JP2001251358A - Method and system for dynamically updating display of work site and propagation model - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a system that revises in general a land form of a work site, that is, to provide a method and a system that dynamically updates display of the work site subjected to a civil engineering work changing the land form of ground surface and that dynamically updates a propagation model of a communication signal in response to the updated display of the work site. SOLUTION: This invention includes the method for dynamically updating a propagation model of a communication signal in an area subjected to a civil engineering work changing the land form of ground surface, and this method includes a step where a ground surface map of the area is dynamically updated as a function of a civil engineering work, and a step where the propagation model is dynamically updated in response to the updated ground surface map. This invention also includes a device that dynamically updates the propagation model of the communication signal in the area subjected to the work of a mobile ground surface revision machine able to change the land form of the ground surface, and the device includes a circuit that stores the ground surface map representing a preceding ground surface before it is subjected to the revising work by the mobile land form revising machine, a circuit that dynamically updates the ground surface map when the ground surface is subjected to the revising work by the mobile land form revising machine, and a circuit that dynamically updates the propagation model in response to the updated ground surface map.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates generally to a method and apparatus for altering the terrain of a work site, and more particularly to
A method for dynamically updating a display of a work site undergoing civil works such as changing the surface terrain, and dynamically updating a communication signal propagation model in response to the update of the display of the work site; and Related to the device.

[0002]

2. Description of the Related Art When partially or fully autonomous or manually operated mobile machines are developed at a work site, a modest way to supervise certain tasks and to plan the movement of the machines. Lots of updates are needed to prepare the time. In some situations, many devices need to work with each other, and information about the activities and movements of each device, other objects in the work environment, and changes made to the work environment and site terrain can be obtained. Must be communicated. As worksites become more complex and more machines are used, efficient means of transmitting and receiving data between machines is needed. Further, the information to be communicated is inherently diverse. For example, the system must support priority data and give priority to data belonging to operations essential to the service. Some of the operations are very interactive and may require very little system latency. In addition, the required frequency band has a large variation of several bytes per second to several hundreds of thousands of bytes per second or more.

[0003] Currently, wireless mobile communication systems are configured to switch between paths or networks in response to detecting loss of signal quality. For example, cellular systems switch base stations when the signal level drops below a certain level, such as when a mobile node moves from one base station area to another. In some cases, the drop in signal level occurs as soon as connection is lost before handover to another base station is complete. For example, mobile weight machine communication systems that operate partially or completely autonomously cannot afford to lose valuable data during this transition, and high quality communication must be maintained at all times. Therefore, it is necessary to have a mobile communication system with means for compensating for deterioration of communication signals and preventing information loss.

[0004] In order to use the available frequency bands most effectively, a communication system should ideally have the ability to select from several overlapping wireless networks the most appropriate network for a particular application. It is a target. It is also preferable to switch networks immediately before the mobile node moves from one network to the other to prevent loss of communication signals. This requires the ability to anticipate the handoff before it is delivered and inform the network when it discovers that the handover is imminent. The ability to predict hand-overs is a task where machines are scattered over long distances due to a large amount of interference from complex surfaces including hills, foliage, deep trenches, holes, tunnels and buildings. It must be reliable in the environment. Radio frequency (R) in areas with irregular terrain and buildings such as deep canyons, steep hills, and high walls
F) Wave propagation requires consideration of factors such as reflection, diffraction, multipath and scattering effects. The signal strength of the RF signal can fluctuate significantly due to small movements in such areas. Since wireless networks are generally made more reliable by adding error detection and correction functions without regard to low processing power and long latency, the reliability of the system needs to be balanced with the speed.

Conventional hierarchical data such as the Internet
In a network, a routing protocol is tied to the logical location of a node in the network. When a packet is sent, it includes the address of the destination host computer in its header. Intermediate nodes in the path between the source and the destination examine the destination address and determine how to route the packet based on the network component of the destination address.
This allows intermediate nodes to forward packets to the network on which the destination host is located without knowing the exact location of the destination host. As the packet travels along the path, intermediate nodes near the destination have information about the exact location of the destination and forward the packet accordingly. One advantage of this type of scheme is that hosts need to know the location of some networks with nodes instead of the location of all nodes in the network.

[0006]

This conventional network assumes that the host is much more stationary. With a lightweight, battery-powered mobile computer using wireless technology, a user can move around while maintaining a connection. However, when nodes move away from their "home" network, the scheme breaks. For example, when a mobile computer with an address belonging to network A moves to network B, packets destined for the mobile computer will still be sent to network A indicated by the network component at that address. All packets destined for the mobile computer are sent to the home computer
Lost while away from the network. The limitations of traditional routing methods limit the mobility of these computers,
It consists in limiting them by confining them to a single network.

[0007] In addition, when the work site is changed, it is also necessary to coordinate many terrain modification machines as they operate within the work site. In particular, it is advantageous to be able to update the ground map and prepare the updated information in each machine. When the information is updated, it may also be necessary to update the communication propagation model. Accordingly, the present invention is directed to overcoming one or more of the problems set forth above.

[0008]

SUMMARY OF THE INVENTION One aspect of the present invention provides
A method of dynamically updating a communication signal propagation model in an area undergoing civil engineering work that changes the surface terrain, the method dynamically updating a ground map of the area as a function of the civil engineering work. And dynamically updating the propagation model in response to updating the ground map. Another aspect of the present invention is an apparatus for dynamically updating a communication signal propagation model in an area subject to a mobile terrain changing machine capable of changing the surface terrain, the apparatus comprising a mobile terrain changing machine. Means for storing a surface map representing the previous surface of the surface being modified by the vehicle, means for dynamically updating the surface map when the surface is modified by a mobile terrain changing machine, and responding to the surface map update Means for dynamically updating the propagation model.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Overview) A wireless mobile communication system of the present invention is provided between two or more communication nodes in an area having a plurality of communication nodes and one or more communication network technologies. A method and apparatus for communicating is provided. Communication nodes can be mobile or stationary. A smart switching system incorporates location information and RF wave propagation calculations for the selected communication network. An environmental map containing the terrain of the area's surface and structures,
Used at selected time intervals to create RF propagation and communication models for signals generated by selected communication nodes and networks in the area, as well as locations and characteristics of potential sources of electromagnetic interference. RF propagation and communication models provide predictions of signal quality everywhere, at a given location. Using these inputs, each communication node of the network of the present invention predicts where it is in the future, whether its location is reachable via a particular wireless network, and what the signal quality is at that location. can do. The network can then be ready for handover between base stations or networks with the desired signal quality, thus minimizing delay and incurred costs. To support mobile nodes, communication protocols such as the standard Internet Protocol known as Mobile IP are used, allowing nodes to change their location within the network without changing their addresses. When a mobile node moves from one network to another, the home agent is the only node in the network that keeps track of the mobile node's location and routes packets to this location. The system of the present invention also directly
Enable communication between peers. When the two nodes are each within range of each other, the user can communicate directly without any assistance from any central router. When the two nodes are each out of the other's coverage area, the user can communicate by using the other mobile node between them to forward their packets, ie, these Intermediate nodes are dynamically used as routers to form temporary networks. By providing this capability, the system can support a very large number of mobile nodes. The system further provides support for a variety of network traffic types, including data intensive file transmission, time-first emergency data, real-time audio data, fixed frequency band data, and periodic location data. The type of service required for that traffic is also considered to meet the special requirements of the various communication nodes, facilitating the interaction of different user applications.

(Mobile IP) The Mobile IP (Internet Protocol) standard was developed to provide for host mobility over the Internet. As described herein, Mobile IP implementation is based on IP version 4
Based on the (IPv4) protocol standard. Mobile IPv
4 allows IPv4 packets to be transparently routed to mobile nodes on the Internet. Also IP
There is also a new version of IP known as Version 6 (IPv6), while there is also a Mobile IP extension known as Mobile IPv6. Both Mobile IPv4 and Mobile IPv6 can be used for the device. In conventional IP routing, if a node moves to another network, the packets destined for it will no longer be reachable. In order for a node to be able to communicate on the new network, it needs to change its IP address. This makes it impossible to maintain a connection when a node changes places. Mobile IP is a routing scheme that does not require a mobile node to change its IP address as it moves. Instead, each mobile node is identified by a single IP address, regardless of the location of the current point belonging to the network.

[0011] Understanding Mobile IP requires familiarity with the following concepts. Mobile node: A node that moves from one network to another. Mobile nodes perform Mobile IP to maintain communication with other nodes. Communication node: A node with which a mobile node is communicating. A communication node may be either a stationary node or another mobile node. Home address: An IP address that is assigned to a mobile node and that does not change regardless of whether the node belongs to a network. Home network: Each mobile node has a home network. This is the network to which conventional IP routing would send packets addressed to the home address when the mobile node was in its home network. Conventional IP routing can send a packet to a mobile node using its home address. Foreign network: Any network other than the mobile node's home network. Home Agent: An agent located on the mobile node's home network. The home agent keeps track of the location of the mobile node and forwards packets to the mobile node when the mobile node is away from home. External agent: An agent located on an external network. The foreign agent helps the mobile node to register with its home agent and also helps to forward forwarded packets to the mobile node.

[0012] Care-of address: IP address on the external network to which the home agent forwards the packet. The care-of address can be either the IP address of the foreign agent or a local address obtained on the foreign network. Dynamic Host Configuration Protocol (DH
Protocols such as CP) can be used for this. The former type of care-of address is called a foreign agent care-of address, and the latter is called a co-located care-of address. Packet interception: This is the process by which the home agent receives a packet addressed to one of its mobile nodes. This is due to the use of the "surrogate" Address Resolution Protocol (ARF) at the home
Executed at P. The home agent answers the address resolution request for the mobile node's IP address from another node on the home network using the proxy ARF,
Gives the home agent's connection layer address as if it were the mobile node's address. The node requesting the address then uses the home agent's concatenated layer address to send the packet to the mobile node, allowing the home agent to receive the packets and forward them to the mobile node's current location. I do. Coupling Repository: The communication node can maintain a repository of care-of addresses for the mobile node to determine where to send packets destined for the mobile node. Binding Update: A message used to update the binding repository of a communication node. Registration lifetime: The period during which registration of a mobile node on an external network is valid. It is also the period during which the binding update is valid.

FIG. 1 illustrates the terms defined above. M is a mobile node. Node S is in communication with M, so S is a communication node. R2 is M's home agent. When M moves to the external network, R4 acts as an external agent. In this case R4
Is used as the care-of address of M. Mobile IP prepares a set of services that give nodes mobility. Here, each of these services will be described. Agent discovery: Home agents and foreign agents can advertise their availability on each link that they serve. In addition, the newly connected mobile node can send an explicit solicitation on the link to know if there is a possible agent. Foreign agents respond to solicitations by announcing their location. Mobile IP agent discovery is implemented as an extension to the ICMP (Internet Control Message Protocol) router discovery protocol. The agent discovery protocol extends the messages (router advertisement and router solicitation) used in the router discovery protocol. The messages used in agent discovery are therefore called agent advertisement and agent solicitation.

Registration: When a mobile node is away from home, it informs its home agent of its current location using a process called registration. Depending on how it belongs to the network, nodes register either directly with the home agent or through a foreign agent that forwards the registration to the home agent. Registration is valid for a fixed time or lifetime of the registration. When the mobile node is using the co-located care-of address, there is no need for a foreign agent, and the mobile node can register directly. When the mobile node returns to its home network, the mobile node "re-registers" with its home agent to stop forwarding packets.

Tunneling: The service provided by a home agent that forwards a packet to a mobile node is called "tunneling." When tunneling a packet, the home agent sends an original IP header by placing another IP header in front of the existing packet.
Encapsulate the packet. This "outside" IP header has a source address, which is the IP address of the host in the capsule, and a destination address, which is the care-of address of the mobile host. If the care-of address is a foreign agent, the foreign agent receives the packet, decapsulates it and sends it locally to the mobile node. If the co-located care-of address is used, the mobile node receives the packet and decapsulates the packet itself.

FIG. 2 illustrates the encapsulation process when a foreign agent is used. In operation, home agent R2 and foreign agent R4 announce their presence using an agent advertisement message. The mobile node M is originally connected to its home network, so it operates without mobility services at this point. The mobile node M moves to a foreign network. When the mobile node detects that it is on a foreign network (since it receives the foreign agent's advertisement), it gets a care-of address. The care-of address is obtained from the foreign agent advertisement message sent from R4. If a node such as R4 that provides foreign agent service is not available, and if the mobile node has that capability, the mobile node will obtain a co-located care-of address using a service such as DHCP. You can try.

Mobile mode M registers its new care-of address with home agent R2 through the exchange of a registration request and reply message. If the address of R4 is used as a care-of address, the registration request and reply are sent to foreign agent R4, which then forwards the packet appropriately. When co-located care-of addresses are used, no foreign agents are involved. When a communication node sends a packet to M, the packet is routed to M's home network. Home agent R2 intercepts these packets and tunnels them to M's care-of address. If the R4 addresses are care-of addresses, R4 decapsulates the packets and sends them locally to M. If a co-located address is used, the tunneled packet will be picked up by M itself and decapsulated. In the reverse direction, packets sent by M to S are sent to their destination, independent of M's location, using conventional IP routing mechanisms.

Mobile IP security is essential because it involves the ability to change the routing of packets destined for any host to be sent to anywhere else on the Internet. Attacks on registration requests and responses cause packets destined for the mobile node to be undeliverable or sent to the wrong destination. For example, another host attempts to pretend to be a mobile node and convinces the home agent to send a packet to it. Therefore, confirmation is performed by the mobile node and home agent for all registration requests and reply messages. The mobile node shares a security parameter index (SPI) and a secret key with its home agent to verify its home agent. One of several available algorithms can be used for confirmation, such as "Keyed Message Digest Version 5" (MD5) with a key size of 16 bytes. In order to prevent any registration messages from being played, time stamps and temporary marks are used to identify each of the registration requests and replies.

(Mobile IP with Route Optimization) Basic Mobile IP allows a mobile node to move away from its home network by preparing a home agent to intercept packets destined for the mobile node's home address. To In the general situation shown in FIG. 3, the mobile node M shown here is away from its home network and communicates with a communication node S located on a foreign network to which the mobile node is currently connected. ing. When mobile node M sends a packet to communication node S, the packet is routed directly to mobile node M using conventional IP routing. However, when the communication node S sends a packet to the mobile node M, the packet is first routed back to the mobile node M's home network. The home agent R2 of the mobile node M intercepts this packet and tunnels it to the mobile node's current foreign agent R1. When the foreign agent R1 receives the encapsulated packet, the capsule is decapsulated and then sent to the mobile node M.

Alternatively, as shown in FIG. 4, packets can be routed more optimally by sending them directly to each other and across the local network. Optimization of the route for Mobile IP optimizes the route that a packet travels from the communication node S to the mobile node M. Any type of packet routing optimization from the communication node S to the mobile node M requires that the communication node S maintain information about the current location of the mobile node M. Each communication node S that supports route optimization must maintain a repository of care-of addresses, called a binding repository. When a communication node S sends a packet, it checks its binding repository to look for a header corresponding to the destination address of the packet. If a matching heading is found, the communication node S itself encapsulates the packet with the care-of address specified in the binding repository heading, and instead of sending it to the mobile node M's home network, directly the care-of address. Tunnel to

If the binding repository header is not found, the packet is sent using conventional IP routing,
It sends the packet back to the mobile node M's home network as before. When home agent R2 intercepts the packet, it assumes that the source host does not have a binding repository heading for mobile node M. Home agent R2 replies by sending a confirmed binding update to communication node S to inform mobile node M of the current care-of address before communication node S tunnels the packet to the current location of mobile node M. Home agent R2 sets the lifetime of the binding update to the time remaining in registration for that particular mobile node M. When the original source receives and confirms the binding update, it adds the binding update to the binding repository for future use. The binding update expires after the time specified by home agent R2.

In order for communication node S to be able to use route optimization, software processing needs to be running to receive and process binding updates. If the host does not use route optimization software, the packet will be
Routed in the same way as Basic Mobile IP. Since some communication nodes S will not have this route optimization software, home agents R2 need to have an algorithm that limits the rate at which they send binding updates to each communication host S, and so on. Otherwise, home agent R2 floods the network with binding updates to communication node S, which will ignore them.

(Clever Switching System) As shown in FIG. 5, the network system of the present invention provides a location and one or more high-speed coverage areas, each of which covers a portion of the location. It incorporates a number of technologies that provide the highest quality from each of the networks, including wide area wireless networks that provide low speed coverage over local area wireless networks. As mobile nodes move through the network, they are continuously within the wide area network and move in and out of the local coverage area. The network technology to use in a particular situation is selected based on the requirements of each particular application. A single composite network made from sub-networks using different technologies thus provides an integrated solution. The flow of data in this network is
Take the most efficient route from the source to the destination, depending on the technical characteristics of the particular sub-network. For example, if a high-speed local area communication link is available between two nodes that want to communicate, the communication path can be used against a slower wide area link that is also available. If there is no other means of communication between the two nodes, the wide area network is used as the default means.

In a preferred embodiment, the mobile IP
Is used to switch between networks as described above. Mobile IP schemes have the advantage of not requiring router changes or mobile nodes in the network. However, the protocol does not specify when to change the subnetwork connection. The system prepares a basic Mobile IP protocol with instructions on which network connection to establish, requiring only minimal changes to the standard Mobile IP protocol. In this system, some mobile nodes cannot carry the operator, and even if they can,
No input from the operator is required, as attention must be focused on operating the device, rather than trying to determine if network delivery should occur. In addition, one of the inputs to the process that determines when to switch networks is the assessment of the quality of wireless communication signals from correspondents on the local area network. The signal strength and the current level of noise or interference can be used to predict future values or recorded for later use. In addition to being able to evaluate this signal quality level, thresholds are set for certain local area network technologies. This value is the minimum satisfaction signal quality value for the hardware, obtained either directly from the hardware or from the hardware specification. Another useful input to the decision process is knowledge of the mobile node's current location. This type of input is combined with knowledge of the location of the wireless local area network transmitter to evaluate signal quality values.

To prepare a realistic model of RF propagation,
The system includes a description of the actual terrain surrounding the mobile node. Using the RF propagation model, the switching system
Attempts to predict when delivery will be required to minimize the time the mobile node is disconnected from the network. The switching system predicts future values of signal quality for communication over the local area network connection. This signal quality value is then compared to a particular threshold. If the predicted value exceeds the threshold, the switching system instructs Mobile IP to try to communicate using its local area network interface; Instruct to communicate using a network connection.

(Switching System Structure) FIG. 6 shows components of a preferred embodiment of the present system. Model center 20
Would provide the core functionality of the switching system, for example,
It includes a set of components such as a model daemon 22, a location-based prediction mechanism 28, an environment / surface map 32, an RF propagation and communication model 34, a non-location-based prediction mechanism 38, and a movement model 56. Since the switching system has a standard dimensional design, it is possible to incorporate the underlying technology as it is improved. The model daemon 22 knows the current state of the mobile node and determines a switch based on this state and inputs from two other sources, a location-based prediction mechanism 28 and a non-position-based prediction mechanism. Is a state machine. The model daemon 22 also sends instructions to the mobile IP software 2
4 and the Mobile IP component allows the mobile nodes to inform their home agent R2 of their current location.

FIG. 7 shows the state machine used by the model daemon 22 to make its switching decisions. When the model daemon 22 starts execution, it starts from the WAN state (where "WAN" means the network interface that Mobile IP was commanded to use, in this case the wide area network interface). . The wide area network was chosen for the initial state of the system because it is assumed that it is always available. Many things can happen from this state.
First, if nothing else happens, model daemon 22 sends an "update" command to the Mobile IP software on this node. Update instructions are sent periodically to ensure that model daemon 22 and mobile node M are in sync.

If the model daemon 22 only leaves the WAN state, the model daemon 22 will determine if the signal strength empirically collected (ie, read directly from the local area network interface hardware). It is time to determine that a stable connection to a local area network (LAN) is indicated. In a preferred embodiment, this is the model daemon 22
Is above the signal strength or LAN signal strength threshold
Hardware signal quality input 26 from AN hardware
Occurs when reading several consecutive values of. Once the model daemon 22 enters the LAN state, it can only leave if one of the following prediction systems predicts a signal strength future value below the LAN threshold. If that happens, a command to switch to the WAN interface is sent to the Mobile IP software on this node, and the model daemon 22 re-enters the WAN state. While in the LAN state, the model daemon 22 sends an "update" command to ensure that the model daemon 22 and the mobile IP software are in sync.

The decision to switch from a LAN interface to a WAN interface is made based on predictive information, whereas the decision to switch from a WAN to a LAN is made based on empirical measurement data. This distinction is made to minimize the likelihood that the mobile node will be commanded to use the local area network interface when that network is not actually available.
As a result, the state change rule facilitates entering the WAN state, since the wide area network connection is always assumed to be available. Another important point is that the model daemon 22 has no concept of home or external. that is,
Know only about network interfaces. The decision whether the mobile node M should be home or foreign is left to the Mobile IP software or routing protocol 24 (FIG. 6) and is not affected by the presence of the model daemon 22.

Referring again to FIG. 6, the position-based prediction mechanism 2
8 accepts the current position of the mobile node from the position acquisition system 30 as input and uses this information as the environment / ground map 3
2 is moved to the coordinates above, and the movement of the mobile node M to a new point is predicted. The location-based prediction mechanism 28 also uses the equations for RF wave propagation and prepares the coordinates as input to an RF propagation and communication model 34 that calculates future signal strength at one or more locations at that location.
Hardware that reliably obtains location information, such as the Differential Global Positioning System (DGPS), is commercially available and readily available. The switching system of the present invention provides an environment / operating environment / operating even when location information is not available.
It has a default location prediction system, such as the ground update system 36. To this end, the system maintains a record of empirically collected signal strengths and interpolates a set of data points to produce future values, a non-position based prediction mechanism 38.
including.

The interpolation performed by the non-position based predictor 38 considers many past values or only a few values and combines them into a polynomial form, ie, fitting them into a curve, It can be as complex as you need. A simple example involves defining a straight line using the two most recently collected signal strengths. The third point is interpolated along this line to the expected signal strength. More useful features would then be more predictable than just the next point in time. In this sense, more complex models can be used that fit a curve through a series of points, taking into account the past behavior of the system.

A location-based prediction mechanism 28 is part of the model center 20 and provides an environment / ground map 32, a location acquisition system 30, RF propagation and It uses information from a number of sources, including the communication model 34, the environment / surface update system 36, and the mobility model 56. FIG. 8 shows a flowchart of a decision process for estimating the signal strength. When the location-based predictor 28 is invoked at block 40, it first attempts to gather input about the current state of the mobile node. The current strength of the local area network communication is obtained from the model daemon 22 that previously read data from the local area network hardware. The mobile node's current location is gathered from any available location system, as indicated by block 42. Once these inputs have been collected, the system checks to see if an environment / ground map 32 for the current location of the mobile node is available at block 44. If environment / surface map 32 is not available at this point, a return error will occur at block 4
6 and the position-based prediction mechanism 28 is disabled. The model daemon 22 will use the value from the prediction mechanism 38 that is not based on position as a default means.

When the environment / surface map 32 at this point is available, the switching system attempts to predict the future location of the mobile node at block 48. The future position of the mobile node is determined for a particular heading of the environment / surface map 32. The data stored at that location, especially the past signal strength and the time it was collected, are recovered. Once the past values have been collected, the system will use the environment / surface map 3 at the location specified by the current location.
2 stores the current signal strength together with the current acquisition time. The time elapsed since the collection time is calculated and compared in decision block 50 to an age threshold associated with the current surface map. If the elapsed time is less than the threshold, the past value is used as a predicted value in block 52. Otherwise, calculations need to be performed using the RF propagation and communication model 34 to predict future signal strength at block 54. The expected signal strength is then
As described above, it can be returned to the model daemon 22 to be used as an input to the threshold comparison. The model daemon 22 can use past signal strengths to learn about its environment from previously visited locations. When the mobile node is using its local area network connection, it can record the signal strength collection as a historical value in its environment / surface map 32. When the mobile node leaves the area to perform a task and later returns to approximately the same place where it was before, the mobile node can use the past signal strength as the expected signal strength, eliminating the need for RF propagation calculations.

Past values can become outdated in situations where the surface of the area in one area of the local area network coverage changes faster than another area. The model allows each area of the local area network coverage to have its own age threshold. By way of example only, the ground surface near a field work center is often fairly static because operation generally does not occur near the field work center. If this is the case, the age threshold for the field work center will be relatively long, for example, a week or so. The work area age threshold may only be valid for a relatively short period of time, as the surface changes faster. If the mobile node returns to its previous location within the time limit set by the age threshold, the model daemon 22 can use past values as predictions. Otherwise, the model daemon 22 needs to calculate a completely new value. More complex aging systems can be devised to age slowly past values over half-life, preferably combining those values with values predicted by the RF propagation and communication model 34 in a weight polynomial. .

In a preferred embodiment of the system,
The position acquisition system 30 is a Differential Global Positioning System (DGPS), but can be replaced with another technology. The target resolution of the environment / ground map 32 (the size in meters of each grid) is a parameter for the switching system of the present invention. One limitation on this resolution is that it cannot be refined beyond the accuracy of DGPS equipment. The resolution of the smaller grid is also
Requires greater storage capacity for the ground map 32 and computationally more sophisticated RF propagation model calculations.
A larger grid size allows for faster calculations and less storage capacity, but displays the earth's surface with less accuracy and generally results in less accurate RF propagation calculations. The resolution of the "grid" of the ground map should not exceed the resolution of the location information. The position information can be displayed in degrees of latitude and longitude or in Cartesian coordinates having a reference coordinate system fixed in space. It should further be noted that the model is not restricted to use on maps with a fixed grid. For example, a map with an irregular mesh display of the earth's surface is possible.

The environment / ground map 32 is a local area map.
The network / coverage can be thought of as a grid placed on the ground over the area where the network coverage exists, or where the wide area network coverage exists, or in general, the environment / surface map 32 is It can also be present for all areas regardless of range. Each square of the grid is a storage location and holds three values. The first value is an altitude value corresponding to an elevation above sea level (or some other reference point) on the ground surface at that point. The second value is the signal strength. As the mobile node traverses the actual surface, the model daemon 22 tracks its location across the environment / surface map 32 and records empirical acquisitions of signal strength in these storage locations. The third value stored is
The time at which the most recent signal strength was collected.

The initial terrain data file or movement model 56 (in FIG. 6) contains elevation information about the terrain of the local area network in question. The file also contains, as described above, the Cartesian coordinates of the center of the environment / ground map 32, where x and y are the horizontal and vertical distances expressed in preferred units of measure from the fixed reference position, range and resolution in meters. Specify the “size” and age threshold of the surface map represented by. FIG. 9 depicts some of these concepts. Position 58 is the origin of the Cartesian coordinate system. Overlying the contour 60 representing the range of the local area network is the ground map 3
2 is a virtual grid 62 representing the second grid. The center of the wireless local area network is the grid 6
Located at the center of the two, the grid extends beyond the edge of the coverage area of the wireless local area network represented by contour 60. The initial ground data file 56 including the altitude information of the local area network receivable range area specifies the position 58 or the center of the ground map 32 with respect to the fixed reference point 64. With knowledge of its current location relative to the fixed reference point 64, the mobile node can determine which of the available surface maps 32, if any, is appropriate for use at a particular location.

The environment / terrain update system 36 for calculating the future position of the mobile node a few seconds ahead warns the model daemon 22 to send a switch command before the network connection is completely lost. Prepare The system of the present invention uses the two most recently collected positions of the mobile node and projects a series of recently collected positions from the method of projecting the path of the mobile node along a straight line through these two points. A variety of position prediction methods can be used, ranging from more complex position prediction systems to fitting parameter curves such as Bezier curves such as More complex forecasting systems include knowledge of commonly followed paths (i.e., roads) through the surface and the dynamic properties of units,
Alternatively, the motion is intelligently predicted based on the surrounding ground surface.

In the current system, the RF propagation and communication model 34 uses the predicted location of the mobile node, the location of the transmitter (typically a local area network access point or base station), the surface between them, and the transmitting equipment. Based on the radio frequency provided, an estimate of the signal strength of the local area communication that the mobile node will receive will be created. The preferred embodiment of the RF propagation and communication model 34 models the effect of natural terrain on electromagnetic wave propagation in real time. This model utilizes a two-dimensional path loss model based on information stored in the environment / surface map 32. The two-dimensional model treats the earth's surface as if it were in a vertical plane between the RF transmitter and the receiver. RF transmissions can travel across or beneath the surface of the earth, but cannot leave the plane to travel around surface features. To build a two-dimensional model,
X of the transmit and receive antennas of the environment / surface map 32,
A vertical plane is intersected between the y and z coordinates. Next, two calculations are performed on this ground slice. First, a free space estimate of the propagation of RF waves from the transmitter to the receiver is calculated using the following equation: P _r = P _t G _t G _r λ ² / ((4λ) ² d ² L) where P _t = transmission power G _t = gain of transmission antenna G _r = gain of reception antenna λ = transmission wavelength d = antenna Distance between L = system loss factor.

This calculation estimates the received transmit power when the two antennas are assumed to be in free space without any kind of interference. Next, plane ground calculation is performed. In the planar ground estimation of RF propagation, another path from the transmitter to the receiver is used, the reflection path from the transmitter to the ground and the ground to the receiver, using the following equation: P _r = P _t G _t G _r h _t ² h _r ² / d ⁴ where P _t = transmission power G _t = gain of the transmission antenna G _r = gain of the reception antenna h _t = transmitter height h _r = Receiver height d = distance between antennas.

Once both calculations have been performed, the lesser of them (representing the "worst case" received power) is used as the basis for the next stage of the model calculation. Some of the RF wave power is carried by secondary waves that do not propagate on the direct path from the transmitter to the receiver. These secondary waves arrive at the receiver after diffracting at a point source located between the transmitter and the receiver, and carry a significant component of the total transmit power. Even if there is a direct line of sight between the transmitter and the receiver, these secondary waves are blocked, reducing the total received power. Fresnel zone refers to the type of these secondary waves based on the path that the waves propagate. Proper Fresnel band gap means that there is no significant power loss because a sufficient amount of these secondary waves can reach the receiver. The gap in the Fresnel zone is calculated according to the prior art depending on which of the following conditions is met: 1. A line of sight exists between the transmitter and the receiver and there is a suitable Fresnel band gap. In this case, the previously calculated base value is used as the received power. 2. A line of sight exists between the transmitter and the receiver, but there is no suitable Fresnel band gap. The received power further decreases from the basic power due to the loss of the secondary wave. 3. There is no line of sight between the transmitter and the receiver. In this case, only a part of the secondary wave can reach the receiver. The results of these calculations are then transferred back to the location-based prediction mechanism 28. A method for calculating a three-dimensional RF propagation model is as follows:
Can be used as a substitute for a two-dimensional model. Three-dimensional models will generally require larger data processing equipment. Those skilled in the art will recognize that any other RF propagation model can be used as well as the above model.

(Quality of Service Characteristics) The network of the present invention generally employs a "throughput", which is the average amount of data sent per unit time measured in bits per second or packets per second, and the rate at which packets travel from a source to a destination. It is mainly concerned with two key quality of service (QOS) parameters, the "time delay", which is the average time it takes to travel. The network utilizes the highest frequency band path from the source to the destination using a path optimization and smart switching system. High-speed wireless local area network
When a link is available, it will generally be used instead of a wide area link.

FIG. 10 shows a state diagram 68 of the present switching system, where a mobile node can only belong to its home network when using its local area network interface. The system begins with a connection loss condition that erases some internal variables, disables the local area network interface, and enables the wide area network interface. Control then transitions to a delete route state that deletes the routing information stored by the mobile node. In the acquisition state, the mobile node attempts to register with its home agent by sending a registration request for all available network interfaces. Control is then automatically transferred to a care-of-wait state in which the mobile node waits for a reply from its registration request. If the registration attempt fails,
The mobile node sends the registration request again and remains in the care-of-waiting state. If retransmission is not allowed, the mobile node returns to the acquisition state and generates a new registration request. If the registration request is successful, the mobile node enters a care-of-registration state corresponding to the mobile IP concept of belonging to a foreign network. The mobile node can remain in this state indefinitely during a successful attempt to reregister the same interface previously used. Registration attempts can only be made using the enabled interface, and the mobile node is then instructed to communicate with the particular interface. If these registration attempts fail, the mobile node returns to the lost connection state and the process starts over.

In addition to the failed registration attempt, the mobile node may issue a switch command to the model daemon 22 to instruct the mobile node to switch from its local area network (LAN) interface to its wide area network (WAN) interface. If you receive from
You can leave the care-of registration state. In this case, the mobile node enters a lost connection state. If the switch command switches from a wide area network interface to a local area network interface,
The system must first enable the local area network interface and disable the wide area network interface. At this point, the system cannot enter the lost connection state because it changes the enabled / disabled state of the network interface again. Instead, the lost connection state is skipped, and the lost path state is entered directly. next,
Once in the acquisition state using the local area network interface, the system may be in a home state (if the mobile node belongs to the home network) or finally a care-of-registration state (if the mobile node belongs to a foreign network). ).

In many different places in the state diagram 68,
The mobile node attempts to detect if its home agent is on a directly connected subnetwork. If a home agent is detected (because the mobile node receives the home agent's advertisement message), the mobile node immediately enters the home state. Once at home, the mobile node will stay there until it receives a command to switch to the wide area network interface, at which point it will enter a loss of connection state.

As shown in FIG. 11, a graphic user interface (GUI) for monitoring the status of the mobile node is provided with the present system. The switching system GUI consists of the depiction of the ground map 32 and the display of status information. The terrain map 32 is displayed in a grid having the required dimensions, with the local area network transmitter defining the center of the local area network relative to the terrestrial map and being marked in black at the grid center. The height of the ground surface can be indicated by color on the map or by other means such as terrain elevation lines. For example, the ground map depicted in FIG. 11 is shown using an altitude code, which code is specified, for example, in meters. It is recognized and anticipated that any coding system and altitude measurement unit can be used to display the surface map. The current coordinates of the mobile node relative to the fixed reference, in this case a maintenance track, are displayed on the right side of the map, and the location of the mobile node is indicated by a hatched square on the map.
The GUI also displays information about which interface the mobile node is currently using (LAN or WAN interface) and the quality of the DGPS information (on or off). Further information on the GUI indicates that the mobile node (i.e.
(48, 0). Further, the mobile node is using its LAN interface and its DGPS equipment is functioning properly.

(Wireless Local Area Network) The present system provides a mobile node with a local area network to provide the ability to communicate at high speed to nearby fixed computers or other nearby mobile nodes. I need. One such local area network is Wave LAN, a product developed by Lucent Technologies. However, the standard dimensional design structure of the system can accommodate any preferred local area network technology. Local area network frequency bands used with the present invention include communications such as isochronous voice data, bursts,
And it must be high enough to support large-capacity communications such as file transfers and image data.
Local area networks must also provide access to signal strength measurements for use in switching systems. This signal strength data is a measure of the received power of a packet originating from another wireless host. Local area networks also need to enable peer communication.

Wireless Wide Area Network Another important aspect of the network architecture of the present invention is the wireless wide area network technology, which provides coverage of communications through global operation and provides predefined communications for different components of the system. Consists of pathways. Any wide area network technology used with the present network structure must provide certain capabilities in order to effectively support the communication characteristics of the present network structure. One ability is
The wireless wide area network needs to be selected to provide coverage throughout the work site.
This coverage should preferably not limit the network to the gaze arrangement of the transmitter. The network must also provide for multipoint capability, broadcast capability, from a single point. In addition, support for packetized data
Required to carry the Internet Protocol communications of the network. In addition, ensuring wide coverage is often at the expense of the ability to provide high frequency bands, but since this property greatly affects overall system performance, fair trade conditions should be considered. . One example of a suitable wide area network is Pacific
An RFM96 radio modem manufactured by Crest. The Pacific Crest products are configured to transmit at 2 watts of power, giving them sufficient coverage to completely cover a large area without the need to place the antenna in line of sight. Another alternative to wide area networks is the use of low earth orbit satellites currently under development.

Use with Temporary Networks In addition to the use of prediction and RF propagation models with Mobile IP, the present invention can also be used in temporary networks. A temporary network is a collection of wireless mobile hosts that form a temporary network without the help of any existing infrastructure or centralized administration. In such an environment, due to the limited range of each mobile host's radio transmission, one mobile post needs to get the help of the other host to have the packet forwarded to its destination It is.

(Industrial Applicability) The present invention requires that some components and operators, such as autonomous or semi-autonomous machines, coordinate their actions in order to accomplish their tasks as efficiently as possible. Applicable in certain situations.
For example, one on-site work center may direct machine effort across the site to gather information about the status of the machine, the status of the changed terrain brought to the site, and the status of the work to be accomplished. In addition, there is a need for communication between the machine and the operator, which allows close cooperation between them and governs the various operations performed on site. The information is also communicated to repair and maintenance personnel, who need to alert them of problems that may slow down or stop the operation of the machine. The present invention provides a warning message, a network management message enabling communication between nodes,
Detailed information about the terrain at the work site, the location of all machines and the current status of one or more jobs currently being performed, audio transmissions, diagnostic and maintenance information, and the fact that the machines cooperate with each other Enables and accommodates a wide range of different types of messages, including image data, to help the control point (operator) make a diagnosis in the event of a work interruption. The present invention provides the ability for machines to move between different wireless network technologies using mobile IP protocols with route optimization, peer-to-peer communication, and smart switching systems.

FIG. 12 shows a land improvement machine such as a front shovel 80 shown in position at a work site 70.
The front shovel 80 is a caterpillar-type machine that performs various civil works at the work site 70. However,
It will be apparent that the principles and applications of the present invention will be useful for virtually any moving tool or machine capable of moving on or underground at a work site and changing the terrain of the work site in some manner. There will be. Front shovel 80
Is equipped with available hydraulic or electro-hydraulic tool controls used to control its operation.

The front shovel 80 is equipped with a position finding system (not shown) that can determine the position with high accuracy. In particular, the front shovel 80 can be equipped with a DGPS receiver (not shown) located on the front shovel 80. Other location systems such as GPS / laser combinations or radar may also be used. The position coordinates of the front shovel 80 in the work site 70 are obtained when the front shovel 80 moves on the work site 70. These coordinates can be calculated in real time to determine the position and path of the front shovel 80 or can be provided as a series of discrete points so that the ground map 32 of the work site 70 can be dynamically updated. . Further, the front shovel 80 also includes a local digital computer (also shown) having a display (not shown) for storing the digitized model of the work site 70 before the change and the target terrain of the work site 70 after the change is completed. (Not shown). The digitized model is also a representation of an environmental map of the ground map 32 or corresponding to the entire area of the work site to be changed. For example, the environmental map includes the structure of the area. The dynamic update information or the ground map 32 can be displayed in real time and can be used by the operator of the front shovel 80 on the display. Using information from the display, the operator can efficiently monitor and command manual control and operation of the front shovel 80. A location system and / or a local digital computer is an example of a means for dynamically updating a ground map as the ground is being modified by a front shovel 80 or other mobile terrain modification machine.

Additionally or alternatively, the dynamic update information may be provided to an electrohydraulic control system having various pumps, valves, hydraulic cylinders, motor / steering mechanisms, and other controls associated with the land improvement machine. Ready for such automatic machine control systems. Electro-hydraulic control minimizes mechanical work, maximizes performance, and provides operator assistance to limit manual control in the event that operator action overloads the machine, for example. Alternatively, site update information can be used to prepare fully integrated automatic machine / tool control.

Some other components of the present invention included in the work site 70 are a maintenance truck 72 and a field office 74 that perform machine maintenance at the work site 70. In this embodiment, the service technician has the ability to take the service laptop 76 from the network at the field office 74 and attach it to the network of service trucks 72, where the laptop is located.
Register to 8. When a mobile node, such as a front shovel 80, needs maintenance, it sends a packet containing a status message to the field office 74. The packets originate from the front shovel 80 and pass through the wireless local area network 82 to the router 84 at the work site 70. The router 84 has data input / output capabilities and runs on a computer system that executes software, which handles IP data packets, determines destination addresses, and transmits the packets over a wireless wide area network 86. Router 88 which is the default home agent of the front shovel 80
Transfer to Router 88 at field office 74 receives the packet, determines its destination address, and forwards the packet to local area network (LAN) 90. Before the packet is sent out to the LAN 90, the router 88 encapsulates the packet as a destination address by the care-of address router 78 of the maintenance laptop 76 and forwards the packet to the local area network 90.

The home agent router 88 determines the source of the original packet (front shovel 80), sends a binding update to the front shovel 80, and sends it to the front shovel 80, where the maintenance and inspection laptop 76 is the mobile router 78 address. The current care-of address. Before the encapsulated packet is sent through the local area network 90 to the foreign agent 78 of the maintenance laptop 76, the home agent router 88 intercepts the packet again. The home agent then encapsulates the packet with the care-of address of the mobile router 78 as the destination address and forwards the packet to the wide area network 86. The home agent again asks the front shovel 80 to be the first source of packets, sends a binding update to the front shovel, and also tells the mobile router 78 the current care-of address. Router 84 at work site 70 receives the packet from wide area network 86 and forwards the packet to wireless local area network 82. Mobile router 7
8 transmits the packet to the wireless local area network 8
2 and remove the first capsule. The mobile router 78 attempts to forward this internal packet to the correct location. The destination address of this internal packet is the address of the mobile router 78 itself, and
Instead, it processes the internal packet itself by removing the internal capsule and forwards the packet to the maintenance laptop 76. The maintenance laptop 76 receives the packet and replies to the front shovel 80. The packet is first sent to the mobile router 78, which is the default router for the maintenance laptop 76. Using the communication capabilities of the peers of the wireless local area network 82, the mobile router 78 forwards the packet directly to the front shovel 80 using the wireless local area network 82.

Front shovel 80 receives the packet and receives two binding updates from home agent 88. Front shovel 80 uses binding updates to add headings to its binding repository. Once the front shovel 80 has a combined repository headline for the service laptop 76 and the mobile router 78, the front shovel can send packets using route optimization until the combined repository headline expires.
The front shovel 80 first looks up its binding repository, then the packet is encapsulated by using the care-of address of the maintenance laptop 76, which is the address of the mobile router 78, as the destination address.
Front shovel 80 again finds its heading for mobile router 78 in its binding repository. The packet is encapsulated a second time using the care-of address of the mobile router 78 as the destination address. The packet is then sent to wireless local area network 82. Using the peer-to-peer capabilities of the local area network 82, the packet is sent directly to the mobile router 78. The mobile router 78 receives the packet using the wireless local area network 82 and removes the first capsule. The mobile router 78 attempts to forward this internal packet to the correct location. The destination address of this internal packet is the address of the mobile router 78 itself, so the router 78 instead processes the internal packet itself by removing the internal capsule and forwards the packet to the maintenance laptop 76. I do.
The maintenance laptop 76 receives the packet and replies to the front shovel 80. The packet is first sent to the mobile router 78, which is the default router for the maintenance laptop. Using the peer-to-peer capabilities of the local area network 82, the mobile router 78 forwards the packet directly to the front shovel 80 using the wireless local area network 82. Front shovel 80
Receives the packet.

Because the front shovel 80 has a binding update to the maintenance laptop 76 and the mobile router 78, the packets are no longer in the wide area network 86.
Not routed to This makes efficient use of the network's facility equipment and minimizes the use of low speed wide area networks. In the above embodiment, the front shovel 8
It should be noted that the zero route optimization software needs to perform two encapsulations to send the packet directly to the maintenance laptop 76.

Although the embodiment described above included only one work site 70, the invention is implemented to cover multiple work sites and multiple machines at each work site. It is possible. Further, when multiple machines are used, it is possible to display the updated information on individual indicators associated with each machine. The display is
Ground map 3 as seen from either or both machines
2 has the ability to update dynamically. In addition, when multiple machines are used, it is further possible to dynamically update the communication signal propagation model in response to updating the ground map 32. Other aspects, objects, and advantages of the invention are described in the drawings,
It can be obtained by reference to the disclosure and the appended claims.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a basic configuration of a mobile IP.

FIG. 2 is a functional block diagram showing a basic configuration of Mobile IP having packet tunneling.

FIG. 3 is a functional block diagram illustrating packet routing without route optimization.

FIG. 4 is a functional block diagram illustrating packet routing for route optimization.

FIG. 5 is an overview diagram showing an example of a coverage area of a local and wide area wireless network.

FIG. 6 is a functional block diagram of the switching system structure of the present invention.

FIG. 7 is a diagram of a state machine used by a model daemon to make a switching decision.

FIG. 8 is a flowchart illustrating an example of prediction based on a position.

FIG. 9 is a schematic view of a ground surface map.

FIG. 10 is a diagram of a state machine for the switching system of the present invention.

FIG. 11 is a diagram of a graphic user interface for the switching system of the present invention.

FIG. 12 is a diagram of a work site where the present invention can be used.

[Explanation of symbols]

 R1 Foreign agent R2 M's home agent S Communication node M Mobile node

Continued on the front page (72) Inventor Bernard Jay Bennington United States of America Pennsylvania 15217 Pittsburgh Beachwood Boulevard 2044 (72) Inventor Daniel dee Stansill United States of America Pennsylvania 16046 Mars Westminster de Live 125 (72) Inventor David Bee Johnson United States of America Pennsylvania State 15217 Pittsburgh Bell Rock Street 1220

Claims (13)

[Claims] 1. A method for dynamically updating a communication signal propagation model in an area that is undergoing civil engineering work that changes the terrain on the ground, comprising: moving a ground map of the area as a function of the civil engineering work. Updating the propagation model dynamically in response to updating the ground map. 2. The method of claim 1, further comprising dynamically updating an environmental map of the area, including a structure of the area. 3. The method of claim 2, wherein the structure is a stationary structure. 4. The method according to claim 2, wherein the structure is a moving structure. 5. The method of claim 1, further comprising predicting communication quality at a future point in time based on the propagation model. 6. The method of claim 1, further comprising the step of providing an operator display of the surface map. 7. An apparatus for dynamically updating a communication signal propagation model in an area exposed to a mobile terrain changing machine capable of changing the terrain on the surface, wherein the communication signal propagation model receives a change by the mobile terrain changing machine. Means for storing a surface map representing a previous surface of said surface, said means for dynamically updating said surface map when said surface is being modified by said mobile land improvement machine, Means for dynamically updating said propagation model in response to an update. 8. The system further comprising: a second mobile terrain changing machine; and means for dynamically updating the ground map when the ground is being changed by the second mobile terrain changing machine. The device according to claim 7, characterized in that: 9. The system further comprising: means for dynamically updating the propagation model in response to updating the surface map when the surface map is being modified by the second mobile terrain modifying machine. The device according to claim 8, characterized in that: 10. The mobile terrain modifying machine further includes means for predicting the quality of the communication signal at a future point in time based on the predicted location of the mobile terrain modifying machine as a function of speed and direction of travel. The apparatus according to claim 7, characterized in that: 11. The apparatus of claim 11, further comprising means for predicting the quality of the communication signal at a future point in time based on a previous quality of the communication signal at the predicted location of the mobile terrain changing machine. An apparatus according to claim 7. 12. A method for dynamically updating a communication signal propagation model in an area exposed to first and second civil engineering machines that alter the terrain on the surface, the method comprising: Dynamically updating as a function of the first and second civil engineering machines; and dynamically updating the propagation model in response to updating the surface map. . 13. An apparatus for dynamically updating a communication signal propagation model in an area exposed to first and second civil engineering machines that alters the terrain on the surface, the apparatus comprising: a ground map of the area. Dynamically updating as a function of the first and second civil engineering machines; and a means for dynamically updating the propagation model in response to updating the surface map. .