Last week a CW (Cambridge Wireless) Small Cell Sig event posed the question; “Interoperability of Small Cells and the Existing Cellular Networks – What’s the Hold-up?”

With presentations from Forum members Alcatel Lucent, ip.access, JDSU and NEC, along with other interested parties, the presentations took a look at rollouts to date and the history of small cell and macro network interoperability to see if we’re really facing a problem and what progress has been made so far.

What was clear from all of the presenters is that interoperability means different things to different people. For some it’s about interference management and remote coordination, for others it’s about extracting information about how subscribers are using the cell and for others it’s about support for the back-end systems that need to support both small cells and the macro layer.

What do the operators want?

Thanks to the changing dynamics of mobile networks and the versatility of small cells operators are also finding themselves faced with a problem – do they follow the single or multi-vendor approach to networks? While each offers its own positives, the potential for innovation in the multi-vendor network is enormous, but its success depends on multi-vendor interoperability on key interfaces.

At the event Alessandro Bovone from EE had a call to action for the industry – don’t expect us to solve any problems, you need to come to us with the solutions. Operators expect small cells to deliver at the same level as a macrocell and against the KPIs that operators measure their networks against.

We’re already seeing small cells being used in multiple environments and work by the Small Cell Forum, amongst others, has gone a long way to addressing the challenges with interoperability. As Nick Johnson of ip.access pointed out in his presentation, many of the laws-of-physics challenges have been solved, so what’s left?

Public interfaces needed – not private

While the work of the Forum has addressed plenty of significant barriers to adoption, some still remain and the recommendations of the Forum and the NGMN have yet to be followed. Looking back at other technologies and approaches it’s clear that any private interfaces will simply not do – operators don’t want to deal with multiple proprietary approaches.

The work of the Small Cell Forum’s working groups, supported by testing at regular Plugfests, has removed many of the potential issues or challenges that can hold back the adoption of a multi-vendor network, but there’s more to be done.

Hope on the horizon

It used to take operators months to deploy a new cellsite, but it’s now possible for them to install a small cell and have it live within the same morning.  This is thanks to not just the work of the Forum but also the NGMN, 3GPP and many other groups who have developed standard interfaces and approaches in use today – but our work is not done. We need more operators, vendors and technology companies to get involved with the work of the Forum and others to define and recommend the next set of interfaces and standards. It’s clear that operators are looking to move to multi-vendor HetNets and it’s now down to us to make it easy as possible for them to do so.