Everything to know about CBRS - the advantages & is it right for you?

CBRS (Citizens Broadband Radio Service) is a new spectrum allocation made available nearly three years ago by the FCC (North America). Its rules make it attractive for private enterprises. The spectrum can be used for both accessing a private wireless network as well as one or more MNOs (Mobile Network Operator, e.g., AT&T, T-Mobile, Verizon) networks using off-the-shelf equipment. 

Access for private enterprises to purchase using off-the-shelf equipment offers the lower cost of ownership similar to Wi-Fi combined with the performance and convenience of a modern cellular service. Gobs of information is available about CBRS and we will not be repeating that here. However, our purpose here is to provide a simple explanation as to why an enterprise might consider installing a CBRS system. 

DAS (Distributed Antenna System), an inferior alternative—the incumbent.

Poor cell service inside buildings is common. Building construction materials are to blame; the closer to stray from exterior walls will further degrade cellular signals emanated from outside cell towers. New construction is even more challenging. Newer wall & window materials drastically attenuate radio signals to the point where the only way to make a call is to walk outside.  

In the past, the only way for an enterprise to provide reliable cell service inside is to have MNOs put cellular equipment inside a building. The radio signals from this equipment are distributed throughout a building with dedicated fiber, RF cable, fiber/RF converters, RF splitters and antennas. This is called DAS. Although there have been many improvements of DAS over the years, the technology has some glaring shortcomings. 

• DAS equipment is expensive. The systems require expensive radios, dedicated fiber, thick RF cabling and antennas distributed throughout a building. 
• Connections to each MNO requires a separate contract which can take one or more years to execute. 
• MNO equipment is on premise. When things go wrong it is not always clear where the problem lies and who is on the hook to fix it. 
• DAS installation and maintenance must be to performed by authorized installers. Enterprises effectively have no visibility, control, or ability to actively troubleshoot issues on DAS. 
• DAS cost of ownership is high for both the enterprise and the MNOs. Purchasing, installing and maintaining a DAS is usually borne by the enterprise, but each MNO must purchase, install and maintain their own equipment and separate high-bandwidth Internet circuit to plug into the DAS. Ultimately, higher operational costs are all reflected in MNO rate plans. 

• Designing a Wi-Fi network for voice traffic servicing mobile users requires strong wireless engineering expertise. RF expertise to optimize AP-to-AP roaming is not trivial. 
• Calls initiated inside a building using a private Wi-Fi network cannot seamlessly handoff to an MNO network when leaving a Wi-Fi enabled building for certain voice applications.
  
  
  
  

The Advantages of CBRS Technology

With CBRS you have the advantages of a private voice network with a system that was designed for voice. Like DAS, it also allows enterprise customers to access the MNO networks from inside buildings. 

CBRS systems have better RF performance than Wi-Fi. The coverage area for a CBRS AP is at least 4 times that of a Wi-Fi AP due to several factors.

• CBRS APs and phones operate at a higher RF transmit power level than Wi-Fi. 
• CBRS can operate at lower data rates and higher coding gain which allow for communications at lower signal levels at the edge of the APs cell boundary. 
• Unlike Wi-Fi, the decision for handoff is made at the network level, so that network congestion and other factors can be considered. 
• AP placement is less fussy with CBRS than Wi-Fi given this improved performance. 
• QoS (quality of service) performance is more strictly controlled in CBRS systems versus Wi-Fi.
  
  If the system is required to provide enterprise network communications, CBRS has lower cost of ownership than DAS. A CBRS system can be used to setup a private voice/data network without the recuring MNO charges. (e.g. industrial, warehouse, etc. use cases) 
  
  The latest 5G features are available in CBRS systems which include higher data rates, lower latency, and better handoff performance. 

• Generally speaking, only newer (from 2020 on) smart phone devices work with CBRS. 
• CBRS does not eliminate the need for Wi-Fi. Many phones and IoT devices require Wi-Fi for indoor use. This is not expected to change. 
• Connection to the Cloud is required. The system needs to coordinate with a Cloud-based SAS (Spectrum Access System) to coordinate usage of the CBRS spectrum. 
• A GPS timing standard and PTP (Precision Timing Protocol) network equipment are required to distribute a common timing standard to all the CBRS APs. 
• There are a limited number of CBRS system manufacturers. The list is growing. 
• The part where private CBRS systems connect to MNOs has not been finalized in many cases. T-Mobile is on board; AT&T is only approved with one partner at the time of this writing and Verizon is, in our words, a hold out. 

Logically speaking, MNOs can benefit greatly from CBRS because it lowers stress on their wireless networks, eliminates cellular equipment installations & maintenance in DAS, reduces indoor cellular augmentation to months—not years, and generally is a much more simpler process for all parties. 

The tide is turning, but the process is not complete. If you are planning a DAS, building a new building, are interested in a private CBRS network for specific devices or simply want to learn more, please contact us. We’d love to understand your needs and explain if CBRS is a good fit or not for you. 

Authored by Tom Head, Shawn Jackman.