CBRS and the Monster Under the Bed

August 1, 2017
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Shared Spectrum strategies, like the USA Citizens Broadband Radio Service “CBRS”, generally will have incumbent usages within the spectrum that will be either technically accommodated or moved in the spectrum planning and implementation process. The accommodation process is to prevent negative effects on both the incumbents, and the new residents.

In the context of CBRS, the US Navy has radar systems that operate across a big part of Band 48. From this US Navy presentation:

The AN/SPN-43C Radar Set is an Air Search Radar (ASR) used for Aircraft Carrier and Amphibious Assault Ship Air Traffic Control, used on LHA, LHD, and CVN type ships.

Because these systems are woven into the electronic war fighting fabric of the US military, they will not be altered. But, the good news is CBRS enabled RAN equipment, as a new resident of the spectrum, is designed to avoid conflict with radars in coastal areas, and some inland areas where they may be used. There are identified coastal port areas in the CBRS spectrum plans that clearly identify where these radars are expected to regularly operate.

What’s the Monster Under the Bed? It’s this: the mis-information on these radars, and their “disastrous effects” have caused some in the RF planning community to think CBRS is not viable as a national strategy due to the risk of service outages when ships fitted with these radars arrive in a coastal port.

So, let’s grab our flashlight, peek under the bed, and hunt for the Monster. As part of the hunt, we’ll document radar technical capabilities, and shipboard operations.

Relevant technical capabilities:

  • Operating frequency range: 3500-3650 MHz
  • Transmission bandwidth: 6 MHz (Google presentation)
  • Operates at 10 Mhz increments across spectrum
  • At irregular intervals, will move to different frequency

Shipboard operations:

  • Radar is subject to mechanical wear (the antenna weighs 1.66 tons, and rotates at 15 RPM) so it’s idle when there are no flight operations
  • Flight operations, that require this radar to be active, will occur within range of coast
  • Radars will occasionally transmit in port as part of routine maintenance activity


With these technical and operational details defined, it’s apparent that things are not bleak for CBRS in coastal areas where naval radar systems will operate.

This is a brief comparison of spectrum of naval radar to CBRS:

  • Only 100 MHz of the 150 MHz assigned to CBRS overlaps with radar
  • When the radar operates in it’s lower 50 MHz range, it does not overlap CBRS
  • CBRS channels are 10MHz wide with PAL range of 3550-3650 MHz and GAA range of 3550-3700 MHz
  • GAA channels in 3650-3700 MHz range will not be disturbed by radar activity
  • PAL channels (3550-3650 MHz) completely overlap with radar range
  • The radar’s 1.6 MHz transmission bandwidth on a 10 MHz increment can result in an “incumbent protection event” affecting up to two CBRS channels

After chatting with a number of engineers about the above summary, it was explained that while up to two channels could be affected by each active radar, the Spectrum Access System “SAS”/ Environment Sensing Capability “ESC” does not just blanket move each Citizens Band Service Device “CBSD” (CBRS radio) to a different channel. The SAS/ESC does heavy lifting by determining appropriate individual changes for each CBSD that is in-scope for the incumbent protection event.

For CBSDs on impacted channels, the SAS will run interference calculations to determine how each one must be affected to protect the incumbent. The SAS could send commands to the CBSD to have it move to a different channel, or reduce its power. Or, the SAS could determine that no action is necessary. This implies that in a given port, many CBSD’s that are farther from the active radar or shielded from it behind other buildings will operate undisturbed even though they are occupying the same channel(s).

In summary, we think that the “Monster Under the Bed” of naval radar that has caused some angst for RF people disappears when we shine the light of decent information on it.

Sleep well, my friends.

– Art King, SpiderCloud Wireless, Director of Enterprise Services & Technologies

Twitter: @ArtKingg
LinkedIn: https://www.linkedin.com/in/kingart
Visit our Enterprise IT site @ http://SpiderCloud.com/Enterprise

Private LTE? What are you talking about???

July 18, 2017


Shared Spectrum strategies like the USA Citizens Broadband Radio Service “CBRS” unlock the pent up demand for Private LTE. CBRS reduces the barriers to entry for enterprises that, in the past, had a tough time accessing spectrum for private cellular.

So, why would anyone ever want to build Private LTE? Well, enterprises with wireless requirements for deterministic timing, controlled bandwidth, true mobility, long signal reach and privacy have not been able to meet them. The system architects in these enterprises view Private LTE operating in CBRS as the emergent ideal solution. We have witnessed that progressive enterprise IT architects envision their wireless ecosystem as a balanced diet of enterprise-owned Wi-Fi and LTE that can seamlessly satisfy the present and future needs of business applications.

As we move to the enterprise market from the mobile operator market, how each Private LTE system networks its radios together are front of mind for the enterprise. Enterprises are seeking Private LTE architectures that deploy like Wi-Fi and leverage the enterprise-wide Cat5e cabling and Ethernet/IP transport infrastructure in-place today.

We believe that SpiderCloud E-RAN is uniquely architected for maximum synergy with today’s enterprise networks, and their future directions. The other competing Radio Access Network “RAN” products that an enterprise can acquire to create their own Private LTE instance all have their own unique architectures that will fail the enterprise screening process in many ways.

What questions should responsible architects ask of Private LTE network vendors?

  • Is the network built on standard Ethernet/IP technology? If not, it requires the construction of another parallel infrastructure. Example: the network is proprietary technology or a DAS.
  • Can the network share the existing Ethernet/IP transport network? If not, it requires the construction of another parallel infrastructure. Example: If it uses CPRI over Ethernet. Sharing not possible due to massive traffic load generated on the Ethernet.
  • Is the network approved for connection to any mobile operators? Any IT application that plans to use the macro-cellular (outdoor) network, must be approved for a connection to the desired mobile operator. If the vendor cannot list any of the four Tier-1 USA mobile operators as approved for connection, that’s a problem.
  • Can the network be shared by Private LTE, and one or more mobile operators? CBRS spectrum can support multiple service providers, so make sure the network can!
  • Is network capacity added in common headend or just at the spot where it’s needed? Spot capacity is much lower cost than addition of a base station in the headend.

A network vendor that cannot answer yes to all five simple questions can still build out a Private LTE network for the enterprise.

But, it could mean:

  • Extra construction cost of parallel physical transport
  • Unplanned space and HVAC requirements in MDF/IDFs
  • Lack of agility in handling network expansion
  • Impossible to add connection to a mobile operator(s)
  • Capacity issues that are expensive to remedy

IF YOU ARE NOT IN AN ENTERPRISE IT ROLE, PLEASE SKIP THIS PARAGRAPH! As an enterprise architect in a multi-national, prior to joining SpiderCloud, I urge enterprise IT people who are researching the addition of Private LTE to their wireless ecosystem to get educated, and look before you leap. Cellular is a totally different universe than Wi-Fi, and you have to ask the right questions. Many vendors can make a sale and install a Private LTE system for you that won’t support your future needs. Failure to ask the right questions in researching the solution space, or in an RFP could result in your enterprise painting itself into the corner.

We have authored a comprehensive Private LTE white paper for enterprise IT application, network and telecom architect readers that explores business demands, vertical market applications, a CBRS primer and solution architecture overview. Get it now!

– Art King, SpiderCloud Wireless, Director of Enterprise Services & Technologies

Twitter: @ArtKingg
LinkedIn: https://www.linkedin.com/in/kingart

Visit our Enterprise IT site @ http://SpiderCloud.com/Enterprise