Implementing Location Based Information/Advertising for Existing MobilePhone Users in Indoor/Urban Environments

Omer Rashid, Paul Coulton, and Reuben EdwardsInformatics, Infolab21, Lancaster University, Lancaster, LA1 4WA, UK

m.rashid,p.coulton,r.edwards@lancaster.ac.uk

Abstract

In the emerging world of m-commerce potentialusers consistently cite location based services as atechnology they would be interested in using. However,solutions to obtaining the specific location of the userpredominately rely on the provision of additionalhardware and/or software within the mobile phone orthe system infrastructure. These techniques are ofteninappropriate for indoor and highly urbanenvironments where the line of sight to the locationmeasurement unit is often unavailable resulting ininaccurate and unreliable positional information. Inthis paper we present a system that can be used withany current mobile phone system to provide locationbased information/advertisements to any mobilephone, equipped with Bluetooth technology, withoutany necessity of installing client side software. Thesystem can be used to provide systems such as locationbased information for tourist in cities or museums orlocation based advertisements.

1. Introduction

Mobile commerce (m-commerce) can be generallydefined as a set of business activities conducted overmobile and wireless networks using applications onhandheld devices. M-commerce not only includes e-commerce applications, but also many new andinnovative applications, such as those shown in Figure1, that are only possible on the mobile and wirelessnetworks [1]. The particular features of mobilenetworks that will enable these innovative applicationsare:

• mobility;• personalization;• and ability to be always online.

The personalization of mobile devices has alreadyappeared in the different hardware configuration andwith the advent of standardized operating systems and

location based information we can also personalize theinternal applications [2].

Mobile EntertainmentServices

Wireless andMobile

Networks

Mobile Auctionsand GamesMobile Information/

Advertising

Product Location Tracking

User MobileBanking

Mobile FinancialApplications

Specificusers

Auction/gameserver

Micro paymentsfor productsand services

Specificlocations

Userpreferences

AdvertisingDatabase

��������������������������������� �������������������������� �������������������������� �������������������������� �������������������������

Some applications may be very location-centric withthis becoming the core of the entire product, forexample, mapping applications and tools to find theshortest route and the closest restaurant. Otherapplications may use location information to provideinformation or advertisements relevant to a particularuser at their current location, for example, suggestingmy favorite type of restaurant in a town were I amvisiting along with suitable place to park. Such locationbased information is expected [3] to have a significantinfluence on user behavior.

Providing location information to facilitate theseservices is far from straight forward and often requiressignificant changes in software and hardware toproduce high degrees of localization. In this paper wepresent a solution that can provide location basedinformation/advertisements at an accuracy of around10m to any current mobile phone equipped withBluetooth technology. Furthermore, whilst othersystems using Bluetooth have been proposed [4], [5],

Proceedings of the International Conference on Mobile Business (ICMB’05)

0-7695-2367-6/05 $20.00 © 2005 IEEE

[6] they utilize client side software whilst this systemrequires no software to be installed on the phone andwill allow users to instantaneously ‘opt-in’ to theservice.

In order that we can place the systems in context weshall discuss more general mechanisms for providinglocation based systems in section two along with theirperformance constraints. In section three we willdescribe the generic Bluetooth system for providing arange of services before highlighting its use inparticular scenarios in section four. Section five definesthe implemented application design for the scenariosdiscussed in section four before we draw our finalconclusions in section six.

2. Providing the Location of a Mobile User

Although we often consider the requirement forproviding the location of a mobile user as a newproblem, in fact all mobile systems effectively track auser’s whereabouts at the cellular level. Each cell sitehas a unique Cell-ID which enables the system tolocate a mobile user so that it can route calls to thecorrect location. While the Cell-ID is easily found(typically acquisition around 3 seconds) its accuracy isentirely dependent on the size of the cell. Cell sizesvary dependent on the capacity requirements of aparticular geographical area of coverage and for 3Gsystems this could range anywhere between cell radiusof 100m to 10 km. Therefore accuracy would beextremely variable although it would require nomodifications to either the mobile handset orinfrastructure.

Finding the location of a specific mobile user with amuch greater degree of accuracy requires systems thatare based on the measurement of pre-definedparameters of a received signal that enables theposition of the mobile user to be inferred. The signalitself could be one used for the mobile communicationitself or specifically provided for locationmeasurement. This signal coupled with themeasurement parameters and the accuracy required hasa direct effect on the complexity required for thesolution. Although the measured parameters could beeither based on Time of Arrival (TOA) or Angle ofArrival (AOA), TOA systems dominate the solutionscurrently being considered and can be based absoluteof relative time. These are the ones considered in detailas part of this section.

Location finding is a relative exercise, in otherwords the location of the mobile user must be estimatedagainst some known framework. This framework couldbe elements such as the locations of the base stations of

a mobile phone network or the satellites of the GlobalPositioning System (GPS). Each system will providedifferent levels of performance and capabilities as weshall discuss in the following sub-sections but bothrepresent significant improvements over the simpleCell ID system.

2.1. Enhanced Observed Time Difference

The Enhanced Observed Time Difference (E-OTD)solution is based on the measurement of signalsoriginating from numerous cell sites which containinformation on differential propagation distances (thisis often referred to as a Time Difference of Arrival(TDOA) mechanism, when synchronized to a commontime base. In GSM systems where transmissions are notsynchronized additional network devices calledLocation Measurement Units (LMUs) can be utilized.These devices measure TDOA at numerous sites andthen calculate correction values. These values arecollected and used to enable correction of the rawTDOA measurements. These corrections can be sent toeither the mobile handset or the centralizedinfrastructure, as shown in Figure 2., depending wherethe calculation is performed. Generally, the number ofLMUs will be less than the number of cell sites and canbe located such that they maximize the precision of themeasurement which means that means they will oftennot be co-located with cell sites. The locationmeasurement could normally be made in around 5seconds and achieve an accuracy of 50 to 125m.However, if the line of sight measurement isunavailable and/or the signal undergoes multipath,system accuracy is severely compromised. Althoughnew hardware would have to be employed only asoftware update is required at the handset.

LocationCalculation and

Control

ServingSite

NeighbourSite #1

NeighbourSite #2

Handset

Synchronised Sitesor LMUs

���������������������������������������� ������������� ������������� ������������� ���������

Proceedings of the International Conference on Mobile Business (ICMB’05)

0-7695-2367-6/05 $20.00 © 2005 IEEE

2.2. GPS or Assisted-GPS

To the layman the obvious solution to the problemof providing an accurate position of the mobile user isto fit a GPS receiver unit within the mobile handset.However, this implementation would have a number ofmajor restrictions such as the fact that no indoorcoverage would be available and it has an acquisitiontime in the region of 10-60 seconds. Further, manyurban environments would also restrict a mobile users‘view’ of the satellites and it would be unreliable insuch situations. Assisted GPS systems overcome someof these limitations by using knowledge obtained fromthe fixed infrastructure to reduce acquisition time downto approximately 5 seconds and possibly provideindoor accuracy to within 50m. However, as with theprevious system, multipath and the lack of line of sightmeasurement will severely degrade this performance.

GPS Assist andLocation

Calculation

Handset

GPS-SV

������������������������������������������������������������������������������������������������ �����������������

GPS solutions are the most complex of all requiringboth new handsets and additional infrastructure and arelikely to be severely detrimental to handset powerconsumption.

3. Bluetooth Location Based System

Almost every new mobile phone and PDA is nowequipped with Bluetooth and consumers are becomingincreasingly aware of the use and benefits of Bluetooth.This has also resulted in widespread use of Bluetoothdongles through which the users can connect theirdesktop machines to these devices. Other initiatives forBluetooth have been seen in the automotive industrywhich has begun to include Bluetooth access in cars.According to sources [7] Bluetooth enabledmanufactured products will experience a sales increaseof 60% between 2003 and 2008.

In terms of this location based system it enablesBluetooth to be used as a means of targeting users with

specialized content in a specific area at a given time.For example, users in a supermarket could be informedabout a certain discount offer based upon theirpurchasing habits. Such messages can be sent to all theusers in the area with a Bluetooth enabled mobilehandset or PDA. In order that the system can service adiverse range of users and devices no client sideapplication is required thus nothing has to be installed.The information is presented in a very familiar andsimple form of a text message. Figure 4 shows thebasic layout of a system for transmitting messages to allthe devices in a given area.

BT message pushserver

Client

ClientClient

Client

Client

Client

Client

Client

�������!�"#����" ������$��������!�"#����" ������$��������!�"#����" ������$��������!�"#����" ������$����#����%�������#����%�������#����%�������#����%����

The system uses Object Exchange Protocol(OBEX) over Bluetooth to send the information totarget devices. Licensed by Bluetooth SIG from IrDA,OBEX has become even more popular. OBEX istransport neutral, as with the Hypertext TransferProtocol (HTTP), which means that it can work overalmost any other transport layer protocol. OBEX isdefined as one of the protocols in Bluetooth and sitsover RS232 Serial Cable Emulation (RFCOMM)protocol [8]. Moreover OBEX is a structured protocolwhich provides the functionality to separate data anddata attributes. A clear definition of each request canbe given which helps distinguish one request fromanother. Use of other protocols such as RFCOMM orLogical Link Control and Adaptation Protocol(L2CAP), require the applications sending andreceiving information to know how the data is sent andwhen to send the reply. Like Extensible MarkupLanguage (XML) OBEX provides structure to the databeing sent in contrast to other protocols such asRFCOMM which basically send bytes.

This approach can be used to advocate locationbased advertisement at point of sale (POS) or perhapshelp/tour guide systems. In the following section weshall discuss two example implementations.

Proceedings of the International Conference on Mobile Business (ICMB’05)

0-7695-2367-6/05 $20.00 © 2005 IEEE

4. Practical Implementations

Although we presented the basic technology for thesystem in the previous section there are operationalissues dependent on how it is to be employed. Thefollowing sections highlight further elements whichmust be incorporated into the design.

4.1. Supermarket Adverts/Coupons

In this scenario we will consider a systemimplemented in a supermarket to supply customers withthe latest information on products and offers. As it islikely that we have a number of message centersscattered throughout the store one of the majorconcerns is how to make sure that a same message isnever sent twice to one device as users may comewithin the range of the transmitting device more thanonce. The range of Bluetooth radio varies between 10 -100 meters. Most Bluetooth radio’s only have a limitedrange of 10 meters, especially mobile handsets.Receiving the same information within short intervalsis likely to irritate the user and will discourage thefuture use of the service.

To facilitate the fact that devices will roam betweendifferent locations, and to prevent duplicate messages,an integrated backend information system is required.Figure [5] shows the conceptual layout for two sites,each of them pushing messages (adverts/coupons) tothe users.

BT message pushserver

Client

ClientClient

Client

Client

Client

Client

Client

BT message pushserver

Client

ClientClient

Client

Client

Client

Client

Client

Store Devicelist for site 1

Store Devicelist for site 2

Backend Information System

Site 1 Site 2

Roaming Devices

������

�������&�'�#�������������&�'�#�������������&�'�#�������������&�'�#���������������(�������������(�������������(�������������(������))��������))��������))��������))������" ������$��" ������$��" ������$��" ������$����������������������

All devices discovered by individual sites are storedin the database along with the site, where they were lastrecorded, and the messages delivered to them. EachBluetooth push server launches a device discovery aftera fixed interval of time. Devices discovered after eachinquiry are cross checked with the database. Onlynewly discovered devices are recorded in the database

and message is sent to these devices. Devices thatreceived the message in the previous discovery do notreceive this message. If a new store promotion messageis made available in database, next discovery will pushthe message to all the devices in the area. The messagesthemselves can be tagged to expire in the database aftera certain amount of time. Within the same scenario theshopping center could decide to pick a random device,as a lucky winner, to perhaps receive a discount ontheir purchase or perhaps a complimentary item. Thewinner can be notified by a Bluetooth message and thismessage is dispatched to one device only.

Searching for devices at a fixed interval means thatthe information system could obtain lots of informationabout different Bluetooth devices. This information canbe flushed daily and some of it can be used to enhancethe filtering mechanism, for instance a Bluetoothdevice appearing on every search or at a particularmessage center may belong to a store employee orperhaps to an employee of store next door. Suchinformation can be used to improve the intelligence ofthe messaging system in identifying potential customersand the message to be sent out to them. To improve,and better target potential customers, the informationsystem can be altered to remember the devices whotake advantage of the coupon. Upon their next trip tothe store these devices can receive an advert targeted atthe product for which the coupon was issued last time.There are many similar cases that can be implementedwithin this scenario and will be dictated by the store’scurrent sales strategy.

4.2. Guided Tour

In this scenario we consider a system implementedat a tourist attraction providing users with keyinformation about the location. Just like the firstscenario we will have different message centers but thistime they will be sending out different messagesdepending upon their location within a particulartourist spot. The first message could be informationabout the current location while the later messages maybe information about other points of interest at thesame spot or perhaps be the one that informs the userthat this particular tourist spot will close in certainamount of time or may provide list to other touristattractions and directions how to get there. For examplelet us consider this to be implemented at a historiccastle. Upon entry to the castle the user can receive abrief history of the castle. Once the user gets within therange of another Bluetooth site, perhaps located at thecastle courtyard, the user will receive another messagegiving a list of places to see within the castle. Since it is

Proceedings of the International Conference on Mobile Business (ICMB’05)

0-7695-2367-6/05 $20.00 © 2005 IEEE

a large site this implementation will differ from the onein the shopping center in terms of how the messages aredistributed and managed. Different Bluetooth siteswithin the castle will provide different messages to theuser. The information system will keep track of thedevices discovered by each site and the messages sentto them. In this case each Bluetooth message centersends out a particular message to the users unlike theshopping center scenario where each device is workingaround the same set of messages. The database can berefreshed on a daily basis.

5. Application Design

In section four we outlined two scenarios where asystem, like the one presented in this paper, can beimplemented to distribute information to a diverserange of users. In this section we will look at the designof the Bluetooth messaging system itself, although theinformation system will not be discussed in detail as itis beyond the scope of this paper. Figure [6] illustratesdifferent processes involved within the entire system todiscover and send messages to users.

DatabaseBluetooth Server

Site

DiscoverDevices

Send MessageUpdate Database

New

More Messagesto send

Sleep forSpecified short

interval

Yes

No

Old

Check DiscoveredDevice List

Check if deviceis newor old

����������*�������*�������*�������*�����# �����# �����# �����# ��++ ��#������ �(���#��#��++ ��#������ �(���#��#��++ ��#������ �(���#��#��++ ��#������ �(���#��#�����

Every site Bluetooth server initiates a discovery tofind all the Bluetooth devices in the area; some filteringis done to eliminate devices such as headsets orcameras etc. Upon completion of the discoveryprocess, a list of devices found is passed to thedatabase, where all entries are checked. The databasereturns with a list of devices that are new and thosewho have already received messages. Based upon theseresults from the database the system selects appropriatemessages to be sent to different target devices. Therationale of the entire system can be dictated by the

information system at the back end of this messagingsystem. Device filtration takes place at Bluetoothdiscovering site. Devices such as headsets, cameras etcare not included in the request to the Database server.The Database server periodically receives an individuallist from each Bluetooth site associated with it. Eachlist consists of Bluetooth addresses of the discovereddevices along with the ID of the discovering site.Figure [7] shows some of the basic functions that theapplication server must perform on the database.

Shopping center

Device List

Device List

Device List

Sort Devices

Add to DB withdiscovering site

Already in DB

New

Existing device

Existing device, new site

UpdateDiscovering

Site

Send firstMessage

Recover last Message IDChoose nextmessage

to send

Generate individual listsbased upon discovering site

����������������������������,,,,�������#���������-���#���������-���#���������-���#���������-����#������(��$�����#������(��$�����#������(��$�����#������(��$��#�#�#���#�#�#���#�#�#���#�#�#������

After receiving the list of discovered devices in thearea the server sorts them out into three groups namely;new devices, existing devices discovered by a differentmessage center and existing devices within the range ofthe same message center that discovered them last time.At this point as seen from Figure [7] the system adds amessage to each device group. Newly discovereddevices are sent the first message or promotion of theday while the other two categories receive or notreceive a message based upon the last message ID,which was sent to them. Before message centers canreceive the lists, database updates the message ID forevery device currently under consideration. Theapplication server once again sends out separate listsspecific to each site with the message they are to pushto the target device. Based upon these lists, messagecenters send out information to the users. On a givenday users never receive a duplicate message whilstmaking sure that every new device coming into theregion shall receive those messages.

This has been implemented in Java. MySQL hasbeen used as the database and PHP has been used toimplement the server side logic. To cut down the

Proceedings of the International Conference on Mobile Business (ICMB’05)

0-7695-2367-6/05 $20.00 © 2005 IEEE

development time Rococosoft Impronto Simulator [9]was used to simulate the server and the discovereddevices. Impronto Simulator works on a virtual stackand application simulated is easy to transfer to aphysical stack. Figure [8] shows the server nameddevice1 with a few discovered devices.

����������������������������....�������� #�����#����#����������������� #�����#����#����������������� #�����#����#����������������� #�����#����#�������������-�+���������� #���-�+���������� #���-�+���������� #���-�+���������� #�������

Simulator makes it easier to test different conditions inthe system. For example during device discovery alldevices shall be shown; both new and the onesdiscovered in the previous run.

To implement this system aveLink Bluetooth stackwas used from Atinav [10]. There are other stacksavailable that have a JSR82 implementation but not allof them support OBEX. There are two basicapproaches that one can take to implement such ssystem; use a Java API with Bluetooth stack built in oruse Java API that uses an external stack. One of themajor reasons aveLink was selected for this applicationwas the fact that it possesses a fully implemented andself contained Java Bluetooth stack. Other choices inthe same category can be Harold [11] or JavaBluetooth [12] but neither of them are a completeimplementation of JSR82 and do not support OBEX.Although all of them are platform independent butHarold and Java Bluetooth stacks require javax.comm[13] to be installed on the machine running thesestacks.

Options in Java API accessing external stacks areBlue Cove [14], JBlueZ [15], avetanaBluetooth [16]and Impronto Developer Kit [17]. Apart fromavetanaBluetooth the rest are OS dependent. JBlueZworks with BlueZ stack for Linux and Blue Cove iscurrently available for Windows only. ImprontoDeveloper Kit is available for Linux at the momentwhile avetanaBluetooth is not only available forWindows and Linux but also for Mac OS. From theoptions considered only Impronto Developer Kit andavetanaBluetooth support OBEX, which in the light ofabove discussion makes avetanaBluetooth a viable

choice if planning to run the system on an externalstack.

In our view aveLink and avetanaBluetooth are themost suitable choices to go with because not only dothey provide support for OBEX but they also have aversion available for Java 2 Micro Edition (J2ME)which can be used to add on functionality to provideinformation as to “Who’s around” along with “What’saround”. Figure [9] shows a message received by aBluetooth enabled handset.

����������������������������////����" ������$�0�(��� ����#��-�)�1#���" ������$�0�(��� ����#��-�)�1#���" ������$�0�(��� ����#��-�)�1#���" ������$�0�(��� ����#��-�)�1#�������

Users can choose not to accept a connection if theydo not want to receive advertisements. In this case theBluetooth message center shall inform the informationsystem that a particular device does not wish to receivepromotions.

6. Further Work & Conclusions

Obviously there are many other scenarios than thosewe have already mentioned and the proposed systemcould easily be adapted to a number of other possibleuses. One of the great benefits of this system is the factthat it can be deployed without requiring the users to doanything more complicated than switch on theirBluetooth capability and accept the message althoughthis limits the content to text based messages. We havealready seen through the wide scale adoption of SMSthat text only communication is perfectly acceptable asit is the information content that is important.According to Barwise & Strong [18], in SMS m-advertising, 81% of the test subjects viewed all themessages before deleting them and 77% of them didthat as soon as they received the advertisement. Thispredicts a healthy response from the users for thissystem. Since this information is being delivered atPOS, users are more likely to take advantage of theoffer as well.

The proposed system is targeted towards personaldevices such as mobile handsets which users wearalmost everywhere and all the time. Users do not wantto receive spam or receive information without theirpermission. With the system presented in this paper

Proceedings of the International Conference on Mobile Business (ICMB’05)

0-7695-2367-6/05 $20.00 © 2005 IEEE

users can choose whether they want to receiveinformation or not. They can simply turn off Bluetoothreception before entering a shopping center or anyother place that advertises the fact that users canreceive promotional information through Bluetooth. Asimilar example is of Mobiluck [19] which permits itsusers to communicate and exchange information witheach other through Bluetooth. Many commercial areasdisplay the unique Mobiluck sign which can notifyusers to either switch on or off their Bluetoothreception. Moreover with our proposed system usershave the choice not to accept an incoming connectionrequest.

Further, as the more advanced location positioningsystems like those described in section two are addedto mobile phones and supporting infrastructure thissystem could feed the vital indoor and urbaninformation to reduce acquisition time and improveaccuracy. With this enhancement a much broader rangeof LBS can be made available to the users at a varietyof locations. User profiles can be made accessiblebetween different shopping centers or it could even beimplemented as portable platform, for instance in abackpack that allows the wearer to transmitadvertisements to public at concerts or fairs.

NeighbourSite # 2

NeighbourSite # 1

Synchronised Sites or LMU's

IndoorEnvironment

Location Calculationand Control

ServingSite

BluetoothHotspots in an

indoor environment

���������������������������������2�2�2�2����" ������$��" ������$��" ������$��" ������$����+ �������������������+ �������������������+ �������������������+ �����������������

-������������������-������������������-������������������-����������������������

With PDA sales declining [20] and mobileconnections increasing our system is a viable option form-advertisements. It not only makes the user in controlof what they receive but it does not require any clientside software which makes it target a wide range ofBluetooth enabled mobile devices available in themarket.

7. References

[1] U. Varshney, “Mobile Commerce: Introduction, CurrentStatus, Challenges and Future”, IEEE Vehicular TechnologySociety News, Vol. 51 No2, May 2004, pp. 4-9.

[2] C. Anderson, GPRS and 3G Wireless Applications,Wiley, USA, 2001.

[3] P. Kannan, A. Chang, and A. Whinston, “WirelessCommerce: Marketing Issues and possibilities”, 34th HawaiiInternational Conference on System Sciences, 2001.

[4] Locatrix, Locatrix Presence, Proximity and LocationService, Retrieved March 2005, http://www.locatrix.com/pr20050222.php

[5] L. Aalto, N. Gothlin, J. Korhonen, T. Ojala “Bluetoothand WAP Push Based Location-Aware Mobile AdvertisementSystem”, MobiSys 2004, Boston, USA.

[6] E-LBA, European Location Based Advertisement,Retrieved March 2005, from http://www.e-lba.com/

[7] InStat, Market Alert, Retrieved 2004, fromhttp://www.instat.com

[8] J.Bray, C.F. Sturman, Bluetooth Connect Without Cables,Prentice Hall PTR, USA, 2001.

[9] Rococosoft, Impronto Simulator, Retrieved February2005,http://www.rococosoft.com/blue_simulator.html

[10] Atinav, Avelink BT sdk for Java, Retrieved February2005 from http://www.avelink.com/Bluetooth/Products/JSR-82/index.htm

[11] Lund University, Department of Automatic Control,Harold A Bluetooth Stack in Java, Retrieved February 2005from http://www.control.lth.se/%7Ejohane/harald/

[12] WWW.JavaBluetooth.org, The Java Bluetooth Stack,Retrieved February 2005, http://www.javabluetooth.org/

[13] SUN Microsystems, Java Technology, RetrievedFebruary 2005, from

http://java.sun.com/products/javacomm/javadocs/javax/comm/package-summary.html

[14] Source Forge, Project Info. Blue Cove, RetrievedFebruary 2005, http://sourceforge.net/projects/bluecove/

[15] JBlueZ, Java API for Bluetooth, Retrieved February2005, from http://jbluez.sourceforge.net/

[16] avetana, avetanaBluetooth JSR82 Implementation forWindows, MacOS and Linux, Retrieved February 2005, fromhttp://www.avetana-gmbh.de/avetana-gmbh/produkte/jsr82.eng.xml

[17] Rococosoft, Impronto Developer Kit, RetrievedFebruary 2005, http://www.rococosoft.com/blue_dk.html

[18] P. Barwise, C. Strong, “Permission Based MobileAdvertising”, Journal of Interactive Marketing, Vol. 16(1),pp 14-24. 2002.

[19] Mobiluck, Mobiluck Bluetooth Software, RetrievedFebruary 2005, from http://www.mobiluck.com/.

[20] InStat, Market Alert PDA Market Faces Steep Decline,Retrieved March 2005, http://www.instat.com/press.asp?ID=1262&sku=IN0501831ID.

Proceedings of the International Conference on Mobile Business (ICMB’05)

0-7695-2367-6/05 $20.00 © 2005 IEEE