Patent Description:
Industry <NUM>, as the fusion of the Industrial Internet of Things (IIOT) and the Cyber-Physical System (CPS), points out that digitization, networking and intelligence are the future development directions of the manufacturing industry. As an important part of Industry <NUM>, industrial wireless networks are also the basis of intelligent manufacturing. Industry <NUM> has the characteristic of diverse application, which means that a single wireless technology cannot satisfy the need of diverse application. Therefore, multiple wireless networks are required to operate in the same range.

The wireless networks can be classified according to heterogeneous access mechanisms: time division multiple access (TDMA) and carrier sense multiple access (CSMA). Due to the openness of ISM band, TDMA-based industrial wireless networks WirelessHART, ISA100.11a, WIA-PA and WIA-FA, and other wireless networks WiFi, Bluetooth, ZigBee and LTE-U work in this band, which inevitably causes the coexistence problem on the spectrum. Some existing wireless coexistence standards, such as IEEE <NUM> and IEEE <NUM>, support coexistence of multiple wireless networks for resource allocation from the architecture, but fail to provide specific resource allocation algorithms. The existing resource allocation algorithm mainly aims at the coexistence problem of CSMA and CSMA networks and the coexistence problem of CSMA and TDMA networks, and only considers the situation that a single channel is available for the coexistence problem of multiple TDMA wireless networks. Therefore, with respect to the need of diversification of Industry <NUM>, the coexistence of the TDMA-based wireless networks of any network number and any network size becomes an important problem that needs to be solved urgently. Known resource allocating methods are described in <NPL>) and <CIT>.

The line topology is also called a line structure, and is universal in the industrial environments, such as intelligent production lines, smart grids and oil pipeline monitoring. At the same time, the line topology is indispensable in the industrial wireless networks due to the advantages of simple structure and strong scalability. Therefore, a new resource allocation algorithm needs to be designed, to solve the coexistence problem of multiple line topological industrial wireless networks.

Aspects of the present invention are defined in the appended independent claim. Optional features of the present invention are defined in the appended dependent claims.

An optimized resource allocation method for coexistence of multiple line topological industrial wireless networks proposed by the present invention is proposed by adequately considering the requirements of minimizing overall scheduling delay. Firstly, the lower bound of scheduling delay of multiple networks is theoretically analyzed, and then the design of the allocation algorithm of inter-network resources and the allocation algorithm of intra-network resources is guided based on theoretical analysis results.

The present invention adopts the following technical solution: a resource allocation method for coexistence of multiple line topological industrial wireless networks comprises the following steps:.

The minimum scheduling delay value is: <MAT> wherein Ridle(j) represents the number of idle resource blocks of j networks, and Ro(i) represents the number of resource blocks occupied by network i, which are respectively represented by the following expressions: <MAT> <MAT>.

N is the number of wireless networks in line topology, and the number of nodes of network i is ni; i ∈ [<NUM>, N]; the number of available channels in the networks is C.

The operation of allocating resources for the networks based on the minimum scheduling delay value comprises the following steps:.

The <MAT>, Bvik(t) represents the number of data packets in the buffer of the node vik at the current time t, wherein the label of the node is k ∈ [<NUM>, ni] and ni is the number of nodes in the network.

The operation of allocating intra-network resources of the networks comprises the following steps:.

The operation of assessing and allocating resources comprises the following steps:.

The resources are resource blocks and comprise a time slot and an available channel of the time slot.

The resource allocation method for coexistence of multiple line topological industrial wireless networks is used for line topological industrial wireless networks for any network number and any network size. The resource allocation method for coexistence of multiple line topological industrial wireless networks is used for multiple line topological wireless networks.

The present invention has the following beneficial effects and advantages:.

To make the purpose, the technical solution and the advantages of the present invention more clear, the present invention will be further described below in detail in combination with practical examples.

The present invention proposes an optimized resource allocation method for coexistence of multiple line topological industrial wireless networks. The main idea of the present invention is: a general expression of the lower bound of the scheduling delay is provided; the minimum time slot required for each network to complete the scheduling is adequately considered to provide guidance for algorithm design; different priorities are allocated for the networks based on the analysis of the lower bound of delay, and then resources are allocated for the networks; nodes in the networks are assessed, a best node combination is selected and the number of parallel transmission nodes in each time slot is maximized, to improve the resource utilization ratio. Therefore, on the whole, the method comprises three stages: lower bound analysis of scheduling delay, allocation algorithm of inter-network resources and allocation algorithm of intra-network resources.

The method considers multiple line topological wireless networks. As shown in <FIG>, N wireless networks exist. Each network i(i ∈ [<NUM>, N]) is composed of a gateway vi<NUM> and a plurality of nodes vik. k ∈ [<NUM>, ni]; V<NUM> and VN<NUM> respectively represent the gateways in the network <NUM> and the network N; V<NUM>n<NUM> and VNnN respectively represent nodes with labels of n<NUM> and nN in the network <NUM> and the network N, wherein n<NUM> and nN respectively represent the total number of nodes included in the network <NUM> and the network N except the gateways. Because different networks use heterogeneous communication protocols, a central controller is required to be responsible for communicating with multiple networks. In the initialization stage before the start of a scheduling cycle, the gateways transmit information about the number of the nodes of the corresponding networks to the central controller. The central controller generates a scheduling table based on the information about the number of available channels and the number of nodes of each network, and issues the scheduling table to the corresponding networks. After the initialization stage is completed, each node generates a data packet, and transmits the data packet to the gateway through aggregation transmission according to the scheduling table. All the nodes are synchronized for time according to IEEE <NUM> standard. Herein, time is divided into multiple time slots of the same length. Each time slot allows to transmit the data packet of one node and the corresponding ACK. All the networks share a set of available channels. Because all the nodes work in the same frequency band and serious mutual interference exists between the networks and inside the networks within the same geographic range, any two nodes cannot use the same channel to transmit data in the same time slot. Each node in the network adopts a half-duplex communication mode. One node cannot receive and transmit the data packets at the same time, that is, adjacent nodes cannot obtain the resources for scheduling at the same time.

N wireless networks exist. Each network i(i ∈ [<NUM>, N]) has ni nodes, and the number of available channels is C. The current time is t; and Ridle(N) represents the number of idle resources of N wireless network, and can be calculated by the following general formula: <MAT> Ro(i) represents the number of resources occupied by the network i, and can be calculated by the following formula <MAT>.

When j satisfies the following situation, <MAT> the general formula of the minimum scheduling delay value is: <MAT>.

The allocation algorithm of inter-network resources comprises the following steps:
Step <NUM>: the purpose of the present invention is to design the allocation algorithm of inter-network resources to minimize the scheduling delay. Firstly, the priority of each network is assessed, and the following two conditions shall be satisfied: Sr = T - t + <NUM>; Nd - Ne = Nc - <NUM>.

Specifically, the lower bound T of the scheduling delay is used as a benchmark; at the current time t, the number of the remaining time slots is (T - t + <NUM>); Sr represents the minimum number of time slots required for completing scheduling; Sr = N |+ 2sum(max((Bvik(t) - <NUM>) , <NUM>)) + (|Nd |- |Ne|) can be obtained by the number of data packets of node buffers in the networks at the current time, wherein N |represents a last node label with data packet in the node buffer; Bvik(t) represents the number of the data packets in the node buffer of the node vik(k ∈ [<NUM>, ni]) at the current time t; Nd represents a set of nodes with data packets in a node buffer; Ne represents a set of nodes having data packets in the node buffer and an empty parent node buffer, i.e., Bvik(t) > <NUM> and Bvik-<NUM>(t) = <NUM>. When Sr = T - t + <NUM> represents that the network is in a critical state, priority must be given to the network. Taking <FIG> as an example, <FIG> shows the number of the data packets of the node buffers in the networks at the current time. Then, the network N<NUM> = <NUM>, 2sum(max(Bvik(t) - <NUM>) , <NUM>)) = <NUM> ,| Nd |= <NUM> and |Ne |= <NUM>. Therefore, the number of the minimum time slots required by the networks is Sr = <NUM>.

Nc represents the number of nodes having continuous data packets farthest from the gateway; and |Nd |- |Ne |= Nc - <NUM> represents the situation that nodes with continuous data in the networks only appear in the position farthest from the gateway. Taking <FIG> as an example, GW represents the gateway; v<NUM>-v<NUM> represent the nodes in the networks; and the number of data packets of each node buffer at the current time is labeled in the table in sequence. The network Nc = <NUM> and |Nd |- |Ne |= <NUM>; and the equation |Nd| - |Ne|= Nc - <NUM> is satisfied. The networks that satisfy the two conditions are set as high priority, and |Ne| resource blocks are allocated for each network until no idle resource block remains or all the networks with high priority have the allocated resource blocks. In addition, other networks are set as low priority.

Step <NUM>: if no idle resource remains at this time, the allocation of the inter-network resources is completed in the current time slot. If the idle resources remain, the remaining resources are allocated for the networks with low priority, and step <NUM> is performed.

Step <NUM>: the remaining networks with low priority are sorted in the descending order of the minimum number of time slots required to complete scheduling, and searched in the descending order. For the network having the difference between the required minimum numbers of the time slots less than or equal to <NUM>, step <NUM> is performed; otherwise, for the network having the difference between the required minimum numbers of the time slots greater than <NUM>, step <NUM> is performed.

Step <NUM>: for the network having the difference between the required minimum numbers of the time slots not greater than <NUM>, the node buffers of the network nodes that satisfy the conditions are combined, and different networks are separated by <NUM> node buffer. Specifically, when the difference is <NUM>, step <NUM> is performed; otherwise, when the difference is <NUM>, step <NUM> is performed.

Step <NUM>: when the difference of the minimum number Sr of the time slots required by the networks is <NUM>, the networks are sorted in a descending order of Sr, the node buffers of the node vi<NUM> to the last node viNl with data in the corresponding networks are combined; and different networks are separated by empty identifiers (<NUM> node buffer). As shown in <FIG>, at this moment, the minimum number of the time slots required by the network i is <NUM>, the minimum number of the time slots required by the network j is <NUM>, and the difference between the minimum numbers of the time slots required by the two networks is <NUM>. Therefore, according to the step <NUM>, the node buffers of two network nodes are combined; and the Sr value of the network j is greater than the Sr value of the network i according to the rule in the step <NUM>. Therefore, the network j is placed in the front half part, network i is placed in the back half part, and an empty identifier is placed in the middle, that is, separated by <NUM> node buffer.

Step <NUM>: when the difference of the minimum number of the time slots required by the networks is <NUM>, the numbers of the resources required by the networks are sorted; the required numbers Rr of the resources are combined in the descending order; the buffers of the node vi<NUM> to the last node viNl with data in the corresponding networks are combined; and each network is separated by empty identifier (<NUM> node buffer). Rr can be calculated by the number of the data packets in the node buffers: <MAT>. As show in <FIG>, at this moment, the minimum numbers of the time slots required by the network i and the network j are <NUM>, and the difference between the minimum numbers of the time slots required by the two networks is <NUM>. Therefore, according to the step <NUM>, the node buffers of two network nodes are combined; and the number of the resources required by the network i is <NUM> and the minimum number of the time slots required by the network j is <NUM> according to the rule in the step <NUM>. Therefore, the network j is placed in the front half part, the network i is placed in the back half part, and an empty identifier is placed in the middle, that is, separated by <NUM> node buffer.

Step <NUM>: the networks having the difference between the required minimum numbers of the time slots greater than <NUM> (the networks used to calculate the difference) are sorted in the descending order. Specifically, the sorted networks comprise a combined new network. Therefore, the remaining resources are firstly allocated to the network with large Sr in order, and the maximum number of resources that can be transmitted in parallel is allocated. If the resources remain at this moment, the resources are allocated for the next network until no idle resource remains or all the networks are allocated with the corresponding resources.

Claim 1:
A resource allocation method for a coexistence of multiple line topological industrial wireless networks, the coexistence comprising a central controller for communicating with the multiple line topological industrial wireless networks, wherein the method is implemented by the central controller, the method comprising the following steps:
obtaining a minimum scheduling delay value required for each of the networks to complete scheduling;
allocating inter-network resources for the networks based on the minimum scheduling delay value; and
allocating intra-network resources of each of the networks;
wherein the minimum scheduling delay value is: <MAT>
wherein Ridle(j) represents the number of idle resource blocks of j networks, and Ro(i) represents the number of resource blocks occupied by network i, which are respectively represented by the following expressions: <MAT> <MAT>
N is the number of line topological industrial wireless networks, the number of nodes of network i is ni; i ∈ [<NUM>, N]; and the number of available channels in the networks is C.