[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"doc-detail-86530-en":3,"doc-seo-86530-105":29,"detail-sidebar-cat-0-en-105":90},{"code":4,"msg":5,"data":6},0,"success",{"doc_id":7,"user_id":8,"nickname":9,"user_avatar":10,"doc_module":4,"category_id":11,"category_name":12,"doc_title":13,"doc_description":14,"doc_content":15,"file_id":16,"file_url":17,"file_type":18,"file_size":19,"view_count":4,"is_deleted":4,"is_public":20,"is_downloadable":20,"audit_status":20,"page_count":21,"language":22,"language_code":23,"site_id":24,"html_lang":23,"table_of_contents":25,"faqs":26,"seo_title":13,"seo_description":14,"update_tm":27,"read_time":28},86530,1374391974468,"Eden","https://ap-avatar.wpscdn.com/davatar_29158cc5080c5b710cf443261637dec0",8,"Research & Report","Holographic MIMO-assisted Multiuser Transmission with Electromagnetic Exposure Constraints","Holographic multiple-input multiple-output (HMIMO) enables continuous electromagnetic (EM) field control over large apertures, but user-side EM exposure becomes a critical issue in large-scale arrays. This paper develops a multiuser uplink HMIMO model with a physically consistent specific absorption rate (SAR) framework to quantify exposure. A spectral efficiency (SE) maximization problem is then solved using a modified iterative water-filling algorithm. Simulations show improved SE while satisfying SAR constraints.","Holographic MIMO-assisted Multiuser Transmission with Electromagnetic Exposure Constraints  \nYilin Yang, Mengyu Qian, Graduate Student Member, IEEE, Ahmed Elzanaty, Senior Member, IEEE,  \nand Li You, Senior Member, IEEE  \narXiv :2607 . 11015v1 [ ee ss . SP] 13 Jul 2026  \nAbstract—Holographic multiple-input multiple-output (HMIMO) has emerged as a promising technology for future wireless systems by enabling continuous electromagnetic (EM) field control over large apertures. However, user-side EM exposure has become an increasingly important concern in large-scale array systems. This paper addresses this issue by developing a multiuser uplink HMIMO model, where a physically consistent specific absorption rate (SAR) model is established to quantify the EM exposure. On this basis, a spectral efficiency (SE) maximization problem is addressed by developing a modified iterative water-filling algorithm. Simulation results demonstrate that the proposed algorithm effectively improves the system SE while satisfying the SAR constraints.  \nIndex Terms—Holographic multiple-input multiple-output (HMIMO), specific absorption rate (SAR), spectral efficiency (SE).  \nI. INTRODUCTION  \nThe sixth-generation (6G) wireless networks are projected to handle the explosive rise in data traffic, driven by a surge of new devices and applications, with far greater spectral efficiency (SE) requirements [1, 2] . With the advancement of metamaterials technology, the concept of holographic multiple-input multiple-output (HMIMO) has been explored to enhance the transmission performance with limited antenna aperture [3] . Unlike traditional MIMO, HMIMO employs densely distributed sub-wavelength antenna elements that form a quasi-continuous aperture [4] . By precisely shaping the spatial electromagnetic (EM) field, HMIMO can efficiently encode information onto the wavefronts and approach the theoretical capacity bound of a finite aperture [5] .  \nRecent studies have extensively investigated HMIMO in terms of channel modeling, beamforming design and performance analysis. For example, [6] proposed a wavenumber division multiplexing scheme based on Fourier basis expansion for one-dimensional transceiver models under line of sight (LoS) conditions. Later, [7] and [8] further studied multiuser HMIMO transmission and focused on SE optimization for HMIMO systems.  \nAlthough these works have demonstralicitly account for EM exposure. This issue is particularly important for HMIMO, since its quasi-continuous aperture can generate highly focused EM fields, which may lead to elevated local energy absorption for users located close to the transmitting surface. ted the potential performance gains of HMIMO, they mainly considered system designs under transmit power constraints and did not exp  \nCopyright (c) 2026 IEEE. Personal use of this material is permitted. However, permission to use this material for any other purposes must be obtained from the IEEE by sending a request to [pubs-permissions@ieee.org](pubs-permissions@ieee.org).  \nThis work was supported by the National Natural Science Foundation of China for Outstanding Young Scholars under Grant 62322104, the Jiangsu Province Major Science and Technology Project under Grant BG2024005, the Natural Science Foundation of Jiangsu Province under Grant BK20231415, and the Fundamental Research Funds for the Central Universities under Grant 2242022k60007 . (Yilin Yang and Mengyu Qian contributed equally to this work.) (Corresponding author: Li You.)  \nYilin Yang, Mengyu Qian, and Li You are with the National Mobile Communications Research Laboratory, Southeast University, Nanjing 210096, China, and also with the Purple Mountain Laboratories, Nanjing 211100, China (e-mail: [yilinyang@seu.edu.cn](yilinyang@seu.edu.cn); [qianmy@seu.edu.cn](qianmy@seu.edu.cn); [lyou@seu.edu.cn](lyou@seu.edu.cn)).  \nAhmed Elzanaty is with 5GIC & 6GIC, Institute for Communication Systems (ICS), University of Surrey, GU2 7XH Guildford, U.K. (e-mail: [a","cbCaipaIT1yBhS3x","https://ap.wps.com/l/cbCaipaIT1yBhS3x","pdf",581592,1,6,"English","en",105,"# Introduction\n## HMIMO in 6G and motivation\n## Prior work on HMIMO and EM exposure\n## SAR metric and limitations of conventional models\n## Key contributions","[{\"question\":\"What problem does the paper address in HMIMO multiuser uplink transmission?\",\"answer\":\"It addresses user-side electromagnetic (EM) exposure concerns by modeling exposure in a holographic MIMO multiuser uplink setting using a specific absorption rate (SAR) framework.\"},{\"question\":\"How does the paper quantify EM exposure?\",\"answer\":\"It establishes a physically consistent SAR model, based on a derived formulation that explicitly captures quasi-continuous current distribution over holographic apertures.\"},{\"question\":\"What method is used to maximize spectral efficiency under SAR constraints?\",\"answer\":\"It formulates a spectral efficiency maximization problem and solves it with a modified iterative water-filling algorithm that enforces the SAR constraints.\"}]",1784212426,15,{"code":4,"msg":30,"data":31},"ok",{"site_id":24,"language":23,"slug":32,"title":13,"keywords":33,"description":14,"schema_data":34,"social_meta":85,"head_meta":87,"extra_data":89,"updated_unix":27},"holographic-mimo-assisted-multiuser-transmission-with-electromagnetic-exposure-constraints","",{"@graph":35,"@context":84},[36,53,67],{"@type":37,"itemListElement":38},"BreadcrumbList",[39,43,47,50],{"item":40,"name":41,"@type":42,"position":20},"https://docshare.wps.com","Home","ListItem",{"item":44,"name":45,"@type":42,"position":46},"https://docshare.wps.com/document/","Document",2,{"item":48,"name":12,"@type":42,"position":49},"https://docshare.wps.com/document/research-report/",3,{"item":51,"name":13,"@type":42,"position":52},"https://docshare.wps.com/document/holographic-mimo-assisted-multiuser-transmission-with-electromagnetic-exposure-constraints/86530/",4,{"url":51,"name":13,"@type":54,"author":55,"headline":13,"publisher":57,"fileFormat":60,"inLanguage":23,"description":14,"dateModified":61,"datePublished":61,"encodingFormat":60,"isAccessibleForFree":62,"interactionStatistic":63},"DigitalDocument",{"name":9,"@type":56},"Person",{"url":40,"name":58,"@type":59},"DocShare","Organization","application/pdf","2026-07-16",true,{"@type":64,"interactionType":65,"userInteractionCount":4},"InteractionCounter",{"@type":66},"ViewAction",{"@type":68,"mainEntity":69},"FAQPage",[70,76,80],{"name":71,"@type":72,"acceptedAnswer":73},"What problem does the paper address in HMIMO multiuser uplink transmission?","Question",{"text":74,"@type":75},"It addresses user-side electromagnetic (EM) exposure concerns by modeling exposure in a holographic MIMO multiuser uplink setting using a specific absorption rate (SAR) framework.","Answer",{"name":77,"@type":72,"acceptedAnswer":78},"How does the paper quantify EM exposure?",{"text":79,"@type":75},"It establishes a physically consistent SAR model, based on a derived formulation that explicitly captures quasi-continuous current distribution over holographic apertures.",{"name":81,"@type":72,"acceptedAnswer":82},"What method is used to maximize spectral efficiency under SAR constraints?",{"text":83,"@type":75},"It formulates a spectral efficiency maximization problem and solves it with a modified iterative water-filling algorithm that enforces the SAR 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