This Industry Viewpoint was authored by Sergiu Nedevschi, Co-Founder & CSO at Tarana Wireless
Fixed wireless access (FWA) networks have long been used to provide basic internet service in areas with no fiber or coax infrastructure. Unfortunately, these legacy FWA solutions are significantly challenged by the obstructions pervasive in most residential neighborhoods, which block wireless signals and severely limit these networks’ utility as demand for faster internet service continues to rise. These obstructionscome in a wide variety of forms, including buildings and other structures, trees, moving vehicles, and terrain features. Data gathered over many years by the mobile network industry indicates that roughly 90% of all suburban link pathways beyond 350 yards from a tower will be obstructed. This is referred to as a non line of sight (NLoS) connection rather than line of sight (LoS).
NLoS propagation significantly lowers link reliability, speed, and range for legacy FWA systems. These shorter distances decrease the coverage area that a single base station can serve while increasing costs, as more base stations and tower sites are required for a given coverage objective. Slower link speeds also limit the service tiers operators can provide to customers and corresponding average revenue per user.
NLoS connections attempted with legacy FWA technology are also much more susceptible to degradation from changing conditions, such as trees moving in the wind. As a result, maintaining customer satisfaction and performance consistency are often very difficult with these networks. FWA is unlike mobile networks, where you can move your phone to somewhere with a stronger, more reliable signal. Unfortunately, you cannot easily move your home if the connection is poor.
A good fixed wireless system needs an approach to dealing with NLoS, since chopping down trees or moving your neighbor’s house to get rid of obstacles is not often practical. In addition, moving base stations closer to target homes in the hope of getting clear lines of sight is rarely viable, due to either limited site availability or the high cost per household served by building large numbers of sites.
Next generation fixed wireless access (ngFWA) networks overcome a majority of the challenges associated with NLoS links by leveraging a distributed massive multiple-input, multiple-out (DM-MIMO) architecture at the base node (BN) on the tower and the remote node (RN) on the subscriber’s home. In this approach each device has many independent antennas that can be used in combination to shape the best link transmission patterns between them.
These patterns involve a signal processing technique known generally as beamforming, which uses discrete elements in the antenna arrays of the BN and the RN to direct radio energy along the most productive paths between them. This increases aggregate signal strength “harvested” by the receiver, and the impact of attenuation or self-interference is reduced. ngFWA uses a new class of unique beamforming approaches in a closed-loop process, in which the BN and the RN work collaboratively over time to find and maintain the best beamforming solution to provide improved link throughput, stability, reliability, and low latency.
A key requirement for ngFWA is the ability to transmit a pattern optimized along the three essential dimensions of space, time, and frequency to make the most of current conditions in the “channel” between BN and RN. The counterpart to optimized transmission from ngFWA beamforming involves the multiple antenna arrays on the receiver pulling the signal from various angles of arrival, delays, amplitude, and phases to combine multipath signals and reconstruct the original signal with very high fidelity. This essentially perfect reconstruction of multipath signals results in a stronger link because all available energy is being used, and it is essential to leveraging diffraction and reflection around objects that would otherwise obstruct the signal.
All these features work together to achieve reliable, stable, and high-speed links that cover never-before seen distances for non-line of sight, line of sight, or near line of sight. With ngFWA, links that were not possible before are now achievable, which means wireless providers can offer faster, more reliable service to a broader customer base with lower costs of infrastructure by significantly reducing the need to build new towers or install more base stations.
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