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Υλοποίηση τεχνικών ευφυών ραδιοφώνων με OFDM σε SDR πλατφόρμες USRP N200 και εφαρμογή σε ένα γνωστικό ραδιο-δίκτυο

Giolias Athanasios

Πλήρης Εγγραφή


URI: http://purl.tuc.gr/dl/dias/8779C324-0752-4ABB-8364-A8510850C093
Έτος 2015
Τύπος Διπλωματική Εργασία
Άδεια Χρήσης
Λεπτομέρειες
Εμφανίζεται στις Συλλογές

Περίληψη

Orthogonal Frequency Division Multiplexing or (OFDM) is a modulation format that is being used for many of the latest wireless and telecommunications standards.OFDM has been adopted in the Wi-Fi arena at standards like 802.11a, 802.11n, 802.11ac and more. It has also been chosen for the cellular telecommunications standard LTE / LTE-A and, in addition, it has been adopted by other standards such as WiMAX and many more. The combination of high data capacity, high spectral efficiency, and its resilience to intersymbol interference as a result of multi-path effects means that it is ideal for the high data applications that have become a major factor in today's communications scene. Since OFDM has gained a significant presence in the wireless market place, it is very interesting to examine it thoroughly and acquire a great amount of knowledge in this area of telecommunications.Firstly, the purpose of this thesis is to provide an experimental study of an OFDM implementation by utilizing the Ettus UHD drivers in C++, USRPs N200 and several math libraries. The initial prototyping takes place in Matlab and after thorough testing the code is converted into the corresponding C++ code that will be able to handle the incoming/outcoming OFDM packets' processing in realtime. Afterwards, the transmitter-receiver set will be pushed to its limits in order to examine the existence and estimation of a frequency selective channel instead of a flat fading channel.Secondly, we have the creation and study of a time slotted protocol with a master transmitter(Primary User - PU) and a slave transceiver(Secondary User - SU) that acts as a cognitive radio. The SU after spectrum sensing transmits packets when the PU is idle, in order to keep all time-slots occupied. Next, this application is modified so that the users can transmit a binary image and a receiver processes the incoming parts. The processing of all the packets is done in realtime and provides us with the received image of each user in the end of his transmission.

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