Near-Field Channel Estimation for OFDM Extremely Large-Scale Array Systems

The concept of extremely large-scale arrays (XL-arrays) is gaining significant attention for future 6G networks, thanks to their potential to deliver numerous advantages. To fully leverage the capabilities of XL-array systems, accurate channel state information (CSI) is essential. In this context, the near-field effect plays a crucial role. A near-field channel is characterized by both angles and distances, known as polar parameters. In OFDM systems, the channel is also influenced by delays. This paper proposes a channel estimation method that takes advantage of full geometric sparsity within a hybrid combining architecture. We begin by investigating polar sparsity, followed by an examination of delay sparsity. Numerical results demonstrate the effectiveness of the proposed approach.