Hi all.
I'm testing to see if inter-BSC handover will work between RBS and osmo-bts, given that support for handover from an E1 to RTP call is not yet supported.
Among all kinds of other things going on, I'm not finding it easy to understand how to configure everything for inter bsc handover.
I know there are two videos (at least) from Neels at OsmoDevCon, on the subject of handover and then inter-MSC handover.
I have one DUG/RUS configurarion with the e1d, bsc/msc/mgw/hlr running on the associated PC and one remote SysmoBTS, which is running osmo-bsc and it's associated MGW locally. All that is fine, I can call between the two BTSs successfully.
I'm guessing I should add the neighbours manually in each bsc but I'm not sure what to configure in the MSC.
Maybe I'll figure it out this evening, but I thought it best to also write most given the time zones and most of you guys will see this before I get back to work tomorrow.
Thanks!
k
On Thu, Jul 01, 2021 at 07:32:09PM -0500, Keith wrote:
I'm not finding it easy to understand how to configure everything for inter bsc handover.
Hm, it appears we are lacking documentation on inter-BSC and inter-MSC handover in the osmo-msc manual.
In each BSC, you add a mapping of ARFCN-BSIC to Cell Identifiers. (In osmo-bsc.cfg, remote-BSS neighbors have to be full Cell Id + ARFCN-BSIC.) I recommend to use CGI identifiers only.
In the MSC, you add a mapping of Cell Identifiers to Point-Codes.
In osmo-bsc.cfg:
# this is the ARFCN+BSIC of the remote-BSS cell, # and the LAC+CI of the remote-BSS cell. neighbor cgi 262 42 23 42 arfcn 123 bsic 4
In osmo-msc.cfg:
neighbor a cgi 262 42 23 42 ran-pc 0.24.1
serving BSC --Cell-Id--> MSC --Point-Code--> target BSC serving given cgi, at given PC
The BSC gets reports about a specific ARFCN and BSIC showing up strongly. It needs to translate that to a Cell Identifier. Only the Cell Identifier is sent to MSC in Handover Required. Then the MSC needs to know which of its BSCs serves that Cell Id. That's why you add to osmo-msc.cfg a mapping of cgi to point-code. Hence MSC will send the Handover Request to the BSC with that point-code matching the cgi.
And to support handover back to the first BSC, do the same thing vice versa. So in a scenario with two BSCs with one BTS each, each BSC has one entry for the other BSC's BTS, and the MSC has two entries, one for each BSC's BTS.
HTH ~N
On 02/07/2021 11:50, Neels Hofmeyr wrote:
Hm, it appears we are lacking documentation on inter-BSC and inter-MSC handover in the osmo-msc manual.
[...] HTH ~N
Many thanks for that explanation, Neels!
I've applied that configuration and I'm testing it out now, although not having so much success as yet. I am not seeing the neighbours in the vty log.
One weird thing, which I will try to diagnose further, is some really strange meas reports on the meas-feed from osmo-bsc running the the bts. i get reports with 100 or more neighbours. and the RX levels are not what the vty log says Could that be something to do with the arm arch?
On Fri, Jul 02, 2021 at 03:21:28PM -0500, Keith wrote:
One weird thing, which I will try to diagnose further, is some really strange meas reports on the meas-feed from osmo-bsc running the the bts. i get reports with 100 or more neighbours. and the RX levels are not what the vty log says Could that be something to do with the arm arch?
meas_feed doesn't use portable data structures, AFAIR. You ahve to run both sender and recipient on the same architecture / ABI.
On 05/07/2021 05:47, Neels Hofmeyr wrote:
Feel free to paste config files... bsc and msc
~N
Thanks Neels, I will test it again first.. I swap the lacs to force LURs on each MSC restart and I think that might have got in the way in this case... Off site now, but I will set up two BSC/BTS locally and check it again.
Posting here again really to ask, should one also use:
neighbor-list mode manual neighbor-list add arfcn 246
or just the :
neighbor cgi 334 07 274 102 arfcn 246 bsic 62
On Mon, Jul 05, 2021 at 06:32:27PM -0500, Keith wrote:
Posting here again really to ask, should one also use:
neighbor-list mode manual neighbor-list add arfcn 246
Those are legacy config items, or may be used in special cases. You should normally omit all neighbor-list commands completely and only configure neighbors as:
# remote-BSS always of the form: neighbor cgi 334 07 274 102 arfcn 246 bsic 62
# local-BSS may come in different sizes: neighbor bts 23 neighbor cgi 334 07 274 102 neighbor cgi 334 07 274 102 arfcn 246 bsic 62
Note that it has to go both ways:
bts 23 neighbor bts 42 bts 42 neighbor bts 23
meaning it is not implicitly reciprocal, each cell's neighbor config starts with a clean slate, no matter what the other cells configured.
-
Harald Welte -
Keith -
Neels Hofmeyr