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Development of communication systems *

A hub about all that concerns the development of communication systems

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APRS. AFSK modulator from Flipper Zero

Level of difficulty Medium
Reading time 7 min
Views 4K

There is such an interesting data transfer protocol - APRS. A lot has already been told about him on the Internet. There will be no in-depth theoretical material here. This article will describe how to create your own "pocket" AFSK modulator. In the following articles there will be instructions for going on the air and for creating a simple demodulator. Which will allow you to accept APRS packages and display information on the display right on the street. Everything will be implemented for Flipper Zero. If you don't have this gadget yet, then don't worry and try everything on the great and terrible Arduino. It is very interesting to transmit information at a distance "with your own hands".

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Total votes 3: ↑3 and ↓0 +3
Comments 2

Does GPS transmit different data into LNAV and CNAV messages?

Reading time 2 min
Views 2K

Different navigation message protocols are used for different navigation signal type. This is true even for a single system like NAVSTAR GPS. For example, L1C/A signals have a LNAV protocol, while L2C and L5 signals utilize a CNAV protocol. The newest L1C signal will use CNAV-2. 

The protocol defines a data distribution into frames, subframes, the subframes structure, transmission intervals, data resolution and so on. 

A navigation receiver use the navigation message data flow for several purposes:

1. The data flow allows to resolve a code ambiguity and set the signal time.

2. Ephemeris and clock values are used for the satellite position calculation, pseudorange corrections and coordinates computation.

3. The received data flow and navigation message data can be used for navigation symbols prediction. As result, we can use the wipe-off technique, expand discriminators and significantly increase tracking sensitivity:

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Total votes 3: ↑3 and ↓0 +3
Comments 0

The benefits of offering VoIP to your customers under your own brand

Reading time 3 min
Views 1.8K

The potential of VoIP to your customers is simply phenomenal. Businesses are experiencing the advantages of VoIP’s cost-efficiency and reliability and now you can pass these benefits onto your own customers very easily. Cloud telecommunication is sophisticated and easily integrated. Confidence in this technology is growing fast. There has never been a better time to start talking to your customers about adopting this solution. It will deliver huge business benefits for them and has the potential to increase business income and profitability.

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Total votes 4: ↑4 and ↓0 +4
Comments 0

REST hooks for WebRTC Click to Call. Implementation experience

Reading time 6 min
Views 2.1K

The "Click to Call" button on the website is an "innovation" that has been around for about 10 years. The technologies under the hood have changed, but the principle remains the same: someone clicks on the button on the site page, then JavaScript launches and requests access to the microphone and establishes a connection to the server — WebRTC SIP gateway. Further, the first client-server leg is a browser gateway, the second leg can be arbitrarily long and through the SIP proxy chain can eventually connect to a mobile or landline phone. Thus, the browser turns, in a sense, into a softphone and becomes a full participant in VoIP telephony.

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Working with light: Starting your career at ITMO University

Reading time 4 min
Views 1.4K
One of our previous articles featured an overview of our photonics department students’ work lives. Today we’re going to expand on this topic by looking at four related MA programs: “Light Guide Photonics and Programmable Electronics”, “LED technologies and optoelectronics”, “Photonic materials” and “Laser technologies”. We sat down with some of the folks currently enrolled in these programs, as well as recent graduates, to talk about the role ITMO University played in kickstarting their careers.

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Total votes 5: ↑5 and ↓0 +5
Comments 0

Simple and free video conferencing

Reading time 3 min
Views 2.4K
Due to a rapid increase in remote work, we have decided to offer video conferencing. Like most of our services, it is free of charge. It is built on a reliable open-source solution, it is mostly based on WebRTC, which allows communicating in the browser by just clicking on a link. Below we’ll tell you more about its features and some of the problems we’ve run into.


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Total votes 2: ↑2 and ↓0 +2
Comments 5

Even more secret Telegrams

Reading time 6 min
Views 4.8K

We used to think of Telegram as a reliable and secure transmission medium for messages of any sort. But under the hood it has a rather common combination of a- and symmetric encryptions. Where’s fun in that? And why would anyone trust their private messages to a third-party anyway?
Spy vs Spy by Antonio Prohías
TL;DR — inventing a private covert channel through users blacklisting each other.

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Total votes 12: ↑8 and ↓4 +4
Comments 0

Info desk: global Internet initiatives

Reading time 6 min
Views 1.3K


Fiber-optic cables are a great way to bring high-speed Internet right to your home or office. But even in large cities not everyone can enjoy the benefits of it, since apartments far away from everyone, or low-population districts far from downtown, are very reluctantly served by ISPs.

And then there’s small towns and villages, far away from the main Internet “highways”. In poorer countries, Internet is often slow and expensive even in large population centers, while villages are often left without a connection for years. To connect them to the World Wide Web takes the resources of not just normal ISPs, but telecom giants. Solar-powered drones with networking equipment, weather balloons, satellites and other similar projects are not just science fiction, but a reality today (or in the near future). But who’s closer to launch and who’s lagging behind? Let’s find out.
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Total votes 7: ↑6 and ↓1 +5
Comments 1

Russian Internet Segment Architecture

Reading time 8 min
Views 4.8K
As many of our readers know, Qrator.Radar is constantly researching global BGP connectivity, as well as regional. Since the Internet stands for “Interconnected Networks,” to ensure the best possible quality and speed the interconnectivity of individual networks should be rich and diverse, with their growth motivated on a sound competitive basis.

The fault-resistance of an internet connection in any given region or country is tied to the number of alternate routes between ASes. Though, as we stated before in our Internet Segments Reliability reports, some paths are obviously more critical compared to the others (for example, the paths to the Tier-1 transit ISPs or autonomous systems hosting authoritative DNS servers), which means that having as many reachable routes as possible is the only viable way to ensure adequate system scalability, stability and robustness.

This time, we are going to have a closer look at the Russian Federation internet segment. There are reasons to keep an eye on that segment: according to the numbers provided by the RIPE database, there are 6183 autonomous systems in Russia, out of 88664 registered worldwide, which stands for 6.87% of total.

This percentage puts Russia on a second place in the world, right after the USA (30.08% of registered ASes) and before Brazil, owning 6.34% of all autonomous systems. Effects of changes in the Russian connectivity could be observed across many other countries dependant on or adjacent to that connectivity, and ultimately by almost any ISP in the world.
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Total votes 35: ↑34 and ↓1 +33
Comments 1

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