If operators are really serious about HetNets, then network operations cannot remain as usual. Deploying hundreds if not thousands of small cells is an operational nightmare that cannot be left to manual processes which is what operators do today. Automation becomes critical – and it has a name in wireless network: self-organizing networks (SON). So let’s take a quick tour of SON.
Genesis of SON
The NGMN (Next Generation Mobile Networks Association) first published its SON requirements in 2008 which was quickly picked up by 3GPP and rolled into the LTE standardization activities. Starting with Release 8, 3GPP defines interfaces for SON built upon existing management architecture. Successive 3GPP releases incorporates additional SON features tracking the expected network evolution stages in time.
The three main functions of SON are:
- Plug & Play: IP address allocation, authentication, software & configuration data download from OAM, establish connectivity
- Planning radio parameters of a new eNB: Physical Cell ID (CID) automatic configuration, handover & cell selection thresholds, power settings, etc.
- Planning transport parameters of a new eNB
- Planning data alignment for all neighbor nodes: Automatic Neighbor Relation (ANR)
- Self test
- Neighbor cell list optimization (evaluation/addition/deletion of existing neighbor cells & intra/inter frequency and inter system neighbor cell list optimization)
- Interference control
- Handover parameter optimization
- QoS related parameter optimization
- Load balancing
- RACH load optimization
- Energy savings
- Cell /service outage detection & compensation
Three architectures are defined:
- Centralized: SON algorithms are executed in the OAM system or separate SON server. In such solutions SON functionality resides in a small number of locations, at a high level in the network architecture
- Distributed: SON algorithms are executed at the network element level. In such solutions SON functionality resides in many locations at a relatively low level in the network architecture
- Hybrid: part of the SON algorithms are executed in the OAM system, while others are executed at the network element level
There are two modes to SON algorithms:
- Open-loop: SON algorithms made identify the required changes and provide new settings for the operator to review. The recommendations of the SON algorithms are only enacted after the operator approves the proposed changes.
- Closed-loop: The results of the SON algorithms enact the proposed changes dynamically without waiting for operator approvals.
HetNets lay many of operator processes to acquire, install, and operate cell sites bare open to the scalability challenges . SON will be necessary to automate many of these processes which otherwise cannot scale to allow for cost effective network operation. This is ironic because although one of the fundamental objectives of SON is opex reduction, I wonder if the sheer scale of HetNets will eat up much if not all of these savings. In other words, SON is here to stay because it’s an indispensable necessity.