Yaacov Cohen, Director of Product Management, Cellwize

Yaacov Cohen, Director of Product Management, Cellwize

This post is by Yaacov Cohen, Director of Product Management, Cellwize

Closed-loop SON is an attribute that the majority of mobile operators desire from a SON solution today. But is their expectation of closed-loop SON the same as what vendors truly offer, or is it missing a critical aspect?

The Mirage

A Closed-loop SON system would have the ability to automatically receive parameter network sets, run optimisations and 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 truly define what Closed-loop SON is?

In Reality

The true meaning of closed-loop SON is actually 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 for anomalies in network performance. Closed-loop SON can only be completed when realising corrective C-SON techniques, which consider the current level of network performance degradation, while comparing normal traffic pattern behaviors.

Parameter changes will have a direct impact on network performance. With that said, any C-SON parameter adjustment applied on the network will affect the network performance for the sector and its surroundings, in some way, positively or in some cases negatively. In order to carry out the next phase of successful optimisation, and avoid negative impact to the network, C-SON is first requested to verify the positive effects of the latest parameter changes by analysing the network health, usually through network KPIs.

A C-SON solution has to 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 are indicating a deterioration of network coverage, then C-SON would search for a counter-corrective activity. This is possible since the C-SON system, by default, knows how to map certain KPIs to optimisation techniques and can therefore trigger the most relevant and applicable C-SON optimisation module with the appropriate policy.

The Intelligent Feedback Loop

In order for C-SON to be able to recover from a degraded network performance, it needs to have the following capabilities:

  • Identify network degradation
  • Combine several KPI values into complex conditional anomalies
  • Map of multiple KPIs to their correlative SON corrective techniques
  • Determine which set of parameters together with which SON module would be best efficiently applied

For SON to be truly beneficial the KPI layer needs to 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 is suffering from poor network performance. Following the discovery, the list is then 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.

The entire process, intelligent feedback loop, is continuous and on-going. 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 min) of automatic parameter adjustments to verify that the current network is healthy and is performing as expected.

Lifting the Veil of Closed-loop SON

Next time a mobile operator asks about Closed-Loop SON – vendors need to present the 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.

Visit us at POD 12 at LTE Asia!

You can also hear Cellwize discuss the role and opportunities of SON in small cell networks on Sept 26th (HetNet Track) at 15:10.

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