In wireless communication, strong signals and reliable coverage are necessary to meet the stringent expectations and demands of users. As discussions around 5G reliability and its challenges continue, many argue that the air interface is still not yet meeting expectations. The question becomes: What is needed to unlock 5G’s potential and future 6G wireless connections? This article discusses how emerging technologies can help overcome some of the current issues.

Despite substantial investment from governments and the private sector, mobile users in some countries still experience slow and sluggish internet. Analysis from cable.co.uk¹ recently found that Northern Africa has the lowest average broadband globally at 12.52 Mbps. At the same time, at the other end of the scale, residents in Iceland could experience speeds of 279.55 Mbps and the vast difference between the two is apparent. Slow download speeds frustrate consumers and have broader economic consequences. Vodafone estimates that small and medium-sized businesses are missing out on as much as £8.6 billion a year in productivity savings because the rollout of standalone 5G has been so slow.² Without reliable wireless 5G connectivity or 5G over Wi-Fi, the prospect of smart homes, factories and cities seems unattainable.

In the U.S., there have been challenges connecting remote communities. However, adoption rates are generally high, thanks to large coverage footprints and high speeds. The situation is even more positive in the Middle East, where countries such as Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates have been leading the way in deploying 5G networks with some of the fastest mobile internet speeds in the world.

Figure 1 Prototype RIS. Source: Drexel Wireless Systems Laboratory.

Figure 2 Airgain Lighthouse^TM smart NCR indoor/outdoor solution.

There is no single solution for improving the 5G rollout timeline and its performance. However, innovations in antennas, repeaters and modems are now set to bridge the gap between vision and reality. In recent years, discussions about reconfigurable intelligent surfaces (RIS) and smart repeaters have become hot topics.

THE COMPLEXITIES OF WIRELESS

A whole network approach is needed to solve the problems surrounding 5G connectivity. Engineers and technology developers must focus their research, design and technical capabilities on enhancing every aspect of the user journey, from the service provider to the end-user. Engineers will appreciate the complexities inherent in wireless, starting with the propagation of 5G signals. Even though 5G can deliver lower latency, increased capacity and faster throughput, the higher frequencies result in a shorter propagation distance from the base station. The 700 MHz part of the spectrum can transmit signals over long distances and penetrate obstacles more effectively. Still, its throughput is lower due to limited available bandwidth, on the order of 10 to 20 MHz per operator.

Higher throughput is possible with the C-Band spectrum around 3.5 GHz, with hundreds of megahertz of RF signal bandwidths available. The problem is that signals in this band only travel 20 percent as far as 700 MHz signals and this propagation distance reduces further at higher frequencies. There is also an issue with limited penetration through walls and obstacles inside buildings. This leads to coverage gaps impacting user experience, network reliability and service consistency.

Demand for 5G is highest in densely populated cities, yet atmospheric pollution, buildings and people can all interrupt or block high frequency signals. To counter this, thousands of base stations or small cells would be needed to reach the highest coverage levels. At a cost of billions, networks this size would be prohibitively expensive for providers and likely incur backlash from nearby people.

RECONFIGURABLE INTELLIGENT SURFACES

An innovative solution with enormous potential to enhance 5G performance is emerging with RIS. Designed to operate in the sub-6 GHz band, primarily at the center frequency of 3.5 GHz, RIS comprises thousands of unit cells equipped with controllable elements (e.g., varactor diodes). These controllable elements enable the surface to reconfigure its response by manipulating incoming electromagnetic (EM) waves to improve signal reception in coverage blind spots. The response can be improved, potentially, by more than 15 dB when configured for a specific direction. Figure 1 shows a prototype RIS board operating in the sub-6 GHz frequency band.

RIS technology promises to be a game-changer for ensuring seamless connectivity in 5G and future 6G networks. Its ability to reconfigure and direct EM waves toward areas with poor coverage can significantly boost 5G performance, efficiency and reliability. It has the potential to boost public confidence in wireless communication technologies. However, the technology is still several years away from large-scale commercialization. For all its advantages, RIS still comes with its challenges for implementation in terms of design complexities, deployment costs and energy efficiency.

5G SMART REPEATERS

Figure 3 (a) Baseline base station path loss characteristic. (b) Base station path loss characteristic with a smart repeater.
(c) Base station path loss characteristic with smart repeater and RIS. Source: Drexel University.

In addition to RIS, 5G smart repeaters are another potentially transformative technology. These repeaters can receive, clean up, amplify and forward the signal down the line. The repeater automatically detects the optimal signal direction while mobile devices maintain fidelity and upload/download speeds even if the base stations are further away. Smart repeaters are a more traditional approach and have evolved over several years with the advancements in wireless technology. But they have proven their worth in enhancing wireless communication.

Dependable and practical, smart repeaters can reduce the cost of wireless infrastructure for operators. These repeaters do not rely on broadband cable backhaul and only require access to power, which could include solar, making them ideal for areas that have always struggled with reliable connectivity. Repeaters receive the desired signal, amplify it from low levels and retransmit it to ensure it reaches the destination with minimal distortion. The adaptability of this solution allows smart repeaters to fit into any communication environment, making them a reliable choice. For this reason, and because the devices are easy to install without compromising performance, solution providers are rapidly moving smart repeaters into the home and enterprise market and continuing to cater to mobile network operators.

Network-controlled repeaters (NCRs) can also play an important role in boosting signal strength and improving coverage in weak zones. These devices are typically an RF repeater that can receive and process side control information (SCI) from the network. This allows NCRs to amplify the signal more efficiently than traditional repeaters.

NCRs are an advanced evolution of traditional repeaters designed to enhance wireless coverage wherever signal strength is weak, such as in dense urban environments, rural zones and indoor spaces. Unlike traditional repeaters, which amplify and retransmit signals, NCRs operate with a higher level of intelligence, utilizing real-time network data and control mechanisms to optimize signal propagation dynamically. This is enabled by accessing the network “knowledge” via the SCI. This dynamic control allows NCRs to adapt to changing conditions, such as varying user demand or physical environmental factors like vehicles, people or other objects on the move. This ensures better signal quality and coverage continuity.

NCRs incorporate intelligent features like beamforming, multi-beam antenna systems and interference cancellation. This allows them to direct signals to specific users and reduce signal losses more efficiently. For example, suppose the network detects higher congestion in one area. In that case, the NCR will optimize its transmission power or beamforming direction to alleviate the issue, ensuring cleaner and more efficient signal propagation. Figure 2 shows an Airgain NCR solution mounted on the side of a building for smart indoor/outdoor coverage.

RIS and NCRs have a great synergy and can work together to provide better coverage and signal quality in challenging environments. Active RIS dynamically interacts with NCR to direct signal beams, reducing interference and boosting throughput. Recent simulations using this collaborative approach have shown enormous potential for improvements in coverage and how both could be integrated into a unified system for future indoor use. Airvine, in conjunction with Drexel University researchers, used the Wireless InSite® model to display outdoor-to-indoor coverage with complete 3D path loss for several network configurations. Figure 3a shows the baseline coverage results for a 3.5 GHz base station. Figure 3b shows how the path loss changes by adding a smart repeater and Figure 3c shows the path loss profile with an RIS/smart repeater combination.

Researchers in the Drexel Wireless Systems Laboratory partially validated the concept of coexistence and cooperation of RIS technology and NCR for smart repeaters within the same network for indoor coverage. They simulated 5G network coverage in the n77 band in C-Band. Their results come from using different scenario features in Wireless InSite,³ a commercial computational EM ray tracing system that employs 3D shooting and bouncing ray methods.

The first scenario, shown in Figure 3a, illustrates the indoor-to-outdoor coverage of a 3.5 GHz 5G New Radio (NR) macro cell used as a baseline. At 3.5 GHz, 5G signals suffer from high path loss when penetrating walls and other obstacles of a target office building about 1.5 km away. This leads to weak signals and poor reception, particularly in deeper indoor areas away from windows, where dead zones are common.

Figure 4 Airgain Lighthouse 5G NR smart repeater.

Figure 3b demonstrates using an NCR equipped with beamforming capabilities strategically placed between the macro cell base station and the target building at approximately 40 meters. The smart repeater receives the weak signal from the base station via its donor antenna, amplifies it and retransmits it through its service antenna toward the target office building. As shown in Figure 3b, the smart repeater is modeled as a service antenna with a 15 dB gain, enhancing the base station signal by about 30 dB and relaying it through the building window. However, there is a significant dead zone or shadow area within the coverage area of the building due to the limited field-of-view of the smart repeater. The efforts at Drexel University were more than just an academic exercise. Figure 4 shows an example of an Airgain 5G NR smart repeater solution that operates in the n77 band of the simulation.

To further improve signal coverage and ensure that users in these shadowed areas receive stronger and more consistent 5G signals, an RIS is also integrated and strategically deployed on walls within the building to enhance signal quality. The Wireless InSite 3D software models the RIS using the Communication Research Centre (CRC) Canada’s ray optic model.⁴ This model consists of a locally periodic, passive metasurface made up of patterns of sub-wavelength scatterers printed on a substrate of glass, plastic or other materials.⁵ The scattering behavior of the RIS is dynamically adjusted to steer the signal by 65 degrees, enhancing the 5G signal from the smart repeater and directing it optimally toward shadowed areas in the corner offices far from the window. This leads to fewer dead zones, as shown in Figure 3c. Future indoor RIS can potentially be made more efficient in adapting their state using power sensors integrated with the surface⁶ and can be more unobtrusively deployed in indoor environments using novel materials and manufacturing techniques like fabrics.⁷ The RIS/smart repeater-enabled 5G network helps overcome the indoor coverage challenges of the 3.5 GHz 5G network, ensuring reliable connectivity in complex environments like office buildings.

IN-BUILDING WIRELESS SOLUTIONS

In the early days of cellular communications, in-building wireless (IBW) coverage was not a primary concern. By the mid-2000s, the need for reliable in-building coverage had grown significantly with the advent of 3G and 4G technologies. This demand has only intensified with the introduction of 5G and now 6G. IBW solutions address these challenges by enhancing network coverage and capacity in areas where the macro network cannot adequately service the demand. This can be due to high penetration losses from building materials, low emissivity glass or the building’s structure blocking the signal. Many ongoing simulations on in-building solutions could help resolve complexities around indoor 5G challenges.

Distributed antenna systems (DAS) are popular solutions for improving IBW coverage. This approach involves deploying a network of antennas throughout a building to distribute the signal from a central location. There are several types of DAS, including passive, active, hybrid and digital DAS. Each of these DAS types has advantages and limitations depending on the size and type of venue.

AMPLIFYING THE BENEFITS

Figure 5 Airgain Lighthouse Micro Smart Repeater.

Enhanced 5G connectivity has the potential to revolutionize industries while consumers seek better streaming experiences and more connected smart home devices. For telecom operators, the challenge lies in maximizing network performance using existing infrastructure without the need for an excessive number of additional base stations. Extending 5G coverage beyond urban areas to underserved regions is also crucial in ensuring broader accessibility. Unobtrusive solutions, like the Airgain Lighthouse Micro Smart Repeater shown in Figure 5, will help with small-office and home-office adoption of the technology.

To achieve this, network providers must adopt the latest technologies that address these challenges and unlock the numerous benefits 5G offers, such as faster download and upload speeds, improved reliability and reduced latency. Solutions like RIS, smart repeaters and NCR are helping network operators optimize their investments. These innovations reduce deployment costs by leveraging existing infrastructure while enhancing signal quality and coverage, making them valuable assets in the industry’s toolkit.

The demand for reliable, high speed 5G connectivity is growing. These and other technologies are the key to overcoming challenges such as signal interference and rising operational costs. New developments in these areas will pave the way for smarter, more connected communities and industries, ensuring that the transformative promise of 5G and, eventually, 6G becomes a global reality.

References

1. “Worldwide Broadband Speed League 2024,” cable.co.uk, Web: www.cable.co.uk/broadband/speed/worldwide-speed-league/?mc_cid=05b0480aeb&mc_eid=659a6c0250.
2. “Supercharging Small Businesses,” Vodafone, March 2024, Web: www.vodafone.co.uk/newscentre/app/uploads/2024/02/Supercharging-Small-Businesses-Web-Hi-Res.pdf.
3. “Wireless InSite® 3D Wireless Propagation Software,” Remcom, Web: https://www.remcom.com/wireless-insite-em-propagation-software.
4. Y. L. C. de Jong, “Uniform Ray Description of Physical Optics Scattering by Finite Locally Periodic Metasurfaces,” IEEE Transactions on Antennas and Propagation, Vol. 70, No. 4, 2022, pp. 2949–2959.
5. S. Stewart, Y. L. C. de Jong, T. J. Smy and S. Gupta, “Ray-Optical Evaluation of Scattering From Electrically Large Metasurfaces Characterized by Locally Periodic Surface Susceptibilities,” IEEE Transactions on Antennas and Propagation, Vol. 70, No. 2, 2022, pp. 1265–1278.
6. M. A. S. Tajin, K. Anim and K. R. Dandekar, “Incident Power and Relative Phase Distribution Mapping in Reconfigurable Intelligent Surfaces Using Energy Harvesting,” IEEE Transactions on Antennas and Propagation, Vol. 71, No. 7, 2023, pp. 6111–6119, Web: https://ieeexplore.ieee.org/document/10105212.
7. K. Anim, M. A. Saleh Tajin, C. E. Amanatides, G. Dion and K. R. Dandekar, “Conductive Fabric-Based Reconfigurable Intelligent Surface,” IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (AP-S/URSI), 2022, pp. 1484–1485.