Two companies have independently raised the profile of how to manage truly large scale small cell deployments. Some issues aren't so apparent with smaller or trial sized rollouts. I spoke with experts from Airvana and XcellAir to learn about some of characteristics required and potential future features foreseen as small cells become more widespread and they more closely interwork with Carrier Wi-Fi.
Airvana is one of the few companies that can claim to have a truly large scale femtocell deployment. As one of the leading femtocell suppliers to Sprint, who boasted having more than a million femtocells in their network in 2012, they've dealt with the "growing pains" of managing on such a large scale. That's about 30x more than the 38,000 cellsites in Sprint's Network Vision plan, which some forecast might double with urban small cells.
Such a large disparity in scale leads to radically different approach to configuration and management, with many manual processes needing to be automated.
With multiple femtocell vendors present in networks, it's best if you can drive these from the same management system. Airvana has experience of configuring both its own and another vendor's small cells. While the open TR.069 standard makes this compatible, inevitably there are some tweaks required to support proprietary features. They launched a new Device Management System at Mobile World Congress which brings this expertise to any large scale small cell deployment, regardless of equipment vendor.
Rapid Activation and Commissioning
Important capabilities to manage any small cell deployment include:
- Downloading and updating operating software
- Security management, typically certificate based and may involve tokens directly stored within the hardware chips
- Determining operating parameters, such as permitted frequencies, power levels, spreading code, Cell ID and emergency call routing
These automate most of the installation process, so that little or no manual intervention is required. Enterprise and urban small cells may require some on-site testing and commissioning, especially where tuning to optimise interworking with the existing macrocell network is required.
As a deployment grows, additional gateways are added in different locations. You would typically expect to start with two (for redundancy) and expand to distribute the load over time. Large numbers of installed small cells would then be "re-parented" to be handled by the new gateways by sending new configuration parameters. When you are moving tens of thousands of devices around at a time, this has to be done in a controlled way to avoid signalling storms that overload the gateways and core networks.
Airvana's system can do this by state, postcode or other parameters and sequence the migration over a number of hours. Parameters defining where emergency calls are routed, range of frequencies available all depend on the location of each cell.
We've discussed the various components of Self-Optimising Networks before, where both Distributed SON (D-SON) and Centralised SON (C-SON) may work together.
Small Cell vendors themselves may offer D-SON capabilities, while several third parties offer independent C-SON solutions. A number of vendors offer both, but this may be tied to their own products.
Small Cell management systems are a good central point for SON to connect through. Operational data reported from the live network can be uploaded and new configuration parameters and constraints defined.
Airvana import details of the macrocell network into their system and use their own software to determine the configuration to work within that framework.
Adding Carrier Wi-Fi and LAA to the mix
XCellAir, a spin-out from Interdigital, view the solution space to encompass both Wi-Fi and Cellular.
They have their own in-house Wi-Fi SON and would work with any 3rd party SON solutions for cellular (they already partner with Airhop). This can directly manage devices or sit on top of existing device management systems and co-ordinate between them. It provides a unified system for management, SON, analytics and optimisation.
As LTE-U becomes deployed, a system that has visibility of both Wi-Fi and LTE should allow best use of the resources and minimise LTE-U stomping on other legitimate users of that spectrum.
Hardwired vs Cloud based
As with many network operation control points, it would be common to co-locate a single small cell management system at the main NOC (Network Operations Centre) with a second fallback system elsewhere in case of disaster. This needs to scale up to the level of the largest deployment expected.
Arguably, availability isn't quite as critical as for other network elements – calls and data sessions aren't disrupted during outages of management systems. However, prolonged outages would prevent any network changes, small cell (re)activations and SON optimisations.
Somewhat unusually, Xcellair have designed their solution from the outset to be entirely cloud based, bringing benefits of scalability and resilience. It remains to be seen if network operators are happy to adopt that approach.
Operators need to have a clear vision for holistic network management and end-user experience. Separate siloed systems for 3G, 4G and Wi-Fi won't achieve that on their own. The larger volumes of network nodes, both small cells and Wi-Fi, require appropriate procedures and tools to handle the scale and achieve their full business potential.
The use of unlicenced spectrum, whether via traditional Wi-Fi or LAA, needs to be handled as another useful resource to meet demand. This isn't just about configuration during installation and commissioning, but becomes more real-time - constantly monitored and optimised.
Most operators already have a clear roadmap for cellular SON. They'll need to ensure it also fits within a wider, holistic view that encompasses small cells, Carrier Wi-Fi and LAA and can handle the full scalability that these bring.