I checked the SNR value from: sp->bursts[bidx].snr

This is quite different from: dsp_api.db_r->a_serv_demod[D_SNR]

The dump of the two values is below:

freq_err=97, snr=216. bsnr=104. freq_err=-7, snr=183. bsnr=247. freq_err=19, snr=405. bsnr=16384. freq_err=-10, snr=189. bsnr=16384. freq_err=-163, snr=318. bsnr=16384. freq_err=-27, snr=470. bsnr=16384. freq_err=-23, snr=483. bsnr=16384. freq_err=99, snr=660. bsnr=16384. freq_err=-64, snr=1752. bsnr=16384. SACCH freq_err=-10, snr=476. bsnr=16384. freq_err=-206, snr=476. bsnr=16384. freq_err=-34, snr=326. bsnr=123. freq_err=-256, snr=217. bsnr=250. freq_err=-81, snr=181. bsnr=16384. freq_err=-190, snr=245. bsnr=16384. freq_err=-98, snr=113. bsnr=16384.

What is causing the difference in TCH?

B.

On Wed, Mar 20, 2013 at 9:07 PM, Bhaskar11 niceguy108@gmail.com wrote:

Dear Sylvain,

I'm studying traffic data using ccch_scan in burstind branch.

In prim_sniff.c I track the SNR levels in l1s_sniff_resp() using code from print_tch.c to read snr values from: dsp_api.db_r->a_serv_demod[D_SNR];

I find that the level changes sharply from ccch mode to tch mode.

In ccch mode most of the snr values are 16384. After switching to tch mode they range from 200 to 600 typically!

Is this normal? Am I doing something wrong when changing mode?

Below is the dump of snr values and freq_err during the run.

B.

=============== data dump fnx = fn % 26; freq_err = ANGLE_TO_FREQ(dsp_api.db_r->a_serv_demod[D_ANGLE]); snr = dsp_api.db_r->a_serv_demod[D_SNR];

fnx=6, bidx=0, freq_err=-24, snr=16384. SACCH fnx=7, bidx=0, freq_err=-6, snr=16384. SACCH fnx=8, bidx=0, freq_err=9, snr=16384. SACCH fnx=9, bidx=0, freq_err=-15, snr=16384. SACCH fnx=25, bidx=0, freq_err=-26, snr=16384. fnx=0, bidx=0, freq_err=10, snr=16384. fnx=1, bidx=0, freq_err=38, snr=16384. fnx=2, bidx=0, freq_err=-14, snr=*16384*. fnx=24, bidx=0, freq_err=46, snr=*16384*. fnx=25, bidx=0, freq_err=23, snr=*16384*. fnx=0, bidx=0, freq_err=-1, snr=*16384*. afc_correct(error=-1Hz, arfcn=24): delta=0, afc_dac(old=544,new=544) fnx=1, bidx=0, freq_err=22, snr=16384. *(Immediate Assignment starts here)* L1CTL_FBSB_REQ (arfcn=4, flags=0x7) Starting FCCH RecognitionFB0 (1266881:8): TOA= 8784, Power= -61dBm, Angle=10831Hz afc_correct(error=10831Hz, arfcn=4): delta=1283, afc_dac(old=-700,new=583) FB0 (1266892:9): TOA=10032, Power= -61dBm, Angle= -340Hz afc_correct(error=-340Hz, arfcn=4): delta=-40, afc_dac(old=583,new=543) FB1 (1266902:8): TOA= 8755, Power= -61dBm, Angle= 0Hz afc_correct(error=0Hz, arfcn=4): delta=0, afc_dac(old=543,new=543) fn_offset=1266900 (fn=1266902 + attempt=8 + ntdma = 6) delay=8 (fn_offset=1266900 + 11 - fn=1266902 - 1 scheduling next FB/SB detection task with delay 8 =>FB @ FNR 1266900 fn_offset=1266900 qbits=4836 Synchronize_TDMA LOST 3717! SB1 (2533807:1): TOA= 26, Power= -61dBm, Angle= 176Hz => SB 0x00a9dd65: BSIC=25 fn=1266912(955/10/21)=> DSP reports SB in bit that is 1127709799 bits in the future?!? Synchronize_TDMA => DSP reports FB in bit that is 1127709776 bits in the future?!? LOST 1907! afc_correct(error=4Hz, arfcn=4): delta=0, afc_dac(old=543,new=543) L1CTL_DM_EST_REQ (arfcn=12545, chan_nr=0x15, tsc=1) LOST 3047! *(tch mode is now active)* fnx=4, bidx=0, freq_err=-92, snr=*238*. fnx=6, bidx=0, freq_err=-132, snr=*82*. fnx=8, bidx=0, freq_err=103, snr=*145*. fnx=10, bidx=0, freq_err=-234, snr=*316*. fnx=12, bidx=0, freq_err=-89, snr=*292*. SACCH fnx=13, bidx=0, freq_err=46, snr=*270*. fnx=15, bidx=0, freq_err=35, snr=*387*. fnx=17, bidx=0, freq_err=201, snr=*1055*. fnx=19, bidx=0, freq_err=130, snr=549. fnx=21, bidx=0, freq_err=-94, snr=51. fnx=23, bidx=0, freq_err=-52, snr=173. fnx=0, bidx=0, freq_err=157, snr=322. fnx=2, bidx=0, freq_err=107, snr=95. afc_correct(error=12Hz, arfcn=24): delta=1, afc_dac(old=543,new=544) fnx=4, bidx=0, freq_err=86, snr=135. fnx=6, bidx=0, freq_err=-126, snr=207.

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