Vadim Yanitskiy has uploaded this change for review. ( https://gerrit.osmocom.org/12181
Change subject: trx_toolkit/burst_fwd.py: document and refactor BurstForwarder ...................................................................... trx_toolkit/burst_fwd.py: document and refactor BurstForwarder Instead of having all configuration variables of BurstForwarder initialized in the class heading, let's introduce two functions for initialization (resetting to defaults) of both UL/DL params. This would allow to reset a BurstForwarder instance from the control interface in follow-up patches. Let's also introduce some basic documentation for the class fields, which were defined in the heading previously. Change-Id: I6b1bf41cf22f01a7e7ecc91c625fb0d2bf4bfeac --- M src/target/trx_toolkit/burst_fwd.py 1 file changed, 117 insertions(+), 39 deletions(-) git pull ssh://gerrit.osmocom.org:29418/osmocom-bb refs/changes/81/12181/1 diff --git a/src/target/trx_toolkit/burst_fwd.py b/src/target/trx_toolkit/burst_fwd.py index 3834849..f3eeddd 100644 --- a/src/target/trx_toolkit/burst_fwd.py +++ b/src/target/trx_toolkit/burst_fwd.py @@ -4,7 +4,7 @@ # TRX Toolkit # BTS <-> BB burst forwarding # -# (C) 2017 by Vadim Yanitskiy <[email protected]> +# (C) 2017-2018 by Vadim Yanitskiy <[email protected]> # # All Rights Reserved # @@ -27,58 +27,136 @@ from data_msg import * class BurstForwarder: - # Timeslot filter (drop everything by default) - ts_pass = None + """ Performs burst forwarding and preprocessing between MS and BTS. - # Freq. filter - bts_freq = None - bb_freq = None + == Pass-filtering parameters - # Randomization of RSSI - randomize_dl_rssi = False - randomize_ul_rssi = False + BurstForwarder may drop or pass an UL/DL burst depending + on the following parameters: - # Randomization of ToA - randomize_dl_toa256 = False - randomize_ul_toa256 = False + - bts_freq / bb_freq - the current BTS / MS frequency + that was set using RXTUNE control command. By default, + both freq. values are set to None, so nothing is being + forwarded (i.e. bursts are getting dropped). - # Timing Advance value indicated by MS (0 by default) - # Valid range: 0..63, where each unit means - # one GSM symbol advance. - ta = 0 + FIXME: currently, we don't care about TXTUNE command + and transmit frequencies. It would be great to distinguish + between RX and TX frequencies for both BTS and MS. - # Timing of Arrival values indicated by transceiver - # in units of 1/256 of GSM symbol periods. A pair of - # base and threshold values defines a range of ToA value - # randomization: from (base - threshold) to (base + threshold). - toa256_dl_base = 0 - toa256_ul_base = 0 + - ts_pass - currently active timeslot, configured by the MS. + It can be activated or deactivated using SETSLOT control + command from the MS. - toa256_dl_threshold = 128 - toa256_ul_threshold = 128 + FIXME: only a single timeslot can be activated! + FIXME: there is no such list for the BTS side. - # RSSI values indicated by transceiver in dBm. - # A pair of base and threshold values defines a range of RSSI - # randomization: from (base - threshold) to (base + threshold). - rssi_dl_base = -60 - rssi_ul_base = -70 + == Preprocessing and measurement simulation - rssi_dl_threshold = 10 - rssi_ul_threshold = 5 + Since this is a virtual environment, we can simulate different + parameters of a virtual RF interface: - # Path loss simulation: DL/UL burst dropping - # Indicates how many bursts should be dropped - # and which dropping period is used. By default, - # period is 1, i.e. every burst (fn % 1 is always 0) - burst_dl_drop_amount = 0 - burst_ul_drop_amount = 0 - burst_dl_drop_period = 1 - burst_ul_drop_period = 1 + - ToA (Timing of Arrival) - measured difference between expected + and actual time of burst arrival in units of 1/256 of GSM symbol + periods. A pair of both base and threshold values defines a range + of ToA value randomization: + + DL: from (toa256_dl_base - toa256_dl_threshold) + to (toa256_dl_base + toa256_dl_threshold), + UL: from (toa256_ul_base - toa256_ul_threshold) + to (toa256_ul_base + toa256_ul_threshold). + + - RSSI (Received Signal Strength Indication) - measured "power" of + the signal (per burst) in dBm. A pair of both base and threshold + values defines a range of RSSI value randomization: + + DL: from (rssi_dl_base - rssi_dl_threshold) + to (rssi_dl_base + rssi_dl_threshold), + UL: from (rssi_ul_base - rssi_ul_threshold) + to (rssi_ul_base + rssi_ul_threshold). + + Please note that the randomization of both RSSI and ToA + is optional, and should be enabled manually. + + === Timing Advance handling + + The BTS is using ToA measurements for UL bursts in order to calculate + Timing Advance value, that is then indicated to a MS, which in its turn + shall apply this value to the transmitted signal in order to compensate + the delay. Basically, every burst is transmitted in advance defined by + the indicated Timing Advance value. The valid range is 0..63, where + each unit means one GSM symbol advance. The actual Timing Advance value + is set using SETTA control command from MS. By default, it's set to 0. + + === Path loss simulation - burst dropping + + In some cases, e.g. due to a weak signal or high interference, a burst + can be lost, i.e. not detected by the receiver. This can also be + simulated using FAKE_DROP command on both control interfaces: + + - burst_{dl|ul}_drop_amount - the amount of DL/UL bursts + to be dropped (i.e. not forwarded towards the MS/BTS), + + - burst_{dl|ul}_drop_period - drop every X DL/UL burst, e.g. + 1 - drop every consequent burst, 2 - drop every second burst, etc. + + """ def __init__(self, bts_link, bb_link): self.bts_link = bts_link self.bb_link = bb_link + # Randomization of RSSI + randomize_dl_rssi = False + randomize_ul_rssi = False + + # Randomization of ToA + randomize_dl_toa256 = False + randomize_ul_toa256 = False + + # Init default parameters + self.reset_dl() + self.reset_ul() + + # Initialize (or reset to) default parameters for Downlink + def reset_dl(self): + # Unset current DL freq. + self.bts_freq = None + + # Indicated RSSI / ToA values + self.toa256_dl_base = 0 + self.rssi_dl_base = -60 + + # RSSI / ToA randomization threshold + self.toa256_dl_threshold = 0 + self.rssi_dl_threshold = 0 + + # Path loss simulation (burst dropping) + self.burst_dl_drop_amount = 0 + self.burst_dl_drop_period = 1 + + # Initialize (or reset to) default parameters for Uplink + def reset_ul(self): + # Unset current DL freq. + self.bb_freq = None + + # Indicated RSSI / ToA values + self.rssi_ul_base = -70 + self.toa256_ul_base = 0 + + # RSSI / ToA randomization threshold + self.toa256_ul_threshold = 0 + self.rssi_ul_threshold = 0 + + # Path loss simulation (burst dropping) + self.burst_ul_drop_amount = 0 + self.burst_ul_drop_period = 1 + + # Init timeslot filter (drop everything by default) + self.ts_pass = None + + # Reset Timing Advance value + self.ta = 0 + # Converts TA value from symbols to # units of 1/256 of GSM symbol periods def calc_ta256(self): -- To view, visit https://gerrit.osmocom.org/12181 To unsubscribe, or for help writing mail filters, visit https://gerrit.osmocom.org/settings Gerrit-Project: osmocom-bb Gerrit-Branch: master Gerrit-MessageType: newchange Gerrit-Change-Id: I6b1bf41cf22f01a7e7ecc91c625fb0d2bf4bfeac Gerrit-Change-Number: 12181 Gerrit-PatchSet: 1 Gerrit-Owner: Vadim Yanitskiy <[email protected]>
