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Wireless Positioning
An anonymous reader writes "This Intel-written whitepaper introduces a way to determine location with the aid of freely accessible, nearby radio sources, such as fixed Bluetooth devices, 802.11 access points, and GSM cell towers. Basically, the device reads the IDs of these local 'radio beacons' (each of which has a unique or semi-unique ID), looks up their positions in a locally-cached database, and performs a computation akin to triangulation. Intel created Place Lab in an effort to satisfy the emerging requirement for location-awareness within mobile devices such as smartphones, PDAs, and laptops, or even moving vehicles. According to the whitepaper, over four million of the required radio beacons have already been mapped."
Sounds interesting. As geeky teens we tried making our own positioning system using 3 transmitters, one receiver and a PC. It never worked well as we didn't know how to properly encode the current time into the 'pings' to calculate the transit time.
Do all these broadcast cells broadcast the time code? Are the clocks in sync or do they need to be? I'm guessing without a way to "time" pings received, there's no easy way to validate your position.
The "need" to find yourself seems sort of a waste for most. GPS is nice but I'm more interested in real time user voting on traffic (on their road, in their direction). GPS + realtime traffic heuristics could offer faster escape routes during evacuations, or better gas mileage by avoiding idle periods.
Before: This Intel-written whitepaper introduces an determine their locations...
After: This Intel-written whitepaper introduces a way to determine location...
I really thought I had suddenly become retarded and couldn't parse english anymore. Thankfully, and quick edit proved me wrong.
Really wierd to see revisions as they happen on the front page.
Sony ha
Network pings are named after the more traditional sonar ping, though. What the poster above you was saying is that he and his teen buddies had trouble timestamping the signals their transmitters were putting out. He and his friends were trying to do a transit time based triangulation, so this information was pretty critical.
On the other hand, I don't think the timing information in a computer is really precise or reliable enough to do a timing based calculation. Certainly you wouldn't rely on the timing of four million independent devices to be synched. This intel system seems to work on signal strength.
Yeah, the GSM towers may not move, but if you RTFA, it mentions 2.2 million beacons, made up mostly by 802.11 AP's. However, take the example of only using immobile devices. What about catastrophe, and simple upgrades that are not in precisely the same location (ie, the opposite side of the same farmer's field). I did rtfa, and it didn't seem clear what the system would do in the case that a known mapped beacon changed location. In a largely populated city it would probably throw out the erroneous data because it does not match what is expected. But what does it do in a less dense area that only recieves a few beacons? In that scenario, I don't see how it could know that the data is erroneous, so I would assume it gives incorrect location information. It's still better than nothing, and it's great that people are trying to solve the problem. But from what I just read about this, I don't think it's ready for commercial use yet.
I am no expert, but I think the reason they have GPS is this: Some cell phones use a time modulation technique to fit multiple users on a small frequency range that was allotted to them. This technique involves shifting parts of your signal in the sub-microsecond range (I dont actually know how fast the shifts occur), and as such require very precise timing (if not the tower and phone would not be in sync I suppse). GPS is the most logical way to achieve this, as GPS sat's transmit the current time as well (each GPS sat has an atomic clock on board). So, they use GPS to get extremely accurate times, which are then used for what I can only describe as their 'ninja-foo' signal manipulation to fit many users in a rather limited frequency space.
Check your phone's service menu. On my LG, I can get there by pressing Menu-0-000000. There's probably a test screen you can use to check your GPS information.. if the towers in your area support it. Note that not all positioning information is available on your phone - the tower plays a big part in finding your location when you use E911.
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Why can't the beacon devices themselves use this method to locate themselves relative to each other? Add a protocol for exchanging this information, and whatever devices are in the neighborhood could quickly reach a consensus as to their relative positions. And if one or more of them are GPS-enabled, voila, we have automagical mapping.
This idea was used in at least one Vernor Vinge story, "Fast Times at Fairmont High". The protagonists dropped wireless routers as "breadcrumbs" and after about four were down, they could accurately identify their position (relative to the routers).
Well, of course! I work on WiFiMaps.com, and we've been talking about doing this for years. It's the only natural outcome of wardriving data, if you think about it. There are few people developing location-based applications at this time, but there are a bunch of them. Some of the stupider people are trying to make a buck out of it, but this is just another feature of this Ubiquitous Computing that some of us are working on.
We've decided to GPL our data, so anyone can develop Google Mashups, or their own applications. In the meantime, we'll continue to collect data, homogenize it, and push it out for everyone to play with. Reminds me that we should mention this to the Placelab folks again.
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