ReQuestNet: A Foundational Learning model for Channel Estimation

--In this paper, we present a novel neural architecture for channel estimation (CE) in 5G and beyond, the Recurrent Equivariant UERS Estimation Network (ReQuestNet). It incorporates several practical considerations in wireless communication systems, such as ability to handle variable number of resource block (RB), dynamic number of transmit layers, physical resource block groups (PRGs) bundling size (BS), demodulation reference signal (DMRS) patterns with a single unified model, thereby, drastically simplifying the CE pipeline. Besides it addresses several limitations of the legacy linear MMSE solutions, for example, by being independent of other reference signals and particularly by jointly processing MIMO layers and differently precoded channels with unknown precoding at the receiver . ReQuestNet comprises of two sub-units, CoarseNet followed by RefinementNet. CoarseNet performs per PRG, per transmit-receive (Tx-Rx) stream channel estimation, while Refinement-Net refines the CoarseNet channel estimate by incorporating correlations across differently precoded PRGs, and correlation across multiple input multiple output (MIMO) channel spatial dimensions (cross-MIMO). Simulation results demonstrate that ReQuestNet significantly outperforms genie minimum mean squared error (MMSE) CE across a wide range of channel conditions, delay-Doppler profiles, achieving up to 10dB gain at high SNRs. Notably, ReQuestNet generalizes effectively to unseen channel profiles, efficiently exploiting inter-PRG and cross-MIMO correlations under dynamic PRG BS and varying transmit layer allocations. The advent of 5G NR and the anticipated evolution toward sixth-generation (6G) networks have ushered in an era of unprecedented connectivity, data throughput, and system complexity. These developments necessitate advanced techniques for low-power, compute-efficient, and reliable wireless communication. Orthogonal Frequency Division Multiplexing (OFDM), a foundational modulation scheme in 5G NR, creates parallel communication channels across a large time-frequency grid. To acquire channel state information (CSI), the pilot signals known as demodulation reference signal (DMRS) is used, whose time-frequency positions and values are known a priori to both transmitter and receiver. Work completed while affiliated with Qualcomm Technologies Inc., USA.