Tag Archives: GSM

GSM Amplifier

2014-12-12 manatails Leave a comment

The High Power Amplifier for my Tactical GSM network has arrived, it almost took 2 weeks to get it delivered.
I bought the amplifier from Israel. Although it is manufactured in Korea.

It gives 42db avarage gain and allows up to 10 watts of transmit power.

Also it is noticable that it has d-sub 3w3 power connector.
I intended to buy a proper connector for the cabling but I gave up, I am going to rely on coils and and duct tapes

But it consumes near 300w of electricity at max, so I had to buy a separate power supply for it.

It isn’t easy to come by a 27v power supply but I was lucky enough to find one.

Radio

LTE EARFCN에 대해

2014-12-12 manatails Leave a comment

블로그 로그를 보다가 LTE eARFCN이란 키워드로 방문하시는 분이 많은 것 같아 간단히 글을 남깁니다.

GSM 같은 셀룰러 네트에서 와이파이의 채널과 같은 의미를 가진것이 ARFCN입니다
Absolute Radio Frequency Channel Number 의 약자죠.
기지국과 휴대폰이 통신을 할 때 쓰는 업링크와 다운링크 채널을 정해 놓은 것입니다.

인접한 셀들끼리 비슷한 채널을 이용해 신호를 송출하면 혼선이 일어나기때문에 각 섹터마다 기지국은 다른 ARFCN을 이용해서 서비스를 하게 됩니다.

이것이
GSM과 같은 2G 망에서는 ARFCN으로
UMTS와 같은 3G 망에서는 U-ARFCN으로
LTE와 같은 4G 망에서는 E-ARFCN으로 불리는 것입니다.

Radio

GSM frequency bands

2014-12-10 manatails Leave a comment

Band	Downlink (MHz)			Bandwidth (MHz)	Uplink (MHz)			Chanel number Arfcn	Duplex spacing (MHz)
Band	Low	Middle	High	Bandwidth (MHz)	Low	Middle	High	Chanel number Arfcn	Duplex spacing (MHz)
GSM 850	869.2	881.5	893.8	24.6	824.2	836.5	848.8	128 – 251	45
GSM 900	935.2	947.5	959.8	24.6	890.2	902.5	914.8	1 – 124	45
DCS 1800	1805.2	1842.5	1879.8	74.6	1710.2	1747.5	1784.8	512 – 885	95
PCS 1900	1930.2	1960	1989.8	59.6	1850.2	1880	1909.8	512 – 810	80

GSM frequency band table for reference

Phone - See 'Radio' for more

Converting MP3/WAV to ulaw/GSM

2014-10-23 manatails 2 Comments

When you want to convert typical MP3/WAV files for your PBX like Asterisk, you can use sox and lame to do it easily.

lame --decode somemp3file.mp3 output.wav
First, convert the MP3 to WAV file.

Then,
For u-law:
sox -V output.wav -r 8000 -c 1 -t ul result.ulaw

For GSM:
sox output.wav -r 8000 -c 1 result.gsm resample -ql

Pre-converting your input sound files usually give much better results than using internal modules for transcoding.

Radio

SGSN temporary MCC/MNC authentication hack

2014-09-10 manatails Leave a comment

From gprs_gmm.c


                        char mccmnc[16];
                        snprintf(mccmnc, sizeof(mccmnc), "%03d%02d", ra_id.mcc, ra_id.mnc);
                        if (strncmp(mccmnc, mi_string, 5) &&
                            (sgsn->cfg.acl_enabled &&
                             !sgsn_acl_lookup(mi_string))) {
                                LOGP(DMM, LOGL_INFO, "Rejecting ATTACH REQUESET IMSI=%s\n",
                                     mi_string);
                                return gsm48_tx_gmm_att_rej_oldmsg(msg,
                                                                GMM_CAUSE_GPRS_NOTALLOWED);
                        }

It needs to be commented out to allow roaming IMSIs to receive PDP contexts

Computer

nanoBTS reset procedure

2013-12-20 manatails 1 Comment

This tutorial is for those who need to reset their nanoBTS units for redeployment.

Originally each nanoBTS unit comes with a little reset dongle. But the dongle isn’t very special – it is just a proprietary connector with pins 9-10 connected to each other.

A screwdriver can do the exactly same thing, all you need to do is to short out pins 9 and 10 of the TIB-IN connector.
The TIB connectors of nanoBTS are a modified RJ69 connector. Refer to the following image for pin locations:

You need to short out the rightmost two pins of the plug.

Video tutorial for 165 series

Video tutorial for 110 series

Disclaimer : This tutorial is not sponsored nor endorsed by ip.access and I am not in anyway associated with ip.access. Please do not contact me for sales inquiry.

Computer