What is a neutral host network?

April 7, 2022 | Neutral Host Networks (NHNs) are a hot topic these days, particularly in the CBRS-based network context. This week I’ll define what neutral host is; next week I’ll get into more of the nuts-and-bolts, including MOCN.

NHNs imply shared resources. Distributed antenna systems (DAS) can be a type of neutral host network when the site and antennas are built, owned, and/or maintained by a third party and then leased to mobile network operators (MNOs). The MNOs (who own most spectrum) attach their cellular signal sources (base stations, small cells, central BBUs) to the DAS and operate their own network over the shared (“neutral”) infrastructure. Typically, there is redundant cabling and equipment, and DAS head ends comprise entire rooms that not only need power but cooling, as well.

So, in this scenario, the only things being shared are the antennas, the room(s) in which the equipment is deployed and maybe the conduit through which the cabling run. Implementations vary. Each MNO independently manages the various network parameters of the frequency bands they own, which means the radios, etc. After all, their customers transition from the outdoor, macrocell-based network to the in-building network, so the MNOs want that transition to be seamless and the in-building experience to be at least as good as on the outdoor network.

As they are discussed today, Neutral Host Networks extend the sharing concept to the radio and transport infrastructure level. So, rather than parallel sets of radio infrastructure and cabling out to shared antennas, MNOs would share radio and transport resources with the other operators on the network. However, the MNOs would still control their own baseband processing which, along with SLAs (at minimum), would enable MNOs to have the same network management visibility and control capabilities as they would have on a conventional DAS. If MNOs cannot obtain end-to-end control over their subscribers’ network experience, then they are unlikely to “attach” to this type of NHN.

In the U.S., CBRS spectrum allows a NHN service provider, for example, to go from building to building with offers to deploy and operate in-building NHNs. They would then sell that capacity to whoever wants it. In this scenario, MNO subscribers (with CBRS-capable devices) would basically roam from their usual licensed bands onto the in-building CBRS network. Again, there would likely be per-MNO SLAs, etc., involved. Note that while a NH licensed band network is feasible, a NHN provider would probably want commitments from MNOs before investing.

The NHN concept can be extended to outdoor networks (e.g., in underserved areas). It can also be used in conjunction with unlicensed bands. Moreover, the use cases could focus on connecting machines and/or applications (e.g., precision agriculture, smart building, security, etc.) rather than people.

Next week, I’ll start going into some of the technologies that can help enable NHNs such as 3GPP-defined specifications (including MOCN) to other approaches such as Open RAN and virtual RAN.

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