Maintaining line of sight in wireless hybrid mobile mesh networks

Abstract

This invention provides a wireless mesh network that enables a line-of-sight (LOS) node communication environment in a wireless mesh network using unmanned aerial vehicle (UAV) platform nodes. [Solution] The wireless mesh network includes a set of data resources available to nodes through the wireless mesh network, including an environmental contour map that stores data representing the characteristics of the environment that can interfere with LOS node communications, and a line-of-sight acquisition and recovery service that operates to acquire LOS using a flight path override module by positioning the UAV node platform according to the data in the environmental contour map.

Description

Technical Field

[0001] The present invention relates to communication networks, specifically, mobile wireless mesh networks that utilize both free space optical (FSO) and radio frequency (RF) communication modes.

Background Art

[0002] Mobile mesh communication networks provide the flexibility, redundancy, and scalability of modern communication systems across various platforms and applications in diverse environments. Conventional wireless mobile mesh networks rely primarily on radio frequency (RF) communication, which is often susceptible to interference, bandwidth limitations, and range constraints. Free space optical (FSO) communication offers a high-bandwidth and secure alternative but is limited to line-of-sight (LOS) communication and is restricted by environmental conditions such as fog, rain, or smoke. Unfortunately, LOS communication between mobile nodes is vulnerable to obstructions from natural and artificial features of the environmental terrain. Therefore, having a wireless mesh network for LOS node communication is highly desirable, whereby the network can be configured to obtain, maintain, and recover LOS between nodes in an environment with terrain features that can obstruct LOS for each location (geographical position) of the mobile nodes. This objective is achieved by the present invention.

Summary of the Invention

Means for Solving the Problems

[0003] Embodiments of the present invention provide a mobile FSO / RF hybrid mesh communication network that supports nodes communicating only via FSO, only via RF, and hybrid nodes capable of both FSO and RF communication, which can predict, avoid, and recover from the loss of LOS communication between nodes due to changes in node location, which are disrupted by environmental terrain features. Embodiments of the present invention primarily relate to network nodes mounted on unmanned aerial vehicles (UAVs), particularly vertical take-off and landing (VTOL) UAVs equipped with avionic systems, of the class commonly referred to as "drones." While networks according to embodiments of the present invention are primarily aerial, with three degrees of freedom of position relative to the nodes, various embodiments may also include nodes mounted on satellites in predetermined Earth orbit, nodes installed on ground mobile vehicles (with two degrees of freedom of position), and nodes in stationary ground structures (with no degrees of freedom of position).

[0004] According to embodiments of the present invention, the location of mobile nodes can be dynamically reconfigured to provide, maintain, and recover LOS communications, optimizing link bandwidth, quality, network coverage, and / or security. [Effects of the Invention]

[0005] Embodiments of the present invention are useful in a variety of industries and sectors, including but not limited to military and defense, disaster recovery, and remote surveillance and monitoring systems, as well as in space-based communication networks.

[0006] The subject matter disclosed can be best understood by referring to the following detailed description when read in conjunction with the attached drawings. [Brief explanation of the drawing]

[0007] [Figure 1] A mobile hybrid mesh network according to one embodiment of the present invention is conceptually shown. [Figure 2]This illustrates the relocation of a mobile node in a network to avoid interference interfering with LOS communication with another node in the network, according to one embodiment of the present invention. [Figure 3] This invention illustrates the predictive positioning of a mobile node in a network to avoid interference that may disrupt LOS communication with another node in the network, according to one embodiment of the present invention. [Figure 4] This document illustrates a location configuration and resources for a mesh network for controlling a mobile UAV node platform to acquire, maintain, and recover optimal LOS between nodes, according to one embodiment of the present invention. [Modes for carrying out the invention]

[0008] For the sake of simplicity and clarity, the elements shown in the diagrams are not necessarily drawn to actual size, and the dimensions of some elements may be exaggerated relative to others. In addition, reference numbers may be repeated in the diagrams to indicate corresponding or similar elements.

[0009] Figure 1 conceptually illustrates a mobile hybrid mesh network 100 according to one embodiment of the present invention. The network 100 includes nodes 101, 103, 105, and 107, each mounted on a VTOL-operable UAV platform and equipped with a suitable avionic system, network interface, and data communication equipment for mutual communication via links 111, 113, 115, 117, and 119. While the network 100 is primarily implemented on a VTOL UAV platform, in a related embodiment, the network 100 also includes node 131 mounted on a satellite in low Earth orbit (LEO) communicating with node 103 via link 121, node 141 mounted on a ground vehicle communicating with node 105 via link 123, and node 151 at a ground station communicating with node 107 via link 125 and with satellite 131 via link 127. Furthermore, in a related embodiment, the network 100 also includes a non-VTOL UAV platform. In addition, network 100 includes connections to an external network 161 (e.g., the Internet), such as via a link 163 to a satellite-based node 131 and a link 165 to a ground station-based node 151. Although the external network 161 is not part of network 100, in various embodiments of the present invention, network 161 and network 100 can be connected and communicate with each other.

[0010] The communication modalities supported by the node through each link are consistent with Legend 180.

[0011] Within the scope of the present invention, the network 100 is primarily concerned with LOS between UAV-based nodes. Satellite-based nodes 131, ground vehicle-based nodes 141, and ground station-based nodes 151 may be involved in LOS-related transactions (e.g., to provide data and other resources), but they are not actively controlled according to the LOS control scheme described herein.

[0012] Figure 2 shows the relocation of the mobile node 101 of the network shown in Figure 1 to avoid interference 201 interfering with LOS communication between node 101 and node 103 of the network, according to one embodiment of the present invention. Three locations of node 101 are shown:

[0013] The first position 101a, which is communicating with node 103 via link 113, is shown in the first orientation 113a;

[0014] The intermediate position 101b following movement 203, which is the first segment 113a, is obstructed by structure 201 at intersection 207, causing an interruption in the LOS of link 113, thus blocking the coupled FSO communication of link segment 113a, and therefore the second segment 113b of link 113 is limited to RF communication (in fact, not only can FSO communication be blocked by obstructions such as structure 201, but RF communication can also be adversely affected); and

[0015] The final position 101c following movement 205 is calculated by the network as a compensating move to restore LOS communication between node 101 and node 103 via link 111, which is currently orientation 113d.

[0016] One consideration when selecting node 101 to perform movement 205 rather than node 103 to perform corrective movement is that (in this non-limiting example) node 103 is assigned the priority task of performing visual monitoring 211 of object 209, while node 101 is not designated to remain at any particular location at this time. Note that even if node 101 at location 101b loses LOS communication with node 103, node 101 still maintains full communication with node 107 and therefore still has access to network 100 and its data resources. Node 101 can still communicate with node 103 (via network node hopping over still active LOS FSO links and similarly via RF links), but the quality of connectivity of network 100 is reduced by the loss of LOS between node 101 and node 103. In this embodiment of the invention, LOS is readily recovered in the event of loss to restore connectivity bandwidth and quality.

[0017] In another embodiment of the present invention, loss of LOS is predicted. Figure 3 shows a predicted positioning 300 of a mobile node 101 to avoid an obstruction 201 that may interfere with LOS communication with another node in the network, according to one embodiment of the present invention. In this embodiment, mobile node 101 is initially moving in direction 203, but the network predictively calculates that if mobile node 101 continues to move in direction 203, it will move to a position where it will lose LOS with mobile node 103 due to obstruction by structure 201. The network determines that mobile node 103 has a higher priority to its current position than it has to move in its current position, and in order to prevent loss of LOS between mobile node 101 and mobile node 103, the network redirects the mobile UAV platform of node 101 to move to a new position 101d in direction 301 instead, so that it avoids structure 201 interfering with LOS between mobile node 101 and mobile node 103.

[0018] Since maintaining the Loss of Service (LOS) is generally easier than needing to reacquire it after its loss, proactively avoiding LOS loss (as shown in Figure 3) may be preferable to restoring LOS after its loss (as shown in Figure 2). Nevertheless, predicting or preventing LOS loss may not always be possible, and therefore, the network should be able to handle both LOS maintenance and recovery.

[0019] Figure 4 shows resources 400 of a mesh network 100 (Figure 1) for controlling mobile nodes to obtain, maintain, and recover optimal LOS between nodes, according to one embodiment of the present invention. As with networks in general, the mobile mesh network 100 provides several data resources for cooperative use by individual nodes and groups of nodes working together. As shown in Figure 4, the resources include data storage resources and data processing resources.

[0020] In a data storage resource of a network 100 according to one embodiment of the present invention, there is a node state data storage resource 401 containing data for all nodes, generally referred to as node(i), where i is in the range of 1 to N, usually the number of nodes in the network 100. More specifically, this data includes, but is not limited to, the following:

[0021] State (i)403 stores data indicating the health and status of node (i); including, but not limited to, the transmit / receive component status for both RF and FSO data communications, processor status and temperature, available memory, and performance issues and flight status of node (i)'s UAV platform, such as charging, avionics readiness, etc.;

[0022] Link (i) 405 stores data about the active communication links of node (i); including data transfer rate, signal-to-noise ratio, connection time, quality, and stability;

[0023] Store the global position vector (including altitude) of the UAV platform of node (i) at position (i) 407;

[0024] Store the velocity vector (relative to stationary) of the UAV platform of node (i) at velocity (i) 409;

[0025] Store the assigned positional priority of node (i) with respect to a different node (j) when the relative positions of two nodes need to be adjusted; the positional priority indicates which node, either the one of node (i) or the one of node (j), should be moved, or whether both UAVs should be moved, and if so, by what relative amount, at priority (i,j) 411;

[0026] Store the data description of the space around node (i) that has LOS to and from node (i) at LOSmap(i) 413; Nominally, this is from the perspective of a spherical coordinate system, specifying the θ and φ angular directions in which node (i) has LOS to the outer periphery of network 100, including the linear range r of the LOS, where any obstructive features of the environment are limited within r, and in that case r is simply the straight-line distance from node (i) to the obstructive feature.

[0027] Note that the r, θ, and φ spherical coordinates can be easily converted to Cartesian coordinates by well-known and well-supported devices, and in the related embodiments of the present invention, by the coordinate data processing resources of network 100 (not shown), and vice versa.

[0028] In addition to the node-related data storage resources listed above, embodiments of the present invention provide the following data storage resources related to network 100 as a whole:

[0029] The environmentContourMap 421 stores data representing the environment of network 100, including all natural features of the environment (e.g., hills and mountains, valleys, dunes, cliffs, deep fissures, bodies of water, trees and forests, etc.) and artificial features (e.g., buildings, bridges, elevated roads, walls, towers, chimneys, signs, monuments, and other structures), in particular features that can obstruct the line of sight (LOS). The term “contour map” as used herein refers to a topographic map that includes contour lines representing the intersections of an (imaginary) elevation surface with the topography and other features of the environment. Associated with each contour line is the altitude of the elevation surface on which that contour line is located. According to embodiments of the present invention, the contour map is rendered as a data object in a format compatible with all of the individual resources 400 of network 100. Specifically, the data processing resources of network 100 can convert part or all of environmentContourMap 421 from its native format into a three-dimensional wireframe data representation of the environment in which network 100 operates.

[0030] According to a related embodiment, this wireframe representation is data equivalent to the environmentContourMap 421, and in another related embodiment, the environmentContourMap 421 is rendered directly into a 3D wireframe data format.

[0031] linkedNodeLOSmap(i,j)423 is a submap of environment data within environmentContourMap 421 that contains the region of the environment corresponding to the common line of sight for both node (i) and node (j), in which case node (i) and node (j) are connected or intended to be connected via an FSO communication link. In geometric set terminology, linkedNodeLOSmap(i,j)423 is the intersection of LOSmap(i)413 and LOSmap(j)413.

[0032] availableLOSmap(i)425 is another submap of environment data within environmentContourMap 421, containing the region of environment corresponding to the line of sight common to node (i) and to all other nodes to which node (i) is connected or intended to be connected via FSO communication links. In geometric set terminology, availableLOSmap(i)425 is the iterative intersection of LOSmap(i)413 with all LOSmap(j)413, in which case (j) extends to all values, and therefore node (i) and node (j) are connected or intended to be connected together via FSO communication links. The significance of availableLOSmap(i) is that it shows all locations where node (i)'s UAV can be positioned and still maintain all existing and intended LOS FSO communication links.

[0033] According to one embodiment of the present invention, all data storage resources for network 100 are continuously updated in real time. This includes, but is not limited to, node state data resources 401 (state(i)403, link(i)405, location(i)407, speed(i)409, priority(i,j)411, LOSmap(i)413), as well as environmentContourMap 421 and linkedNodeLOSmap(i,j)423, in addition to availableLOSmap(i)425. Thus, any query made at any time over network 100 against any of these elements in data storage will always return a currently valid data response.

[0034] According to embodiments of the present invention, among the data processing resources of network 100, there is a line-of-sight acquisition and recovery service 431 which receives an input argument (i,j) that designates both node (i) and node (j) as nodes that need to acquire or recover LOS between them. The line-of-sight acquisition and recovery service 431 utilizes other data processing resources (as disclosed herein) together with a flight path override module 447 (described in detail below) to position one or more UAV node platforms to achieve LOS acquisition or recovery between node (i) and node (j). Specifically, the line-of-sight acquisition and recovery service 431 makes the flight path override module 447 available to maintain LOS between node (i) and node (j) in response to a predicted loss of line of sight warning (as described below). In a relevant embodiment, if nodes (i) and node (j) currently have LOS connectivity, the line-of-sight acquisition and recovery service 431 confirms this condition and cancels any active predicted loss of line of sight warnings.

[0035] According to an embodiment of the present invention, among the data processing resources of network 100, there is a location prediction service 433 which receives an input (i) specifying a UAV of node (i) and calculates the predicted future vector position of the UAV based on the current vector position of node (i) extrapolated according to the current vector velocity of node (i) over a specified time interval Δt. It should be noted that in practice, UAVs can accelerate rapidly and change direction rapidly, and therefore the velocity of node (i) may only be valid for short periods in such cases. Nevertheless, the location prediction service 433 can provide useful information in cases where the velocity is substantially constant over a period of time.

[0036] According to an embodiment of the present invention, among the data processing resources of network 100 is a predicted collision warning service 435. Based on data provided by the location prediction service 433 for all nodes, along with data provided by environmentContourMap 421, the predicted collision warning service 435 provides warnings of predicted collisions between one or more nodes and warnings of predicted collisions between nodes and environmental features (such as buildings). As detailed below, the warnings are broadcast via network 100.

[0037] According to an embodiment of the present invention, among the data processing resources of network 100, there is a line-of-sight loss notification service 437 which continuously queries the nodes of network 100 for their connection status and issues a notification if the LOS FSO communication connection is unintentionally lost. The notification includes the (i,j) identification of the currently disconnected node. As detailed below, the notification is broadcast via network 100.

[0038] According to embodiments of the present invention, among the data processing resources of network 100, there is a predicted line-of-sight loss warning service 439. Similar to the predicted collision warning service 435, the predicted line-of-sight loss warning service 439 calls a location prediction service 433 for all nodes i that currently support LOS FSO communication and, together with the location prediction service 433, queries the availableLOSmap(i) data resource to determine whether one or more of the nodes i are predicted to leave the area that supports LOS connections with one or more other nodes. If the predicted location of node i may be outside the LOS area with another node j, the predicted line-of-sight loss warning service 439 transmits a predicted line-of-sight warning in that sense via network 100, such as by broadcast, as described below. In embodiments of the present invention, if there is a predicted line-of-sight loss warning, the line-of-sight acquisition and recovery service attempts to maintain the LOS and prevent the loss of LOS. The term "acquire" and similar terms, as used herein in the context of LOS, refer not only to initially establishing an LOS, but also to maintaining an LOS by preventing a loss of an LOS, and to re-establishing an LOS after a loss of an LOS.

[0039] According to an embodiment of the present invention, the data processing resources of the network 100 include a node and link query service 441, which provides convenient access to a data resource 401 relating to data associated with all nodes of the node network 100.

[0040] According to an embodiment of the present invention, among the data processing resources of the network 100, there is a network query service 443 which provides convenient access to all data resources associated with the network 100.

[0041] According to an embodiment of the present invention, among the data processing resources of network 100, there is a map query service 445 which provides convenient access to all map-related data storage of network 100.

[0042] According to embodiments of the present invention, among the control resources mounted on the node UAV platform, there is a flight path override module 447 which receives an input having a velocity vector to override and replace the current UAV velocity. If this request comes from the line of sight acquisition and recovery service 431, the flight path override module 447 queries the node and link query service 441 to determine whether the node(i) priority allows its current flight path to accept the override request, and if so, redirects the UAV's avionics control at the replacement velocity. If this request comes from the predicted collision warning service 435, in embodiments of the present invention, the override is applied regardless of the node(i) priority.

[0043] According to embodiments of the present invention, among the network management resources of network 100, there is a network resource allocation service 449 which allocates each of the resources of network 100 (including itself) to a specific node. In a related embodiment, each node has sufficient data storage, program storage, and data processing capabilities to accommodate all of the network resources 400. This provision is made for the purpose of redundancy and fault tolerance so that network 100 will always have the required data resources and data processing resources necessary for proper functioning. However, even if each node can separately hold the hardware, firmware, and software for all network data resources, it is not necessary, or even desirable, for all nodes to provide all data resources and all data processing resources. With the special exception of the flight path override module 447 (which is a component of each individual node), distributing the operation of data resources and data processing resources across the network is more efficient and less burdensome while still providing the redundancy and backup necessary to ensure that network 100 is robust and fault-tolerant. The specific distribution of resources is performed by the network resource allocation service 449, which ensures sufficient redundancy and emergency backups. For example, if a particular node leaves the network (e.g., by becoming inoperable), the network resource allocation service 449 reallocates its resources from the currently missing or non-functional node to another suitable node. For this reason, the network resource allocation service 449 itself should operate redundantly on as many nodes as possible without placing an excessive load on network 100.

[0044] According to embodiments of the present invention, all interactions between data storage resources and data processing resources in network 100 are performed in accordance with the network and broadcast messaging protocol 471. In this schema, a data processing resource invokes another data processing or data storage resource by placing a message on the network. The node assigned to perform the requested data storage / retrieval service and / or data processing service then returns a response to the message sender. Where there are redundant nodes, there is a priority order, which the redundant node(s) then wait before responding, and only respond if the preferred node for that service has not responded. In addition to sending messages to specific nodes, the network and broadcast messaging protocol 471 also simultaneously provides general broadcasts of notices and warnings to all nodes.

[0045] In this way, maintaining LOS connectivity according to the embodiments of the present invention is reliably performed via the network 100, which operates as an organic unit, by evenly distributing various services and their requested sub-services across the network 100.

Claims

1. A wireless mesh network for line-of-sight (LOS) node communication, wherein the wireless mesh network is Multiple mobile nodes in an environment, each mounted on a vertical take-off and landing (VTOL) capable unmanned aerial vehicle (UAV) platform, and including a flight path override module that operates to change the speed of the UAV platform, wherein at least two nodes of the wireless mesh network have communication capabilities limited to LOS, A set of data resources available to nodes through the aforementioned wireless mesh network, An environmental contour map storing data representing the characteristics of the environment that can interfere with LOS node communication, and Line of Sight Acquisition and Recovery service that positions the UAV node platform according to the environmental contour map data and operates to acquire LOS using the flight path override module. A set of data resources, including A wireless mesh network, including one.

2. The wireless mesh network according to claim 1, wherein at least two of the plurality of nodes communicate via free-space optical (FSO) communication.

3. The wireless mesh network according to claim 2, wherein at least two of the plurality of nodes further communicate via radio frequency (RF) communication.

4. The aforementioned set of data resources is The wireless network according to claim 1, further comprising a line-of-sight loss notification service that operates to communicate line-of-sight loss notifications, the line-of-sight acquisition and recovery service recovers the LOS in response to the line-of-sight loss notification.

5. The aforementioned set of data resources is A location prediction service for predicting the location of the UAV node platform, A predicted line-of-sight loss alert service that receives predicted UAV locations and operates to communicate line-of-sight loss alerts, and It further includes, The line-of-sight acquisition and recovery service maintains the line of sight in response to the line-of-sight loss warning. The wireless network according to claim 1.

6. The aforementioned set of data resources is The LOS map for a node further includes data relating to the space surrounding the node, up to the outer perimeter of the network, where there are LOS to and from the node. The wireless network according to claim 1.

7. The aforementioned set of data resources is The system further includes a linked node LOS map for a pair of nodes connected by an LOS data communication link, wherein the linked node LOS map stores data relating to the area of ​​the environment corresponding to a common line of sight to both nodes of the pair. The wireless network according to claim 6.

8. The aforementioned set of data resources is LOS maps available for nodes The available LOS map further includes storing data relating to all locations that the UAV platform of the node can locate while still maintaining LOS with all other nodes that have LOS communication links to the node. The wireless network according to claim 7.

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