SON in LTE - additional materials

LTE SON as a concept for NW automation

LTE SON podejściem do automatyzacji działania sieci

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LTE SON Outline

1. SON Introduction

2. Self-Configuration Algorithms (PCI, ANR)

3. Self-Optimization Algorithms (ICIC, ESM)

4. SON Coordinaton


SON Introduction


SON Introduction SON Concept – Drivers for SON

High performance required

• Growing number of BW hungry services

• Growing number of devices and change of device character (M2M)

Heterogeneous Network to be cooperatively managed

• Macro/Micro/Pico/Femto cells and Relays

Overlaying multiple networks for a single operator

• 2G/3G/LTE/WiFi

Higher operational frequencies

• Increase number of cells required / higher NW cost

Increasing complexity of networks

• Multitude / growing number of parameters with interdependencies

• Multitude of RRM algorithms working at different time scales

HO thresh PRB conf

TimeToTrig

Hysteresis

AC thresh

AC

PSched

LTE

GSM UMTS

WiFi Core

cdma

2000


OAM

SON Introduction SON Concept – Evolution Path Towards Autonomous System

1. Basic

Meas

Action

2. Managed

Meas

Action

OAM

3. Predictive

Auto

Algs

Suggested

change

Approved

OAM

4. Adaptive

Auto

Algs

Suggested

change

Approved

Policy

Long term

performance report

Adjust policy

OAM

5. Autonomic

Auto

Algs

Suggested

change

Approved

Policy

Adjust policy

One time high level

policy definition

All NEs are managed

independetly

Collect & aggregate info from NEs into

few consoles where required configs

are initiated manually

Automatic algs (e.g. SON) recommend actions

based on gathered info. Actions need to be

approved

System automatically takes action based on measurements

controlled by low level policies set/adjusted by operator

Fully integrated system is dynamically managed based

on business rules and policies


SON Introduction SON Concept – Challenges for SON

”Although SON promises huge benefits towards having reliable and optimum mobile networks, the benefits come with challenges in making

them reality” M. Marvangi (ICIMU 2011, Malaysia)

Challenge SON Solution Requirement

Flexible SON configuration:

• Fully controlled SON

• Partly controlled SON

• Fully automatic SON

SON Cooperation /

SON Coordinator

Standardization Effort for

multi-vendor and coordination

Standardization Effort for

InterRAT SON

Convince operators to change NW management

• Redefinition of OAM/Planning/Optimization Procedures

• Gain trust on automation – gradual introduction of SON

Easy migration from non-SON to SON NW

Resolve conflicts between different SON functions

Assure that SON features taken from different vendors will

cooperate

Assure that SON solutions will operate in multi-RAT NW

• E.g. single tilt change for LTE optimization might influence

badly other RATs if single antenna used


SON Introduction SON Within 3GPP Standardization (1/2)

SON

Self Configuration Self Optimization Self Healing

3GPP approach for SON (3GPP TS 32.500):

”SON algorithms themselves will not be standarized in 3GPP”

”3GPP standarizes measurements, procedures and open interfaces to support SON”

eNB

Network

Plug in

Configuration

downloading

eNB

eNB

Optimize powers

HO params

PRACH params

eNB

eNB

restart

RF failure

Ala

rm

Recovery

actions

take

over UEs

SON: set of Use Cases that govern the NW including: planning, setup & maintanence

SON objective: minimization of manual changes of RAN configuration and optimization


SON Introduction SON Within 3GPP Standardization (2/2)

SON targets / policies

SON algorithms

Settings, parameters

Nodes and interfaces

eNB, UE measurements

SO

N F

ram

ew

ork

Standard / Operator

Non-standard / Vendor dependent

Standard

Standard

Standard

Non-standard / Operator

(counters / threshold / KPI)


SON Introduction Key Parts of SON

Main areas of SON SON supporting functions


Self-Configuration


Self-Configuration Self Configuration Procedure Example

eNB

eNB

eNB

Backhaul

MME

DHCP

Server O&M

1. Auto connect to

backhaul

2. Get the IP address

4. Autosetup the

S1 connection

3. Auto software

and configuration download

(e.g. PCIs, neighbors)

5. Auto X2 with neighbor setup

6. Configure

the PCIs for

cells

7. Set the neighbor

cells (ANR)

New eNB

Already deployed eNB

Self-Configuration (S-Conf): Process which brings a network element into service requiring minimal

human operator intervention or none at all.


PCI = 6

Automated Configuration of PCI PCI Usage and PCI Assignment Criteria

PCI = 1

PCI = 3

PCI = 2

PCI = 4

PCI = 5

504 PCIs To be distributed among cells

Used at:

• Synchronization (PSS/SSS)

• Measurement reports

• Handover requests

• Cell reselection meas.

• PHY signals (CRS, DRS)

Criteria for PCI Assignment

Collision- and confusion-free assignment

Avoid reconfigurations

Adaptability to different NW deployments

Applicability to initial and evolutionary deployment scenarios

Specific PHY and operator policy constraints

.. but, PCI reuse is

required

(especially for

HetNets)


Automated Configuration of PCI Collision and Confusion Free

The assignment of PCI shall be

PCI = 1 PCI = 1

Possible Problems with PCI assignment

• UE is not able to differentiate between these two cells

• UE in connected mode can synchronize to the cell that it is not attached to

PCI = 1 PCI = 2

• If UE reports to cell 2 of strong cell 1 (left hand), the eNB can direct the user to

right hand cell 1 in HO (which is not the reported neighbor)

PCI = 1

Collision free

each two neighbors shall have different PCIs

PCI = 1 PCI = 2

PCI = 1 PCI = 2 PCI = 3

Confusion free

all neighbors of a given (center) cell shall have different PCI

Collision

two neighbors have the same PCI

Confusion

two neighbors of a given (center) cell have the same PCI

We may need a central assignment and reassignment the PCI to all eNBs

(using e.g. graph coloring algorithm in RNP tool or a central node for assigning the IDs)

Conflict avoidance approaches for distributed SON

Listen on the radio interface (Listening module at eNB before setting PCI)

UE assisted PCI detection (UE report all received PCIs, eNB assigns temporar PCI)


Automated Configuration of PCI Example Approach to Centralized PCI Assigment

Usage of Graph Coloring Approach • Use different colours for each node of the graph

• Use lowest number of different PCIs with collision / confussion free approach

1. Example network layout

2. Representation of the NW by graph • Node – cell

• Edge – neighborhood relation to direct neighbor or

neighbor of neighbor

Considered Cell

Direct neighbor

Neighbor of neighbor

4. Collision and confusion free PCI assignment

PCI B

PCI C

PCI A

PCI B

PCI C

Considered Cell

Neighbor of neighbor relation

Direct neighbor

relation

Approach: two connected nodes need to have different colours

3. Coloured Graph


Cell A

(serving)

Cell B

Cell C

Automatic Neighbor Relation Function Neighbor Relations Importance

NR Table

• Cell B

• Cell Z

No ANR

Measure Cell B

and report

Succesful HO

No Cell C

measurement

RLF and re-est

in cell C

Cell A

(serving)

Cell B

Cell C

NR Table

• Cell B

• Cell Z

With ANR

Measure Cell B

and report

Succesful HO

Cell C discovery /

measurement

and report Succesful HO

Cell C

NRT update and

HO control to cell C


Automatic Neighbor Relation Function UE Based LTE Cell Discovery (LTE ANR)

PCI 1 PCI 2

eNB

Core

NR Table

• PCI 10

• PCI 12

NR Table

• PCI 11

• PCI 13

• PCI = 1

• EGCI = 20 • PCI = 2

• EGCI = 30

PCI 2 PCI 1

7. New entry

(upd. NRT)

1. Measure signal (PCI = 2)

4. Read BCCH (ECGI = 30)

eNB

2. RRC Meas. Rep. (PCI = 2)

5. Report (ECGI = 30)

3. Request to report ECGI for PCI = 2

6. TNL address of

eNB with ECGI = 30

8. Establish X2 interface (X2 Setup)

9. New entry

(upd. NRT)


Self-Optimization


Self-Optimization Self Optimization Algorithm (High Level View)

Monitor input data

Analyse input data with

optimization algorithms

Execute corrective actions

One time self-optimization

procedure ends

Fallback

mechanism

Meet the

targets?

System state better after the

corrective actions execution?

Yes

No

Yes

No

Keep monitoring

Restore the system to

the previous state

(before the corrective

actions were executed)

UE measurements

UE signalling (e.g. RLF)

Cell global counters

Apply optimization

algorithm and

parameter adaptation


Inter-Cell Interference Coordination ICIC Scenarios

Downlink Uplink

Useful

signal Interference

eNB measures

interference UE measures interference and

sends info to eNB over

measurement reports

• Static – parameters are not changed (PFR or full reuse 1)

• Semi dynamic – slow adaptations of resources and CEU/CCU

threshold

• Dynamic ICIC scheme – frequent adjustments of parameters

(requires a lot of X2 signalling)

f

Power CEU

CCU

BW

Example semi-dynamic scheme – Partial Frequency Reuse

f

Power CEU

CCU

BW

Inner

zone Outer

zone

SON ICIC decides on: • Inner / outer zone threshold

• BW part for each zone

• Outer zone reuse scheme for neighbors

ICIC goal: Control the inter-cell interference (possible for PUSCH, PDSCH, PUCCH)


Inter-Cell Interference Coordination Example ICIC Operation on UE Mobility

1 2 3 4

5

Power

BW

f

Power

BW

f

Useful signal

Interference

1 2

3

4 5

UE is scheduled to inner subband

with low interference (due to large

pathloss) from cell 2

Cell 1 Cell 2

UE is scheduled to

outer subband where

cell 2 doesn’t transmit

UE is handed over from

cell 1 to cell 2

UE is scheduled to

outer subband where

cell 1 doesn’t transmit

UE is scheduled to inner subband

with low interference (due to large

pathloss) from cell 1


Inter-Cell Interference Coordination Proactive vs Reactive Approaches

Reactive approach Proactive approach (Dynamic PFR/SFR)

Using indicators of experienced interference

(interference is present)

Announcing scheduling decisions

(requires a lot of signalling)

eNB eNB

• HII = bitmap of UL PRB – interference sensitivity

• RNTP = bitmap of DL PRB – power threshold exceeding

I’ll schedule UE at

PRB x I’ll not use PRB x

eNB eNB

• OI = per UL PRB report on experienced interference

I’ve measured

interference at

PRB x

I’ll adapt power levels

of UEs to decrease

interference 1 2 1 2


Energy Saving Management Example Daily Traffic Profile

0

10

20

30

40

50

60

70

80

90

100

0-1

1-2

2-3

3-4

4-5

5-6

6-7

7-8

8-9

9-10

10-1

1

11-1

2

12-1

3

13-1

4

14-1

5

15-1

6

16-1

7

17-1

8

19-2

0

20-2

1

21-2

2

22-2

3

23-0

[%]

Hour

Load voice % of max capacity of cell Load data % of max capacity of cell

RF output power % of max output power

Possiblity to

switch off cell

High traffic

scenario


Energy Saving Management ESM Introduction and Usage Scenario

ESM goal: Cost savings and reduced environmental impact. Focused on automatic

adaptations of offered capacity by NW to actual traffic demand at given point of time

Example actions • Radio solutions:

• Not scheduling in certain subframes

• Switch off some antennas to save power in MIMO modes

• Adapt transmission power

• Switch off some carrierrs

• NW solutions:

• Switch off cells (e.g. for HeNBs, capacity booster Pico cells etc)

Example scenario – capacity booster / capacity limited NW Coverage based macro-cells and capacity based pico-cells

Switch-off capacity-boosters when

capacity is no longer needed

High traffic situation

(e.g. busy hour)

Low traffic situation

(e.g. night hours)

No-ES

No-ES

No-ES

No-ES No-ES

No-ES

No-ES

EScompensate

(macrocell)

ESaving

(cap booster)

ESaving ESaving

ESaving

ESaving ESaving

Considered scenarios • Cell overlaid use case

• eNB can enter ES mode if there’s radio coverage from other

system

• Capacity limited network use case

• Coverage area of a group of eNBs is taken care by one of

more of its eNBs while others go into ES state


SON Coordinator


Interaction Between SON Use Cases Problems with Interactions

UE

measurements

eNB

measurements

SON

Use Case 3

SON

Use Case 2

SON

Use Case 1

Parameter 1 Parameter 2

• Can alter the same parameter

• Interact with each other

• Can work against each other

• Performance depends on

multiple use cases

Multiple SON use cases

SON coordination definition (3GPP TS 32.522): ”SON Coordination means preventing or resolving conflicts or negative influences between SON functions to make SON functions comply with operator policy”


Interacting Use Cases - Example Interactions Between Handover Parameter Optimization and Load Balancing

SON algorithms Control parameters KPIs / metrics

Load balancing

HO param

optimization

HO offset

Hysteresis

TTT

HO failure

ratio

(HPIHOF)

HO ping

pong ratio

(HPIHPP)

RLF ratio

(HPIRLF)

Virtual

load

We

igh

ted

su

m:

HP

= w

1 *

HP

I HO

F +

w2

* H

PI H

PP +

w3

* H

PI R

LF

Metric conflict

Unsatisfied

users

Source: Socrates D5.9 Final report


SON Coordinator

Interacting Use Cases – Example SON Coordinator – Cooperative Use Case Example (HPO and LB)

SON algorithms Control parameters KPIs / metrics

Load

balancing

HO param

optimization

HO offset

Hysteresis

TTT

HO failure

ratio

HO ping

pong ratio

RLF ratio

Virtual

load

Autognostics

Operator policy

Requested changes

Alig

nm

ent

COO1 HPO priorty

COO2 LB priority

COO3 Abnormal situation

detect/solve

Conflict detection and

resolution

E.g. settings of metrics

weights, setting assured

virtual load

Collects and processes

PM/FM/CM

Coordination policy

selection



Interacting Use Cases - Example HPO and LB Cooperative Use Case – Example Results

0

5

10

15

20

25

30

No SONHPO

LBHPO&LB

HPO&LB&Coordinator

Av. No of unsatisfied users (%)

Call drop ratio (%)

HO pingpong ratio (%)

HO failure ratio (%)


Pe

rfo

rma

nce

(%

)


Thank you for your attention!

SON in LTE - additional materials

Technology

Transcript of SON in LTE - additional materials