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PMN: It’s all about Spectrum, Spectrum, Spectrum!


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In real estate it's all about location. In the world of Private Mobile Networks (PMN), the location is still important, but spectrum choices are even more important to be able to have consistent delivery, meeting your requirements across geographies. 


It’s paramount to understand that different spectra have different propagation (reach/behavior) and that unlicensed spectra such as CBRS are not universally available in all countries when piloting a blueprint PMN to be rolled out in multiple countries. Furthermore, there are a number of different “flavors” (architectures) of PMN to choose from with different characteristics and associated price points.

A PMN can come in many different “flavors” 

In its most basic, and typically most cost-effective form, a PMN can consist of transport purchased on an existing public mobile network from an established Mobile Network Operator (MNO) with a service level agreement.

In a 5G network, this would most likely mean buying a logical network “slice”. In its most advanced form, this would mean having a full stack of all necessary operational systems on site to support fully autonomous operations. The most common options include (but there may be in between options from the provider):

  1. The PMN is delivered as a VPN over an existing MNO network
  2. The PMN is delivered as a VPN over an MNO network with site specific operator additions (site specific antennas/base
  3. The PMN is delivered with site specific operator additions (site specific antennas/base stations) and a local break out of data
  4. The PMN is delivered with a full stack of on-premise servers/systems to be able to operate as an autonomous network

A rule of thumb is that if option one above costs 1X, then the cost of option four above is typically 8-10X. Hence, it’s important to understand current and foreseeable SLA requirements on the PMN to make an
informed architectural decision.

What are the differences between different spectrum bands on a high level? 

Please refer to the chart below to see the relationships of spectra use cases that are discussed throughout the rest of this document.

broken image

When there is a choice of which spectrum to use, it’s basically a compromise between coverage and speed (as well as to some extent also latency and high number of endpoints). The high-level and not so scientific explanation is:

  • The higher the spectrum band, the shorter the reach. Lower spectrum bands also permeate walls better than higher spectrum bands. Very high spectrum bands require line of sight to work properly.
  • On the other hand, higher spectrum bands areusually available in wider channels which enable higher throughput. As each base station is handling a relatively smaller area, it also supports a denser implementation of endpoints.

This really means that you want different spectra for different use-cases. For example:

  • When planning to cover a big area like a large open-pit (overground) mine, sea or airport in a cost effective way, you should prefer lower spectra, typically low bands in the range 600-900 MHz to minimize the number of base stations needed. Typical data speed is 30-75 Mbps.
  • When planning to cover a medium-size building, such as a factory where the use case calls for low latency and high reliability or an arena full with people, you should prefer spectra in high bands, 7 GHz and above, typically bands in the range 24 GHz to 40 GHz. Data speed is usually 1 Gbps or higher.
  • Mid bands use spectra in the range 1 GHz-2.6 GHz and 3.5 GHz - 6 GHz which are optimal for covering campuses consisting of multiple buildings extending to several blocks in size. Typical data speed is 100-250 Mbps. C-Band, which is frequently referenced, resides in 3.7 GHz - 4.2 GHz in the mid band and CBRS (available in the US) resides in 3.55 GHz – 3.7 GHz (LTE Band 48 / 5G band n78).

The challenge when dealing with global roll-outs is that only operators (and equipment manufacturers working closely with operators) can provide the same (or close to same) spectra across geographies.

When looking at license free spectra, bear in mind that only about 22 countries currently have some kind of license-free spectra. 20 countries currently offer license-free mid bands. Another ten have high-band
offerings, but only eight also provide license-free mid bands. These numbers are expected to increase over time, as more and more regional spectra harmonization efforts are under way. The current offerings by region have many variations:

  • In Europe there is a tendency to provide LTEB and 43 / 5G Band n78 (except the UK that uses different bands altogether!) in the mid band, and the amount of spectrum varies from 40 MHz to 240 MHz,
    typically in the range 3.4 GHz to 3.8 GHz. In the high bands, it’s 5G band n258 and the amount of spectrum varies from 400 MHz to 850 MHz, typically in the range 24.25 GHz to 27.5 GHz.
  • In APAC there is a tendency to provide 5G Band n79 (Japan also offers spectrum in LTE band B41) in the mid band, and the amount of spectrum varies from 100 MHz to 300 MHz and typically in the range 4.6 GHz to 4.9GHz. In the high bands, it’s 5G band n257 and n261 and the amount of spectrum
    varies from 400 MHz to 900 MHz, typically in the range 27.95 GHz to 29.5 GHz.
  • In the US, the allocated spectrum, CBRS, is in LTE band 48 / 5G band n78 and resides in the mid band, 3.55 GHz – 3.7 GHz (150 MHz).

The mid-band spectrum offerings in Europe and US are fairly comparable while the mid-band spectrum offerings in APAC are in significantly higher ranges, about 1 GHz higher than Europe and US
which means propagation will likely be somewhat different. When doing research for this article, I ran across this Ericsson Whitepaper that I found very helpful and detailed.

Who can provide a PMN 

The typical providers of a PMN include MNOs, Managed Service Providers (MSPs), Systems Integrators (SIs), Equipment manufacturers like Ericsson and Nokia, and in a limited way Hyperscalers like AWS on a regional basis.

Don’t forget about LTE 

Even if the primary initial use case for investing in a PMN works fine on 5G alone and supports the target spectrum band, consider secondary use cases that may benefit from LTE as well at a low additional investment level.

PMN as a Managed Service or Self-Managed  

Most organizations don’t really want to become mobile operators, and having to master all the associated skills. In fact, many MNOs outsource the operation of their network to managed service providers like
Ericsson and Nokia. Contracting a PMN as a managed service makes a lot of sense in most situations.


Start by trying to identify all of the use cases that will drive the PMN requirements. Ensure that the prospective vendors can show a roadmap for how their technology can be extended in phases to support the full scope. Keep in mind that PMN technology is evolving quickly and that some requirements may be dependent on a future 5G release. Architect for modularity to insulate as much as possible against lacking vendor long term viability and ensure the selected vendor(s) can support across the entire target footprint and provide access to required spectrum.

It may look attractive for organizations with a CapEx-heavy tradition to buy and operate their own PMN infrastructure. However, for most organizations, it’s usually a better and lower risk option to buy PMN as a
managed service from a MNO or managed service provider with strong operator relationships.


Leif-Olof Wallin

Advisor | Lionfish Tech Advisors | Enterprise Mobility & IoT | Lion Briefs Contributor
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