Hi,
Is there a function in OpenBSC that can help in estimating the diastase of the connected phone ? For example, something that gives the value of the power received by the phone from the BTS and the power received by the BTS from the phone (during paging or active call).
best regards,
On 02/11/16 13:01, sami wrote:
Hi,
Is there a function in OpenBSC that can help in estimating the diastase of the connected phone ? For example, something that gives the value of the power received by the phone from the BTS and the power received by the BTS from the phone (during paging or active call).
best regards,
Hi sami. You can see those uplink and downlink power levels with 'show lchan' in OpenBSC. For example:
Measurement Report: Flags: L1 MS Power: 33 dBm, Timing Advance: 9 RXL-FULL-dl: -86 dBm, RXL-SUB-dl: -87 dBm RXQ-FULL-dl: 0, RXQ-SUB-dl: 0 RXL-FULL-ul: -87 dBm, RXL-SUB-ul: -47 dBm RXQ-FULL-ul: 0, RXQ-SUB-ul: 0
There you will also see "Timing Advance" although I'm not sure how exactly to interpret that. Maybe somebody else might comment. I'm also not sure what RXQ is, although I've seen those numbers increase when I use very low power levels in osmotrx and move the MS away from the USRP, so I presume it's an indicator of RF errors? I'll take the opportunity to also ask for clarification on that :)
Hi Keith,
Thanks for your help, I will try it !
Best regards, Sami,
On Nov 2, 2016, at 9:07 PM, Keith Whyte keith@rhizomatica.org wrote:
On 02/11/16 13:01, sami wrote:
Hi,
Is there a function in OpenBSC that can help in estimating the diastase of the connected phone ? For example, something that gives the value of the power received by the phone from the BTS and the power received by the BTS from the phone (during paging or active call).
best regards,
Hi sami. You can see those uplink and downlink power levels with 'show lchan' in OpenBSC. For example:
Measurement Report: Flags: L1 MS Power: 33 dBm, Timing Advance: 9 RXL-FULL-dl: -86 dBm, RXL-SUB-dl: -87 dBm RXQ-FULL-dl: 0, RXQ-SUB-dl: 0 RXL-FULL-ul: -87 dBm, RXL-SUB-ul: -47 dBm RXQ-FULL-ul: 0, RXQ-SUB-ul: 0
There you will also see "Timing Advance" although I'm not sure how exactly to interpret that. Maybe somebody else might comment. I'm also not sure what RXQ is, although I've seen those numbers increase when I use very low power levels in osmotrx and move the MS away from the USRP, so I presume it's an indicator of RF errors? I'll take the opportunity to also ask for clarification on that :)
Regarding TA: it's very approximate measure of distance:
1) it's not yet implemented the way it should - see https://projects.osmocom.org/issues/1545 for example
2) Increase in TA +1 approximately equals to increase of +550 meters distance between phone and BS (1 bit period = 3.69 usec times speed of light)
3) There's guard period (8.25 for normal bursts) between transmissions which allows it not to overlap with next one so even the phone with incorrect TA might still work with BTS to some extend.
On 11/02/2016 08:07 PM, Keith Whyte wrote:
On 02/11/16 13:01, sami wrote:
Hi,
Is there a function in OpenBSC that can help in estimating the diastase of the connected phone ? For example, something that gives the value of the power received by the phone from the BTS and the power received by the BTS from the phone (during paging or active call).
best regards,
Hi sami. You can see those uplink and downlink power levels with 'show lchan' in OpenBSC. For example:
Measurement Report: Flags: L1 MS Power: 33 dBm, Timing Advance: 9 RXL-FULL-dl: -86 dBm, RXL-SUB-dl: -87 dBm RXQ-FULL-dl: 0, RXQ-SUB-dl: 0 RXL-FULL-ul: -87 dBm, RXL-SUB-ul: -47 dBm RXQ-FULL-ul: 0, RXQ-SUB-ul: 0
There you will also see "Timing Advance" although I'm not sure how exactly to interpret that. Maybe somebody else might comment. I'm also not sure what RXQ is, although I've seen those numbers increase when I use very low power levels in osmotrx and move the MS away from the USRP, so I presume it's an indicator of RF errors? I'll take the opportunity to also ask for clarification on that :)
On 03/11/2016 14:57, Keith wrote:
Would you also be able to clarify RXL-FULL/SUB and the RXQ-FULL/SUB figures?
I looked at the source and did some research, in case anyone (who didn't know already) is interested, the L is Level and the Q is Quality.
RXL-SUB is the measurement when DTX (*Discontinuous Transmission)* is enabled, (abbr. of subset) RXL-FULL is otherwise i.e when there is voice activity.
That's very much of a tl;dr, but there's plenty of info on it out there.
Yes, you're right.
RXL (RXLEV) is [0..63] which codes signal level (0 is weakest) RXQ (RXQUAL) is [0..7] which codes BER (Bit Error Rate) level (0 is least errors)
So RXLEV measures the radio signal quality (how much interference our signal suffered) while RXQUAL measures errors in decoded signal (how much useful info we've managed to extract from signal). Both are estimation of how good is the radio link between MS and BTS using different definition of what "good" is.
And -FULL and -SUB just defines when those measurements are done by MS (in case of DTX there are periods of no transmission so there's nothing to measure).
Overall, this is even worse way to estimate distance than TA - MS standing next to powerful electric motor with lots of of EM leak in the vicinity of BTS will get worse RX* measurements than MS which is far away but in nice clean EM environment.
See 3GPP TS 45.008 for lots of details.
Overall, for getting the distance (as well as actual position) we got RRLP protocol which I think is the way to go for location data.
On 11/03/2016 06:45 PM, Keith wrote:
On 03/11/2016 14:57, Keith wrote:
Would you also be able to clarify RXL-FULL/SUB and the RXQ-FULL/SUB figures?
I looked at the source and did some research, in case anyone (who didn't know already) is interested, the L is Level and the Q is Quality.
RXL-SUB is the measurement when DTX (*Discontinuous Transmission)* is enabled, (abbr. of subset) RXL-FULL is otherwise i.e when there is voice activity.
That's very much of a tl;dr, but there's plenty of info on it out there.
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Keith -
Keith Whyte
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Max -
sami