English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Near-field communications present new opportunities over near-field channels,however, the spherical wavefront propagation makes near-field signal processingchallenging. In this context, this paper proposes efficient near-field channelestimation methods for wideband MIMO mmWave systems with the aid of extremelylarge-scale reconfigurable intelligent surfaces (XL-RIS). For the widebandsignals reflected by the analog RIS, we characterize their near-field beamsquint effect in both angle and distance domains. Based on the mathematicalanalysis of the near-field beam patterns over all frequencies, a widebandspherical-domain dictionary is constructed by minimizing the coherence of twoarbitrary beams. In light of this, we formulate a two-dimensional compressivesensing problem to recover the channel parameter based on the spherical-domainsparsity of mmWave channels. To this end, we present a correlationcoefficient-based atom matching method within our proposed multi-frequencyparallelizable subspace recovery framework for efficient solutions.Additionally, we propose a two-dimensional oracle estimator as a benchmark andderive its lower bound across all subcarriers. Our findings emphasize thesignificance of system hyperparameters and the sensing matrix of eachsubcarrier in determining the accuracy of the estimation. Finally, numericalresults show that our proposed method achieves considerable performancecompared with the lower bound and has a time complexity linear to the number ofRIS elements.

Near-Field Channel Estimation for Extremely Large-Scale Reconfigurable Intelligent Surface (XL-RIS)-Aided Wideband mmWave Systems