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Technology Stocks : Qualcomm Moderated Thread - please read rules before posting -- Ignore unavailable to you. Want to Upgrade?

To: pheilman_ who wrote (23170)	5/30/2002 8:41:35 AM
From: David E. Taylor	Read Replies (2) \| Respond to of 196644

Paul: ...At least Cambridge Positioning Systems didn't try to claim this was new technology, differential time of arrival has been public domain for decades. But that's the very excuse they are in fact using (since they apparently can't come up with any other) - from the article Rose posted: EOTD uses up to four different cellular base stations to figure a cell phone's location, measuring the arrival times of the call at various different cellular antennas. But in rural areas, cellular base stations are sometimes miles apart. Instead of four, it's likely there will be just two base stations to help figure out the location, making it less accurate, Wade said. "This is not developing an IP router or a new kind of modem," he said. "This was brand new, completely unthought-of-before technology that takes a long time." [My emphasis] I thought QCOM's SnapTrack GPS approach works on GSM/TDMA as well as CDMA. Is the AWE, Cingular and Voicestream use of EOTD just the result of their resistance to paying QCOM for anything? David T.

To: pheilman_ who wrote (23170)	5/30/2002 11:14:27 AM
From: rkral	Read Replies (1) \| Respond to of 196644

Re: E-OTD (Enhanced-Observed Time Difference) technology "The linear array of stations doesn't give additional information on the radius to the mobile." No radius information? Obtaining three radii for three BTSs (to the mobile's location) is exactly how the system works. There's a great graphic at the link below. "Visualize the mobile and both base stations as colinear. All this system can determine is which direction the mobile is from the base stations, it cannot make any statement about where the mobile is along the road .. " Actually, I believe the colinear case is the only case where two BTSs are "sufficient". Visualize two stations as 10 km apart. The E-OTD method shows the mobile to be 6 km from one BTS, and 4 km from the other. That's a fairly good statement of position. Of course, after accounting for measurement errors, the actual location could be quite some distance to either side of the road .. worst when the mobile is at the midpoint between BTSs, imho. A third colinear BTS, at a greater distance from the mobile than the first two BTSs, would be of no help. You've used the terms "linear array" and "direction". Seems to me you are thinking of E-OTD as a Loran-like technology. It's not. Ron cursor-system.com