Similar to what we do in osmo-bts-trx, group everything related to
an Uplink burst into a structure. Pass a pointer to this structure
to the logical channel handlers. This makes the code easier to read,
and facilitates sending NOPE indications to the transceiver
(will be introduced in the upcoming patch).
Get rid of sched_trx_handle_tx_burst(), and instead just call
sched_trx_a5_burst_enc() directly from sched_frame_clck_cb().
Change-Id: Id45b27180c233fdc42ae1ef0b195554dd299a056
Related: SYS#5313, OS#1569
It may happen that one or more Downlink bursts are lost on their
way to the MS due to a variety of reasons. Modern transceivers
supporting TRXDv1 protocol would substitute lost bursts with
so-called NOPE indications. Hovewer, neither fake_trx.py nor
grgsm_trx do support this feature at the moment.
We can still detect and compensate TDMA frame loss per logical
channels in the same way as it's already done in osmo-bts-trx.
In short, we should keep TDMA frame number of the last received
burst in the logical channel state, and using the appropriate
multiframe layout, check if there were any gaps between TDMA
frame number of the current burst and the stored one.
Change-Id: I3551d79796a3730565c2c70577e9d134e636f275
Using TDMA frame number of a burst with bid=0 is fine for xCCH,
but not for TCH and FACCH, because they use the block-diagonel
interleaving. A single block on TCH may be interleaved over
8, 4 or even 6 consecutive bursts depending on its type.
Since we now have the measurement history, we can attach TDMA
frame number to each measurement set, and then look up N-th
one when averaging the measurements in sched_trx_meas_avg().
Change-Id: I9221957297a6154edc1767a0e3753f5ee383173f
So far we used to store the sums of ToA and RSSI measurements in the
logical channel state, and after decoding of a block, we did calculate
the average. This approach works fine for xCCH and PDTCH, but when it
comes to block-diagonal interleaving (which is used on TCH/F and TCH/H
channels), the results are incorrect. The problem is that a burst on
TCH may carry 57 bits of one encoded frame and 57 bits of another.
Instead of calculating the sum of measurements on the fly, let's push
them into a circular buffer (the measurement history), and keep them
there even after decoding of a block. This would allow us to calculate
the average of N last measurements depending on the interleaving type.
A single circular buffer can hold up to 8 unique measurements, so the
recent measurements would basically override the oldest ones.
Change-Id: I211ee3314f0a284112a4deddc0e93028f4a27cef
Due to recent include dependency tree change in libosmocore, trxcon
fails now to build since it uncovered it's missing a header inclusion
for a symbol it is using:
osmocom-bb/src/host/trxcon/sched_trx.h:204:20: error: ‘GSM_MACBLOCK_LEN’ undeclared here (not in a function)
204 | uint8_t mr_cache[GSM_MACBLOCK_LEN];
| ^~~~~~~~~~~~~~~~
Change-Id: Ide22e525c106342b00171a8c08bb7265d19a651b
This feature may be useful for our TTCN-3 testing infrastructure.
By default it's disabled, and can be enabled using command line
arguments of the main binary:
./trxcon -g 127.0.0.1 ...
Change-Id: Iab4128fee5f18d816830fdca6c5ebebaf7451902
According to 3GPP TS 45.010, section 5.6.2, for packet-switched
channels the BTS shall monitor the delay of the Access Bursts
sent by the MS on PTCCH and respond with timing advance values
for all MS performing the procedure on that PDCH.
According to 3GPP TS 45.002, section 3.3.4.2, PTCCH (Packet Timing
advance control channel) is a packet dedicated channel, that is
used for continuous Timing Advance control (mentioned above).
There are two sub-types of that logical channel:
- PTCCH/U (Uplink): used to transmit random Access Bursts
to allow estimation of the Timing Advance for one MS in
packet transfer mode.
- PTCCH/D (Downlink): used by the network to transmit
Timing Advance updates for several MS.
As per 3GPP TS 45.003, section 5.2, the coding scheme used for
PTCCH/U is the same as for PRACH as specified in subclause 5.3,
while the coding scheme used for PTCCH/D is the same as for
CS-1 as specified in subclause 5.1.1.
The way we used to handle both PTCCH/U and PTCCH/D is absolutely
wrong - it has nothing to do with xCCH coding. Instead, we need
to use rx_pdtch_fn() for Downlink and tx_rach_fn() for Uplink.
Also, since we only have a shared RSL channel number for PDCH
(Osmocom-specific RSL_CHAN_OSMO_PDCH), there should be a way
to distinguish both PDTCH and PTCCH logical channels. Let's
introduce TRX_CH_LID_PTCCH for that.
Change-Id: I2d1e9b8a66f027047f8d7bdc3f82ff9d8ebcc25e
Both PRIM_IS_RACH() and PRIM_IS_EXT_RACH() macros to be used for
handover RACH detection in the follow up changes, thus we need
have them widely available. Let's also give them better names:
PRIM_IS_EXT_RACH -> PRIM_IS_RACH11
PRIM_IS_RACH -> PRIM_IS_RACH8
and introduce a new generic one for checking whether a given
primitive is RACH in general (either 8-bit or 11-bit) or not.
Change-Id: Ibc39c57fda000647be1829786f6423dcf3f435cd
Let's avoid fancy alignment in the description of logical channels
for the benefits of having better readability, the ability to add
more comments and fields without making it look ugly.
Also, let's get rid of field 'chan' of 'trx_lchan_desc' structure
since it's not used anywhere, and not actually needed because the
position of each lchan description is defined by its TRXC_* type.
As a bonus, let's add a human readable description to each
lchan definition, so it can be printed in the VTY some day.
Change-Id: I2fc61e1cdca4690a34e2861b9ee3b7c64ea64843
Instead of counting both RSSI and ToA measurements separately,
let's have a single counter in trx_lchan_state.meas struct.
Change-Id: I45454a3ac92b8cc85dd74092e4ab6eb350f20c9a
According to GSM TS 05.02, section 3.3.5, Cell Broadcast Channel
(CBCH) is a downlink only channel, which is used to carry the
short message service cell broadcast (SMSCB). CBCH is optional,
and uses the same physical channel as SDCCH. More precisely,
CBCH replaces sub-slot number 2 of SDCCH channels when enabled.
This change introduces the CBCH enabled multi-frame layouts,
and two separate logical channel types:
- GSM_PCHAN_CCCH_SDCCH4_CBCH (lchan TRXC_SDCCH4_CBCH),
- GSM_PCHAN_SDCCH8_SACCH8C_CBCH (lchan TRXC_SDCCH8_CBCH).
Both logical channels are separately identified using
the following Osmocom specific cbits:
- TRXC_SDCCH4_CBCH - 0x18 (0b11000),
- TRXC_SDCCH8_CBCH - 0x19 (0b11001).
The reason of this separation is that we somehow need to
distinguish between CBCH on C0/TS0, and CBCH on CX/TS0.
Unlike TRXC_SDCCH8_CBCH, TRXC_SDCCH4_CBCH is enabled
automatically (TRX_CH_FLAG_AUTO), so CBCH messages
can be decoded on C0 while being in idle mode.
Change-Id: Iad9905fc3a8a012ff1ada26ff95af384816f9873
According to 3GPP TS 04.08, section 3.4.1, SACCH logical channel
accompanies either a traffic or a signaling channel. It has the
particularity that continuous transmission must occur in both
directions, so on the Uplink direction measurement result messages
are sent at each possible occasion when nothing else has to be sent.
The LAPDm fill frames (0x01, 0x03, 0x01, 0x2b, ...) are not
applicable on SACCH channels!
Unfortunately, 3GPP TS 04.08 doesn't clearly state which "else
messages" besides Measurement Reports can be send by the MS on
SACCH channels. However, in sub-clause 3.4.1 it's stated that
the interval between two successive measurement result messages
shall not exceed one L2 frame.
This change introduces a separate handler for SACCH primitives,
which dequeues a SACCH primitive from transmit queue, if present.
Otherwise it dequeues a cached Measurement Report (the last
received one). Finally, if the cache is empty, a "dummy"
measurement report is used. When it's possible,
a non-MR primitive is prioritized.
Change-Id: If1b8dc74ced746d6270676fdde75fcda32f91a3d
Related: OS#2988
Enforcing pointer to a 'trx_instance' structure is not flexible,
because it is used as parent talloc context only.
Change-Id: I5ab2ef5cea76f955bf72ef54541b3b75cdc2d23f
Having access to a logical channel state is required by the
follow-up change, which will introduce a separate function
for dequeuing SACCH primitives.
Change-Id: Ibde0acf8e6be224b1007be707a636eaad68c8d36
Unlike xCCH, TCH/H channels are using block diagonal interleaving,
so every single burst carries 57 bits of one traffic frame, and 57
bits of another one. Moreover, unlike TCH/F where both traffic
and FACCH/F frames are interleaved over 8 bursts, a FACCH/H is
interleaved over 6 bursts, while a traffic frame is interleaved
over 4 bursts.
This is why a TCH/H burst transmission can't be initiated on
an arbitrary TDMA frame number. It shall be aligned as of
stated in GSM 05.02, clause 7, table 1.
This change introduces two basic functions:
- sched_tchh_block_map_fn - checks if a TCH/H block transmission
can be initiated / finished on a given frame number
and a given channel type;
- sched_tchh_block_dl_first_fn - calculates TDMA frame number of
the first burst using given frame number of the last burst;
and some auxiliary wrappers to simplify the usage of
sched_tchh_block_map_fn().
Change-Id: Iaf4cb33f1b79df23f8a90c8b14ebe0cd9907fbb9
This field of the logical channel state structure was not used at
all as there is nothing related to A-bis / RSL in trxcon itself.
Change-Id: Iec1abf777a74cf57deadafa95e2337cba5d02842
Instead of passing the information about a logical channel, it
makes sense to pass the pointer to its state where everything
is stored. This approach would allow to avoid adding more
arguments every time, e.g. in case of AMR.
Change-Id: I91fe86fef43aac68776a58c9acc37ef2a9ee8042
Initially it was assumed that FACCH prioritization should be done
in the same way for both TCH/F and TCH/H. Moreover, it was not
possible to confirm this, because TCH/H was (and still) not
implemented yet. But according to the specs:
- unlike FACCH/F, FACCH/H transmissions shall be aligned
within a multiframe, i.e. can only be initiated on
particular frame numbers (see GSM 05.02, clause 7);
- unlike FACCH/F, a FACCH/H frame steals two TCH/F frames;
so the TCH/H (including FACCH/H) primitives should be handled
separately from the TCH/F (including FACCH/F) primitives.
Change-Id: I9b59f60e1cbac8fb8fd557b6c67b5e376c0a6bbb
the initial tch_mode is not always 0 (signalling) but can very well
be directly a codec mode, if the initial activation of the channel
is in speech mode as opposed to signalling
Change-Id: I96e4c89da1165e9c5287d863e0e65d811460c606
Since this change, each lchan handler shall manually indicate
a type of both message indications and confirmations.
Change-Id: I02e0b87d61c127d2f6f5b9532909af78332bf707
If at the moment of transmission there are no frames in TX buffer,
then either a dummy LAPDm frame (0x01, 0x03, 0x01, 0x2b ...) or a
silence frame (depending on a codec in use) shall be transmitted.
This is required for proper measurements on the BTS side.
Change-Id: Ie590990f2274ea476678f6b2079f90eeadab6501
This new flag is intended to indicate that continuous burst
transmission is assumed on particular logical channel. In other
words, if a logical channel has this flag, but there is nothing
to transmit in a TX buffer, then either a dummy LAPDm frame or
a silence frame shall be sent.
Change-Id: I25fcf9eeb787ffe5378d92532439e67d7d42fa65
There's no need to express ToA value as a float. Let's turn it into
an int16_t with 1/256 symbol period accuracy throughout the code to
avoid both float arithmetic as well as loosing any precision.
Inspired by Idce4178e0b1f7e940ebc22b3e2f340fcd544d4ec.
Change-Id: I99c0f38db08a530d5846c474aba352aa0b68fe86
As there is no any order relation between logical channels, it's
better to use the linuxlist API instead of talloc array.
Change-Id: I5a78582c77ed1ab33817d240e065dc4cd4708199
This change implements the A5/X ciphering support transparently
for the logical channel handlers. In other words, a DL burst is
deciphered before being passed to a handler, and an UL burst is
ciphered before being sent to transceiver.
The implementation mostly relays on the libosmocore's A5 API.
Change-Id: Ib53418d8c0f394fdece09cf5cc240887cb0bb5af
Having a possibility to preprocess UL burst before sending to
transceiver is required for the further ciphering support
integration and probably some other tasks.
Change-Id: Ia6eead5d4f51d7c0bf277b9d5ebb0a74676df567
Previously, each lchan handler used to obtain and delete primitives
from a timeslot's tranmit queue itself. This approach entails many
potential problems and bugs:
- The lchan handlers shall not do that by definition, they
should encode and decode frames according to GSM 05.03.
- In some cases (e.g. TCH), a single transmit queue may contain
primitives of different types (e.g. TCH, FACCH and SACCH). At
the same time, the lchan handlers don't care and don't even
know about each other. So, this could cause an unexpected
behaviour in some cases.
This change separates all primitive management routines,
providing a new API for obtaining and dropping them.
"Write programs that do one thing and do it well."
Change-Id: I29503ece51903784bc53541015285234471c8d15
It's good to write, keep and make the source code as much modular
as possible. So, Tte primitive management code was separated to
the 'sched_prim.c' and going to be extended in the near future.
Change-Id: Ifec8c9e4f2c95c72b00772688bcb5dc9c11d6de7
Previously, we used to drop a frame if decoding wasn't successful.
This way, the higher layers didn't even know about that, so the
local counters and Measurement Reports were incomplete.
This change makes scheduler to forward L2 frames in any case,
setting the num_biterr for each of them. In case of decoding
error, a dummy (payload filled by 0x00) L2 frame will be sent.
Change-Id: I31011d8f3ca8b9a12474cd0bc653faed18391033
This change implements basic TCH/F lchan handlers for both data
reception and transmission. Only FACCH (signaling), FR and EFR
payloads are supported at the moment.
Change-Id: If6b0eaede2b484484d2a824e7219ff04483266a1
There were some BTS specific variables, which are meaningless.
This change cleans them up, and also groups some measurement,
encryption, and AMR specific variables into sub-structures.
Change-Id: Ie753a7e3e7fa2b433d8319b3a05b85b8583d7be2
In order to get the transceiver more time to process bursts,
the L1 scheduler should process the frames and send the bursts
in advance (a few frames before), like OsmoBTS does. By default,
the advance value is 20 frames, but this can be adjusted using a
new command line option of trxcon '-f'.
Change-Id: Ic258a169f3554f931d6277e18ca060d029b77f32
The training sequences, data / traffic indication and confirmation
helpers are used by several lchan handlers, like xCCC and TCH. It
would be better to have them all declared within a shared header.
Change-Id: I71980f09a0c0e023370e1a651afc24fff2491552
This change introduces shared primitive management functions,
exposed from the l1ctl_rx_data_req() implementation:
- sched_trx_init_prim() - allocates memory for a new primitive
and its payload. Initializes primitive's header, setting
the logical channel type and the payload length. After
initialization, the talloc context of a primitive is
a trx instance, which passed as the first argument.
- sched_trx_push_prim() - decodes the timeslot index from
chan_nr and pushes a primitive to its transimt queue.
The talloc context of primitive is changed to the
parent trx_ts instance after queuing.
Both functions will be used for handling both L1CTL_TRAFFIC_REQ
and L1CTL_RACH_REQ.
Change-Id: I8169a1ef4ef54d91b50f3e213e4842f54af8b499
It's better to pass a trx_lchan_state instance directly from
caller to lchan handler instead of passing trx_lchan_type. This
way a handler wouldn't need to find lchan itself.
Change-Id: I47a40542b03ab31da12b0abb1c263c83662ff018
Previously, the chan_nr, received from L2, was parsed in a wrong
way, so in some cases only one logical channel was activated or
some messages (such as Measurement Requests) were sent on
incorrect channel (e.g. on SDCCH instead of SACCH).
This change reimplements the sched_trx_chan_nr2lchan_type(), and
introduces a new function sched_trx_set_lchans(), whics will
parse chan_nr and (de)activate required channels.
Change-Id: I480311c65ef93bbc1644ec708dd2a68fd33091e0
Vadim Yanitskiy
Vadim Yanitskiy
Pau Espin
Harald Welte