Location-Based Services

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Location-Based Services

• Henning Schulzrinne
• Columbia University

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Overview

• Time space
• Getting location information
• Using location information
• Privacy issues

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Getting location information

• Universal
• anywhere in the world
• independent of network connectivity
• Non-proprietary
• Energy efficient
• Accurate to 10 m/room level

doesnt exist in one system
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Location-determination methods
Method GPS 802.11 protocols cell tower manual
layer L2 L2, L3, L7
accuracy 10m 20-100m room-level, AP 100 m-2 km room or building AP
advantages privacy global accurate simple to implement reasonably accurate room-level accuracy no surveying needed no infrastructure cost client privacy no infrastructure privacy
problems mostly outdoors requires survey only works in urban areas requires Internet connectivity mapping IP address to switch port? low accuracy cell coverage stationary only doesnt scale
use Enterprise home LANs Enterprise home LANs Some ISPs DSL, cable backup for other methods enterprise home PC
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Location delivery protocols
Method LLDP-MED DHCP HELD
layer L2 L3 L7 (HTTP)
accuracy room-level, AP room-level, AP room-level, AP
advantages simple to implement built into switch direct port/room mapping simple to implement network locality traverses NATs can be operated by L2 provider
problems may be hard to automate for large enterprises mapping MAC address to location? mapping IP address to switch port?
use Enterprise home LANs Enterprise home LANs Some ISPs DSL, cable ISPs
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Location-based services
Foundations of Location-based Services (Steinger,
Neun, Edwardes), modified)
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Location-based services

• Finding services based on location
• physical services (stores, restaurants, ATMs,
  ...)
• electronic services (hot spots, printers, ...)
• Using location to improve (network) services
• incoming or outgoing communications adapts to
  location
• Using location to provide information
• tourist guides
• advertisements
• Making others aware of user location
• presence (individual)
• popularity, movement (group)
• Security
• grant access based on users location

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Location-based VoIP services

• Location-aware inbound routing
• do not forward call if time at callee location is
  11 pm, 8 am
• only forward time-for-lunch if destination is on
  campus
• do not ring phone if Im in a theater
• outbound call routing
• contact nearest emergency call center
• send delivery_at_pizza.com to nearest branch
• location-based events
• subscribe to locations, not people
• Alice has entered the meeting room
• subscriber may be device in room

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Citysense.com (alpha consumer app)
See the city in true realtime how busy is the
city where is everyone going, right now?Red
all anonymous destination activity Green only
unusual destination activity Press 1 to see the
1 hottest destination, then 1 again to see the
restaurants and bars there, etc. Now available in
San Francisco, more cities rolling out in beta
version.
Aggregate GPS information
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Minimum Volume Embedding
Machine learning algorithm that determines
behavior and clusters from anonymous aggregate
movement from all pairs of corners in the
city. Obtains behavioral map of city (vs.
geographical map)
Work
Restaurants
Nightlife
Residential
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Platforms
missing network connectivity
missing navigation
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IETF GEOPRIV and SIMPLE architectures
DHCP
XCAP (rules)
notification interface
publication interface
GEOPRIV
SUBSCRIBE
SIP presence
PUBLISH
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Privacy issues

• Not all LBS are privacy-sensitive
• where is the the M125 bus?
• navigation with GPS
• Problem location personal identity
• or derivable (e.g., via home location)

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Privacy threats
reveal device anonymously (e.g., nearest gas
station)
reveal identity location to LBS (friend finder
service)
Privacy
reveal to individual (friend, other)
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Presence and privacy PIDF-LO

• All presence data, particularly location, is
  highly sensitive
• Basic location object (PIDF-LO) describes
• distribution (binary)
• retention duration
• Policy rules for more detailed access control
• who can subscribe to my presence
• who can see what when

lttuple id"sg89ae"gt ltstatusgt ltgpgeoprivgt
ltgplocation-infogt ltgmllocationgt
ltgmlPoint gmlid"point1 srsName"ep
sg4326"gt ltgmlcoordinatesgt374630N
1222510W lt/gmlcoordinatesgt
lt/gmlPointgt lt/gmllocationgt
lt/gplocation-infogt ltgpusage-rulesgt
ltgpretransmission-allowedgtno lt/gpretransmissi
on-allowedgt ltgpretention-expirygt2003-06-2
3T045729Z lt/gpretention-expirygt
lt/gpusage-rulesgt lt/gpgeoprivgt lt/statusgt
lttimestampgt2003-06-22T205729Zlt/timestampgt lt/tupl
egt
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GEOPRIV privacy rules

• Conditions
• identity, sphere
• time of day
• current location
• identity as lturigt or ltdomaingt ltexceptgt
• Actions
• watcher confirmation
• Transformations
• include information
• reduced accuracy
• e.g., only within 5 mile radius

• User gets maximum of permissions across all
  matching rules
• privacy-safe composition removal of a rule can
  only reduce privileges
• Extendable to new presence data
• rich presence
• biological sensors
• mood sensors

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Open technical and standards issues

• Universal APIs
• As simple as gettimeofday()
• Not specific to method or vendor
• Crowd-sourcing
• Integration between presence and location
• presence as universal third party interface?
• Clear privacy rules
• both technical and legal

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Deployment issues

• ISPs need to make location available to their
  customers
• for in-door use
• location as a chargeable service?
• LAN-based location for room-level location
• APs and ports
• enterprise