Report on final THz Baseband Algorithms and Phased Array Beam Forming ready for real-time implementation

Work package (WP) 5 of TERRANOVA investigates and develops the concepts of THz modems, frontends and antennas, and the interface to embed them into different fibre optic links. Several different interesting system architecture candidates were proposed in the course of this project, at high-level as part of the deliverable D2.2 (“TERRANOVA System Architecture”) and in more detail at component level in D5.1 (“Report on preliminary THz RF-Frontend and Antenna, Phased Array Beamforming, Baseband Algorithms and Optical RF-Frontend Ready for Implementation in Offline Tests”). However, those ideas were, so far, not validated in a realistic system simulation environment with experimentally derived and verified models.
One of the critical milestones of TERRANOVA is the proof-of-concept of the analog hybrid optical-THz wireless communication system. In this concept, there is no baseband digital signal processing (DSP) at the interface between the optical fibre and the THz wireless frontend – for this reason categorized as an analog hybrid link. All baseband DSP is shifted to the optical end, which has to take care of the complete joint optical-THz wireless link and the corrections of its imperfections. The vision of TERRANOVA is that the available optical PHY DSP algorithms can be still used or modified derivations of them. The evaluation of the system performance and the identification of potential bottlenecks is vital for the success of the experimental high capacity demonstrator in WP6. A step-by-step procedure was implemented and results are presented in this deliverable. In a first step, measurements and simulations of the stand-alone THz wireless link are compared to establish a verified simulation model of the wireless link. In the next step, the same is done for the coherent optical and the IM/DD optical links. The individual simulation models are for this reason experimentally validated. In the last step, the combination of both, the optical and the THz wireless links, is investigated.
Another important aspect of TERRANOVA is the evaluation of beamforming (BF) algorithms at THz frequencies. The experimental demonstration in WP6 has several shortcomings related to the very limited number of antenna elements that can be actually implemented. In addition, the demonstrator suffers from uncorrelated phase noise and thermal drift. The assessment of the practical limitations by realistic simulation models is important before the real-time implementation of the BF algorithms. In this context, the robustness of the codeword selection and SNR maximization-based BF approach must be further validated, before the real-time implementation in a modem can start. Related to the limited number of RF channels and antenna elements, the discrete lens array (DLA) antenna concept was identified as a very interesting concept in WP3 to overcome the problem. At THz frequencies, the size of such a solution becomes 10x smaller than for example at 28 GHz, which is attractive for commercial solutions. A first feasibility study towards an experimental demonstration helps at an early stage for planning in WP6 and the assessment of the implementation risks associated to such a solution. Fixed and mobile scenarios would benefit from channel estimation schemes, which could be used for compensation of multi-path related problems. Before starting the implementation of such algorithms, it is important to evaluate the implementation complexity and their robustness.
You can find the PDF here: TERRANOVA D5.2