RRM Overview
Slide 1
NokiaEDU
RRM Overview
FDD and TDD LTE Radio Planning
[FL17SP/TL17SP]
RA4120
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RRM Overview
Slide 2
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RRM Overview
Slide 5
RA4120 – Learning Elements list
➢Introduction & Roadmaps
➢LTE/EPS Overview
➢LTE Air Interface
➢Air Interface Overheads
➢RRM overview
➢LTE Link Budget
➢Cell Range (Coverage Planning)
➢Radio Capacity Planning
➢Nokia eNodeB LTE Solution
➢Initial Parameters Planning
➢LTE Performance Simulations
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RRM Overview
Slide 6
Module Objectives
After completing this module, the participant will be able to:
• Review the main LTE RRM features
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RRM Overview
Slide 7
Module Contents
• Radio Resource Management (RRM) Overview
• Scheduler
• Adaptive Modulation and Coding (AMC)
• Outer Loop Quality Control (OLQC)
• Power Control
• Multiple Inputs Multiple Outputs (MIMO)
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RRM Overview
Slide 8
Module Contents
• Radio Resource Management (RRM) Overview
• Scheduler
• Adaptive Modulation and Coding (AMC)
• Outer Loop Quality Control (OLQC)
• Power Control
• Multiple Inputs Multiple Outputs (MIMO)
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RRM Overview
Slide 9
Radio Resource Management (RRM) Overview
Scope of RRM:
• Management and optimized utilization of the (scarce) radio resources
• Provision for each service/bearer/user an adequate QoS (if applicable)
eNB
• Increasing the overall radio network capacity and optimizing quality
• RRM is located in eNodeB
X2
LTE-Uu
LTE-UE
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Evolved Node B
(eNB)
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RRM Overview
Slide 10
RRM functions
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Nokia LTE RRM Framework consists of RRM building blocks, RRM functions and RRM algorithms.
L3 RRM:
ICIC: Selects certain parts of the Frequency Spectrum of the LTE Carrier. Exclusively for PDSCH and
PUSCH on Cell Basis. Remaining channels not affected.
DRX/DTX algorithm: To support provisioning of measurement gaps for Inter-RAT-HO and DRX/DTX
mode in later product releases. Not supported in RL09.
Differences with RRM WCDMA:
•Softer and Soft handovers are not supported by the LTE system
•LTE requirements on power control are much less stringent due to the different nature of LTE radio interface
i.e. OFDMA (WCDMA requires fast power control to address the “Near-Far” problem and intra-frequency
interferences)
•On the other hand LTE system requires much more stringent timing synchronization for OFDMA signals.
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RRM Overview
Slide 11
RRM Framework
UE scope: Handover control, power control, Adaptive Modulation and Coding, outer link quality
control, MIMO
Cell scope: Radio Admission Control, Congestion Control
eNode B scope: Packet Scheduler (cell scope for simpler implementation)
RAN scope: Load Balancing
Multi-RAT scope: Interworking with GSM/EDGE, UMTS and CDMA2000, inter-RAT HO
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RRM Overview
Slide 12
RRM Framework
Functional Description of the different RRM Modules
• Radio Admission Control : Admission control will be in charge of deciding when new users (or
mobility users) are allowed to establish bearers in the cell
• Handover control: Is in charge of the mobility control within the LTE RRM. Based on UE reported
events it will select the appropriate target cell for HO and initiate mobility procedures.
• Packet Scheduler: Is in charge of UL and DL scheduling every TTI and resource allocation. PS will
decide which users are scheduled on a TTI basis, the location and the amount of resources
allocated to each user.
• AMC (OLQC, OLLA): AMC will perform link adaptation tasks to ensure radio resources are used in
the most efficient way possible.
• MIMO: This module is in charge of selecting whether Transmit diversity, Spatial multiplexing or
dynamic switching between previous two modes will be employed for every user based on UE
feedback
• Power control: For DL it will be a semi static configuration but for UL RRM will provide feedback for
closed loop power control to reduce UL interference.
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RRM Overview
Slide 13
RRM Framework: Time Scale of RRM Functions
Time Scale
Traffic, Channel and 100 s
Location Variations
Call
Duration
Radio Admission Control
Connection Mobility Control
10 s
Load Balancing , Congestion Control
Layer 3
RRM
Interhandover
Time
1s
L3 Signaling
Delay
100 ms
Burst or Packet
Duration
13
Channel
Fading
Time
10 ms
LTE TTI
1 ms
Slow UL
Power Control
Dynamic
(open/closed Slow UL LA/AMC, MIMO
Loop)
Slow UL ATB
Control
Outer Link Quality Control (OLQC)
Fast DL AMC
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UE
DRX/DTX
Control
Layer 2
RRM
Packet Scheduling (UL/DL), fast ATB
ATB = Adaptive Transmission Bandwidth
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RRM Overview
Slide 14
Module Contents
• Radio Resource Management (RRM) Overview
• Scheduler
• Adaptive Modulation and Coding (AMC)
• Outer Loop Quality Control (OLQC)
• Power Control
• Multiple Inputs Multiple Outputs (MIMO)
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RRM Overview
Slide 15
LTE RRM: Scheduling
- Motivation
• Bad channel condition avoidance
15
CDMA
OFDMA
Single Carrier transmission
does not allow to allocate
only particular frequency
parts. Every fading gap
effects the data.
The part of total available
channel experiencing bad
channel condition (fading) can
be avoided during allocation
procedure.
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RRM Overview
Slide 16
Scheduler (UL/DL)
•
•
•
•
•
Cell-based scheduling (separate UL/DL scheduler per cell)
Scheduling air interface resource on a 1ms × 12sub-carrier (PRB pair) basis, (also allocation type for DL)
Scheduler controls UEs & assigns appropriate grants per TTI
Proportional Fair (PF) resource assignment among UEs
Uplink:
• Channel unaware scheduling (frequency hopping) in RL20
• Interference aware scheduling in RL30
• Channel aware UL scheduling in RL40
• Downlink:
• Channel aware DL scheduling - Frequency Domain Packet Scheduling (FDPS) - based on CQI with
resources assigned in a fair manner
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RRM Overview
Slide 17
Downlink Scheduler
Algorithm
Start
- Determine which PRBs are available (free) and can be allocated to UEs
- Allocate PRBs needed for common channels like SIB, paging, and
random access procedure (RAP)
- Final allocation of UEs (bearers) onto PRB. Considering only the PRBs
available after the previous steps
• Pre-Scheduling: All UEs with data available for transmission based on
the buffer fill levels
• Time Domain Scheduling: Parameter max​Num​Ue​Dl decides how
many UEs are allocated in the TTI being scheduled
• Frequency Domain Scheduling for Candidate Set 2 UEs: Resource
allocation in Frequency Domain including number & location of allocated
PRBs
Evaluation of available resources (PRBs/RBGs )
for dynamic allocation on PDSCH
Resource allocation and scheduling
for common channels
DL scheduling of UEs :
Scheduling of UEs /bearers to PRBs /RBGs
End
Start
Pre -Scheduling :
Select UEs eligible for scheduling
-> Determination of Candidate Set
1
Time domain scheduling
of UEs according to simple criteria
-> Determination of Candidate Set
2
Frequency domain scheduling
of UEs /bearers
-> PRB /RBG allocation to UEs
/bearers
End
SIB: System Information Broadcast
MAX_#_UE_DL depends on the bandwidth: 7UEs (5 MHz), 14UEs (10MHz), 17UEs (15MHZ) and 20 UEs (20MHz)
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RRM Overview
Slide 18
Uplink Scheduler
Algorithm
- Evaluation of the #PRBs that will be assigned to UEs
- Available number of PRBs per user: resources are assigned via PRB groups (group of consecutive PRBs)
•Time domain:
- The Maximum Number of Ue’s in Uplink which can be scheduled per TTI time frame is restricted by an O&M
parameter (maxNumUeUl) and depends on the bandwidth: 7 UEs (5 MHz), 14 UEs (10MHz), 17 UEs (15MHz) and
20 UEs (20MHz)
Frequency Domain:
- Uses a random function to assure equal distribution of PRBs over the available frequency range (random
frequency hopping, channel unaware RL20)
a)
b)
Example of allocation in frequency domain:
Full Allocation: All available PRBs are assigned to the
scheduled UEs per TTI
Fractional Allocation: Not all PRBs are assigned. Hopping
function handles unassigned PRBs as if they were allocated to
keep the equal distribution per TTI
PRBs allocated for PRACH, PUCCH are excluded for PUSCH
scheduling
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RRM Overview
Slide 19
Uplink Scheduler
IAS: Interference Aware Scheduler UL (RL30)
Improvement in UL coverage by optimizing the cell edge performance
• Flexi eNodeB takes into account the noise and interference measurements together with the UE Tx power density
(= UE TX power per PRB) when allocating PRBs in the frequency domain
• Cell edge users are assigned to frequency sub-bands with low measured inter-cell interference
• Up to 10% gain for cell edge users in low and medium loaded networks
• Easier to implement than channel aware scheduling (no sounding reference signal used)
eNode B measured
interference
PRBs
subband with high interference
subband with low
interference
subband with medium
interference
IAS gain in Dimensioning tool (LiBu)
– IM > 1 dB: 1 dB
– IM ≤ 1 dB:0 dB
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Feature ID(s): LTE619
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RRM Overview
Slide 20
Uplink Scheduler
Channel Aware Scheduler (RL40)
UE specific channel state
information (CSI) is
derived from:
- PUSCH
- sounding reference
signals (SRS)
The eNB evaluates the Channel State Indicator (CSI) of the UEs in which both the Sounding Reference Signal
(SRS) and PUSCH transmission are taken into account for an improved estimation of the channel quality.
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RRM Overview
Slide 21
Uplink Scheduler
Channel Aware Scheduler (RL40)
step 1: resource
evaluation
Uplink scheduling function now updated for CAS
- 4. How to assign available resources to scheduled UEs?
• UL step 4a: How many resources shall be allocated to each UE?
- RR
- EX (RL20)
- WRR (RL30)
• UL step 4b: Where in the spectrum shall the PRBs of each UE be
allocated?
- CUS
- IAS (RL30)
- CAS (RL40)
step 2: pre-scheduling
CS1 (candidate set 1)
step 3: TD scheduler
CS2 (candidate set 2)
UL step 4a: FD
scheduler, #PRBs for
each UE
UL step 4b: FD
scheduler, PRB
positions
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RRM Overview
Slide 22
LTE786: Flexible Uplink Bandwidth (RL50)
• It allows blanking of the outer edges of the uplink channel bandwidth
Blanked
Resource Blocks
PUCCH
PRACH
PUCCH
Blanked
Resource Blocks
PUSCH
•Achieved by increasing the bandwidth allocated to PUCCH, and not using the resources
situated at spectrum edge.
•LTE transmission bandwidth thus reduced, leaving blanked areas at bandwidth edge.
•Blanked areas serve as a guard band for reducing out of band emissions
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RRM Overview
Slide 23
▪
▪
▪
▪
▪
The LTE944 functionality makes it possible to exclude
certain uplink resources from being used
As a result, no transmission will take place in certain
sections of the uplink band
Only PUSCH resources can be „muted” with LTE944
PUCCH resources can be blanked with another
functionality: LTE 786 (Flexible UL Bandwidth)
PRACH position can be configured using system
parameters
Frequency
LTE944: PUSCH Masking (RL60)
These uplink resources
will never be allocated
Time
Direct reasons behind the feature concept – specific situation in the South Korea 1800 MHz band
No uplink PUSCH transmission allowed in certain sections of the uplink.
Result: fragmented uplink allocations
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RRM Overview
Slide 24
LTE825: Uplink outer region scheduling (FDD-LTE 15A)
• It allows the PUSCH to use one of the blanked regions by the ‘LTE786 Flexible Uplink Bandwidth’
• Outer region scheduling can allocate resources to either the PUSCH or PRACH
• PRACH requires at least 6 Resource Blocks in the outer region
• for effective PUSCH scheduling it is recommended that the outer region is always at least 3 Resource Blocks
• a single UE cannot be allocated Resource Blocks from both the central and outer regions
Blanked
Resource Blocks
PUCCH
PRACH /
PUSCH
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PUCCH
PUSCH
PUSCH /
PRACH
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RRM Overview
Slide 25
not specifically
linked to
LTE825
LTE825: Uplink outer region scheduling (FL15A)
Sounding Reference Signal (SRS)
• A new SRS parameter is introduced with FDD-LTE15A: srsActivation
• In addition, the SRS configuration starts to be allocated dynamically by the eNode B rather than relying upon the
srsConfiguration parameter
• selected according to the bandwidth available to the SRS
• Within the context of LTE825, the SRS is not permitted within the outer PUSCH region
• has an impact upon channel aware scheduling
LNCEL: srsActivation
activates/deactivates SRS
feature in the cell.
False (0), True (1)
Default: 0
must be set to ‘true’ if:
ulsSchedMethod = 'channel aware'
and actPuschMask = 'false'.
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RRM Overview
Slide 26
LTE 1059: Multi-Cluster Scheduling (FL16)
Before LTE1059
LTE944 PUSCH masking
•
It allows to exclude certain uplink resources
from being used, therefore no transmission
will take place in certain sections of the
uplink band (PRBs are blanked)
PUSCH area 1
26
•
It allows using blanked PRBs from one
side of spectrum for PUSCH scheduling,
in scenario when LTE786 Flexible uplink
bandwidth is in use
PUSCH area 2
Blanked PUSCH
•
•
LTE825 Outer region scheduling
PUSCH area 1
PUCCH
Blanked PUSCH
PUSCH area 2
PUCCH
Both of the functionalities cause that PUSCH is fragmented into 2 areas
As uplink resource allocations have to be continuous. As a result PUSCH division is causing
peak UE throughput to decrease as single UE has to be scheduled in only one of PUSCH areas
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RRM Overview
Slide 27
LTE 1059: Multi-Cluster Scheduling (FL16)
Motivation for LTE1059
• In case when LTE944 PUSCH masking or LTE825 Outer region scheduling is used in the network, PUSCH spectrum is
divided into several PUSCH areas
• Divided PUSCH causes uplink peak UE throughput decrease when only one UE is scheduled in single TTI,
because UE can be scheduled only in one PUSCH area at the time
• LTE1059 Multi-cluster scheduling introduces possibility to schedule UE in two PUSCH areas at the same time when
there is only one UE scheduled in single TTI
Before: Single UE can be scheduled
in only one PUSCH area in single TTI
PUCCH PUSCH area 1
PUSCH area 2
PUCCH
After: Single UE can be scheduled in two PUSCH
areas in single TTI. Peak throughput is increased
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RRM Overview
Slide 28
Module Contents
• Radio Resource Management (RRM) Overview
• Scheduler
• Adaptive Modulation and Coding (AMC)
• Outer Loop Quality Control (OLQC)
• Power Control
• Multiple Inputs Multiple Outputs (MIMO)
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RRM Overview
Slide 29
LTE RRM: Link Adaptation by AMC (UL/DL)
Optimizing air interface efficiency
• Motivation of link adaptation: Modify the signal transmitted to and by a particular user according to the signal
quality variation to improve the system capacity & coverage reliability.
• It modifies the MCS (Modulation & Coding Scheme) & the transport block size (DL) and ATB (UL)
• If SINR is good then higher MCS can be used  more payload per symbol  more throughput.
• If SINR is bad then lower MCS should be used (more robust)
• Nokia eNodeB performs the link adaptation for DL on a TTI basis
• The selection of the modulation & the channel coding rate is based:
• DL data channel: CQI report from UE
• UL: BLER measurements in Flexi LTE BTS
Adaptive Transmission Bandwidth (ATB): Calculates maximum number of PRBs that UL SCH can be
assigned to a particular UE taking into account UE QoS profile and available UE power headroom
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LTE31: Link Adaptation by AMC
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RRM Overview
Slide 30
Link Adaptation / AMC for PDSCH
START
•Procedure:
- Initial MCS is provided by O&M (parameter
iniMcsDl) & is set as default MCS
- If DL AMC is not activated (O&M parameter
ENABLE_AMC_DL) the algorithm always uses this
default MCS
- If DL AMC is activated, HARQ retransmissions use
the same MCS as for initial transmissions of the
packets
- If DL AMC is activated, initial transmission uses an
MCS based on averaged CQI value reported by UE
for allocated PRBs
Retrieve Default MCS
no
Dynamic AMC
active?
HARQ
retransmission?
yes
no
Use Default MCS
Determine avaraged CQI
value for allocated PRBs
Use the same MCS as for
initial transmission
Determine MCS
END
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RRM Overview
Slide 31
Link Adaptation / AMC for PUSCH
•Functionality
- UL LA is active by default but can be deactivated by O&M parameter actUlLnkAdp. If not active, the initial MCS
(iniMcsUl) is used all the time
LNCEL: actUlLnkAdp;
Activate uplink link adaptation;
off (0), slowAmcOllaATB (4), eUlLa (5),
fUlLa (6); Default: eUlLa (5)
- UE scope
LNCEL: iniMcsUl
Initial MCS in uplink;
0...28,
Default: 5
- In initial option (slowAmcOllaATB nowadays) two parallel algorithms adjust the MCS to the radio channel
conditions:
• Inner Loop Link Adaptation (ILLA):
- Slow Periodic Link adaptation (20-500ms) based on BLER measurements from eNodeB (based on SINR in
future releases)
• Outer Loop Link Adaptation (OLLA): event based
- In case of long Link Adaptation updates and to avoid low and high BLER situations, the link adaptation can
act based on adjustable target BLER:
- “Emergency Downgrade” if BLER goes above a MAX BLER threshold (poor radio conditions)
- “Fast Upgrade” if BLER goes below of a MIN BLER threshold (excellent radio conditions)
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RRM Overview
Slide 32
Comparison: DL & UL Link adaptation for PSCH (4/6)
Downlink
•
Fast
•
Uplink
•
slow periodical ~30ms
channel aware CQI based
•
Channel aware average BLER based
•
MCS selection 1 out of 0-28
•
MCS adaptation +/- 1 MCS correction
•
Output
•
Output
•
up to 64QAM support
•
up to 16 QAM support
1 TTI
MCS TBS
MCS ATB
•
MCS: Modulation & Coding Scheme
TBS: Transport Block Size
ATB: Automatic Transmission Bandwidth
32
Adaptive Transmission Bandwidth (ATB): Responsible for defining maximum number of PRBs that can be
assigned to a particular UE by UL SCH
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RRM Overview
Slide 33
Extended UL Link Adaptation (E-ULA) concept (RL30)
With LTE1034 the 3 processes (UL AMC, UL ATB and UL OLLA) that rule the UL Link Adaptation,
work synchronized but independently to each other.
LNCEL: actUlLnkAdp;
Activate uplink link adaptation;
off (0), slowAmcOllaATB (4), eUlLa (5), fUlLa (6);
Default: eUlLa (5)
Eliminate any possibility of BLER target drifting by:
•
•
stopping the SLOW AMC algorithm (ILLA)
leaving the MCS regulation the OLLA
algorithm
Therefore OLLA algorithm is unchanged and
become the only one ruling the MCS index up and
down
OLLA reacts relatively fast when it comes to
reduce MCS index and slowly enough when it
comes to upgrade MCS index
The main idea
Slow
ATB
OLLA
AMC
ATB is no longer Power Headroom (PHR) based
but BLER based (with PHR correction).
It will become active only when the OLLA has
already reached the lower possible limit for the
MCSindex
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Most of all SlowATB is coordinated with OLLA.
This means that SlowATB acts only when OLLA
has no longer margin left in terms of reaction.
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RRM Overview
Slide 34
E-ULA activation and composition
Parameter actUlLnkAdp activates Link Adaptation and defines its mode
ATB
actUlLnkAdp
ILLA
OLLA
PHR based
BLER based
off
eUlLa
slowAmc
slowAmcATB
slowAmcOlla
slowAmcOllaATB
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RRM Overview
Slide 35
LTE829: Increased uplink MCS range (RL30)
- UL AMC shall select the MCS to be employed from the table below according to the radio conditions
MCS Index
I MCS
Modulation
Order
Q
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
35
'
m
TBS
Index
I TBS
2
2
2
2
2
2
2
2
2
2
2
4
4
4
4
4
4
4
4
4
4
6
6
6
6
6
6
6
6
0
1
2
3
4
5
6
7
8
9
10
10
11
12
13
14
15
16
17
18
19
19
20
21
22
23
24
25
26
reserved
Redundancy
Version
rvidx
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
2
3
•
•
•
Initial UL MCS range is restricted from MCS 0 to MCS 20 (QPSK & 16QAM)
LTE829 Increased UL MCS range introduces 16QAM High MCSs and it
allows for extending the range of MCSs used for 16QAM UEs beyond
MCS20 to:
• MCS21
• MCS22
• MCS23
• MCS24
Approximately 25% higher UL peak rates
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RRM Overview
Slide 36
LTE1495: Fast Uplink Adaptation (F-ULA) (RL60)
System level simulation results
FULA immediate
MCS adaptation
FULA high UE
TP available
EULA slow MCS increasing
EULA lower UE TP during
transition phase
1 UE attached in good radio
conditions
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RRM Overview
Slide 37
LTE1495: Fast Uplink Adaptation (F-ULA) (RL60)
Evolution of UL Link Adaptation:
Link Adaptation
AMC
UL LA
E-ULA
F-ULA
ILLA
Slow AMC
Not used with E-ULA
Fast AMC
OLLA
OLLA
OLLA unchanged
Modified OLLA
Slow ATB
- PHR based
New ATB
- PHR and BLER based
Modified ATB
LNCEL:ulamc​Enable = True
LNCEL:ulatb​Enable = True
LNCEL:act​Ul​Lnk​Adp =
eUlLa
LNCEL:act​Ul​Lnk​Adp = fUlLa
OLLA and ATB
synchronization
F-AMC core integrates all
functional blocks
ATB
Parameter activation
Comment
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PHR: Power Headroom Report
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RRM Overview
Slide 38
LTE44: 64QAM in UL (FL16)
Before and after LTE44
• Feature LTE44 introduces 64 QAM modulation scheme in UL increasing maximum achievable UE uplink
throughput in a very good radio conditions and improving average cell capacity
• Higher peak UL throughputs can be achieved due to the support of higher Modulation and Coding Schemes
(MCSs)  MCS 21 – MCS 28
UL CELL
Capacity
UL CELL
Capacity
With activated LTE44 – 64QAM in UL
Without LTE44 – 64QAM in UL
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RRM Overview
Slide 39
LTE44: 64QAM in UL (FL16) - Technical Details
Signal quality requirements
• Due to its higher vulnerability to interference, 64 QAM requires higher SINR (Signal to Noise and Interference
Ratio) values than in case of lower modulations (QPSK or 16 QAM)
• UEs will use 64 QAM modulaiton in a very good radio conditions
UL 1Tx-2Rx, 10% BLER target, 12 PRBs
25.00
QPSK
20.00
16 QAM
64 QAM
SINR [dB]
15.00
10.00
5.00
0.00
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
-5.00
-10.00
39
*4GMax Link Level simulation results
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MCS index
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RRM Overview
Slide 40
LTE44: 64QAM in UL (FL16)
Dimensioning Aspects - Peak UL throughput
• Operating band: 2600 MHz
• Clutter type: Dense Urban
• Inter Site Distance: 500 m
• Duplex mode: TDD
• Frame configuration: 1
• Special subframe format: 7
• 100% penetration of UE
Categories 5 & 8
• Antenna configuration:
• UL: 2Rx MRC
• Frequency scheduler:
• UL: Channel aware
Peak UL user throughput
7600
Average UL cell capacity
[kbps]
General assumptions
7400
7200
7000
14%
10%
6800
6600
6400
6200
6000
16QAM (MCS20)
16QAM (MCS24)
64QAM (MCS28)
Coclusion
• Activation of feature LTE44 – 64QAM in UL brings slight average UL cell throughput
improvement – about 14% comparing to basic 16QAM (MCS20) transmission and about 4%
comparing to 16QAM with MCS24 (activated feature LTE829 – Increased UL MCS range)
• Improvement of average cell capacity is quite low comparing to the MCS24 transmission
(LTE829 – Increased UL MCS range) due to the fact that 64 QAM modulation requires
much better radio conditions (higher SINR values)  64 QAM can be used close to the eNB
causing that only small fraction of UEs in the cell will use it (assuming all of them are UL 64
QAM capable)
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RRM Overview
Slide 41
LTE44: 64QAM in UL (FL16) - Compliance Aspects
• Feature LTE44 – 64QAM in UL is supported only by the 3GPP UE Categories 5 and 8 that support 64 QAM
modulation scheme in UL
• UE Categories 1 – 4 and 6, 7 does not support the 64 QAM modulation in UL – there will be no gain observed for them
after feature activation
UE Category
Maximim number of ULSCH transport block
bits transmitted within a
TTI
Maximum number of
bits of an UL-SCH
transport block
transmitted within a
TTI
Support for 64QAM i
UL
Category 1
5160
5160
No
Category 2
25456
25456
No
Category 3
51024
51024
No
Category 4
51024
51024
No
Category 5
75376
75376
Yes
Category 6
51024
51024
No
Category 7
102048
51024
No
Category 8
1497760
149776
Yes
3GPP TS 36.306, table 4.1-2
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RRM Overview
Slide 42
LTE2479: 256QAM Modulation in Downlink (FL16A)
Background - modulation
Q
Q
Each modulation symbol has its representation on
constelation diagram
ISD
I
I
• The higher the modulation order, the more modulation
symbols need to be reflected on the constalation diagram
• The more modulation symbols need to be reflected, the
smaller inter-symbol distance (ISD) is experienced
- Smaller distance between adjacent modulation symbols
leads to higher SINR requirement, as the risk of
incorrect symbol detection is higher
QPSK
16 QAM
Q
Q
I
64 QAM
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256 QAM
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RRM Overview
Slide 43
LTE2479: 256QAM Modulation in Downlink (FL16A)
Before & after LTE2479
Before
After
• No 256QAM possible for DL transmission
•
256QAM can be used for DL transmission
• UDP peak rates up to:
•
Improved spectral efficiency
− FDD: ~561,6Mbps (4CC CA, 4x2MIMO, 4x20MHz, 64QAM)
− TDD: ~327Mbps (3CC CA, 2x2MIMO, 3x20MHz, TDD frame
config 2, 64QAM)
• Gain numbers depend on 256QAM area probability and
availability of 256QAM capable UEs
•
UDP peak rates up to:
− FDD: ~748Mbps (4CC CA, 4x2 MIMO, 4x20MHz,
256QAM)
− TDD: ~436Mbps (3CC CA, 2x2 MIMO, 3x20MHz, TDD
frame config 2, 256QAM)
DL CELL
Capacity
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RRM Overview
Slide 44
Module Contents
• Radio Resource Management (RRM) Overview
• Scheduler
• Adaptive Modulation and Coding (AMC)
• Outer Loop Quality Control (OLQC)
• Power Control
• Multiple Inputs Multiple Outputs (MIMO)
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RRM Overview
Slide 45
Outer Link Quality Control (OLQC)
Optimize the DL performance
Feature: CQI Adaptation (DL)
• CQI information is used by the scheduler & link adaptation in such a way that a certain BLER of the 1 st
HARQ transmission is achieved
• CQI adaptation is the basic mean to control Link Adaptation behavior and to remedy UE measurement
errors
• Only used in DL
• Used for CQI measurement error compensation
– CQI estimation error of the UE
– CQI quantization error or
– CQI reporting error
• It adds a CQI offset to the CQI reports provided by UE. The corrected CQI report is provided to the DL Link
adaptation for further processing
• CQI offset derived from ACK/NACK feedback
Feature ID(s): LTE30
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RRM Overview
Slide 46
Support of aperiodic CQI reports
Functionality
- Aperiodic CQI reports scheduled in addition to
periodic reports
• Periodic CQI reports on PUCCH
• Aperiodic CQI reports on PUSCH
UL grant + CQI indicator
Description
- Controlled by the UL scheduler
Perio
• Triggered by UL grant indication (PDCCH)
dic C
- Basic feature
Ap e r
iodic
• Benefits
• Not so many periodic CQIs on PUCCH needed
• Allow frequent submission of more detailed reports (e.g.
CQIs
QI (P
U
(PU S
CCH
)
CH )
MIMO, frequency selective parts)
Feature ID(s): LTE767
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RRM Overview
Slide 47
Module Contents
• Radio Resource Management (RRM) Overview
• Scheduler
• Adaptive Modulation and Coding (AMC)
• Outer Loop Quality Control (OLQC)
• Power Control
• Multiple Inputs Multiple Outputs (MIMO)
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RRM Overview
Slide 48
LTE RRM: Power Control
Improve cell edge behavior, reduce inter-cell interference & power consumption
•Downlink:
- There is no adaptive or dynamic power control in DL but semi-static power setting
- eNodeB gives flat power spectral density (dBm/PRB) for the scheduled resources:
• The power for all the PRBs is the same
• If there are PRBs not scheduled that power is not used but the power of the remaining scheduled
PRBs doesn’t change:
- Total Tx power is max. when all PRBs are scheduled. If only 1/2 of the PRBs are scheduled the Tx
power is 1/2 of the Tx power max ( i.e. Tx power max -3dB)
- Semi-static: PDSCH power can be adjusted via O&M parameters
• Cell Power Reduction level: dlCellPwrRed [0...20] dB attenuation in 0.1 dB steps
Feature ID(s): LTE27
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RRM Overview
Slide 49
Power Control - Downlink Power Boosting for Control
Channels
• Offsets determine power shifts for subcarriers which carry PCFICH/PHICH or cell-specific Reference Signal
(and PRS)
Benefits:
• Better PCFICH detection avoids throughput degradation
due to lost subframes
• Higher reliability of PHICH avoids unnecessary
retransmissions causing capacity degradation and
additional UE power consumption
• Better channel estimation avoids throughput degradation
and improves HO performance
Cons:
• Small degradation on PDSCH subcarriers: Subcarrier
power boosting only allowed if the excess power is
withdrawn from the remaining subcarriers
Example of Reference Signals power boosting
Feature ID(s): LTE430
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RRM Overview
Slide 50
UL Power Control
Improve cell edge behavior, reduce inter-cell interference and power consumption
Uplink:
• UL PC is a mix of Open Loop Power Control & Closed Loop Power Control:
PPUSCH (i)  min{PCMAX ,10 log10 (M PUSCH (i))  P0 _ PUSCH ( j )   ( j )  PL  TF (i)  f (i)}[dBm]
• Closed Loop PC component f(i): Makes use of feedback from the eNB. Feedback are TCP* commands
sent via PDCCH to instruct the UE to increase or decrease its Tx power
• UL Power control is Slow power control:
– No need for fast power control as in 3G: if UE Tx power
2) SINR measurment
3) Setting new power offset
was high it incremented the co-channel for other UEs.
– In LTE all UEs resources are orthogonal in frequency &
time
*TPC: Transmit Power Control
50
4) TX power level
adjustment with the new
offset
1) Initial TX power level
Feature ID(s): LTE27&LTE28
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RRM Overview
Slide 51
UL Power Control
Uplink (cont.):
• UL PC is a mix of Open Loop Power Control & Closed Loop Power Control:
PPUSCH (i )  min{PCMAX ,10 log10 ( M PUSCH (i ))  P0 _ PUSCH ( j )   ( j )  PL  TF (i )  f (i )}[dBm]
• PCMAX: max. UE Tx power according to UE power class; e.g. 23dBm for class 3
• MPUSCH: # allocated PRBs. The UE Tx Power is increased proportionally to the # of allocated RBs.
Remaining terms of the formula are per RB
• P0_PUSCH: eNB received power per RB when assuming path loss 0 dB. Depends on α
• α: Path loss compensation factor. Three values:
– α= 0, no compensation of path loss
– α= 1, full compensation of path loss (conventional compensation)
– α ≠ { 0 ,1 } , fractional compensation
• PL: DL Path loss calculated by the UE
• Delta_TF: increases the UE Tx power to achieve the required SINR when transmitting a large number of
bits per RE. It links the UE Tx power to the MCS.
Feature ID(s): LTE27&LTE28
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RRM Overview
Slide 52
Conventional & Fractional Power Control
• Conventional PC schemes:
• Attempt to maintain a constant SINR at the receiver
• UE increases the Tx power to fully compensate for increases in the path loss
• Fractional PC schemes:
• Allow the received SINR to decrease as the path loss increases.
• UE Tx power increases at a reduced rate as the path loss increases. Increases in path loss are only
partially compensated.
• [+]: Improve air interface efficiency & increase average cell throughputs by reducing Intercell interference
- 3GPP specifies fractional power control for the PUSCH with the option to disable it & revert to conventional
based on α
UL
SINR
UL
SINR
Fractional Power
Control: α ≠ { 0 ,1}
Conventional Power Control:
α=1
UE Tx
Power
UE Tx
Power
If Path Loss increases by 10
dB the UE Tx power increases
by 10 dB
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If Path Loss increases by
10 dB the UE Tx power
increases by < 10 dB
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RRM Overview
Slide 53
LTE1336: Interference aware UL-Power Control (RL60)
Interference in LTE UL plays critical role determining the throughput
• UL interference is coming from neighboring cell UEs
- It cannot be predicted since we do not know how the UEs will be
distributed
UL Power control illustration
eNodeB1
- Contributions to interference are most prominent from cell-border UEs
eNodeB2
UL interference
• As a result the role of PC is to provide the required SINR while controlling
at the same time the interference caused to neighboring cells
• Looking at the UL SINR formula…
Affected UE
Useful signal is already
close to maximum
SINR =
S
I+N
=
Cell- center
UE
S
Σ(I1,I2, … In)
Noise N is negligible in
interference limited
scenarios: I >> N
Cell edge users inject as much
interference to neighboring eNB as to
their serving eNB. Therefore
contributions to interference in
adjacent cells are most prominent
from cell-border UEs
… it is clearly visible that it’s better to minimize the interference than
improve the useful signal if we want to get better SINR
53
Cell-edge
UE
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Minor UL
interference
to eNodeB1
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RRM Overview
Slide 54
LTE1336: Interference aware UL-Power Control (RL60)
LTE1336 optimizes tradeoff between the throughput achieved in the own cell and the uplink interference
injected to neighbor cells
• UL power control is trade-off between inter-cell interference and own
cell throughput
UL power-control dilemma
- Increase of UL power brings additional useful signal for own cell UEs,
but adds additional interference for neighboring cells
Interference to
neighbors
• Nokia research invented the algorithm which achieves higher
throughput in a whole range of cells, at reduced UL power settings
(especially for cell-edge UEs)
• Interference-aware ULPC (IAwPC) or so called Interference Penalty
Algorithm (IPA) feature exploits that concept by implementation of new UL
closed-loop power control
Throughput
- Reduction of UL power decrease useful signal but also lowers the
interference
Own throughput
In neighboring
cell ULPC will
increase the power
which will turn back
the effect.
At the end all cells
will be “shouting”
UL power
LTE1336
Breakpoint
Maximized UE throughput with proportional fair scheduler
Improved average and cell-edge throughput
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RRM Overview
Slide 55
LTE1336: Interference aware UL-Power Control (RL60)
• Feature is alternative to the existing LTE28 Closed
Loop UL Power Control for PUSCH/SRS
Open Loop
Closed Loop
LTE27
LTE28 or LTE1336
- PUCCH power control is not impacted
• LTE1336 is based on the OLPC mechanism in the UE
and adds new outer closed loop in the eNB that takes
into account the interference generated to adjacent
cells (estimated based on reported CQI)
Interference-aware
ULPC LTE 1336
• Replaces CLPC
Closed Loop
for PUSCH/SRS
PC LTE28
• System-wide
• SINR and RSSI throughput-based
target window
metric optimization
power control • Compromised cell
Open Loop
steering
LTE27
and UE oriented
PC
• Basic trade-off • UE oriented
between celledge and cellcenter
performance
• Cell oriented
• OLPC algorithm is left untouched
• Additionally new power control activation parameter is
introduced – LNCEL:actUlpcMethod which replaces the
previous parameters:
- ulpcEnable, ulpcPuschEn , ulpcPucchEn, ulpcSrsEn
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RRM Overview
Slide 56
LTE1336: Interference aware UL-Power Control (RL60)
Not activated
LTE1336
eNodeB1
1. UE Tx power adjusted by current
PC mechanism may cause high
interference into adj. cells
•
eNodeB2
Poor SINR
UL interference
Especially due to cell-edge UEs
transmitting with high power
2. This results in poor SINR and
throughput to the affected UE
Cell-edge
UE
Affected UE
Activated
LTE1336
Much
better
SINR
eNodeB1
eNodeB2
UL interference
1. Cell border UEs toned down
2. Reduced interference helps to
restore the loss in link quality caused
by reducing UL power
3. This gives throughput improvement
Affected UE
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Cell- center
UE
Cell-edge
UE
Cell- center
UE
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RRM Overview
Slide 57
LTE1336: Interference aware UL-Power Control (RL60)
• The mechanism is kind of a deal between neighboring eNBs:
- This means: the feature only works (has benefit) with a
multitude of eNBs with feature beeing activated
- Conversely: LTE1336 can give no gain over OL-PC if cells are
not coupled (without coverage overlap)
Throughput improvement is higher than
reduction due to power decrease
Cell border UEs
power decreased
Interference
Limited
• Throughput reduced
• Throughput improved
"Dear neighbors, if I reduce your interference (at
a loss of my own throughput), and if you then do
the same (i.e. not use all of your improved link
budget for higher throughput), there will be
benefit for all of us.„
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RRM Overview
Slide 58
LTE1949: Extend Power Reduction Range (FL15A)
cellPwrRedForMBMS is used to set the power for MBSFN transmission
together with antenna maximum TX power and cell power reduction (pMax,
cellPwrRed).
LNCEL: cellPwrRedForMBMS
Cell power reduction for MBMS
transmission 0...6 dB
Default: 0
The total power of MBSFN sub-frames would be
cell maximum power - cell power reduction - cell power reduction for MBMS
or
pMax - cellPwrRed - cellPwrRedForMBMS
dlCellPwrRed
Static consistency checks have been removed as the allowed value range for
cell power reduction (dlCellPwrRed) shall consider the radio module hardware.
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LNCEL: dlCellPwrRed
Cell power reduction
transmission 0...20 dB
Default: 0
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RRM Overview
Slide 59
Module Contents
• Radio Resource Management (RRM) Overview
• Scheduler
• Adaptive Modulation and Coding (AMC)
• Outer Loop Quality Control (OLQC)
• Power Control
• Multiple Inputs Multiple Outputs (MIMO)
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RRM Overview
Slide 60
MIMO, DL channels & RRM Functionality
RRM MIMO Mode Control Functionality
• Refers to switch between:
▪ Tx Diversity (single stream)
▪ MIMO Spatial Multiplexing (single / dual stream)
▪ 1x1 SISO / 1x2 SIMO
• Provided by eNB only for DL direction
In UL, Flexi eNodeB has 2Rx Div. :
• Maximum Ratio Combining
Benefit: increase coverage by increasing the
received signal strength and quality
Available MIMO options vs. channel type
- Options for Transmit Diversity (2 Tx):
• Control Channels
• PDSCH
- Options for spatial Multiplexing:
• Only DL PDSCH
- MIMO is SW feature
Channel can be configured to use MIMO mode
Channel cannot be configured to use MIMO mode
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RRM Overview
Slide 61
3GPP Transmission Modes (TM) Overview
• transmission modes defined by 3GPP TS36.331234
• BF: beamforming SM: spatial multiplexing
Mode 1
Single-antenna port (SISO)
Mode 2
Transmit diversity (SFBC, Frequency Shift Time Diversity)
Mode 3
Open-loop SM (CQI and RI reported by UE, PM def. by eNb, rank
adapt., rank 1 ≈ TM2, otherwise SM)
Mode 4
Closed-loop SM (CQI, RI, PMI reported by UE, rank adaptation)
Mode 5
Multiuser-MIMO
Mode 6
Closed loop rank 1 precoding
Mode 7
Single-antenna port, port 5 (BF, DRS)
Mode 8
Dual layer BF (port 7 and/or 8)
Rel 9
Mode 9
Multi-stream beamforming with CSI-RS (Channel state information)
Rel 10
FDD & TDD
Rel 8
TDD only
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PMI
- Single stream: 4 matrices (2x1)
- Dual stream: 2 matrices (2x2)
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RRM Overview
Slide 62
Nokia to 3GPP TM mode mapping (FL16)
62
O&M Parameter: dlMimoMode
Corresponding 3GPP Transmission Mode
SingleTX (0)
TM1: Single-antenna port; port 0
TXDiv (10)
TM2: Transmit Diversity
4 way TxDiv (11)
TM2: Transmit Diversity
Dynamic Open Loop MIMO (30)
TM3: OL spatial multiplexing
TM2: Transmit diversity
Closed Loop MIMO 2x2 (40)
TM4: CL spatial multiplexing
TM6: CL Rank=1
Closed Loop MIMO 4x2 (41)
TM4: CL spatial multiplexing
TM6: CL Rank=1
Closed Loop MIMO 4x4 (43)
TM4: CL spatial multiplexing
TM6: CL Rank=1
TM9: Multi-stream beamforming with CSI-RS (Channel state
information) for Release≥10, Cat.6 and Cat.7 is supported
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RRM Overview
Slide 63
Single antenna port transmission (Single TX, RL10)
Downlink
•1x1 SISO or 1x2 SIMO
Uplink
• Flexi eNB supports boths 2-branch & 4-branch RX diversity
• SINR enhanced
• Based on Maximum Ratio Combining (MRC)
• Additional gain from MRC: up to 6 dB (10% BLER, depending on conditions)
• Requires: uncorrelated antennas, x-polarized or d > 10 x wavelength
dlMimoMode
SingleTX (0)
Transmission on a single antenna port, port 0: DL processing
Layer
Mapper
Precoding
Complex symbols after
scrambling and modulation
RE mapping
OFDM signal generation
1 Layer
(Rank = 1)
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RRM Overview
Slide 64
dlMimoMode
TXDiv (10)
4 way TxDiv (11)
Transmit Diversity:
2x2 TXDiv, RL10
4x2 4 way TXDiv, RL50
•
Based on Space Frequency Block Coding (SFBC)
•
Benefits: Increases robustness, diversity gain, enhances cell edge
performance
•
Each Tx antenna transmits the same stream of data with  Receiver gets
replicas of the same signal which increases the SINR
•
Link budget gain: min 3 dB wrt 1x2 case (Tx power per Tx branch as in
single ant. case)
•
Rank 1 transmission, i.e. no multiplication of data rates
•
aka Alamouti scheme
Layer
Mapper
Single antenna Tx
Tx
Div
Precoding
1 data stream
Symbols after scrambling and modulation, 1 code word
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RRM Overview
Slide 65
dlMimoMode
Dynamic Open Loop MIMO (30)
LTE70: Dynamic Open Loop MIMO (RL10)
• Dynamic switch between TX Diversity(TXDiv) and Open Loop Spatial Multiplexing (SM) based on
averaged CQI and RI values.
Open Loop Spatial Mux
•Rank 2 transmission  throughput enhancements, double rate compared to 1TX antenna
• 2 code words
• code book (no PMI feedback, i.e. open loop)
Layer
Mapper
Precoding
2 data streams are supported
RE map, OFDM signal
Symbols after scrambling and modulation, 2 code words
Feedback:
▪ CQI
▪ RI
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RRM Overview
Slide 66
Precoding
- Precoding generates the signals for each antenna port
- Precoding is done by multiplying the signal with a precoding matrix selected from a predefined
codebook known at the eNB and at the UE side
- Closed loop: UE estimates the radio channel, selects the best precoding matrix (the one that offers
maximum capacity) & sends it to the eNB
- Open loop: no need for UEs feedback as it uses predefined settings for Spatial Multiplexing & precoding
Pre-coding codebook for 2 Tx antenna case
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RRM Overview
Slide 67
dlMimoMode
Closed Loop MIMO (40)
LTE703: Adaptive Closed Loop MIMO 2x2 (RL20)
• Dynamic switch between TX Diversity(TXDiv, Rank=1) and Closed Loop Spatial Multiplexing (SM, Rank=2) based on
averaged CQI and RI values and Precoding Matrix Indicator (PMI) reported by UE.
Benefit: High peak rates (2 code words) & good cell edge performance (single code word)
Rank 1 transmission (Single code word, TX Div) enhanced SINR on cell edge
Layer
Mapper
Precoding
1 data stream
Symbols after scrambling and modulation, 1 code word
•Rank 2 transmission (2 code words, SM) throughput enhancements
Layer
Mapper
Precoding
2 data streams are supported
Feedback:
▪CQI
▪RI
▪PMI
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RRM Overview
Slide 68
LTE568: Adaptive Closed Loop MIMO 4x2 (RL50)
dlMimoMode
Closed Loop MIMO 4x2 (41)
• Dynamic switch between TX Diversity(TXDiv, Rank=1) and Closed Loop Spatial Multiplexing (SM, Rank=2) based
on averaged CQI and RI values and Precoding Matrix Indicator (PMI) reported by UE.
Benefit: High peak rates (2 code words) & good cell edge performance (single code word)
Rank 1 transmission (Single code word, TX Div) enhanced SINR on cell edge
Layer
Mapper
Precoding
1 data stream
Symbols after scrambling and modulation, 1 code word
•Rank 2 transmission (2 code words, SM) throughput enhancements
Layer
Mapper
Precoding
2 data streams are supported
2 codewords are the 3GPP max – Ack/Nck and CQI are per codeword – 2 CW gives an optimum overhead.
Even with high order layers (say 8x8) still only 2 CW but we are sending the codewords much faster!
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Feedback:
▪CQI
▪RI
▪PMI
© Nokia 2017
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RRM Overview
Slide 69
LTE1987: Downlink Adaptive Close Loop SU MIMO (4x4)
(FL16)
Introduction
• LTE1987 Downlink adaptive closed loop SU MIMO (4x4) extends the current
MIMO functionality of LTE568 (DL adaptive CL MIMO 4x2, FDD & TDD)
and LTE569 (DL adaptive CL MIMO 4x4, TDD only) to support up to 4
downlink spatial multiplexing layers in LTE FDD and TDD using
transmission modes 4 and 9.
• LTE568 MIMO 4x2 and LTE569 MIMO 4x4 with TM4 are integrated in this
feature
• Doubled DL peak throughput comparing to 4x2 MIMO
• 4x4 MIMO maximum peak throughput is only achieved in very good SINR
conditions
• Interworking with Carrier Aggregation is limited. 4x4 MIMO capable UEs will
not use CA and 4x4 MIMO at the same time
• 4x4 MIMO feature supported in the FDD solution for the first time.
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(excerpt from R2-153465)
2
Support of 4-Layer MIMO in Current Specifications
Currently, the DL MIMO layers a UE supports for a band combination are determined by two parameters: The UE
category, and the band combination-specific indication supportedMIMO-CapabilityDL-r10. So far 4-layers with TM3/4 has
only been possible for UE categories 5 & 8. For all other cases, support of more layers than two has been reserved for
TM9 and TM10 usage.
The issue with more MIMO layers than two is the rank indicator: Currently the rank indicator is determined implicitly by
the UE category, except for TM9/10 for which it may be determined based on the band combination-specific capability.
This is noted also in TS36.306, as shown below (from Rel-10 version of the specification):
4.3.4.7
supportedMIMO-CapabilityDL-r10
This field defines the maximum number of spatial multiplexing layers in the downlink direction for a certain band and
bandwidth class in a supportedBandCombination supported by the UE.
The support for more layers in supportedMIMO-CapabilityDL than given by the “maximum number of supported layers
for spatial multiplexing in DL” derived from the ue-Category (without suffix) in the UE-EUTRA-Capability IE is only
applicable to transmission mode 9.
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RRM Overview
Slide 70
LTE1987: Downlink Adaptive Close Loop SU MIMO (4x4) (FL16)
Before & after
LTE568 & LTE569
LTE1987
• LTE568 supports MIMO 4x2 with TM4 for all
Release 8 Cat≥2 UEs, TDD and FDD
• MIMO 4x4 with TM9 for Release≥10, Cat.6
and Cat.7 is supported
• LTE569 supports MIMO 4x4 with TM4 for all
Cat.5 and Cat.8 UEs, only in TDD
• MIMO 4x4 with TM4 for all Cat. 5 and Cat.8
UEs is supported
TDD and FDD
Cat. 6|7 Rel.≥10 (TM9)
Cat. 5|8 (TM4)
Cat. 5|8 (TM4, TDD only)
Legacy UE (2RX)
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During CP2 declaration a change request affecting the feature scope was still not confirmed but the
scope of LTE1987 includes the modification which has been issued in the change request. The major
change affects the FDD related scope including now MIMO4x4 based on TM4 within the scope of
LTE1987. For TDD, MIMO4x4-TM4 has been already considered in the TDD feature LTE569, 'DL CL SU
MIMO(4x4) - TM4 (see focal point entry).
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RRM Overview
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