CN109756375B - Conflict-free link scheduling method for independent multi-channel TDMA network - Google Patents
Conflict-free link scheduling method for independent multi-channel TDMA network Download PDFInfo
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Abstract
The invention provides a conflict-free link scheduling method for an independent multi-channel TDMA network, which comprises the following steps: 1. creating an independent multi-channel TDMA network model; 2. acquiring a conflict graph of an independent multi-channel TDMA network model; 3. acquiring a complementary graph of the conflict graph; 4. numbering the nodes in the complementary graph again; 5. acquiring a new complementary graph; 6. judging whether the new supplementary image is an empty image, if so, executing a step 7, otherwise, replacing the original supplementary image with the new supplementary image, and executing a step 4; 7. each maximum clique in the set of maximum cliques is assigned a channel frequency. The invention ensures the network capacity, simultaneously expends smaller calculation amount, reduces the time complexity of independent multi-channel TDMA network link scheduling, re-numbers the nodes in the complementary graph, optimizes the deep search sequence of the nodes of a backtracking method, reduces the time for finding the maximum cluster, and further reduces the time complexity of independent multi-channel TDMA network link scheduling.
Description
Technical Field
The invention relates to the technical field of communication, in particular to a conflict-free link scheduling method for an independent multi-channel TDMA network, which can be used for high-efficiency transmission of information in the multi-channel TDMA network.
Background
Time division multiple access (tdma) is a communication technology for realizing a shared transmission medium, and is generally used in the field of wireless communication. It allows multiple users to use the same frequency in different time slices, with the users transmitting quickly one after the other, each using their own time slice.
The traditional TDMA network uses a single channel, and the half-duplex working mode of the nodes causes that the nodes cannot receive and send information simultaneously, so that the load of the transit nodes is heavier than that of other nodes. And because the receiving and sending frequencies of all nodes are the same, the nodes in two hops and within two hops can not send in the same time slot, and the sending conflict is more. With the increase of the hop count, the transmission delay of the data is also obviously increased, and the throughput of the network is sharply reduced. Therefore, by using a plurality of completely independent channels, the nodes can work in a full-duplex mode, the forwarding capability of the transit nodes is improved, the conflict in the same time slot network is reduced, the utilization rate of the time slot is increased, and the throughput of the network is greatly improved.
One of the most important problems in multi-channel TDMA networks is the link scheduling problem. The essence of independent multi-channel TDMA network link scheduling is to allocate appropriate time slots and frequency resources to links in the network to achieve the purpose of efficient data transmission, while the conflict-free independent multi-channel TDMA network link scheduling is to reasonably allocate the resources on the premise of eliminating link interference. The purpose of collision-free independent multi-channel TDMA network link scheduling is to find out the links which do not interfere with each other and allocate the same time slot and frequency for the links.
Independent multi-channel TDMA network link scheduling aims to find out non-interfering links in a network, and the problem of link coexistence can be solved by the maximum clique problem of a graph. The maximum group problem of the graph is an NP complete problem, a solving method is divided into an accuracy method and an heuristic method, the accuracy method can theoretically guarantee that the optimal solution is obtained, but the time exponentially rises along with the scale; heuristic methods can find an approximate solution in a short time, but this approximate solution is not necessarily the optimal solution. For the independent multi-channel TDMA network link scheduling problem, an optimal solution capable of coexisting links needs to be found, so that an accurate algorithm needs to be adopted, and therefore how to reduce the time complexity of the algorithm is an important problem.
The independent multi-channel TDMA network link scheduling method is divided into three categories: the independent multi-channel TDMA network link scheduling method based on dynamic channel assignment, the independent multi-channel TDMA network link scheduling method based on dynamic channel and static channel mixed assignment and the independent multi-channel TDMA network link scheduling method based on static channel assignment. In the independent multi-channel TDMA network link scheduling method based on dynamic channel assignment, nodes realize dynamic switching of channels by exchanging control information packets, but the efficiency is reduced by switching channels too frequently; the independent multi-channel TDMA network link scheduling method based on the mixed assignment of the dynamic channel and the static channel firstly adopts the static assignment and adopts the dynamic adjustment when the communication quality is reduced, and the method has higher difficulty and is difficult to realize.
At present, a method based on static channel assignment is mostly adopted for realizing link scheduling of an independent multi-channel TDMA network, which means that once channel assignment is completed, a communication channel of a node cannot be changed in the whole process, the method is simple and easy to realize, the problem of efficiency reduction caused by frequent switching of channels is avoided, and the problem of difficulty in realization caused by mixed assignment of channels is avoided, but the method mainly focuses on better solving the problem of link conflict, and usually cannot better optimize network capacity, for example, Chinese patent with an authorization publication number of CN102427592B and named as a centralized link scheduling method for a multi-channel wireless network discloses a method for centralized link scheduling of multi-channel. The method comprises the steps of numbering links in a network topological graph, obtaining a corresponding network conflict graph from the network topological graph, obtaining a maximum independent set sequence and a maximum cluster sequence of the network conflict graph according to the network conflict graph, obtaining the weight of each maximum independent set according to the maximum cluster sequence, and finally arranging the links in the maximum independent sets to be transmitted in different channels according to the weights. The method can improve the network capacity, but the calculated weight of the maximum independent set of the conflict graph only determines the sequence of the independent multi-channel TDMA network link scheduling, and does not bring substantial optimization to the result of the independent multi-channel TDMA network link scheduling, and along with the increase of the network scale, the calculation amount of the weight of the maximum independent set of the conflict graph can be gradually increased, so that the time complexity is increased.
Disclosure of Invention
The present invention is directed to overcome the above disadvantages of the prior art, and to provide a conflict-free link scheduling method for an independent multi-channel TDMA network, which is used to solve the technical problem of the prior art that the time complexity is large.
The technical idea of the invention is as follows: firstly, creating an independent multi-channel TDMA network model, acquiring a conflict graph of the independent multi-channel TDMA network model, acquiring a complementary graph corresponding to the conflict graph, then numbering nodes in the complementary graph again, then acquiring a new complementary graph and judging whether the new complementary graph is empty, if so, allocating channel frequency for each maximum group in the maximum group set, otherwise, re-numbering the nodes in the complementary graph and performing the subsequent steps again until allocating channel frequency for each maximum group in the maximum group set.
According to the technical idea, the technical scheme adopted for achieving the purpose of the invention comprises the following steps:
(1) creating an independent multi-channel TDMA network model:
(1a) creating an independent multi-channel TDMA network model comprising a node set N, an edge set E and a channel frequency set F, wherein N is {1,2, …, k, … N }, k represents the serial number of the node, N represents the total number of the node, and N is more than or equal to 2; e ═ E1，2，e2，1，…，ep，q，eq，p，…，es，t，et，s}，p≠q，s≠t，ep，qAnd eq，pRespectively representing directed edges with a starting point of a node p and an end point of a node q, and directed edges with a starting point of a node q and an end point of a node p, wherein the number of the directed edges is x, and x is more than or equal to 2 and less than or equal to n (n-1); f ═ F1，f2，…，fl，…，fm}，flRepresents the l-th channel frequency, m represents the total number of the channel frequencies, and m is more than or equal to 2;
(1b) defining the intersected directed edges in the E as directed edges with main conflicts, wherein the intersected directed edges in the E are not intersected but are intersected with a third edge at the same time, and the starting point and the end point of the third directed edge are respectively the starting point of one directed edge and the end point of the other directed edge, so that the two directed edges are directed edges with secondary conflicts;
(2) obtaining a conflict graph G of an independent multi-channel TDMA network model:
(2a) setting a node set V with the number of nodes equal to the number x of directed edges in the set E, at least having a maximum clique set MS of a maximum clique, and emptying the set V and the set MS;
(2b) each directed edge E in the set Ep，qMapping to the nodes in the set V to obtain a node set V':
(2c) connecting nodes corresponding to all the directed edges with main conflicts in the set E in the set V 'through solid lines, simultaneously connecting nodes corresponding to all the directed edges with secondary conflicts in the set E through solid lines, and numbering each node in the set V' in an increasing mode according to a natural number set to obtain a conflict graph G of the independent multi-channel TDMA network model;
(3) acquiring a complement G' of the conflict graph G:
connecting nodes corresponding to all directed edges which do not have primary conflict or secondary conflict and are contained in the set E in the conflict graph G through a dotted line, and deleting all solid-line directed edges in the conflict graph G to obtain a complement graph G' of the conflict graph G;
(4) renumbering nodes in the complementary graph G':
according to the numbering rule of { y,1}, { y-1,2}, { y-2,3}, …, numbering the nodes in the complementary graph G' again in sequence, and realizing the steps as follows:
(4a) setting a number set, and deleting the numbers of all nodes in the complementary graph G':
setting a number set I with a maximum value y equal to the total number of nodes of the complementary graph G ' {1,2, …, I, …, y }, where I denotes a number for renumbering the nodes in the complementary graph G ', and deleting the number of each node in the complementary graph G ';
(4b) nodes with medium maximum and second maximum degrees in the supplementary graph G' are numbered:
sequencing unnumbered nodes in the complementary graph G ' according to the sequence of the node degrees from large to small, numbering the node with the maximum node degree in the complementary graph G ' by using the last number in the set I, numbering the node with the second maximum node degree in the complementary graph G ' by using the first number in the set I, and then deleting the two used numbers from the set I;
(4c) judging whether a unnumbered node exists in the neighbor node set of each of the two numbered nodes in the supplementary graph G', if so, executing the step (4d), otherwise, executing the step (4 f);
(4d) judging whether an unnumbered node exists in the neighbor node set of each of the two numbered nodes in the supplementary graph G', if so, executing the step (4e), otherwise, executing the step (4 f);
(4e) numbering the neighbor nodes:
numbering the neighbor nodes of the nodes with the maximum node degree in the complementary graph G 'by using the first number in the set I, numbering the neighbor nodes of the nodes with the second maximum node degree in the complementary graph G' by using the last number in the set I, deleting the two used numbers from the set I, and executing the step (4 f);
(4f) judging whether the number of the numbers in the set I is larger than 1, if so, executing the step (4b), otherwise, executing the step (4 g);
(4g) judging whether the number of the numbers in the set I is equal to 1, if so, numbering the last node of the complementary graph G ' by using the last number in the set I, replacing the complementary graph G ' by using the numbered complementary graph to obtain a newly numbered complementary graph G ', and otherwise, replacing the complementary graph G ' by using the complementary graph numbered in the steps (4b) and (4e) to obtain a newly numbered complementary graph G ';
(5) acquiring a new complementary graph H:
adding the maximum cluster M of the patch G 'into the set MS, and deleting the nodes in the maximum cluster M from the patch G' to obtain a new patch H;
(6) judging whether the new supplementary graph H is an empty graph, if so, executing the step (7), otherwise, replacing the supplementary graph G' with the new supplementary graph H, and executing the step (4);
(7) channel frequencies are assigned to each maximum clique in the set MS:
allocating any channel frequency F in the set F to each maximum group in the set MS in the current time slotlAnd judging whether the maximum groups which are not allocated with the channel frequencies exist in the set MS, if so, allocating the channel frequencies for the maximum groups which are not allocated with the channel frequencies in the set MS at the next time slot of the current time slot until all the maximum groups in the MS are allocated with the channel frequencies, and otherwise, realizing the channel frequency allocation of each maximum group in the set MS.
Compared with the prior art, the invention has the following advantages:
firstly, the invention gradually obtains the complement of the conflict graph of the independent multi-channel TDMA network model, obtains the maximum cluster set by solving the maximum clusters of the complement graph, and finally allocates different channel frequencies to each maximum cluster in the maximum cluster set to complete the independent multi-channel TDMA network link scheduling, thereby maximizing the number of links capable of being transmitted simultaneously, improving the spatial multiplexing of the links, solving the problems that the calculation of unnecessary weight of the maximum independent set of the conflict graph is still carried out after the maximum independent set sequence is obtained in the prior art, causing the increase of the calculated amount and not bringing substantial optimization to the result of the independent multi-channel TDMA network link scheduling, ensuring the network capacity, spending smaller calculated amount and reducing the time complexity of the independent multi-channel TDMA network link scheduling.
Secondly, the nodes in the complementary graph are numbered again, so that the deep searching sequence of the nodes of the backtracking method is optimized, and the problems of more searching nodes and overlarge time complexity caused by the fact that the nodes are only sorted according to the ascending or descending sequence of the node degrees in the prior art are solved.
Drawings
FIG. 1 is a flow chart of an implementation of the present invention;
FIG. 2 is a diagram of a model for a stand-alone multi-channel TDMA network in an embodiment of the invention;
FIG. 3 is a diagram illustrating the collision relationship between directed edges defined by an independent multi-channel TDMA network model according to an embodiment of the present invention;
FIG. 4 is a diagram of collisions for an independent multi-channel TDMA network model in an embodiment of the present invention;
FIG. 5 is a complement of a conflict graph in an embodiment of the present invention;
FIG. 6 is a flow chart of an implementation of the present invention for renumbering nodes in a complementary graph.
Detailed Description
The invention is described in further detail below with reference to the figures and the specific embodiments.
Referring to fig. 1, the present invention includes the steps of:
step 1) creating an independent multi-channel TDMA network model:
step 1a) creating an independent multi-channel TDMA network model comprising a node set N, an edge set E and a channel frequency set F, wherein N is {1,2, …, k, … N }, k represents a serial number of a node, N represents the total number of nodes, and N is more than or equal to 2; e ═ E1，2，e2，1，…，ep，q，eq，p，…，es，t，et，s}，p≠q，s≠t，ep，qAnd eq，pRespectively representing directed edges with a starting point of a node p and an end point of a node q, and directed edges with a starting point of a node q and an end point of a node p, wherein the number of the directed edges is x, and x is more than or equal to 2 and less than or equal to n (n-1); f ═ F1，f2，…，fl，…，fm}，flRepresents the l-th channel frequency, m represents the total number of the channel frequencies, and m is more than or equal to 2;
the independent multi-channel TDMA network model adopted in this embodiment has a structure as shown in fig. 2, and includes a node set N ═ {1,2, 3, 4}, where the total number N of nodes is equal to 4, because the larger the total number of nodes is, the later obtained collision graph of the network modelThe more complex; e ═ E1，2，e2，1，e2，3，e3，2，e3，4，e4，3-6 directed edges, x being equal to 6, where x has no relation to the total number N of nodes in the set N; f ═ F1，f2The total number of channel frequencies m is equal to 2 for reasons of simplicity.
Step 1b) defining the intersected directed edges in the E as directed edges with main conflicts, wherein the intersected directed edges in the E are not intersected but are intersected with a third edge at the same time, and the starting point and the end point of the third directed edge are respectively the starting point of one directed edge and the end point of the other directed edge, so that the two directed edges are directed edges with secondary conflicts;
in the embodiment, the collision relationship between directed edges defined by the independent multi-channel TDMA network model, where the main collision is as shown in fig. 3(a), and the collision generated when two links share the same node includes three cases, namely, a collision that receives data simultaneously, such as a directed edge e1，3And e2，3The node 3 receives data from the node 1 and the node 2 at the same time; collisions in which data is both transmitted and received, e.g. directed edge e4，6And e6，5Node 6 both sends data to node 5 and receives data from node 4; collisions of simultaneous transmitted data, e.g. directed edge e9，7And e9，8Node 9 sends data to both node 7 and node 8.
Secondary collision As shown in FIG. 3(b), two links do not share a node, but the transmission of one link affects the reception of the other link, including two cases, such as a directed edge e1，2And e3，4The two edges do not share a node, but the sending of data by node 3 to node 4 affects the receiving of data by node 2 from node 1; such as a directed edge e5，6And e7，8The two edges do not share a node, but node 5 sending data to node 6 affects node 8 receiving data from node 7.
Step 2) obtaining a conflict graph G of the independent multi-channel TDMA network model:
step 2a) setting a node set V with the number of nodes equal to 6 of directed edges in the set E, at least having a maximum clique set MS of a maximum clique, and emptying the set V and the set MS;
step 2b) is to arrange each directed edge E in the set Ep，qMapping the node to a node in the set V to obtain a node set V';
step 2c) connecting nodes corresponding to all the directed edges with main conflicts in the set V 'and all the directed edges with secondary conflicts in the set E through solid lines, and numbering each node in the set V' in an increasing mode according to a natural number set to obtain a conflict graph G of the independent multi-channel TDMA network model;
the conflict graph of the independent multi-channel TDMA network model obtained through step 2) is shown in fig. 4, and the conflict graph includes 6 nodes, each of which corresponds to each directed edge in the independent multi-channel TDMA network model one-to-one, all nodes having a conflict relationship are connected by a solid line, node 1 is not connected with node 6, and node 2 is not connected with node 5.
Step 3), acquiring a complementary graph G' of the conflict graph G:
connecting nodes corresponding to all directed edges which do not have primary conflict or secondary conflict and are contained in the set E in the conflict graph G through a dotted line, and deleting all solid-line directed edges in the conflict graph G to obtain a complement graph G' of the conflict graph G;
the complement of the conflict graph obtained through step 3) is shown in fig. 5, and the complement still contains 6 nodes, and there are connections between node 1 and node 6 and connections between node 2 and node 5.
Step 4), numbering the nodes in the complementary graph G' again:
for the present embodiment, the nodes in the complementary graph G 'are sequentially renumbered according to the numbering rule of {6, 1}, {5, 2}, and {4, 3}, and the renumbering of the nodes in the complementary graph G' is further described in detail with reference to fig. 6:
step 4a) setting a number set, and deleting the numbers of all nodes in the complementary graph G':
setting a number set I of a maximum value y equal to the total number of nodes 6 of the complementary graph G ' {1,2, 3, 4, 5, 6}, wherein the numbers represent numbers for renumbering the nodes in the complementary graph G ', and deleting the number of each node in the complementary graph G ';
step 4b) numbering the nodes with the medium maximum degree and the second maximum degree in the complementary graph G':
sequencing unnumbered nodes in the complementary graph G ' according to the sequence of the node degrees from large to small, numbering the node with the maximum node degree in the complementary graph G ' by using the last number in the set I, numbering the node with the second maximum node degree in the complementary graph G ' by using the first number in the set I, and then deleting the two used numbers from the set I;
step 4c) judging whether a node which is not numbered exists in the neighbor node set of each of the two numbered nodes in the supplementary graph G', if so, executing step 4d), otherwise, executing step 4 f);
step 4d) judging whether one unnumbered node respectively existing in the neighbor node set of the two numbered nodes in the supplementary graph G' is a neighbor node or not, if so, executing step 4e), otherwise, executing step 4 f);
step 4e) numbering the neighbor nodes:
numbering the neighbor nodes of the nodes with the maximum node degree in the complementary graph G 'by using the first number in the set I, numbering the neighbor nodes of the nodes with the second maximum node degree in the complementary graph G' by using the last number in the set I, deleting the two used numbers from the set I, and executing the step 4 f);
step 4f) judging whether the number of the numbers in the set I is larger than 1, if so, executing step 4b), otherwise, executing step 4 g);
step 4G) judging whether the number of the numbers in the set I is equal to 1, if so, numbering the last node of the supplementary graph G ' by using the last number in the set I, replacing the supplementary graph G ' by using the numbered supplementary graph to obtain a renumbered supplementary graph G ', and otherwise, replacing the supplementary graph G ' by using the numbered supplementary graph in the step 4b) and the step 4e) to obtain a renumbered supplementary graph G ';
the reason for the process of renumbering the nodes in the complementary graph G' in step 4) is explained as follows: the numbering rule according to the form of {6, 1}, {5, 2}, and {4, 3} is adopted, so that the deep search sequence of the backtracking method used subsequently in the embodiment is actually optimized, if the node degree is renumbered only according to the descending order of the node degree, the node with the maximum degree is searched first when the node is searched, and although a clique can be found quickly and the probability that the clique is the maximum clique is higher, the nodes searched in the subsequent search process of the clique are verified to be more; and numbering is carried out again according to the increasing sequence of the node degrees, so that the node with the minimum searching degree is searched first when the node is searched, the possibility that the cluster to be found is the maximum cluster is higher in the later process, and the invalid condition of the search in the earlier stage is more, so that the node is sorted according to the node degrees and then numbered alternately, and the two defects can be avoided.
The complement after renumbering obtained in step 4) is the same as in fig. 5.
Step 5), acquiring a new complementary graph H:
adding the maximum cluster M of the patch G 'into the set MS, and deleting the nodes in the maximum cluster M from the patch G' to obtain a new patch H;
the two concepts of cliques and maximum cliques are explained as follows: in graph theory, a graph clique is defined as a subset of a vertex set of the graph, the vertex subset satisfies that any two nodes are adjacent, the number of nodes in the clique is called the clique number, and the clique with the largest graph number is the maximum clique.
The method for solving the maximum clique M of the complementary graph G ' adopts a backtracking method, and comprises the specific steps of firstly setting the maximum clique of the complementary graph G ' to be empty, then judging whether a clique is still formed after any vertex of the complementary graph G ' is added into the maximum clique, if so, considering the two situations of adding the vertex into the maximum clique or abandoning the vertex, otherwise, directly abandoning the vertex, and then recursively judging whether a clique is still formed after the next vertex of the complementary graph G ' is added into the maximum clique or not until all nodes in the complementary graph G ' are judged.
Step 6) judging whether the new supplementary graph H is an empty graph, if so, executing step 7), otherwise, replacing the supplementary graph G' with the new supplementary graph H, and executing step 4);
step 7) assigning a channel frequency to each maximum cluster in the set MS:
allocating any channel frequency F in the set F to each maximum group in the set MS in the current time slotlAnd judging whether the maximum groups which are not allocated with the channel frequencies exist in the set MS, if so, allocating the channel frequencies for the maximum groups which are not allocated with the channel frequencies in the set MS at the next time slot of the current time slot until all the maximum groups in the MS are allocated with the channel frequencies, and otherwise, realizing the channel frequency allocation of each maximum group in the set MS.
In the present embodiment, the obtained maximum cluster set MS is { {1, 6}, {2, 5}, {3}, and {4} }, and F is { { F { { 6} }1，f2After the channel frequency in the MS is allocated to each maximum group in the MS, the result is: in the first time slot, f is set1Is assigned to {1, 6}, and f is assigned2Is assigned to {2, 5}, and in the second time slot, f is assigned1Is assigned to {3}, and f is assigned2Is assigned to {4 }.
Referring to fig. 2 and 4, and in combination with the corresponding relationship between the directed edge in the independent multi-channel TDMA network model and the node in the conflict graph, the link scheduling result of the independent multi-channel TDMA network is obtained as follows: in the first time slot, at the channel frequency f1Scheduling { e }1，2，e4，3At channel frequency f2Scheduling { e }2，1，e3，4At the second time slot, at the channel frequency f1Scheduling { e }2，3At channel frequency f2Scheduling { e }3，2}。
Claims (2)
1. A method for collision-free link scheduling for independent multi-channel TDMA networks, comprising the steps of:
(1) creating an independent multi-channel TDMA network model:
(1a) creating an independent multi-channel TDMA network model comprising a node set N, an edge set E and a channel frequency set F, wherein N is {1,2, …, k, … N }, k represents the serial number of the node, N represents the total number of the node, and N is more than or equal to 2;E＝{e1,2,e2,1,…,ep,q,eq,p,…,es,t,et,s}，p≠q,s≠t，ep,qand eq,pRespectively representing directed edges with a starting point of a node p and an end point of a node q, and directed edges with a starting point of a node q and an end point of a node p, wherein the number of the directed edges is x, and x is more than or equal to 2 and less than or equal to n (n-1); f ═ F1,f2,…,fl,…,fm}，flRepresents the l-th channel frequency, m represents the total number of the channel frequencies, and m is more than or equal to 2;
(1b) defining the intersected directed edges in the E as directed edges with main conflicts, wherein the intersected directed edges in the E are not intersected but are intersected with a third edge at the same time, and the starting point and the end point of the third directed edge are respectively the starting point of one directed edge and the end point of the other directed edge, so that the two directed edges are directed edges with secondary conflicts;
(2) obtaining a conflict graph G of an independent multi-channel TDMA network model:
(2a) setting a node set V with the number of nodes equal to the number x of directed edges in the set E, at least having a maximum clique set MS of a maximum clique, and emptying the set V and the set MS;
(2b) each directed edge E in the set Ep,qMapping the node to a node in the set V to obtain a node set V';
(2c) connecting nodes corresponding to all the directed edges with main conflicts in the set E in the set V 'through solid lines, simultaneously connecting nodes corresponding to all the directed edges with secondary conflicts in the set E through solid lines, and numbering each node in the set V' in an increasing mode according to a natural number set to obtain a conflict graph G of the independent multi-channel TDMA network model;
(3) acquiring a complement G' of the conflict graph G:
connecting nodes corresponding to all directed edges which do not have primary conflict or secondary conflict and are contained in the set E in the conflict graph G through a dotted line, and deleting all solid-line directed edges in the conflict graph G to obtain a complement graph G' of the conflict graph G;
(4) renumbering nodes in the complementary graph G':
according to the numbering rule of { y,1}, { y-1,2}, { y-2,3}, …, numbering the nodes in the complementary graph G' again in sequence, and realizing the steps as follows:
(4a) setting a number set, and deleting the numbers of all nodes in the complementary graph G':
setting a number set I with a maximum value y equal to the total number of nodes of the complementary graph G ' {1,2, …, I, …, y }, where I denotes a number for renumbering the nodes in the complementary graph G ', and deleting the number of each node in the complementary graph G ';
(4b) nodes with medium maximum and second maximum degrees in the supplementary graph G' are numbered:
sequencing unnumbered nodes in the complementary graph G ' according to the sequence of the node degrees from large to small, numbering the node with the maximum node degree in the complementary graph G ' by using the last number in the set I, numbering the node with the second maximum node degree in the complementary graph G ' by using the first number in the set I, and deleting the last number and the first number in the set I;
(4c) judging whether a unnumbered node exists in the neighbor node set of each of the two numbered nodes in the supplementary graph G', if so, executing the step (4d), otherwise, executing the step (4 f);
(4d) judging whether an unnumbered node exists in the neighbor node set of each of the two numbered nodes in the supplementary graph G', if so, executing the step (4e), otherwise, executing the step (4 f);
(4e) numbering the neighbor nodes:
numbering the neighbor nodes of the nodes with the maximum node degree in the complementary graph G 'by using the first number in the set I, numbering the neighbor nodes of the nodes with the second maximum node degree in the complementary graph G' by using the last number in the set I, deleting the two used numbers from the set I, and executing the step (4 f);
(4f) judging whether the number of the numbers in the set I is larger than 1, if so, executing the step (4b), otherwise, executing the step (4 g);
(4g) judging whether the number of the numbers in the set I is equal to 1, if so, numbering the last node of the complementary graph G ' by using the last number in the set I, replacing the complementary graph G ' by using the numbered complementary graph to obtain a newly numbered complementary graph G ', and otherwise, replacing the complementary graph G ' by using the complementary graph numbered in the steps (4b) and (4e) to obtain a newly numbered complementary graph G ';
(5) acquiring a new complementary graph H:
adding the maximum cluster M of the patch G 'into the set MS, and deleting the nodes in the maximum cluster M from the patch G' to obtain a new patch H;
(6) judging whether the new supplementary graph H is an empty graph, if so, executing the step (7), otherwise, replacing the supplementary graph G' with the new supplementary graph H, and executing the step (4);
(7) channel frequencies are assigned to each maximum clique in the set MS:
allocating any channel frequency F in the set F to each maximum group in the set MS in the current time slotlAnd judging whether the maximum groups which are not allocated with the channel frequencies exist in the set MS, if so, allocating the channel frequencies for the maximum groups which are not allocated with the channel frequencies in the set MS at the next time slot of the current time slot until all the maximum groups in the MS are allocated with the channel frequencies, and otherwise, realizing the channel frequency allocation of each maximum group in the set MS.
2. A collision-free link scheduling method for independent multi-channel TDMA networks according to claim 1, characterized in that: the maximum clique M of the patch G ' in the step (5) is calculated by adopting a backtracking method, and the specific idea is that the maximum clique of the patch G ' is firstly set to be empty, then whether a clique is still formed after any vertex of the patch G ' is added into the maximum clique is judged, if yes, the vertex is added into the maximum clique or the vertex is abandoned, otherwise, the vertex is directly abandoned, and then whether a clique is still formed after the next vertex of the patch G ' is added into the maximum clique is recursively judged until all nodes in the patch G ' are judged.
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