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

To: rkral who wrote (23206)	5/30/2002 6:15:02 PM
From: pheilman_	Read Replies (1) \| Respond to of 196649

EOTD....At least Cambridge Positioning Systems didn't try to claim this was new technology. Agreed the frequency reuse will cause problems, but, even without other transmitters, GSM is not very good for doing RF triangulation. It is narrowband. This is why GPS is a spread spectrum transmission, you can time the chips and even sub-chips for accuracy. With a narrowband transmitter and receiver I believe the uncertainty is related to the bandwidth and with GSM at (frantic web search) 200 KHz. The crude method for RF timing is to sample the rising edge and use it crossing a threshold, works poorly as the received power is different at the two BTS. Next step is to use a differential threshold vs. a delayed copy of the signal, works a little better, but notice the edge can never be "faster" than the BW, low bandwidth signal, poor estimate of location. Next clever move is to time off a transmitted timing pattern, still limited by the BW. Now toss in the distant transmitters on the same frequency and it becomes even more difficult to locate a transmitter. Paul

To: rkral who wrote (23206)	5/30/2002 7:20:51 PM
From: mightylakers	Read Replies (1) \| Respond to of 196649

EOTD needs the mobile to hear 3 BTSs .. at the same time? Yes, pretty much, but keep in mind mobile does need to scan for the other pilot signals to get ready for handover. Or do 3 BTSs need to hear the mobile at the same time? It's the mobile doing the listening, that is why EOTD is a mobile based LCS. there are no equivalents to CDMA's rake receivers Rake receiver is not for listening to different signals, but the same signal from multipath, i.e. delay. So it's a different thing.

To: rkral who wrote (23206)	5/30/2002 9:24:36 PM
From: John Biddle	Respond to of 196649

Mightylakers hit it on the head, I believe, when he said keep in mind mobile does need to scan for the other pilot signals to get ready for handover The phone is always talking to every base-station it can see, in order to prepare for and execute a handover. This same simultaneous (or nearly so) communication on slightly differently frequencies is all that's needed for doing the rf part of EOTD. No magic here, not even new technology.