Location Based Web Search on GSM/GPRS Mobile ... - WWW2006

<strong>Location</strong> <strong>Based</strong> <strong>Web</strong> <strong>Search</strong>
on GSM/GPRS Mobile Devices
VVS. Naresh, Prasad Pingali, Vasudeva Varma
International Institute of Information Technology, Hyderabad, India
Murali Krishna Punaganti Venkata
Nokia Research Center, Helsinki, Finland

Agenda
•Introduction
• Solution Outline
• Steps Involved
•Open Issues

Current search
• Obtained from http://mobilesearch.nokia.com

Introduction
• Goal of this project : Provide a <strong>Location</strong> <strong>Based</strong>
<strong>Search</strong> (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”
• <strong>Location</strong> 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
<strong>Location</strong>
– <strong>Web</strong> search using <strong>Location</strong>.
• 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 <strong>Location</strong> needs to be inferred
– Get <strong>Location</strong> Codes from Device
– Lookup <strong>Location</strong> Codes to get <strong>Location</strong> Names
• <strong>Web</strong> <strong>Search</strong> Using <strong>Location</strong>
– Query Expansion
– <strong>Web</strong> Meta-<strong>Search</strong>
– Merge and Rank <strong>Search</strong> Results using a Weighted
Ranking function.
– Default Ranking is based on Granularity of
<strong>Location</strong>.

Obtain Mobile Device <strong>Location</strong>
• 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
• <strong>Location</strong> 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
• <strong>Location</strong> Area Code (LAC) and
• Cell ID

Get <strong>Location</strong> 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.i<strong>Location</strong>AreaCode; //<strong>Location</strong> Area Code
TInt cellId = ni.iCellId;
//Cell ID

Query Expansion & <strong>Search</strong>
• Query Expansion for each <strong>Location</strong> 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
• <strong>Search</strong> Results merged, ranked using
granularity of location.
• Ranking function weights are tunable.

Example <strong>Location</strong> <strong>Based</strong> <strong>Search</strong> for
“Chinese Restaurant”

Example <strong>Location</strong> <strong>Based</strong> <strong>Search</strong> for
“Chinese Restaurant”

Example <strong>Location</strong> <strong>Based</strong> <strong>Search</strong> for
“Chinese Restaurant”

Example <strong>Location</strong> <strong>Based</strong> <strong>Search</strong> 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 B
Service Provider C

MCC – 404 - India

LAC – 2711 Hyderabad

CellID – 04BE
Banjara Hills

Obtaining the <strong>Location</strong> Database
• Difficulty in Obtaining <strong>Location</strong> Database
because
– Three of the four <strong>Location</strong> 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 <strong>Location</strong>
mapping in desktops.
• Open issues
– User Privacy
– Security

Questions??