Citizens Broadband Radio Service (CBRS) is one of the hottest topics in 5G recently. Many consider it a game-changer in next-generation wireless networks, with benefits that cut across LTE and Wi-Fi. From fixed wireless access to mobile offloading, CBRS could be a cost-effective way to expand coverage and fill existing gaps. A popular use case is enhancing coverage in congested areas such as urban settings and sports stadiums. Another popular use case is fixed wireless access (FWA) for residential, commercial, and municipal broadband. Instead of fiber to every home or office, FWA decentralizes the last-mile internet for greater reliability and affordability.
Regardless of the application, CBRS’ mid-band spectrum is promising on many fronts. Because of its 3.55GHz to 3.7GHz range, CBRS strikes a good balance between data transmission rate and wireless range. But for those evaluating CBRS for the first time, the rules of engagement can be confusing. For example, CBRS requires spectrum assignment at the time of usage. And under certain scenarios, spectrum access could even be blocked. Therefore, if you are evaluating CBRS for your network, here are common pitfalls to know before moving forward.
Pifall #1: Thinking CBRS is Completely Unlicensed
Despite popular assumptions, CBRS is not an unlicensed spectrum. Technically, CBRS is a lightly licensed spectrum with shared access across three different parties. These include Incumbent, Priority Access License (PAL), and General Authorized Access (GAA) users.
Of the three parties, incumbents have the highest priority. These include the U.S. Navy and commercial satellite companies. After that comes exclusive PAL usage based on spectrum auctions in 2020. And finally, there is GAA for public use. Taking a step back, navigating access across different parties and priority levels may seem complex. However, certified devices and systems coordinate proper access in real-time. In fact, all CBRS deployments in the U.S. require certified Citizens Broadband Radio Services Devices (CBSDs). Furthermore, these CBSDs require registration with a cloud-based Spectrum Access System (SAS). The SAS acts as a traffic controller for the shared spectrum, ensuring proper access to the right users at the right time.
Because CBRS is a shared spectrum, CBSDs in the U.S. must be registered with a SAS to ensure proper function and access.
Pitfall #2: Failing to Analyze Existing Spectrum Usage
Despite the general availability of the spectrum, it is always best to ensure capacity before designing and deploying new CBRS networks. This provides a general understanding of the potential overcrowding of the spectrum and can prevent interferences and even outages. Therefore, use a spectrum analysis tool to comb through the intended network deployment locations. And since SAS providers monitor the CBRS spectrum, some may be able to provide this analysis. The current list of certified SAS providers includes Federated Wireless, Google, CommScope, Amdocs, Sony, and Key Bridge.
A note on spectrum availability: Even without the complete assurance of spectrum assignment, there is a wide and increasing spectrum that’s available for GAA. For example, incumbent commercial satellite companies will likely reallocate from CBRS to another spectrum in 2022. Furthermore, grandfathered CBRS licenses and exclusion zones will continue to decline in 2022. And although CBRS PAL auctions ended in August 2020, commercial PAL networks do not affect the GAA channels. That’s because 80MHz of the total CBRS spectrum of 150MHz is reserved for GAA, which should be sufficient for most applications. The net impact of CBRS’ wide spectrum and declining incumbent use likely means greater spectrum access for GAA going forward.
While CBRS is not ‘off-the-shelf,’ it offers a cost-effective solution that lowers the barrier to entry for new market entrants like WISPs.
Pitfall #2: Limiting CBRS Networks to Macro Cells
Designing CBRS networks with traditional macro-cell architecture will not work as effectively as they did in prior-generation networks. This is due in large part to adjacent bands like C-Band, which overlaps with CBRS in the 3GHz to 4GHz spectrum. Popular among mobile network operators, C-Band has higher power transmission limitations than CBRS. As a result of the power imbalance, CBRS is more likely to suffer from interference.
To minimize CBRS interference, it’s better to leverage small cell networks. As with any small cell network, RF spectrum planning is especially important for proper coverage. RF planning starts by analyzing the number of end-users, devices, and throughput speeds. It also includes assessing device types, their expected mobility, and the local environment. Meticulous planning and network simulations will help ensure proper CBRS coverage under varying circumstances. Note: if you are deploying a CBRS network on properties you do not own, it’s best to lock in potential sites ahead of time. This will minimize deployment bottlenecks common to site acquisition and permitting phases.
CBRS Checks Off Many Boxes
In conclusion, while CBRS may not be a straightforward solution, it checks off many boxes for a wide array of applications. Furthermore, certified devices and centralized access systems eliminate the need for complex homegrown systems. But regardless of devices and systems, successful wireless networks begin with RF spectrum and network planning. Therefore, if you’re evaluating CBRS for an upcoming network build, Airwaive is here to help. Our free RF planning and automated site acquisition platform streamlines the process. We are passionate about wireless and look forward to partnering with you, so click on the button below to schedule a call with the Airwaive team.