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Re: How RRLP 'MS assisted GPS' really works
by Dieter Spaar 13 Dec '10

13 Dec '10

Hello Christian, Thank you very much for the links. On Sun, 12 Dec 2010 19:22:41 +0100, "Christian Vogel" <vogelchr(a)vogel.cx> wrote: > > There are a few. My Trimble Thunderbolt can give you doppler and > codephase (gps often calls it "pseudorange"). Thats interesting, the ublox 5 GPS module I was playing with only provides those data if you have the so called "raw data premium feature" enabled (whatever this means, I have not yet looked at the details). > Sparkfun sells "only the frontend" (mixer, 1-bit ADC, USB) > with sourcecode available in a book and on DVD (WTF?!) > > ---> http://www.sparkfun.com/products/8238 Interesting device, I wasn't aware of it (I know about the book). Is the Source Code of the book available ? So far I have only seen some material for download at the following site, not sure if there is the whole content of the DVD: http://kom.aau.dk/project/softgps/ Would be interesting to use the code with a USRP. > There's actually quite a lot of information out there, > but there also seem to be quite a lot of half-abandoned > projects (and a few seem to have vanished since the last time I had > an interest in it around 2005). I had a short look at some but always had the impression that it is not exactly what I am looking for. I guess I should try to get a GPS receiver which provides the required data, thats probably the easiest approach. Best regards, Dieter -- Dieter Spaar, Germany spaar(a)mirider.augusta.de

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Re: How RRLP 'MS assisted GPS' really works
by Dieter Spaar 12 Dec '10

12 Dec '10

Hello Harald, On Sun, 12 Dec 2010 17:01:22 +0100, "Harald Welte" <laforge(a)gnumonks.org> wrote: > > Pretty interesting. If only I had the time to implement it ;) I don't think that implementing is the hard part, debugging is. You send data which might be wrong due to some bugs in your code into a "black-box" which does something with the data. The "black-box" will not tell you if your data are wrong, if they are, it might just take longer till any results are returned. So you are not sure if you are doing the things right. I conclude the above from my experience so far: Even phones with very extensive tracing capabilities don't tell you much about what is going on during their GPS position calculations. And at least I am not aware of a GPS server I have access to who will provide those data required for an "MS-assisted" measurement so that one could compare the own calculation against a reference. If someone know about a server providing those data (I am not talking of things like "almanac" or "ephemeris" here) or knows about existing source code to do the calculation, I would like to know. BTW, the book "Server-Side GPS and Assisted-GPS in Java" contains a few nice chapters, one should not care about "Java" in the title, only the examples are written in Java. Best regards, Dieter -- Dieter Spaar, Germany spaar(a)mirider.augusta.de

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How RRLP 'MS assisted GPS' really works
by Harald Welte 12 Dec '10

12 Dec '10

Hi all, I believe I have finally figured out how this 'MS assisted' RRLP mode works. Not sure if I am the first or the last one to understand it, just wanted to share what I know: Just to recap, RRLP has three modes: * E-OTD of different BTS signals (AFAIK not used) * MS-based GPS positioning (optionally with assistance data from the GSM net) * MS-assisted GPS positioning (what I'm talking about now) On Wed, Dec 08, 2010 at 08:53:48AM +0000, Dieter Spaar wrote: > This is from the RRLP specification, those are some of the data for > assisted measurements (those "low-level" data I refered to): > > Data sent to the phone (for every satellite) > > Doppler > Doppler uncertainty > Code phase > Int code phase > GPS bit number > Code phase search window > Azimuth > Elevation Basically this tells the phone: * which doppler shift to expect (result from movement speed of satellite), typically in the range of +/- 5kHz of the GPS L1 frequency * the 'code phase', i.e. the difference between a certain GSM bit (in a specified timeslot/frame number/bcch carrier) and a specified GPS bit (TOW, bit, chip, ...) * which azimuth/elevation to expect (not sure how the phone should use this, unless it knows the orientation of the antenna and has a MIMO receiver) what happens now is that the MS will lock onto one specific satellite. It can do this quickly, as it altready knows * a certain doppler frequency shift (range) in which it should apply a known scrambling code sequence (the satellite number corresponds to a given pseudo-random sequence), and the * expected 'code phase', i.e. the difference between the time at which a certain bit is transmitted on the BCCH carrier of a GSM cell, and which chip of the given satellite will be expected to be received within the GSM cell. Once it acquires the signal, it will measure the number of whole (and fractional) GPS chips that it has observed between * the start of a given GSM frame number (called 'reference frame') and the * wrap of the GPS 1023bit pseudo-random sequence This is then sent back to the network: > Data sent back from the phone (for every satellite) > > Carrier Noise Ratio > Doppler this is the actually measured doppler shift for this satellite in the MS receiver > Whole Chips (0..1022) > Fractional Chips (0..1023) and this is the number of GPS chips between the wrap of the GSM reference frame number and the wrap of the GPS 1023 bit chip sequence. The specification states "The resolution of the fractional portion is approximately 0.3m" So all the phone actually ever does is measurement of timing difference. It will never try to decode the actual GPS signal at all. The network (SMLC) can then compute the GPS position, as it can get the timing information for all the satellites the phone has received, and it already knows all the other data (almanac/ephemeris/...) from a local database and/or its own reference receiver. Pretty interesting. If only I had the time to implement it ;) -- - Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)

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wiring scheme required
by Thomas Ansorg 12 Dec '10

12 Dec '10

hello i still don't know how 2 bs11 in multi-drop config are connected correctly. nothing's to find on openbsc.com. someone may send a schematic to me, please. T. -- Wer Rechtschreibfehler findet, darf sie behalten!

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tei and oml ts assignment
by Thomas Ansorg 12 Dec '10

12 Dec '10

hello how do i set the tei and timeslot for a bs11? of course i know bs11_config and the tei_oml parameter, but it don't seem to work. i tried ./bs11_config tei_oml 4 30 and 30 4 (to set the timeslot to 4 and tei to 30). but when i query the bs11, it still says timeslot=1 and tei=25. I tried it with and without disconnection of the bs11. how do i call bs11_config correct for that purpose? T. -- Wer Rechtschreibfehler findet, darf sie behalten!

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[ADM] Please try to avoid merges in the git tree
by Harald Welte 11 Dec '10

11 Dec '10

Hi all, this is just a general request to everyone with git commit access on the OpenBSC / Osmocom repositories. I would appreciate to restrict the use of 'git merge' to the absolute minimum neccessarry, as it makes the commitlog and timeline much harder to understand. If you're working on some private branch on a particular feature, please rebase that private branch on current master before pushing the changes. Thanks! -- - Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)

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Bounce action notification
by mailman＠lists.gnumonks.org 11 Dec '10

11 Dec '10

This is a Mailman mailing list bounce action notice: List: OpenBSC Member: Barrie.Mcclarity(a)zeusmail.org Action: Subscription disabled. Reason: Excessive or fatal bounces. The triggering bounce notice is attached below. Questions? Contact the Mailman site administrator at mailman(a)lists.gnumonks.org.

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AW: Plans for GSM / OpenBSC field test at 27C3
by Andreas.Eversberg 10 Dec '10

10 Dec '10

> Andreas: Do you have some SuperSIM to test the new pySIM patch mode and > integrate it with OpenBSC? If not, I will send you some sample cards monday > next week. please send me some cards. i have not followed the pySIM talk in the mailing list. what reader do i need?

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Successfully Implemented SMS capable MSC & VLR
by tejas oza 10 Dec '10

10 Dec '10

Hi Holger, If you remember we are the students from Uppsala University Sweden. I am glad to inform you that we have done with our project. We have successfully implemented SMS capable MSC and VLR in Erlang, integrated with Mobile Arts SMSC, HLR and OpenBSC. We are also planning to make our project Open source and will inform you as soon as we will finalize it. -- *Thanks & Regards Tejas Oza Masters in Computer Science, Department of Information Technology, Uppsala University, Sweden.*

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Control Interface
by Harald Welte 10 Dec '10

10 Dec '10

Hi Daniel, i am occasionally browsing the commitlog of the daniel/controlif branch and am wondering what exactly is happening there. It seems much more to me that 'controlif' is about reimplementing a lot of the functionality that already exists in the VTY, which I think is bad. My original understanding of the idea of SNMP support was: 1) we mostly want to export counters that we already have, but in a consistent/machine-parseable way. This is read-only 2) we may want to have traps 3) we have some (few!) things like rf_lock which should be issued (written) by the external SNMP process. Has the focus changed since this last discussion? Can anyone explain why that is? Even if we suddenly have a need for a lot of write/modify type settings from the SNMP side, we should not have two ways how to modify a single parameter inside OpenBSC. In that case we may need some code that can sort-of automatically 'export' all controlif parameter to the VTY, and remove the current code that sets this parameter from the VTY. Any ideas? Regards, Harald -- - Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)

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