Patent Application
20230379239
The disclosure herein relates to a method for establishing a communication through multiple distinct communication paths deployed over different network operators, a system for establishing a communication through multiple distinct communication paths deployed over different network operators and a vehicle system.
Vehicles, in particularly unmanned aerial vehicles, that are either remotely piloted and/or rely on a high level of autonomy may be equipped with a communication system to contribute to achieving a desired design assurance level for specific vehicle functions, reducing the on-board autonomy system complexity by the help of ground system elements. Such a communication system may be composed of airborne and ground segments that connect the flying vehicle and a ground station, e.g. either air traffic control or aircraft operation center. Ground sub-networks providing availability higher than 99.999% exist, but similar values are not known to be delivered by network operators for the wireless segment, for example SATCOM service.
It is known to use multi-technology/multi-link communication networks for a communication with improved availability and safety. However, using commercially available communication paths cannot guarantee that a single failure of network equipment will not simultaneously affect multiple communication paths, as network operators usually do not share topology and routing/configuration information of their networks.
It is thus an object of the subject matter herein to disclose a method for establishing a communication through multiple paths with an improved availability and a reduced failure probability.
This object is met by a method for establishing communication. Advantageous embodiments and further improvements may be gathered from the following description.
A method for establishing a communication through multiple distinct communication paths deployed over different network operators is disclosed, comprising the steps collecting of location information of network nodes of several available distinct paths between a source node and a destination node, comparing location information of the network nodes to identify possibly co-located network nodes, determining of path segment lengths of consecutive path segments between the nodes of each path, estimating whether path segments of the paths intersect based on the locations of the network nodes and the path segment lengths, selecting of multiple paths that do not comprise intersecting path segments and/or co-located network nodes and/or co-sharing path segments, and establish a communication between the source node and the destination node over both selected paths.
For explaining the concept according to the disclosure herein, the above-mentioned features as well as relevant aspects of communication paths are discussed in the following. Network resilience is defined as the ability of a network to provide and maintain a predefined level of service availability in the face of unexpected events and faults in its nominal operation. To avoid service disruption by a single source of failure and thereby to increase its availability, the underlying infrastructure is usually configured to operate over multiple disjoint communication routes. Still, for example if overlay links of these disjoint paths are routed over the same network resource, e.g. an optical fiber duct, they will fail at the same time upon the event of the resource, e.g. an outage caused by an excavator cutting the fibers within the duct. Especially, if a service is designed and implemented over multiple network operators, in order to meet the availability requirements, it cannot be guaranteed that single failure events will not affect the service of all operators at the same time. Examples include, but are not limited to, services routed through fibers owned by different operators that are, however, routed through the same tunnel or over the same bridge.
The method according to the disclosure herein allows to ensure that service availability can be met in the event of network outages that can affect several of the network operators involved in the service deployment in order to support flying vehicle autonomy and a superior safety of flight. However, the method may also be used for other communication applications with a high demand of availability.
To provide a highly available communication service, exemplarily over a mix of wireless and wired links, disjoint path routing approaches are used to cope with multiple failure scenarios. This is achieved using a set of k link or node disjoint paths, wherein k>=2. If information about Shared Risk Resource Groups or shared risk groups (SRGs) are available, a calculation of an SRG-disjoint path pair allows to protect a connection against a common failure of a set of resources in any SRG. Also, if such information is not provided, the method according to the disclosure herein is capable of detecting such shared risks for communication paths deployed over different network operators.
The availability of a system is based on the operation of a set of distinct subsystems that connected to obtain an intended function. Reliability is defined as the probability that a system performs its intended function for a specified period of time under a given conditions and the availability is the probability that a system can be used at a given time instant. The availability (A) is a feature of restorable systems and its components and it is defined as:
where MTTF is the mean time to failure and MTTR is the mean time to repair.
The availability of an end-to-end service from a source to a destination is calculated based on the availability values of the subsystems/components that compose the end-to-end path. If a service is deployed over multiple network operators, it is usually impossible to identify elements of the information paths that can fail simultaneously, as operator network configuration, routing strategies and underlying physical topology are not disclosed. The method according to the disclosure herein is capable of identifying shared risks in multi-operator environment. It is assumed that in intermediate network nodes network functions (NF) are deployed.
NF or network function virtualization is a network architecture concept that uses the technologies of IT virtualization to virtualize entire classes of network node functions into building blocks that create communication services. For example, the fifth generation (5G) mobile networks introduce a new paradigm of network automation that is enabled and can be implemented by cloud computing and network function virtualization (NFV). On the one hand, computation resources are available where needed and they are coming closer to the end user through Multi-access Edge Computing (MEC) technology. On the other hand, NFV enables the flexible and on-the-fly creation and placement of both application and network functions, aiming at satisfying the diverse application requirements and optimizing the management of the heterogeneous (network, computational and storage) resources.
The Open Network Automation Platform (ONAP) is the part of the larger Network Function Virtualization/Software Defined Network (NFV/SDN) ecosystem that is responsible for the efficient control, operation, and management of Virtual Network Function (VNF) capabilities and functions. It specifies standardized abstractions and interfaces that enable efficient interoperation of the NVF/SDN ecosystem components. It is supported by main mobile operators, is deployed in several commercial cellular networks, and multiple vendors provide ONAP support and integration in their products. The ONAP platform enables product/service independent capabilities for design, creation, and runtime lifecycle management of resources in the NFV/SDN environment. These capabilities are provided using two major architectural frameworks, i.e. a Design Time Framework to design, define and program the platform, and a Runtime Execution Framework to execute the logic programmed in the design environment. The platform delivers an integrated information model based on the VNF package to express the characteristics and behavior of these resources in the Design Time Framework. The information model is utilized by Runtime Execution Framework to manage the runtime lifecycle of the VNFs. The management processes are orchestrated across various modules of ONAP to instantiate, configure, scale, monitor, and reconfigure the VNFs using a set of standard APIs provided by the VNF developers.
It is advantageous to deploy network functions in selectable nodes. The network functions may be able to generate and provide location data via an application programmable interface (API) through Global Navigation Satellite System (GNSS). This may be done in the method step of collecting of location information of the network nodes. This allows to conduct a primary check whether intermediate nodes along multiple communication paths are co-located. If this is the case, they may possibly share resources, which may decrease the overall availability. By comparing location information of the network nodes, it is possible to rule out co-located and probably identical nodes or nodes that are integrated into identical network equipment. By ruling out these co-located nodes, the availability of the selected communication paths is increased, and a single failure of a network equipment does not affect multiple communication paths
Every communication path comprises at least one path segment. The path segment is to be understood a section or part of the path that is located between two consecutive nodes. In a simple case, the start and destination nodes merely enclose a single path segment. However, it is likely that with expected distances between the start and destination nodes a plurality of intermediate network nodes are present as well as a plurality of path consecutive segments enclosed by consecutive pairs of nodes.
According to the disclosure herein, the path segment lengths are determined. In combination with knowledge about the location of the nodes of the distinct paths it can be estimated whether path segments intersect, which may be an indication of at least partially sharing the same network equipment. The distance between two nodes may exemplarily be estimated based on the location data, e.g., using Euclidean distance or an Earth-surface-based approximation. However, also a transmission delay measurement may be performed, from which an estimation of the physical route length can be calculated, e.g., an upper bound is obtained by assuming propagation delay only.
To establish a highly available communication over multiple distinct paths, suitable end-to-end routes can be set up by selecting node pairs that are surely diverse, i.e. that do not contain co-located nodes and shared or intersecting path segments. In an advantageous embodiment, the collecting of location information of network nodes comprises querying the respective nodes for location information. As explained above, the network nodes may be equipped with an API that allows to retrieve desired information. If the available network nodes comprise geo-information, it is simple to receive and collect location information for further proceeding in the method.
In an advantageous embodiment, the determining of path segment lengths comprises measuring a transmission delay along the respective path segment. The distance between two consecutive nodes in a path segment is determined by the product of propagation delay and propagation speed in the signal transferring medium used in the path segment. For example, the propagation speed in a copper cable is about 2.3×108 m/s, while in an optical fiber it is about 2.0×108 m/s.
In an advantageous embodiment, determining of path segment lengths comprises calculating a distance between consecutive nodes of the respective path segments. This may be conducted alone or in combination with measuring the transmission delay. In a simple case, the path segments are completely straight. If two distinct path segments are analyzed that are directly connected to a start node or a destination node, it is conceivable that they are diverse if the measured path segment lengths equal the calculated distances between the respective nodes.
In an advantageous embodiment, the method further comprises calculating a ratio of the sum of distances between a common node and multiple connected, distanced nodes and the sum of respective path segment lengths, wherein it is assumed that the path segments are non-sharing if the ratio is greater than 0.9. Hence, as explained above, the measured path segment lengths equal or almost the calculated distances between the respective nodes and co-sharing path segments can be ruled out. The ratio may furthermore be in a range of 0.85 to 0.95.
In an advantageous embodiment, the selecting of multiple paths additionally comprises determining a total path length and/or expected signal attenuation and/or signal latency as a cost factor for each available path and minimizing the cost factor when selecting the multiple paths. Besides the availability itself also a communication quality can be maximized through a cost-optimizing function.
In analogy, the disclosure herein relates to a system for establishing a communication through multiple distinct communication paths deployed over different network operators, comprising a start node and a destination node, wherein each of the start node and the destination node comprises at least one communication device adapted for establishing a communication between the source node and the destination node over multiple paths, wherein each of the start node and the destination node comprises a control unit, wherein at least one of the control units is designed for collecting of location information of network nodes of several available distinct paths between the source node and the destination node, comparing location information of the network nodes to identify possibly co-located network nodes, determining of path segment lengths of consecutive path segments between the nodes of each path, estimating whether path segments of the paths intersect based on the locations of the network nodes and the path segment lengths, and selecting multiple paths, through which the communication is to be established, that do not comprise intersecting path segments and/or co-located network nodes and/or co-sharing path segments.
The control units preferably are capable of connecting to the network nodes through the above-identified API that allows to interact with network functions of the network nodes in order to conduct the above-identified steps of the method.
In an advantageous embodiment, the collecting of location information of network nodes comprises querying the respective nodes for location information through the at least one control unit.
In an advantageous embodiment, the determining of path segment lengths comprises measuring a transmission delay along the respective path segment through the at least one control unit.
In an advantageous embodiment, the determining of path segment lengths comprises calculating a distance between consecutive nodes of the respective path segments through the at least one control unit.
In an advantageous embodiment, the at least one control unit is further adapted for calculating a ratio of the sum of distances between a common node and multiple connected, distanced nodes and the sum of respective path segment lengths, wherein it is assumed that the path segments are non-sharing if the ratio is greater than 0.85 to 0.95 and particularly greater than 0.9.
In an advantageous embodiment, the selecting of multiple paths additionally comprises determining a total path length and/or expected signal attenuation and/or signal latency as a cost factor for each available path and minimizing the cost factor when selecting the multiple paths.
The disclosure herein further relates to a vehicle system comprising at least one vehicle, at least one communication station and at least one system according to the above description, wherein the start node is arranged in one of the vehicle and the communication station, and wherein the destination node is arranged in the other one of the vehicle and the communication station.
In an advantageous embodiment, the vehicle is an aircraft, and wherein the communication station is a ground station.
In the following, the attached drawings are used to illustrate example embodiments in more detail. The illustrations are schematic and not to scale. Identical reference numerals refer to identical or similar elements.
The method 2 comprises the steps of collecting 4 of location information of network nodes of several available distinct paths between a source node and a destination node, comparing 6 location information of the network nodes to identify possibly co-located network nodes, determining 8 of path segment lengths of consecutive path segments between the nodes of each path, estimating 10 whether path segments of the paths intersect based on the locations of the network nodes and the path segment lengths, selecting 12 of multiple paths that do not comprise intersecting path segments and/or co-located network nodes and/or co-sharing path segments, and establishing 14 a communication between the source node and the destination node over both selected paths.
The collecting 4 of location information of network nodes may comprise querying 16 the respective nodes for location information. The determining 8 of path segment lengths may comprise measuring 18 a transmission delay along the respective path segment and/or calculating 20 a distance between consecutive nodes of the respective path segments.
In addition, the method may further comprise calculating 22 a ratio of the sum of distances between a common node and multiple connected, distanced nodes and the sum of respective path segment lengths, wherein it is assumed that the path segments are non-sharing if the ratio is greater than 0.85 to 0.95 and in particular greater than 0.9. This may be conducted in the step of selecting 12 multiple paths. Also, the selecting 12 of multiple paths may additionally comprise determining 24 a total path length and/or expected signal attenuation and/or signal latency as a cost factor for each available path and minimizing 26 the cost factor when selecting the multiple paths.
The availability of the communication from the source node 32 to the destination node 34 is calculated based on availability values of the subsystems or components that compose the respective paths 28 and 30. In this example, data is transported from the source node 32 to the destination node 34 over the two disjoint paths 28 and 30. Assuming that the node availability is 1, i.e. 100%, the overall service availability A is calculated as follows:
A=1−(1−A28)·(1−A30)=A28+A30−A28·A30
wherein where A28=A28a·A28b and A30=A30a·A30b·A30c. The subscript numbers indicate the respective paths or path segments.
For simplicity, the path segments 28a, 28b, 30a, 30b, 30c are assumed to have the same availability of 0.999. The total end-to-end service availability when transferring information from the source node 32 to the destination node 34 simultaneously on both communication paths 28 and 30 is 0.99999. For the same network shown in
A=(1−(1−A28a)·(1−A30a·A30b))·A28b/30c
If using the same common path segment availability of 0.999 for every path segment, the service end-to-end availability is 0.9989, which is two orders of magnitude lower compared to the case, when the path segments are not affected by the same risk. This shows the importance of identifying common risks, when provisioning high availability services.
The vehicle 38 uses a direct air to ground (DA2G) communication service deployed using dual-connectivity, via both network operators towards the communication station 40, which may be referred to as a base station, a ground assistant, remote pilot station or air traffic control.
If both communication paths from the vehicle 38 to the communication station run through the first base station 42, the service can be affected if a failure happens at the shared resource of the first base station 42, e.g. power outage. Thus, to guarantee the high availability of the service, this shared risk should be identified and only the first communication path 46, operated by a first operator OP1, and the third communication path 50, operated by a second operator OP2, should be used. As mentioned in combination with
In
A suitable binary matrix for evaluating the path segments may be as follows, wherein the value “1” stands for non-sharing path segment and “0” for all other states. The path segments 92 and 94 are not clearly distinct, such that a “0” is entered for the combinations of path segments 92 and 94. However, all other path segments 84-90 and 96-98 are likely non-sharing.
The source node 32 and the destination node 34 have to be connected with two distinct paths to increase the availability. If an objective function with cost minimization without constraints is used, i.e. without excluding possibly shared path segments, a first path, i.e. a working path, will be a path running from the start node 32 to node 78 through segment path 88, afterwards to node 82 through the path segment 94 as well as to the destination node 34 through path segment 98, with a cost value of “60”. A protection path would result in a path running from the start node 32 to node 76 through segment path 86, afterwards to node 80 through the path segment 92 as well as to the destination node 34 through path segment 96, with a cost value of “70”.
However, if the same objective function is used, but the constraint is added to avoid shared path segments, the working path will be start node 32-node 78-node 82-destination node 34 with a cost value of “60”. The protection path would be start node 32-node 74-destination node 34 with a cost value of “100”.
Still further, regarding the estimation stated in connection with
i.e. if the sum of path segment lengths are almost identical to the sum of node distances, it may be assumed that the first and second path segments 104 and 106 are diverse. As explained above, this assumption may apply to a ratio greater than 0.85 to 0.95 and in particular greater than 0.9.
While at least one example embodiment of the invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the example embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a”, “an” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22174623.3 | May 2022 | EP | regional |
