Shravan Gaonkar, Jack Li, Romit Roy Choudhury, Landon Cox, Al Schmidt

Presented by : Gregory Teodoro

A brief overview

Mobile Computing Hardware is increasing in power, and decreasing in cost

such that basic commodity devices will be able to perform work such as participatory sensing. Mobile phones especially, can be used by leveraging their

camera, GPS, accelerometers, and other such sensors to gather information.

Using a multitude of these phones over a large area it is possible to build a “virtual information telescope”. A visual large scale interface, that can quickly shift to small and more detailed specifics.

Combined with these sensors, participating users can record multimedia blogs (video, voice, pictures, ect.).

Deeper in, these blogs can be combined with a user-based query/answer . (ala services such as Cha-Cha, but less personal and more public/social)

Combined, all of these factors form…

…the Micro-Blog Service!

Micro-blog stands to combine all of this information

Idea being to create a network of easily accessible, localized information.

Services - Querying

Querying Service The Micro-blogs main goal is to offer a

querying services, through use of the influx of sensor information, a user can gather information about temperature, weather, available Wi-Fi services

Queries can also require human interaction. Questions can be sent out to an area about

nearby restaurants, locations, the weather, attractions ect… and then answered by people in the area.

Services – Location-Based Queries and blogs can also be

superimposed on a virtual space (map) or a physical space (a part of a city). “Float”. Person A sends out micro-blog about

Restaurant X in Area Y. Person B comes to Area Y and has set an

interest in information on “Restaurants”. Since he’s in Area Y, he’d receive Person A’s microblog about the Restaurant X.

Relies on social participation.

Potential Applications

Tourism On the fly information about attractions in an

area, either through blogs or audio/videos. Can ask questions about services in an area

(parking, hotels, ect) News Services

Users send out and report events they see, or sensors information can create and offer weather announcements. Spontaneity of capturing information and

easier publishing means immediate news reports

Potential Applications (cont.) Micro-Alerts

Location-aware alerts, an example being a college where microblogs can be placed directing users to specific buildings.

Comparable best to floating sticky notes. Social Collaboration

Ability to offer on the fly services, ala Craigslist. Car Pools and Healthcare Reports for

example. Can post queries and questions, and

qualified users can answer them.

Architecture and Design

Location based Micro-blogs require a localization service. GPS, GSM, WiFi, ect

Issue of potential power consumption and accuracy balance. Blog are location-tagged then indexed by originator,

access permissions, themes, ect. Client contacts webserver to access and retrieve a micro-

blog. Users can also send queries to specific regions R.

Using the localization, the database can see if it has any serviceable blogs to send to the user, and attempts to match time, location, and permissions.

If it cannot find an answer, it will send a query to phones in the area that are declared available, and they may answer the query. Any answers are placed onto the map as a new micro-blog, and may

be deleted after a pre-specified lifetime. Users will also automatically received micro-blogs

pertaining to their interests and the region they are in, triggered when the phone updates its location.

Block-Diagram of Micro-Blog

Considerations

Energy Aware Localization Constant running of GPS localization is a heavy drain on energy,

and may not be required for acceptable accuracy. Energy Aware Applications

Applications should adapt to energy needs and efficiency versus performance.

Incentives Why would people answer queries if they don’t have to?

Location Privacy Location-based blogging reveals the bloggers general location,

security and privacy concerns. Spam

Malicious users may use the service to spam other users. Content Inaccuracy

Not all query answers might be correct, and malicious users may outright lie.

Energy Awareness

Rather than using a single localization scheme, we can use a mix. Use GPS to find the general location once,

then use the less expensive WiFi or GSM localizations to keep track.

We only use GPS if we have too, or if the user has traveled a distance above a certain threshold.

Using a technique called war-driving, a map of WiFi Aps can be created, and then used (by detecting if a user is in range) to device a users approximate location.

Interpolated Path

Problems with this…

Does not achieve optimal usage. Sharp turns in a path may not trigger a

change in the WiFi-estimated distances. Will continue to extrapolate the original

direction of movement, and not the sudden turns.

Will not correct itself until a new WiFi fingerprint is created.

Energy Aware Applications Only updates by GPS when required, or

when a blog is actually created and placed. When not created a blog, it will only updated

based on Wi-Fi or cell-based localizations, as exact location or accuracy may not be required.

Delay updating and uploading blogs if battery power is below a certain threshold. Keeps power on the phone in case of an

unforeseen emergency.

Incentives

Why should people answer queries if they don’t need to? Queries can be restricted to social network

A user’s friends would be far more likely to answer than a stranger.

Alternatively a give and take approach Users would be given “query credits” based on how

often they participate and answer other user’s queries. Issues with bogus queries, collusion, cliques, ect. Malicious or misbehaving users can be found through

use of a direction node with a cost representation how often the two nodes query each other.

Monetary costs for sending out queries and answers Plan is to piggy-back on a value package offered by

phone providers.

Locational Privacy

Location-based blogging reveals the bloggers location! A trust is required between the users

and the server administrators at Micro-Blog. A fundamental drawback. They make the assumption that users are

willing to trust Micro-Blog. Offers a private, social, and a public

mode as an alternative.

Spam

The network can be used send spam to users Proposed solution is to limit the amount of

queries a single user can receive from each group (private, social, public) during a time period. Blocks any queries past this point Does not solve the issue!

A user can be spammed to use up the number of queries they want to receive a day, preventing any future legitimate queries from being received.

Content Inaccuracy

Not all information will be correct. Users will receive a reputation based on other user’s

ratings. Akin to other social services like Digg.

The higher a reputation, the more confidence the micro-blog will have that their query answer is correct.

Do not publish answers from sources that are not confident.

PROBLEMS! A malicious user will be quickly locked out, as will

unknowledgeable, but they will still be able to send out some disinformation

No methods to stop a malicious user from acting legitimate to gather a good reputation, and then abusing it

Ties into group/user collusion as well.

Implementation

The Micro-Blog program is placed onto a phone client. Designed specifically to interrupt the normal operations of a

phone as little as possible. System State

System begins in Idle mode User goes to send a blog

When finished, blog is sent out, phone is tagged with location, and then switches to Sync mode

Sync Mode Phone syncs information with the webserver and receives any

new, relevant Micro-blogs, then returns to Idle Log State

Entered periodically where phone updates its status based on sensor data (signal strength, temperatures, cameras, WiFi/GSM IDs, ect), then returns to Idle

Query state A query was receive and appears on the users phone and waits for

an action. Either reply or ignore. Sends it out, then returns to Idle This is also checked periodically.

State Machine for Micro-Blog

Web Infastructure

Phone data is send to a database via TCP, and uploading into a MySQL database server, then indexed into proper relational tables. Blogs in response to an earlier query are sent

out to the approriate users. Apache 2.0 is used to offer HTTP access to

the Micro-Blog over a web browser, where users can request blogs, create blogs, and browse a region map.

Server periodically checks all phones that have a live connection and their user-set constraints and send queries to them as appropriate.

Battery Life and Localization A mix between localization

techniques, and the use of battery must be found. Findings were done using a Nokia N95

phone. Main research was done through the use

of localization trades off. Localization schemes included using

combinations of WiFi, GPS, and GSM.

Findings

Findings (cont.)

Battery life improved using a mix of the localization schemes as appropriate. This still had a negative effect on locational

accuracy As far as the application is concerned the trade-off of

accuracy is worth the improvement of battery life Methods Attempted

Wifi with periodic GPS correction GSM with periodic WiFi Corrections

Proposed accuracy error was a max of 125m, leading to a total of 25 hours of battery life.

GSM with periodic WiFi offered the best battery life vs. localization error, and is used in the Micro-Blog program.

Findings (Cont.)

Reception

Questionnaires were done on participants about the application and how they felt about it. Great for idling periods, but needs a better GUI. Privacy control is absolutely vital, and users

appreciated the ability to control privacy. Incentives may not be an issue if program is

“fun”. Strong correlation between voice blogs being

personal, and text blogs being impersonal. Best time of day is between 5:00-9:00 PM Concerns about battery life minimal because

recharging is easy or imminent.

Paper Strengths

Very good ideas about what the software should do, and some basic logistics behind it.

Highly concerned with battery and location accuracy, and answers the question about what should be used well.

Lots of future potential in the subject at hands.

Does attempt hands-on testing and user-base interaction.

Paper Weaknesses

Ignores a lot of potential networking issues, such as sorting through data, dealing with traffic, packet loss, congestion, among other things

Glazes over some of the privacy and malicious user issues, and does not fully solve them.

Though it was a user study, not many users were involved (only 12), nor were these users varied in location, culture, or age. Needs a far more extensive study of a user-base Paper does admit this as a fault of the study.

Future Work/Follow Ups

Location-Privacy in the General Public A far broader audience needs to be

approached with the software and tested. Accelerometer usage

Accelerometers are not used in terms of gauging distance travel and localization techniques

Has potential to be integrated into social networking applications (Facebook, MySpace, Google+)

Methods of identifying and blocking false content need to be developed.

Questions?