It may happen that the BSC requests logical channel activation on a
dynamic timeslot, which is in a process of switching from one pchan
type to another due to a preceding channel activation request.
In this case 'struct gsm_bts_trx_ts' already holds an msgb with the
preceding RSL CHANnel ACTIVation message, that is normally handled
once the PHY completes the process of timeslot re-configuration.
On receipt of subsequent RSL CHANnel ACTIVation messages, in function
dyn_ts_l1_reconnect() we overwrite the preceeding msgb (memleak), by
the most recent one. And once the timeslot re-configuration is done,
only the most recent CHANnel ACTIVation message gets ACKed.
In order to avoid this, let's move the msgb ownership to 'struct
gsm_lchan', so it cannot be overwritten by the CHANnel ACTIVation
message that is related to a different lchan on the same timeslot.
Change-Id: Ia625c2827fca883ea712076706d5ef21ed793ba6
Related: I3b602ac9dbe0ab3e80eb30de573c9b48a79872d8
Fixes: OS#5245
Let's split all lchan and power_control specific stuff into their own headers,
it helps finding out data and operations available related to them.
We already have similar classification in osmo-bsc.
Change-Id: I6424dcbd2e329fc1a516f8886359554ed7e9487e
Have a more stable loop with less temporary oscillations at the expense
of increased reaction time.
4 SACCH blocks (P_CON_INTERVAL=2) is the minimum interval to get stable
measurements for the last requested MS Power level. With P_CON_INTERVAL=1,
are also made during a period with stable power being use to transmit,
but the MS Power level used (and announced in MR) is not the last one
requested by the BTS, but the one requested in the previous loop
iteration. This can make the MS and BTS bounce 2 values forth and back,
and create some temporary oscillation.
See osmo-bsc User manual section "Power Control" for more information.
Related: SYS#5371
Change-Id: I91c505447f68714239a4f033d4f06e91893df201
GSM/EDGE Evolution and Performance, Section 12.3 suggests Temporary
Overpower as another solution to improve SACCH/FACCH performance in
case of bad C/I. The idea here is that you increment the DL transmit
power by 2..4dB only for FACCH/SACCH bursts, while keeping all voice
bursts at the lower (normal) level as determined by BS power control.
SACCH blocks can be recognized by the channel type, since they're
always transmitted in specific frames of a multiframe. FACCH blocks,
however, are not predictable and can substitute voice blocks at
(almost) any time. Thus we need to mark FACCH bursts as such in
the logical channel handlers (using TRX_BR_F_FACCH).
Change-Id: Ie8a626fefccf1eb07271058e5126ec106cb1abcf
Related: SYS#5319
The ip.access style dynamic timeslots are a bit special in a way that
on the A-bis/RSL we always use the Channel Number value of TCH/F,
even in PDCH mode. This is why gsm_lchan2chan_nr() would always
return values corresponding to TCH/F for TCH/F_PDCH.
This behavior is only acceptable in the context of RSL messages, while
other parts of the code base may not work properly due to this trick.
A good example is the scheduler in osmo-bts-trx, where we have to
patch Channel Number value to make channel activation work.
DPCU INFO pcu_sock.c:853 Activate request received: TRX=0 TS=5
DL1C INFO l1sap.c:2043 (bts=0,trx=0,ts=5,ss=0) Activating channel TCH/F on TS5
DL1C NOTICE scheduler.c:1097 (bts=0,trx=0,ts=5,ss=0) Activating PDTCH
DL1C NOTICE scheduler.c:1097 (bts=0,trx=0,ts=5,ss=0) Activating PTCCH
In the code branch responsible for channel deactivation, we somehow
forgot to add the same workaround, so deactivation does not work:
DL1C INFO l1sap.c:2076 (bts=0,trx=0,ts=5,ss=0) Deactivating channel TCH/F on TS5
DTRX INFO trx_if.c:255 phy0.0: Enqueuing TRX control command 'CMD NOHANDOVER 5 0'
DRSL NOTICE rsl.c:1286 (bts=0,trx=0,ts=5,ss=0) (bts=0,trx=0,ts=5,ss=0) not sending REL ACK
Because of that, TCH/F_PDCH timeslots actually remain active after
deactivation, so the scheduler keeps producing L1SAP DATA.ind.
DL1P NOTICE l1sap.c:126 (bts=0,trx=0,ts=5,ss=0) assuming active lchan, but state is NONE
DL1P ERROR l1sap.c:732 1583426/1194/00/29/14 No lchan for DATA MEAS IND (chan_nr=PDCH on TS5)
DPCU NOTICE pcu_sock.c:973 PCU socket not connected, dropping message
DL1P NOTICE l1sap.c:126 (bts=0,trx=0,ts=5,ss=0) assuming active lchan, but state is NONE
DPCU NOTICE pcu_sock.c:973 PCU socket not connected, dropping message
DL1P NOTICE l1sap.c:126 (bts=0,trx=0,ts=5,ss=0) assuming active lchan, but state is NONE
DL1P ERROR l1sap.c:732 1583430/1194/04/33/18 No lchan for DATA MEAS IND (chan_nr=PDCH on TS5)
DPCU NOTICE pcu_sock.c:973 PCU socket not connected, dropping message
DL1P NOTICE l1sap.c:126 (bts=0,trx=0,ts=5,ss=0) assuming active lchan, but state is NONE
DPCU NOTICE pcu_sock.c:973 PCU socket not connected, dropping message
Instead of patching Channel Number in various places, let's rather
make the RSL specific behavior configurable by having two variants
of gsm_lchan2chan_nr().
Change-Id: I01680140c7201bf5284b278bceaea8ae01c122b2
Fixes: OS#5238
Similar to what is already provided for power control loops. However,
there's no existing way to communicate TA control parameters from the
BSC to the BTS, so implement them locally in BTS vty.
Related: SYS#5371
Change-Id: I9fa71f836bb9a79b0ef2567bfcfdf38ff217840b
As per 3GPP TS 45.008 sec 4.2, the ms_pwr received in L1 SACCH Header is
the value used over previous measurement period. Hence, we need to feed
the algo with the measurements taken over that same period.
Related: SYS#4917
Change-Id: I13c0014fdd73f823ae5b1256c35bfa7d97cfa334
Field is renamed to look similar to similar fields in power control
loop. This is a preparation commit, next one will add functionality to
skip SACCH blocksi (P_CON_INTERVAL).
Related: SYS#5371
Change-Id: I169ce58ab827e38b64f4b15f935097a9118fa118
During live testing, it has become apparent that some IMM ASS still fail
when sending the RR IMM ASS directly upon the target channel becoming
active.
Add a bit of delay after activation, to give some time for the channel
to light up for the MS. Default is 50ms.
Related: OS#5559
Change-Id: Ia1e63b98944dc840cde212fc732e20277cdc5585
params->rxqual_meas.upper_thresh is left unchecked in
lchan_bs_pwr_ctrl() on this commit on purpose, to keep this
commit with old behavior wrt to algo logic.
Change-Id: If7e3987df89d680cfa443195ab2f225681d0e6cf
This commit extends existing MS Power Control Loop algorithm to take
into account computed C/I values on the UL, received from MS. The
related C/I parameters used by the algorithm are configured at and
provided by the BSC, which transmits them to the BTS similar to already
existing parameters.
Using C/I instead of existing RxQual is preferred due to extended
granularity of C/I (bigger range than RxQual's 0-7).
Furthermore, existing literature (such as "GSM/EDGE: Evolution and Performance"
Table 10.3) provides detailed information about expected target values,
even different values for different channel types. Hence, it was decided
to support setting different MS Power Parameters for different channel
types.
These MS Power Parameters are Osmocom specific, ie. supported only by
newish versions of osmo-bts. Older versions of osmo-bts should ignore
the new IEs added just fine. The new IEs containing the MS POwer
Parameters are not send for non osmo-bts BTSs, hence this commit is
secure with regards to running osmo-bsc against an ip.access BTS such
as nanoBTS.
Related: SYS#4917
Depends: libosmocore.git Change-Id Iffef0611430ad6c90606149c398d80158633bbca
Change-Id: I5dfd8ff9ab6b499646498b507624758dcc160fb6
We have two osmocom specific timers used in the BTS, X1 and X2. Expose
those on the VTY configuration, as timer group 'bts'.
This prepares for a subsequent patch, where I would like to add another
configurable timer. This provides the basic infrastructure for that.
Related: SYS#5559
Change-Id: I0f56f9425134679219884b0c3c2f29e77aff5e64
When an Immediate Assignment comes in targeting an lchan that is not yet
active, then hold back the RR Immediate Assignment until the channel
becomes active.
This allows the BSC to send the Immediate Assignment before first
waiting for the Channel Activation ACK, saving one Abis roundtrip, and
helping avoid double allocation on high latency Abis links.
Related: SYS#5559
Related: I56c25cde152040fb66bdba44399bd37671ae3df2 (osmo-bsc)
Related: Ifb2c62431a91dafa6116b5d6b9410930f00a6e18 (osmo-ttcn3-hacks)
Change-Id: Ie52765b238b01f22fb327fe12327fbf10abcad4c
The BCCH carrier (sometimes called C0) of a BTS shall maintain
discontinuous Downlink transmission at full power in order to
stay 'visible' to the mobile stations. Because of that, early
versions of 3GPP TS 45.008 prohibited BS power reduction on C0.
However, in the recent 3GPP TS 45.008 there is a feature called
'BCCH carrier power reduction operation'. This is a special
mode of operation, where the variation of RF level for some
timeslots is relaxed for the purpose of energy saving.
In BCCH carrier power reduction operation, for timeslots on the
C0 carrier, except timeslots carrying BCCH/CCCH, the output power
may be lower than the output power used for timeslots carrying
BCCH/CCCH. In this case the maximum allowed difference in output
power actually transmitted by the BTS is 6 dB.
The power reduction operation can be controlled by the BSC by
sending BS POWER CONTROL on the A-bis/RSL with the Channel Number
IE set to 0x80 (RSL_CHAN_BCCH). This makes osmo-bts reduce the
transmission power on inactive timeslots of the BCCH carrier.
This is a non-standard, Osmocom specific extension, so indicate
support of this feature to the BSC in the feature vector. Also
add a VTY command to allow enabling/disabling the power reduction
locally. Add some signalling notes to the A-bis/RSL manual.
For more details, see 3GPP TS 45.008, section 7.1.
Change-Id: I3dcee6e910ccc61c5c63c728db9ea04327e2fc98
Depends: I69283b3f35988fc7a1a1dcf1a1ad3b67f08ec716
Related: SYS#4919
This change implements general interference averaging logic for
the higher layers. In l1sap_info_time_ind(), where we receive
TDMA time updates from BTS model, call rsl_tx_rf_res() for each
transceiver according to the interval defined by the Intave
parameter received from the BSC. In rsl_tx_rf_res() perform
the actual averaging for each inactive logical channel, and
then send everything to the BSC over the A-bis/RSL.
The BTS model specific code needs to report the measurements
for each logical channel every 104 TDMA frames (SACCH period)
by calling gsm_lchan_interf_meas_push().
Change-Id: Id80fdbef087de625149755165c025c0a9563dc85
Related: SYS#5313, OS#1569
The TSC (Training Sequence Code) value in 'struct gsm_bts_trx_ts'
is always initialized in oml_rx_set_chan_attr() during the OML
bootstrapping, so there is no need for gsm_ts_tsc() - remove it.
Store the initial TSC value in 'struct gsm_bts_trx_ts', so we can
apply a different TSC value during the RSL CHANnel ACTIVation.
Store the Training Sequence Code/Set in 'struct trx_dl_burst_req'.
These values are indicated to the transceiver (TRXDv2 PDUs, 'MTS'
field) and used by the new TRX_{GMSK,8PSK}_NB_TSC macros.
Change-Id: I3744bc308b99ef941e6e9d139444e414abebc14b
Related: SYS#4895, OS#4941
BCC takes 3 LSB bits of the BSIC, so we should apply 0b111 or 0x07.
The BSIC is specified in 3GPP TS 03.03 section 4.3.2.
Change-Id: Id24ad64e6c6de080ab43faa272daf844fbba6954
Related: SYS#5315, OS#4940
Together with the 'generic' structures which used to be shared between
osmo-bsc and osmo-bts some time ago, we also have the following
osmo-bts-trx specific structures (in hierarchical order):
- struct l1sched_trx (struct gsm_bts_trx),
- struct l1sched_ts (struct gsm_bts_trx_ts),
- struct l1sched_chan_state (struct gsm_lchan).
These structures are not integrated into the tree of the generic
structures, but maintained in a _separate tree_ instead. Until
recently, only the 'l1sched_trx' had a pointer to generic
'gsm_bts_trx', so in order to find the corresponding 'gsm_lchan' for
'l1sched_chan_state' one would need to traverse all the way up to
'l1sched_trx' and then tracerse another three backwards.
+ gsm_network
|
--+ gsm_bts (0..255)
|
--+ l1sched_trx --------------------> gsm_bts_trx (0..255)
| |
--+ l1sched_trx_ts --+ gsm_bts_trx_ts (8)
| |
--+ l1sched_chan_state --+ gsm_lchan (up to 8)
I find this architecture a bit over-complicated, especially given
that 'l1sched_trx' is kind of a dummy node containing nothing else
than a pointer to 'gsm_bts_trx' and the list of 'l1sched_trx_ts'.
In this path I slightly change the architecture as follows:
+ gsm_network
|
--+ gsm_bts (0..255)
|
--+ gsm_bts_trx (0..255)
|
--+ l1sched_trx_ts <----------------> gsm_bts_trx_ts (8)
| |
--+ l1sched_chan_state --+ gsm_lchan (up to 8)
Note that unfortunately we cannot 1:1 map 'l1sched_chan_state' to
'gsm_lchan' (like we do for 'l1sched_trx_ts' and 'gsm_bts_trx_ts')
because there is no direct mapping. The former is a higl-level
representation of a logical channel, while the later represents
one specific logical channel type like FCCH, SDCCH/0 or SACCH/0.
osmo-bts-virtual re-uses the osmo-bts-trx hierarchy, so it's also
affected by this change.
Change-Id: I7c4379e43a25e9d858d582a99bf6c4b65c9af481
The MS sets the SRR bit in the L1 SACCH header to request DL-SACCH
repetition from the BTS. At the moment we access the l1_info stored in
tle lchan struct each time we want to check the status of the SRR bit.
However, it is more convinient to do this once at reception and store
the status of the status of the flag in a separate struct member.
Change-Id: Ieddd45d7890343d64db14b9c726f6fa2f25714f6
Related: SYS#5114
in struct gsm_lchan and also in other places l1_info is handled in its
binary form. Libosmocore now offers structs to handle l1 info, so lets
use those structs to get rid of all the manual decoding of l1_info.
Depends: libosmocore I23c1890b89d5a0574eb05dace9f64cc59d6f6df7
Change-Id: I5eb516d7849750f3dd174d48c9f07dabf2c80515
In change [1] the new power control structures and default params
were introduced. In change [2], the existing VTY commands for MS
power control in the BTS were deprecated and changed to use the
new structures as storage. Finally, in change [3], handling of
the power control parameters on the A-bis/RSL was implemented.
This change is the final logical step in the mentioned chain: it
makes both MS/BS power control loops use the new parameters, and
removes the old structures. The actual implementation of both
power control loops remains the same, however the expected output
of some unit tests for the Downlink loop needs to be changed:
- TC_fixed_mode: disabling dynamic power control becomes a separate
step of the test script since the field 'fixed' is removed;
- TC_rxlev_target: RxLev thresholds are printed 'as-is'.
Not all of the new parameters are used by the power control loops
yet. Further improvements to be done in the follow up commits.
[1] I6d41eb238aa6d4f5b77596c5477c2ecbe86de2a8
[2] Icbd9a7d31ce6723294130a31a179a002fccb4612
[3] I5a901eca5a78a0335a6954064e602e65cda85390
Change-Id: Ib18f84c40227841d95a36063a6789bf63054fc2e
Related: SYS#4918
For the sake of simplicity, the old structures that are still used
by MS/BS power control loops are kept in place. Migration to the
new structures requires additional changes to the existing power
control logic, so it will be done in the follow-up changes.
The new parameters are integrated as follows:
+ struct gsm_bts - a BTS instance:
| Hard-coded default (fall-back) parameters for all transceivers.
|
+-+-> struct gsm_bts_trx - a TRX instance (transceiver):
| Default parameters for all logical channels inherited from
| 'struct gsm_bts' at start-up. May be overwritten by the
| BSC using ip.access specific 'Measurement Pre-processing
| Defaults' message on the A-bis/RSL interface.
|
+---> struct gsm_lchan - a logical channel (e.g. TCH or SDCCH):
Connection specific parameters inherited from 'struct
gsm_bts_trx'. May be overwritten by parameters sent
by the BSC in CHANnel ACTIVation and other messages.
Change-Id: I6d41eb238aa6d4f5b77596c5477c2ecbe86de2a8
Related: SYS#4918
We already have MS Power Control, which according to 3GPP 45.008
shall be implemented in the MS to minimize the transmit power in
the Uplink direction. The BS Power Control may optionally be
implemented by the network side for the same purpose.
Using Downlink signal measurements reported by the MS, the BSS
(either BSC, or BTS) may control Downlink attenuation in a way
that the transmit power remains as low as possible, or remains
in a specific range corresponding to good RxLev values on the
MS side. This change implements autonomous BS Power Control,
that can optionally be enabled by the BSC.
BS Power Control re-uses parts of the MS Power Control code,
so all parameters can be configured in the same way - via the
VTY interface or a configuration file. This basically means
that features like hysteresis and EWMA based filtering are
also available for BS Power Control.
The only difference is that RxQual values higher than 0 would
trigger the logic to reduce the current attenuation twice.
Note that one of the unit tests ('TC_rxlev_max_min') fails,
as the power step limitations for raising and lowering look
wrong to me, and the related discussion is still ongoing.
Change-Id: I5b509e71d5f668b6b8b2abf8053c27f2a7c78451
Related: SYS#4918
3GPP TS 44.006, section 11 describes a method how the uplink
SACCH transmission can be repeated to increase transmission
reliability.
Change-Id: I7e4cc33cc010866e41e3b594351a7f7bf93e08ac
Related: OS#4795, SYS#5114
3GPP TS 44.006, section 11 describes a method how the downlink
SACCH transmission can be repeated to increase transmission
reliability.
Change-Id: I00806f936b15fbaf6a4e7bbd61f3bec262cdbb28
Related: OS#4794, SYS#5114
3GPP TS 44.006, section 10 describes a method how the downlink
FACCH transmission can be repeated to increase transmission
reliability.
Change-Id: I72f0cf7eaaef9f80fc35e752c90ae0e2d24d0c75
Depends: libosmocore I6dda239e9cd7033297bed1deb5eb1d9f87b8433f
Related: OS#4796 SYS#5114
This part adds the common lchan flags to indicate whether DL SACCH
should be activated.
Note that currently, osmo-bsc *always* sends the MS Power IE as well as
the TA IE, also for inter-cell HO, so in the osmoverse, nothing will
change until we also adjust osmo-bsc. See OS#4858.
Change-Id: Ibea973ccadf5d424213f141f97a61395856b76de
So far the Uplink power control loop did not filter the Uplink RSSI
measurements (reported by the BTS) at all. The lack of filtering
makes our implementation too quick on the trigger, so in the real
deployments there will be unneeded Tx power oscillations.
In order to reduce this effect, let's implement a very simple EWMA
(also known as Single Pole IIR) filtering that is defined as follows:
Avg[n] = a * Pwr[n] + (1 - a) * Avg[n - 1]
where parameter 'a' determines how much weight of the latest UL RSSI
measurement result 'Pwr[n]' carries vs the weight of the average
'Avg[n - 1]'. The value of 'a' is usually a float in range 0 .. 1, so:
- value 0.5 gives equal weight to both 'Pwr[n]' and 'Avg[n - 1]';
- value 1.0 means no filtering at all (pass through);
- value 0.0 makes no sense.
This formula was further optimized with the use of '+=' operator.
The floating point math was also eliminated by scaling everything
up (by 100). For more details, see:
https://en.wikipedia.org/wiki/Moving_averagehttps://en.wikipedia.org/wiki/Low-pass_filter#Simple_infinite_impulse_response_filterhttps://tomroelandts.com/articles/low-pass-single-pole-iir-filter
The EWMA filtering is now *enabled by default*, but can be disabled
or (re-)configured over the VTY at any time:
! Completely disable filtering
no uplink-power-filtering
! Enable EWMA smoothing with the given parameters
uplink-power-filtering algo ewma beta <1-99>
Note that the VTY command expects 'beta' instead of 'alpha':
alpha = (100 - beta)
and the value must be in %. This is done for simplicity:
1% means lowest smoothing,
99% means highest smoothing.
Let's say we have EWMA filtering enabled with alpha = 0.4, and get
-98 dBm on the input, while the last output value was -60 dBm.
The new output would be:
Avg[n] = 0.4 * Pwr[n] + 0.6 * Avg[n - 1]
Avg[n] = (0.4 * -98) + (0.6 * -60)
Avg[n] = -75.2 => around -75
Of course, this is not a silver bullet, but better than nothing.
Change-Id: Ib6dcadbf14ef59696c6a546bd323bda92d399f17
Related: SYS#4916
MA (Mobile Allocation) is actually a bit-mask indicating those ARFCNs
of the Cell Allocation, which must be used as the hopping sequence.
What we store in struct gsm_bts_trx_ts is the actual list of hopping
channels, so let's name it properly and eliminate possible confusion.
Change-Id: I677d66e428fa0fe119ebc37bc2a4e6cc05c251c4
The idea behind the baseband frequency hopping is quite simple: we
have several RF carriers (transceivers) transmitting and receiving
on fixed frequencies (just like in a regular multi-trx setup), and
an additional burst routing layer between the schedulear and the
transceiver interface (TRXD over UDP).
Speaking in terms of the proposed implementation:
- on Downlink, dlfh_route_br() calculates the ARFCN corresponding
to the current TDMA frame number according to the hopping sequence
parametets, and picks the transceiver with matching ARFCN;
- on Uplink, ulfh_route_bi() iterates over the transceiver list of
of the BTS, calculating hopping ARFCNs for equivalent timeslots,
and picks the one with ARFCN matching the received burst.
In order to avoid frequent transceiver lookups on the Downlink path,
dlfh_route_br() maintains a "cache" in the timeslot state structure.
Unfortunately, this "cache" seems to be useless on the Uplink path,
so ulfh_route_bi() always needs to lookup the matching transceiver
for each burst received over the TRXD interface.
It may also happen that the scheduler will be unable to route an
Uplink or Downlink burst, e.g. due to inconsistent / incorrect
hopping sequence parameters received from the BSC, or in case
if a transceiver gets RF-locked by the BTS operator.
Such events are logged as "FATAL" and aditionally signalled by the
following osmo-bts-trx specific rate counters:
- trx_sched:dl_fh_no_carrier (Downlink), and
- trx_sched:ul_fh_no_carrier (Uplink).
Change-Id: I68f4ae09fd0789ad0d8f1c1e17e17dfc4de8e462
Related: SYS#4868, OS#4546
Move all struct gsm_bts_trx references from bulky gsm_data to its own
file containing all related definitions and implementations. Also move a
few functions clearly related to that object which were placed in bts.*
Change-Id: Iebaf5b221c48b571f45408af867ce6f9c0cd9f4a
bts.h refers to struct gsm_bts object, but we still had a bunch of stuff
in bulky gsm_data.* from old days. Let's move stuff where it belongs to
start clean up of gsm_data.
Change-Id: I0a4219e3f64f625ee8b364bf408b8d2bcc8085c5
Vadim Yanitskiy
Pau Espin
Neels Hofmeyr
Philipp Maier