Commit
c80e193f6d95367e764684a6021ede981f44ebbd
by Kirill Smelkovtrxcon: Advance Uplink TDMA Fn by default again
This essentially reverts 923e9b0b (trxcon: do not advance Uplink TDMA Fn
by default; I838b1ebc54e4c5d116f8af2155d97215a6133ba4) for the following
reason:
In trxcon TRX clock is unused, because the signal from BTS is used as
the master clock source instead (see 45c821ae/Ic8a5b6277c6b16392026e0557376257d71c9d230
"trxcon: get rid of the timer driven clock module" for details".
Before restoration of tx-queue in fake_trx this was working ok even with
fn-advance=0 on Ms side, but after I41291708effdd2c767be680fff22ffbd9a56815e
(Revert "Revert "trx_toolkit/transceiver.py: implement the transmit
burst queue"") fake_trx is sending frames having Fn when exactly same Fn
happens corresponding on fake_trx clock. This results in BTS frames
(that are sent with fn-advance=2 by default (see
I7da3d0948f38e12342fb714b29f8edc5e9d0933d in osmo-bts.git and OS#4487)
to be queued, waited to be sent, and then actually sent to Ms on
fn=msg.fn . And then even if Ms replies immediately with that same fn,
that message will be dropped by fake_trx as stalled, because fake_trx
thinks that the message is too late since that fn already happened
according to fake_trx clock.
Here is a trace of how that looks like with 1 BTS and 1 MS(*):
7.106.927 CLOCK fn=80 # fake_trx running
7.111.592 CLOCK fn=81
7.116.289 CLOCK fn=82
7.120.949 CLOCK fn=83
7.125.523 CLOCK fn=84
7.130.000 CLOCK fn=85
7.134.575 CLOCK fn=86
...
7.209.222 CLOCK fn=102
7.209.897 BTS -> fn=104 tn=0 # BTS starts to emit RF
7.210.221 BTS -> fn=104 tn=1
7.210.556 BTS -> fn=104 tn=2
7.210.796 BTS -> fn=104 tn=3
7.211.019 BTS -> fn=104 tn=4
7.211.234 BTS -> fn=104 tn=5
7.211.479 BTS -> fn=104 tn=6
7.211.768 BTS -> fn=104 tn=7
7.213.086 CLOCK fn=103
7.214.354 BTS -> fn=105 tn=0
7.214.566 BTS -> fn=105 tn=1
7.214.685 BTS -> fn=105 tn=2
7.214.792 BTS -> fn=105 tn=3
7.214.890 BTS -> fn=105 tn=4
7.214.985 BTS -> fn=105 tn=5
7.215.083 BTS -> fn=105 tn=6
7.215.184 BTS -> fn=105 tn=7
7.217.823 CLOCK fn=104
7.218.869 BTS -> fn=106 tn=0
7.219.092 BTS -> fn=106 tn=1
7.219.224 BTS -> fn=106 tn=2
7.219.330 BTS -> fn=106 tn=3
7.219.431 BTS -> fn=106 tn=4
7.219.527 BTS -> fn=106 tn=5
7.219.621 BTS -> fn=106 tn=6
7.219.718 BTS -> fn=106 tn=7
7.222.535 CLOCK fn=105
...
9.995.869 CLOCK fn=706 # MS will soon connect.
9.997.138 BTS -> fn=709 tn=0 # Note: BTS is sending fn=709 before CLOCK fn=707
9.997.338 BTS -> fn=709 tn=1 # so this messages become queued before CLOCK fn=709 happens
9.997.444 BTS -> fn=709 tn=2
9.997.535 BTS -> fn=709 tn=3
9.997.620 BTS -> fn=709 tn=4
9.997.708 BTS -> fn=709 tn=5
9.997.789 BTS -> fn=709 tn=6
9.997.874 BTS -> fn=709 tn=7
10.000.583 CLOCK fn=707
10.001.735 BTS -> fn=710 tn=0
10.001.932 BTS -> fn=710 tn=1
10.002.041 BTS -> fn=710 tn=2
10.002.134 BTS -> fn=710 tn=3
10.002.220 BTS -> fn=710 tn=4
10.002.373 BTS -> fn=710 tn=5
10.002.459 BTS -> fn=710 tn=6
10.002.718 BTS -> fn=710 tn=7
[DEBUG] ctrl_if_trx.py:115 (MS) Recv POWEROFF cmd # MS starts to connect
[INFO] ctrl_if_trx.py:117 (MS) Stopping transceiver...
[DEBUG] ctrl_if_trx.py:229 (MS) Ignore CMD ECHO
10.005.203 CLOCK fn=708
[DEBUG] ctrl_if_trx.py:229 (MS) Ignore CMD SETSLOT
10.006.406 BTS -> fn=711 tn=0
[DEBUG] ctrl_if_trx.py:124 (MS) Recv RXTUNE cmd
10.006.999 BTS -> fn=711 tn=1
10.007.153 BTS -> fn=711 tn=2
[DEBUG] ctrl_if_trx.py:131 (MS) Recv TXTUNE cmd
10.007.590 BTS -> fn=711 tn=3
10.007.728 BTS -> fn=711 tn=4
[DEBUG] ctrl_if_trx.py:97 (MS) Recv POWERON CMD # MS connected and activated RF
[INFO] ctrl_if_trx.py:109 (MS) Starting transceiver...
10.008.344 BTS -> fn=711 tn=5
10.008.471 BTS -> fn=711 tn=6
10.008.563 BTS -> fn=711 tn=7
10.009.868 CLOCK fn=709 # CLOCK fn=709 happens
10.009.987 MS <- fn=709 tn=0 # messages of BTS queued previously with that fn=709 are forwarded to Ms
10.010.696 MS <- fn=709 tn=1
10.010.904 MS -> fn=709 tn=0 # <-- MS sends UL message with that same fn=709 _before_ CLOCK fn=710
10.011.397 BTS -> fn=712 tn=0
10.011.507 MS <- fn=709 tn=2
10.011.770 MS <- fn=709 tn=3
10.011.968 MS <- fn=709 tn=4
10.012.156 MS <- fn=709 tn=5
10.012.342 MS <- fn=709 tn=6
10.012.527 MS <- fn=709 tn=7
10.012.914 BTS <- fn=709 tn=0
10.013.166 BTS -> fn=712 tn=1
10.013.524 MS -> fn=709 tn=1 # <-- MS sends UL message with that same fn=709 _before_ CLOCK fn=710
10.013.832 BTS -> fn=712 tn=2
10.013.949 MS -> fn=709 tn=2 # <-- MS sends UL message with that same fn=709 _before_ CLOCK fn=710
10.014.081 BTS -> fn=712 tn=3
10.014.177 MS -> fn=709 tn=3 # <-- MS sends UL message with that same fn=709 _before_ CLOCK fn=710
10.014.361 BTS -> fn=712 tn=4
10.014.475 CLOCK fn=710 # but most of those messages of MS with fn=709 are not picked up
10.014.713 MS -> fn=709 tn=4 # instantly and so become dropped as stale on CLOCK fn=710
10.014.815 MS <- fn=710 tn=0
10.015.032 BTS -> fn=712 tn=5
10.015.687 MS <- fn=710 tn=1
10.016.189 MS <- fn=710 tn=2
10.016.464 MS <- fn=710 tn=3
10.016.648 MS <- fn=710 tn=4
10.016.882 MS <- fn=710 tn=5
10.017.110 MS <- fn=710 tn=6
10.017.336 MS <- fn=710 tn=7
[WARNING] transceiver.py:321 (MS) Stale TRXD message (fn=710): fn=709 tn=1 pwr=0
[WARNING] transceiver.py:321 (MS) Stale TRXD message (fn=710): fn=709 tn=2 pwr=0
[WARNING] transceiver.py:321 (MS) Stale TRXD message (fn=710): fn=709 tn=3 pwr=0
[WARNING] transceiver.py:321 (MS) Stale TRXD message (fn=710): fn=709 tn=4 pwr=0
So without adding some fn-advance it is practically not possible for Ms
to be on time with tx-queueing on TRX even if Ms sends its uplink frames
right immediately after receiving downlink ones.
This way Ms fn-advance has to be 1 at the minimum, so that immediate UL
replies can in principle arrive before fn+1 happens on fake_trx side,
even for tn=7. And it is also better to increase fn-advance once more by
another +1, to compensate for possible jitter due to OS scheduling
latencies and similar things. This way default fn-advance=2 on Ms side
becomes symmetric to default fn-advance on BTS side and Ms<->BTS
exchange starts to work ok even with tx-queueing activated on fake_trx.
In theory it should be possible to reduce those fn-advances to 1 on both
sides, but that will likely require to switch clock granularity from Fn
to Tn increasing precision by an order of magnitude, which will likely
also result in the need to make architectural change of moving trx to
work inside BTS and MS instead of being separate service processes.
That's a big task and I'm not delving into that here.
Note: Uplink Fn advance > 0 is needed for Ms when working with regular
TRX'es as well. The reason is exactly the same as explained above. In
923e9b0b the reason for setting fn-advance=0 by default was that trxcon
is usually being used with fake_trx, and that with fake_trx it is not
needed. But after reenabling tx-queueing we have to revisit even
fake_trx case again.
(*) the trace was captured with the help of the following debugging patch:
--- b/src/target/trx_toolkit/burst_fwd.py
+++ a/src/target/trx_toolkit/burst_fwd.py
@@ -22,6 +22,18 @@
from trx_list import TRXList
+import sys, time
+
+# trace logs msg to stderr with also marking it with high-resolution timestamp.
+t0 = time.time()
+def trace(msg):
+ t = time.time() - t0
+ t_ms = int(t * 1e3) / 1e3
+ us = int((t - t_ms) * 1e6)
+ print("%7.3f.%03d %s" % (t_ms, us, msg), file=sys.stderr)
+
class BurstForwarder(TRXList):
""" Performs burst forwarding between transceivers.
@@ -63,6 +75,7 @@ def forward_msg(self, src_trx, rx_msg):
if trx.get_rx_freq(rx_msg.fn) != tx_freq:
continue
+ trace("%s\t<- fn=%d\ttn=%d" % (trx, rx_msg.fn, rx_msg.tn))
# Transform from TxMsg to RxMsg and forward
tx_msg = rx_msg.trans(ver = trx.data_if._hdr_ver)
trx.handle_data_msg(src_trx, rx_msg, tx_msg)
--- b/src/target/trx_toolkit/fake_trx.py
+++ a/src/target/trx_toolkit/fake_trx.py
@@ -29,7 +29,7 @@
import re
from app_common import ApplicationBase
-from burst_fwd import BurstForwarder
+from burst_fwd import BurstForwarder, trace
from transceiver import Transceiver
from data_msg import Modulation
from clck_gen import CLCKGen
@@ -473,6 +473,7 @@ def run(self):
# This method will be called by the clock thread
def clck_handler(self, fn):
+ trace("CLOCK\tfn=%d" % fn)
# We assume that this list is immutable at run-time
for trx in self.trx_list.trx_list:
trx.clck_tick(self.burst_fwd, fn)
--- b/src/target/trx_toolkit/transceiver.py
+++ a/src/target/trx_toolkit/transceiver.py
@@ -25,6 +25,7 @@
from data_if import DATAInterface
from udp_link import UDPLink
from trx_list import TRXList
+from burst_fwd import trace
from gsm_shared import HoppingParams
@@ -198,6 +199,7 @@ def __init__(self, bind_addr, remote_addr, base_port, **kwargs):
self._tx_queue = []
def __str__(self):
+ return self.name
desc = "%s:%d" % (self.remote_addr, self.base_port)
if self.child_idx > 0:
desc += "/%d" % self.child_idx
@@ -289,6 +291,7 @@ def recv_data_msg(self):
return None
# Enque the message, it will be sent later
+ trace("%s\t-> fn=%d\ttn=%d" % (self, msg.fn, msg.tn))
self.tx_queue_append(msg)
return msg
Change-Id: Icf0b4568b44eb75ee0733391d94b0af86f27ee2e
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