Difference between revisions of "OpenBTS: Kalibrasi"
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Revision as of 07:43, 3 March 2012
Sumber: http://gnuradio.org/redmine/wiki/1/OpenBTSClockCalibration
Jika kita tidak mempunyai peralatan lab yang baik dan kita ingin mengetahui akurasi clock USRP, kita dapat menggunakan aplikasi Kalibrator (Copyright (c) 2009 Joshua Lackey, Alexander Chemeris). Tentunya kita tidak mungkin memperoleh hasil yang baik seperti hi-tech lab, tapi cukup lah untuk mengetahui error kalibrasi clock yang ada.
Latest version of Kalibrator today is 0.2 and is available here. Starting from the next update of OpenBTS Kalibrator will be distributed as a part of OpenBTS standard package.
How it works¶
Kalibrator takes advantage of the existing real networks and their accuracy. So you need to be in range within some operator's BTS. You pass the downlink frequency of the previously scanned ARFCN as a command line parameter for Kalibrator. Using some math Kalibrator can estimate the value of frequency difference between the frequency it tunes USRP to and the frequency of a BTS working in +-200kHz range near that frequency.
Building and running¶
To build Kalibrator with gnuradio 3.2.2 (ver. 3.1.3 is not currently supported) run 'make' and you will get binary file 'kal' which is ready for use.
Now you need to know which ARFCN is better to use. With any GPRS modem supporting AT commands it is possible to find an ARFCN with the strongest signal. Without such modem, you have to scan whole band by manual iteration through downlink frequencies (it can be inconvenient especially on 1800/1900 band). Search this file for specific downlinks all_gsm_channels_arfcn.txt.
Suitable channels must have at least -70 to -80dBm strenght, else you got to much overruns and the result could be misguiding. That's just good to have more channels to scan to eliminate possible wrong error. There is an example of network scan from GPRS modem (offset values are added manually).
T-Mobile operator ================= at^moni Serving Cell I Dedicated channel chann rs dBm MCC MNC LAC cell NCC BCC PWR RXLev C1 I chann TS timAdv PWR dBm Q ChMod offset 58 53 -57 230 01 4358 719D 2 4 33 -106 48 I Limited Service -2197 Hz OK
at^monp chann rs dBm MCC MNC BCC C1 C2 offset 106 45 -65 230 01 7 40 40 -2507 Hz 75 37 -73 230 01 2 32 32 -2367 Hz 28 21 -89 230 01 4 16 16 N/A 80 17 -93 230 01 1 12 12 N/A
OK
Telefonica O2 operator ====================== at^moni Serving Cell Z I Dedicated channel chann rs dBm MCC MNC LAC cell NCC BCC PWR RXLev C1 I chann TS timAdv PWR dBm Q ChMod offset 86 59 -51 230 02 04BC 090B 1 3 33 -106 54 I Limited Service -2496 Hz
OK at^monp chann rs dBm MCC MNC BCC C1 C2 offset 114 47 -63 230 02 4 42 42 N/A 112 30 -80 230 02 7 25 25 N/A 93 19 -91 230 02 7 14 14 N/A
OK
Here is obvious how the values were obtained.
[openBTS@openBTS kal-0.2]# ./kal -f 946600000 -u USRP side: B FPGA clock: 52000000 Decimation: 192 Antenna: RX2 Sample rate: 270833.343750 average [min, max] (range, stddev) -2197.789062 [-2431, -1843] (588, 146.761444) overruns: 0 not found: 0
[openBTS@openBTS kal-0.2]# ./kal -f 956200000 -u USRP side: B FPGA clock: 52000000 Decimation: 192 Antenna: RX2 Sample rate: 270833.343750 average [min, max] (range, stddev) -2507.531006 [-2575, -2436] (139, 40.815132) overruns: 0 not found: 0
[openBTS@openBTS kal-0.2]# ./kal -f 950000000 -u USRP side: B FPGA clock: 52000000 Decimation: 192 Antenna: RX2 Sample rate: 270833.343750 average [min, max] (range, stddev) -2367.053467 [-2431, -2275] (156, 43.972340) overruns: 0 not found: 0
[openBTS@openBTS kal-0.2]# ./kal -f 952200000 -u USRP side: B FPGA clock: 52000000 Decimation: 192 Antenna: RX2 Sample rate: 270833.343750 average [min, max] (range, stddev) -2496.760254 [-2592, -2375] (217, 61.745182) overruns: 0 not found: 0
By default RX and side are set to ones used by OpenBTS, so usually you need only one mandatory parameter '-f'. You can use -u is optional parameter for continous display.
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Download
Download dari
http://thre.at/kalibrate/kal-v0.4.1.tar.bz2
Compile
cp kal-v0.4.1.tar.bz2 /usr/local/src/ cd /usr/local/src tar jxvf kal-v0.4.1.tar.bz2 cd /usr/local/src/kal-v0.4.1 ./bootstrap && CXXFLAGS='-W -Wall -O3' ./configure && make
Menjalankan
cd /usr/local/src/kal-v0.4.1/src/ ./kal -h
Hasil
kalibrate v0.4.1, Copyright (c) 2010, Joshua Lackey Usage: GSM Base Station Scan: kal <-s band indicator> [options] Clock Offset Calculation: kal <-f frequency | -c channel> [options] Where options are: -s band to scan (GSM850, GSM900, EGSM, DCS, PCS) -f frequency of nearby GSM base station -c channel of nearby GSM base station -b band indicator (GSM850, GSM900, EGSM, DCS, PCS) -R side A (0) or B (1), defaults to B -A antenna TX/RX (0) or RX2 (1), defaults to RX2 -g gain as % of range, defaults to 45% -F FPGA master clock frequency, defaults to 52MHz -v verbose -D enable debug messages -h help
Scanning 1800
Menjalankan
./kal -s 1800 -F 64
Hasil
kal: Scanning for DCS-1800 base stations. DCS-1800:
Scanning 900
Menjalankan
./kal -s 900
Hasil
kal: Scanning for GSM-900 base stations. GSM-900:
Scanning 850
Menjalankan
./kal -s 850
Hasil
kal: Scanning for GSM-850 base stations. GSM-850:
chan: 128 (869.2MHz - 13Hz) power: 9400.80 chan: 131 (869.8MHz + 7Hz) power: 4081.75 chan: 139 (871.4MHz + 10Hz) power: 2936.20 chan: 145 (872.6MHz - 7Hz) power: 33605.48
Scanning Channel
Menjalankan
./kal -c 145
Hasil
kal: Calculating clock frequency offset. Using GSM-850 channel 145 (872.6MHz) average [min, max] (range, stddev) - 1Hz [-8, 7] (14, 3.948722) overruns: 0 not found: 0
Referensi
- http://gnuradio.org/redmine/wiki/1/OpenBTSClockCalibration
- http://sourceforge.net/mailarchive/attachment.php?list_name=openbts-discuss&message_id=3d032e5d0911101431o5bb31844mdfe80ae4fc9789ea@mail.gmail.com&counter=1
- http://thre.at/kalibrate/
- http://thre.at/kalibrate/#install
- http://ttsou.github.com/kalibrate-uhd/
- https://github.com/ttsou/kalibrate-uhd
Pranala Menarik
Persiapan
- USRP: High Precision Clock
- USRP: Menyambungkan ClockTamer ke USRP1
- USRP: Instalasi Board
- OpenBTS: GIT Source Code
OpenBTS 2.6
- GNURadio
- GNURadio: Ubuntu Install
- GNURadio: Ubuntu Install GNURadio 3.4.2
- GNURadio: Contoh Aplikasi
- GNURadio: Spectrum Analizer GSM
- GNURadio: Mengubah board RFX1800 menjadi RFX900
- GNURadio: Programming Untuk Pemula
- OpenBTS: Ubuntu Install
- OpenBTS: Konfigurasi
- OpenBTS: Kalibrasi
- OpenBTS: Konfigurasi Asterisk untuk OpenBTS
- OpenBTS: Menjalankan smqueue
- OpenBTS: Mengoperasikan BTS
- OpenBTS: Tampilan di Nokia saat pakai OpenBTS
- OpenBTS: Operasi 1800 MHz
- OpenBTS: Beberapa Tips
- OpenBTS: USRP2
- OpenBTS: Amplifier
- OpenBTS: SMS
- AirProbe
OpenBTS 2.8
- GNURadio: Ubuntu 11.10 Install *NOT RECOMMENED*
- GNURadio: Ubuntu 11.10 instalasi menggunakan Repo NOT RECOMMENDED
- GNURadio: Ubuntu 11.10 Instal GNURadio 3.3.0
- GNURadio: Ubuntu 11.10 Instal GNURadio 3.4.2
- GNURadio: Ubuntu 11.10 Install dari GIT GNURadio
- OpenBTS: Ubuntu 11.10 Install
- OpenBTS: 2.8 dari SVN Install RECOMMENDED
- OpenBTS: 2.8 Instalasi Real Time Asterisk
- OpenBTS: 2.8 Konfigurasi
- OpenBTS: Database SQLite
Ettus E110
- OpenBTS: E110 Cara Login
- OpenBTS: E110 Install Image di MicroSD
- OpenBTS: E110 Cek Daughter Board
- OpenBTS: E110 Mengubah Master Clock
- OpenBTS: E110 Bekerja dengan opkg
- OpenBTS: E110 GNURadio
- OpenBTS: E110 Instalasi OpenBTS
- OpenBTS: E110 Instalasi OpenBTS 2.6 *NOT RECOMMENDED*
Lain Lain
- Membuat Base Station GSM Open Source
- Teknologi Selular
- GSM: Daftar Channel Frekuensi
- Wireless Internet
- OpenBSC
- AirProbe
- Base station subsystem
- GSM
- Asterisk
- Mobile phone
Catatan Legal dan Pendukung
- Siapa Bilang OpenBTS Ilegal?
- OpenBTS: Catatan MNC dan MCC Indonesia
- OpenBTS : Alokasi Frekuensi Operator GSM Indonesia