Analysis of Quadrature Amplitude Modulation under Rayleigh Fading Channel

Da bi se omogućio razvoj mobilnog komuniciranja, potrebno je povećavati prijenosnu brzinu u bežičnim mrežama s obzirom na zahtjevne usluge i velik broj korisnika. Jedno od rješenja je korištenje naprednih modulacijskih teknika, kao što je kvadraturna diskretna modulacija amplitude. Posebno ograničenje u modeliranju mobilnih sustava jesu velike smetnje kojima bežični kanal utječe na signal u transmisiji. Najveće smetnje nastaju djelovanjem Rayleighijevog fedinga. Zbog toga je nužno koristiti modulacijsku tehniku koja osim dobre spektralne efikasnosti ima i dobru otpornost na smetnje. Tema ovog rada je analiza performansi QAM modulacije na kanalima s Rayleighijevim fedingom. Motivacija rada jest pronaći dobar kompromis između spektralne efikasnosti, snage odašiljanja i greški koje nastaju pri prijenosu. U radu su prikazani rezultati testiranja utjecaja AWGN šuma i Rayleighijeva fedinga, i to: utjecaj na konstelacijske dijagrame QAM modulacija, utjecaj na grešku bita i grešku simbola. Također, teoretski su objašnjeni AWGN kanal, kanal s Rayleighijevim fedingom, kapaciteti navedenih kanala, osnove digitalnih modulacija i QAM modulacija.In order to facilitate the development of mobile communication, it's necessary to increase the transmission speed in wireless networks due to the demanding services and a large number of users. One solution is the use of advanced modulation technique, such as the discrete quadrature amplitude modulation. Important limitation on modeling mobile systems are great distortions affecting the signal in transmission. Rayleigh fading causes biggest distortions. It is therefore necessary to use a modulation technique that besides good spectral efficiency has good resistance to distortions. The theme of this thesis is to analyze the performance of QAM modulation in Rayleigh fading channels. It's motivation is to find a good compromise between spectral efficiency, power transmission and errors that occur during transmission. The thesis presents the results of testing the influence of AWGN noise and Rayleigh fading, including: the impact on the QAM modulation constellation diagrams, the impact on the bit error rate and symol error rate. Also, it includes theoretically explaination of the AWGN channel, the Rayleigh fading channel, the capacity of the these channels, the basics of digital modulation and QAM modulation