Another interesting cellular technology that is gaining focus is the use of private LTE/private 5G in CBRS (Citizen Broadband Radio Service) spectrum by enterprises. It is an alternate wireless solution to the existing 802.11 Wi-Fi.
CBRS is an unlicensed frequency spectrum (known by band 48) from 3550 to 3700 MHz that is currently approved by FCC in US. This is shared among 3 tiers with incumbents being the highest priority tier used for US Navy/radar services that has the privilege to utilize the full 150MHz frequency space. This is followed by PAL tier that uses spectrum: 3550-3650Mz and has a reservation of 7 x10MHz channels. GAA can utilize the entire 150 MHz range, if no frequency slot is occupied by the above tiers, which is the case in most locations. All the enterprises that use private LTE belong to the GAA tier.
Features
- Utilize unlicensed shared frequency spectrum: 3.5 GHz (3550 MHz to 3700 MHz).
- 150 MHz spectrum band width
- Frequency spectrum coordinated by a centralized server called SAS (Spectrum Access Service)
Core Components
- SAS (Spectrum Access Service) – Centralized management cloud software that co-ordinates the CBRS spectrum use by GAA to make sure that the it does not interfere with the other higher priority tiers in that specific location.
2. CBSD Devices
- Category B – all the base stations/CBRS based APs with power of 30-47 dBm/10MHz mainly used for outdoor purposes. Operating between 3550 MHz and 3650 MHz
- Category A –devices with power 23-30dBm/10MHz for indoor use.
When we deploy any CBRS device (category A or category B) in an enterprise, it is required to register the CBSD to SAS by a CPI (Certified Professional Installer). The accuracy of data input during the registration process is important for SAS to allocate the right channel and power. For right reporting of the geographic locations. The accuracy should be up to +/-50 m horizontally and +/- 3 m elevation.
3. EPC (Evolved Packet Core)/ LTE Edge – manage all the base stations and client traffic within the network .
4. End user devices – client devices that are not base stations and do not communicate with SAS. It connects to CBRS (max power up to 23dBm / 10MHz
High level Deployment Architecture using Celona Product
- Identify the devices that support the CBRS technology. These devices usually have a CBRS SIM slot to insert the CBRS SIM. Celona SIM should be inserted on the end user devices. End devices that supports CBRS technology is listed in the link below from Celona:
https://docs.celona.io/en/articles/3484781-cbrs-capable-devices-in-the-market
- Celona AP must be registered to SAS by a CPI based on the location. SAS will allocate the frequency spectrum and power necessary for the private LTE.
- Celona APs acting as CBRS category A/B devices allow the EU devices to associate to them in the CBRS frequency.
- All the user traffic is tunneled from Celona AP to the Celona Edge that can implement QoS through feature called micro slicing and make routing decisions. Celona Edge is similar to the wireless controller in the Wi-fi infrastructure that manages all the Celona category A/B devices.
- Celona AP and Edge devices are managed through a centralized cloud server called the Celona Orchestrator.
Benefits of CBRS over Wi-Fi
- Longer range with lesser congestion/interference
- CBRS infrastructure controls and coordinates both client uplink and downlink traffic unlike Wi-fi infrastructure that does not have control over the client traffic.
- Receiver devices are more standardized with better quality chipsets and hence they can receive low quality signal with lower noise floor compared to Wi-Fi
- End user device association to CBRS APs are centrally controlled during hand over or roaming scenarios
- Better modulation technique: OFDMA is used here. Though, the same is used in 802.11ax, CBRS uses this technique more efficiently to provide better performance.
References
CTS 245: Celona Architecture and Live Demo – YouTube
CBRS and Wi-Fi: Friends or Foes? A Guest Webinar Hosted by Celona – YouTube
Webinar: CBRS Alliance Explains How to Deploy a Private LTE Network – YouTube
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