state of layer23

Andreas.Eversberg Andreas.Eversberg at versatel.de
Mon Jun 7 07:49:58 UTC 2010


 
hi,

if you pull the git, you will notice that i submitted the lapdm code i
was working on. location update with app_mobile works now. (at least for
the combined BCCH+CCCH+SDCCH4) the best way to test the location update
is to setup a mobile test card to manual network selection, and to set
the registered PLMN to the tester's network. see VTY interface for more.

what happens:

- the previously store ba-list of frequencies is used to search for the
registered PLMN. since there is only one frequency on a tester, the
power measurement is done on this frequency only.
- the power measurement result is positive, so a sync request is made to
that channel.
- the sync is indicated by layer 1.
- the BCCH data is received. the cell is "suitable and allowable".
- a sync request is done again, because this cell is the one to "camp
on".
- a sync request is done again, because the mobility management process
makes a location update and requests a channel from the radio ressource.
- the sync is confirmed by layer 1.
- after syncing to the channel the layer 2 is activated by the BTS.
- the location updating request is sent and messages are exchanged until
the location update is complete.
- the layer 2 is de-activated by the BTS.
- the release of layer 2 is currently not processed by RR, so the timout
aborts the radio link. (but this is fixed soon)

but there are problem:

1. the layer 1 sometimes crashes when sending frames. i guess there is
no queue inside... i currently don't care about any confirm of a frame,
so i send all frames i need to send. i would like to get a confirm when
a frame is sent, so i can send the next frame without making layer 1
overflow. this confirm would also be handy for RACH requests when they
are sent. since there are only few message during a location update or a
call, i think this is not much overhead. when requesting sync/rach
again,
all pending frames (RACH request / transmit data) shall be removed
inside
layer 1.

2. when sending two sync requests to layer 1 without a delay, the layer
1 crashes. i expect to do a sync request at any time. also when sending
a sync request before i got a response, i do not know to which the
response belongs to which request. (delayed on the serial line) a
confirm of every sync request would be handy, so i can wait for this
confirm until i make another sync request to a different channel. this
confirm just tells me that the layer 1 has received the sync request and
is able to receive another sync request. also when syncing to a
different channel, i skip any sync result or received frames until i get
the confirm, so i can skip any data from the last channel i was synced
to.


andreas









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