This article is part of the TechXchange: 5G Infrastructure.
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What you’ll learn:
- How 5G connectivity is disrupting nearly every industry.
- Why legacy DAS infrastructure needs to be upgraded or replaced to support 5G service.
- How 5G frequencies and RAN architecture complicate in-building coverage planning, and how to address these challenges.
Since mobile network operators (MNOs) started rolling out the first 5G networks roughly five years ago, this latest mobile technology continues to experience a meteoric rise. In fact, 5G is on record as scaling faster than any previous generation of mobile wireless technology.
In North America, 5G connections already account for a market penetration of 36% of the population, and worldwide 5G networks are on track to add nearly a billion new connections each year to reach 6.8 billion by the end of 2027.
Despite this obvious success—or perhaps in part because of it—5G technology is still facing several hurdles to be overcome and challenges to be addressed. This is particularly true when it comes to mobile communications that either originate or terminate indoors.
The Rise of 5G
For the most part, the unprecedented scale and impact of 5G is due to the disruptive nature of this technology. Thanks to the ability to deliver higher capacity, faster data speeds, and lower-latency connectivity, 5G enables a wide array of new capabilities, such as:
- Enhanced Mobile Broadband (eMBB): More throughput at faster speeds for enhanced data rates, expanded coverage, and improved data-sharing efficiency.
- Ultra-Reliable, Low-Latency Connections (URLLC): Near real-time interaction and controls allow the network to support new use cases in manufacturing, healthcare, and military applications.
- Massive IoT and M2M Communications: The ability to support many more devices per unit of area than 4G/ LTE while enabling longer battery life in connected devices.
- Network Slicing: Virtual logical networks, or “network slices,” within a single physical network allow segregation of targeted use cases with varying levels of service and security.
These capabilities, in turn, enable mobile network operators (MNOs), enterprises, and manufacturers to develop innovative services with the power to revolutionize nearly every industry—from healthcare, industrial manufacturing, and retail to logistics, real estate, hospitality, and education.
With 5G eMBB capabilities, virtual-reality (VR) and augmented-reality (AR) technologies can be leveraged to create immersive experiences for telehealth, scientific research, education, and premier guest experiences in the hospitality industry and throughout event venues.
Likewise, capabilities such as massive IoT connectivity, network slicing, and intelligent positioning enable realization of mission-critical Industry 4.0 use cases, including predictive maintenance, manufacturing automation, real-time asset tracking, and occupational health and safety, implemented with high accuracy and low latency.
These 5G advances are due to fundamental network architecture changes made as the technology evolves from 4G, as specified in the 3GPP standards. Although these evolutionary transformations enable significant improvements in mobile network speed, quality, latency, and reliability, they also affect how 5G networks perform indoors.
Indoor 5G Access
As more consumers and businesses worldwide adopt 5G, there are mounting expectations of seamless 5G connectivity everywhere, all the time. This includes indoors where roughly 80% of all mobile voice and data traffic occurs. Whether in an office building, hospital, airport, subway, hotel, or stadium, subscribers demand always-on mobile service in today’s hyper-connected world.
Moreover, 5G data connectivity has become essential to day-to-day business for many organizations. For example, a growing number of healthcare facilities have adopted a bring-your-own-device (BYOD) policy. This means that to reliably access electronic healthcare records and application data, physicians and staff need secure and reliable connectivity to at least three of the major MNO networks. And in offices or other commercial properties, building owners rely on 5G and the IoT to automatically control building systems such as security cameras, lighting, and smart thermostats.
Yet, even before the evolution to 5G, legacy mobile network service was typically unreliable inside most modern buildings. Energy-efficient Leadership in Energy and Environmental Design (LEED) building materials, congested network traffic, and nearby obstructions that block radio frequency (RF) transmissions all contribute to spotty in-building coverage and dropped calls.
To address these connectivity issues, many building owners and network operators have traditionally installed distributed antenna system (DAS) platforms to deliver and amplify mobile network signals throughout buildings and campuses. Now the transition to next-generation 5G is creating new in-building connectivity challenges.
5G Connectivity Complexity
As demand for mobile data capacity escalates, the Federal Communications Commission (FCC) continues to make new RF spectrum available to alleviate bottlenecks, including both frequency 1 (FR1) bands below 6 GHz, and frequency 2 (FR2) bands above 6 GHz. However, many of the new frequencies used for 5G are even less capable of penetrating buildings than previous spectrum deployed for 3G and 4G/ LTE networks.
Initial allocations of FR2 mmWave frequencies between 24 and 40 GHz didn’t provide an economical solution for wide-area 5G deployment. Because these high-band frequencies offer such poor propagation over long distances, MNOs need to build very dense networks to avoid coverage gaps, making these frequencies impractical outside densely populated urban areas.
However, the 5G mmWave frequencies are also easily blocked by most objects and building materials, including energy-efficient glass. Thus, service can be unreliable both indoors and outdoors in built-up city neighborhoods.
More recently, the FCC made available new mid-band spectrum for 5G, including the C-band (3.7 to 3.98 GHz), Citizens Broadband Radio Service (CBRS, 3.55 to 3.7 GHz), and the spectrum dubbed “Auction 110” by the FCC (3.45 to 3.55 GHz), which is also known as Lower n77. These mid-band frequencies offer an optimal mix of speed, capacity, and coverage.
In turn, most MNOs are taking advantage of them to build out their networks more cost-effectively and enhance wide-area 5G capacity and speed for a better user experience. Plus, because the CBRS spectrum includes some general authorized access (GAA) channels that are unlicensed, other organizations are also using this spectrum to build private 5G networks for a range of enterprise and industrial applications.
Nonetheless, this new mid-band spectrum occupies a higher frequency range than traditional mobile network spectrum, limiting transmission distance and signal strength. As a result, although Tier 1 MNOs are rolling out more wide-area 5G networks using mid-band frequencies across the U.S., these frequencies still can’t penetrate building materials, leaving many building tenants, visitors, and employees without ready access to 5G services indoors.
Building Out In-Building Coverage
As network managers and building owners plan their in-building 5G strategy, the first step is to identify whether existing DAS platforms can be upgraded. With a modular, multi-band DAS, support for the new 5G frequencies can be easily added to legacy systems without requiring complete infrastructure replacement.
However, the RF characteristics of new mid-band spectrum should be carefully considered when planning upgraded deployments. This may require RF benchmarks, site surveys, updated network designs, and approval from the local mobile service providers.
Mid-band signals tend to be attenuated by metal, concrete, low-emissivity glass, and other building materials. So, not only are these frequencies less likely to provide in-building service from outside networks, but these transmissions also can be impeded by interior walls and furniture.
The C-band, for example, offers just one-fourth the signal propagation characteristics of legacy mobile communications bands. (Fig. 1) This means that additional reconfiguration of existing in-building network infrastructure is needed to provide sufficient coverage and capacity indoors with mid-band 5G spectrum.
Moreover, although the C-band spectrum offers much greater capacity due to increased channel sizes up to 100 MHz, the wider channels consume more radio power, which drastically reduces the effective coverage area. In fact, indoor C-band coverage per antenna is roughly 15% of what’s possible with previous frequencies at the same power level.
That means an antenna providing around 1,000 square feet of coverage for a 4G 20-MHz channel in the legacy Advanced Wireless Service (AWS) band would only cover a little more than 150 square feet with a 100-MHz channel in the C-band, assuming a typical office environment with sheetrock walls (Fig. 2).
As a result, achieving the same indoor coverage with C-band requires a higher effective output power from the antenna, versus legacy mobile communications frequencies. To overcome these obstacles, most existing 4G systems will need amplifiers that provide 4X to 10X more output power for mid-band 5G to match the existing footprint.
Yet, a higher-power configuration may not be feasible if the legacy system already uses high-output power amplifiers. If this is the case, the best practice may be to install a fiber-to-the-edge overlay system to support specific coverage requirements of the new 5G frequencies. In this way, fiber-to-the-edge technology carries voice and data transmissions to the edge of the DAS network, enabling faster speeds, higher bandwidth, and lower latency at each access endpoint throughout a building or campus.
Plus, as technology convergence drives more fiber throughout the entire communications network, a common, end-to-end fiber infrastructure offers a scalable evolution path to support more secure and efficient building management systems or IoT applications, such as security monitoring, energy management, smart locks, or motion-activated lighting.
This installed fiber also facilitates future communications technology upgrades. These include additional DAS capacity overlays to enable support for future frequency bands as the FCC releases more spectrum and MNOs turn off previous mobile generations.
Sophisticated link-budget analysis tools and experienced DAS professionals can help network managers weigh the various factors unique to each in-building deployment to enable optimized 5G coverage and capacity. Recommendations to ensure high quality for maximum service availability might include adjusting power output, deploying fiber-to-the-edge, or replacing existing antennas and coaxial splitters.
Timing is Everything
In addition to signal propagation considerations of new 5G frequencies, changes in radio-access-network (RAN) architecture complicate the delivery of 5G connectivity indoors. One of the most substantial transformations from 4G LTE networks is the introduction of the 5G New Radio (NR) air interface standard, designed to enable high-capacity throughput for significantly faster and more responsive 5G mobile experiences.
The 5G NR air interface supports high-bandwidth applications such as streaming video and VR, low-bandwidth massive IoT connectivity and M2M communications, and mission-critical use cases like vehicle-to-everything (V2X) communications and VR-assisted telemedicine, requiring very-low-latency transmissions.
To bring about greater capacity and lower latency, this new air interface enables 5G networks to support a combination of FR1 and FR2 frequency bands, whereas traditional mobile communications traffic primarily used the FR1 bands. Most of these new 5G frequency bands employ time-division duplexing (TDD), rather than frequency-division duplexing (FDD), to provide more contiguous spectrum and support larger channel widths.
The introduction of TDD means that timing synchronization is critical in 5G networks to avoid interference between uplink (UL) and downlink (DL) transmissions. Moreover, because 5G devices can only identify and connect to mobile networks within 3GPP standards-defined delay windows, delay management becomes a key consideration as well.
Consequently, when it comes to managing DAS platforms to support 5G service, failure to properly synchronize timing and minimize delays will result in poor in-building network performance and user experience. On the plus side, the increased scheduling flexibility enabled by TDD bands means that more slots can be assigned for either UL or DL transmissions per channel. This allows network managers to configure the in-building 5G network to meet the specific needs of a venue or service.
Promise of the 5G Future
As 5G adoption continues to accelerate, this disruptive technology is empowering an array of exciting new capabilities. Innovative 5G services are revolutionizing industrial and manufacturing processes, healthcare procedures, scientific research, business practices, and our day-to-day lives.
And the frenetic pace of mobile network evolution doesn’t appear to be slowing down anytime soon. In some regions, 5G is just starting to gain momentum, while MNOs in other parts of the world are demonstrating 5G Advanced and 6G technologies. The common denominator is that consumers and businesses alike expect ubiquitous, always-on connectivity everywhere.
New mid-band spectrum presents an ideal blend of frequency characteristics to enhance wide-area network coverage, capacity, and speed, helping to fulfill 5G’s true potential. But when planning in-building DAS deployments, be sure to consider how the new 5G RAN architecture and frequency allocations will impact the effective coverage reach and capacity to ensure optimized quality of service for an ideal 5G experience.
Read more articles in the TechXchange: 5G Infrastructure.