This is the begin of a long march of turning tbf into a C++ class
and properly hiding the secrets inside this implementation instead
of having it spread across various different files.
Do not claim that the payload is not known. Add the missing break.
Do not print:
<0002> gprs_rlcmac.cpp:1174 GPRS_RLCMAC_CONTROL_BLOCK_OPT block payload is not supported.
<0002> gprs_rlcmac.cpp:1176 Unknown RLCMAC block payload.
For mocking/unit-testing/emulation (and a dual trx-systems) having
global state is quite bad. Cut back on the usage of the global
struct gprs_rlcmac_bts. It also makes the complexity of certain
routines more clear.
The timing advance of any TBF is stored when it ends. Whenever a new TBF
with the same TLLI is created (downlink TBF), the stored TA is recalled.
This algorithm assumes that the mobile does not move too fast during
transfer. Also the mobile must start a connection in order to get correct
initial timing advance.
This algorithm does not implement the timing advance procedure as defined
in TS 04.60. To implement the standard timing advance procedure, the BTS
must decode RACH on certain bursts, the mobile is expected to send them.
This requires much more complexity to a transceiver like USRP/UmTRX or
Calypso BTS.
The algorithm was tested at TA >= 8 and works quite well.
The measurements include:
- DL bandwidth usage
- DL packet loss rate
- DL measurements by mobile
- UL measurements by BTS
In order to receive DL measurements from mobile, it must be enabled via
system information message at BSC.
This simpliefies the allocation process.
tfi_alloc is responsible to allocate a TFI, not a time slot.
The first time slot available depends on multislot class and on other
ongoing TBF (concurrent TBFs), so it is part of the allocation
algorithm to select it.
The slots are choosen in a way that later selection of slots for
concurrent TBFs will have the same downlink/uplink control channel
(PACCH).
This is required for polling acknowledge of new TBF assignment on PACCH.
The MS will always have the same PACCH uplink slot while beeing in packet
transfer mode.
Original code: c7e7f6868b
(The code was committed earlier, but got lost somehow.)
I added IMSI, so the paging request is sent in correct paging group.
Also I excluded rest octets from pseudo length.
It is tested and it work.
Some MS will leave packet transfer mode, if TAI is given, but no timing
advance control messages are sent on PTCCH. This could results in
permanent loss of larger packets.
It is quite essential. It shows how TBFs are related and helps to estimate
states and timers (timeouts) of the MS.
In order to use it, it must be defined by a switch at gprs_rlcmac.h.
Be sure to use always two bytes of length information for DL-UNITDATA,
even if the length of LLC data is less than 128 bytes. This way the data
has always the same offset from a 32 bit boundary.
This is required, since we may change slot allocation. In case of a
change, we do not want to be unable to change, if the same TFI on one of
the other slots is already in use by a different TBF (having same TFI, but
on different slot).
It is mandatory to support it because MS may request a single block.
In this case the network must assign a single block.
It is possible to force single block allocation for all uplink requests
on RACH. (VTY option)
In order to send control blocks to MS and receive control blocks from MS
(polling), it is required to select one timeslot that the MS must be
able to send and receive. The allocation algorithm must take care of
selecting that slot.
The new data structure is required to define slot/TFI assigment for MS
with multislot capability.
Now there are two lists for TBFs: uplink and downlink. It is possible to
have different TBFs with same TFI in the same direction, as long as they
are assigned on different timeslots.
See tbf.txt for description.
Note: This does not implement any multislot support. It defines the new
data structure. Currently only the first slot is assigned.
Merge is based on jolly_new branch with two modifications.
1. Modified PCU L1 interface.
pcu_l1_if.cpp - common functions for tx and rx messages on L1 interface.
sysmo_sock.cpp - SYSMO-PCU socket functions.
openbts_sock.cpp - OpenBTS-PCU socket functions.
pcuif_proto.h - L1 interface's primitives.
2. Modified encoding of RLC/MAC Control messages, now we use structures and encode_gsm_rlcmac_downlink() function for encode control blocks (without hand-coding).
Only when using LOGL_DEBUG, every detailled information is displayed.
When using LOGL_INFO, a summary of the process is displayed.
When using LOGL_NOTICE, only errors and warnings like timeouts
or invalid received informations are displayed.
When using LOGL_ERROR, only local error like software errorss are
displayed.
The pseudo length may not include the rest-octets, so it stays compatible
to non-GPRS phones.
At pcu_l1_if.c (OpenBTS) no pseudo length is given, so the frame is
only 22 bytes long. I could not test if it works.
The hack for resetting BSSGP instance is removed and now performed
whenever the NS state changes to UNBLOCKED.
The BSSGP instance is now created only once, as it should be.
Received STATUS messages are ignored as they should be.
The creation and destruction of BSSGP/NS instances is now handled by
layer 1 interface alone.
Added functions:
- gprs_bssgp_pcu_rx_paging_ps() for handling paging message from BSSGP;
- write_paging_request() for writing paging request message;
- gprs_rlcmac_paging_request() and pcu_l1if_tx_pch() for sending paging request message to BTS.
Holger Hans Peter Freyther