Post on 29-Nov-2014
FDD-LTE Radio ICIC
ZTE University
Contents
ICIC Introduction
ICIC theory and scheme
ICIC Performance
ICIC Application
What Is ICIC?
ICIC (Inter cell Interference Coordination)
A set of techniques that based on
FFR/SFR( fractional frequency reuse/soft frequency
reuse) and power control/allocation, adaptive
scheduling. It can be used to suppress ICI( inter cell
interference) and to achieve improved coverage
area compared to universal frequency
reuse( frequency reuse factor is equal to one)
network deployment and keep proper system
spectrum efficiency simultaneously.
Interference coordination & management –
Overview
There are three main interference coordination &
management methods
Interference coordination & management methods for handling mono-frequency interference
Mono-frequency interference causes cell edge spectrum efficiency deteriorating
High spectral efficiency requirement needs mono-frequency network deployment
Interference
randomization
Interference
coordination
based on SFR/FFR
Interference
cancellation
Interference coordination & management –
Comparison
Though does not decrease interference’s power but whitens it.
SINR improvement is limited. Sole utilization of randomization can
not satisfy the SINR requirement of LTE.
Easy to implement.
Interference
randomization
Interference
cancellation
High complexity
Strict resource allocation requirement
Strict inter cell synchronization requirement
Interference
coordination
based on FFR
SFR/FFR allocates adjacent cells’ cell edge users orthogonal frequency, so inter
cell interference is decreased. Residual interference is decreased by
pro-active mode and passive mode interference coordination based on
indicators exchanging between different adjacent eNodeBs.
Balance of complexity and performance.
The last one for
consideration
Combine
ICIC types for LTE
Based on frequency adjustment
Type-1: Static ICIC;
Type-2: Semi-static ICIC;
Type-3: Dynamic ICIC.
Modes for non-static ICIC:
Mode-1: Pro-active Mode;
Mode-2: Reactive Mode.
High Complexity, Not easy Implementation,
Middle Overhead, Middle CAPEX and Low
OPEX, Suitable to load of 35%~70%.
Performance improved more. Fit to slowly
varying load.
1 Type 1 Static ICIC
2 Type 2 Semi-Static ICIC
3 Type 3 Dynamic ICIC
Low Complexity, Easy Implementation,
Low Overhead, Low CAPEX and High OPEX,
Fit to load of 35%~50%, Performance lightly
improved. Not fit to varying load.
High Complexity, Hard Implementation, High
overhead, High CAPEX and Low OPEX, Fit to
load of 35%~70%, Performance improved
most. Fit to varying load.
Comparison of Different ICIC Types in LTE
Contents
ICIC Introduction
ICIC theory and scheme
ICIC Performance
ICIC Application
Universal Frequency Reuse (Reuse factor = 1)
Frequency reuse factor 1
All cells and sectors use
the same frequency
which is showed by the
same grey color.
ICI is generated
Sector 2
Sector 1Sector 3
Different-Frequency Reuse (Reuse factor = 3)
Frequency reuse factor 3
neighbor sectors have
different frequency
which is showed by the
different colors (red
green and blue).
ICI is decreased
Sector 2
Sector 1
Inner
Sector 3
Soft Frequency Reuse
Fractional Frequency Reuse (1<Reuse factor<3)
1< Frequency reuse factor <3
Cell edge region in neighbor cells
have different frequency which is
showed by the different colors
(red, green and blue). But cell
center region in neighbor cells
have the same frequency which is
showed in the grey color.
ICI is somehow decreased
compared with mono-frequency
reuse.
In SFR, total band=A+B+C, D=total
band – cell edge band. In FFR,
total band=A+B+C+D.
Sector 2
Sector 1
Inner
Sector 3
C A
B D
ICIC Modes for LTE
Modes for Static ICIC
Type-1: FFR;
Type-2: SFR/SFR2.
Modes for Semi-Static ICIC
Type-1: Pro-active SFR/SFR2;
Type-2: Reactive SFR/SFR2.
Static ICIC in LTE-introduction
Static ICIC
No coordination between different eNodeBs;
Based on FFR/SFR/SFR2, i.e. , Try to allocate orthogonal cell edge
resources to neighbor cells. The frequency reuse factor target for
cell edge is 3, and the frequency reuse factor target for cell center
is 1. i.e., both the cell edge efficiency and system efficiency is under
consideration in design.
Different resources allocation is allowed and power control is
allowed for interference mitigation. Such as FFR, SFR, SFR2.
Static ICIC in LTE-Frequency Allocation
Scheme
Different Frequency Resource Allocation schemes
FFR (Fractional Frequency Reuse)
In FFR, one frequency band in a sector is defined as use or not use,
The Power for different frequency band is the same. The system
equivalent frequency reuse factor in the interval of [1, N].
System bandwidth divided into N orthogonal parts. Each sector
edge use one part orthogonal to neighbor sectors. Each sector
center use the same part with neighbor sectors.
Static ICIC in LTE-Frequency Allocation Scheme
SFR (Soft Frequency Reuse)
In SFR, one frequency band in a sector is not defined as use or not use, but defined as how much power allocated the frequency was used in a cell. The system equivalent frequency reuse factor in the interval of [1, N].
Main principle for SFR:
1. System bandwidth divided into N orthogonal parts. For each sector, select some parts as main carriers, others as auxiliary carriers, The power of main carriers are higher than auxiliary carriers ;
2. Main carriers for different neighbor sectors are orthogonal;
3. Main carriers can be used for overall sector, but auxiliary carriers can only be used in cell center;
4. By Adjusting the proportionality between main carrier power and auxiliary carrier power, SFR can adapt to the load distribution in cell edge and cell center.
SFR2(Combination of SFR and FFR)
Static ICIC in LTE-Frequency Allocation
Scheme Different Frequency Resource Allocation schemes
FFR
system
bandwidth
divided into 4
bands, Cell
Center reuse
1,Cell Edge
reuse 3
SFR
system
bandwidth
divided into 3
bands, Cell
Center reuse
(1 3), Cell
Edge reuse 3.
CA B D
B,C are not used. A is first allocated
to Cell edge user (CEU) . D is only
used for Cell center user (CCU).
Unallocated part of A can be used
for CCU together with D.
P Cell 1
F CA B D
A,C are not used. B is first allocated
to Cell edge user (CEU) . D is only
used for Cell center user (CCU).
Unallocated part of B can be used for
CCU together with D.
P Cell 2
F CA B D
A,B are not used. C is first allocated
to Cell edge user (CEU) . D is only
used for Cell center user (CCU).
Unallocated part of C can be used for
CCU together with D.
P Cell 3
F
CA B
D1=B+C
A is first allocated to CEU . D1 is only
used for CCU. Unallocated part
of A can be used for CCU together
with D1.
P Cell 1
F CA B
D2=A+C
B is first allocated to CEU . D2 is only
used for CCU. Unallocated part
of B can be used for CCU together
with D2.
P Cell 2
F CA B
D3=A+B
C is first allocated to CEU . D3 is only
used for CCU. Unallocated part
of C can be used for CCU together
with D3.
P Cell 3
F
Static ICIC in LTE-Frequency Allocation
Scheme
Different Frequency Resource Allocation schemes
SFR2
system
bandwidth
divided into 4
bands, Cell
Center reuse
(1 3), Cell
Edge reuse 3.
CA B D
A is first allocated to CEU. D1 is only
used for CCU. Unallocated part of A
can be used for CCU together with
D1. In D1, D is first allocated to CCU.
P Cell 1
F CA B D
P Cell 2
F CA B D
P Cell 3
F
D1=B+C+D
B is first allocated to CEU. D2 is only
used for CCU. Unallocated part of B
can be used for CCU together with
D2. In D2, D is first allocated to CCU.
D2=A+C+D
C is first allocated to CEU. D3 is only
used for CCU. Unallocated part of C
can be used for CCU together with
D3. In D3, D is first allocated to CCU.
D3=A+B+D
Semi-static ICIC in LTE-introduction
Semi-Static
Coordination between different eNodeBs; Frequency allocation adapts to
load distribution in Cell edge and cell center. Reallocation is done on a time
scale corresponding to seconds. X2 signaling such as HII, OI and RNTP
are supported.
Based on FFR, i.e. , Try to allocate orthogonal cell edge resources to
neighbor cells. The frequency reuse factor target for cell edge is 3, and the
frequency reuse factor target for cell center is 1. i.e., both the cell edge
efficiency and system efficiency is under consideration in design.
Different resources allocation is allowed and power control is allowed for
interference mitigation. Such as FFR, SFR, SFR2.
Semi-static ICIC in LTE-X2 signaling
X2 signaling interacting
Introduction
Interacting signaling: HII and OI are used for uplink semi-static ICIC.
RNTP is used for downlink semi-static ICIC.
Interacting mode: HII and RNTP are pro-active mode. OI is reactive
mode.
Interacting interval: Several tens of milliseconds for semi-static ICIC.
Interacting granularity: Each RB has corresponding indicators.
Interacting flow chart: different respectively for different indicators.
Interacting cells: cells in the neighbor cell list(NCL).
HIIGenerate HII for
CEU PRB
S
C
H
E
D
U
L
E
R
System load
statistics
Neighbor
cells’HII
Classify CEU
and CCU
Allocate time-frequency
and power resources to
CCU and CEU
Decide CCU and
CEU Band allocation
UE’s Tx power
and SINR statistics
UE’s RSRP
report
If high
load, power
Of HII
indecated
PRBs
be lowered
Service Type
Power
Control
Decide UE’s power
variable
IoT test on
Each PRB
If lightly load,
HII indicated
PRBs will not
be allocated to
CEU and high
SINR CCU
Semi-static ICIC in LTE-X2 signaling-HII X2 signaling interacting flow chart:
HII for Uplink
If one PRB is allocated to CEU by scheduler, the HII indicator for the PRB is generated as 1,
otherwise 0. The HII bitmap is generated for each target cell based on cell related CEU’s HII
Indicator statistics in report interval. Upon receiving HII bitmap, in lightly load the HII indicated
PRBs will not be allocated to CEU and high SINR CCU; in high load the power of HII indicated
PRBs will be lowered.
Semi-static ICIC in LTE-X2 signaling-OI X2 signaling interacting flow chart:
OI for Uplink
The OI indicator for each PRB is generated in the IOT test. OI have four values: high, medium,
low, and null. The bitmap is generated based on RNTP indicators statistics in report interval
and sent to all neighbor cells in NCL by X2 interface. If OI from strong interfering cells received,
the Tx power of the OI indicated PRB should be Adjusted based on OI, UE’s SINR and Tx
Power statistics.
OIGenerate OI for
CEU PRB
S
C
H
E
D
U
L
E
R
System load
statistics
Neighbor cells’OI
Classify CEU
and CCU
Allocate time-frequency
and power resources to
CCU and CEU
Decide CCU and
CEU Band allocation
UE’s Tx power
and SINR statistics
UE’s RSRP
report
Service Type
Power
Control
Decide UE’s power
variable in inner loop
Power control
IoT test on
Each PRB
Decide uplink
power
variable in
outer loop
Power control
for overall cell
Semi-static ICIC in LTE-X2 signaling-
Downlink-RNTP X2 signaling interacting flow chart:
RNTP for Downlink
If one PRB is allocated by scheduler, the RNTP indicator for the PRB is generated by eNodeB
as follows. The RNTP bitmap is generated based on RNTP indicators statistics in report
interval and sent to all neighbor cells in NCL. Upon receiving RNTP bitmap, the PRB with
RNTP=1 will not be allocated to CEU whose CQI is too small.
S
C
H
E
D
U
L
E
R
System load
statistics
Generate RNTP for
each PRB
Neighbor
cells’RNTP
Classify CEU and
CCU
Allocate time-
frequency and power
resources to CCU
and CEU
Decide CCU and
CEU Band allocation
UE’s CQI report
and power
statistics for UE’s
PRB
UE’s RSRP
report
Service Type
( )
max_
( )
max_
( ) if
( ) 0;
no promise about the upper
( )limit of is made
( ) 1;
A PRBthresholdp
nom
PRB
A PRB
p
nom
PRB
E nif RNTP
E
RNTP n
if
E n
E
RNTP n
Contents
ICIC Introduction
ICIC theory and scheme
ICIC Performance
ICIC Application
ICIC Simulation Results-Semi-Static Uplink
Different system load
simulation.
Frequency reuse scheme SE ESE RB Usage
bps/Hz/cell
bps/Hz/user
%
Load=90%
FR=1 1.027 0.0281 93.87
SFR 1.060 0.0217 88.32
HII 1.019 0.0282 93.41 Load=80%
FR=1 0.934 0.0403 82.18 Static SFR 0.969 0.0439 76.26
Semi-static SFR+HII 0.942 0.0419 81.66
Load=70%FR=1 0.873 0.058 72.55
Static SFR 0.914 0.0594 67.74
Semi-static SFR+HII 0.884 0.0642 72.34 Load=50%
FR=1 0.735 0.0647 54.22
Static SFR 0.780 0.0785 50.79
Semi-static SFR+HII 0.761 0.0798 52.96 Load=35%
FR=1 0.612 0.1006 37.75
SFR 0.628 0.075 34.33
HII 0.627 0.0905 37.79
ICIC Simulation Results-Semi-Static Uplink
ESE figure for Different
system load simulation.
ESE
0
0.02
0.04
0.06
0.08
0.1
0.12
99% 90% 80% 70% 50% 35%
Load
bps/Hz
FR=1
SFR
HII
OI
HII+OI
ICIC Simulation Results-Semi-Static Uplink
SE figure for Different
system load simulation.SE
0.000
0.200
0.400
0.600
0.800
1.000
1.200
99% 90% 80% 70% 50% 35%
Load
bps/Hz
FR=1
SFR
HII
OI
HII+OI
ICIC Simulation Results-Semi-Static Uplink
Some comments
HII is introduced into uplink semi-static ICIC compared with
uplink static ICIC.
Compared with FR=1, semi-static ICIC using HII can improve
cell edge spectrum efficiency.
Compared with static SFR, under high load and low load
scenarios semi-static ICIC is better; under medium load,
semi-static ICIC has near performance.
Compared with static SFR, semi-static ICIC is more capable of
tracking system load variation.
ICIC Simulation Results-Semi-Static Downlink
70% load(k=0.15)
FreqUse Type
CEU Ratio
OC RB PwRatio SE ESE ALLRBratio Avg.Bler
bps/Hz/cell
bps/Hz/user bps/Hz/user %
FR=1 0.5 12 1 1.7469 0.0329 72.7162 5.6788
SFR 0.4 16 2 1.5803 0.0380 69.6275 4.3261
45%load(k=0.10)
FreqUse Type
CEU Ratio
OC RB PwRatio SE ESE ALLRBratio Avg.Bler
bps/Hz/cell
bps/Hz/user bps/Hz/user %
FR=1 0.4 16 1 1.1984 0.0206 45.8041 4.0891 SFR 0.4 16 2 1.1011 0.0235 43.9899 2.6279
ICIC Simulation Results-Semi-Static Downlink
Some comments
For downlink ICIC, individual frequency band allocation
will not have obvious advantage to interference mitigation.
Interference mitigation depend on the power allocation
for CCU and CEU. For CEU, signal transmit power is
higher. So performance increasing of CEU must be at the
cost of CCU performance decreasing. From the statistics,
in order to improve ESE, SE is degraded. It can be seen
that, SFR can improve ESE at the cost of SE.
Contents
ICIC Introduction
ICIC theory and scheme
ICIC Performance
ICIC Application
ICIC Application Scenario Rural
ICIC Be suitable;
The service load change very slowly;
Rural Scenarios Pls. See figures below.
Sub-Urban
ICIC Be suitable;
Important future living place.
Sub-Urban Scenarios Pls. See figures
below.
ICIC Application Scenario Urban
static ICIC not suitable;
density people and complicated radio propagation environment.
Service load change more quickly because of subscribers
moving;
Urban Scenarios Pls. See figures below.
ICIC Roadmap
Stage 1-2009Q4 Stage 2-Planning
Dynamic ICICStatic ICIC
Semi-static ICIC