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pespin gerrit-no-reply at lists.osmocom.orgpespin has submitted this change. ( https://gerrit.osmocom.org/c/osmo-bts/+/25443 ) Change subject: TA Control Loop: Change toa256 switch threshold to 75% of a symbol ...................................................................... TA Control Loop: Change toa256 switch threshold to 75% of a symbol As per 3GPP TS 45.010 sec 5.6.3 Delay assessment error: """ the delay shall be assessed in such a way that the assessment error (due to noise and interference) is less than 1/2 normal symbol periods for stationary MS. For MS moving at a speed up to 500 km/h the additional error shall be less than 1/4 normal symbol period. """ Hence, required TA loop calculation should take into account an error of up to 1/2 + 1/4 = 75% of a symbol. By changing the threshold variable to that percentage we make sure we take into account bigger deviations and update TA accordingly. Related: SYS#5371 Change-Id: I4c5825df4291d3851a113027abf7566de343a190 --- M src/common/ta_control.c 1 file changed, 5 insertions(+), 4 deletions(-) Approvals: osmith: Looks good to me, but someone else must approve pespin: Looks good to me, approved Jenkins Builder: Verified diff --git a/src/common/ta_control.c b/src/common/ta_control.c index 6cef545..fd49d60 100644 --- a/src/common/ta_control.c +++ b/src/common/ta_control.c @@ -25,8 +25,9 @@ #include <osmo-bts/gsm_data.h> #include <osmo-bts/logging.h> -/* 90% of one bit duration in 1/256 symbols: 256*0.9 */ -#define TOA256_9OPERCENT 230 +/* 3GPP TS 45.010 sec 5.6.3 Delay assessment error: + * 75% of one bit duration in 1/256 symbols: 256*0.75 */ +#define TOA256_THRESH 192 /* rqd_ta value range */ #define TA_MIN 0 @@ -51,12 +52,12 @@ int16_t delta_ta = toa256/256; if (toa256 >= 0) { - if ((toa256 - (256 * delta_ta)) > TOA256_9OPERCENT) + if ((toa256 - (256 * delta_ta)) > TOA256_THRESH) delta_ta++; if (delta_ta > TA_MAX_INC_STEP) delta_ta = TA_MAX_INC_STEP; } else { - if ((toa256 - (256 * delta_ta)) < -TOA256_9OPERCENT) + if ((toa256 - (256 * delta_ta)) < -TOA256_THRESH) delta_ta--; if (delta_ta < -TA_MAX_DEC_STEP) delta_ta = -TA_MAX_DEC_STEP; -- To view, visit https://gerrit.osmocom.org/c/osmo-bts/+/25443 To unsubscribe, or for help writing mail filters, visit https://gerrit.osmocom.org/settings Gerrit-Project: osmo-bts Gerrit-Branch: master Gerrit-Change-Id: I4c5825df4291d3851a113027abf7566de343a190 Gerrit-Change-Number: 25443 Gerrit-PatchSet: 3 Gerrit-Owner: pespin <pespin at sysmocom.de> Gerrit-Reviewer: Jenkins Builder Gerrit-Reviewer: laforge <laforge at osmocom.org> Gerrit-Reviewer: osmith <osmith at sysmocom.de> Gerrit-Reviewer: pespin <pespin at sysmocom.de> Gerrit-MessageType: merged -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.osmocom.org/pipermail/gerrit-log/attachments/20210914/f7532869/attachment.htm>