1. Indoor Positioning System
Tony Offer, Christopher Palistrant

2. Basic Concept Function Usefulness Target Users
Make mobile device aware of its location within a building
Use location awareness to provide location-dependent services
Usefulness
Many applications for devices that know where they are
Provision of services based on the context of locality
Target Users
Businesses with large office buildings
Maintenance workers
-- Positioning achieves room-level accuracy (not really need more accuracy than that)
---- Location really means “room number”
-- The system is decentralized so that the device is the first and only to know about its location, unless it chooses to share that information.
-- Map not only shows which room in a building the device is located, but also provides feedback about nearby services, opportunities, or restrictions.
---- Information about location-specific resources on the map could either be statically pre-programmed, or it could come from other devices or other people that choose to broadcast their locations. Rooms could also broadcast information regarding what goes on inside those rooms.
-- Location-aware applications: The intelligent map is the direction we’re headed as far as applications are concerned, but there are several others: SECURITY (Can have a server with private documents on the net, yet only allow people in the same room to log into it), FAST PRINTING (know to print on the printer in the same room).

3. Example Scenario
Start out in office
Locate coworker
Head out toward coworker’s office
Guy in office – looks at screen to find coworker – heads out into
hall – stops by a printer – back into the hall – enters coworker’s
office – computer state changes based on location
Guy starts in his office, needs to get to a conference room he’s never been to before in order to give a presentation
At very beginning, guy
Guy needs to meet another coworker in coworker’s office to work on software that requires direct access to sensitive, private source code.
Before guy leaves his own office (rm. 334, for example), he wants to make sure that his coworker is in his office (say rm. 556). Since coworker has specifically allowed his location information to be published to this guy, the guy can bring up his PDA map application and find his coworker’s blip to make sure that he is in rm. 556.
Assured that his coworker is still in his office, the guy heads out in that direction. He is no longer in a room (since he is walking through hallways), so he no longer has his location information.
Halfway there, guy remembers he needed to print out something to bring with him to his coworker. So guy finds nearest room with a printer, walks into the room, opens the appropriate document on his PDA, and selects the “Print” option. The document automatically prints on the printer in the room because the PDA is aware that it is in the same room as that printer.
With newly printed document in hand, the guy continues his journey to his coworker’s office.
In order to reach his coworker’s office, he must pass through an outer door with keycard access, behind which is a subset of offices that work on sensitive information that is not allowed to leave the area. The guy and his coworker are working together on sensitive information, so they can only work on it in this section of the building.
When the guy finally enters the office of his coworker, new files appear on the guy’s PDA. These are sensitive source code files that are always locked or hidden unless the device is in the correct designated area. Now that the guy is in the correct location of the building to work on the source code, the files become available for reading and writing.
The guy and his coworker work on the source code together for a while, then the guy finally leaves near the end of the day. As soon as he leaves the coworker’s office, the files he was working on become locked or hidden again.
After print stop, continue on to coworker’s office
Arrive at coworker’s office
Notice automatic change in mobile device

4. User Interest User’s degree of automation is increased
Enhanced machine autonomy
Reduced dependence on user input
Device state can change based on location
Current tasks simplified by our system
Selecting the closest office printer
Finding a person in the office building
Changing desktop environment based on inhabited room

5. Architecture Components Process Server beacon Mobile client
Speakers
capability
Mobile client
Microphone
Process
Server beacons emit simultaneous and ultrasound broadcasts
Clients listen for ultrasound
Clients determine location
No centralized management
Uses pre-existing hardware

6. Indoor Positioning System In Action
iPAQ receives room-identifying message
iPAQ hears ultrasound from nearby server beacon
iPAQ identifies its location
Human is not disturbed by inaudible ultrasound

7. Expected Effort Remaining components Minimum requirements
No additional hardware needed
Need software to communicate over
Need software to sample and analyze incoming sound
Minimum requirements
Single beacon with card
Implement location-awareness
Desired Functionality
N beacons with less than or equal to N broadcast points
Implement interactive map application
No additional hardware because our project’s major goal is to use pre-existing hardware.
FFTW

8. Expected Effort (continued)
Unknowns
Reliability of ultrasound broadcast
Capabilities of the iPAQ recording system
Processing power of the iPAQ
Contingencies
If iPAQ is not sufficient
Recording system: Attach external microphone
Processing power: Use simpler DFT library
Anything else: Use laptop as mobile client
If ultrasound is unreliable
Experiment with different hardware arrangements

9. Related Work Cricket (MIT) Active Bat (AT&T) Similarities Differences
Uses a combination of radio waves and ultrasound to determine location
No central management
Differences
Uses specialized $10 beacons and receivers
Determines 4x4 ft region within a room
Active Bat (AT&T)
Uses a central management server to perform computations
Uses specially made hardware for tags and sensors
Determines location within a room to an accuracy of 9 cm

10. Related Work (continued)
Context-Aware Computing With Sound (Intel Research, Cambridge)
Similarities
Uses standard computer speakers and microphones to generate and detect ultrasound
Differences
Modulates ultrasonic sound waves to carry data
Does not provide positioning capabilities

11. Distinctiveness Ideas borrowed from other projects
Emission and detection of ultrasound to signify room-level activity
Production and sampling of ultrasonic frequencies using standard computer speakers and microphones
Unique aspects of our project
Utilizes pre-existing, standard office hardware to accomplish its goals
Distinguishes itself from the Cricket and Active Bat projects
Trades high-level accuracy for simplicity and ease of deployment

12. Burning Questions
Will the iPAQ and other standard mobile devices be able to perform fast Fourier transforms?
Is our system crippled by the inability of a mobile client device to be made aware of its location in hallways?

13. Evaluation Major evaluation metrics
Cost
Our system should only use readily available hardware
Reliability
Our system should provide accurate and consistent location determinations
The rate of error for false positives and negatives should be as low as possible
Desired information from user studies
Usefulness of the system
Reliability of the location determination
Speed of update when transitioning between rooms