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A New Taxi Ride Service for the ForthcomingGeneration of Intelligent Transportation Systems

Simone Frattasi1, Hanane Fathi1, Antje Gimmler 2, Frank Fitzek1, Ramjee Prasad11Center for TeleInFrastruktur (CTIF), Aalborg University, Aalborg, Denmark

{sf |hf |ff |prasad}@kom.aau.dk2Institute for Social Science and Organisation, Aalborg University, Aalborg, Denmark

gimmler@socsci.aau.dk

Abstract— This paper proposes a newIntelligent TransportationSystems(ITS) service, which solves a daily problem encounteredby most people living in a metropolis: how to catch a taxi in themost time efficiently manner. The architecture that supports thisnew Personalized Public Transit(PPT) service takes advantage ofthe heterogeneity of the network environment and utilizes cellularand short-range communications in order to solve the problemlocally and generate value for the user, the service provider andthe taxi driver. Besides the definition of the service itself, thispaper also gives an insight on its social robustness.

Index Terms— 4G, Cellular network, Convergence, Cooper-ation, Heterogeneity, Intelligent Transportation System(ITS),Multi-hop, Services, Short-range communication, Social Impact,User-centricity, Wireless communication, WLAN, WPAN.

I. I NTRODUCTION

Intelligent Transportation Systems(ITS) is a global phe-nomenon, attracting worldwide interest from transportationprofessionals, automotive industry and political decision mak-ers. It encompasses a broad range of wireless and wire linecommunications-based information and electronics technolo-gies that, when integrated into the transportation system’sinfrastructure and in vehicles themselves, help to monitor andmanage traffic flow, reduce congestion, provide alternate routesto travellers, enhance productivity, save lives, time and money,and deliver multimedia contents for drivers and passengers.Evolutions and revolutions of these technologies are hence ofdirect impact on the design of ITS systems. This paper focusesespecially on the potential advantages that may be introducedby communication technologies.

Currently, the design of theFourth Generation of WirelessMobile Communication Systems(4G) is under definition. In[1], in order to avoid prophetic visions, which usually arebound to end up in big ’flops’, 4G is approached by meanof a pragmatic methodology. The latter, showing that thecreation of innovative user-friendly and personalized services,which answer the daily needs of the users, are the firststep to be undertaken, ends up in an attempt of definition[2]: ”4G will be a convergence platform that will provideclear advantages in terms of bandwidth, coverage, powerconsumption and spectrum usage, thus also offering a varietyof new heterogeneous services (from pop-up advertisementsto location-based and interactive or on-demand ones – socalled IP datacasting). Though the core is still cellular, its

network architecture will be predominantly extended to short-range communication systems, where the users may alsocooperate in a completely distributed orcellular-controlledfashion [3]. All these characteristics will be supported bymulti-mode/reconfigurable devices and the implementation ofinterworking ones.”

This paper proposes a new ITS service, which solves a dailyproblem encountered by most people living in a metropolis:how to catch a taxi in the most time efficiently manner.The architecture that supports this newPersonalized PublicTransit (PPT) service takes advantage of the heterogeneity ofthe network environment and utilizes cellular and short-rangecommunications in order to solve the problem locally andgenerate value for the user, the service provider and the taxidriver. As a result, the synergy with the forthcoming generationof communication technologies is shown to efficiently supportITS systems, addressing problems related to transportation.

The rest of the paper is structured as follows: SectionII briefly introduces PPT services and technologies; SectionIII defines the new ITS service and architecture; Section IVdiscusses its social robustness. Finally, the concluding remarksare given in Section V.

II. PPT SERVICES AND TECHNOLOGIES

PPT or demand responsive transit serves pick-up passen-gers on a demand or as-needed basis. Personalized publictransportation uses all kinds of transit and paratransit vehicles:buses, taxis, shared-ride vans, etc. Vehicles are dispatched ondemand, and they typically provide door-to-door service, or atleast a short deviation from a fixed-route.

In recent years PPT has been greatly enhanced by theimplementation of advanced technologies for the dispatchingand routing of vehicles. Typically PPT involves the applicationof two technologies:

• Computer-Aided Dispatch Systems(CAD). Also knownas dynamic scheduling systems, this software automatesthe process of assigning ride requests to vehicles. De-pending on the operation, the objective may be to mini-mize passengers’ wait time, subject to a minimum vehicleload, or, conversely, to maximize the vehicle load subjectto a maximum wait time. The CAD system tracks all riderequests (origin, destination, time of pick up, number ofpassengers), assigns riders to the available vehicles while

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Fig. 1. Unshared taxi ride scenario. Fig. 2. Shared taxi ride scenario.

simultaneously planning vehicles’ routes and dispatchesthem.

• Advanced Vehicle Location(AVL). It lets dispatchersknow where en-route vehicles are located, so that theycan pick up passengers whose ride requests were receivedafter the vehicle left the base. This is likely to reducewaiting times and increase the number of passengersserved per vehicle-mile, but it could also increase the ridetime for those passengers already in the vehicle. Whenvehicles are equipped with AVL, the CAD system wouldhave to be able to evaluate whether it is advantageousto assign the new ride request to a vehicle enroute or toan undispatched vehicle. The dominant AVL technologydeployed today is theGlobal Positioning System(GPS),representing close to 75% of all systems deployed. How-ever, it is well known that GPS receivers are unreliable orunusable in difficult environments such as indoor, underdense foliage and in urban canyons. That is why GPScannot be used stand-alone for ITS applications. Usually,it is integrated with other systems to ensure the integrityand accuracy of positioning.

CAD and AVL have the potential to increase the efficiencyof paratransit services and offer advantages to both operatorsand users. Operators may consolidate existing demand in fewervehicles, serve a larger market and reduce labor costs. Userscould enjoy reduced advanced reservation times, reduced wait-ing times and faster travel times.

III. A N EW TAXI RIDE SERVICE

A. Dedicated Ride

In a metropolitan city like Paris, New York, or Rome, peoplewant to get on a taxi as fast as possible. Unfortunately, oftenthere are many taxis available but not visible in their vicinity(around 100 m of range). In case, instead, that each taxi isequipped with anAccess Point(AP), the user terminal canbroadcast a taxi ride request (red dashed lines in Figure 1),which is forwarded to theBase Station(BS) by the APs ofthe available taxis in the user’s range (black dashed lines inFigure 1) to avoid concurrency. The CAD system will thenchoose the appropriate taxi based on its proximity with the

user1 and return to the selected taxi the location of the userand to the user the taxi’s arrival time (green dashed lines inFigure 1).

The benefit for the customers is mostly the time-efficiency,as the proposed service does not require them to reach athird party (i.e., the dispatch center) in order to search fora taxi nearby. For the taxi drivers, instead, the advantage isthat the signalling information received from the user andexchanged with the BS is not displayed, so that they do notget disturbed unnecessarily. Only the closest available taxi ismade aware of its course: it receives a message notifying thata customer is waiting at the given location (e.g., one streetaway). The whole situation is solved locally via the cellularnetwork, which works as a controller avoiding the conflictingsituation where more than one taxi is warned to pick up thesame customer or a taxi gets more than one customer goingto different destinations. As a consequence, the reward for thenetwork provider is to charge for the provision of the newservice.

B. Shared Ride

Short-range communications also allow multi-hop ad-hocconnections to be established, thus permitting users out ofthe taxis’ coverage to exploit the service just by using theother people’s terminals as relays and creating a group ofcustomers that may share all or part of their trip (see Figure2). A cooperative action may hence advantage multiple usersgoing to the same direction, since they can minimize the costof their course. Furthermore, such an infrastructure can also beused to improve the accuracy of the users’ location estimation,as shown in [4].

Once in the taxi, the customer/s can have access to theInternet and, thus also to multimedia contents, via the AP.The latter may either be connected via the cellular networkor through a multi-hop link set up by the surrounding taxisto a fixed AP (see Figure 3). Thereby, even terminals that arenot featured with a cellular technology can be connected via a

1For a more accurate localization respect to the actual cellular-basedtechniques, if the user terminal is equipped with the GPS, the request containsalso the estimated position of the user.

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Fig. 3. Multimedia content delivery.

Fig. 4. Service network architecture.

Wireless Personal Area Network(WPAN) or aWireless LocalArea Network(WLAN) technology in such environment.

The network architecture that supports the proposed serviceis depicted in Figure 4.

IV. SOCIAL IMPACT OF THEPROPOSEDITS SERVICE

The scenario sounds rather brilliant: to be in New YorkAND to be able to catch a taxi in an ordinary workingday. This is possible with the proposed ITS service, wherethe coordination of the taxis and the customers is performedin a far more intelligent way than the traditional centraladministration is able to do. Even to share a taxi is mucheasier: a cab can collect several customers who are standingin short distance from each other without knowing that theyhave the same destination in common.

Researchers and mobile phone enthusiasts put high hopesinto the possibilities of enhancing cooperative behavior withthe means of technological settings. The introduction of multi-hop ad-hoc connections in the proposed service, for example,not only permits those users out of the taxis’ coverage toexploit the service just by using the other people’s terminals as

relays, but also to create groups of customers that may shareall or part of their trip, thus reducing the costs.

Cities do not only challenge our civility and our willingnessto behave in a cooperative manner, they also challenge ourability to be mobile. Urban environments are demanding and,though everything seems dependant upon mobility, it is exactlyimmobility that is sometimes the result of urban traffic –real, as well as virtual traffic. Furthermore, to coordinatethe actions of inhabitants and visitors of big cities is oftendifficult to be achieved. In New York, for example, severalinitiatives have been launched in order to install Wi-Fi APsand cell phone antennas on lampposts, traffic signals and otherplaces all over the town, with the aim of enabling a bettercoordination of action and providing infrastructure for spatialas well as virtual mobility. The mobile phone is the bestexample for a new mixture of these two types of mobility:the virtual mobility to overcome the spatial distance betweenthe communication partners is combined with a newspatialmobility of the mobile phone itself, since it is not fixed andtightened to a wired line. In business as well as in leisuretime, different types and combinations of spatial and virtualmobility will occur as prerequisites for modern societies. Thetaxi ride service illustrates that spatial and virtual mobility arebecoming interdependent and that the mobile phone is used toenhance the spatial mobility.

V. CONCLUSIONS

This paper has proposed a new ITS service, which solvesa daily problem encountered by most people living in ametropolis: how to catch a taxi in the most time efficientlymanner. Since in our approach the user is considered asthe first stepping stone towards the definition of 4G, all theavailable technologies are working together to achieve onegoal: solve locally a critical situation for him. Furthermore,we have shown that the service architecture is an example ofthe pillars that defines 4G as a convergence platform that en-compasses cellular and short-range communications systems.In conclusion, the synergy with the forthcoming generationof communication technologies is shown to efficiently supportITS systems, addressing problems related to transportation.

VI. A CKNOWLEDGEMENTS

This work has been supported by Samsung Electronics, Co.,LTD, Korea.

REFERENCES

[1] S. Frattasi, H. Fathi, F. Fitzek, M. Katz, R. Prasad, ”A PragmaticMethodology to Design 4G: From the User to the Technology”, inProceedings of the 4th International Conference on Networking (ICN),IEEE, Reunioun Island, France, April 17-21, 2005.

[2] S. Frattasi, H. Fathi, F. Fitzek, K. Chung, R. Prasad, ”4G: The User-Centric System”, Mobile e-Conference (Me), Electronic Conference,August, 2004.

[3] S. Frattasi, B. Can, F. Fitzek, R. Prasad, ”Cooperative Services for 4G”,in Proceedings of the 14th IST Mobile & Wireless CommunicationsSummit, Dresden, Germany, June 19-23, 2005.

[4] Simone Frattasi, Marco Monti, Daniele Teotino, Mirko Antonini, MarinaRuggieri, Ramjee Prasad, ”The Next Generation of Mobile LocalizationSystems”, in Proceedings of the 11th European Wireless Conference(EW), Nicosia, Cyprus, April 10-13, 2005.