A Self-configuration Subsystem will be created in OAM to be responsible for the self configuration of eNB. For self-optimisation functions, they can be located in OAM or eNB or both of them. So according to the location of optimisation algorithms, SON can be divided into three classes: Centralised SON, Distributed SON and Hybrid SON.
• Centralized SON
In Centralized SON, optimisation algorithms are executed in the OAM System. In such solutions SON functionality resides in a small number of locations, at a high level in the architecture. Below figure shows an example of Centralized SON.
In Centralized SON, all SON functions are located in OAM systems, so it is easy to deploy them. But since different vendors have their own OAM systems, there is low support for optimization cases among different vendors. And it also does not support those simple and quick optimization cases.
• Distributed SON
In Distributed SON, optimisation algorithms are executed in eNB. In such solutions SON functionality resides in many locations at a relatively low level in the architecture. Below figure shows an example of Distributed SON.
In Distributed SON, all SON functions are located in eNB, so it causes a lot of deployment work. And it is also difficult to support complex optimization schemes, which require the coordination of lots of eNBs. But in Distributed SON it is easy to support those cases, which only concern one or two eNBs and require quick optimization responses. For Distributed SON, X2 interface needs to be extended.
• Hybrid SON
In Hybrid SON, part of the optimisation algorithms are executed in the OAM system, while others are executed in eNB. Below figure shows an example of Hybrid SON.In Hybrid SON, simple and quick optimization schemes are implemented in eNB and complex optimization schemes are implemented in OAM.
So it is very flexible to support different kinds of optimization cases. And it also supports the optimization between different vendors through X2 interface. But on the other hand, it costs lots of deployment effort and interface extension work.
