Fixed wireless access (FWA) is a mature access technology that can provide cost-effective solutions for both mobile network operators (MNOs) and multi-system operators (MSOs). It enables mobile network operators to provide fixed cable-like services and MSOs to increase speed and capacity while expanding HFC services beyond their current footprints.
CableLabs recently analyzed how key propagation parameters affect fixed wireless access (FWA) performance. Our findings indicate that although FWA deployment may be challenging, it is scenario dependent. Factors such as user throughput goals, antenna design/selection, and MIMO channel capacity can play important roles. The analysis also highlights some opportunities for operators to mitigate proliferation challenges.
We detail these findings in two new SCTE papers: “Challenges of Fixed Wireless Access Propagation” and “Experimental Analysis of FWA MIMO Capability in the 6 and 37 GHz Bands.” We explored our ideas further during our session at SCTE TechExpo24, which is now available to watch on-demand.
Together, these publications, along with related papers, analyze the challenges associated with FWA deployment in residential and indoor office environments in North America and summarize our latest research on FWA.
Our investigation was based on experimental results provided by four large-scale indoor and outdoor-to-indoor (O2I) testing campaigns, followed by comprehensive data analysis and statistical model development.
Customer Premises Equipment (CPE) in an FWA network can use an outdoor or indoor antenna. While an outdoor antenna offers better technical performance, the indoor option is more cost-effective due to lower installation costs.
Fixed wireless access test
When using 5G support, FWA performance is enhanced by the associated large channel bandwidth (ChBW), e.g., up to 100 MHz for 7 GHz spectrum and up to 400 MHz for millimeter (mmWave, 24 – 52 GHz Hz), thus increasing user productivity.
CableLabs analyzed the impact of propagation on fixed wireless access (FWA) performance in 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 propagation, angle of arrival, synthetic bandwidth, small scale fading, Rician K factor) Increased output channel capacity (MIMO).
To evaluate the performance of the FWA network and its impact from the propagation channel, multiple test campaigns were designed to characterize path loss, building entry loss (BEL), large-scale fading (e.g. shadowing), and small-scale fading effect (e.g. change of receiver position by a small number from lambda). We have chosen the testing environments accordingly:
Indoor office environment (CableLabs head office in Louisville, Colorado – 2nd floor), providing 172 links (86 per Band 6 and 37 GHz) Residential O2I environment (CableLabs Test Headquarters in Brighton, Colorado), providing 216 links (108 per Band 6 and 37 GHz), in LOS, NLOS, deep NLOS and through spreading plants (trees)
The test setup was based on a virtual circuit array (VCA), comprising the equivalent of 1,000 antenna elements. For each antenna position on the VCA, measurements included channel transfer functions (CTFs), channel impulse responses (CIRs), path loss, and so on. By using such a VCA, the need to realign the CPE antenna for each measurement and the small-scale effect of volume fading are avoided.
Poor spread
Our indoor and O2I measurement results support a direct comparison of the impact of propagation on indoor performance and indoor O2I FWA performance for the 6 and 37 GHz cases.
A high-level comparison of measured FWA O2I path losses indicates that there is a link budget penalty of 15 to 20 dB when using 37 GHz links versus similar 6 GHz links for the same type of environment. The 37 GHz O2I penalty is partially offset by the reduced number of multipath components (MPCs), resulting from the rapid Rx power decay of the 37 GHz MPC in indoor O2I and FWA environments. Intuitively, the latter suggests that 37 GHz FWA O2I/indoor links can provide better performance (SNR / user throughput) versus the sub-7 GHz bands if the associated link budget penalty can be offset .
MIMO channel capacity gain
The MIMO channel capacity gain is the ratio of the MIMO channel capacity versus the SISO channel capacity. The MIMO channel capacity gain corresponds to the MIMO user throughput gain (ratio of MIMO user throughput versus SISO user throughput). For a 2×2 MIMO link, the ideal MIMO power gain/user throughput is two. Our results indicate that MIMO capacity gain and MIMO user throughput gain are degraded by propagation in the FWA scenario.
The SCTE paper and presentation provide more details on why MIMO user throughput is higher in NLOS compared to LOS conditions and on which MIMO user throughput gain is affected by antenna separation distance, directionality, etc.
Future opportunities
Despite the challenges associated with deployment – particularly in residential and on-premises office environments in North America – FWA O2I offers a viable solution for operators seeking to expand their services. To learn more, download the SCTE papers, “Challenges for Fixed Wireless Access Deployment” and “Experimental Analysis of FWA MIMO Capability in the 6 and 37 GHz Bands,” and watch our TechExpo presentation.
