tree c0c09f5b4e2a77ee5033cefb8526038a69e61a73
parent fad4bbc517ef2a55988f0fd7874d98dbc5303b14
author Philipp Maier <pmaier@sysmocom.de> 1548152946 +0100
committer Philipp Maier <pmaier@sysmocom.de> 1550740657 +0100

assignment_fsm: fix channel allocator preferences

When the MSC allocates a channel through the ASSIGNMENT REQUEST, it may
ask for a TCH/H and a TCH/F at the same time and tell which of the two
types it prefers.

The process of channel allocation currently selects, based on the BTS,
MSC and MS capabilites exactly one apropriate codec/rate (e.g. TCH/H)
and then tries to allocate it. If that allocation fails, there is no way
to try the second choice and the assignment fails.

For example: The MSC asks for TCH/F and TCH/H, prefering TCH/F, then the
channel allocator will try TCH/F and if it fails (all TCH/F are
currently in use), then TCH/H is never tried.

Since the BSC currently only trys the first best codec/rate that is
supported it also ignores the preference.

Lets fix those problems by including the preference information and both
possible codec/rate settings into the channel allocation decision.

Change-Id: I5239e05c1cfbcb8af28f43373a58fa6c2d216c51
Related: OS#3503