Evaluation of Coarse-Grained Reconfigurable Array for a Dual Mode OTFS-OFDM Modulator

Orthogonal Time Frequency Space (OTFS) multiplexing, a prospective waveform for 6<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$G$</tex> offers high reliability under high mobility compared to Orthogonal Frequency Division Multiplexing (OFDM), but it is characterized by relatively high computational complexity. To address this challenge, a dual-mode framework has been proposed in the literature that dynamically switches between OFDM and OTFS as needed. However, processing such a computationally intensive workload is not feasible on general-purpose processors and therefore must be accelerated through an Application-Specific Integrated Circuit (ASIC) or a reconfigurable hardware device. A typical form of a reconfigurable hardware is a Coarse-Grained Reconfigurable Array (CGRA). The concept of CGRA has existed for a few decades, but it is still gaining traction due to its massively parallel processing capabilities and run-time reconfigurability. This paper proposes a CGRA-based modulator to meet the run-time switching requirements for a dual-mode OFDM-OTFS system. The CGRA is synthesized on a Stratix-IV FPGA device for prototyping purposes. Operating at a frequency of 181.0 MHz, the CGRA delivers a performance of 11.58 GOPS with a dynamic power dissipation of 308 mW. The proposed architecture is evaluated for multiple OTFS scales <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(8\ \times 4,8\times 8,16\times 16)$</tex> and demonstrates that the proposed solution offers promising results in terms of both performance and scalability.