Have you ever taken the fourier transform of a square wave, read anything about termination, thought about why people bother to use slew rate controlled drivers, thought about how edge rates effect EMI,...
Didn't think so.
You might want to read "System Design Considerations When Using Cypress CMOS Circuits" at Cypress and bone up on your transmission line theory.
I'll bet that it's off by default. If you leave it on all of the time it will consume more power. Of course this assumes that they are using some form of assisted GPS to achieve a reasonable time to fix.
Does anybody know if this GPS works indoors? (Please don't tell me that it's impossible to get GPS to work indoors because I know for a fact that it's possible.)
Re:GPS can work indoors, in cars, in elevators,...
on
GPS Meets PCS
·
· Score: 1
These guys are trying to use HDTV transmitters as a sort of pseudolite:
http://www.rosum.com/
I think that their idea is to reuse the HDTV transmitters instead of having to install new equipment since it would be less expensive. They may run into other problems since there signal propagation delays could be somewhat unpredictable.
The whole idea of using GPS as a location technology is to reuse a proven technology and not require the installation of an alternate network, or upgrades to an existing network. The signals are strong enough given a sufficiently powerful receiver.
If you want increased GPS accuracy then one way to do that is with differential GPS which does not require additional GPS transmitters. I don't think that cellphone users really need submeter accuracy, but since they are connected to a 2 way network then it's possible that work could be done in this area.
When looking at high accuracy GPS developments (with 10's of thousands of correlators running) I have not seen any hard evidence that signal bounce is a problem for GPS. Whenever developers have a problem that they don't understand, then they are likely to brush it off as a multipath problem. If you can point me to any well documented papers which say otherwise then I would appreciate it.
GPS can work indoors, in cars, in elevators,...
on
GPS Meets PCS
·
· Score: 1
A number of threads here have made comments by people that GPS won't work indoors, in an urban environment, in a car,... The problem with such statements is that there is no theoretical basis for them, they are made based upon a person's experience with a particular off the shelf GPS unit. That's _not_ what will be ultimately included in the cellphones. (The first units off the line may have limited performance compared to what will become available in the next couple of years.)
There is nothing magic about getting GPS to work indoors. I hope that everybody realizes that even in an outdoor setting the GPS signal is buried beneath the noise. Please study the terms "massive parallel correlation" and "aiding" and understand how position can be solved for quickly even in a cold start situation in an indoor location.
Here are a couple of companies working on high sensitivity GPS solutions:
Here is a course outline for a high-sensitivity GPS class offered by Navtech:
http://www.navtechgps.com/seminars/sem218.asp
Indoor GPS, or more precisely, high-sensitivity GPS, is one of the frontiers of GPS development. Driving this development is the need to locate cell-phones and other wireless devices. For this reason, high-sensitivity GPS devices are coming to market in the form of chips that need to be imbedded in wireless devices by the device manufacturer.
This 1 day course includes:
-how the technology works, both theory and practice
-where to get high-sensitivity GPS chips
-how to quantify and assess performance of competing solutions
-how to go about implementing high-sensitivity GPS hardware, including implementation issues and solutions
-the role of the wireless carrier
-industry standards governing wireless location
8:30 - Motivation
Location Based Services and FCC E911 Mandate;
Latest status of E911 Mandate
Standard GPS Review
Why GPS seems difficult
GPS link-budget, power of received signals, dB Review
How GPS works with low signal strengths
GPS architecture review.
GPS signal: at the satellite, at the receiver, the PRN code
Standard GPS receiver.
Front end gain, Friis' formula, Front end worksheet, Baseband, Tracking
loop, Mixers, Baseband gain, Correlation, Receiver SNR worksheet
Why standard GPS doesn't work inside
9:45 - Acquisition and Aiding
Acquisition
Frequency and code delay search space, ambiguity function, acquisition
schemes, acquisition worksheet.
Navigation, role of ephemeris and HOW, re-acquisition at lower signal
strengths, the low signal strength conundrum,
Aiding
The fundamental idea of aiding, role of wireless aiding, history of wireless
aiding: 1981 through 1998.
11:00 - Indoor GPS Theory
Indoor receiver architecture, correlator size vs. integration time, freq/code search space for Assisted-GPS, Assisted-GPS acquisition scheme, coherent integration, I&Q channels and non-coherent integration, squaring loss, Hi-sensitivity SNR worksheet, correlator size vs. sensitivity, signal strengths in practice.
1:30 - Indoor GPS: Who, How, Implementation Issues
Who
Manufacturers of wireless-ready GPS.
How
Hardware and Software approaches; software-correlator and
hardware-correlator receiver architecture, processing timeline,
comparison of Standard & Hi-S GPS receivers.
RF Front ends; what to look for, candidate chips.
Implementation issues
Hardware issues; RAM, ROM, Flash, DSP, Interrupts, Power.
Timing issues; role of time tags, cellular network timing, solving for the
time tag
2:45 - Indoor GPS Performance
Achievable performance
PFA and PD, Achievable performance worksheet
Demonstrated performance
In offices, basements, urban canyons, parking garages & filing cabinets
Measuring and predicting performance
Calibrating/validating your SNR worksheet, with real signals, using a
simulator, effect of code side-lobes, implementation losses.
4:00 - Aiding Sources, Industry Standard, Summary
Aiding sources
Where aiding comes from, reference station, local area & worldwide
network approach, the role of the wireless carrier, broadcast vs. 1:1,
navigation solution in mobile and at server
Industry standards for Assisted-GPS
Common data, GSM, UMTS, CDMA, US-TDMA.
Indoor GPS Summary
The problem we faced and the solution: combination of aiding and
massive parallel correlation.
Indoor GPS reality checklist.
I have seen indoor GPS work
on
GPS Meets PCS
·
· Score: 1
GPS _can_ work indoors, in cars, in parking garages, in elevators...
First a question that might be of interest to a broad audience:
If your designs are truly asynchronous then their performance will noticibly change with variations in process. How does a supplier explain why units sold on a Tuesday work faster than items on a Wednesday? With synchronous logic we (with the exception of the overclockers) generally give up some performance but get consistent performance by using the same clock rate on all systems. I ask this question because Weitek once made a Sparc FPU which could operate faster than a competitor's by enabling a special mode, but Sun would not use that mode because they didn't want customers complaining that they got a "lemon" with one of the slower chips. (They required a second source.)
And to round it out how about some detail for the hardware guys in the audience:
What tools/languages do you use for design, simulation, synthesis, test generation, place and route, clock tree synthesis, timing analysis, boundary scan, power estimation,...? Do you use Unix? Source code control? Have you tried prototyping in the Xilinx Virtex FPGAs?
Have you gone away from the COT (customer own tools) approach? Do you use vendor supplied libraries? If not how do you validate your libraries?
Have any of your hardware designs go into full production? What yields did you achieve?
How easy is it for somebody to integrate your cores into their own ASIC? Can any Verilog RTL jock do it, or do you need experienced full custom chip designer expertise and a COT flow?
Why give the guy a hard time for doing a little research? If there were a "robust and free alternative to cvs" would you recommend that he ignore it?
Personally I use CVS for ASIC development and am pretty happy with it. We use tools on Solaris, Linux, and Windows 2000 in the course of developing and verifying ASICs and it's nice to have a tool that works well on all of the above. You should see the mess that a lot of hardware engineers create...
I knew a group of electrical engineering consultants that did this and it worked out really well for them too. I'm not sure but I think that they started the company in Ireland, and paid an accountant in Ireland to handle a lot of the paperwork. Sorry for the lack of detail, but apparently this is a pretty well known loophole.
Actually they did the same thing in America, and it lets them take on jobs with companies that will not hire individual consultants. So now they get contracts with said companies even though they *are* basically working as individual consultants. It's all a shell game...
Check out what Qualcomm (SnapTrack) and their competition are doing. There are a number of companies working on GPS which will get embedded in cell phones, two way pagers,... and it's designed to work indoors. Qualcomm spent $2B on SnapTrack so they obviously believe in the technology.
Slashdot Mirror
Didn't think so.
You might want to read "System Design Considerations When Using Cypress CMOS Circuits" at Cypress and bone up on your transmission line theory.
I'll bet that it's off by default. If you leave it on all of the time it will consume more power. Of course this assumes that they are using some form of assisted GPS to achieve a reasonable time to fix.
Does anybody know if this GPS works indoors? (Please don't tell me that it's impossible to get GPS to work indoors because I know for a fact that it's possible.)
These guys are trying to use HDTV transmitters as a sort of pseudolite:
http://www.rosum.com/
I think that their idea is to reuse the HDTV transmitters instead of having to install new equipment since it would be less expensive. They may run into other problems since there signal propagation delays could be somewhat unpredictable.
The whole idea of using GPS as a location technology is to reuse a proven technology and not require the installation of an alternate network, or upgrades to an existing network. The signals are strong enough given a sufficiently powerful receiver.
If you want increased GPS accuracy then one way to do that is with differential GPS which does not require additional GPS transmitters. I don't think that cellphone users really need submeter accuracy, but since they are connected to a 2 way network then it's possible that work could be done in this area.
When looking at high accuracy GPS developments (with 10's of thousands of correlators running) I have not seen any hard evidence that signal bounce is a problem for GPS. Whenever developers have a problem that they don't understand, then they are likely to brush it off as a multipath problem. If you can point me to any well documented papers which say otherwise then I would appreciate it.
A number of threads here have made comments by people that GPS won't work indoors, in an urban environment, in a car,... The problem with such statements is that there is no theoretical basis for them, they are made based upon a person's experience with a particular off the shelf GPS unit. That's _not_ what will be ultimately included in the cellphones. (The first units off the line may have limited performance compared to what will become available in the next couple of years.)
There is nothing magic about getting GPS to work indoors. I hope that everybody realizes that even in an outdoor setting the GPS signal is buried beneath the noise. Please study the terms "massive parallel correlation" and "aiding" and understand how position can be solved for quickly even in a cold start situation in an indoor location.
Here are a couple of companies working on high sensitivity GPS solutions:
http://www.snaptrack.com (Qualcomm)
http://www.globallocate.com
Here is a course outline for a high-sensitivity GPS class offered by Navtech:
http://www.navtechgps.com/seminars/sem218.asp
Indoor GPS, or more precisely, high-sensitivity GPS, is one of the frontiers of GPS development. Driving this development is the need to locate cell-phones and other wireless devices. For this reason, high-sensitivity GPS devices are coming to market in the form of chips that need to be imbedded in wireless devices by the device manufacturer.
This 1 day course includes:
-how the technology works, both theory and practice
-where to get high-sensitivity GPS chips
-how to quantify and assess performance of competing solutions
-how to go about implementing high-sensitivity GPS hardware, including implementation issues and solutions
-the role of the wireless carrier
-industry standards governing wireless location
8:30 - Motivation
Location Based Services and FCC E911 Mandate;
Latest status of E911 Mandate
Standard GPS Review
Why GPS seems difficult
GPS link-budget, power of received signals, dB Review
How GPS works with low signal strengths
GPS architecture review.
GPS signal: at the satellite, at the receiver, the PRN code
Standard GPS receiver.
Front end gain, Friis' formula, Front end worksheet, Baseband, Tracking
loop, Mixers, Baseband gain, Correlation, Receiver SNR worksheet
Why standard GPS doesn't work inside
9:45 - Acquisition and Aiding
Acquisition
Frequency and code delay search space, ambiguity function, acquisition
schemes, acquisition worksheet.
Navigation, role of ephemeris and HOW, re-acquisition at lower signal
strengths, the low signal strength conundrum,
Aiding
The fundamental idea of aiding, role of wireless aiding, history of wireless
aiding: 1981 through 1998.
11:00 - Indoor GPS Theory
Indoor receiver architecture, correlator size vs. integration time, freq/code search space for Assisted-GPS, Assisted-GPS acquisition scheme, coherent integration, I&Q channels and non-coherent integration, squaring loss, Hi-sensitivity SNR worksheet, correlator size vs. sensitivity, signal strengths in practice.
1:30 - Indoor GPS: Who, How, Implementation Issues
Who
Manufacturers of wireless-ready GPS.
How
Hardware and Software approaches; software-correlator and
hardware-correlator receiver architecture, processing timeline,
comparison of Standard & Hi-S GPS receivers.
RF Front ends; what to look for, candidate chips.
Implementation issues
Hardware issues; RAM, ROM, Flash, DSP, Interrupts, Power.
Timing issues; role of time tags, cellular network timing, solving for the
time tag
2:45 - Indoor GPS Performance
Achievable performance
PFA and PD, Achievable performance worksheet
Demonstrated performance
In offices, basements, urban canyons, parking garages & filing cabinets
Measuring and predicting performance
Calibrating/validating your SNR worksheet, with real signals, using a
simulator, effect of code side-lobes, implementation losses.
4:00 - Aiding Sources, Industry Standard, Summary
Aiding sources
Where aiding comes from, reference station, local area & worldwide
network approach, the role of the wireless carrier, broadcast vs. 1:1,
navigation solution in mobile and at server
Industry standards for Assisted-GPS
Common data, GSM, UMTS, CDMA, US-TDMA.
Indoor GPS Summary
The problem we faced and the solution: combination of aiding and
massive parallel correlation.
Indoor GPS reality checklist.
GPS _can_ work indoors, in cars, in parking garages, in elevators...
Please see the following links for more details.
http://www.navtechgps.com/seminars/sem218.asp
http://www.snaptrack.com/
http://www.globallocate.com/
First a question that might be of interest to a broad audience:
If your designs are truly asynchronous then their performance will noticibly change with variations in process. How does a supplier explain why units sold on a Tuesday work faster than items on a Wednesday? With synchronous logic we (with the exception of the overclockers) generally give up some performance but get consistent performance by using the same clock rate on all systems. I ask this question because Weitek once made a Sparc FPU which could operate faster than a competitor's by enabling a special mode, but Sun would not use that mode because they didn't want customers complaining that they got a "lemon" with one of the slower chips. (They required a second source.)
And to round it out how about some detail for the hardware guys in the audience:
What tools/languages do you use for design, simulation, synthesis, test generation, place and route, clock tree synthesis, timing analysis, boundary scan, power estimation,...? Do you use Unix? Source code control? Have you tried prototyping in the Xilinx Virtex FPGAs?
Have you gone away from the COT (customer own tools) approach? Do you use vendor supplied libraries? If not how do you validate your libraries?
Have any of your hardware designs go into full production? What yields did you achieve?
How easy is it for somebody to integrate your cores into their own ASIC? Can any Verilog RTL jock do it, or do you need experienced full custom chip designer expertise and a COT flow?
Personally I use CVS for ASIC development and am pretty happy with it. We use tools on Solaris, Linux, and Windows 2000 in the course of developing and verifying ASICs and it's nice to have a tool that works well on all of the above. You should see the mess that a lot of hardware engineers create...
Actually they did the same thing in America, and it lets them take on jobs with companies that will not hire individual consultants. So now they get contracts with said companies even though they *are* basically working as individual consultants. It's all a shell game...
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