An Analysis of Spectral Beamforming and Angular OFDMA for THz Communications

In this paper, we analyze orthogonal frequency-division multiple access (OFDMA) based on the concept of THzPrism, which is a spectral beamforming technique particularly suited for THz communications. The basic principle of the THzPrism is to replace the phase shifters in antenna arrays used for conventional beamforming by delay elements. As a result, the spectral components of the radiated signal are transmitted in different directions. Using OFDMA along with this type of spectral beamforming leads to a multiple access scheme, where the subcarriers point in different directions, and the OFDMA signal covers the intended angular sector while providing a significant beamforming gain. The basic properties and the performance of this recently introduced technique are still very little investigated in the technical literature. In this paper, focusing on the downlink, we analyze the interference between the OFDMA subcarriers that is created by the spectral beamforming, and we assess the resulting bit error rate performance degradation for different values of the system parameters. Our analysis gives a clear insight into system design and achievable performance.