General

In this research project the method of multicarrier transmission is to be implemented and tested in practice.  The best-known multicarrier method is Orthogonal Frequency Division Multiplexing (OFDM) and is used in many current standards such as LTE, WLAN, 5G, to name only the most important ones.
OFDM is very powerful with long echo runtimes of the signals, easy to implement by means of FFT, but it also has some serious disadvantages. Among these are the moderate spectral efficiency and the high demands on the linearity of the transmitter.
These disadvantages lead to an out-of-band radiation, which can interfere with adjacent channels. To reduce this out-of-band radiation, variants of OFDM have been proposed in the literature which are known as Filter Bank Modulation Carriers (FBMC).

OFDM

Orthogonal Frequency-Division Multiplexing is a Multi-Carrier Modulation Method. It is widely used in Applications such as DVB-T, 4G, Wifi, and Powerline Networks. The transmitted data is split up into many small carriers. Each of these carriers is then modulated with a modulation method such as QPSK, QAM or BPSK.
 After allocating all the carriers and adding sync-words in front of the frame, the transmission signal is generated through an IFFT. The IFFT takes all the Channels of one OFDM Symbol and generates a time-signal. Through calculating the IFFT it is secured that every carrier is orthogonal to the others.
After that the last third of the samples of the signal are copied to the front of the signal. This is called cyclic prefix. The cyclic Prefix ensures, that the FFT can be used to equalize the transmission signal.