Fixed wireless access (FWA) is a mature access technology that could provide cost-effective solutions for both mobile network operators (MNOs) and multiple system operators (MSOs). It enables MNOs to provide fixed cable-like services and MSOs to increase speed and capacity while extending HFC services beyond their current footprints.

CableLabs recently analyzed how key propagation parameters impact FWA performance. Our findings indicate that while FWA propagation can be challenging, it is scenario dependent. Factors such as user throughput targets, antenna design/selection and MIMO channel capacity can play significant roles. The analysis also highlights some opportunities for operators to mitigate the propagation challenges.

We detailed these findings in two new SCTE papers: “Fixed Wireless Access Propagation Challenges” and “Experimental FWA MIMO Capacity Analysis in 6 and 37 GHz Bands.” We explored our insights further during our session at SCTE TechExpo24, which is now available to watch on-demand.

Together, these publications, along with related papers, analyze the FWA propagation-related challenges for North American residential and indoor office environments and summarize our latest research on FWA.

Our investigation was based on experimental results provided by four extensive indoor and outdoor-to-indoor (O2I) test campaigns, followed by a thorough data analysis and statistical model development.

Customer premises equipment (CPE) in a FWA network can use either an outdoor or an indoor antenna. While the outdoor antenna offers better technical performance, the indoor option is more cost-effective due to minimal installation costs.

Fixed Wireless Access Testing

When using 5G support, the FWA performance is augmented by the associated large channel bandwidth (ChBW), e.g., up to 100MHz for sub 7GHz spectra and up to 400MHz for millimeter (mmWave, 24 - 52 GHz), accordingly increasing user throughput.

CableLabs analyzed the propagation impact upon FWA performance in both indoor and outdoor-to-indoor (O2I) scenarios in the 6 GHz and 37 GHz bands. The studies are grouped into two categories:

• Single-input multiple-output (SIMO) propagation challenges (path loss, O2I loss, power delay and angular profiles, delay and angular spread, angle of arrival, synthetic beamwidth, Small-scale fading Rician K-factor)
• Multiple-input multiple-output (MIMO) channel capacity gain

To evaluate the FWA network performance and impact from the propagation channel, multiple test campaigns were designed to characterize the path loss, building entry loss (BEL), large-scale fading (e.g., shadowing), small-scale fading impact (e.g., changing the receiver position by a few lambdas). We selected the test environments accordingly:

• An indoor office environment (CableLabs’ main office in Louisville, Colorado -- 2nd floor), providing 172 links (86 for each 6 and 37GHz band)
• O2I residential environment (the CableLabs Test House in Brighton, Colorado), providing 216 links (108 for each 6 and 37GHz band), in LOS, NLOS, deep NLOS and through vegetation (trees) propagation

The test setup was based on a virtual circular array (VCA), featuring the equivalent of 1,000 antenna elements. For each antenna position on the VCA, measurements included the channel transfer functions (CTFs), channel impulse responses (CIRs), path loss, etc. Using such a VCA avoided a need to re-align the CPE antenna for each measurement and the small-scale fading impact.

Propagation Impairments

Our indoor and O2I measurement results support a direct comparison of the propagation impact upon the indoor and O2I FWA indoor performance for the 6 and 37 GHz cases.

A high-level comparison of the measured FWA O2I path losses indicates that there is a 15-20 dB link budget penalty when 37 GHz links are used vs. similar 6 GHz links for the same type of environment. The 37 GHz O2I penalty is partially compensated by the reduced number of multipath components (MPCs), caused by the rapid Rx power decay of the 37 GHz MPC in the O2I and indoor FWA environments. Intuitively, the latter suggests that 37 GHz FWA O2I/indoor links could provide a better performance (SNR/User Throughput) vs. sub 7GHz bands if the related link budget penalty could be compensated.

MIMO Channel Capacity Gain

The MIMO channel capacity gain represents the ratio of the MIMO vs. SISO channel capacity. The MIMO channel capacity gain is identical to the MIMO user throughput gain (the ratio of the MIMO user throughput vs. SISO user throughput). For a MIMO 2×2 link, the ideal MIMO capacity gain/user throughput is equal to two. Our findings indicate that the MIMO capacity gain and the MIMO user throughput gain is degraded due to the propagation in a FWA scenario.

Our SCTE paper and presentation provide more details on the causes of the MIMO user throughput gain being higher in NLOS than LOS conditions and on MIMO user throughput gain impacted by antenna separation distance and orientation, etc.

Future Opportunities

Despite the propagation-related challenges — particularly in North American residential and indoor office environments — FWA O2I presents a viable solution for operators seeking to expand their service footprint. To learn more, download the SCTE papers, “Fixed Wireless Access Propagation Challenges” and “Experimental FWA MIMO Capacity Analysis in 6 and 37 GHz Bands,” and watch our TechExpo presentation.