{
  "abstract": "This letter investigates the spatial separability of closely-located users in cell-free massive multiple-input multiple-output (CF-mMIMO) systems using high-diversity real-world channel measurements. We evaluate the orthogonality of four closely-located users under various CF topologies. To ensure a fair comparison, a constant aggregate number of 64 transmit antennas is maintained across all configurations. Our results demonstrate that transitioning from a co-located to a distributed architecture significantly enhances spatial multiplexing: increasing the number of access points (APs) from one to eight reduces both the median channel correlation and the condition number by approximately 50%, while the median spectral efficiency is increased by 5%-6.7% from one to four APs. However, scaling beyond these thresholds results in a performance saturation, as additional APs contribute negligible power due to decreasing large-scale fading coefficients. These findings suggest that excessive AP densification leads to marginal improvements, highlighting a practical trade-off between spatial diversification and the effective signal strength of additional distributed APs.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": null,
  "author_total": 6,
  "authors": [
    {
      "name": "Dimitrios Georgios Nixarlidis"
    },
    {
      "name": "Eric Pierre Simon"
    },
    {
      "name": "Davy Gaillot"
    },
    {
      "name": "Valentin Picquet"
    },
    {
      "name": "Pierre Laly"
    },
    {
      "name": "Joumana Farah"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/6279q6hgw9m5x.bib",
  "cited_by": 0,
  "doi": "10.1049/ell2.70734",
  "fulltext_url": null,
  "id": "6279q6hgw9m5x",
  "issns": [
    "0013-5194",
    "1350-911X"
  ],
  "landing_url": "https://hal.science/hal-05820914v1",
  "language": "en",
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "hal",
      "0.phys"
    ],
    [
      "hal",
      "0.spi"
    ],
    [
      "openalex",
      "2208|Advanced MIMO Systems Optimization"
    ]
  ],
  "openalex": "W7160907043",
  "pdf_url": "https://hal.science/hal-05820914/document",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-07",
  "publisher": "IET",
  "ris": "https://research.draconitic.com/paper/6279q6hgw9m5x.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:59Z",
      "native_id": "hal-05820914",
      "source": "hal",
      "url": "https://hal.science/hal-05820914v1"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "hal:0.phys",
      "subfield": "general"
    }
  ],
  "title": "Characterization of Closely‐Located Users in Measured Cell‐Free Massive MIMO Networks",
  "title_text": "Characterization of Closely‐Located Users in Measured Cell‐Free Massive MIMO Networks",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:17:59Z",
  "url": "https://research.draconitic.com/paper/6279q6hgw9m5x",
  "venue": "Electronics Letters",
  "versions": []
}