There is a promised nirvana from installing a single set of CBRS small cells in a building where everybody can seamlessly access cellular service at much higher performance and lower cost. But this involves sharing the available capacity. We explore four different options to achieve that and discuss some of the implications.
1. Private Standalone CBRS
Once FCC certification of SAS providers and CTIA testing of small cells has been completed (timeline H1 2018), it will be legal and possible to operate your own private CBRS small cell network in the US. You’ll need to use data dongles until compatible smartphones are available sometime later next year.
Such standalone networks will have their own core network functionality, handling all aspects of registration, authorisation, authentication, data session management and if appropriate billing. There are several software companies with core network software suitable for this today, such as Athonet, Druid and Quortus. There are also tens of potential small cell vendors who have demonstrated interoperability with SAS providers – just look at the list of partners on their websites and/or the CBRS Alliance membership list.
SIM card authentication doesn’t just allow the network to verify the identity of the user, it also enables the smartphone to check the validity of the network it’s trying to connect with. This avoids the security risk of connecting to spoof networks. It also means that operators (who control the SIM card configuration) also determine which networks you can connect with. When you are roaming abroad for example, there’s a preferential list of which networks to search for although more sophisticated users may choose to manually override the first choice.
This means that for a truly independent Private LTE network, you may want to issue and provision your own SIM cards. This can be done using easily available computer equipment or ordered in batches from a SIM manufacturer, but is an overhead. What’s more awkward is that users/guests can’t just continue to use their existing SIM cards – they’ll need to swap them and/or use a second phone.
The alternative is to authenticate using a different mechanism that doesn’t require co-operation from the host network operator, such as used for Wi-Fi.
These approaches may be quite acceptable for devices used only onsite, especially data dongles for fixed equipment, but would restrict widespread adoption for casual use. Either there will need to be a new option on smartphone menus that allows bypassing this security check, or a potential method for operators to agree to enable access in their SIM cards.
You could think of it being similar to using Facebook or Google to login to a website. There is little operational cost to facilitate the feature and they gain insight into where and when their customers are connecting to other networks.
When connected, it would be similar to a roaming arrangement but without call forwarding for incoming or CallerID on outbound calls. The private network name rather than the major network might appear on the top left corner of the screen.
It’s unclear how much interest operators have in supporting this approach today. They could view it in a similar way to Wi-Fi Hotspot 2.0 roaming without the revenue opportunity or they could see it as a threat because it offloads traffic that would otherwise generate additional revenue.
2. Direct install by single MNO or MVNO
This would use a single set of CBRS-only small cells connected via S1 interface directly to a single operator core network. It would only be available for use by the customers of that network who have CBRS compatible smartphones.
Systems would be implemented by existing authorised installers, ensuring compliance with planning, wiring and technical requirements of the operator.
Users would see the same major network name on the top right corner of their phone and as far as they are concerned it’s just another part of the network. Operators will want confidence that service quality will be improved to avoid tarnishing their brand. I’ve heard some operators set higher quality/performance targets for indoor systems than outdoor, expecting fewer call drops/session disconnects when moving around inside buildings.
One question is why would an operator deploy CBRS small cells rather than re-using their existing licenced spectrum indoors? CBRS will initially be compatible with fewer smartphones, reducing the return on investment. One answer could be to use CBRS mainly as a speed boost via carrier aggregation. Data traffic will be seamlessly offloaded to CBRS where available, otherwise remain on the existing network. It’s just another frequency to deploy. This should greatly improve performance indoors but could still cause voice service outages in the deeper/underground parts of buildings without any licenced spectrum coverage.
I’d also include deployment by an MVNO – a service provider that today would not have any spectrum or radio network deployed. Cable TV companies (MSOs) such as Charter have significant plans to deploy CBRS for which they will pay minimal licence fees, offloading traffic from their host mobile network. In some cases, these MVNO/CBRS companies might even allow seamless roaming from the major networks into buildings and areas where service would otherwise be deficient. It could be embarrassing for a major cellular network to have poorer coverage than an MVNO which enhances the same basic service with small cells in underserved areas.
3. Direct install for sharing between multiple network operators
Sharing a single set of small cells rather than multi-band, multi-technology, multi-operator DAS may be attractive to some operators due to the much lower cost. If a single CBRS deployment could serve the customers of multiple operators, reducing the cost significantly, then this should become even more commercially attractive. The downside is that they would have to be happy about sharing and confident that their brand quality would not be negatively impacted.
There are scalability concerns for this type of installation directly driven by network operators – they may not be able to cope with large number of individual building deployments involving many different businesses, owners and regional building regulations.
4. Neutral host
A business model that has been discussed many times up to now is that of a neutral host that acts as a consolidator, aggregating traffic from many smaller businesses and buildings to provide supervision and connection to the major networks.
These would approve and authorise individual CBRS buildings for use, perhaps in a similar way to some of the larger Wi-Fi ISPs. The logo appearing on the phone may be theirs or the business owners, and they would supervise adequate QoS on behalf of the network operators.
Administering fair sharing policy
A common question where a single radio resource is shared is how to ensure there is a fair sharing policy. This needs to be administered within the radio network rather than the core, because it is close to the point of consumption. Radios generally don’t know who is connected and can’t differentiate between high value vs low value use. They can only see the overall load being requested and can throttle back high demand during peak use.
We’ve all experienced the wide range of speeds and performance from radio connections, from the trickle of painfully slow data download to super-fast instant response. Many factors contribute to that, of which the demand vs capacity curve is the most critical. Often in-building wireless systems are most constrained by their backhaul connection, which should be the easiest to resolve.
Regular review of the performance of each building installation will be important, with action taken to enhance capacity in the light of inadequate resource.
There are different options for CBRS to be deployed within buildings.
Fully seamless service will require some co-operation and co-ordination with all the major cellular networks. While in the short term, standalone or directly deployed CBRS installations are more likely, in the longer term I would expect to see several neutral host companies expanding to satisfy the need.
MVNOs, such as the Cable TV companies, are a wildcard that could establish a bridgehead in the in-building market.