This industry view was written by Sergiu Nedevschi, co-founder and CSO at Tarana Wireless
Fixed Wireless Access (FWA) networks have long been used to provide basic Internet service in areas without fiber or coaxial infrastructure. Unfortunately, these legacy FWA solutions are significantly challenged by the ubiquitous barriers in most residential neighborhoods that block wireless signals and severely limit the usefulness of these networks as demand for faster Internet service continues to grow. . These obstructionscome in a wide variety of forms, including buildings and other structures, trees, moving vehicles, and terrain features. Data collected over many years by the mobile network industry indicates that approximately 90% of all suburban backhauls beyond 350 meters from a tower will be obstructed. This is called a No Line of Sight (NLoS) connection rather than a Line of Sight (LoS) connection.
NLoS propagation dramatically reduces link reliability, speed, and range for legacy FWA systems. These shorter distances reduce the coverage area that a single base station can serve while increasing costs, as more base stations and tower sites are needed for a given coverage goal. Slower link speeds also limit the service levels operators can provide to customers and the corresponding average revenue per user.
NLoS connections attempted with legacy FWA technology are also much more likely to be degraded by changing conditions, such as trees moving in the wind. Therefore, it is often very difficult to maintain customer satisfaction and performance consistency with these networks. FWA is different from mobile networks, where you can move your phone to a location with a stronger, more reliable signal. Unfortunately, you cannot easily move your house if the connection is poor.
A good fixed wireless system requires an approach to dealing with NLoS, because cutting down trees or moving your neighbor’s house to remove obstacles is often not practical. Additionally, moving base stations closer to target homes in hopes of obtaining clear lines of sight is rarely viable, either due to limited site availability or the high cost per household served by building a large number of sites.
Next-generation fixed wireless access (ngFWA) networks overcome the majority of challenges associated with NLoS links by leveraging a massive distributed multiple-input multiple-output (DM-MIMO) architecture at the base node (BN) on the tower and the Remote Node (RN) at the subscriber’s home. In this approach, each device has many independent antennas that can be used in combination to form the best link transmission patterns between them.
These designs involve a signal processing technique commonly known as beamforming, which uses discrete elements in the BN and RN antenna arrays to direct radio energy along the most productive paths between them. . This increases the overall strength of the signal “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 RN work collaboratively over time to find and maintain the best beamforming solution to improve the link speed, stability, reliability and low latency.
A key requirement for ngFWA is the ability to transmit an optimized pattern along the three critical dimensions of space, time, and frequency to make the most of current conditions in the “channel” between BN and RN. The optimized transmission counterpart of ngFWA beamforming involves the multiple antenna arrays on the receiver pulling the signal at different angles of arrival, delays, amplitude, and phases to combine the 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 used, and it is essential to take advantage of diffraction and reflection around objects that would otherwise obstruct the signal.
All of these features work together to achieve reliable, stable, high-speed links that cover distances never seen before for non-line of sight, line-of-sight, or near line-of-sight. With ngFWA, links that weren’t possible before are now achievable, meaning wireless service providers can deliver faster, more reliable service to a wider customer base with lower infrastructure costs by dramatically reducing the need to build new towers or install more base stations.
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Categories: Industry Perspective Telecommunications Equipment Wireless
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