Multi-Topology Routing in Next-Generation IoT Networks

Abstract

A node device for forming a multi-hop network is provided. The node device is configured to discover two routing topologies: a normal routing topology for normal data transmission and a preferred topology for prioritized data transmission. The normal route is discovered for all data nodes in an IoT network, and the preferred route is discovered for only the preferred data nodes. The normal data route (D-route) is discovered using a distance-based route discovery protocol (RPL), and the preferred route (P-route) is optimally discovered for only the preferred data nodes to minimize route overlap, route transmission time, and route length. The node device includes a transceiver configured to transmit and receive normal data in a destination-oriented directed acyclic graph (DODAG)-based topology and transmit and receive priority data in the optimal routing topology; a memory configured to store a computer-executable program including a communication mode (CM), a multirate link count (MLC), a route overlap degree (DRO), neighbor node information, route transmission time, and route length; and a processor configured to execute the steps of the computer-executable program. The steps include finding a D route and finding a P route, where finding a P route includes finding a non-circular route, finding a minimum overlap route, finding a minimum transmission time route, and finding a minimum length route.

Description

[Technical Field]

[0001] The present invention relates generally to routing data in wireless communication networks, and more particularly to routing heterogeneous data in next generation wireless communication networks. [Background technology]

[0002] With the emergence of 5G and beyond communication technologies, consumer wireless devices are evolving from the current generation to the next generation. Next-generation wireless devices support multiple communication modes / interfaces and can perform more functions. During the transition phase, it is impractical to completely replace deployed current-generation devices with next-generation devices. Therefore, next-generation wireless networks will consist of a mixture of current-generation and next-generation nodes. Because existing routing protocols are typically designed for current-generation networks, it is necessary to address how to efficiently route diverse data in next-generation wireless networks.

[0003] Therefore, it is desirable to provide a new routing architecture for transmitting diverse data in next-generation IoT networks. Summary of the Invention

[0004] Some embodiments of the present invention are based on the recognition that as consumer wireless devices evolve from current to next generations, current generation devices support a single communication mode / interface and / or perform a single function, while next generation devices may support multiple communication modes / interfaces and / or perform more functions. Devices that support a single communication mode are referred to as single-mode, and devices that support multiple communication modes / interfaces are referred to as multi-mode.

[0005] Some embodiments of the present invention are based on the recognition that during a consumer device transition phase, it is impractical from a cost and service continuity perspective to replace all deployed current generation devices with next generation devices.

[0006] To this end, one objective of various embodiments of the present invention is to form a next-generation wireless IoT network using data concentrators and a mixture of current-generation and next-generation nodes. Data concentrators are considered multimode nodes, current-generation nodes are single-mode normal data nodes, and next-generation nodes are classified as multimode normal data nodes, single-mode preferred data nodes, and multimode preferred data nodes. Current-generation nodes and next-generation multimode normal data nodes collect only normal data, while next-generation single-mode preferred data nodes and next-generation multimode preferred data nodes collect both normal data and preferred data. Nodes that collect only normal data are called D nodes, and nodes that collect both normal data and preferred data are called P nodes.

[0007] Some embodiments of the present invention are based on the recognition that in multi-hop wireless networks, route discovery is unavoidable because at least one data node cannot communicate directly with the data concentrator and must relay communications via other data nodes.

[0008] Therefore, various embodiments of the present invention form two routing topologies for next-generation IoT networks: a normal topology and a preferred topology. The normal topology is used to transmit normal data, and the preferred topology is used to transmit priority data. The normal route in the normal topology, called the D-route, is discovered for all data nodes using a distance-based approach, while the preferred route in the preferred topology, called the P-route, is discovered only for priority nodes to minimize route overlap, route transmission, and route length. The D-route has low efficiency, while the P-route has high efficiency.

[0009] Some embodiments of the present invention are based on the recognition that nodes in a next-generation IoT network may be single-mode nodes or multi-mode nodes. Single-mode nodes support a low-speed communication mode, while multi-mode nodes support both low-speed and high-speed communication modes. To support interoperability, the low-speed communication mode of a multi-mode node must be the same as the low-speed communication mode of a single-mode node.

[0010] Thus, various embodiments of the present invention create low-speed links and high-speed links in a routing topology, where low-speed links are created between two single-mode nodes or between a single-mode node and a multi-mode node, and high-speed links are created only between two multi-mode nodes.

[0011] Some embodiments of the present invention are based on the recognition that priority nodes in next generation IoT networks can collect both normal and prioritized data, with the prioritized data having a higher priority than the normal data, and the transmission of the prioritized data having a higher priority than the transmission of the normal data.

[0012] Therefore, various embodiments of the present invention provide priority-based data routing such that when a data node transmits or relays both normal data and prioritized data, it transmits the prioritized data first. It is therefore an object of various embodiments of the present invention to provide a distributed D-route discovery method and a centralized P-route discovery method.

[0013] To this end, D-Route Discovery considers the multimode nodes present in the next-generation IoT network. These nodes are organized as a destination-oriented directed acyclic graph (DODAG) in the D-Route topology. The communication mode (CM) is included in the DODAG Information Object (DIO) message, where CM = 1 indicates a single-mode node and CM = 2 indicates a multimode node. CM can be used to calculate the multimode link count (MLC), which represents the number of multimode links along the route. A route with a smaller MLC comprises fewer multimode links, while a route with a larger MLC comprises more multimode links. Other conditions being equal, a data node selects a route with a larger MLC. Additionally, the cumulative traffic load (ATL) is included in the destination advertisement object (DAO) message, and the ATL parameter can be used to calculate the route communication time (RCT). Other conditions being equal, a data node selects a route with a smaller RCT.

[0014] Some embodiments of the present invention are based on the recognition that route overlap can delay data transmission and cause data loss. P route discovery depends on the number of nodes in the network, the number of preferred nodes, and node placement. It is not always possible to find overlap-free P routes. However, P route overlap can be minimized.

[0015] To this end, optimal P routes are found to minimize objectives such as route overlap, route transmission time, and route length. Therefore, a method for calculating the degree of route overlap is needed. However, existing route overlap calculation methods are defined for point-to-point (P2P) routing and are not suitable for multipoint-to-point (MP2P) routing. In MP2P routing, all routes have the same destination node, and since this destination node does not transmit data, it should not be counted in the route overlap calculation.

[0016] One objective of some embodiments is to define the route overlap of an MP2P route as the sum of the overlaps of each forwarding node caused by the route. A forwarding node is a node on the route that transmits or relays data. Mathematically, the route overlap is the total number of times a route repeatedly passes through a forwarding node.

[0017] Some embodiments of the present invention are based on the recognition that circular routes are inefficient because they have longer delays, waste communication bandwidth and node resources, and may interfere with other routes. Therefore, a non-circular P route must be found.

[0018] Therefore, some embodiments of the present invention provide a recursive non-cyclic route discovery method for finding a non-cyclic route from a preferred node to a data concentrator in a next-generation IoT network, which starts from the preferred node and extends the route hop-by-hop until the route reaches the data concentrator or the route cannot be extended without a cycle.

[0019] Some embodiments of the present invention are based on the realization that the maximum number of non-overlapping routes is equal to the number of physical neighbors of the data concentrator.

[0020] Therefore, an objective of some embodiments is to find P routes of preferred nodes that minimize route overlap. P route finding is formulated as a nonlinear optimization problem.

[0021] According to some embodiments of the present invention, there is provided a node apparatus for use in a multi-hop heterogeneous wireless network including single-mode nodes and multi-mode nodes. The node apparatus comprises a transceiver configured to transmit and receive messages to discover normal data routes (D-routes), the discovered D-routes forming a Destination-Oriented Directed Acyclic Graph (DODAG) topology, and the transceiver configured to transmit and receive normal data in the Destination-Oriented Directed Acyclic Graph (DODAG) topology and transmit and receive prioritized data in the optimal routing topology. The node apparatus comprises: a memory configured to store a computer-executable program and DODAG topology configuration parameters, including a rank, a communication mode (CM), and a multi-rate link number (MLC) specified by an Internet Protocol version 6 (IPv6) routing protocol for low power and lossy networks (RPL) protocol; and a processor configured to execute the steps of the computer-executable program. The steps include discovering D-routes of all data nodes to form a DODAG topology using an IPv6 routing protocol for low power and lossy networks (RPL), where the RPL protocol uses DODAG Information Object (DIO) messages to perform an upstream route discovery process and Destination Advertisement Object (DAO) messages to perform a downstream route discovery process. The steps include discovering neighboring nodes along with discovering D-routes, where a processor determines another node as a neighboring node when it receives a DIO message broadcast from the other node via a transceiver. The steps include transmitting, via the transceiver, an accumulated traffic load (ATL) and an identifier of the neighboring node to a data concentrator via a DAO message.

[0022] Some embodiments of the present invention further provide a node apparatus for use in a multi-hop heterogeneous wireless network including a multi-mode concentrator. The node apparatus includes a transceiver configured to acquire cumulative traffic load (ATL) and neighbor node information of data nodes to transmit a destination-oriented directed acyclic graph (DODAG) information object (DIO) message to initiate normal data route (D-route) discovery, receive a destination advertisement object (DAO) message to configure a downstream normal data route (D-route), and perform optimal preferred route (P-route) discovery to construct an optimal routing topology. The transceiver is configured to transmit the optimal routing topology to data nodes on the discovered preferred route (P-route) to transmit prioritized data to the multi-mode concentrator. The transceiver is configured to receive normal data in the DODAG topology and prioritized data in the optimal routing topology. The node apparatus includes a memory configured to store a computer-executable program and parameters including a communication mode (CM), an ATL, a neighbor node set, a route overlap degree (DRO), and optimal preferred route (P-route) discovery, and a processor configured to execute the steps of the computer-executable program. The steps include discovering D-routes for all data nodes using an Internet Protocol version 6 (IPv6) routing protocol for low power and lossy networks (RPL), where the RPL protocol uses DIO messages to perform an upstream route discovery process and Destination Advertisement Object (DAO) messages to perform a downstream route discovery process. The steps include discovering optimal preferred routes (P-routes) by formulating a P-route discovery problem as a nonlinear optimization problem to minimize route overlap calculated using the DIO, where the discovered optimal P-route is further optimized to minimize route transmission time and route length.

[0023] Some embodiments are based on the recognition that the minimum overlap route discovery problem can be a multi-solution problem in which a set of multiple P routes can minimize route overlap.

[0024] To that end, some embodiments of the present invention provide a method for determining a set of minimally overlapping P routes so as to minimize the total route transmission time.

[0025] Additionally, some embodiments of the present invention also provide a method for determining a set of minimally overlapping P routes so as to minimize the total route length.

[0026] The present invention will now be described in detail with reference to the accompanying drawings, which are not necessarily to scale, emphasis instead being placed upon illustrating the principles of embodiments of the present disclosure. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a schematic diagram illustrating a next-generation wireless IoT network consisting of a data concentrator and a mix of current-generation and next-generation nodes. [Figure 2] The present invention illustrates a node classification in a next-generation wireless IoT network, in which a data concentrator is a multi-mode node, a current-generation node is a normal single-mode node, and a next-generation node includes a multi-mode normal node, a preferred single-mode node, and a preferred multi-mode node. [Figure 3] FIG. 1 illustrates an example of a two-topology routing architecture in a next-generation wireless IoT network. [Figure 4] FIG. 1 is a diagram illustrating an example of a circular route and a non-circular route in a next-generation wireless IoT network. [Figure 5] FIG. 1 is a diagram illustrating an example of a sub-route on a route from a priority node p to a data concentrator C in a multipoint-to-point (MP2P) routing topology in a next-generation wireless IoT network. [Figure 6]FIG. 1 is a diagram illustrating an example of end nodes and non-end nodes when a non-circular P route is discovered in a next-generation wireless IoT network. [Figure 7] FIG. 11 illustrates the sub-route extension and expansion of a preferred node when discovering a non-cyclic P route in a next-generation wireless IoT network. [Figure 8A] FIG. 1 illustrates an algorithm for setting up acyclic route discovery of preferred nodes in next-generation wireless IoT networks. [Figure 8B] FIG. 1 illustrates an algorithm for recursively extending and expanding acyclic sub-routes of preferred nodes in next-generation wireless IoT networks. [Figure 9] This is an algorithm for finding the minimum overlapping route of all priority nodes in next-generation wireless IoT networks. [Figure 10] FIG. 1 is a diagram illustrating time allocation for prioritized data transmission and normal data transmission in a next-generation wireless IoT network. DETAILED DESCRIPTION OF THE INVENTION

[0028] While the above-described drawings illustrate embodiments of the present disclosure, other embodiments are contemplated, as discussed above. The present disclosure illustrates exemplary embodiments and is not intended to be limiting. Those skilled in the art can devise numerous other variations and implementations that fall within the scope and spirit of the principles of the disclosed embodiments.

[0029] In current-generation IoT networks, devices typically have fewer resources and perform simple functions. For example, these devices are battery-powered, support the IEEE 802.15.4 communication protocol, and transmit data using FSK modulation. Next-generation IoT networks, on the other hand, typically include a mix of current-generation and next-generation devices. The next-generation devices are equipped with more resources and can perform more functions. For example, the next-generation devices may use grid power, support both the IEEE 802.15.4 communication protocol and the LTE / 5G communication protocol, and use both FSK and QAM modulation. Therefore, next-generation devices in next-generation IoT networks can perform multiple roles. Take, for example, a next-generation smart meter network that includes current-generation and next-generation meters. The current-generation meters only collect metering data and periodically transmit the metering data to a data concentrator. However, the next-generation meters may 1) collect both metering data and power supply information, 2) support multiple communication modes / interfaces, or 3) collect both metering data and power supply information while supporting multiple communication modes / interfaces. Power supply information, transmitted in last-gasp messages, is important for power suppliers to perform predictive maintenance on smart meter networks and diagnose the causes of abnormal events such as power outages. This information has a higher priority than regular metering data. Therefore, next-generation meters that collect power supply information are called priority meters. Therefore, priority meters must efficiently transmit event-based last-gasp messages in addition to periodically transmitting metering data.

[0030] In next-generation IoT networks, nodes may be classified based on different criteria, such as (1) their role as data source or data destination, (2) their communication capabilities, and (3) their data collection capabilities. Based on criterion 1), a node that collects data is called a data node, and a node that aggregates data is called a data concentrator. Based on criterion 2), a node that supports one communication mode is called a single-mode node, and a node that supports multiple communication modes / interfaces is called a multi-mode node. In particular, a data concentrator is a multi-mode node. Based on criterion 3), a node that collects only normal data is called a normal node, and a node that collects both normal data and prioritized data is called a prioritized node.

[0031] FIG. 1 is a schematic diagram illustrating a next-generation wireless IoT network including a data concentrator 100, a current-generation single-mode normal data node 110, a next-generation multimode normal data node 120, a next-generation single-mode-preferred data node 130, and a next-generation multimode-preferred data node 140. These nodes form a multi-hop mesh network. Typically, data packets are transmitted from a data node (current-generation node or next-generation node) to the data concentrator 100, but control messages can be transmitted in either direction. Because at least one data node cannot communicate directly with the data concentrator 100, communication must be relayed through an intermediate node. Single-mode nodes can only support a low-speed communication mode. However, multimode nodes can support both low-speed and high-speed communication modes. As a result, a low-speed link 150 is formed by two single-mode nodes or by a single-mode node and a multimode node. Meanwhile, a high-speed link 160 is formed by only two multimode nodes. The single-mode nodes include the current-generation normal data node 110 and the next-generation single-mode-preferred data node 130. The multimode nodes include a next generation multimode regular data node 120, a next generation multimode preferred data node 140, and a data concentrator 100.

[0032] 2 shows node classification in a next-generation wireless network. Nodes in a next-generation IoT network 200 are first classified into data nodes 210 and data concentrators 220. Data concentrators 220 are considered multimode nodes 230. Data nodes 210 are further classified into current-generation data nodes 240 and next-generation data nodes 260. Current-generation data nodes 240 are classified into single-mode normal data nodes 250, and next-generation data nodes 260 are classified into multimode normal data nodes 270, single-mode preferred data nodes 280, and multimode preferred data nodes 290.

[0033] Routing is inevitable for transmitting data in multi-hop IoT networks. Routing has been widely studied for many years. The concept of routing is simple. However, the routing problem is a high-complexity problem consisting of two steps: route discovery and routing scheduling. Route discovery can be an NP-complete problem. For example, maximizing the throughput of a multi-hop wireless network has been proven to be NP-hard due to the effects of wireless interference. In addition, in a two-dimensional mesh topology, both the centralized and distributed routing scheduling problems have also been proven to be NP-complete, further increasing the complexity of the routing scheduling problem.

[0034] Well-known route discovery protocols include the Dijkstra shortest route algorithm, dynamic source routing (DSR), ad hoc on-demand distance vector (AODV), and the Internet Protocol version 6 (IPv6) routing protocol for low-power and lossy networks (RPL). However, these routing protocols are not designed to handle heterogeneous data and heterogeneous nodes. For example, RPL sends all uplink traffic to a default parent node and uses the same network configuration parameters for all nodes. Therefore, there is a need to address the challenges that arise in next-generation IoT networks.

[0035] Many issues need to be addressed for next-generation IoT networks to function efficiently. Route overlap is one of the issues that must be addressed by next-generation IoT networks, especially when transmitting priority data. Route overlap can have a significant impact on network performance. Route overlap can delay data transmission and cause data loss in wireless networks. Therefore, to improve the reliability of priority data transmission, it is necessary to minimize route overlap, especially the overlap of routes used to transmit priority data.

[0036] The present invention provides a two-topology routing architecture for next-generation IoT networks: a normal topology used for normal data transmission and a preferred topology used for prioritized data transmission. Routes in the normal topology are called normal data routes (D-routes), and routes in the preferred topology are called preferred routes (P-routes). D-routes are discovered for all data nodes in the network. However, P-routes are discovered only for prioritized data nodes. D-routes are discovered using traditional protocol-based techniques. However, P-routes are discovered using the inventive optimal technique, which formulates P-route discovery as an optimization problem. Therefore, P-routes are optimal routes that minimize route overlap, route transmission time, and route length.

[0037] FIG. 3 illustrates an example of a two-topology routing architecture for a next-generation IoT network including a data concentrator C, two next-generation multimode normal data nodes 1 and 5, three next-generation single-mode preferred data nodes 2, 6, and 14, and ten current-generation single-mode data nodes 3, 4, 7, 8, 9, 10, 11, 12, 13, and 15. Route 300, indicated by dashed arrows, represents a D route in the routing topology for transmitting normal data. These distance-based routes are discovered using a conventional RPL protocol. Route 310, indicated by solid arrows, represents a P route in the routing topology for transmitting prioritized data. These routes are discovered using the optimal method provided by the present invention. The routes for prioritized data nodes 2, 6, and 14 in the two topologies are different. In the normal topology, routes 2 → C, 6 → 2 → C, and 14 → 9 → 3 → C overlap at node 2. However, in the priority topology, routes 2 → C, 6 → 5 → 1 → C, and 14 → 9 → 3 → C do not overlap. Also, links 5 → 1 and 1 → C are high-speed links. The P route uses these high-speed links. However, the D route does not have these high-speed links. Assume that the PHY data rate in the low-speed communication mode is 100 kbps and the PHY data rate in the high-speed communication mode is 800 kbps. The low-speed link takes 8 ms to transmit a 100-byte packet. However, the high-speed link takes only 1 ms. Furthermore, IoT devices are usually half-duplex. Considering wireless link interference and ignoring random backoff delays, the D route takes 32 ms to transmit three priority data packets. In contrast, the P route takes only 26 ms. These results indicate that the P route may be longer but is more efficient. The Need for Multi-Topology Routing

[0038] With the emergence of 5G and beyond, consumer IoT devices are evolving from the current generation to the next generation. Current-generation devices are deployed with fewer resources and perform simpler functions. For example, current-generation devices support one communication mode (called single-mode devices) and collect normal data. Meanwhile, next-generation devices are equipped with more resources and perform more functions. For example, next-generation devices support multiple communication modes / interfaces (called multi-mode devices) and / or can collect both normal and prioritized data (called prioritized devices). However, during the transition phase, it is impractical to completely remove deployed current-generation devices. For example, consider a next-generation smart meter network that includes current-generation normal meters and next-generation priority meters. The normal meters periodically collect and transmit metering data. On the other hand, the priority meters not only collect normal metering data but also detect power supply information. This information is important for power suppliers to perform predictive maintenance and diagnose the causes of abnormal events such as power outages, and therefore has a higher priority than normal metering data. Therefore, priority meters must efficiently transmit power supply information in addition to normal metering data. Therefore, a new routing architecture is needed to transmit heterogeneous data in next-generation IoT networks. To this end, we need to address how to efficiently route diverse data in next-generation IoT networks.

[0039] While routing for current-generation IoT networks has been extensively studied, routing for next-generation IoT networks has not yet been thoroughly studied. This invention provides a two-topology routing architecture for next-generation IoT networks: a normal topology used for normal data transmission and a prioritized topology used for prioritized data transmission. Routes in the normal topology are called D-routes, and routes in the prioritized topology are called P-routes. Data nodes that collect only normal data are called D-nodes, and data nodes that collect both normal and prioritized data are called P-nodes. D-routes are discovered for all data nodes in the network. However, P-routes are discovered only for prioritized data nodes. D-routes are discovered using a distance-based approach. However, P-routes are discovered using an optimal approach that formulates route discovery as an optimization problem. Therefore, P-routes are optimal routes that minimize route overlap, route transmission time, and route length.

[0040] An embodiment of the present invention considers a next-generation IoT network that includes a data concentrator, a set of N regular data nodes called D nodes, and a set of M prioritized data nodes called P nodes. Both the D nodes and P nodes may be single-mode or multi-mode. The data concentrator is considered a multi-mode node. Communications between single-mode nodes and between single-mode nodes and multi-mode nodes use low-speed mode. High-speed mode may only be applied to communications between multi-mode nodes. The placement of the D nodes and P nodes is random. Discovery of the decentralized D-route

[0041] An embodiment of the present invention enhances the RPL routing protocol for discovering D-routes. RPL uses DODAG Information Object (DIO) messages to discover upstream routes and Destination Advertisement Object (DAO) messages to discover downstream routes. To discover P-routes, each data node performs neighbor discovery during D-route discovery. Another node that receives a DIO message broadcast from a node is considered the node's neighbor. Once D-route discovery is complete, each data node sends neighbor information to the data concentrator via a DAO message.

[0042] Communication mode and multimode link number included in the DIO message The DIO message contains information for a node to obtain DODAG configuration parameters for parent node selection, i.e., route selection. In the present invention, the communication mode (CM) and multimode link count (MLC) are also included in the DIO message. CM = 1 indicates single-mode, and CM = 2 indicates multimode. The CM parameter can be used to calculate the MLC metric, which represents the number of multimode links along the route, i.e., the number of high-speed links along the route. For a data concentrator, CM = 2 and MLC = 0. During D-route discovery, a data node increments MLC by 1 only if the data node itself is a multimode node and the DIO message transmitter is also a multimode node. A data node selects a parent node using the RPL rank metric and the MLC metric. If parent node candidates have the same rank, the data node selects the route with the larger MLC value because the route with the larger MLC value contains more high-speed links. Rank is a distance-based metric that represents the node's position relative to the concentrator in the DODAG topology. A smaller rank value means that the node is closer to the concentrator, and a larger rank value means that the node is farther away from the concentrator.

[0043] Accumulated traffic load, neighbor node information and communication mode included in DAO messages Traffic load can have a significant impact on network performance. However, this issue has not been adequately addressed in the RPL routing protocol. In the present invention, the cumulative traffic load information of each data node is included in the DAO message. In the RPL protocol, a data node not only transmits its own data, but also relays the data of its child nodes to the default parent node. Therefore, the cumulative traffic load (ATL) of data node n is given as follows:

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[0044]

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[0045] There are different definitions of route overlap. One prior art defines link (edge) overlap as route overlap. However, this definition may underestimate route overlap. For example, in Figure 3, routes (11, 5, 1, C) and (12, 5, 2, C) overlap at node 5, but there is no link overlap between these two routes. Another prior art defines route overlap as the sum of all individual node overlaps between any two routes. This node-based overlap definition for P2P routing may overestimate MP2P route overlap. For example, because data concentrator C does not transmit data, the two routes mentioned above only have one valid node overlap at node 5. However, this definition gives two overlaps: one node overlap at node 5 and another node overlap at node C.

[0046]

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[0047] Circular routes are inefficient. Figure 4 shows examples of non-circular and cyclic routes. The route (12,6,7,3,C) 400 is a non-circular route, while the route (11,5,1,4,5,2,C) 410 is a cyclic route because 5 → 1 → 4 → 5 is cyclic.

[0048]

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[0050] Figure 5 shows the multipoint-to-point (MP2P) routing topology in the next-generation wireless IoT network. n 5 shows an example of a sub-route 500 on the P route from to the data concentrator C.

[0051] Before introducing the recursive acyclic route discovery algorithm, we first define an end node.

[0052] definition An end node is a data node where the extension of a non-circular subroute ends, i.e., the subroute cannot be extended without a cycle.

[0053] An end node is different from a leaf node. An end node is a leaf node, but a leaf node is not necessarily an end node. The determination of an end node depends on the sub-route being extended. A node may be an end node when extending one sub-route, but not an end node when extending another sub-route. In FIG. 6, when extending sub-route (10,4), node 11 is not an end node, but when extending sub-route (4,5), node 11 is an end node.

[0054]

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[0055]

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[0059] Problem (3) is a nonlinear optimization problem that can be difficult to solve, especially for large and dense networks with many acyclic routes. In fact, problem (3) belongs to the combinatorial optimization problem family and is weakly NP-hard (NP-Hard).

[0060]

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[0061] Problem (3) may be a multi-solution problem. For example, in Figure 3, routes (2,C), (6,5,1C), and (14,9,3C) and routes (2,C), (6,5,4,1C), and (14,8,3C) are two sets of routes with zero overlap. Therefore, the minimum overlap route may be further optimized based on other metrics, such as route transmission time and route length. In a network without multi-mode nodes, a route with minimum length may provide the shortest transmission time. However, in the presence of multi-mode nodes, these two objectives may yield different solutions. Minimum Transmission Time P Route Discovery

[0062]

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[0066] After concentrator C finds the preferred route for transmitting priority data, it transmits the preferred route not only to priority nodes but also to normal nodes, so that priority nodes know the P route for transmitting priority data, and all nodes in the network know the P route for relaying priority data.

[0067] A data node may transmit or relay both normal data and prioritized data simultaneously. In this case, the data node first transmits or relays prioritized data using the prioritized route, which indicates that the prioritized route has a higher priority than the normal route. Data concentrator allocates priority data transmission time

[0068] Expedited data has a higher priority than normal data. However, normal data transmissions may compete for resources with the prioritized data transmissions and delay the prioritized data. Therefore, data concentrator C can divide time into periods as shown in Figure 10. Priority Period (PP) 1000 is used only for prioritized data transmissions, and Data Period (DP) 1010 is used for both normal and prioritized data transmissions. Data concentrator C can transmit such period information to all data nodes in the network.

[0069] The above description provides exemplary embodiments only and is not intended to limit the scope, application, or configuration of the present disclosure. Rather, the following description of exemplary embodiments will provide those skilled in the art with an enabling description for implementing one or more exemplary embodiments. Various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the subject matter as set forth in the appended claims.

[0070] While the present disclosure has described the invention by way of exemplification of preferred embodiments, it is to be understood that various other adaptations and modifications can be made within the spirit and scope of the invention. Therefore, it is the object of the appended claims to cover all such variations and modifications as come within the true spirit and scope of the invention.

Claims

1. A node device used in a multi-hop heterogeneous wireless network including a single-mode node and a multi-mode node, a transceiver configured to transmit and receive messages to discover normal data routes (D-routes), the discovered D-routes forming a destination-oriented directed acyclic graph (DODAG) topology, the transceiver configured to transmit and receive normal data in the destination-oriented directed acyclic graph (DODAG) topology and to transmit and receive priority data in an optimal routing topology; a memory configured to store a computer-executable program and DODAG topology configuration parameters including a rank, a communication mode (CM), and a multi-rate link count (MLC) specified by an Internet Protocol version 6 (IPv6) routing protocol for low power and lossy network (RPL) protocol; a processor configured to execute the steps of the computer-executable program; The steps include: using the IPv6 routing protocol for low power and lossy networking (RPL) protocol to discover the D-routes of all data nodes to form the DODAG topology, the RPL protocol using DODAG Information Object (DIO) messages to perform an upstream route discovery process and Destination Advertisement Object (DAO) messages to perform a downstream route discovery process; The method includes discovering the D-route and discovering neighboring nodes, wherein the processor determines another node as a neighboring node when the processor receives a DIO message broadcast from the other node via the transceiver; A node device comprising: transmitting, using the transceiver, the cumulative traffic load (ATL) and an identifier of the neighboring node to a data concentrator via the DAO message.

2. 2. The node device according to claim 1, wherein the DIO message includes parameters specified by the RPL protocol and other parameters for selecting a parent (root) from a DODAG topology.

3. the DIO message includes a rank specified by the RPL protocol, the CM, and the MLC; The CM is used to calculate the MLC; The node apparatus of claim 2 , wherein the MLC is used to select a route, and if parent candidates have the same rank, the data node selects the route with the larger MLC.

4. the data concentrator and multi-mode data nodes set the CM to 2, and the single-mode data nodes set the CM to 1; 4. The node apparatus of claim 3, wherein if the data node is a multimode node and the transmitter of the DIO message is a multimode node, the data concentrator sets the MLC to 0 and the data node increments the MLC by 1. 【Request Item 5】 【Number 1】

6. 2. The node device according to claim 1, wherein when a data node has both normal data and prioritized data, the data node transmits the prioritized data first.

7. A node device for use in a multi-hop heterogeneous wireless network including a multi-mode concentrator, a transceiver configured to transmit a destination-oriented directed acyclic graph (DODAG) information object (DIO) message to initiate normal data route (D-route) discovery, receive a destination advertisement object (DAO) message to configure a downstream normal data route (D-route), and acquire cumulative traffic load (ATL) and neighbor node information of data nodes to perform optimal preferred route (P-route) discovery for constructing an optimal routing topology; the transceiver configured to transmit the optimal routing topology to the data nodes on the discovered preferred route (P-route) to transmit prioritized data to the multimode concentrator; the transceiver configured to receive normal data in the DODAG topology and receive the prioritized data in the optimal routing topology; a memory configured to store a computer-executable program and parameters including a communication mode (CM), the ATL, a neighbor node set, a route overlap degree (DRO), and a best preferred route (P-route) discovery; a processor configured to execute the steps of the computer-executable program; The steps include: Discovering the D-routes of all data nodes using an Internet Protocol version 6 (IPv6) routing protocol for low power and lossy networks (RPL) protocol, wherein the RPL protocol uses the DIO message to perform an upstream route discovery process and a Destination Advertisement Object (DAO) message to perform a downstream route discovery process; A node device includes: discovering an optimal preferred route (P route) by formulating a P route discovery problem as a nonlinear optimization problem to minimize route overlap calculated using the DRO; and the discovered optimal P route is further optimized to minimize route transmission time and route length.

8. The P route discovery is Discovering an acyclic route for each preferred data node using an acyclic route discovery method for identifying acyclic routes for preferred data nodes in a multi-hop heterogeneous wireless network; Finding a minimum overlap P route in a multi-hop heterogeneous wireless network by solving a nonlinear optimization problem using a minimum overlap P route finding method; Finding the set of minimum overlapping P routes that minimizes the total route transmission time of the multi-hop heterogeneous wireless network by solving a nonlinear optimization problem; and finding the set of minimum overlapping R-routes that minimizes the total route length of the multi-hop heterogeneous wireless network by solving a nonlinear optimization problem. [Request Item 9] [Number 2] [Request Item 10] [Number 3]

11. The acyclic route discovery includes: constructing a one-hop acyclic route for a preferred node that is a neighbor of the concentrator; and discovering a set of acyclic routes for a preferred node that is not a neighboring node of the concentrator using a recursive extension and extension method for recursively extending and extending each sub-route starting from the preferred node, wherein each sub-route is a partial route that has not yet reached the concentrator.

12. The recursive extension and expansion of the sub-roots are constructing one one-hop sub-route from the preferred node to each adjacent node; 12. The node apparatus of claim 11, further comprising: recursively extending and expanding each one-hop subroute until the subroute reaches a concentrator; or deleting the subroute if the subroute cannot be extended without a cycle; or expanding the subroute if the subroute can be extended to multiple extendable nodes. [Request Item 13] [Number 4] [Request Item 14] [Number 5] [Request Item 15] [Number 6] [Request Item 16] [Number 7] [Request Item 17] [Number 8] [Request Item 18] [Number 9] [Request Item 19] [Number 10]

20. The concentrator transmits the discovered optimal preferred route (P route) to data nodes on the P route for prioritized data transmission; A normal data node on the P route relays priority data using the P route; 8. The node device according to claim 7, wherein the priority node transmits or relays priority data using a P route.

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