As 5G networks are still rolling out around the world, the telecommunications industry is already looking toward the future. 5G brought improvements in connectivity with faster download speeds, lower latency and enhanced network reliability. With 6G, these capabilities will be even greater and meet the ever-growing demand for connectivity, which now stands at a 25 percent compound annual growth rate, effectively doubling every three years.
A future 6G network operating in sub-THz bands should be able to provide download speeds that allow upwards of 1 Tbps, which is about 100x faster than 5G. The enhanced capabilities of 6G will enable seamless integration of various technologies, such as communications and sensing, as well as expansive use of AI and machine learning for network optimization. Figure 1 shows how wireless infrastructure evolves with each technology cycle, along with the role that towers play in these networks.
In the wireless infrastructure business, we look at each network generation cycle through the lens of three advancements: spectrum, technology and site densification.
The cycle of each generation starts with spectrum, as new spectrum coming onto the market means new opportunities for the tower business. High-powered, dedicated spectrum is the key and with future 6G frequencies in the 7 to 15 GHz and sub-THz bands, opportunities for new RF platforms will open up opportunities for innovative technology, radio development and testing services to optimize radio placement.
Spectrum is expensive, so once these new radios are deployed, how do we get more bits per second per hertz over their lifecycle? Increasing efficiency and lowering the cost per bit is where the technology roadmap comes into play. Many cellular technology companies and start-ups create technologies that become site upgrades. For a tower company, our customers are continuously adding to and upgrading existing radios, enabling more capacity at both the site and system level.
Finally, densifying the infrastructure is an important component of increasing capacity at the end of a generation cycle.
To see how the role of towers has evolved in the wireless ecosystem, we can look back to 4G. As an early innovator in the tower space, American Tower purchased and deployed new towers, enabling a cost-efficient, neutral-host model in which the towers could be shared by customers. The early low-band spectrum, below 2 GHz, made pedestrian and mobility services in urban, suburban and rural areas accessible. Mobile phones were less of a luxury as we moved to 4G and smartphones began to emerge. The introduction of 5G technology, coupled with massive MIMO, allowed the use of new mobile spectrum at 3 GHz mid-band and 28 GHz mmWave. Services were quickly extended to fixed wireless access (FWA) and future 5G standards will expand coverage using non-terrestrial networks such as high-altitude platforms and LEO satellites. Some of these capabilities still have a way to go before reaching the global marketplace, but we will soon see them become fully realized.
We might ask, what type of infrastructure, as shown in Figure 1, will we need in the future to maximize the availability of spectrum and device electronics for higher frequencies such as 3GPP’s frequency range 2 (FR2) (24 to 71 GHz) and 6G FR3 (7 to 24 GHz) and even sub-THz? How can we leverage 6G on existing towers for the mainstream rollout of population coverage and potentially integrated backhaul? One may also consider the local area potential of device-to-device or V2X sidelink in connection with reconfigurable intelligent surfaces. These can expand access to data-driven intelligent IoT services in cities. How do all these radio technologies play together cost-effectively and how do we enable future wireless infrastructure that will be even more resilient and more reliable?
Figure 1 Wireless infrastructure evolution.
Infrastructure investments are important to do most economically and we can see how critical these investments are when we look at the infrastructure evolution over time, as shown in Figure 2. With 4G deployments, we introduced OFDMA with two- and four-layer, single-user MIMO and fiber-fed remote tower-top radio heads. Decades ago, placing active radios at the top of towers was difficult, but now, it is a common practice. We replaced shelters hosting baseband equipment and radios with outdoor cabinets. In parallel, the backhaul started to improve with the use of more and more fiber. With 5G, cellular operators moved to support massive MIMO with active beamforming in the mid-band spectrum to leverage the large existing base of 4G macro towers. Smaller cells were required with the early availability of mmWave, but this technology was limited to providing better access in places like stadiums, some FWA and other limited hotspot environments to enhance the user experience.
Figure 2 Evolution of macro tower sites to 6G.
6G networks, when deployed using 3GPP Release 21 in 2029 and beyond, will require new radios operating on the same infrastructure with even higher mid-band and potentially sub-THz frequencies. It will drive another round of tower investment for new radio antennas, power amplifiers, filters and digital front-end radio processing. Infrastructure improvements to support legacy bands with 6G will require antenna upgrades and more advanced transceivers, together with support for open radio interfaces. Also, the architecture and functional splits between the tower, the base of the tower and the network will depend on the trend to standardize AI models for single-ended or end-to-end (device-to-network) and potentially new waveforms like orthogonal time frequency space modulation.
The range of capabilities we can enable on existing towers is critical to the 6G operator economics. Can we get 80 percent or more of the coverage from these higher mid-band frequencies to augment and extend what we do today with 5G at mid-band? Fixed wireless is increasingly a big part of the success of 5G, so how can we improve these services with 6G? Finally, one can envision existing towers with sub-THz radios for backhaul, FWA and sensing. Short, high bandwidth links open up the possibility to leverage our increasingly denser networks to enable a tower-to-tower mesh, as shown in Figure 3. Can the higher FR2 bands and beyond provide reliable links with larger bandwidths, bringing us new capabilities to allow sensing of the environment around a tower for detection and control of drones and other mobile platforms? Does wireless connectivity as an overlay to fiber backhaul networks improve overall resiliency for mission-critical applications?
Figure 3 Resilient edge networks.
In the wireless access world that exists today, operators take all the customer traffic from their specific sites and route the data to their core platforms for interconnection to the Internet and other telco networks, as shown in Figure 3. However, when looking at the future of enabling 6G edge applications from an API platform perspective, very few independent software developers will write a latency-sensitive multi-access edge computing (MEC) application that uniquely leverages only one access network or results in vastly differing performance across users due to varying routing and hops across multiple access networks. Developers need consistency for the system to scale, or they fall back to common solutions. High performance edge applications need to run in localized neutral-host locations.
Application developer revenues are maximized when they cut across a fully converged set of wireline and wireless access networks by operating in neutral colocation data centers. The challenge for the industry is the need to invest in the data center infrastructure in advance to support future low latency mission-critical or real-time inferencing applications. Performance dictates the need to peer or exchange access traffic horizontally, east to west, not simply south to north, to different processing locations by each operator. The traffic routing problem is solved if we could put in a 6G-enabled wireless mesh at the higher frequencies and use all the tower infrastructure to create another layer of resiliency on top of the existing fiber network, not to replace but to augment with a deterministic latency bound across multiple access networks for a subset of the traffic. We can make it both timely and cost-effective to bring traffic uniquely to a multi-MNO MEC hub site (e.g., edge aggregation site) and process applications for all users that require low latency, such as workloads requiring an AI inferencing model or agent.
Edge computing, where data processing occurs close to the source of data generation, goes together with 6G. By reducing the distance that data needs to travel to be processed, edge computing lowers the end-to-end latency and enables faster decision-making. This will be important while using machine-to-machine applications for which real-time data processing is critical, such as autonomous vehicles, drones, electric vertical take-off and landing aircraft and real-time video and sensing to improve safety in smart cities.
The future need for orchestrating a service employing specific AI agents, after moving from training to inferencing, will be spread throughout the infrastructure, from hyperscale data centers to devices. We need the AI orchestrator to piece together what workloads to run in which location. If you are trying to talk to a device that is not a smartphone but another input device to “help solve this problem,” is there a visual component? Is there an uplink challenge? How do I process this?
At American Tower, we are focused on leveraging our assets to answer those questions. We are working on a MW scale modular aggregation edge data center in Raleigh, N.C., with partners. We also seek to repurpose our older shelters and leverage them for local workload processing and data access. The data today is not available at local sites, so we need to add the local breakout and evolve to where the user plane function can deposit the traffic anywhere across the edge continuum with specific intent and purpose.
Despite the challenges that 6G will require, such as significant investment in infrastructure, including new antenna systems and the need for regulatory bodies to establish the allocation of frequencies to ensure network efficiency, the future is bright. 6G will change the landscape of communication, enabling faster, more reliable and more immersive connectivity than ever before. With advancements in AI, traditional and new radio band communications, sensing and edge computing, 6G will usher in an era of connected technologies that will enhance every aspect of our lives. 6G will open the door to greater digital and AI enterprise and consumer transformation in the coming decades.