Change in osmo-ttcn3-hacks[master]: bts: Add timing offset tolerance module parameter to support real HW

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Pau Espin Pedrol gerrit-no-reply at lists.osmocom.org
Fri Sep 28 18:16:52 UTC 2018


Pau Espin Pedrol has posted comments on this change. ( https://gerrit.osmocom.org/11083 )

Change subject: bts: Add timing offset tolerance module parameter to support real HW
......................................................................


Patch Set 5:

(2 comments)

https://gerrit.osmocom.org/#/c/11083/5/bts/BTS_Tests.ttcn
File bts/BTS_Tests.ttcn:

https://gerrit.osmocom.org/#/c/11083/5/bts/BTS_Tests.ttcn@1285
PS5, Line 1285: 		actual_ta := f_tolerance(l1p.ms_actual_ta, 0, 63, mp_tolerance_timing_offset_256syms/256)
According to "3GPP TS 48.058", "9.3.10 L1 Information":
"""
Octets 2-3 contain the L1 header information of SACCH blocks. The information fields and codings are as defined in 
3GPP TS 44.004. 
"""

Then. According to "3GPP TS 44.004", "6.1  Physical layer protocol fields and procedures:"

"""
For all the bands except GSM 400, the values 0 to 63 are valid TA values.  The bit pattern "1111111" indicates that the 
field does not contain a timing advance value. All other bit combinations (64 to 126 decimal) are reserved. For all bands 
except GSM 400 bit 8 is set to spare.
"""

So this one is good.


https://gerrit.osmocom.org/#/c/11083/5/bts/BTS_Tests.ttcn@1288
PS5, Line 1288: 	var template uint8_t t_toffs := f_tolerance(offs, -63, 192, mp_tolerance_timing_offset_256syms/256);
> I think I swapped these values with those of line 1285, I need to have a look at these ranges again.
According to "3GPP TS 48.058", "9.3.37 MS Timing Offset":
"""
The meaning of the MS Timing Offset is as defined in 3GPP TS 45.010. The value of MS Timing Offset is the binary 
value of the 8-bit Timing Offset field (octet 2) - 63. The range of MS Timing Offset is therefore -63 to 192. 
"""

And looking for "Timing Offset" in TS 45.010 I could only find this:
"""
MS timing offset:
 delay of the received signal relative to the expect
ed signal from an MS at zero distance under static 
channel conditions with zero timing advance. This is accurate to ± 1 symbol, and reported once per SACCH or after a 
RACH as. required (i.e. at the same rate as timing advan
ce). For example, for an MS with a round trip propagation 
delay of P symbols, but with a timing advance of T symbols, the reported timing offset will be P-T quantized to the 
nearest symbol. For GPRS the MS timing offset is not reported. 
"""

So, as a result:
line 1264 should have ranges (-63*256, 192*256).
line 1285 should have ranges (0,63) (correct in current version).
line 1288 should have ranges (0, 255).



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Gerrit-Project: osmo-ttcn3-hacks
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: Icf1d2216d29c1ebf68c672e6ca06c54a7457304b
Gerrit-Change-Number: 11083
Gerrit-PatchSet: 5
Gerrit-Owner: Pau Espin Pedrol <pespin at sysmocom.de>
Gerrit-Reviewer: Harald Welte <laforge at gnumonks.org>
Gerrit-Reviewer: Jenkins Builder (1000002)
Gerrit-Reviewer: Pau Espin Pedrol <pespin at sysmocom.de>
Gerrit-Reviewer: Vadim Yanitskiy <axilirator at gmail.com>
Gerrit-Comment-Date: Fri, 28 Sep 2018 18:16:52 +0000
Gerrit-HasComments: Yes
Gerrit-HasLabels: No
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