The current implementation always starts the downlink slot allocation
with the first possible slot, depending on which channels are enabled
and which multislot class is offered by the MS. So in configurations
with many (>4) PDCH, some PDCH are not really used.
The new implementation introduced by this commit differs as follows:
- The reservation mechanism provided by GprsMs is used to avoid
incompatibilities is used in the same way like algo A does. This
basically means, that the allocation is done once when the first
TBF is requested and then used until all TBF have been released.
- All combinations of Rx and Tx slots are checked for compatibility
with the multiscot class. Basically the combination with the most
usable PDCH and the least number of reservations is used.
- Only one UL slots is provided.
- Tta and Tra are checked.
Sponsored-by: On-Waves ehf
Currently algorithm A bases its time slots selection on the number of
TBF actively using the PDCHs. This statistically prefers the first
time slots, especially with short living TBFs. So when the first TBF
is triggered by an uplink transfer (which generally results in a
short-lived TBF) the potentially longer living DL TBF will be bound
to the same slot. When another MS then requests an uplink TBF, it
will get the same slot (no UL TBF currently active).
This commit changes the algorithm to base its selection on reserved
slots instead.
Sponsored-by: On-Waves ehf
According to TS 45.002, 6.4.2 the training sequence (TSC) must be the
same for all slots in a multi-slot set.
This commit updates find_possible_pdchs() to only consider slots with
the same TSC if more that 1 slot shall be assigned.
Note that the first PDCH's TSC will be used as reference, so if two
or more groups with a common TSC are configured, only the first will
be used. This restriction does not apply to algorithm A, since it
will not assign more than one slot and therefore sets the max_slots
parameter to 1.
Sponsored-by: On-Waves ehf
Currently only the first enabled PDCH will be used. Beside the
throughput this will also limit the number of TBFs:
- number of UL TBFs <= 7
- number of DL TBFs <= 32
This commit changes the allocation algorithm to use the PDCH with the
least number of attached TBFs. This will improve the troughput in
both directions and the UL limits:
- number of UL TBFs <= min(32, N_PDCH * 7) UL TBFs
Ticket: #1794
Sponsored-by: On-Waves ehf
Currently the PDCH object do not know anything about the TBFs using
them. To make the slot allocation load dependant, at least some
numbers are required.
This commit adds TBF counters (one per direction) and the related methods
attach_tbf, detach_tbf, and num_tbfs to gprs_rlcmac_pdch.
Sponsored-by: On-Waves ehf
Currently the old TBF (either uplink or downlink) is passed around at
TBF allocation mainly to get information about the MS. To implement
more complex allocation algorithms, the MS object itself will be
needed anyway.
This commit replaces the old_tbf arguments by MS object arguments.
Sponsored-by: On-Waves ehf
The ms_class value is a property of the MS and thus belongs to the
GprsMs class. Nevertheless the MS object is created after the TLLI
gets known, so the value still has to be stored in the TBF initially.
This commit add the ms_class value to the GprsMs class and introduces
TBF accessor functions which either access that object or, if that is
not available, the value stored locally.
Ticket: #1674
Sponsored-by: On-Waves ehf
There is no need for the union/struct anymore. Make the variable members
of the UL/DL class.
As a result gprs_rlc_dl_window gets a reset() method because
memset(&dir.dl, 0, sizeof(dir.dl)) doesn't work anymore in reuse_tbf().
Ticket: SYS#389
Sponsored by: On-Waves ehf
Use UL/DL TBFs instead of the base class wherever it is clear that the
code only deals with one kind of TBF.
Ticket: SYS#389
Sponsored by: On-Waves ehf
The current code keeps a reference to all tbfs in the bts and another
reference in the pdch. This allows for the possibility of both lists to
go out of sync.
This patch removes the pdch-specific list of ul and dl tbfs and uses the
lists in the bts to lookup tbfs everywhere.
Performance for going through the global list is not an issue yet. We
can optimize this later and in a better way.
Sponsored-by: On-Waves ehf
The current code would only ever assign one PDCH for the initial
assignment (from CCCH). Only if reuse_tbf is called the algorithm would
actually use multiple DL PDCHs if possible.
This patch introduced a tbf attribute upgrade_to_multislot that is set
if we have multiple PDCH configured, and support multislot assignment,
but can only assign a single PDCH (alloc_algorithm_b, parameter single
is set). In this case after the assignment completes (and the MS is
listening on a PDCH) we resend a DL assignment though the PACCH and this
time we can assign multiple timeslots.
Counter j must be wrapped to prevent beeing negative, when it is
initialized. This wrapping happens, if TS 0 is used for PDCH in
combination with regular GPRS phones (MS class 12 or similar).
After reduce_rx_window() and update_rx_win_max() was called, one or more TS
might be removed. tx_win_min and tx_win_max must be adjusted to the new range
of allocated slots.
The algorithm does not support more than 5 TS on downlink for type 1 MS.
Supporting more than 5 TS would require adding more complexity to this
algorithm. MS that support more than 4 (or 5) TS on downlink are rare,
if they really exist.
Create a select_ul_slots which is very (95%) similar to the
select_dl_slots handling. This needs to be refactored and the
todo for multiple uplink slots should be handled too.
Add a warning about a potential failure on a busy PCU.
The naming of RX/TX still looks fishy and it should use DL/UL instead.
Work on pointers right now. We could introduce a struct with the window
min and max and pass this struct. The usage of 'D' appears wrong in the
ul_usage..
All logging code that used tbf->tfi is now using tbf_name to
print the the TBF. External code is now using tfi() which is
inlined and should result in the same code being generated as
before (+debug code that can be stripped).
The list belongs to the BTS. This makes cleaning this up more easy
and establishes a hierachy of resources that start from the BTS. The
debug_diagram code is now broken.
When a PDCH is disabled all resources should be freed. This is
currently not possible as the PDCH does not know where it belongs
to. On top of that the list (and other resources) should be
properly initialized on construction so that disable() is idempotent
and does not check if it was disabled. During the re-factoring I
noticed that during a sysmobts re-start some resources are not
freed. I left a warning in the code to resolve this issue later.
There was no difference but there is no point in poking in the
internals of the tbf, pdch and trx from various places. Information
hiding has a real purpose, e.g. compare with reading "the mythical
man month".
Jacob Erlbeck
Daniel Willmann