Wave domain transmitter simplifies multiuser mimo ofdm signals
A Fully Wave-Domain Wideband MU MIMO OFDM Transmitter via Stacked Intelligent Metasurfaces
Hardware Architecture
Summary
Modern wireless signals often use complex digital processing to send data to multiple users simultaneously. This paper shows a way to create these signals using structures called intelligent metasurfaces, working directly with waves instead of traditional digital electronics. The authors split the process into two parts: one that adapts and prepares user data, and another that shapes the final transmitted waveform. Their design reduces reliance on conventional electronics while maintaining good performance, which could lead to simpler and more efficient wireless transmitters.
What this means in practice
- •For wireless hardware engineers: Build baseband-free transmitters that synthesize MU-MIMO OFDM signals directly in the wave domain using stacked metasurfaces for simpler hardware implementation.
- •For telecommunications infrastructure teams: Develop next-generation wideband wireless transmitters that may reduce complexity and improve spectral efficiency by leveraging wave-domain signal processing.
Authors
Zheao Li, Jiancheng An, Chau Yuen
Abstract
This paper proposes an advanced realization principle for wideband multiuser multiple-input multiple-output orthogonal frequency-division multiplexing (MU-MIMO OFDM) transmitters, where the conventional transmitter-side baseband chain is physically synthesized in the wave domain. For design and optimization purposes, this fully wave-domain wideband MU-MIMO OFDM transmitter implemented by a cascaded SIM structure is functionally partitioned into two cascaded SIM blocks. The first block, denoted as SIM_1, integrates symbol loading and channel-adaptive MU-MIMO precoding updated at the channel-coherence timescale, mapping the user streams to a virtual port-subcarrier representation. The second block, denoted as SIM_2, acts as an offline-configured sampling-rate modulator that materializes the inverse discrete Fourier transform (IDFT) and cyclic prefix (CP) insertion directly in the wave domain. This baseband-free architecture establishes a virtual-to-physical transition from information bits to radiated CP-extended OFDM waveforms. To account for practical nonidealities, SIM_2 is optimized to fit the ideal multi-port CP-OFDM operator, and its residual response is mapped into an effective coupling matrix. Then, SIM_1 is optimized in a communication-oriented manner by jointly adapting discrete phase shifts and stream-subcarrier power loading to maximize the sum spectral efficiency. Results demonstrate the convergence, architecture trade-off, wave-domain OFDM materialization accuracy, and competitive performance of the proposed baseband-free transmitter.