A self-organizing Network (SON) is an automation technology designed to make the planning, configuration, management, optimization and healing of mobile radio access networks simpler and faster. SON functionality and behavior has been defined and specified in generally accepted mobile industry recommendations produced by organizations such as 3GPP (3rd Generation Partnership Project) and the NGMN (Next Generation Mobile Networks).
SON has been codified within 3GPP Release 8 and subsequent specifications in a series of standards including 36.902, as well as public white papers outlining use cases from the NGMN. The first technology making use of SON features will be Long Term Evolution (LTE), but the technology has also been retro-fitted to older radio access technologies such as Universal Mobile Telecommunications System (UMTS). The LTE specification inherently supports SON features like Automatic Neighbor Relation (ANR) detection, which is the 3GPP LTE Rel. 8 flagship feature.
Newly added base stations should be self-configured in line with a "plug-and-play" paradigm, while all operational base stations will regularly self-optimize parameters and algorithmic behavior in response to observed network performance and radio conditions. Furthermore, self-healing mechanisms can be triggered to temporarily compensate for a detected equipment outage, while awaiting a more permanent solution.
SON architectural types
Self-organizing networks are commonly divided into three major architectural types.
In this type of SON (D-SON), functions are distributed among the network elements at the edge of the network, typically the ENodeB elements. This implies a certain degree of localization of functionality, and is normally supplied by the network equipment vendor manufacturing the radio cell.
In centralized SON (C-SON), function are more typically concentrated closer to higher-order network nodes or the network OSS, to allow a broader overview of more edge elements and coordination of e.g. load across a wide geographic area. Due to the need to inter-work with cells supplied by different equipment vendors, C-SON systems are more typically supplied by 3rd parties like Celcite, Gladiator-Innovations or Cisco.
Hybrid SON is a mix of centralized and distributed SON, combining elements of each in a hybrid solution.
Self-organizing network functionalities are commonly divided into three major sub-functional groups, each containing a wide range of decomposed use cases.
Self-configuration strives towards the "plug-and-play" paradigm in the way that new base stations shall automatically be configured and integrated into the network. This means both connectivity establishment, and download of configuration parameters are software. Self-configuration is typically supplied as part of the software delivery with each radio cell by equipment vendors. When a new base station is introduced into the network and powered on, it gets immediately recognized and registered by the network. The neighboring base stations then automatically adjust their technical parameters (such as emission power, antenna tilt, etc.) in order to provide the required coverage and capacity, and, in the same time, avoid the interference.
Every base station contains hundreds of configuration parameters that control various aspects of the cell site. Each of these can be altered to change network behavior, based on observations of both the base station itself, and measurements at the mobile station or handset. One of the first SON features establishes neighbor relations automatically (ANR), while others optimize random access parameters or mobility robustness in terms of handover oscillations. A very illustrative use case is the automatic switch-off of a percent of base stations during the night hours. The neighboring base station would then re-configure their parameters in order to keep the entire area covered by signal. In case of a sudden growth in connectivity demand for any reason, the "sleeping" base stations "wake up" almost instantaneously. This mechanism leads to significant energy savings for operators.
When some nodes in the network become inoperative, self-healing mechanisms aim at reducing the impacts from the failure, for example by adjusting parameters and algorithms in adjacent cells so that other nodes can support the users that were supported by the failing node. In legacy networks, the failing base stations are at times hard to identify and a significant amount of time and resources is required to fix it. This function of SON permits to spot such a failing base stations immediately in order to take further measures, and ensure no or insignificant degradation of service for the users.
Introduction of SON
Self-organizing Networks features are being introduced gradually with the arrival of new 4G systems in radio access networks, allowing for the impact of potential ‘teething troubles’ to be limited and gradually increasing confidence. Self-optimization mechanisms in mobile radio access networks can be seen to have some similarities to automated trading algorithms in financial markets. SON has also been retrofitted to existing 3G networks to help reduce cost and improve service reliability.
The Mobile World Congress trade conference in 2009 saw the first major announcements of SON functionality for LTE mobile networks, with Alcatel-Lucent and Nortel making announcements and demonstrations of early stage products. First deployments occurred in Japan and USA during 2009/10. In 2010 Actix announced a contract  to supply centralized SON for LTE networks to NEC Corporation of Japan.
The first commercial live test of one of the official 3GPP SON functions was held 12 November by TeliaSonera and Ericsson. It verified the Automatic Neighbor Relations (ANR) feature in parts of a commercially deployed network in Sweden, using a mobile for a commercial chipset vendor. ANR automatically sets up neighbor relations based on actual radio conditions.
Subsequent announcements in 2011, 2012, 2013 and 2014 by self-organizing network suppliers such as Amdocs, Cellwize, Cisco, Eden Rock, and Reverb Networks, who have deployed centralized SON (C-SON) solutions on multi-vendor cross-technology 4G LTE, 3G UMTS and 2G GSM mobile operator networks, demonstrates the continuing deployment of centralized SON solutions in both 4G LTE and 3G UMTS domains by some of the largest mobile network operators globally.
Public announcements about live deployments have been made by several vendors, including Celcite (now part of Amdocs), Cisco (formerly Intucell, see below), Cellwize, Eden Rock, and Reverb Networks.
Although introduced as a 4G/LTE technology, several companies have announced or installed SON systems that also control a 2G/3G&4G networks, such as Cellwize and 3G/UMTS networks.
Early adopters of SON technology who have made public announcements include AT&T (USA), KDDI (Japan), Beeline (Kazakhstan) & Pelephone and Cellcom (Israel).
With the evolution of RAN to the cloud, some SON vendors are virtualizing their SON offering, such as Cellwize joins Alcatel Lucent Cloudband Ecosystem Program.
C. Brunner, D. Flore: Generation of Pathloss and Interference Maps as SON Enabler in Deployed UMTS Networks. In: Proceedings of IEEE Vehicular Technology Conf. (VTC Spring '09). Barcelona, Spain, April 2009
- Nomor Research: White Paper "Self-Organizing Networks (SON) in 3GPP Long Term Evolution"
- Self-Organizing Networks, SON, tutorial covering self configuration, optimisation and healing
- C-SON White Papers covering requirements of re-farmed networks, M2M & IoT, Network Modernization, etc