location based web search on gsm/gprs mobile devices vvs. naresh, prasad pingali, vasudeva varma...
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Location Based Web Searchon GSM/GPRS Mobile Devices
VVS. Naresh, Prasad Pingali, Vasudeva VarmaInternational Institute of Information Technology, Hyderabad, India
Murali Krishna Punaganti Venkata Nokia Research Center, Helsinki, Finland
Current search
• Obtained from http://mobilesearch.nokia.com
Introduction
• Goal of this project : Provide a Location Based Search (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 subscriber Maximum 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 parameters Two 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 Information Location Area Code (LAC) and Cell 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 Code
TInt MNC = ni.iNetworkInfo.iId.iMNC; //Mobile Network Code
TInt locationareacode = ni.iLocationAreaCode; //Location Area Code
TInt 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”
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
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
