Self Organizing Networks, SON (Reducing Complexity in LTE Cellular Network)

Author Topic: Self Organizing Networks, SON (Reducing Complexity in LTE Cellular Network)  (Read 810 times)

Offline najnin

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Self Organizing Networks, SON are essential for today's complicated cellular networks to configure, organize, optimize performance, & then provide self healing capabilities when faults occur.

With radio networks like those used for LTE and other cellular technologies becoming more complex, network planning needs to be made easier: planning, configuration, management, optimization and healing all need to be automated to bring improvements.

As a result the concept of self-organizing networks, SON is growing in interest and use. With the networks themselves being able to monitor performance, they can optimize themselves to be able to provide the optimum performance.

By using self-organizing networks, SON technology, networks are able to organize and optimize their performance. Operators can then benefit from significant improvements in terms of both CAPEX, capital expenditure and later OPEX, operational expenditure.

Definition of Self Organizing Networks

Self organizing networks, SON, can be defined as a set of use cases that govern a network including the planning, set up and maintenance activities.

In this way the self-organizing networks enable the network to set itself up and then manage the resources to enable the optimum performance to be achieved at all times.

The main drive in the SON development and standardization up to now comes from 3GPP, primarily for LTE, but also extended towards 2G and 3G networks in later releases. These features are currently not available between 3GPP access technologies and other access technologies like Wi-Fi.

Why SON?

There are three main reasons.

The first is that the number of parameters that must be set in the network elements has increased significantly from each technology generation to the next. UMTS has a significantly higher number of parameters than GSM, and LTE has even more. Hence, it is not practical to set and maintain these manually.

The second reason is that the quick evolution of wireless networks has led to operators having parallel operation of 2G, 3G, and LTE infrastructures, and even also networks using non-3GPP technologies like Wi-Fi. Operators need to coordinate the operations of their network to utilize their network resources as efficiently as possible. This requires inter-RAT (radio access technology) SON functionality.

The third reason is that an increasing part of the traffic will be on small cells such as microcells, picocells, and femtocells.

Self Organizing Networks areas

There are three main areas over which the self-organizing networks operate.

Self configuration:   The aim is for base stations to become essentially "Plug and Play" items. They should need as little manual intervention in the configuration process as possible. This will enable the skill level of installers to be reduced, thereby saving costs while improving the reliability. Accordingly this is a major element within the overall self organizing network, SON software. This is the dynamic plug-and-play configuration of newly deployed eNBs. The eNB will by itself configure the Physical Cell Identity, transmission frequency and power, leading to faster cell planning and rollout. The interfaces S1 and X2 are dynamically configured, as well as the IP address and connection to IP backhaul. To reduce manual work ANR (Automatic neighbor relations) is used. ANR configures the neighboring list in newly deployed eNBs and is optimizing the list configuration during operation.

Fig 1: PCI Reporting

Self optimization:   Once the system has been set up, it will be necessary to optimize the operational characteristics to best meet the needs of the overall network. This is achieved by self-optimization routines within the overall self-organizing network, SON software. Self optimization includes optimization of coverage, capacity, handover and interference.
Mobility load balancing (MLB) is a function where cells suffering congestion can transfer load to other cells, which have spare resources. MLB includes load reporting between eNBs to exchange information about load level and available capacity.
MLB can also be used between different Radio Technologies. In case of inter-RAT the load reporting RAN Information Management (RIM) protocol will be used to transfer the information via the core between the base stations of different radio technologies. A handover due to load balancing is carried out as a regular handover, but it may be necessary to amend parameters so that the User Equipment (UE) does not return to the congested cell.

Fig 2, 3: Handover

Self-healing:   Any system will develop faults from time to time. This can cause major inconvenience to users, however it is often possible for the overall network to change its characteristics to temporarily mask the effects of the fault. Boundaries of adjacent cells can be increased by increasing power levels and changing antenna elevations, etc. This self-healing aspect of SON, self-organizing networks is of great interest. Coverage and Capacity Optimization enables automatic correction of capacity problems depending on slowly changing environment, like seasonal variations.

Benefits of SON:

To be more specific, the main benefits of introducing SON functions in cellular networks are as follows.
(i)   Reduced installation time and costs.
(ii)   Reduced OPEX due to reductions in manual efforts in connection with monitoring, optimizing, diagnosing, and healing of the network.
(iii)   Reduced CAPEX due to more optimized use of network elements and spectrum.
(iv)   Improved user experience.
(v)   Improved network performance.

Terminology:
ANR - Automatic Neighbour Relations, CGID - Cell Global Id, C-RNTI - Cell Radio Network Temporary Identifier, eNB - evolved Node B, MLB - Mobility Load Balancing, MRO - Mobility Robustness Optimization, OAM - Operation, administration and maintenance, PCI - Physical Cell Identity, PCID - Physical cell identities, PRACH - Physical Random Access Channel, PRB - Physical Resource Block, RACH - Random Access Channel, RAN - Radio Access Network, RAT - Radio Access Technology, RIM - RAN Information Management , RLF - Radio Link Failure, RNTI - Radio Network Temporary Identifier, RRC Radio Resource Control

References:

http://www.radio-electronics.com/info/cellulartelecomms/self-organising-networks-son/basics-tutorial.php
http://www.3gpp.org/SON
http://www.hindawi.com/journals/jcnc/2012/862527/