MIMO OFDM για ασύρματα συστήματα

Abstract

Τα σηµερινά συστήµατα ασύρµατων επικοινωνιών επιζητούν ολοένα περισσότερο την αξιόπιστη µετάδοση της πληροφορίας και την ταυτόχρονη αύξηση του ρυθµού των δεδοµένων, η οποία µειώνεται εξαιτίας των φαινοµένων του καναλιού, για την παροχή αξιόπιστης ποιότητας υπηρεσιών. Σε αυτή την κατεύθυνση την τελευταία δεκαετία έχουν αναπτυχθεί τα συστήµατα πολλαπλών εισόδων πολλαπλών εξόδων (ΜΙΜΟ), τα οποία αποτελούν σηµαντικότατο πεδίο έρευνας των επικοιν

The current systems of wireless communications seek continuously more for reliable transmission of information and the simultaneous increase of spectral efficiency, which is decreased because of the phenomena of channel, for the benefit of reliable quality of services. In this direction the last decade have been developed the systems of multiple input multiple output (MIMO), which constitute most important field of research of communication systems. The systems in question can offer increase of capacity of communication system (b/s/Hz), via the additional territorial dimension that imports in the existing dimension of time. Nevertheless, the bigger advantages of this method are presented with the use of OFDM. OFDM is a technique that has been developed for a lot of decades, however was not possible to use because of the restrictions of material. After the most important progress of technology in the sector of microelectronics (VLSI) and the reduction of cost that it has today, was given the occasion so that is developed a technique which offers important profits in the spectral efficiency, via the repression of phenomenon of intersymbol interference (ISI). The present technique in combination with the mentioned before technique MIMO, offers important profits in the throughput of modern exigent communication systems. In the present work we study the attribution of system OFDM in environments of white additive noise and intersymbol interference (Awgn, Rayleigh and Rician) via simulation with the environment matlab. After that we simulate a MIMO system and we study the capacity of this system (b/s/Hz) and the influence of antennas in the transmitter and receiver. After we study the diversity and multiplexing gain of a MIMO system. Finally we introduce the results of the simulation, we export the conclusions and we present the advantages using the combination of techniques MIMO – OFDM.