The Citizens Broadband Radio Service (CBRS) is Redefining Communications
We live in a data-driven era, where data has become a crucial resource for many businesses, equivalent to power, water, and heating/cooling utilities – commonly called the “fourth utility.”
With the increasing need for data, organizations are always looking for faster and more secure access to their information. Consequently, the U.S. Federal Communications Commission (FCC) has approved using Band 48, also known as CBRS, in response to these demands.
But what exactly is CBRS, and how can it benefit your organization?
What Is CBRS?
The Citizens Broadband Radio Service (CBRS) is a 150 MHz spectrum within the 3.5 GHz band, ranging from 3550 to 3700 MHz. Historically, this band was only sparsely used by U.S. federal government radar systems, a few fixed satellite receivers, and wireless internet service providers. However, with the growing demand for additional spectrum to manage the influx of new mobile users, the FCC has identified this underutilized band for broader use to free up spectrum for shared wireless.
To ensure commercial Access, CBRS is designed with a three-tiered spectrum-sharing framework.
The top tier is allocated to Incumbent Access, reserved explicitly for existing users of the band, such as the Department of Defense personnel and U.S. Naval Radar, who will receive permanent priority and site-specific protection.
The middle tier, Priority Access, is available to organizations that pay a fee for a Priority Access License (PAL), which can be purchased at auction with limited renewal rights.
The third tier, General Authorized Access (GAA), covers the remainder of the spectrum and is available for general use.
This three-tiered framework is managed through a Spectrum Access System (SAS), which protects higher-tier users from interference from lower-tier users, while optimizing the efficient use of available spectrum for all users.
By enabling private LTE broadband for commercial enterprises, CBRS will provide better coverage and capacity, benefiting organizations in various sectors.
Three Types of CBRS Users
Tier 1
Tier-1 users, referred to as ‘Incumbents,’ receive the highest priority in the 3550-3700 MHz band. These users include authorized federal users, Fixed Satellite Service (space-to-Earth) earth stations in the 3600-3650 MHz band, and temporarily, grandfathered wireless broadband licensees or WISPs in the 3650-3700 MHz band. Incumbents are protected from interference caused by Priority Access Licensees and General Authorized Access users.
Tier 2
Tier-2 users are known as Priority Access License (PAL) holders. These can be businesses, rural WISPs, and qualifying tribal lands. According to the FCC, “Priority Access Licenses (PALs) will be licensed on a county-by-county basis through competitive bidding. Each PAL consists of a 10 megahertz channel and is a 10-year renewable license. Counties are defined using the United States Census Bureau’s 2017 counties.”
Each county can have up to 7 PALs, and each license holder is entitled to a 10 MHz TDD channel. Due to the channel aggregation cap, a single license holder can purchase up to four 10 MHz channels, but no more.
The FCC requires PAL holders to meet substantial performance requirements by the end of the initial license term. PAL holders must protect Incumbent Access users and accept interference from them but receive protection from General Authorized Access users.
Tier 3
General Authorized Access (GAA) users have the lowest priority and do not need to pay to use the band. GAA users can access channels throughout the entire 3550-3700 MHz band. However, they cannot use channels currently in use by Incumbent users.
GAA users share 70 MHz with PAL users, subject to availability, as PAL users have priority. The remaining 80 MHz is reserved for GAA access, although PAL users can also use this part of the band under GAA provisions.
How Will CBRS Change Commercial Communications?
Increased Accessibility
The increased accessibility of CBRS marks a significant milestone for business enterprises. Presently, there is no publicly available broadband spectrum that private businesses can use, which forces some organizations to lease through carriers, requiring a multi-million dollar system.
Alternatively, other businesses rely on public LTE or WiFi to fulfill their business data needs. Although this approach enables mobile device users to accomplish tasks that previously required a computer or physical presence on the job, it has its own issues, including network congestion, weak signals in certain locations, and security concerns.
With CBRS, publicly available broadband spectrum is now accessible for the first time, significantly reducing the entry barrier for business enterprises. Unlike previous systems, it does not require organizations to purchase spectrum, making it a more cost-competitive option for broadband coverage. Organizations can customize the network to meet their unique coverage needs and expand or downsize the system as their business evolves.
More Efficiency
Compared to Distributed Antenna Systems (DAS) – networks of antenna nodes that provide wireless service within a geographic area or structure – the economics of CBRS technology are more efficient. Additionally, the speed and consistency of service are potentially more reliable than WiFi, possibly making WiFi obsolete.
Although WiFi has revolutionized wireless networking, it has disadvantages, including limited coverage and capacity, overly sensitive access points, and tedious sign-on processes. Ultimately, WiFi was not designed for complex commercial operations. CBRS overcomes these limitations and offers a more efficient option for large commercial enterprises such as airports and factories, providing comprehensive on-site coverage extending to every corner of the operation.
Ground-Breaking Advancement
One of the most revolutionary advancements introduced by the newly available private broadband spectrum access is the capability to utilize highly dependable LTE networks to support the expanding number of IoT devices. These devices, which include smart meters, real-time surveillance systems, and worker safety monitoring sensors, are becoming increasingly critical components of business operations, requiring constant, dependable broadband access. CBRS provides this, empowering organizations to leverage the potential of IoT.
Ultimately, CBRS allows for creating an affordable, private data network at a lower cost without the dependence on a wireless carrier. Looking ahead, CBRS and its limitless possibilities will drive automation, workforce productivity, efficiency, and safety – all of which are essential concerns for forward-thinking organizations today.
Advantages of CBRS
CBRS has been hailed as a catalyst for innovation across various industries and sectors, including agriculture, finance, healthcare (such as hospitals and home care), hospitality (including hotels), manufacturing, military, mining, oil, office buildings, corporate campuses, public agencies, public venues (like stadiums and entertainment venues), retail (such as malls and shops), supply chain and distribution (including warehouses and ports), transportation and transportation venues (such as airports and train stations), utilities, power generation, distribution, and many more.
While the CBRS industry is experiencing rapid development and changes in its device ecosystem, some uncertainties remain. For instance, questions about CBRS hand-off to cellular networks, the integration timeline of radio manufacturers (such as Ericsson, Nokia, and Samsung) for incorporating carrier signals into the CBRS band, or how E911 calls will be managed in the CBRS band, especially if the CBSD is voice-capable, still need to be addressed. However, the industry will likely resolve these issues because CBRS is poised to become a permanent fixture in the wireless landscape.
IIoT and Enterprise Applications
CBRS provides enterprises with the traffic management capabilities, capacity, low latency, reliability, and security of LTE (and eventually 5G), essential for Industrial IoT (IIoT) and other enterprise applications, including voice.
Standalone Deployment
Enterprises can deploy standalone networks not necessarily tied to a mobile operator network.
Control and Security
By deploying a private or neutral host network, enterprises can maintain control over the network’s architecture, performance, management, and security rather than relying entirely on mobile operators.
Simplicity
CBRS networks are less complex than large carrier-operated LTE networks, making them easier to deploy and operate.
Improved Propagation Characteristics
The lower 3.5 GHz band CBRS uses offers higher regulatory power limits and better RF propagation characteristics than the 5 GHz band, resulting in longer-range coverage.
Out-of-Box Solutions
CBRS small cell solutions are plug-and-play and do not require a carrier-grade core network. The CBSD includes all necessary network components and network configuration tools. Enterprises only need to handle RF planning and backhaul.
Reduced Complexity
CBRS simplifies LTE capacity expansion without the complexity of sharing the spectrum band with Wi-Fi, offering 150 MHz of sparsely used spectrum for LTE deployment.
Spectrum Sensing and Coordination
With three tiers of users, the question arises: how does a CBRS system sense, direct, and prioritize traffic correctly?
This is achieved through Spectrum Sensing and Coordination, a unique and vital feature of CBRS.
At the heart of spectrum sensing and coordination is the Spectrum Access System (SAS).
The SAS is a cloud-based service that manages the wireless communications of devices in the CBRS band to prevent harmful interference with higher-priority users, and the FCC has certified four companies – CommScope, Federated Wireless, Google, and Sony – as SAS Administrators to manage access to the band.
A CBRS device (CBSD) needs authorization from the SAS before it can transmit in the CBRS band. The SAS functions like a traffic controller or an orchestra conductor.
Tier-1, or Incumbent, users have priority access to the CBRS spectrum and do not require SAS authorization. However, the SAS must be aware of Tier-1 users’ activities to prevent PAL and GAA users from causing interference during their communication.
The SAS detects when Tier-1 users transmit with Environmental Sensing Capability (ESC) sensors. The ESC is a network of sensors that detects incumbent activity in the CBRS band, primarily along the coast, and relays that information to the SAS. Since the SAS cannot proactively contact a CBSD, the CBSD must initiate all communications. CBSDs communicate with the SAS using the SAS-CBSD API, while the Wireless Innovation Forum (WInnForum) sets the communication protocols between CBSDs and the SAS, which are implemented in the SAS-CBSD API.
There are two types of CBSDs:
Class A: Class A base station is typically an indoor or low-power outdoor small cell with a maximum power of 24 dBm (per 10 MHz) and a maximum EIRP of 30 dBm (1 watt). Class A CBSDs are similar to “enterprise-class” small cells.
Class B: Class B base station (CBSD) is designed for outdoor use and has a maximum EIRP of 47 dBm (50 watts). It is intended for fixed wireless purposes.
Block Diagrams of Private LTE Network and CBRS Through DAS
The eNodeB (eNB) is considered a CBRS device or CBSD – and the heart of a CBRS-based private LTE network.
eNDs are connected to the SAS server via a router and LAN. The router also serves as a pathway for the eNB or CBSD to communicate with the core network (EPC). If direct communication between the eNB and the SAS server is not possible, a Domain Proxy can be utilized. This proxy can communicate with the SAS on behalf of multiple individual CBSDs or CBSD network networks. Additionally, the Domain Proxy can enable legacy radio equipment in the CBRS band to interface with the SAS, ensuring compliance with Part 96 rules.
Private LTE Networks or dedicated CBRS networks enable organizations to implement use cases requiring secure, low-latency, and high-quality networks, such as video surveillance, critical communications, automated guided vehicle support, industrial automation, or remote equipment control.
CBRS Through a Multi-Carrier DAS
In a multi-carrier DAS, signal sources from Mobile Network Operators (MNO) are integrated at the head-end.
At a high level, the DAS head-end receives the RF signal from the MNO source, converts it to an optical signal, and distributes it via fiber to devices known as ‘remotes.’ These remotes convert the optical signal to an RF signal and distribute it to users through the antenna.
For a multi-carrier DAS to be compatible with CBRS, the signal must be processed both at the head and remote end. Additionally, antennas and other passive components must be compatible with the CBRS band.
If a remote output exceeds 23 dBm, it must be capable of communicating with the SAS server per FCC regulations. Future DAS architectures may handle this in two ways:
Allow the remotes to connect directly to the SAS server.
Use a Domain Proxy device, which can gather information from the remote electronics and communicate with the SAS server.
It is predicted that the use of Domain Proxy devices will increase in future DAS deployments.
It is strongly recommended that a CBRS-compatible DAS component, such as remotes, be OnGo certified when added.
How MNOs Use CBRS
CBRS promises to reduce customers’ dependence on Mobile Network Operators (MNOs) for wireless communications. Although MNOs will leverage the CBRS band, there are two ways in which MNOs can expand their capacity using it.
Supplemental Data Links
MNOs can utilize the 3.5 GHz GAA spectrum bands as supplemental data links, with a licensed band serving as an “anchor” carrier for control signaling and primary data transmission.
TD-LTE Technology
TD-LTE deployed on the CBRS bands can carry control signaling and data traffic across the shared 3.5 GHz spectrum.
In both scenarios, CBRS offers a higher network quality control level than Wi-Fi offload solutions. The availability of 10-MHz channels enables mobile operators to implement carrier aggregation, boosting peak speeds and overall capacity. PAL licenses, particularly for outdoor deployments, can ensure a guaranteed spectrum in traffic-dense areas.
Through PAL licensing, MNOs can secure up to 40 MHz of CBRS bands in strategic geographical locations. Additionally, operators can utilize additional CBRS bands on a GAA basis, leveraging extra spectrum resources to meet growing demands.
Important Entities
CBRS Alliance and OnGo
In 2016, six companies established the CBRS Alliance, which grew to over 100 members by mid-2018. The CBRS Alliance aims to support the common interests of its members, implementers, and operators by fostering the development, commercialization, and adoption of LTE solutions for the US 3.5 GHz CBRS band.
The CBRS Alliance created OnGo, which they describe as providing “uncompromised connectivity.” According to the CBRS Alliance, OnGo offers nearly limitless options for customization, allowing networks to be tailored to specific needs such as IIoT applications, in-building wireless, or connectivity in public spaces. Practically, OnGo can be seen as a certification program—a set of standards for performance and interoperability that ensures the seamless integration and deployment of OnGo wireless devices and solutions.
WInn Forum
WInnForum, short for the Wireless Innovation Forum, is an industry-led group that sets requirements and protocols for using the CBRS band. Its members include SAS administrators, CBRS equipment manufacturers, network operators, and training program administrators such as Google.
Four Myths About CBRS
MYTH: CBRS Is 5G
FACT: CBRS can be leveraged to support 5G technology
5G represents the fifth generation of cellular technology, delivering faster speeds and enhanced network flexibility. Meanwhile, CBRS is a distinct spectrum within the broadcast band and a fundamental component in supporting 5G. The operation of 5G necessitates substantial amounts of spectrum, and CBRS can facilitate the increasing requirements for broadband and forthcoming 5G technologies.
MYTH: Spectrum Access Will Be Difficult
FACT: Spectrum Access Will Be Open And Easy
CBRS operates on a three-tiered spectrum authorization framework.
The first tier, known as the Incumbent Access tier, is exclusively allocated to authorized federal users and grandfathered Fixed Satellite Service users who are currently operating within the band.
The second tier is the Priority Access tier, which consists of Priority Access Licenses (PAL) that can be acquired through an auction process with limited renewal rights. However, it’s important to note that the Priority Access tier offers no right to exclude others.
The final tier is the General Authorized Access (GAA) tier, which is open to all users, including carriers, non-carriers, enterprises, residences, and private citizens. The GAA tier can utilize up to 150 MHz of the spectrum, with a minimum of 80 MHz guaranteed.
MYTH: Carriers Will Use Up The CBRS Spectrum
FACT: Three Tiers Of Spectrum Will Ensure CBRS Access
Major telecom carriers may turn to CBRS to augment their capacity and support the push for 5G. However, the three-tiered spectrum authorization framework ensures fair Access. The Priority Access tier, available for auction to the highest bidders nationwide, will likely attract these carriers.
Nonetheless, the General Authorized Access (GAA) tier remains available for other users, including carriers, non-carriers, enterprises, residences, and private citizens. It’s worth noting that if a company purchases a Priority Access tier and doesn’t utilize it, the spectrum becomes available for others to use, preventing companies from hoarding spectrum.
MYTH: Incumbents Will Impact Effective Usage
FACT: Designated Spectrum Will Safeguard Open Access
Some have expressed concerns about potential interference or exclusion from the 3.5 GHz band due to the current use by the military and satellites. However, these incumbents only utilize the band in range of the U.S. coasts on a sporadic basis. Furthermore, modern directional RF antenna technology can minimize the chances of interference with the incumbents. As they only occupy the lower 100 MHz of spectrum, an additional 50 MHz of spectrum is available for other users.
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