Managing the CBRS Spectrum
With radio spectrum in short supply and many more service providers looking for innovative ways to access this scarce resource, Citizens Broadband Radio Service (CBRS) arrives just in time to help address the growing need for wireless connectivity. But access to the 150MHz of ‘fast track’ band must be carefully managed, albeit autonomously, to ensure incumbents are protected and other users experience optimum performance.
In the first two blogs in this series, we introduced the concept of CBRS and some of its many diverse use cases. In this blog, we take a closer look at the CBRS radio spectrum and the role that the Spectrum Access System (SAS) plays in managing access to it.
The CBRS spectrum
CBRS is a new approach to spectrum management being introduced by the FCC. The CBRS radio spectrum is a 150MHz band stretching between 3550-3700MHz. The CBRS framework is arranged in three tiers in order of priority, with Tier 1 (incumbents) at the top followed by Tier 2 Priority Access License (PAL) and Tier 3 General Authorized Access (GAA).
Incumbent users are given the highest priority without being affected by other users of the spectrum. Incumbents include the US military with shipborne radar systems operating in the 3550-3650MHz band and other ground-based military radar systems operating in the 3650-3700 MHz band. Such users do not use the spectrum intensively, which is why 3.5GHz is ideal for spectrum sharing. In addition, while shipborne radar is most prevalent along the east and west coasts of the USA, this is also where the highest density of the population lives, thereby placing greater demand on CBRS spectrum. This is one of the main reasons why the FCC devised an active access system to protect incumbent users from interference, while enabling other operators to share the spectrum.
Access to the spectrum for tier 2 (PAL) and 3 (GAA) users is controlled by the Spectrum Access System (SAS), with access being granted according to the radio spectrum usage in the locality at the time.
To protect high-priority users, incumbents are monitored by an environmental sensing capability (ESC) that detects incumbent radio activity in a particular geographic region. When radar is detected, the ESC alerts the SAS, which in turn, inhibits other CBRS devices (CBSDs) from operating in the same region and frequency channel (which could cause interference).
Other Tier 1 incumbents include receive-only satellite earth stations, which currently operate in the 3600-3700 MHz band. Since PAL and GAA users are not allowed to operate around these sites within a defined wireless protection zone, an ESC is not required. In addition, many wireless internet service providers (WISPs) also use the CBRS band between 3650-3700 MHz. These users are referred to as “grandfathered” incumbents and will gradually transition to become PAL or GAA users over a five-year period. There are thousands of these networks, and operation will continue to be allowed under CBRS until 2023. Activity of these users is also not monitored by ESCs.
Tier 2 and 3 access
Tier 2 PAL operates over the lower 100MHz of the band from 3550-3650MHz, and licenses are granted to operators for up to 4 channels through a spectrum auction. PAL users have a higher priority over GAA users but in both cases their spectrum access can be suspended if a Tier 1 incumbent requires the channel. PALs are each assigned to a 10MHz channel and are geographically limited to a specific region (one or more census tracts) for a three-year term. PAL licenses are limited to a maximum of 70MHz (7x 10MHz channels) in any one census tract.
GAA is the bottom tier of CBRS and provides access to anyone. GAA users may operate anywhere over the entire band but they have the lowest priority and do not have interference protection. Tier 3 users are licenced by rule and may be inhibited from operating if they risk interfering with PAL users or incumbents. Registered CBSDs can request use of specific frequency channels via the SAS but access will depend on a number of factors, which can change over time. The SAS uses information from multiple sources to make this calculation including other CBSDs, radio propagation models, incumbent activity via ESCs and FCC databases.
In this way, spectrum management becomes autonomous and access to the 150MHz of CBRS spectrum is optimized. This significantly increases the number of concurrent users able to access the same radio spectrum with low interference between them.
Amdocs SpectrumONE enables this shared spectrum approach by providing shared spectrum services to service providers wishing to use the CBRS spectrum. These services include: managed access to the spectrum, interference supervision, incumbent protection and channel management. By managing the spectrum for the CBSDs, Amdocs SpectrumONE enables transmission in the 3.5GHz spectrum, thereby ensuring users have access to the capacity needed. In upcoming posts we will take a closer look at the SAS and ESC and the essential functions they perform within the CBRS solution, as well as what Amdocs SpectrumONE can provide to users.
Learning to share CBRS in the 3.5 GHz band changes how we use spectrum, Senza Fili
CBRS Information and Standards, Wireless Innovation Forum Spectrum Sharing Committee
Citizens Broadband Radio Service (CBRS) Shared Spectrum: An Overview, Federated Wireless
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Faster 5G rollouts: High risk – great rewards!
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Life is often about high risks and great rewards but being well prepared with the right tools and approach is essential to avoiding disaster.
For most service providers, modernizing and upgrading networks to 5G can mean navigating difficult hurdles. But at the same time, it’s an opportunity to embrace many new challenges. Whether it’s rolling out 5G, refarming spectrum for more efficiency, collocation, or just swapping out tired or redundant network equipment, the rewards outweigh the risks.
According to GSMA, the number of unique mobile subscribers will reach 5.9 billion by 2025 -- equivalent to 71% of the world’s population -- and two thirds of mobile connections worldwide will operate on high speed networks – 4G and 5G. Mobile operators will invest $0.5 trillion in mobile capex worldwide between 2018 and 2020 to support customer migration and further drive consumer engagement in the digital era. The winners will be those who can transform the fastest, while still improving customer experience.
But racing to roll out 5G and its services also means service providers will need to do everything they can to avoid negatively impacting quality of service such as increased call drops, handover failures and impaired data rates. The process of upgrading live networks is an inherently high-risk activity with return on investment tightly linked to service quality and rapid deployment. Delays in rolling out the new technology can increase costs and impact revenues.
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5G’s promise to meet connectivity demands begins with network design!
A quality network design ensures optimal use of wireless spectrum while delivering a significantly improved customer experience that reduces churn.
Familiar with this Bugatti Veyron Super Sport? It’s easily recognizable and the quality is undeniable. But have you ever stopped to consider that quality begins with the design.
When quality is embedded into the design, it tends to follow through the entire lifecycle which is likely to result in exceptional customer experience. This also applies to digital networks.
With the anticipation of 5G devices and applications, service providers are under even more pressure to deliver new services, greater capacity, faster connections and exceptional service. They need to improve their service agility to stay ahead of the game but designing and optimizing a 5G network can be challenging if you aren’t equipped with the right tools, techniques and expertise to achieve it fast.
A recent ABI Research study forecasted the in-building wireless market will more than double in revenue by 2020 to $9 billion. Subscribers expect operators to provide coverage when and where they need it most like inside sports venues, transportation hubs, retail stores and universities. Poor coverage results in poor customer experience, which could be avoided with better network optimization.
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CBRS: Reasons to take advantage of the shared spectrum space
CBRS has several characteristics that make it attractive for multiple use cases.
Propagation – Since CBRS uses an actively managed spectrum access system, it can use terrain and radio propagation data to control how devices make use of the shared spectrum. This increases efficiency by enabling many more devices to operate simultaneously across the same radio spectrum while minimizing interference between them.
Cost – Because of the way the CBRS spectrum is licensed and controlled, it makes a much more affordable network for small scale and new entrant operators for both indoor and outdoor use. Priority Access Licenses (PALs) are limited to a 3 or 6 year duration, are restricted geographically, and there is no guarantee of renewal. So, this helps avoid license monopolies by any one operator and keeps license costs down.
Rapid access – New operators no longer need to wait for license auctions. Tier 3 General Authorized Access (GAA) is licensed by FCC rules where operators are permitted to use any part of the 3550-3700 MHz band not assigned to a higher tier user. GAA users can simply deploy a device and turn it on to register with the Spectrum Access System (SAS) to become fully operational.
Greater capacity – CBRS enables more capacity for individual CBRS devices (CBSDs) by optimizing spectrum access and ensuring devices are not subject to radio interference. Individual operators can utilize concatenated channels (up to a maximum of 40 MHz for PAL users) to increase available bandwidth.
Security and reliability – LTE based CBRS provides an industry proven solution for secure and reliable wireless data communications.
CBRS use cases include (but are not limited to):
Last mile access networks – CBRS provides a convenient way to offer wireless ‘last-mile’ access especially for some types of rural broadband services, where laying fiber can be prohibitively expensive. This is often called Fixed Wireless Access (FWA).
LTE network densification – For many operators, building out the network to provide more capacity around traffic hotspots can be challenging. CBRS enables many more small cells to be deployed cost effectively in busy public areas such as railway stations and shopping malls.
In-building (LTE) femto cells – CBRS has defined two classes of device known as Class A and Class B, with the main difference being their RF power levels. Class A devices are low power (EIRP <1watt) and have a relatively short range by comparison to Class B devices (EIRP <50watts). Because Class A devices have reduced propagation characteristics with lower interference, they are well suited for indoor coverage and floor-by-floor applications.
Internet of Things (IoT) – IoT requires high numbers of connected devices operating across high density networks. Applications such as Smart Home, Connected Office, Smart City, and Industrial IoT all depend on device connectivity over a wide area at an affordable cost. IoT devices often only need occasional network access and CBRS can offer a solution for IoT connectivity due to its autonomously managed access system. This is being promoted by the Industrial Internet of Things (IIoT) Coalition.
Low range small cells – New entrants such as multiple system operators (MSOs or cable companies) are looking for cost effective ways to deploy their own LTE networks to compete with mobile network operators. CBRS offers a realistic alternative for new entrants to deploy their own radio access networks using small cell technology. For example, Comcast, a member of the CBRS Alliance, has requested a license to test wireless networks for both fixed and mobile access in the Philadelphia area using CBRS technology. Meanwhile, Verizon has been proactive in testing both indoor and outdoor small cells that will operate in the 3.5 GHz spectrum bands, and its first use case will be outdoor small cells used to offload traffic from lower spectrum bands to improve the user experience.
Wireless backhaul – Large numbers of small cells and wireless access points need to be connected back to the core network without the need to deploy expensive fiber. Line of Sight (LoS) and Point to Point (P2P) backhaul networks can offer a practical solution where a CBRS radio spectrum could be utilized.
Venue or stadium networks – Many venue owners are considering CBRS to provide their own access networks as an alternative or extension to distributed antenna systems (DAS). The National Football League (NFL) for example, has applied for a license to test CBRS at their NFL team stadiums in the U.S.
Neutral host RAN – A neutral host network provider can bridge the gap between mobile operators and enterprise organizations who don’t want to manage the complexity of their own wireless networks. Neutral host providers can make use of a CBRS spectrum to offer access to multiple operators over small scale networks within large public venues, university campuses and enterprises with limited IT resources.
Enterprise private LTE networks – Many large organizations such as hotels, airports and railway stations are looking for ways to deploy their own privately managed LTE networks. Due to its low cost, low interference and high bandwidth, CBRS can provide the solution. Examples include healthcare, manufacturing and transportation hubs such as the city and port of Los Angeles where a private, wide area and highly secure wireless network is essential.
Although our list here is not exhaustive, it provides an example of the many varied use cases, which CBRS can support through its innovative approach to spectrum sharing. In our next blog, we will discuss the CBRS radio spectrum and take a closer look at the Spectrum Access System (SAS).
Learn more about Amdocs SpectrumONE service for CBRS.
CBRS: New Spectrum and Flexible Indoor and Outdoor Mobile Solution, Mobile Experts
Learning to share CBRS in the 3.5 GHz band changes how we use spectrum, Senza Fili
NFL getting into the CBRS game files for proof-of-concept testing at stadiums, Fierce Wireless
Comcast eyes 3.5Ghz CBRS for both fixed and mobile applications including commercial handsets, Fierce Wireless