Benefits of Self Optimizing Networks in LTE

Self Optimizing Networks : Benefits of SON in LTE - July 2011

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Mobility Robustness Optimization to avoid Handover failures

The following is from 4G Americas Whitepaper on SON:

Mobility Robustness Optimization (MRO) encompasses the automated optimization of parameters affecting active mode and idle mode handovers to ensure good end-user quality and performance, while considering possible competing interactions with other SON features such as, automatic neighbor relation and load balancing.

There is also some potential for interaction with Cell Outage Compensation and Energy Savings as these could also potentially adjust the handover boundaries in a way that conflicts with MRO. While the goal of MRO is the same regardless of radio technology namely, the optimization of end-user performance and system capacity, the specific algorithms and parameters vary with technology.

The objective of MRO is to dynamically improve the network performance of HO (Handovers) in order to provide improved end-user experience as well as increased network capacity. This is done by automatically adapting cell parameters to adjust handover boundaries based on feedback of performance indicators. Typically, the objective is to eliminate Radio Link Failures and reduce unnecessary handovers. Automation of MRO minimizes human intervention in the network management and optimization tasks.

The scope of mobility robustness optimization as described here assumes a well-designed network with overlapping RF coverage of neighboring sites. The optimization of handover parameters by system operators typically involves either focused drive-testing, detailed system log collection and postprocessing, or a combination of these manual and intensive tasks. Incorrect HO parameter settings can negatively affect user experience and waste network resources by causing HO ping-pongs, HO failures and Radio Link Failures (RLF). While HO failures that do not lead to RLFs are often recoverable and invisible to the user, RLFs caused by incorrect HO parameter settings have a combined impact on user experience and network resources. Therefore, the main objective of mobility robustness optimization should be the reduction of the number of HO-related radio link failures. Additionally, sub-optimal configuration of HO parameters may lead to degradation of service performance, even if it does not result in RLFs. One example is the incorrect setting of HO hysteresis, which may results in ping-pongs or excessively delayed handovers to a target cell. Therefore, the secondary objective of MRO is the reduction of the inefficient use of network resources due to unnecessary or missed handovers.

Most problems associated with HO failures or sub-optimal system performance can ultimately be categorized, as either too-early or too-late triggering of the handover, provided that the required fundamental network RF coverage exists. Thus, poor HO-related performance can generally be categorized by the following events:

* Intra-RAT late HO triggering

* Intra-RAT early HO triggering

* Intra-RAT HO to an incorrect cell

* Inter-RAT too late HO

* Inter RAT unnecessary HO

Up to Release 9, a UE is required to send RLF report only in case of successful RRC re-establishment after a connection failure. Release 10 allows support for RLF reports to be sent even when the RRC reestablishment does not succeed. The UE is required to report additional information to assist the eNB in determining if the problem is coverage related (no strong neighbors) or handover problems (too early, too late or wrong cell). Furthermore, Release 10 allows for precise detection of too early / wrong cell HO.

Smart Deployment with Smart Antennas and ORI

This is from a presentation by Dr. Peter Meissner, Operating Officer, NGMN Alliance.

Its very interesting the way the Antennas are evolving.

If you are interested in reading more about ORI, see the earlier post here.

NSN Celebrating 20 years of GSM

Its been 20 years since the first GSM call was made and GSM is still as relevant today as it was 10 years back.My earlier post today was about the technology deployment and adoption trends and my guess is that GSM/GPRS will be still relevant for long time to come especially its de-facto fallback for the roaming calls. Some Facts about GSM that would should know:* First network launched in 1991* There are 838 GSM Networks in 234 countries with 4.4 Billion subscribers* In 2010, 1.44 million GSM subscribers were added every day* 545 EDGE networks in 198 countries with 1.5 Billion subscribers* By 2015, 1.5billion GSM M2M subscribers will be present

Here is a presentation from NSN about 20 years of GSM and since they had the privilege of launching the first commercial network I am sure they have a good reason to celebrate.

20 Years of GSM: Past, Present & Future

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A new section on 3G4G website on GSM has been added here.

Technology Deployment and Adoption Trends

This informative slide shows the number of years it takes after the technology is launched to reach the peak volumes. Though we know this to be true for the 1G and 2G systems, I find it difficult to believe the same would be true for 3G and 4G systems.

If the LTE deployments are going to happen as per the plans then we may see the peak volumes for 3G/HSPA+ around 2016. It would be difficult to predict the same for '4G' systems as we do not know as of know what all would be part of 4G. As you would recall that LTE was supposed to be 3.9G but was too confusing so everyone adopted it as 4G. LTE-A, the real 4G, I guess would still be part of 4G. What else would end up as 4G is hard to predict so we will have to go with the prediction for the time being.

Dual-Mode and Multi-Mode Femtocells

Came across this slide in one of the presentations from MWC.

The Dual-Mode and maybe Multi-Mode solution (in future) may be very useful, not only from the point of view that it can serve LTE as well as 3G mobile devices but in case of a LTE mobile where for voice calls the UE may have to fall back on 3G network, if there is no 3G coverage then there would be no voice communication possible.

One of the ways to do have a voice communication in the initial phases of LTE is CS Fallback (CSFB). CSFB is possible by the UE establishing the call on UMTS or GSM network. If for some reason the coverage on those networks is non-existent then having a dual-mode femtocell can be really helpful as it would seamlessly transfer the voice call on the 3G.

Hopefully in the future when VoLTE is here these problems would be solved automatically.

The main problem that I can see with this Dual-mode or Multi-mode solution is that the operator would have to be supporting both Small Cells solution across both the networks and I guess they would be slightly expensive.

Infographic on 'The Internet of Things'

Very interesting Infographic from Cisco on the 'Internet of Things' that we have discussed before.

Since its not possible for me to put the whole Infographic here, you can check it out on Cisco blogs.

A Survey on 3GPP Hetrogeneous Networks

A Survey on 3GPP Hetrogeneous Networks

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Available for limited time to download free from here.

Network Mode of Operation (NMO)

Picture Source: Tektronix

The Network Mode of Operation (NMO) is also sometimes referred to as Network Operation Mode (NOM). The Network Modes have different values and interpretation in UTRAN and GERAN

In both the cases the Operation modes is decided based on the Gs interface between the CS CN (core network) a.k.a. MSC and the PS CN a.k.a. SGSN

In UTRAN:

Network Operation Mode I (NMO-I) is used when the Gs interface is present. In this case during the registration a Combined Attach (includes GPRS Attach & IMSI Attach procedures) procedure can be performed. A GMM Attach Request message with the attach type set to Combined Attach is used. Upon completion of this procedure, MM Status is IMSI Attached and GMM State is Attached.

In Network Operation Mode II (NMO-II) the GS Interface is not present. So the GMM attach procedure and the IMSI Attach (via Location Update) has to be performed seperately. This causes additional signalling.

Basic air interface signalling in case of NMO2 is shown here.

In GERAN:

Network operation mode 1. A network which has the Gs interface implemented is referred to as being in network operation mode 1. CS and PS paging is coordinated in this mode of operation on either the GPRS or the GSM paging channel. If the mobile device has been assigned a data traffic channel then CS paging will take place over this data channel rather than the paging channel (CS or PS).

Network operation mode 2. The Gs interface is not present and there is no GPRS paging channel present. In this case, paging for CS and PS devices will be transferred over the standard GSM common control channel (CCCH) paging channel. Even if the mobile device has been assigned a packet data channel, CS paging will continue to take place over the CCCH paging channel and thus monitoring of this channel is still required.

Network operation mode 3. The Gs interface is not present. CS paging will be transferred over the CCCH paging channel. PS paging will be transferred over the packet CCCH (PCCCH) paging channel, if it exists in the cell. In this case the mobile device needs to monitor both the paging channels.

The GERAN part above is extract from the book Convergence Technologies for 3G Networks.

From Martin Sauter's Blog:

The Gs interface, has a number of subtle but important advantages:

During an ongoing GPRS / EDGE data transfer (TBF established), mobiles can't detect incoming voice calls and SMS messages as they are focused on receiving packets and thus can not observe the paging channel. In NMO-1, the circuit switched part of the network forwards the paging message to the packet switched side of the network which then forwards the paging message between the user data blocks while a data transfer is ongoing. Mobiles can thus receive the paging message despite the ongoing data transfer, interrupt the session and accept the voice call or SMS.

Location/Routing area updates when moving to a cell in a different location/routing area are performed much faster as the mobile only communicates with the packet switched part of the network. The packet switched network (the SGSN) then forwards the location update to the circuit switched part of the network (to the MSC) which spares the mobile from doing it itself. This is especially important for ongoing data transfers as these are interrupted for a shorter period of time.

Cell reselections from UMTS to GPRS can be executed much faster due to the same effect as described in the previous bullet. Whithout NOM-1 an Inter RAT (Radio Access Technology) cell reselection with Location and Routing Area update requires around 10 to 12 seconds. With NOM-1 the time is reduced to around 5 to 6 seconds. An important difference as this reduces the chance to miss an incoming call during the change of the radio network. Also, ongoing data transfers are interrupted for a shorter time,an additional benefit that should not be underestimated.

HSPA evolution – beyond 3GPP Release 10

HSPA evolution – beyond 3GPP Release 10, Ericsson, Jul. 2011

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This and other HSPA/HSPA+ presentations are available to download here.