Patent Grant
9524642
A vehicular ad hoc network (VANET) is a mobile network that uses moving vehicles as nodes in the mobile network. For example, a VANET turns participating vehicles into a wireless router or node, allowing vehicles within approximately 100 to 300 meters of each other to connect and to create a network with a wide range. As vehicles fall out of signal range and drop out of the network, other vehicles can join in, connecting vehicles to one another so that a mobile Internet is created.
There are various types of VANETs, including, e.g., vehicle-to-infrastructure (V2I) networks, vehicle-to-vehicle (V2V) networks, and so forth. Generally, a V2I network includes a network of vehicles and roadside infrastructure for promoting communication among the vehicles and the roadside infrastructure. There are various type of roadside infrastructure, including, e.g., roadside units (RSUs). Generally, a RSU includes a device for providing vehicles with information, e.g., safety warnings and traffic information. Generally, a V2V network includes a network of vehicles for promoting communication among the vehicles.
In one aspect of the present disclosure, a method performed by one or more processors includes receiving a notification message indicative of an occurrence of an event; determining that a position of a vehicular device that is associated with the one or more processors is located on a boundary of a reachability area surrounding a source of the event; determining that a direction of movement of the vehicular device is towards the source; responsive to determining that the position is on the boundary of the reachability area and that the direction of movement of the vehicular device is towards the source, entering a roadside unit state in which the vehicular device acts a roadside unit for a pre-defined period of time; detecting one or more vehicular devices that are uninformed of the occurrence of the event and that are located outside of the reachability area; and broadcasting the notification message to the one or more uninformed vehicular devices.
Implementations of the disclosure can include one or more of the following features. In some implementations, the method also includes receiving, from at least one of the one or more uninformed vehicular devices, information indicating receipt of the broadcast notification message. In other implementations, the method includes detecting an absence of receipt of information indicating that at least one of the one or more uninformed vehicular devices received the broadcast notification message.
In still other implementation, entering the roadside unit state comprises causing movement of the vehicular device that is associated with the one or more processors to temporarily cease for re-broadcasting of the notification message. In some implementations, the method includes determining that the pre-defined period of time has elapsed; responsive to determining that the pre-defined period of time has elapsed: enabling movement of the vehicular device that is associated with the one or more processors; and transitioning from the roadside unit state to another state for performing one or more of storing the notification message, carrying the notification message, and forwarding the notification message.
In some implementations, the vehicular device that is associated with the one or more processors comprises the one or more processors. In other implementations, the notification message comprises one or more of traffic information, road information and safety information; wherein the event comprises one or more of traffic related conditions, an accident, and road related conditions; and wherein the source comprises one or more of a location of the traffic related conditions, a location of the accident, a vehicular device that caused the accident, and a location of the road related conditions.
In still other implementations, determining that the position of the vehicular device that is associated with the one or more processors is located on the boundary of the reachability area surrounding the source of the event comprises: determining, based on execution of a series of instructions, that the position of the vehicular device that is associated with the one or more processors is located on the boundary of the reachability area surrounding the source of the event; wherein the series of instructions comprise:
angle between a vector (from Vehicle A to Vehicle S) and another vector (from
set of all neighboring vehicles of Vehicle A.
moving direction of Vehicle A with respect to a line connecting from Vehicle A to
∠(A, S, i)
min (mini(θi), 0)
(max (maxi(θi), 0)
temporary RSUs
wherein vehicle A comprises the vehicular device that is associated with the one or more processors; wherein vehicle S comprises one or more of the source and one of the one or more informed vehicles; and wherein vehicle i comprises a neighbor of vehicle A.
In some implementations, the method includes detecting a density of vehicular devices in proximity to the vehicular device associated with the one or more processors;
determining a size of the region of interest; and determining the pre-defined period of time based on the size of the region of interest and based on the density of vehicular devices in proximity to the vehicular device associated with the one or more processors. In still other implementations, the method includes indirectly detecting a rebroadcast of the notification message by at least one of the one or more uninformed vehicular devices to which the one or more processors originally broadcast the notification message, with indirect detection based on one or more of beacon messages and overhearing the notification message being broadcast by the at least one of the one or more uninformed vehicular devices; and in response to detecting, transitioning from the roadside unit state to another state for performing one or more of storing the notification message, carrying the notification message, and forwarding the notification message.
In still another aspect of the disclosure, one or more machine-readable media are configured to store instructions that are executable by one or more processors to perform operations including receiving a notification message indicative of an occurrence of an event; determining that a position of a vehicular device that is associated with the one or more processors is located on a boundary of a reachability area surrounding a source of the event; determining that a direction of movement of the vehicular device is towards the source; responsive to determining that the position is on the boundary of the reachability area and that the direction of movement of the vehicular device is towards the source, entering a roadside unit state in which the vehicular device acts a roadside unit for a pre-defined period of time; detecting one or more vehicular devices that are uninformed of the occurrence of the event and that are located outside of the reachability area; and broadcasting the notification message to the one or more uninformed vehicular devices.
Implementations of this aspect of the present disclosure can include one or more of the foregoing features.
In still another aspect of the disclosure, an electronic system includes one or more processors; and one or more machine-readable media configured to store instructions that are executable by the one or more processors to perform operations including: receiving a notification message indicative of an occurrence of an event; determining that a position of a vehicular device that is associated with the one or more processors is located on a boundary of a reachability area surrounding a source of the event; determining that a direction of movement of the vehicular device is towards the source; responsive to determining that the position is on the boundary of the reachability area and that the direction of movement of the vehicular device is towards the source, entering a roadside unit state in which the vehicular device acts a roadside unit for a pre-defined period of time; detecting one or more vehicular devices that are uninformed of the occurrence of the event and that are located outside of the reachability area; and broadcasting the notification message to the one or more uninformed vehicular devices. Implementations of this aspect of the present disclosure can include one or more of the foregoing features.
All or part of the foregoing can be implemented as a computer program product including instructions that are stored on one or more non-transitory machine-readable storage media, and that are executable on one or more processors. All or part of the foregoing can be implemented as an apparatus, method, or electronic system that can include one or more processors and memory to store executable instructions to implement the stated operations.
The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.
A system consistent with this disclosure expands a communication range of a VANET by causing vehicular devices in the VANET to act as fixed-point communication nodes, e.g., for a pre-defined and temporary period of time. There are various types of fixed-point communication nodes, including, e.g., RSUs. By causing vehicular devices to act as fixed-point communication nodes, the system enables a V2V network to act as a V2I network, e.g., without the expense of the infrastructure associated with a V2I network. As a temporary RSU, a vehicular device can make a brief stop and take on or assume tasks of a conventional RSU—relaying messages to nearby vehicles and acting as a communication bridge for other vehicles in the network.
Referring to
In the PCN environment, safety messages are disseminated to vehicles within region of interest 150, which is an area surrounding a source of an event. In this example, region of interest 150 includes reachability area 138.
Generally, a reachability area includes an area surrounding a source of an event that is within a communication range of the source (and/or within a communication range of a vehicle at the source). In this example, the event may be a traffic-related event—an accident, and a road related event, and so forth. In this example, the source may be one or more of a location of the traffic related event, a location of the accident, a vehicular device that caused the accident, a location of the road related event, and so forth. Generally, a safety message includes information about an event. In an example, the event is an accident. In this example, the safety message includes information indicative of a time of the accident, a location of the accident, and so forth. Generally, a safety message may be issued by a vehicle involved in the accident, an emergency services vehicle (e.g., a police car), a bystander, a bystander vehicle, and so forth.
In the example of
In the example of
In this example, reachability area 138 (e.g., the gray-shaded region) surrounds vehicle 122. In this example, other vehicles included in reachability area 138 are in a communication range of vehicle 122. After the broadcast from vehicle 122, vehicles 112, 114, 116, 118, 120, 124, 130 in reachability area 138 receive the message and are informed about the accident. In this example, vehicles 112, 114, 116, 118, 120, 124, 130 are informed of the accident via spatial relays from vehicle 122 or other informed vehicles, e.g., vehicles that are informed of the message and/or vehicles that are informed of the event (e.g., the accident). In an example, informed vehicles are informed of the event via the broadcast of the safety message from vehicle 122. In another example, informed vehicles are informed of the event based on proximity of the informed vehicle to a source of the event. For example, a police car that is in vicinity of a source of an event is an informed vehicle, e.g., because a police officer who is using the police car may use the police car to transmit safety messages to other vehicles that are in proximity to the police car. In this example, reachability area 138 includes vehicles that can receive messages from vehicle 122 via direct transmission or via multi-hop forwarding.
In an example, vehicles 102, 104, 106, 108, 110, 126, 128, 132, 134, 136 are located outside of reachability area 138, are outside of a communication range of vehicle 122, and are inside of region of interest 150. In this example, vehicles 102, 104, 106, 108, 110, 126, 128, 132, 134, 136 do not receive the safety message from vehicle 122. In this example, one or more of vehicles 112, 114, 116, 118, 120, 124, 130 include a RSU determination module (not shown) to identify when a vehicle should act as a RSU, e.g., to promote dissemination of the safety message to uninformed vehicles that are outside of reachability area 138. Generally, an uninformed vehicle includes a vehicle that has not received the message originally broadcast from the source, e.g., from vehicle 122. Generally, a RSU dissemination module includes a series of instructions that are executable by a processor (e.g., a processor included in a vehicle) to determine if the vehicle should act as a temporary RSU. In an example, the processor may be associated with the vehicle, e.g., by being configured from communication with the vehicle and/or with one or more components of the vehicle.
In an example, the RSU determination module selects vehicles to act as temporary RSUs based on various criteria. One of these criteria is that the vehicle is positioned on a boundary of reachability area 138. Vehicles that are on the boundary (boundary vehicles) of reachability area 138 are in proximity to both informed vehicles and uninformed vehicles. Boundary vehicles have an increased probability of encountering uninformed vehicles, e.g., relative to a probability of non-boundary vehicles and informed vehicles meeting uninformed vehicles. In this example, because the non-boundary vehicles and the informed vehicles are mostly surrounded by informed vehicles, selection of the non-boundary vehicles and the informed vehicles as temporary RSUs does not significantly increase the dissemination of the safety messages, e.g., relative to dissemination of the safety message when the non-boundary vehicles and the informed vehicles do not act as RSUs.
Another criteria for a RSU determination module to select a vehicle to act as a temporary RSU is that the vehicle is moving in a direction towards a source (e.g., a source of the accident). That is, in addition to using the position of vehicles in determining whether a vehicle acts a temporary RSU, the RSU determination module also uses a movement direction of the vehicle in determining whether the vehicle acts a temporary RSU. In this example, the RSU determination module is configured to select boundary vehicles that travel toward the accident as temporary RSUs. By having these boundary vehicles act as RSUs and stop at current locations for a brief period of time (and not continue to travel toward the accident scene), the subsequent rebroadcasts from these boundary vehicles may reach uninformed vehicles, when these uninformed vehicle arrive into the RSUs' neighborhoods (e.g., areas surrounding the RSUs). In this example, the RSU determination module is configured to not select as temporary RSUs those boundary vehicles that travel in the outward direction from the scene of accident. For example, in
For example, the RSU determination module may determine that vehicles that are close to a source (e.g., within predefined distance of the source and/or on a boundary of a reachability area for the source) and moving towards the source should act as temporary RSUs. The RSU determination module may also determine that stationary vehicles that are close to the source should not act as temporary RSUs, e.g., as these vehicles are not moving towards the source. The RSU determination module may also determine that vehicles that are not close to the source (e.g., not within the reachability area for the source), but are moving towards the source, should also not act as temporary RSU. The RSU determination module may also determine that vehicles that are close to the source (e.g., within the reachability area for the source and/or on a boundary of the reachability area for the source), but are moving away from the source, should not act as a temporary RSU. The RSU determination module may also determine that vehicles that are not close to the source (e.g., not within the reachability area for the source) and are moving away from the source should not act as a temporary RSU.
In the example of
As previously described, there are various ways in which a vehicle acting as a RSU may be configured to disseminate notification messages. In one example of a pre-emptive scheme, vehicle 116 that is acting as a RSU temporarily stops to rebroadcast the notification message. If vehicle 116 hears any of the vehicles rebroadcasting the notification message, then vehicle 116 will consider this as an implicit acknowledgement of receipt of the notification message and change its state from the RSU state to the SCF state and resume its trip.
There are various other techniques a vehicle acting as a RSU may implement to disseminate notification messages. In another example of a timer-based approach, vehicle 116 implements a timer based approach in which vehicle 116 stops for a pre-defined period of time (e.g., thirty seconds) to transmit the notification message and then resumes its trip. In this example, vehicle 116 acting as a RSU promotes network connectivity for the pre-defined period of time. If vehicle 116 cannot relay the notification message to another vehicle, vehicle 116 resumes its trip.
In an example, a vehicle acts as a RSU for forty-five seconds. In this example, the RSU fails to detect beacon messages (which implicitly indicate acknowledgement of the safety message) or to overhear the same safety message being broadcast by some of the uninformed vehicles, e.g., within the forty-five seconds that it is waiting. However, other vehicles may be moving towards the source of the event. These other vehicles may be selected as the RSU, e.g., when these other vehicles come within the transmission range of the source. When these other vehicles are selected to act as RSUs, these other vehicles wait for forty-five seconds in search of the next RSU.
In still another example, a vehicle acting as a RSU may temporarily stop for a minimum amount of time, e.g., min (t′, t_max), where min (x,y) is a function that returns the smaller of x and y in the argument. In this example, t′ is the time needed to establish a new RSU with the preemptive scheme and t_max is the fixed maximum time used in the timer based approach.
In the example of
In the example of
The RSU determination module combines additional rules that consider directions of vehicles with a distributed gift-wrapping algorithm to generate an RSU determination algorithm, as shown in the below Table 1. Generally, a RSU determination algorithm includes a series of executable instructions to identify when a vehicle should transition to a RSU state.
angle between a vector (from Vehicle A to Vehicle S) and another vector (from
set of all neighboring vehicles of Vehicle A.
moving direction of Vehicle A with respect to a line connecting from Vehicle A to
∠(A, S, i)
min (mini(θi), 0)
(max (maxi(θi), 0)
temporary RSUs
In the above Table 1, vehicle A is a vehicle in a reachability area for a source of an accident and it receives the safety message from vehicle S which could be a vehicle at the source and/or one of the one or more informed vehicles. Vehicle i is a vehicle that neighbors vehicle A, e.g., by being within a pre-defined distance of vehicle A.
Upon receiving the message from Vehicle S, Vehicle A computes an angle θi for its neighbors. In the example of
Referring to
Referring back to
In some embodiments, the RSU determination module determines that vehicle 120 is included in reachability area 138, e.g., rather than being on the boundary of reachability area 138, based on a value of |θ+|+|θ_| for vehicle 120 being greater than π. In this example, the RSU determination module identifies that vehicle 120 should remain in its current state, e.g., rather than transitioning to a SCF state or to a RSU state. In this example, the RSU determination module determines that vehicle 120 should remain in its current state, e.g., independent of the direction in which vehicle 120 is moving relative to vehicle 122.
In the example of
In an example, the RSU determination module is configured to determine an amount of time in which a vehicle remains in a RSU state. In an example, if a vehicle in a RSU state does not stop long enough to encounter uninformed vehicles, then message reachability does not increase. Generally, message reachability includes a fraction of vehicles in a network that receive a message. In another example, if a vehicle in a RSU state stops for too long, the travel delays of the vehicles that act as temporary RSUs are increased and message reachability also decreases. In an example, message reachability decreases when as the amount of time a vehicle acts as a RSU increases, for at least the following reasons. Uninformed vehicles that are outside a reachability area can be informed by receiving RSU rebroadcasts or SCF rebroadcasts. In an example, a network has a 20% DSRC penetration rate. In this example, when a temporary RSU's stop time increases from 10 seconds to 30 seconds, more uninformed vehicles benefit from the temporary RSU rebroadcasts. As the stop time of the temporary RSU exceeds 30 seconds, message reachability degrades due to two reasons: i) there are very few rebroadcasts made by a vehicle remaining in a RSU state during the excess time since vehicles that come into contact with the RSU during this time period are already informed via SCF rebroadcasts; and ii) a vehicle remaining in a RSU state for an extended period of time decreases the chance for the vehicle to do SCF rebroadcasts. That is, once the vehicle completes its RSU task of performing RSU rebroadcast, the vehicle could do additional SCF rebroadcasts and further improve the message reachability.
In this example, the RSU determination module is configured to calculate an amount of time in which a vehicle remains in a RSU state, with the calculation based on vehicle density of a region of interest, a size of the region of interest, and topology of the network surrounding the vehicle. In an example, when a vehicle acts as a RSU for a defined period of time, message reachability in a VANET increases, e.g., relative to message reachability independent of vehicles acting as RSUs (e.g., without vehicles acting as RSUs). In an example, a control system (not shown) may be configured to generate various metrics indicative of an effectiveness of causing a vehicle to act as a RSU. One of these vehicles may include a metric indicative of message reachability. The metric indicative of message reachability may be based on transitive connectivity and reachability among vehicles. In an example, a vehicle that is designated as vehicle j is transitively reachable from another vehicle (e.g., vehicle i) at time t if and only if the two following conditions are met: (i) vehicle i is connected with vehicle j at a point in time before t; i.e., ∃t′<t, A(i, j, t)=1, or (ii) there exists a relay vehicle, vehicle k, such that ∃t′, t″, where t′≦t″≦t, A(i, k, t′)=1 and A(k, j, t″)=1. In this example, A(i, j, t) is a connectivity indicator which takes on the value of 1 if there is a path available between vehicles i and j at time t, and 0 otherwise. The second condition implies that vehicle k receives a message from vehicle i at time t′ and vehicle k then stores, carries and forwards this message to vehicle j at time t″. Thus, vehicle j is transitively reachable from vehicle i (i.e., vehicle j receives a message from vehicle i).
In this example, the controller system determines that message reachability improves, e.g., when vehicles temporarily act as RSUs. Such an improvement is mainly due to the fact that vehicles that serve as RSUs stay in a network for a longer period of time, e.g., relative to a period of time in which these vehicles would otherwise stay in the network. In this example, a ratio of informed vehicles increases, e.g., relative to the ratio of informed vehicles independent of vehicles acting as RSU. This increase in the amount of informed vehicles (i.e., vehicles that have received the message) causes an increase in an amount of message rebroadcasts which reach the uninformed vehicles, e.g., relative to an amount of message rebroadcasts which reach the uninformed vehicles independent of vehicles acting as RSUs.
In an example, the control system may determine that message reachability varies with DSRC penetration rate. For example, the control system determines an increase in message reachability when RSU-vehicles are implemented in a network with sparse and moderately-dense DSRC-equipped vehicles (i.e., 10%-40% penetration rate), e.g., relative to message reachability in a network with highly-dense DSRC-equipped vehicles.
In the example of
As previously described, a RSU is one type of fixed-point communication node. In this example, the RSU state is a type of fixed-point communication node state, in which a vehicle acts as a fixed-point communication node. Using the techniques described herein, a vehicle may include a module for causing the vehicle to enter a fixed-point communication node state.
In a variation of
Referring to
In the example of
In still another example, the RSU determination module determines that a vehicle is included in a reachability area for a source of an event. In this example, the RSU determination module also determines (306) if the vehicle is on the boundary of the reachability area and is moving in a direction towards the source of the event. In an example, the RSU determination module determines that the vehicle is either not on the boundary of the reachability area and/or is not moving in a direction towards the source of the event. In this example, the RSU determination module causes (308) the vehicle to remain in a current state.
In some embodiments, the RSU determination module determines that the vehicle is on the boundary of the reachability area and is moving in a direction towards the source of the event. For example, referring back to
Referring back to
In the example of
Referring to
If the RSU determination module determines that vehicle 116 is not in a region of interest, then the RSU determination module completes its process and does not execute further instructions. If the RSU determination module determines that vehicle 116 is in a region of interest, then the RSU determines module determines (356) if vehicle 116 is on a boundary of the reachability area (also referred to herein as reachability region) for the source (e.g., an accident scene) and is moving toward the accident scene.
If the RSU determination module determines that vehicle 116 is either not on a boundary of the reachability area or is not moving toward the accident, the RSU determination module enters (364) a SCF state. Actions performed in the SCF state are described in further detail below. In this example, the RSU determination module also detects when vehicles 116 leaves (365) the region of interest. If the RSU determination module determines that vehicle 116 has left the region of interest, then the RSU determination module completes its process and does not execute further instructions.
If the RSU determination module determines that vehicle 116 is both on a boundary of the reachability area and is moving toward the accident, the RSU determination module enters (358) a RSU state. In the RSU state, vehicle 116 makes (360) a brief stop. During the brief stop, vehicle 116 receives (366) hello messages from uninformed vehicles. Generally, a hello message includes information announcing a presence of a vehicle. Responsive to the hello messages, the RSU determines module rebroadcasts (362) the safety message.
In the example of
Processing device 402 can include one or more microprocessors. Generally, processing device 402 can include an appropriate processor and/or logic that is capable of receiving and storing data, and of communicating over network 412. Examples of network 412 include a local area network (“LAN”), a wide area network (“WAN”), e.g., the Internet. Memory 404 can include a hard drive and a random access memory storage device, including, e.g., a dynamic random access memory, or other types of non-transitory machine-readable storage devices. As shown in
Embodiments can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations thereof. Apparatus of the invention can be implemented in a computer program product tangibly embodied or stored in a machine-readable storage device and/or machine readable media for execution by a programmable processor; and method actions can be performed by a programmable processor executing a program of instructions to perform functions and operations of the invention by operating on input data and generating output.
The techniques described herein can be implemented advantageously in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. Each computer program can be implemented in a high-level procedural or object oriented programming language, or in assembly or machine language if desired; and in any case, the language can be a compiled or interpreted language.
Suitable processors include, by way of example, both general and special purpose microprocessors. Generally, a processor will receive instructions and data from a read-only memory and/or a random access memory. Generally, a computer will include one or more mass storage devices for storing data files; such devices include magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and optical disks. Computer readable storage media are storage devices suitable for tangibly embodying computer program instructions and data include all forms of volatile memory such as RAM and non-volatile memory, including by way of example semiconductor memory devices, such as Erasable Programmable Read Only Memory (EPROM), Electrically Erasable Programmable Read Only Memory (EEPROM), and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM disks. Any of the foregoing can be supplemented by, or incorporated in, ASICs (application-specific integrated circuits).
In another example, due to the nature of software, functions described above can be implemented using software, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations.
A number of embodiments have been described. Nevertheless, it will be understood that various modifications can be made without departing from the spirit and scope of the processes and techniques described herein. In addition, the logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. In addition, other steps can be provided, or steps can be eliminated, from the described flows, and other components can be added to, or removed from, the described systems. Accordingly, other embodiments are within the scope of the following claims.
This application claims the benefit of priority under 35 U.S.C. §119(e) to provisional U.S. Patent Application No. 61/632,116, filed on Jan. 18, 2012, the entire contents of which are hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2013/022251 | 1/18/2013 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2013/109960 | 7/25/2013 | WO | A |
| Number | Name | Date | Kind |
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| 20040128062 | Ogino | Jul 2004 | A1 |
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| Number | Date | Country |
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| 2431761 | May 2007 | GB |
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| Number | Date | Country | |
|---|---|---|---|
| 20140354451 A1 | Dec 2014 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61632116 | Jan 2012 | US |
