eprintid: 10204643 rev_number: 7 eprint_status: archive userid: 699 dir: disk0/10/20/46/43 datestamp: 2025-02-12 13:41:24 lastmod: 2025-02-12 13:41:24 status_changed: 2025-02-12 13:41:24 type: article metadata_visibility: show sword_depositor: 699 creators_name: Zhu, Z creators_name: Wang, L creators_name: Wang, X creators_name: Wang, D creators_name: Wong, KK title: Spatial-spectral Cell-free Sub-terahertz Networks: A Large-scale Case Study ispublished: inpress divisions: UCL divisions: B04 divisions: F46 keywords: Millimeter wave communication, Massive MIMO, Leaky wave antennas, Resource management, Phased arrays, Terahertz communications, Radio spectrum management, Downlink, Couplings, Channel estimation note: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions. abstract: This paper studies the large-scale cell-free networks where dense distributed access points (APs) serve many users. As a promising next-generation network architecture, cell-free networks enable ultra-reliable connections and minimal fading/blockage, which are much favorable to the millimeter wave and terahertz transmissions. However, conventional beam management with large phased arrays in a cell is very time-consuming in the higher-frequencies, and could be worsened when deploying a large number of coordinated APs in the cell-free systems. To tackle this challenge, the spatial-spectral cell-free networks with the leaky-wave antennas are established by coupling the propagation angles with frequencies. The beam training overhead in this direction can be significantly reduced through exploiting such spatial-spectral coupling effects. In the considered large-scale spatial-spectral cell-free networks, a novel subchannel allocation solution at sub-terahertz bands is proposed by leveraging the relationship between cross-entropy method and mixture model. Since initial access and AP clustering play a key role in achieving scalable large-scale cell-free networks, a hierarchical AP clustering solution is proposed to make the joint initial access and cluster formation, which is adaptive and has no need to initialize the number of AP clusters. After AP clustering, a subchannel allocation solution is devised to manage the interference between AP clusters. Numerical results are presented to confirm the efficiency of the proposed solutions and indicate that besides subchannel allocation, AP clustering can also have a big impact on the large-scale cell-free network performance at sub-terahertz bands. date: 2025-01-16 date_type: published publisher: Institute of Electrical and Electronics Engineers (IEEE) official_url: https://doi.org/10.1109/twc.2025.3526932 oa_status: green full_text_type: other language: eng primo: open primo_central: open_green verified: verified_manual elements_id: 2357867 doi: 10.1109/TWC.2025.3526932 lyricists_name: Wong, Kai-Kit lyricists_id: KWONG98 actors_name: Wong, Kai-Kit actors_id: KWONG98 actors_role: owner full_text_status: public publication: IEEE Transactions on Wireless Communications pagerange: 1-1 issn: 1536-1276 citation: Zhu, Z; Wang, L; Wang, X; Wang, D; Wong, KK; (2025) Spatial-spectral Cell-free Sub-terahertz Networks: A Large-scale Case Study. IEEE Transactions on Wireless Communications p. 1. 10.1109/TWC.2025.3526932 <https://doi.org/10.1109/TWC.2025.3526932>. (In press). Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/10204643/1/manuscript-final.pdf