We will need this for the actual handover algorithm implementation, as we will
only know the current BTS and the BCCH ARFCN of the strongest cell in the
measurement reports. Using this new function, we can resolve the matching
gsm_bts.
Since we are keeping a bitvec of the neighbor cells, we can now use
bitvec_get_nth_set_bit() to determine the ARFCN for each reported
cell in the 04.08 MEASUREMENT REPORT.
We use a 1024-bit-sized bitvec to generate the BA and neighbor frequency list.
This bitvec is still generated from the list of all BTS's inside the BSC, but
this patch is the first step to generalize this, i.e. generate arbitrary
neighbor lists.
* introduce a new bitvec_get_bit_pos() function to determine the bit value
at a given position inside a bit vector
* make sure bitvec_{get,set}_bit_pos() share code as possible
In some cases, we can try to close the lchan a bit faster than our
lchan release timeout:
* After we've sent LOC UPD ACCEPT and MM INFO
* After a phone has confirmed the RELEASE of a call
The rationale is as following:
If we have NECI=1, then the phone will request a channel with CHREQ
"0100xxxx Originating speech call from dual-rate mobile station when TCH/H is
sufficient and supported by the MS for speech calls", then we will try to
allocate a TCH/H [as it is sufficient].
However, if there are no free TCH/H slots on the BTS, we abandon and can't
handle the MO call at all :(
We might read or write on the OML link when the BTS is
reset and will get SIGPIPE interrupt and be gone... Just
ignore the SIGPIPE we will get the "exception" on the next
run of bsc_select and kill the (old) OML link.
With ip.access, in case of TCH/H, we have one RTP stream for each half-slot
(lchan), not just one per on-air timeslot. This is quite different from
a classic BTS where the TRAU frames of the two TCH/H channels would be
part of the same 16k sub-slot in a E1 timeslot.
Before this commit, OpenBSC used templates for the SYSTEM INFO
1, 2, 3, 4, 5 and 6 messages. Those templates were patched in
various places to reflect the network config like ARFCN.
Now, we actually generate those SI messages ourselves, using
values from the configuration file, and even calculating neighbor
cell lists.
All bts'es that you have configured in OpenBSC will end up in
the neighbor cell list - which should be more than sufficient for
the current small-single-site networks.
Code to implement handover control logic. A yet-to-be-implemented
handover algorithm will call bsc_handover_start(old_lchan, new_bts)
to start the handover process.
This introduces the signals S_LCHAN_ACTIVATE_{ACK,NACK} and
S_LCAN_HANDOVER_{FAIL,COMPL,DETECT} as well as code that actually issues
those signals. The signals are relevant for a yet-to-be-written handover
control logic.
Harald Welte
Harald Welte