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Cellular re-broadcast over satellite

I've recently attended a seminar that (among other topics) also covered RF interference hunting. The speaker was talking about various real-world cases of RF interference and illustrating them in detail.

Of course everyone who has any interest in RF or cellular will know about fundamental issues of radio frequency interference. To the biggest part, you have

cells of the same operator interfering with each other due to too frequent frequency re-use, adjacent channel interference, etc.

cells of different operators interfering with each other due to intermodulation products and the like

cells interfering with cable TV, terrestrial TV

DECT interfering with cells

cells or microwave links interfering with SAT-TV reception

all types...

LaForge's home page
Posted at 2017-02-15 23:00:00 | Electronics | read on

Towards a real SIGTRAN/SS7 stack in libosmo-sigtran

In the good old days ever since the late 1980ies - and a surprising amount even still today - telecom signaling traffic is still carried over circuit-switched SS7 with its TDM lines as physical layer, and not an IP/Ethernet based transport.

When Holger first created OsmoBSC, the BSC-only version of OpenBSC some 7-8 years ago, he needed to implement a minimal subset of SCCP wrapped in TCP called SCCP Lite. This was due to the simple fact that the MSC to which it should operate implemented this non-standard protocol stacking that was developed + deployed before the IETF SIGTRAN WG specified M3UA or SUA came around. But...

LaForge's home page
Posted at 2017-02-12 23:00:00 | Electronics | read on

Testing (not only) telecom protocols

When implementing any kind of communication protocol, one always dreams of some existing test suite that one can simply run against the implementation to check if it performs correct in at least those use cases that matter to the given application.

Of course in the real world, there rarely are protocols where this is true. If test specifications exist at all, they are often just very abstract texts for human consumption that you as the reader should implement yourself.

For some (by far not all) of the protocols found in cellular networks, every so often I have seen some formal/abstract machine-parseable test specifications. Sometimes it was TTCN-2, and...

LaForge's home page
Posted at 2017-02-11 23:00:00 | Electronics | read on

FOSDEM 2017

Last weekend I had the pleasure of attending FOSDEM 2017. For many years, it is probably the most exciting event exclusively on Free Software to attend every year.

My personal highlights (next to meeting plenty of old and new friends) in terms of the talks were:

20 Years of Linux Virtual Memory by MM-Guru Andrea Arcangeli

GPU-Enabled Polyphase Filterbanks by Jan Kraemer

Virtual multi-antenna arrays for estimating the bearing of radio transmitters by Francois Quitin

Secure Microkernel for Deeply Embedded Devices by Jim "jserv" Huang

A discussion of Fedora's Legal state by Tom Callaway

Radio Lockdown Directive by Max Mehl

I was attending but not so excited by Georg...

LaForge's home page
Posted at 2017-02-10 23:00:00 | Electronics | read on

Free Stuff, January–June 2016

It's been a while since we've posted, but yes, we are still giving away free stuff! Even though we can't respond to each and every email, we do read and carefully consider all of them, and we choose at least one awesome group, project, or individual each month to send some free hardware to. Here are the free stuff recipients for the first half of 2016.

ADS-B Out Open Source Project

We gave a HackRF One to developer and pilot Christopher Young, whose latest development project is an in-flight ADS-B Out transponder. ADS-B Out allows pilots to broadcast position, ground speed, and...

Great Scott Gadgets
Posted at 2017-02-09 23:21:00 | Electronics | read on

Реверс-инжиниринг лазерного сканера Leuze RS4


Ранее я уже рассказывал о реверс-инжиниринге лазерного датчика расстояния. В этот раз речь пойдет о более сложном устройстве — лазерном сканере Leuze RS4. Как и датчик, этот сканер попал ко мне в сломанном состоянии, так что пришлось заняться восстановлением его работы, и в процессе улучшить некоторые его характеристики, и, фактически, переделать его в другое устройство.
Читать дальше →

[iliasam]
Posted at 2017-02-01 07:00:09 | Electronics | read on

Osmocom Conference 2017 on April 21st

I'm very happy that in 2017, we will have the first ever technical conference on the Osmocom cellular infrastructure projects.

For many years, we have had a small, invitation only event by Osmocom developers for Osmocom developers called OsmoDevCon. This was fine for the early years of Osmocom, but during the last few years it became apparent that we also need a public event for our many users. Those range from commercial cellular operators to community based efforts like Rhizomatica, and of course include the many research/lab type users with whom we started.

So now we'll have the public OsmoCon on April 21st, back-to-back with the invitation-only OsmoDevcon...

LaForge's home page
Posted at 2017-01-31 23:00:00 | Electronics | read on

Mounting computers on wooden boards

Putting a Pentium 4 rig, power supply and all, on piece of plywood for easy hanging.

Halestrom.net
Posted at 2017-01-26 08:33:41 | Electronics | read on

Autodesk: How to lose loyal EAGLE customers

A few days ago, Autodesk has announecd that the popular EAGLE electronics design automation (EDA) software is moving to a subscription based model.

When previously you paid once for a license and could use that version/license as long as you wanted, there now is a monthly subscription fee. Once you stop paying, you loose the right to use the software. Welcome to the brave new world.

I have remotely observed this subscription model as a general trend in the proprietary software universe. So far it hasn't affected me at all, as the only two proprietary applications I use on a regular basis during the last decade are...

LaForge's home page
Posted at 2017-01-22 23:00:00 | Electronics | read on

33C3 talk on dissecting cellular modems

Yesterday, together with Holger 'zecke' Freyther, I co-presented at 33C3 about Dissectiong modern (3G/4G) cellular modems.

This presentation covers some of our recent explorations into a specific type of 3G/4G cellular modems, which next to the regular modem/baseband processor also contain a Cortex-A5 core that (unexpectedly) runs Linux.

We want to use such modems for building self-contained M2M devices that run the entire application inside the modem itself, without any external needs except electrical power, SIM card and antenna.

Next to that, they also pose an ideal platform for testing the Osmocom network-side projects for running GSM, GPRS, EDGE, UMTS and HSPA cellular networks.

You can find the Slides and the Video...

LaForge's home page
Posted at 2016-12-30 00:00:00 | Electronics | read on
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Однажды китайский ученый Ли Хунь Янь обнаружил некоторую незначительную, однако, существенно отличающуюся от фона корреляцию между количеством псилоцибина потребляемого корфуцианскими медузами и характером передвижения оных по стенкам четырехсотлитровго шарообразного аквариума, установленного в лаборатории по случаю празднования сто второго полугодичного затмения от начала новой эры Сингулярного Прорыва. Недолго думая, Ли Хунь Янь приделал к щупальцам медуз источники излучения в видимом диапазоне но с разной длинной волны, заснял весь процесс шестью камерами с 48 часовой выдержкой, симметрично расставив последние вокруг сосуда, где резвились подопытные и через неделю собрал прелюбопытнейший материал, который, в свою очередь, лег в основу фундаментального труда, ныне известного, как теория полутретичных n-многообразий простой метрики Ли Хунь Янь, с которой (с некоторыми упрощениями и оговорками) я, по мере сил, постараюсь познакомить любопытного и пытливого читателя.

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