Recently the need for a new cellular communications standard is increasing due to the limitations of the 4G standard. Several modulation techniques have been proposed for the 5G standard, and filter bank multicarrier (FBMC) is one of them. Orthogonal frequency-division multiplexing (OFDM), which is used for the 4G standard, has relatively poor out-of-band emission performance. Offset QAM-FBMC has good out-of-band emission performance, but there is a difficulty in utilizing algorithms developed for the conventional multiple-input, multiple-output (MIMO) system. QAM-FBMC is recently proposed to solve both of these problems. QAM-FBMC has a trade-off relationship between its spectrum confinement and self-interference. However, only simulations on the BER performance and tests on the robustness to phase noise of a QAM-FBMC system are recently reported.
In this paper, prototype filters are designed for QAM-FBMC and their performance is compared with the waveform of OFDM. In particular, the QAM-FBMC prototype filters are designed that maximize signal-to-interference ratio (SIR) subject to an out-of-band emission constraint. Both computer simulations and hardware experiments are conducted using the designed QAM-FBMC filters to compare the frequency characteristics of the QAM-FBMC signals with those of OFDM without cyclic prefix (CP). The experiments employ an arbitrary waveform generator to generate the QAM-FBMC and OFDM signals at intermediate frequencies. Both the simulations and the experiments show that an OFDM subcarrier has large sidelobes whereas a QAM-FBMC subcarrier does not, which results in better out-of-band emission performance for the QAM-FBMC than the OFDM. This is consistent with the theoretical frequency characteristics of the QAM-FBMC and the OFDM. Thus, the QAM-FBMC can achieve a smaller out-of-band emission and, consequently, a smaller interference, and a better spectral efficiency.
The last chapter of this thesis describes how the hardware experiment is conducted by using a GaGe’s CompuGen waveform generator. It covers detailed specifications of the CompuGen hardware, how to install and use required software, how to control the hardware using the software, and some implementation examples.