With an increasing number of users, devices and networks being deployed, wireless spectrum is straining – especially unlicensed or “free” spectrum such as WiFi. CBRS is a new spectrum sharing scheme that is being introduced in the US and other parts of the world, and it can remove spectrum barriers for Private LTE networks to enable them to affordably and effectively replace enterprise WiFi.
For most organizations, the single biggest challenge to setting up a wireless broadband network is access to spectrum. To get access to spectrum in the past, you had to either:
- buy spectrum at auction for dedicated access, free from interference
- make use of unlicensed spectrum, without protection and having to deal with unknown interferers
However, there is now a third option: shared spectrum via the Citizens Broadband Radio Service (CBRS). CBRS can make spectrum for Private LTE networks as accessible as Wi-Fi and has the power to revolutionize wireless networks for enterprises.
But before we move on to possible use cases, let’s look at what CBRS is and how it works.
What is CBRS?
With spectrum becoming ever scarcer as more users, devices, and apps require connectivity, the United States Federal Communications Commission (FCC) recognized the need for additional spectrum and authorized the full commercial deployment of the CBRS (Citizen Broadband Radio Service) in early 2020.
CBRS is a new band of spectrum made available for wireless communication. CBRS uses the 150MHz slice of spectrum in the 3.5GHz band and operates between 3550MHz to 3700MHz. Previously, this band was exclusively used for military radar systems and aircraft communications, but since it was underutilized, the FCC decided to make the 3.5GHz band available for wireless broadband commercial shared use.
What sets CBRS apart from traditional spectrum is its advanced, three-tier spectrum framework allowing unlicensed/lightly-licensed/licensed spectrum to be dynamically shared. This means organizations can set up private wireless broadband networks without the need for expensive spectrum licenses.
SAS (Spectrum Access System)
The spectrum allocation is handled by a central database called the SAS (Spectrum Access System). It coordinates spectrum access among the incumbent military radars, satellite earth stations, and new commercial users, and is tasked with protecting the higher-tier users from lower-tier users and optimizing efficient use of the available spectrum in the CBRS band for all users.
When a user/device wants to use the CBRS band, it needs to be requested via the SAS cloud-based system. If the spectrum is free in the desired geographic location, the SAS will grant the request, and when the user/device is done with the channel, it is returned to the pool the SAS draws from to grant further requests.
Three Tiers of Spectrum Access
CBRS utilizes three tiers of spectrum use rights: Incumbent users, Priority Access License (PAL) users and General Authorized Access (GAA) users.
- The Incumbent tier is reserved for users that traditionally use the 3550-3700 MHz range. This group mainly includes the Navy as well as commercial fixed satellite stations
- The PALs tier is for users that purchase CBRS spectrum licenses at auctions. The FCC will auction seven 10-MHz blocks in each county in the United States. The licenses are for 10-year terms. The licenses are purchased on a per-county basis, and bidders are limited to 40 MHz in any county
- The General Authorized Access (GAA) tier is unlicensed spectrum that users can access for free
CBRS Infrastructure and User Devices
CBRS enables devices such as smartphones to access networks operating on CBRS spectrum. Its infrastructure consists of two main parts: Citizen Broadband Radio Service Device (CBSD)/Access Points and Devices/Endpoints.
The CBSD or Access Point is an eNodeB: a base station capable of performing network control functions and creating mobile network coverage. In CBRS, these come in two categories:
- CBSD Category A: Includes access points and low-power cellular base stations that can operate either indoors or outdoors with lower antenna gain than Category B devices.
- CBSD Category B: These devices are for outdoor use only with higher antenna gain
The CBRS radio interface is exactly the same as for LTE at other frequencies, supporting voice, text, and data services with seamless mobility. This means CBRS end user devices can be typical consumer devices like smartphones, tablets, but also IoT devices. The end user device can have maximum transmitting power/antenna gain that’s similar to regular smartphone devices on commercial wireless licensed frequency bands.
Elements of a CBRS System
A CBRS system comprises the following elements:
- Spectrum Access Systems (SAS): Centrally coordinates access to the shared spectrum, enforcing priorities and modelling the RF environment
- CBSD (CBRS eNODEB): Radio nodes operating in the CBRS band, must coordinate with a SAS in order to transmit
- Evolved Packet Core (EPC): CBSD aggregation and proxy functions for large networks; can be integrated with an EMS/NMS or be standalone
- CBRS UE: A user device such as a handset or an IoT element that uses the CBRS frequency band in connection with a CBSD
CBRS Use Cases
Large enterprises have traditionally deployed Wi-Fi networks to satisfy the growing demands for wireless broadband data. However, it has been a poor substitute for seamless mobile voice services indoors. CBRS offers secure connectivity, high speeds data rates and the quality of an LTE network regardless if it’s in-building or outdoors.
An opportunity to create a private LTE network to run enterprise or venue-specific applications on mobile devices of consumers or workers enables tremendous flexibility – and allows enterprises to tap into broader device and app store ecosystems that already exist.
For instance, a large corporation can run a secure enterprise CRM and communication tools on workers’ mobile devices through a private LTE network at enterprise campuses. In another example, a heavy industry company can set up a private LTE network at a remote mining site and run industrial IoT applications on LTE devices.
A recent demo from Nokia, Qualcomm and Alphabet showcasing a live 360-degree VR streaming from a race car is yet another example of new user experiences that can be enabled on high-capacity private LTE networks leveraging the CBRS bands.
Cable Operator MVNO
CBRS is a great option for new entrants like cable operators to build out an LTE network and is a compelling traffic offload option for cable operators looking to enter the mobile wireless industry with a Mobile Virtual Network Operator (MVNO) strategy.
LTE service across both host macro network and owned CBRS small cell network may simplify network integration efforts and will likely result in more predictable user experience than offloading to Wi-Fi. Since cable operators do not yet own much licensed spectrum, this is a big upgrade from Wi-Fi.
Wireless capacity deployment
CBRS spectrum can also be used to increase the existing wireless capacity over small cells in dense urban markets, banks, universities, concert halls, sports arenas, parks, shopping malls, hotels, or conference centers, for example.
As you can see, CBRS will open up new spectrum for almost anyone, and coupled with the fifth-generation wireless technology standard (5G), it will unfold a new wave of developments in wireless communication in the years to come.
The Tait CBRS portfolio leverages award-winning LTE technology to deliver new private, public and hybrid solutions that maximize spectral efficiency, revolutionize cost models and dramatically reduce deployment time and risk.
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