location based web search on gsm/gprs mobile devices · location based web search on gsm/gprs...
TRANSCRIPT
Location Based Web Searchon GSM/GPRS Mobile Devices
VVS. Naresh, Prasad Pingali, Vasudeva VarmaInternational Institute of Information Technology, Hyderabad, India
Murali Krishna Punaganti VenkataNokia Research Center, Helsinki, Finland
Agenda
• Introduction• Solution Outline
• Steps Involved
• Open Issues
Introduction
• Goal of this project : Provide a Location BasedSearch (LBS) for GSM/GPRS based mobile devices.
• GSM is a dominant mobile phone system.• Mobile devices most suited for location based
services, because they are “mobile”• Location based services were tried on desktops using
IP addresses for anonymous users.– e.g. URL redirection based on user's IP address
Solution Outline
• The solution can be seen as two main steps– Obtain Mobile Device
Location– Web search using Location.
• Difficulties Involved– Obtaining the location string
database– Refining and re-ranking results
• Open Issues– Standardization of location
parameters– Privacy Issues– Security Policies
Steps Involved
• Displayed location string not accessible for third-party applications
• Mobile Device Location needs to be inferred– Get Location Codes from Device– Lookup Location Codes to get Location Names
• Web Search Using Location – Query Expansion– Web Meta-Search– Merge and Rank Search Results using a Weighted
Ranking function.– Default Ranking is based on Granularity of
Location.
Obtain Mobile Device Location
International Mobile Subscriber Identity (IMSI)used for identifying a mobile phone subscriberMaximum length of code being 15 symbols Composed of three different parts
MCC (Mobile Country Code)3 digits fixed length
MNC (Mobile Network Code)1-2 digits, variable length
MSIN or MIN (Mobile Station Identification Number) maximum 10 digits , variable length
Location Parameters of Interest Totally 4 parametersTwo from IMSI which are standardized by ITU-T (The International Telecommunication Union – Telecommunication Standardization Sector):
Mobile Network Code (MNC)Mobile Country Code (MCC)
Two from Service Provider Specific InformationLocation Area Code (LAC) andCell ID
Get Location Information
• The Symbian C++ (series 60 version-2.1) code snippet to get all four location parameters from a mobile device looks like this:
RTelServer server;CleanupClosePushL(server);User::LeaveIfError(server.Connect());User::LeaveIfError(server.LoadPhoneModule(_L("phonetsy.tsy")));RTelServer::TPhoneInfo info;User::LeaveIfError(server.GetPhoneInfo(0, info));RBasicGsmPhone phone;CleanupClosePushL(phone);User::LeaveIfError(phone.Open(server, info.iName));MBasicGsmPhoneNetwork::TCurrentNetworkInfo ni ;phone.GetCurrentNetworkInfo( ni ) ;TInt MCC = ni.iNetworkInfo.iId.iMCC; //Mobile Country CodeTInt MNC = ni.iNetworkInfo.iId.iMNC; //Mobile Network CodeTInt locationareacode = ni.iLocationAreaCode; //Location Area CodeTInt cellId = ni.iCellId; //Cell ID
Query Expansion & Search
• Query Expansion for each Location Name Individually.
• Three types of expansion using – Country name (MCC)– City Name/ Region Name (LAC)– Region Name within City (CellID)
• Region being most granular, Country being least granular information
• Search Results merged, ranked using granularity of location.
• Ranking function weights are tunable.
Example Location Based Search for “Chinese Restaurant”
Example Location Based Search for “Chinese Restaurant”
Example Location Based Search for “Chinese Restaurant”
Example Location Based Search for “Chinese Restaurant”
The above results are from a location in India-Hyderabad- Banjara Hills
MNC – 013 –Service Provider “C”
Service Provider A
Service Provider C
Service Provider B
MCC – 404 - India
LAC – 2711 Hyderabad
Banjara Hills
CellID – 04BE
Obtaining the Location Database
• Difficulty in Obtaining Location Database because– Three of the four Location parameters vary across
service providers except MCC (Mobile Country Code).
• Used community effort to populate the database.
• Application prompts user to identify any unknown location codes. Users help populating the database.
Issues
• Not all location parameters are standardized. Therefore makes the task much more complicated than IP address to Location mapping in desktops.
• Open issues– User Privacy– Security
Questions??