Microcell parameters for ALU B10

Hi Pix,

l_rxqual_dl_h=39 (*0.1)
l_rxqual_ul_h=39 (*0.1)

l_rxlev_dl_h= -97
l_rxlev_ul_h= -97

EN_MCHO_H_UL=enabled EN_MCHO_H_DL=enabled

U_RXLEV_DL_MCHO=-93
U_RXLEV_UL_MCHO=-93

W_LEV_MCHO=1
A_LEV_MCHO=10

a_qual_ho= 4 (SACCH)
a_lev_ho=4 (SACCH)
w_lev_ho= 1

I think by applying MCHO feature, it is not taking into account other parameters, i’ve been looking for an ALU doc but cant find any. Maybe you can help.

BR
Yann

hi ian,

yes, i do know how MCHO work 🙂
so i’m sure we will sort it out !

first thing : whn you activate the MCHO handovers, they do not forbid other type of handovers to take place. They only activate 3 new causes (UL and DL and BAD SACCH) among all the others that already exist.
IMO, the MCHO causes DL and UL are not useful and can be simulated by the typical “low DL” and “low UL” level HO causes.
The cause BAD SACCH is more interesting and is tuned thanks to the parameter N_BAD_SACCH.

1/ Deactivate MCHO DL and MCHO UL.
2/ Apply these default settings;
l_rxqual_dl_h=39 (*0.1)
l_rxqual_ul_h=39 (*0.1)
l_rxlev_dl_h= -93dBm
l_rxlev_ul_h= -101dBm
ho_margin(s,n) = 5dB in both directions
Optimize this setting:
a_pbgt_ho = 12, then 10 then 8 SACCH

do you see any decrease of HO QUALITY ?

What about HO INTERFERENCE ? Is it high ?

Please post some real Qos readings for HO split, HO outgoing preparation sucess rate and HO efficiency rate, idle band measurements of the interference and the “RMS” rxlev_avg, rxqual_avg, timing_advance_avg for each TRX of that cell.

Regards,
pix

hi ian,

ping pong between micro and macro…

micro to macro : those are emergency handovers, so i guess your signal quality in the micro cell is very bad.

macro to micro : those are capture ho, the MS is sent to the micro cell because the rxlev of the microcell is good enough.
what is your setting of L_RXLEV_CPT_HO(macro, micro) ?

The anti ping pong timer is calle T_INHIBIT_CPT. Tune it to a high value in the macro cell (about 40s).It will prevent the capture ho from macro to micro AFTER the MS did a QUALITY HO from micro to macro.

The main issue seems to be bad quality in the microcell, perhaps your capture ho is done too early.
L_RXLEV_CPT_HO(macro, micro) ?
A_PBGT_HO(macro) ?
L_MIN_DWELL_TIME(macro) ?
H_min_dwell_time(macro) ?

Regards,
pix

yes, those settings are correct.
do you see a lot of quality ho in the micro cells ?
regards
pix

ian,

it seems you have a real quality problem in your microcells.
have you checked RMS ?
– rxqual avg
– rxlev avg
– timing advance average
– “s” average (radio link counter)
– UL FER
…

or just by doing a drive test, you’ll see where you’re having a quality issue. have you tried changing frequencies ? deactivate DL power control ? deactivate amr ?
In your situation, the t inhibit will work very well, as i explained earlier… but it is just hidding the problem, not fixing it.

cheers
pix

those are averaging windows, used to average the last “n” SACCH measurement-results.
Those averages are then used for HO decisions (= the raw measurements are useless).

If A_lev_Ho = 4, it means that the value of rxlev used in algorithms is acctually the averages of the past 4 rxlev measuremed.
There is one measurement every 480ms (= 0.5s), so it means that one avg_rxlev is an average of the past 4*0.5 = 2s.
If a_lev_ho is too small, then averages are too ‘jumpy’. HO decisions are made on fake pikes or dives .
If too large, then in front of a criticial loss of signal, the averages will not reflect the problem soon enough. The HO cannot be detected in time.

Best Regards,
pix

hi mannu,

Since when do you have interference in UL ? Since forever ? Or since a specific date ?

When you swapped the two cells, does the problem occur on the same “physical sector” than before, or on the same “logical cell” than before ?

If same physical sector – then you have a HW issue with the micro BTS. Check feeder connection and try to make a full restart of the BTS.

If same logical cell – then you do have a configuration problem, probably due to frequencies. Could you swap frequencies from one cell to the other one?

For each cell :
* What is the HO UL Qual % in each cell ? (busy hour value)

* how much is the TCH erlang BH traffic ?

* how much is the “idle channel interference” ?

* how much is the average timing advance ? (in NPO Indicator family – Radio Measurements -)

Cheers,
pix