sharing context- aware road and safety information

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T e l e m a T i c s a n d V e h i c u l a r c o m m u n i c a T i o n s

P

roviding traffic information remains an important challenge on roads throughout the world. The Radio Data System (RDS) in Europe and South America and the lesser-known Radio Broadcast Data System (RBDS) in North America are initial steps to provide drivers with context-aware information. The Traffic Mes- sage Channel (TMC) uses RDS to deliver travel information to users. Both the research community and public administrations are interested in understanding affect how onboard information systems affect user safety.

The communication channel and information source are both important issues in such information provision systems. However, apart from the over-studied centralized systems, which simply collect traffic notifications at a central station, the research community is now focusing on propagating local events to surrounding vehicles. Vehicular ad hoc networks (VANETs) are examples of such networks. VANETs facilitate harnessing a decentralized, spontaneous network to route messages among vehicles.

In addition to providing information to the driver and using a suitable communication channel, a third element is crucial in the design of a complete vehicular information system:

the infrastructure edge. An effective human or automatic monitoring strategy is necessary to

ensure correct road network operation. A centralized system is also necessary in applications that require processing critical events to obtain global knowledge about the road network and thus improve driving safety and efficiency.

We present an integrated vehicular system for the collection, management, and provision of context-aware information on traffic and driver location. This system uses an integrated vehicle- to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication paradigm enriched with an information management system. The infrastructure manages vehicle-detected safety hazards and other relevant information, adapting them to the vehicle’s context and driver’s preferences. This vehicular integrated system resem- bles the concept of a smart road.¹

Toward unified V2V and V2i communications

The necessity of a communication channel to integrate the vehicle in the traffic environment has led intelligent transportation system (ITS) researchers to investigate vehicular networks.

Initial approximations to this problem include monitoring systems for company fleets, in which research is now very specialized.² Cellular networks (CNs) are usually considered a V2I communication channel, in which a centralized system tracks vehicles. Researchers soon realized the importance of autonomous cooperation among vehicles. Using a V2V communication pattern, a vehicle could notify surrounding vehicles of traffic events of interest.³ For several This integrated vehicular system represents a complete ITS solution for

the collection, management, and provision of context-aware information on traffic and current location for the road environment.

José Santa

and Antonio F. Gómez-Skarmeta University of Murcia,

Espinardo Campus

sharing context-

aware road and

safety information

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years, this has been the main research line in vehicular communications, mainly through VANET solutions.⁴

Today, new interests are arising in the V2I communication field, but they currently focus on vehicle integration with roadside equipment.¹ (V2I usually refers to dataflow in both directions: vehicle to infrastructure, and infrastructure to vehicle.) For example, researchers are considering deploying radio frequency identification (RFID) technologies for goods tracking and traffic sign recognition. Electronic fee collection systems use dedicated short-range communications (DSRC) to communicate with onboard terminals, and other proposals use this technology to provide Internet connectivity to vehicles.⁵ CNs have also undergone relevant improvements, offering good Internet connectivity in mobile environments but also support-

ing common monitoring solutions. CNs are now a mature technology, and some of their features make them more ap- propriate than VANETs for vehicular communications in certain scenarios.⁶

Both VANETs and CNs have good characteristics for vehicular communications. VANET solutions offer high performance connectivity among nearby vehicles because their decentralized architecture uses vehicles to create a scalable, cooperative mesh in which every vehicle acts as a router. CNs offer long-range communications via direct connectivity to the Internet through the operator’s network. This communication paradigm has two additional advantages: assurance of connectivity even without a high ratio of equipped vehicles, and the use of a proven deployed technology.

Our approach combines the advan-

tages of both VANETs and CNs to es- tablish a starting point to embrace all of their services. Figure 1 illustrates our idea of merging the main advantages of a decentralized solution with CN technology. Using a peer-to-peer (P2P) paradigm over the CN, our architecture harnesses the benefits of both approaches. P2P networks create a virtual decentralized architecture in which individual nodes can communicate without physical details about the underlying network. The architecture initially inherits latency limitations for close V2V communications from the CN. Currently, a CN connection can- not match the latency times of VANET systems between nearby vehicles.

However, new improvements point to CN technology as a valid carrier of vehicular transmissions for increasingly more services, making it a suitable

Decentralized Scalable

V2V communication (VANET)

Good local connectivity

Cooperative approach

V2I communication (CN)

Penetration rate not required

Direct Internet connection Good

far

connectivity Deployed

technology

CN and P2P communication model for V2V and V2I

Scalable Good local

connectivity Decentralized

Deployed technology

Direct Internet connection Good

far connectivity

Information system for context-aware information provision and monitoring

Scalable Good

local

connectivity Decentralized

Deployed technology

Direct Internet connection

Information inference

Road state management

Road events

dissemination Driver preferences Good

far connectivity

Advantages of both paradigms

using P2P

Using infrastructure

storage and intelligence

Figure 1. Advantages of a cellular network (CN) and peer-to-peer (P2P) communication system with infrastructure capabilities.

Our architecture takes advantage of the synergy of these technologies to reach an integral intelligent transportation system (ITS) platform for supporting context-aware information provision services.

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TelemaTics and Vehicular communicaTions

complement to VANET approaches.⁷ The cost of the communication channel is also an important issue in CNs.

Due to special agreements between operators and service providers, the cost of CN data connections is gradually decreasing.

Our earlier work described our first steps in the design of such a communication architecture and our initial performance evaluations.⁸ We have extended this system with functional capabilities at the edge of the vehicle and enriched it by integrating it into an en- tire vehicular information system.

importance of infrastructure in context-aware

information management A V2V network lets vehicles communicate and propagate information over a limited area. Such a strategy is useful for notifying nearby vehicles about traffic hazards, road conditions, traffic jams, and other local events. However, a V2I link offers extra benefits. Our work goes a step further, using an infrastructure system to provide context- aware information to drivers, depend- ing on their preferences, and generally taking advantage of a global system ca- pable of processing roadside events.

Figure 1 shows the new capabilities of our network model after we added infrastructure communication. The core system can give a global vision of the road network state, processing information from vehicles and roadside hardware, and performing monitoring tasks. In this way, a system following this scheme could

notify vehicles about traffic problems

•

affecting a long highway;

send a warning message of conges-

•

tion forecasts, on the basis of traffic jam messages received from vehicles or information feedback from roadside loop detectors; or

report pollution problems in a given

• area.

These are only some of the possi-

bilities such a system offers via traffic data analysis and the combination of V2V and V2I communications to overcome the limitations of current traffic information systems such as the TMC. In our design, a local entity responsible for a particular traffic area collects information by receiving local events from vehicles and roadside hardware.

The communication architecture in- tegrates an inference technique, which adapts information provided to vehicles according to user preferences. Earlier work describes our initial develop- ment of this idea.⁹ Here, we integrate the management of user profiles in an information provision system. Users and road operators can modify system behavior, and the vehicle can receive relevant points of interest (POIs) according to custom inference rules. This service exemplifies the potential of infrastructure-based services and the usefulness of the infrastructure-to- vehicle (I2V) communication link as a complement to V2V.

communication

architecture and information- Processing system

Our main goal is to develop a platform that provides ubiquitous services to vehicles,¹⁰ enabling a suitable networking platform for implementing services that span V2V and V2I communications. Figure 2 shows the over- all architecture. In our earlier work,⁸ we explained the vehicular network, which involves entities located at the roadside (gray zone) and a global entity called the group server (GS). Each vehicle drives along roads with service provision capabilities, and every coverage area and its associated services are registered in the GS. The system services have an informative nature and exploit V2V and V2I capabilities.

Hence, they include safety services such as breakdown or repair-notification services, as well as tourism and travel information. The methodology follows a publish-subscribe scheme

in which vehicles subscribe to some services and receive asynchronous notifications.¹¹

Using a P2P network with JXTA technology, vehicles communicate with one another and with the infrastructure. The GS stores geometrical information about every coverage area and its P2P communication groups.

Thus, all available services use a P2P group, which generally changes when the vehicle enters a new area, limiting the propagation of messages only in an area of interest. Vehicles pass from one coverage area to another through a hand-off process aided by a global navigation satellite system (GNSS)—in this case, a GPS one. The vehicle uses a TCP/IP-based protocol to send a hand- off request to the GS, which replies with the P2P connection details and the new area’s geometry.

Messages transmitted over the JXTA overlay network are routed through logical pipes, and contain information about the message source, the event type, and the event payload. When a vehicle subscribed to a service sends a message, all vehicles in the area that are also subscribed receive that message. This mechanism offers a V2V communication paradigm. However, an infrastructure entity called an environment server (ES) is placed in every coverage area (see Figure 2). The ES monitors all event messages sent among vehicles in its area and pro- cesses them according to its content. It also plays a forwarding role between vehicles and the infrastructure in a V2I communication scheme. Because the ES is connected to the rest of the roadside hardware, it can send certain notifications to vehicles, such as “your speed is over the limit,” using a unicast mechanism. Environment servers are logical entities and, therefore, can be installed in roadside computers or ex- ecuted over a server located at the core infrastructure. The latter offers more flexibility, avoiding scalability and maintenance drawbacks. The connection between the roadside hardware

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and the ES can be physical or remote;

our RFID prototype is connected to a remote ES, for instance.

We’ve also developed a complete information system for the infrastructure side. The distributed-core storage manager system, represented by a dashed line in Figure 2, is implemented via remote objects, which the rest of the infrastructure entities use through remote method invocation (RMI).

Each ES forwards new events from vehicles and road hardware to the core storage manager. The Internet traffic operation server (ITOS) provides Web access with a complete view of road events by analyzing the roadside information accessible via the core storage manager. This Web application offers

differentiated access to users and operators. Operators, unlike system cli- ents, have an administration account with management capabilities. Users of the Web front end can check road conditions from home or even using their vehicle’s onboard computer, via an Internet connection.

So that certain services can offer context-aware information in the local traffic area, the system includes a model of the environment through ontologies, whose instances represent relevant locations in the coverage areas. This information is distributed to each ES in charge of maintaining a local database. The system models user preferences as profile ontologies located in the core storage man-

ager. Users can modify their profile through the Web application located at the ITOS.

The information provision technique integrated in the platform works as follows. Vehicle presence is detected during a hand-off via the management link maintained with the GS, or by a specialized device (such as the RFID reader used in our prototype). When the vehicle is detected, the ES requests the user’s profile from the core storage manager (see Figure 2). Using this profile and the available contextual database, the ES performs an inference process and notifies the driver of the adapted information, following an I2V communication pattern. Road operators can manage the contextual Global navigation

satellite system (GNSS) Users

Profiles

Environment server_n

Local-event notification Areas

services

Internet traffic operation system (ITOS) User profile

information

configurationArea

Storage access

On-road hardware

Events for new Area Local event notification

Web access to global road state and account

settings

Web-based management

Local event notification Area_n

TCP/IP HTTP

Remote method invocation JXTA

Figure 2. Complete communication and infrastructure architecture. Vehicles communicate with one another and with the infrastructure using an overlay network. The infrastructure provides extended capabilities in the management of roadside information and the provision of context-aware notifications.

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database through the Web application at the ITOS. A previous work details the ontological models used in the system.⁹

Information from subscribed services is thus sent or received via events. Such events come directly from other vehicles or from the infrastructure via ES entities. Events from the roadside initially have local importance because they represent context-aware information exchanged in a V2V pattern, but they’re also useful for creating a global view of the road network at the ITOS edge.

Because V2V events sent in an area can be active for a long time, vehicles entering the area might not be aware of an important incident. This is why the

ITOS supports the GS in the hand-off process and sends previous events col- lected in the area to entering vehicles, as Figure 2 shows.

system operation from the Vehicle’s Viewpoint

Figure 3 illustrates the five most typical scenarios. In the first one, drivers subscribe to the services in which they’re interested. The onboard software sends a subscription to the GS to receive or send notifications from or to the network. Once the vehicle connects to the system or enters a new coverage area, a hand-off occurs (second scenario).

Because vehicles receive the geometry of the service areas from the GS, the

onboard unit (OBU) detects the necessity of performing a hand-off by means of its navigation subsystem. In this process, the GS sends to the vehicle the P2P connection parameters and the new area’s geometry. The onboard software also asks about traffic incidents in the new zone to update its local navigation information.

The third scenario in Figure 3 exemplifies the connection that an ES can maintain with the roadside hardware.

We’ve implemented a prototype in which an RFID system detects a vehicle and the ES provides the driver contextual information. In addition to this I2V message passing, the fourth scenario in Figure 3 illustrates V2V Group server

Global navigation satellite system, satellite-based augmentation system Subscription (Serv1, ...)

Group server

ES_n

Internet traffic operation server 1 Area

update

2 Area info

3 Events query

4 Events response

(b)

ES_n 2 Presence

notification

1 Detection

(c)

(a)

RFID reader

1 Event 4 Event 1 Event

2 Neighbor query

2 Event notification

(d)

ES_n

3 Neighbor response

(e)

ES_{n + 1} Group server

3 Event

1 Event 1 Event

ES_n ES_{n + 1}

Distributed-core storage manager

4 Event

Figure 3. Operation scenarios and interaction with the system: (a) subscription to services, (b) hand-off process, (c) reception of events from the roadside, (d) emission of events and message forwarding to the core infrastructure, and (e) forwarding of critical events to adjacent service areas. Vehicles exchange information events via the overlay network, and environment servers interconnect road and infrastructure segments.

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communication. Here, the yellow vehicle notifies other vehicles in the area of a road maintenance event. The ES also receives this event and forwards the message to the core storage platform, following a V2I paradigm. Fi- nally, the last scenario illustrates the forwarding mechanism that an ES executes when a critical event is received from the roadside (a vehicle or other roadside hardware). When the ES receives a notification such as

“Collision” from a critical service, the ES asks for the same service’s P2P parameters in adjacent areas and forwards the message to these environment servers. The vehicle that initially generated the event sends the message to all vehicles in the current area, but the forwarding strategy ensures that vehicles in adjacent areas receive the information as well.

Prototype details

To create a complete prototype of the system, we have set up a real vehicle and real hardware for the infrastructure, while also implementing all the necessary software. The University of Murcia has employed the vehicle for testing and adapted it in a widely sen- sored vehicle in several research proj- ects.¹² A single-board computer (SBC) and the rest of the sensors installed in the vehicle (GPS, odometer, gyro, and so on) comprise the OBU. We’ve also used another vehicle equipped with GPS and a common laptop in our V2V and hand-off tests.⁸ We implemented the ES approach and ran several instances over common Linux-based PCs. To test the connection between an ES and the rest of the road hardware, we set up an RFID reader, which detects a vehicle presence through a tag

affixed to the windshield. The photo- graphs in Figure 4b show this setup.

We installed the RFID reader at the test location using an ad hoc gantry.

We connected a laptop via a serial port to the reader, to send presence notifications to the corresponding ES. We developed the GS and ITOS and installed them over a high-performance server, to cover high rates of queries.

The OBU contains a software platform for developing and deploying services using the Open Service Gateway initiative (OSGi), which implements applications as modules.¹³ One of these applications is Message Console, which appears in Figure 4a. This application can use the information services offered by our system. Using the buttons on the right side of the window, users can connect to the services they’re interested in.

When the activated services appear in the user connect with the platform and receive context-aware notifications mapped on a navigation system. The radio frequency identification (RFID) prototype deals with the logic to detect vehicles at certain points of the road network, to provide relevant information about the surroundings.

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the current coverage zone, their corresponding images appear below, and users can receive and send events by clicking on them.

The central part of the window shows messages about active services (road incidents, weather, tourist information, and so on). In this example, the vehicle has received information about hotels and cinemas. The service that provides such information is called on-road in- formation, and uses the RFID system to detect the vehicle at certain places.

When an ES receives the presence notification, it asks the core infrastructure for the user profile and then infers relevant information for the driver via its local environmental database. Finally, the ES sends this information to the vehicle, including the matching rate for each point of interest. In the example, the hotels that best suit the user’s preferences are AC Elche, NH Amistad, and NH Rincón de Pepe, with a matching rate of 43 percent. The interring subsystem calculates this suitability rate,

considering the number of features that match the user’s profile and the POI element.

Figure 4 also shows the onboard software’s navigation capabilities. This feature currently supports both Google Maps and geographic information systems (GIS) data. The software draws both previous road problems received during the hand-off and new ones via icons over the road. The light red line in Figure 4 depicts the polygon cover- ing the current coverage area. When the vehicle is close to a road event (initially sent by a vehicle or roadside sen- sor or manually fixed by an operator), the application graphically displays a warning, along with the remaining distance to the incident, and commu- nicates further details through a spoken alert. The example in the figure involves a warning about the proximity of a breakdown on the road. A yellow mark on the map represents this event.

As this example illustrates, a warning icon, a spoken alert, and the navigation

map always inform the user of a road incident. The central text panel also notifies the user.

The distributed-core storage manager consists of a set of RMI entities (profile manager, user manager, and road- event manager) performing information management tasks, and a remote MySQL database to physically store all data. The RMI entities work as inde- pendent applications, each publishing a remote object used by the ITOS and environment servers. In our prototype, the RMI applications and the MySQL server run on the high-end computer mentioned earlier, but they can be installed in different hosts.

Figure 5 shows two screenshots of the Web application located at the ITOS, implemented using JSP (Java Server Pages). The application depicts road incidents over map images created from GIS data, but also supports Google Maps. In the map view provided in Figure 5a, a road operator is reading information about a traffic jam event a vehicle has reported near Murcia. Road event types appear on the left side of the window. For every incident, a colored mark over the map identifies the event type, and users can access its associated information by clicking on the icon. A typical user can only see road network information, but the operator can also insert, de- lete, or modify events and manage the registered users. Each user can, nev- ertheless, change his or her own profile, as shown in Figure 5b, to vary the information received from the infrastructure. The user can select several features about several kinds of POI—

(b) (a)

Figure 5. Monitoring and user

management application: (a) map view and (b) edit profile view. Using the Web application hosted by the ITOS, users and operators can monitor and manage road network incidents and modify the platform’s behavior when they receive context-aware information.

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O

ur system comprises a complete context-aware information provision system for the road environment, and we’re currently working on a multitude of interesting areas in this general system. We’re especially interested in the roadside hardware. Vehicle identification is just one capability of RFID in vehicular environments. Traf- fic sign recognition and the labeling and tracking of goods are some features we’d like to include in our system using RFID. We’re also performing more field tests with our integrated V2V-V2I and CN-based communication platform to prove that our solution is a feasible alternative to VANET approaches for most applications. The infrastructure capabilities in terms of information provision and traffic monitoring are continually growing as well, with new functionalities oriented toward both the operator and the user. We’re also evaluating new capabilities to include at the infrastructure edge via a GIS, which will make it possible to analyze data from the roadside according to the road network features. Our ultimate goal is to create a novel, versatile, and useful information system for the vehicular environment.

ACkNOWleDgMeNTS

We thank the Spanish ministry of Science and Education for sponsoring this work under grants Fpu-Ap2005-1437 and tIN2008-06441-C02-02, and the Spanish program to Aid Groups of Ex- cellence of the Séneca Foundation under grant 04552/GErm/06.

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interests include vehicle communications, context awareness, location-based services, positioning systems, electronic vehicle identification, and intelligent transportation systems. He has a phD in computer science from the university of murcia, Espinardo Campus. Contact him at [email protected].

Antonio F. Gómez-Skarmeta is a professor in the Department of Information and Communications Engineering at the university of murcia, Espinardo Cam- pus. His research interests include mobile communications, pervasive systems, network security, and intelligent transportation systems. He has a phD in computer science from the university of murcia, Espinardo Campus. Contact him at [email protected].