Harald Welte has submitted this change and it was merged.

Change subject: fake_trx: handle SETTA (Timing Advance) indicated by MS
......................................................................


fake_trx: handle SETTA (Timing Advance) indicated by MS

Timing Advance value is a timing correction value, indicated by
the network to MS, which is used to compensate UL signal delay.
In other words, the network instructs a phone to transmit bursts
N=TA symbol periods earlier than expected.

Since we are in virtual environment, let's use TA value to
calculate the ToA (Timing of Arrival) value for BTS.

Change-Id: Ie5833a9f221587bbcac10f0b223ead9c1cbda72b
---
M src/target/fake_trx/burst_fwd.py
M src/target/fake_trx/ctrl_if_bb.py
2 files changed, 33 insertions(+), 0 deletions(-)

Approvals:
  Harald Welte: Looks good to me, approved
  Jenkins Builder: Verified



diff --git a/src/target/fake_trx/burst_fwd.py b/src/target/fake_trx/burst_fwd.py
index 4a0e9bb..bcf2257 100644
--- a/src/target/fake_trx/burst_fwd.py
+++ b/src/target/fake_trx/burst_fwd.py
@@ -34,6 +34,11 @@
        bts_freq = None
        bb_freq = None
 
+       # Timing Advance value indicated by MS (0 by default)
+       # Valid range: 0..63, where each unit means
+       # one GSM symbol advance.
+       ta = 0
+
        # Constants
        # TODO: add options to change this
        RSSI_RAND_TRESHOLD = 10
@@ -56,6 +61,17 @@
                # Generate a random ToA range
                self.toa256_min = self.TOA256_RAND_BASE - 
self.TOA256_RAND_TRESHOLD
                self.toa256_max = self.TOA256_RAND_BASE + 
self.TOA256_RAND_TRESHOLD
+
+       # Calculates ToA value for Uplink bursts (coming to a BTS)
+       def calc_toa_ul(self):
+               # Generate a random ToA value
+               toa256 = random.randint(self.toa256_min, self.toa256_max)
+
+               # Apply TA value
+               ta256 = self.ta * 256
+               toa256 -= ta256
+
+               return toa256
 
        # Converts a L12TRX message to TRX2L1 message
        def transform_msg(self, msg_raw):
@@ -128,6 +144,9 @@
                if msg is None:
                        return None
 
+               # Emulate ToA value for BTS
+               msg.toa256 = self.calc_toa_ul()
+
                # Validate and generate the payload
                payload = msg.gen_msg()
 
diff --git a/src/target/fake_trx/ctrl_if_bb.py 
b/src/target/fake_trx/ctrl_if_bb.py
index 47c7048..74fb242 100644
--- a/src/target/fake_trx/ctrl_if_bb.py
+++ b/src/target/fake_trx/ctrl_if_bb.py
@@ -115,6 +115,20 @@
 
                        return 0
 
+               # Timing Advance
+               elif self.verify_cmd(request, "SETTA", 1):
+                       print("[i] Recv SETTA cmd")
+
+                       # Parse and check TA value
+                       ta = int(request[1])
+                       if ta < 0 or ta > 63:
+                               print("[!] TA value should be in range: 0..63")
+                               return -1
+
+                       # Save to the BurstForwarder instance
+                       self.burst_fwd.ta = ta
+                       return 0
+
                # Wrong / unknown command
                else:
                        # We don't care about other commands,

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Gerrit-MessageType: merged
Gerrit-Change-Id: Ie5833a9f221587bbcac10f0b223ead9c1cbda72b
Gerrit-PatchSet: 1
Gerrit-Project: osmocom-bb
Gerrit-Branch: fixeria/trx
Gerrit-Owner: Vadim Yanitskiy <axilira...@gmail.com>
Gerrit-Reviewer: Harald Welte <lafo...@gnumonks.org>
Gerrit-Reviewer: Jenkins Builder

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