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Published byMoses Cannon Modified over 8 years ago
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ORBIT: Multimedia Messaging & location- based services Henning Schulzrinne Columbia University
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Overview Disconnected ad-hoc networks multi-modal networking 7DS prototype Location-based services location determination service creation privacy policies
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Wireless Network: filling the infrastructure-ad hoc gap Wireless networks: Ubiquitous, fast, cheap: pick any two… Currently, varies from 0.1c to $4/MB Research has primarily explored: one-hop infrastructure extension (2G, 3G, 802.11) multi-hop connected ad-hoc networks (mesh networks) But: 2G/3G bandwidth will remain low and precious hot spots not ubiquitous ad hoc networks don’t scale brittle if spanning large areas Our proposal: use mobile nodes to carry data to and from infrastructure networks
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Applications Tourism: get information about sights, travel, public transport schedules,.. upload picture postcards and video recordings Transportation: users in buses and trains leverage data capability Emergencies: propagate “I’m alive” and rescue information Mobile sensors: sensors spread too far to communicate directly with each other large sensor data objects
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7DS – a framework for intermittently connected networks Two directions for data: Internet mobile nodes mobile nodes Internet Each in multiple hops but not routed highlow high7DS802.11 hotspots lowsatellite SMS? voice (2G, 2.5G) bandwidth (peak) delay
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Realization
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Average Delay (s) vs Dataholders (%) Peer-to-Peer schemes medium transmission power high transmission power
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Current status: prototype Initial Java implementation search not just by URL, but by content greater likelihood of finding appropriate material (“news”) Working on PDA implementations Also, considering Linux embedded systems low-power, self-contained
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Combining cellular and 7DS networks Proposed research use ubiquitous, low-speed networks for control some only one-way (satellite, XM, Spot) short-range, multi-hop for bulk data transmission Cellular reselling pay once for bandwidth, use many times Inverse multiplexing for high-priority content Content location find nearest hotspot Cache cleaning indicate popular content for proactive querying remove stale content in mobile Internet case Incentive management reputation management credit for delivering data
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Location-based services Finding services based on location physical services (stores, restaurants, ATMs, …) electronic services (media I/O, printer, display, …) not covered here Using location to improve (network) services communication incoming communications changes based on where I am configuration devices in room adapt to their current users awareness others are (selectively) made aware of my location security proximity grants temporary access Privacy rules for access to context data
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Location-based services & SIP We’re using SIP (and SIMPLE) as generic protocols for effecting change (“actuators”) send MESSAGE to devices distributing event information (“sensors”) Advantages: people and rooms identified by URIs sip:hgs@cs.columbia.edu sip:cepsr815@cs.columbia.edu cross-domain, with extensive security mechanisms domains don’t need to trust each other scalable to global system many other systems are mostly local
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Location-based services Presence-based approach: UA publishes location to presence agent (PA) becomes part of general user context other users (human and machines) subscribe to context call handling and direction location-based anycast (“anybody in the room”) location-based service directory Languages for location-based services building on experience with our XML-based service creation languages CPL for user-location services LESS for end system services
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Location information geospatial longitude, latitude, altitude civil time zone, country, city, street, room, … categorical type of location properties of location privacy (“no audio privacy”) suitability for different communication media
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Determining location GPS may not be practical (cost, power, topology) Add location beacons extrapolate based on distance moved odometer, pedometer, time-since-sighting idea: meet other mobile location beacons estimate location based on third-party information
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PA device controller SUBSCRIBE to each room SUBSCRIBE to configuration for users currently in rooms 1.discover room URI 2.REGISTER as contact for room URI tftp HTTP Example: user-adaptive device configuration SLP “all devices that are in the building” RFC 3082? 802.11 signal strength location REGISTER To: 815cepsr Contact: alice@cs SIP room 815
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Architectures for (geo) information access Claim: all using protocols fall into one of these categories Presence or event notification “circuit-switched” model subscription: binary decision Messaging email, SMS basically, event notification without (explicit) subscription but often out-of-band subscription (mailing list) Request-response RPC, HTTP; also DNS, LDAP typically, already has session-level access control (if any at all) Presence is superset of other two
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Presence/Event notification Three places for policy enforcement subscription binary only policy, no geo information subscriber may provide filter could reject based on filter (“sorry, you only get county-level information”) greatly improves scaling since no event-level checks needed notification content filtering, suppression only policy, no geo information third-party notification e.g., event aggregator can convert models: gateway subscribes to event source, distributes by email both policy and geo data
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Presence model subscription policy event generator policy subscriber filter rate limiter change to previous notification? for each watcher subscriber (watcher) SUBSCRIBE NOTIFY
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Policy rules There is no sharp geospatial boundary Presence contains other sensitive data (activity, icons, …) and others may be added Example: future extensions to personal medical data “only my cardiologist may see heart rate, but notify everybody in building if heart rate = 0” Thus, generic policies are necessary
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Processing models Sequential model: for each subscriber, apply rules to new data doesn’t scale well to large groups Relational database model: re-use indexing and other query optimizations well-defined query and matching semantics e.g., mySQL and PostGres have geo extensions At time of subscription: SELECT address FROM policies WHERE person=$subscriber (AND now() between(starttime,endtime) OR starttime is null) AND (a3=$a3 or a3 is null) …
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Conclusion 7DS as extension of infrastructure and ad- hoc networks Combine benefits of low bit-rate, but ubiquitous and high bit-rate, but sparse networks Location-based services as core wireless service from location determination to location management and privacy
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