| Yaacov Cohen, Director Product Management, September 04, 2014

Wireless operators bring it up in almost all operator-vendor dialogues: “Does your SON work in a closed-loop fashion?”. Closed-loop SON is one of the main promises of automated centralized SON (C-SON) solutions and is sometimes a mandatory requirement from operators, making it essential in any solid SON offering.

In most cases, when the vendor simply answers “of course!”, have they truly understood the full intent of what the operators are asking, or is closed-loop SON missing a critical aspect?

The foundation

A closed-loop SON has the ability to automatically receive parameter network sets, run optimization, then provision parameter set adjustments back onto the network – automatically and faultlessly. This loop part of a C-SON integration with vendor OSS is the basic foundation of any C-SON solution, ensuring the automation of coordinated SON activities. But does this accurately define all aspects of closed-loop SON?

The bigger picture

The true meaning of closed-loop SON is much broader. It isn’t just the configured connections that allow for the closed-loop data transfers, but rather a wider network-centric approach which continuously seeks anomalies in network performance. Closed-loop SON can only be completed by utilizing corrective C-SON techniques, which consider the current level of network performance degradation while comparing it against normal traffic pattern behavior. Parameter changes have a direct impact on network performance. Any C-SON parameter adjustment applied on the network will affect network performance for the sector and its surroundings, eith positively or in some cases negatively. In order to carry out the next phase of successful optimization and avoid negative impact to the network, C-SON is first requested to verify the positive effects of the latest parameter changes by analyzing the network health, usually through network KPIs. A C-SON solution must recover from a degraded network performance situation automatically. It can do this by either reverting back to a healthy network snapshot or applying corrective SON activities.
In the event where the expected results are not met, for example the KPIs indicate deterioration of network coverage, then C-SON searches for a counter-corrective activity. This is possible since the C-SON system knows by default how to map certain KPIs to optimization techniques and can therefore trigger the most relevant and applicable C-SON optimization module with the appropriate policy.

Intelligent feedback loop

In order for C-SON to be able to recover from a degraded network performance, it must be able to:

  • Identify network degradation
  • Combine several KPI values into complex conditional anomalies
  • Map multiple KPIs to their correlative SON corrective techniques
  • Determine which set of parameters is most efficiently applied to which particular SON module

For SON to be beneficial the KPI layer must be incorporated within the platform mediation layer and triggered upon the arrival of new KPI reports. The immediate outcome is the discovery, which is a list of sectors where users or the network suffer from poor network performance. Following the discovery, the list is cross-diagnosed with the latest SON activities along with other non-SON related activities for the specific sector, resulting in multiple alternative correction methods.

The next stage, the active phase, is where the C-SON system self-initiates the most relevant corrective technique for the sector or cluster at hand along with its corresponding parameters. Alternatively the C-SON system simply decides to revert back to a previously stored network configuration record. The rollback action re-iterates all SON adjustments provisioned on a sector until the entire configuration is recovered.

Accurate picture of closed-loop SON

The entire process, which forms an intelligent feedback loop, is continuous and ongoing. With each new set of KPI reports arriving from the network, C-SON evaluates the current KPI set in real-time. It compares the most recent cycle (every 15-60 minutes) of automatic parameter adjustments to verify that the current network is healthy and performing as expected.

The next time a mobile operator asks about closed-loop SON, vendors must present an accurate picture.

Closed-loop SON is much more than just a simple automated network monitoring feature with automated data feeds traveling back and forth. Closed-loop SON conceals the many necessary elements in the monitoring infrastructure layers which continuously guard network performance, striving to continuously pre-empt and recover from degraded situations automatically and in closed-loop.