Showing posts with label SON. Show all posts
Showing posts with label SON. Show all posts

Tuesday, 27 March 2012

Tuesday, 1 November 2011

RRC Signalling in Rel-10 for MDT

Last year I wrote about Minimization of Drive Testing (MDT) and mentioned about the possibility of enhancements. Now looking at the new RRC specs I can see a new message LoggedMeasurementsConfiguration has been added,
When the UE is in RRC_CONNECTED mode, this message can be sent and the UE be informed about the measurements to be performed. The message contents are as follows:

LoggedMeasurementConfiguration-r10 ::= SEQUENCE {
criticalExtensions CHOICE {
c1 CHOICE {
loggedMeasurementConfiguration-r10 LoggedMeasurementConfiguration-r10-IEs,
spare3 NULL, spare2 NULL, spare1 NULL
},
criticalExtensionsFuture SEQUENCE {}
}
}


LoggedMeasurementConfiguration-r10-IEs ::= SEQUENCE {
traceReference-r10 TraceReference-r10,
traceRecordingSessionRef-r10 OCTET STRING (SIZE (2)),
tce-Id-r10 OCTET STRING (SIZE (1)),
absoluteTimeInfo-r10 AbsoluteTimeInfo-r10,
areaConfiguration-r10 AreaConfiguration-r10 OPTIONAL, -- Need OR
loggingDuration-r10 LoggingDuration-r10,
loggingInterval-r10 LoggingInterval-r10,
nonCriticalExtension SEQUENCE {} OPTIONAL -- Need OP
}


Once the UE has done the measurements, it can inform the network in one of the following messages, RRCConnectionSetupComplete, RRCConnectionReestablishmentComplete, RRCConnectionReconfigurationComplete and UEInformationResponse that it has the required information available. This is done by including the following new Enum:

logMeasAvailable-r10 ENUMERATED {true} OPTIONAL,

Finally, the network can request the logged Measurements information in the UE Information Request Message. The new fields for that are:


UEInformationRequest-v1020-IEs ::= SEQUENCE {
logMeasReportReq-r10 ENUMERATED {true} OPTIONAL,
nonCriticalExtension SEQUENCE {} OPTIONAL
}

The UE would send the following information in the response message:


LogMeasInfo-r10 ::= SEQUENCE {
locationInfo-r10 LocationInfo-r10 OPTIONAL,
relativeTimeStamp-r10 INTEGER (0..7200),
servCellIdentity-r10 CellGlobalIdEUTRA,
measResultServCell-r10 SEQUENCE {
rsrpResult-r10 RSRP-Range,
rsrqResult-r10 RSRQ-Range
},
measResultNeighCells-r10 SEQUENCE {
measResultListEUTRA-r10 MeasResultList2EUTRA-r9 OPTIONAL,
measResultListUTRA-r10 MeasResultList2UTRA-r9 OPTIONAL,
measResultListGERAN-r10 MeasResultList2GERAN-r10 OPTIONAL,
measResultListCDMA2000-r10 MeasResultList2CDMA2000-r9 OPTIONAL
} OPTIONAL,
...
}


MeasResultList2GERAN-r10 ::= SEQUENCE (SIZE (1..maxCellListGERAN)) OF MeasResultListGERAN


LocationInfo-r10 ::= SEQUENCE {
locationCoordinates-r10 CHOICE {
ellipsoid-Point-r10 OCTET STRING,
ellipsoidPointWithAltitude-r10 OCTET STRING,
...
},
horizontalVelocity-r10 OCTET STRING OPTIONAL,
gnss-TOD-msec-r10 OCTET STRING OPTIONAL,
...
}

Wednesday, 31 August 2011

Ultra Self Organising Networks (UltraSON)

While watching the Femtocell Video, I was a bit curious on what exactly UltraSON does, so I decided trying to find more info. Surprisingly the information was hard to come by. I finally managed to find the Qualcomm site that has more details but surprisingly it wasnt east to find. From the website (link at bottom):

Qualcomm femtocell R&D program is focused on developing self organizing network features to address interference and mobility management for femtocell deployment in residential and enterprise environments. Interference and mobility management is a chief concern especially when operators are planning for high levels of perfromace from dense and an unplanned femtocell deployments. Qualcomm has developed UltraSON™, a comprehensive suite of interference and mobility management techniques for femtocell deployments in residential and enterprises.

The techniques that make UltraSON:


More details on UltraSON at : http://www.qualcomm.com/research/femtocells

Wednesday, 10 August 2011

Self-Evolving Networks (SEN): Next step of SON

In a post last year, I listed the 3GPP features planned for the Self-Organising networks. Self-optimisation has been a part of the SON. It is becoming more of a common practice to refer to SON as Self-Optimising networks. A recent 4G Americas whitepaper was titled "Benefits of self-optimizing networks in LTE".

The next phase in the evolution of the Self-Configuring, Self-organizing and Self-optimizing network are the Self-Evolving Networks (aka. SEN) that will combine the Organizing and Optimizing features with the Self-testing and Self-Healing features. Self-testing and Self-healing have been recommended as subtasks of SON in the NGMN white paper. Self-testing and self-healing means that a system detects itself problems and mitigates or solves them avoiding user impact and significantly reducing maintenance costs.

We may still be a long way away from achieving this SEN as there are quite a few items being still standardised in 3GPP. Some of the standardised items have not yet been fully implemented and tested as well. Some of this new features that will help are listed as follows:

Automatic Radio Network Configuration Data Preparation (Rel-9)

When radio Network Elements (e.g. cells and/or eNBs) are inserted into an operational radio network, some network configuration parameters cannot be set before-hand because they have interdependencies with the configuration of operational NEs. "Dynamic Radio Network Configuration Data Preparation" comprises the generation and distribution of such interdependent parameters to the newly inserted network element and optionally already operational NEs.

This functionality allows fully automatic establishment of an eNB into a network. Otherwise an operator needs to set these configurations manually. Without this functionality self-configuration cannot be considered not fully as "self".


SON Self-healing management (Rel-10)

The target of Self-Healing (SH) is to recover from or mitigate errors in the network with a minimum of manual intervention from the operator.

Self-healing functionality will monitor and analyse relevant data like fault management data, alarms, notifications, and self-test results etc. and will automatically trigger or perform corrective actions on the affected network element(s) when necessary. This will significantly reduce manual interventions and replace them with automatically triggered re-s, re-configurations, or software reloads/upgrades thereby helping to reduce operating expense.


LTE Self Optimizing Networks (SON) enhancements (Rel-10)

This WI continues work started in Rel-9. Some cases that were considered in the initial phases of SON development are listed in the TR 36.902. From this list, almost all use cases are already specified. Capacity and Coverage Optimization (CCO) was already nominally part of the Rel-9 WI, but could not be completed due to amount of work related to other use cases. Energy Savings are a very important topic, especially for operators, as solutions derived for this use case can significantly limit their expenses. According to TR 36.902 this solution should concern switching off cells or whole base stations. This may require additional standardised methods, once there is need identified for.

Basic functionality of Mobility Load Balancing (MLB) and Mobility Robustness Optimization (MRO), also listed in TR 36.902, were defined in Rel-9. However, successful roll-out of the LTE network requires analysing possible enhancements to the Rel-9 solutions for MLB and MRO. In particular, enhancements that address inter-RAT scenarios and inter-RAT information exchange must be considered. These enhancements should be addressed in Rel-10. There may also be other use cases for LTE for which SON functionality would bring optimizations. The upcoming LTE-A brings about also new challenges that can be addressed by SON. However, since not all features are clearly defined yet, it is difficult to work on SON algorithms for them. It is therefore proposed to assign lower priority to the features specific for LTE-A.


UTRAN Self-Organizing Networks (SON) management (Rel-11)

For LTE, SON (Self-Organizing Networks) concept and many features have been discussed and standardised.

The SON target is to maintain network quality and performance with minimum manual intervention from the operator. Introducing SON functions into the UTRAN legacy is also very important for operators to minimize OPEX.

Automatic Neighbour Relation (ANR) function, specified in the LTE context, automates the discovery of neighbour relations. ANR can help the operators to avoid the burden of manual neighbour cell relations management.

Self-optimization functionalities will monitor and analyze performance measurements, notifications, and self-test results and will automatically trigger re-configuration actions on the affected network node(s) when necessary.

This will significantly reduce manual interventions and replace them with automatically triggered re-optimizations or re-configurations thereby helping to reduce operating expenses.

Minimization of Drive Tests (MDT) for E-UTRAN and UTRAN is an important topic in 3GPP Rel-10.

With the help of standardized UTRAN MDT solutions, Capacity and Coverage Optimization (CCO) for UTRAN should also be considered in UTRAN SON activities.


Study on IMS Evolution (Rel-11)

IMS network service availability largely relies on the reliability of network entity. If some critical network elements (e.g. S-CSCF, HSS) go out of service, service availability will be severely impacted. Moreover network elements are not fully utilized because network load is not usually well distributed, e.g. some nodes are often overloaded due to sudden traffic explosion, while others are under loaded to some extent. Though there’re some element level approaches to solve these problems, such as the ongoing work in CT4, the system level solution should be studied, for example, the method to distribute load between network elements in different regions especially when some disaster happens, such as earthquake.

The network expansion requires a great deal of manual configurations, and the network maintenance and upgrade are usually time-consuming and also costly for operators. Introducing self-organization features will improve the network intelligence and reduce the efforts of manual configuration. For example, upon discovering the entry point of the network, new nodes can join the network and auto-configure themselves without manual intervention. And if any node fails, other nodes will take over the traffic through the failed node timely and automatically.


The above mentioned features are just few ways in which we will achieve a truly zero-operational 4G network.

Wednesday, 27 July 2011

MRO: Handover failures signalling

Continuing on the Self-organising Network (SON) feature of Mobility Robust Optimisation, Handover failures.


Click on image to enlarge

One of the discussions I had with a colleague is how would the signalling happen in case of Handover failures I mentioned earlier.

After the handover failure, when the connection is successfully established again either as a normal Setup or Re-Establishment or RRC Reconfiguration then a new optional field is available:

rlf-InfoAvailable-r10 ENUMERATED {true} OPTIONAL,

This is used to indicate to the network that the UE has some information relating to the RL Failure that occurred.

The network will then use the UE Information Request I blogged about earlier to ask for this information. The UE will send the information back in the response.

It should be noted that this UEInformationRequest and Response messages were introduced part of Release-9 but there has been since some updates in Release-10. The Response message now looks as follows:

RLF-Report-r9 ::= SEQUENCE {
measResultLastServCell-r9 SEQUENCE {
rsrpResult-r9 RSRP-Range,
rsrqResult-r9 RSRQ-Range OPTIONAL
},
measResultNeighCells-r9 SEQUENCE {
measResultListEUTRA-r9 MeasResultList2EUTRA-r9 OPTIONAL,
measResultListUTRA-r9 MeasResultList2UTRA-r9 OPTIONAL,
measResultListGERAN-r9 MeasResultListGERAN OPTIONAL,
measResultsCDMA2000-r9 MeasResultList2CDMA2000-r9 OPTIONAL
} OPTIONAL,
...,
[[ locationInfo-r10 LocationInfo-r10 OPTIONAL,
failedPCellId-r10 CHOICE {
cellGlobalId-r10 CellGlobalIdEUTRA,
pci-arfcn-r10 SEQUENCE {
physCellId-r10 PhysCellId,
carrierFreq-r10 ARFCN-ValueEUTRA
}
} OPTIONAL,
reestablishmentCellId-r10 CellGlobalIdEUTRA OPTIONAL,
timeConnFailure-r10 INTEGER (0..1023) OPTIONAL,
connectionFailureType-r10 ENUMERATED {rlf, hof} OPTIONAL,
previousPCellId-r10 CellGlobalIdEUTRA OPTIONAL
]]
}

Everything after the extension marker ellipses (...) is added in release 10. More information in Release-10 RRC specs (36.331)

Friday, 22 July 2011

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.

Friday, 18 March 2011

Roadmap to Operational Excellence for Next Generation Mobile Networks


This presentation is from:

FP7 SOCRATES Final Workshop on Self-Organisation in Mobile Networks February 22, 2011 - Karlsruhe, Germany

This and all other presentations from this workshop are available to download from here.

Wednesday, 5 January 2011

eICIC: Enhanced inter-cell interference coordination in 3GPP Release-10

Inter-cell interference coordination (ICIC) was introduced in Release-8/9 of the 3GPP LTE standards. The basic idea of ICIC is keeping the inter-cell interferences under control by radio resource management (RRM) methods. ICIC is inherently a multi-cell RRM function that needs to take into account information (e.g. the resource usage status and traffic load situation) from multiple cells.

Broadly speaking, the main target of any ICIC strategy is to determine the resources (bandwidth and power) available at each cell at any time. Then (and typically), an autonomous scheduler assigns those resources to users. Thus, from the Radio Resource Control perspective, there are two kind of decisions: (a) which resources will be allocated to each cell? and, (b) which resources will be allocated to each user?. Clearly, the temporality of such decisions is quite different. Whereas resources to users allocation is in the order of milliseconds, the allocation of resources to cells take much longer periods of time or can be fixed.

Static ICIC schemes are attractive for operators since the complexity of their deployment is very low and there is not need for new extra signaling out of the standard. Static ICIC mostly relies on the fractional reuse concept. This means that users are categorized according to their Signal-to-Noise-plus-Interference Ratio (SINR), that means basically according to their inter-cell interference, and different reuse factors are applied to them, being higher at regions with more interference, mostly outer regions of the cells. The total system bandwidth is divided into sub-bands which are used by the scheduler accordingly.

A simple way to explain ICIC is based on picture above. The users are divided into two categories, one is Cell Center User (CCU), and the other one is Cell Edge User (CEU). CCUs are the users distributed in the gray region of above figure, and CEUs are the users distributed in the above red, green and blue areas. CCU can use all the frequencypoints to communicate with the base station, while CEU must use corresponding specified frequency points to ensure orthogonality between different cells.
CEUs can be assigned a higher transmissionpower for the frequency reuse factor is greater than 1. The frequency points are not overlapped at the edges so the adjacent cell interference is small. CCU’s frequency reuse factor is 1; for the path loss is small and transmission power is low. Therefore the interference to the adjacent cells is not high either.

Dominant interference condition has been shown when Non-CSG/CSG users are in close proximity of Femto, in this case, Rel8/9 ICIC techniques are not fully effective in mitigating control channel interference, and hence, Enhanced interference management is needed At least the following issues should be addressed by any proposed solutions:
o Radio link monitoring (RLM)
o Radio Resource Management (including detection of PSS/SSS and PBCH)
o Interference from CRS
oo To PCFICH/PHICH/PDCCH
oo To PDSCH
o CSI measurement
o Interference from PDCCH masked with P-RNTI and SI-RNTI (for SIB-1 only) and associated PCFICH

As a result, from Release-10 onwards eICIC work was started. In Rel-10, two eICIC or Enhanced inter-cell interference coordination (also incorrectly referred to as Enhanced Inter-Cell Interference Cancellation) were being actively discussed. They are Time domain eICIC and autonomous HeNB power setting. More advanced ideas are being thought of beyong Rel-10 including Interference management techniques on carrier resolution ( optimally exploiting available Networks frequency assets (carriers in same or different bands) , combination with Carrier Aggregation; interference management schemes proposed both during LTE-Advanced Study Item phase, and during Rel-10 HetNet eICIC work.

From an earlier presentation in SON Conference:

eICIC:
- Effectively extends ICIC to DL control - time domain
- Requires synchronization at least between macro eNB and low power eNBs in its footprint
- No negative impact on legacy Rel 8 Use

Range Extension(RE)
- Refers to UE ability to connect and stay connected to a cell with low SINR
- Achieved with advanced UE receivers - DL interference cancellation (IC)

RE + eICIC technique:
– Eliminates coverage holes created by closed HeNBs
– Improves load balancing potential for macro network with low power eNBs and leads to significant network throughput increase
–Enables more UEs can be served by low power eNBs, which can lead to substantially higher network throughput

More details on eICIC is available in 3GPP CR's and TR's listed below:
  • R1-105081: Summary of the description of candidate eICIC solutions, 3GPP TSG-WG1 #62, Madrid, Spain, August 23rd – 27th, 2010.
  • R1-104942: Views on eICIC Schemes for Rel-10, 3GPP TSG RAN WG1 Meeting #62, Madrid, Spain, 23-27 August, 2010.
  • R1-104238: eICIC Chairman’s note, 3GPP TSG RAN WG1 Meeting #61bis, Dresden, Germany, 28th June – 2nd July 2010.
  • R1-103822: Enhanced ICIC considerations for HetNet scenarios, 3GPP TSG RAN WG1 #61bis Meeting, Dresden, Germany, June 28 – July 2, 2010.
You can also check out NTT Docomo's presentation on LTE Enhancements and Future Radio Access here.

Wednesday, 15 December 2010

SON in Heterogeneous Networks

Another presentation from the SON 2010 Conference based on yesterdays theme of HetNets.


Presented by Seungpyo Hong of Institute of Network Technology, SK Telecom.

Tuesday, 14 December 2010

What are Heterogeneous Networks (HetNets)?

HetNets are hot. I hear about them in various contexts. Its difficult to find exactly what they are and how they will work though. There is a HetNets special issue in IEEE Communications Magazine coming out next year but that's far away.

I found an interesting summary on HetNets in Motorola Ezine that is reproduced below:


“The bigger the cell site, the less capacity per person you have,” said Peter Jarich, research director with market intelligence firm Current Analysis. “If you shrink coverage to a couple of blocks, you are having that capacity shared with a fewer number of people, resulting in higher capacity and faster data speeds.”

This is a topic the international standards body, the Third Generation Partnership Project (3GPP), has been focusing on to make small cells part of the overall cellular network architecture.

“What we’re seeing is a natural progression of how the industry is going to be addressing some of these capacity concerns,” said Joe Pedziwiatr, network systems architect with Motorola. “There is a need to address the next step of capacity and coverage by introducing and embracing the concepts of small cells and even looking at further advances such as better use of the spectrum itself.”

As such, discussion regarding this small-cell concept has emerged into what is called heterogeneous networks, or Het-Net, for short. The idea is to have a macro wireless network cooperating with intelligent pico cells deployed by operators to work together within the macro network and significantly improve coverage and augment overall network capacity. Small cells can also be leveraged to improve coverage and deliver capacity inside buildings. Indoor coverage has long been the bane of mobile operators. Some mobile operators are already leveraging this concept, augmenting their cellular service offering with WiFi access to their subscriber base in order to address the in-building coverage and capacity challenges facing today’s cellular solutions.

Pedziwiatr said this Het-Net structure goes far beyond what is envisioned for femtocells or standard pico cells for that matter. Introducing a pico cell into the macro network will address but just one aspect of network congestion, namely air interface congestion. The backhaul transport network may become the next bottleneck. Finally, if all this traffic hits the core network, the congestion will just have shifted from the edge to the core.

“This requires a system focus across all aspects of planning and engineering,” Pedziwiatr said. “We’re trying to say it goes beyond that of a femto. If someone shows up at an operator and presents a pico cell, that is just one percent of what would be needed to provide true capacity relief for the macro network.”

Femtocells, otherwise known as miniature take-home base stations, are obtained by end users and plugged into a home or office broadband connection to boost network signals inside buildings. A handful of 3G operators worldwide are selling femtocells as a network coverage play. For the LTE market, the Femtocell Forum is working to convince operators of the value of a femtocell when it comes to better signal penetration inside buildings and delivering high-bandwidth services without loading the mobile network. This is possible, because the backhaul traffic runs over the fixed line connection. However, this femtocell proposition largely relies on end user uptake of them—not necessarily where operators need them, unless they install femtocells themselves or give end users incentives to acquire them.

As with any new concept, there are challenges to overcome before Het-Nets can become reality. Het-Nets must come to market with a total cost of ownership that is competitive for an operator to realize the benefit of providing better capacity, higher data speeds, and most of all, a better end-user experience said Chevli.

“The level of total cost of ownership has to be reduced. That is where the challenge is for vendors to ensure that any new solution revalidates every existing tenet of cellular topology and evolve it to the new paradigm being proposed,” Chevli said. “You can’t increase the number of end nodes by 25X and expect to operate or manage this new network with legacy O&M paradigms and a legacy backhaul approach.”

One of the issues is dealing with interference and Het-Net network traffic policies. “How do you manage all of these small cell networks within the macrocell network?” asked Jarich. “Right now if you have a bunch of femtocells inside a house, there is this concept that the walls stop the macrocell signals from getting in and out. You get a separation between the two. Go outdoors with small cells underlying bigger cells and you get a lot more interference and hand-off issues because devices will switch back and forth based on where the stronger signal is.”

Pedziwiatr said for a Het-Net to work, it would require a change in node management, whereby an operator isn’t burdened with managing big clusters of small cells on an individual basis. “We see elements of SON (self organizing networks), self discovery and auto optimization that will have to be key ingredients in these networks. Otherwise operators can’t manage them and the business case will be a lot less attractive,” he said.

Fortunately, the industry has already been working with and implementing concepts of SON in LTE network solutions. In the femtocell arena also, vendors have been incorporating some elements and concepts of SON so that installing them is a plug-and-play action that automatically configures the device and avoids interference. But even then, Het-Nets will require further SON enhancement to deal with new use cases, such as overlay (macro deployment) to underlay (pico deployments) mobility optimization.

When it comes to LTE, SON features are built into the standard, and are designed to offer the dual benefit of reducing operating costs while optimizing performance. SONs will do this by automating many of the manual processes used when deploying a network to reduce costs and help operators commercialize their new services faster. SON will also automate many routine, repetitive tasks involved in day-to-day network operations and management such as neighbor list discovery and management.

Other key sticking points are deployment and backhaul costs. If operators are to deploy many small cells in a given area, deploying them and backhauling their traffic should not become monumental tasks.

Chevli and Pedziwiatr envision Het-Nets being deployed initially in hot zone areas – where data traffic is the highest – using street-level plug-and-play nodes that can be easily installed by people with little technical know-how.

“Today, macro site selection, engineering, propagation analysis, rollout and optimization are long and expensive processes, which must change so that installers keep inventories of these units in their trucks, making rollout simple installations and power-ups,” said Pedziwiatr. “These will be maintained at a minimum with quick optimization.”

The notion of backhauling traffic coming from a large cluster of Het-Net nodes could also stymie Het-Nets altogether. Chevli said that in order to keep costs down, Het-Net backhaul needs to be a mix of cost-effective wireless or wired backhaul technology to aggregate traffic from what likely will be nodes sitting on lamp posts, walls, in-building and other similar structures. The goal then is to find a backhaul point of presence to aggregate the traffic and then put that traffic on an open transport network in the area.

Backhaul cost reductions may also be a matter of finding ways to reduce the amount of backhaul forwarded to the core network, Pedziwiatr said. These types of solutions are already being developed in the 3G world to cope with the massive data traffic that is beginning to crush networks. For traffic such as Internet traffic, which doesn’t need to travel through an operator’s core network, offloading that traffic as close to the source as possible would further drive down the cost of operation through the reduction of backhaul and capacity needs of the core network.

In the end, with operators incorporating smaller cells as an underlay to their macro network layer rather than relying on data offloading techniques such as femtocells and WiFi that largely depend on the actions of subscribers and impacted by the surrounding cell operating in the same unlicensed frequency, Het-Nets in licensed spectrum will soon become the keystone in attacking the ever-present congestion issue that widely plagues big cities and this is only likely to get worse over time.

Image Source: Dr. Daichi Imamura, Panasonic presentation.

Thursday, 9 December 2010

Minimization of Drive Tests (MDT) in 3GPP Release-10

Another one that came from the SON conference.

At present, the network optimisation after it is operational is generally done by drive testing. In this an equipment (test mobile) that collects measurements and location information collects all the required information while the equipment is being driven in a car on the roads and this information is used offline to analyse the coverage in different locations and based on that the parameters, power, antenna locations, antenna tilts, etc. are optimised. After the changes to any of the optimisation paramaters, drive test has to be undertaken again to make sure that the impact of these changes are positive.

One more thing that has to be taken account of is that the drive tests have to be carried out at di9ffert times to be able to predeict the behaviour at different loads.

Using drive tests for network optimization purposes is costly and causes also additional CO2 emissions, so it is desirable to develop automated solutions, including involving UEs in the field, in 3GPP to reduce the operator costs for network deployment and operation. The studies done as part of the study item phase [1] have shown that it is beneficial to collect UE measurements to enable a more efficient network optimisation and it is feasible to use control plane solutions to acquire the information from devices. This information, together with information available in the radio access network can be used for Coverage Optimization purposes.

It should be remembered that drive tests form a big part of the Network opex and Deutsche Telekom for example expects a 40% cost saving with SON (and MDT is a part of that)

Goal of MDT in 3GPP Rel.10
– Automatic UE measurements collection and data logging used to replace the manual drive testing that the operators have to perform in their networks
– Evaluation of network performance per physical location
– For both HSPA & LTE


There are two different types of MDT:

Immediate MDT: MDT functionality involving measurement performance by UE in CONNECTED state and reporting of the measurements to eNB/RNC available at the time of reporting condition.

Logged MDT: MDT functionality involving measurement performance by UE in IDLE state at points in time when configured conditions are satisfied, its storage in measurement log for reporting to eNB/RNC at a later point in time.

The solutions for MDT shall be able to work independently from SON support in the network. Relation between measurements/solution for MDT and UE side SON functions shall be established in a way that re-use of functions is achieved where possible.

• Use cases
– 3GPP R10: Coverage optimization : Prio1
– For 3GPP > R10 :Capacity optimization, Mobility optimization, Parameterization of common channels, QoS verification, no specific measurements
- In Release-11 MDT Enhancements and evaluation of other MDT use cases, such as ”Parameterization of common control channels” and Positioning enhancements will be explored.

• MDT and SON
– MDT is about UE measurement collection for off-line processing No automatic mechanism is defined MDT
– SON is aiming at instantaneous/automated reaction on short to middle term network issues

It should be noted that MDT is a wide area and some of the boundaries between MDT and SON are a bit fuzzy. One of the other ways for SON is to enable detected cell measurements in the handset. This will give the indication about the cells that are not in the monitored set but the UE is able to see.

The RRC (control plane) measurements for LTE are not advanced enough and there are no measurements for UE position. On the other hand for UMTS/HSPA the UE positioning measurements could be used to report the exact location at the point of measurements. There are some discussions for enhancing the LTE measurements to include the longitude, latitude, altitude, velocity and even direction (too ambitious?).

Finally it should be pointed out that UE based reporting based on the User Plane Measurements (typically done by the operator installing a small application on the handset) can be performed by the operator in case a user is reporting poor coverage or failure in an area. Since these are proprietary applications, the operator can collect variety of information including but not limited to, position information, crrent cell and neighbour cell power levels, etc.

With all the control plane measurements and user plane measurements, the battery life could be severely affected and it has to be made sure that these are done very seldomly or with users permission.

Some of the things mentioned above may not be exactly true and if you know better please feel free to correct me.

[1] 3GPP TR 36.805 - Study on Minimization of drive-tests in Next Generation Networks

[2] 3GPP TS 37.320 - Universal Terrestrial Radio Access (UTRA) and Evolved Universal Terrestrial Radio Access (E-UTRA); Radio measurement collection for Minimization of Drive Tests (MDT); Overall description; Stage 2 (Release 10)

Wednesday, 8 December 2010

SON for reducing Opex in Legacy Networks

Presented by Stéphane Téral, Principal Analyst, Mobile and FMC Infrastructure, Infonetics Research in the 1st Self-Organizing Networks Conference, 30th Nov and 1st Dec. 2010 at the Waldorf Hilton.

Tuesday, 7 December 2010

SON framework in 3GPP

From a Presentation by Cinzia Sartori from Nokia Siemens Networks (NSN) in the Self-Organising Networks Conference in London, Nov. 2010

Release 8 functionality
• Self-configuration procedures

Release 9 enhancements
• Self-optimization procedures
• Energy Saving Intra-RAT

Release 10 objectives
• Extend Self-optimization procedures , including inter-RAT
• Minimization of Drive Test (MDT)
• Energy Saving extension, including Multi-RAT (Study Item)
• 3G-ANR
• SON Conflict Resolution

SON features for R11 (Probably - Under Discussion)
• Minimization of Drive Tests (MDT) enhancements
• Mobility Robustness Optimization for MultiRAT
• SON for LTE-A features defined in Rel.10
•• Hetrogeneous Networks aka. HetNet?
•• SON for Relays
•• SON for Carrier Aggregation

Wednesday, 1 December 2010