets are empty, set i=i+1, return to step 2, otherwise end the process.

Wherein, in this embodiment, D2D link pairs belonging to the same MIS can reuse the same RU resources or subchannels, but it is required that there is no interference between these D2D link pairs and the Wi-Fi site occupying the RU. When the AP allocates a D2D link pair for each RU or there is no D2D link pair and no RU is allocated, the uplink resource allocation phase ends.

Figure 7 shows an example in resource allocation. In each resource allocation sub-phase, the AP will allocate reusable D2D link pairs to each RU based on S_STA (storing Wi-Fi stations that successfully compete for RU resources) and LRSD information. For example, when i is equal to 1, the AP allocates the channel resource RU1 to S_STA(i), assuming that the Wi-Fi station is STA1. Therefore, the AP obtains the maximum independent set information from S(1) and the interference relationship matrix between STA1 and the D2D link pair, LRSD(STA1)=[1, 1, 0, 0, 1, 1, 0, 1] , where the number of elements in LRSD is equal to the number of D2D link pairs. Then, AP matches LRSD(STA1) and S(1), and finally stores the result in DR(i) and updates S.

In one embodiment, in the uplink data transmission stage, the operations performed include:

In the uplink data transmission phase, the AP sends a TF frame, and the Wi-F station and D2D link pair that receive the frame perform conflict-free data on the RUs allocated to them according to the resource allocation information contained in the frame. Transmission, when the AP successfully receives the data sent by the station, the AP will reply a multiuser block acknowledgment (multiuser block ACK, referred to as MBA) frame.

It may also include that the station and the D2D link pair perform conflict-free data transmission on their available RUs according to the information in the TF frame sent by the AP. Assuming that the uplink data transmission period is TXOP, these stations and D2D link pairs can transmit data during a given TXOP period. After receiving a packet from a station, the AP will reply to the station using a multi-block acknowledgment mechanism.

Those of ordinary skill in the art can understand that all or part of the steps in the various methods of the above embodiments can be completed by instructing relevant hardware through a program, and the program can be stored in a computer-readable storage medium, and the storage medium can include: ROM, RAM, magnetic disk or optical disk, etc.; in addition, the channel resource allocation algorithm of the present invention is not only limited to allocating RU resources but also applicable to allocating sub-channel resources.

The above-mentioned embodiments further describe the purpose, technical solutions and advantages of the present invention in detail. It should be understood that the above-mentioned embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made to the present invention within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (7)

1. A method for allocating channel resources in a high-density wireless network is characterized by comprising the following steps:

dividing a channel into a plurality of subchannels, namely resource units; dividing the channel into a plurality of stages including an uplink random access stage and an uplink resource allocation stage;

in an uplink random access stage, a non-D2D station, namely a Wi-Fi station, randomly accesses a resource unit by adopting a backoff mechanism and sends a BSR frame to compete for channel resources; when the number of Wi-Fi stations successfully contending for the resource unit is greater than or equal to the number of RUs, or when an uplink period is reached,

entering an uplink resource allocation stage, modeling an interference relationship between D2D link pairs, namely D2D stations, as an interference graph by the AP according to pre-established D2D link pair information, and generating a plurality of maximum independent set MIS information containing all D2D link pairs and an interference relationship matrix LRSD between the Wi-Fi stations and all D2D link pairs; the AP allocates RU resources to the Wi-Fi stations which successfully compete to the channel in sequence, and allocates an interference-free D2D link pair to each RU according to the maximum independent set information and the interference relationship matrix information;

the modeling process of the interference graph comprises that a network topology structure is formed by taking an AP as a center and covering a plurality of D2D link pairs around the AP; representing the D2D link pairs by a vertex set V and representing the interference relationship between the D2D link pairs by an edge set E to form an interference graph G < V, E >; the interference relationship is defined by SINR values of receiving ends of two links; if the SINR of the receiving end of any link is smaller than the SINR threshold, the interference relationship between the two communication links is considered to exist;

the process of generating multiple maximum independent sets MIS information containing all D2D link pairs includes generating a maximum independent set MIS information from an interference graph G<V，E>Dividing the D2D link pair into different MIS according to the interference relation; with S ═ S1, S2, S3, …, Sk]K most independent sets representing updated interference maps, where k is variable, different interference maps corresponding to different k; sk stores the ID of the D2D link pair in the kth MIS; by NR (nxn) ═ NR_i，j]To represent the interference relationship between the D2D link pair, when there is an interference relationship between the D2D link pair i and the D2D link pair j, nr is the interference relationship between the link pair i and the link pair j_i,j1, otherwise nr_i,j＝0；

The process that the AP allocates RU resources to the Wi-Fi stations which successfully compete to the channel in sequence comprises the step that when the uplink random access stage is finished; the AP will assign RUs to station and D2D link pair, let LRSD ═ l, according to the generated maximum independent set and interference relationship of station and D2D link pair_ri,j]Representing a STA and D2D link pairWhen there is an interference relationship between site i and D2D link pair j, then lr_i,j1, otherwise lr_i,j＝0；

The process of allocating a non-interfering D2D link pair to each RU according to the maximum independent set information and the interference relationship matrix information includes:

step 1: the AP acquires interference relationship matrix information of Wi-Fi stations competing to RU resources;

step 2: the AP sequentially allocates RU resources to Wi-Fi stations competing to a channel, and initializes RU indexes i to 1;

and step 3: matching the interference relation matrix of the Wi-Fi site competing to the ith RU resource with the maximum independent set with the most elements;

and 4, step 4: judging whether interference does not exist between the D2D link and the site in the current maximum independent set, and if interference does not exist, performing step 5; otherwise, performing step 6;

and 5: assigning the ith RU to a non-interfering D2D link, removing the D2D link that has been assigned to the RU from the maximum independent set, and updating the maximum independent set;

step 6: matching the interference relation matrix of the Wi-Fi site with the maximum independent set with the most elements in the remaining maximum independent sets;

and 7: and (3) judging whether all RU allocation is completed or all the maximum independent sets are empty, if so, making i equal to i +1, returning to the step (2), otherwise, ending the flow.

2. The method of claim 1, wherein the back-off mechanism comprises:

step 1: the AP publishes an optimal contention window value CW and an available RU number R in a random access trigger TF-R frame;

step 2: if the Wi-Fi station needs to send data, a value is randomly selected from a contention window [0, CW ] to serve as a backoff count OBO of the Wi-Fi station;

and step 3: the Wi-Fi station executes a backoff stage, judges whether a backoff count OBO in the backoff stage is greater than 0, and reduces the backoff count OBO of the backoff stage by r if the backoff count OBO is greater than 0; otherwise, executing step 4;

and 4, step 4: the Wi-Fi station randomly selects one RU from r available RU resources and sends a BSR frame of the RU to the AP; resetting the OBO value of the Wi-Fi station to CW; namely, the Wi-Fi station does not participate in medium competition any more in the current round of uplink random access stage;

and 5: if the AP successfully receives the BSR frame from the Wi-Fi sites, recording the information of the Wi-Fi sites; and when the number of the Wi-Fi stations successfully contending to the RU is larger than or equal to the number of the RUs, the AP sends a TF frame to inform the end of the uplink random access phase, otherwise, the AP enters the next backoff phase, and the step 3 is executed.

3. The method of claim 2, wherein the contention window value is calculated by maximizing the throughput of the RUs as an objective function to calculate an optimal contention window value, such that the throughput S per RU is the maximum_RUExpressed as:

wherein, T_iIndicating the average time of occurrence of the collision; t is a unit of_cRepresents the average time that the channel is idle; e [ P ]]Is the average packet length; n represents the number of Wi-Fi sites; tau represents the probability of sending data packets in randomly selected RUs at random time slot of the Wi-Fi station; CW denotes a contention window value.

4. A method for allocating channel resources in a high-density wireless network according to claim 3, wherein τ is calculated by calculating a partial derivative of throughput in each RU with respect to τ, and extracting τ in an approximately derived manner; the calculation formula is expressed as:

wherein k is Tc/Ti.

5. The method of claim 1, wherein the interference relationship matrix between the station and all D2D link pairs is generated by constructing an interference graph according to D2D link pairs and their interference relationships; judging whether the SINR between any Wi-Fi station and the D2D link to the receiving end is smaller than an SINR threshold value, if so, determining that an interference relationship exists between the two links; forming interference relation matrix information LRSD (lrr) between the Wi-Fi station and the D2D link pair according to the interference relation_i,j]Wherein, lr_i,jRepresents the interference relationship between Wi-Fi station i and D2D link pair j, lr_i,j1 represents that an interference relationship exists between the Wi-Fi station i and the D2D link pair j; lr of_i,j0 means that there is no interference relationship between Wi-Fi station i and D2D link pair j.

6. The method as claimed in claim 1, wherein the channel is further divided into an uplink data transmission phase, and in the uplink data transmission phase, the station and the D2D link perform collision-free data transmission according to the resource allocation result in the TF frame.

7. The method as claimed in claim 6, wherein the operation performed in the uplink data transmission phase includes the AP sending a TF frame, the Wi-Fi station and the D2D link receiving the TF frame performing collision-free data transmission on its allocated RU according to the resource allocation information contained in the frame, and the AP replying a multi-user block acknowledgement MBA after the AP successfully receives the data sent by the station.

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