Sistem za zajem in analizo radijskih tekstovnih sporočil

Legan, David (author), Umek, Anton (mentor)

Glavni cilj diplomske naloge je izdelava sistema za zajem RDS sporočil, ki jih oddajajo radijske postaje na UKW področju. Praktična izvedba sistema temelji na univerzalnem programirljivem sprejemniku SDR. SDR ali software-defined radio je lahko radijski sprejemnik in/ali oddajnik. V primerjavi s strojnimi radio sprejemniki, katere uporabljamo v domačem okolju, se signali obdelujejo v procesorju, njegove komponente pa so izdelane programsko. Od tod tudi ime programirljivi radio. SDR se uporablja predvsem za eksperimentalne namene, pa tudi v mobilnih omrežjih in vojaških komunikacijah. Cenovna dostopnost SDR radio sprejemnika se izkazuje po vse večji razširjenosti uporabe za različna področja kognitivnega radia. Zmogljivost sprejemanje signalov se giblje približno v območju frekvenčnega pasa od 20 MHz pa vse do 2200 MHz. Vsebuje osnovne gradnike za pretvorbo zajetega radio signala v primerno obliko za nadaljnjo obdelavo. Sprejemnik sestavljata dve glavni integrirani vezji. Prvo vezje vsebuje elemente, ki spremeni neposredni analogni signal. Spreminjanje poteka tako, da premakne frekvenčni pas z namenom, da je ta primeren za nadaljnji prenos sporočila in bolj prilagodljiv za moteče pojave na prenosni poti. Drugo vezje poskrbi, da se prenesen fizikalni signal ali sporočilo pretvori v različne oblike. Sporočilo je lahko zapisano s simboli (črke, številke ali binarni simboli v računalniškem zapisu). V prenosnem kanalu, kjer se prenašajo taki simboli (niz števil ali »digiti«), se zato tak prenos imenuje digitalni prenos. To je glavna komponenta drugega vezja, saj vsebuje napravo, ki pretvori analogni v digitalni signal. Njegovo delovanje je bilo raziskano s pomočjo eksperimentov. Raziskal sem tri primere eksperimentov za različna področja uporabe. Delo je bilo v celoti opravljeno samo pri dveh, kajti zaradi omejene dostopnosti in lokacije mi pri zadnjem ni uspelo. Uspešno sem sprejel in prebral radio RDS sporočila s strani radio oddajnih postaj. Zajel sem pa tudi komunikacijo letalskega prometa z različnimi programskimi orodji. S pomočjo SDR spremenljivega radia sem raziskal še delovanje tako imenovane aplikacije POCSAG, s katero sem poizkušal sprejeti radio signal. Gre za informativne bazne postaje, ki vsebujejo pozivnike. Njihov namen je obveščanje o nevarnostih v neposrednem času. Zajem RDS sporočil sem preveril z več različnimi programskimi orodji. Eden izmed najpreprostejših za uporabo je SDR#, ki deluje zgolj v Windows okolju. Potrebno je nastaviti želeno frekvenčno območje postaje ter način sprejemanja radio signala. V našem primeru sem uporabil širokopasovni FM na UKW področju radijskih frekvenc. Raziskal sem še programsko orodje GNU Radio, operativno v Linux okolju. Linux okolje sem uporabil preko USB pomnilnika, na katerem sem namestil navidezno sliko Linux okolja. To mi je omogočilo, da sem se izognil dolgotrajnemu namestitvenemu procesu. V primerjavi s SDR# orodjem se je pokazal za učinkovitejšega, vendar zahtevnejšega za uporabo. Programsko okolje GNU radio omogoča mnogo več kot SDR#, hkrati pa zahteva tudi več znanja in daljše učenje za uspešno uporabo SDR sprejemnika. Vsi bolj izobraženi uporabniki si lahko sami ustvarijo simulacijsko okolje in pogoje, kjer preizkušajo delovanje različnih radio sistemov. Kot zadnjo orodje, ki sem ga kasneje uporabil za naš eksperimentalni sistem za zajem RDS sporočil, sem uporabil programsko orodje REDSEA. Tudi ta deluje v Linux okolju. Za zajem in analizo RDS sporočil sem moral poleg programskega orodja REDSEA uporabiti še tri dodatna. Prvi, ki sem ga uporabil, je programski jezik PYTHON. Z njim sem ustvaril programsko kodo, ki mi je omogočala povezavo in prenos RDS sporočil v primerno podatkovno obliko. Zajeta sporočila, ki jih zajamemo s programskim orodjem READSEA, ni mogoče neposredno uporabiti za analizo, ker vsebujejo dodatne znake. S programskim orodjem PHYTON zato upravljamo aplikacijo READSEA in ustrezno filtriramo sporočila za prenos v podatkovno bazo. Podatkovna baza SQLite3 mi je omogočila pretvorbo prenesenih RDS sporočil v ustrezen format podatkov. Te pa sem lahko prenesel na zadnje programsko orodje, s katerim sem napravil analizo podatkov. To je programsko orodje Microsoft Excel. Kot nalogo za analizo RDS sporočil sem izbral merjenje ponovljivosti skladb in informativnih sporočil. S pomočjo ročnih poizvedb v programu Excel sem pridobil statistične podatke o ponovljivosti skladb. Analiza zajetih podatkov je pokazala, kako pogosto se ponavljajo skladbe določenih radio postaj in koliko časa je za to namenjenega, in sicer v primerjavi z celotnim radijskim programom.

• Language: Slovenian
• Keywords: RDS, SDR, RTL-SDR, REDSEA, PYTHON, SQLite3
• Work type: Bachelor thesis/paper
• Organization: FE - Faculty of Electrical Engineering
• Year: 2017
• PID: 20.500.12556/RUL-93035
• Publication date in RUL: 17.07.2017

Secondary language

• Language: English
• Title: A system for capturing and analyzing RDS messages

Abstract

The main goal of the diploma thesis is to create a system able to capture RDS messages, which are broadcast by radio stations on the UKW field. The practical implementation of the system is based on a universal software SDR receiver. An SDR or a software-defined radio can be a radio receiver and/or a transmitter. If compared to hardware radio receivers, which we use in a domestic environment, the signals are processed in a processor and its components are made by a software. That is the reason why it is called a software defined radio. An SDR is mainly used for experimental purposes as well as in mobile networks and military communications. The price accessibility of an SDR radio receiver is the reason why its usage is rapidly increasing in different fields of a cognitive radio. Its capacity of receiving signals is ranging from 20 MHz to 2200 MHz of the frequency zone. It contains basic elements for conversing the captured radio signal into a suitable form for further processing work. A receiver is composed by two integrated circuits. The first circuit contains elements which modify a direct analogue signal. The modification is performed in the following way: the frequency zone is moved in order to be suitable for a further transmission of the message and also more adaptable to disturbing factors which may occur on the transportable way. The second circuit takes care that a transferable physical signal or the message is converted into different forms. The message can be written with symbols (letters, numbers or binary symbols in the machinery notation). In a transmissible channel, where such symbols are transmitted (a set of numbers or »digits«), the transmission is called a digital transfer. That is the main component of the second circuit since it contains a device which converts an analogue to a digital signal. Its operation was researched by means of experiments. I studied three cases of experiments for different fields of use. The work was completed in only two cases, in the last one I was not successful because of a limited accessibility and location. I successfully received and read the radio RDS messages sent by radio stations. I also captured the communication of an aircraft traffic with different types of software tools. By means of an SDR defined radio I also researched the operation of a so-called POCSAG application with which I was trying to receive a radio signal. These are informative base stations which contain pagers. Their purpose is to inform about the dangers in the real time. I checked captured RDS messages with many different types of software tools. The one with the easiest usage is the SDR# which only works in the Windows system. It is necessary to set the desired frequency band of a radio station and a method of the receiving a signal. In our case I used the FM wideband zone on the UKW field of radio frequencies. I also researched the GNU Radio programme which operates in the Linux system. The Linux system was used through the USB drive on which I installed a virtual image of the Linux system. It enabled me to avoid a long lasting installing process. Comparing to the SDR# tool it proves to be more effective but also more difficult to be used. The programme environment of the GNU radio enables much more than SDR#, but at the same time it also requires more knowledge and a longer study for a successful usage of an SDR receiver. More educated users can create a simulating environment and conditions by themselves in which they test the operation of different radio systems. The last tool which I used later on for our experimental system to capture RDS messages was the software tool REDSEA. It also operates in the Linux system. Besides the REDSEA software for capturing and analysing the RDS messages I also had to use three additional software tools. The first one which I used is the PYTHON programme language. With this tool I created the programme code which enabled me to connection and transfer the RDS messages into a suitable data form. Messages which are captured with the REDSEA tool cannot be directly used for the analysis because they contain certain additional symbols. With the PYTHON tool accordingly we manage the application REDSEA in order to appropriately filter the messages for their transmission into a database. SQLite3 database enabled me to convert the received RDS messages into a suitable data format. These messages could be consequently transferred into the last software tool from which I made the analysis of the data. This is the Microsoft Excel tool. As a task for the analysis of the RDS messages, I chose monitoring the repetition of the songs and other informative messages. By means of manual inquiries in the Excel program, I acquired statistical data about the repetition of the songs. The analysis of the captured data revealed how often the songs are repeated by the selected radio stations and how much time is meant for that purpose comparing it to the entire radio programme.

• Keywords: RDS, SDR, RTL-SDR, REDSEA, PYTHON, SQLite3