Neutral-Hosts In The Shared Mid-Bands: Addressing Indoor Cellular Performance

TL;DR

The paper investigates indoor neutral-host deployments in the CBRS 3.55–3.7 GHz band to address indoor mid-band cellular performance. Using real-world measurements in a three-floor healthcare facility, it shows robust indoor coverage, minimal outdoor interference, and substantial DL/UL gains when users are served by the neutral-host, plus UE power savings and capacity offload for MNOs. The work highlights the practical potential of low-power indoor CBRS deployments for spectrum efficiency and coexistence with incumbents, while acknowledging the need for broader multi-site validation. It lays groundwork for spectrum-sharing policy and deployment planning in mid-band bands like 3.1–3.45 GHz and beyond.

Abstract

The 3.55 - 3.7 GHz Citizens Broadband Radio Service (CBRS) band in the U.S., shared with incumbent Navy radars, is witnessing increasing deployments both indoors and outdoors using a shared, licensed model. Among the many use-cases of such private networks is the indoor neutral-host, where cellular customers of Mobile Network Operators (MNOs) can be seamlessly served indoors over CBRS with improved performance, since building loss reduces the indoor signal strength of mid-band 5G cellular signals considerably. In this paper, we present the first detailed measurements and analyses of a real-world deployment of an indoor private network serving as a neutral-host in the CBRS band serving two MNOs. Our findings demonstrate significant advantages: (i) minimal outdoor interference from the CBRS network due to over 22 dB median penetration loss, ensuring compatibility with incumbent users; (ii) substantial indoor performance gains with up to 535$\times$ and 33$\times$ median downlink and uplink throughput improvements, respectively, compared to the worst-performing MNO; (iii) reduced uplink transmit power for user devices (median 12 dB reduction), increasing energy efficiency; and (iv) significant capacity offload from the MNO network (median 233 resource blocks/slot freed in 5G), allowing MNOs to better serve outdoor users. These results highlight the potential of low-power indoor CBRS deployments to improve performance, increase spectrum efficiency, and support coexistence with current and future incumbents, e.g., the 3.1 - 3.45 GHz band being considered for sharing with federal incumbents in the U.S.

Figures (18)

• Figure 1: Neutral-host architecture.
• Figure 2: Neutral-host deployment at the healthcare facility.
• Figure 3: RSRP heatmaps of neutral-host and MNO's 5G deployments.
• Figure 4: Comparison of RSRP for all observed PCIs.
• Figure 5: Comparison of neutral-host RSRP observed indoors and outdoors.