Hello friends, I want to modify the SYSTEM INFORMATION data, but I have some difficulties to understand the GSM spec. It's about the GSM 04.08 part 10.5.2.34, I don't know how to interpet table 10.5.72 (and other similar tables). According to paragraph 9.1.35 table 9.32 (GSM 04.08) SI3 rest octetets has a length of 4 bytes, but according to par. 10.5.2.34 we're dealing with a type 5 IE and thus with length of 5 bytes. That's odd to me, but hey, the world is full of surprises :) Anyway, the problem is I don't know how to interpret table 10.5.72 (of GSM 04.08). I mean, for example, element CBQ (Cell Bar Qualify) is at bit 1. Bit 1 of what, which octet? What is L | H? Can someone explain it to me, so I can experiment with SI messages? Thank you!
Well guys, If someone can help me with how to fill in the Rest Octets, I'll send you a postcard from my city to thank you :) What I found out is that it uses CSN.1 notation, but the description is hard to follow, I began to see words floating around the screen. <SI3RestOctet>::=<Optionalselectionparameters> <OptionalPoweroffset> <SystemInformation2terIndicator> <EarlyClassmarkSendingControl> <Schedulingifandwhere> {L|H<GPRSIndicator>} <sparepadding>: <OptionalSelectionParameters>::= L |H <SelectionParameters>; <SelectionParameters>::= <CBQ:bit(1)> <CELL_RESELECT_OFFSET:bit(6)> <TEMPORARY_OFFSET:bit(3)> <PENALTY_TIME:bit(5)>; <OptionalPowerOffset>::= L |H <PowerOffset:bit(2)>;<SystemInformation2terIndicator>::= L|H; <EarlyClassmarkSendingControl>::= L|H; <Schedulingifandwhere>::= L|H <WHERE:bit(3)>; <GPRSIndicator>::= <RACOLOUR :bit(3)> < SI13POSITION :bit>; So, now I want to enable GPRS support by do something with GPRSIndicator. This is how I thought to do that: L|H -> 1 next -> RACOLOUR -> 000 next -> SI13POSITION -> 0 So we get -> 1 000 0 Next step is to do something with padding but than I'm lost. I don't have good documentations on how to use CSN.1 for GSM network.
Nordin - You will probably find GSM 04.07 Appendix B of some use here. Specifically, for a description of the padding sequence and the meaning of "H" and "L" see GSM 04.07 B.1.2.2. -- David On Jun 18, 2009, at 9:12 AM, Nordin wrote:
Well guys,
If someone can help me with how to fill in the Rest Octets, I'll send you a postcard from my city to thank you :) What I found out is that it uses CSN.1 notation, but the description is hard to follow, I began to see words floating around the screen.
<SI3RestOctet>::=<Optionalselectionparameters> <OptionalPoweroffset> <SystemInformation2terIndicator> <EarlyClassmarkSendingControl> <Schedulingifandwhere> {L|H<GPRSIndicator>} <sparepadding>:
<OptionalSelectionParameters>::= L |H <SelectionParameters>;
<SelectionParameters>::= <CBQ:bit(1)> <CELL_RESELECT_OFFSET:bit(6)> <TEMPORARY_OFFSET:bit(3)> <PENALTY_TIME:bit(5)>;
<OptionalPowerOffset>::= L |H <PowerOffset:bit(2)
;<SystemInformation2terIndicator>::= L|H;
<EarlyClassmarkSendingControl>::= L|H;
<Schedulingifandwhere>::= L|H <WHERE:bit(3)>;
<GPRSIndicator>::= <RACOLOUR :bit(3)> < SI13POSITION :bit>;
So, now I want to enable GPRS support by do something with GPRSIndicator. This is how I thought to do that: L|H -> 1 next -> RACOLOUR -> 000 next -> SI13POSITION -> 0 So we get -> 1 000 0
Next step is to do something with padding but than I'm lost. I don't have good documentations on how to use CSN.1 for GSM network.
David A. Burgess Kestrel Signal Processing, Inc.
On Thu, Jun 18, 2009 at 06:12:38PM +0200, Nordin wrote:
Well guys,
If someone can help me with how to fill in the Rest Octets, I'll send you a postcard from my city to thank you :)
What I personally imagine might help is to look at the BSSMAP dissector in wireshark. It typically contains quite easily readable C-code for the actual packet parsing. -- - Harald Welte <laforge@gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)
What I personally imagine might help is to look at the BSSMAP dissector in wireshark. It typically contains quite easily readable C-code for the actual packet parsing.
Ok, I'll look at it this weekend. I haven't used wireshark a lot, but this is the right time to learn to work with it. Also to analyze your trace you post me about listening to neigbourcells with nanobts.
participants (4)
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David A. Burgess -
Harald Welte -
Nordin -
Nordin Bouchtaoui