LTE Throughput
Optimizations
LTE Large-Scale Commercial Application, Fast Network Construction
The commercial application of LTE networks speeds up; the terminal industrial chain matures in
2014; and the number of UEs increased dramatically.
The number of commercial LTE networks has reached 274 (28 LTE TDD
networks) by February 17, 2014
300
263
250
200
148
150
100
50
2
16
2009
2010
46
5 million
10 million
100 million
2G
2 years
(1992–1994)
3 years
(1992–1995)
6 years
(1992–1998)
3G
2 years
(2001–2003)
3 years
(2001–2004)
6 years
(2001–2006)
4G
0
2011
UE Quantity
274
2012
2013
2014.2
According to GSA, the number of TD-LTE UE types has increased to 304
by January 30, 2014, among which 63 were smart UEs, exceeding 20%
of the total number. The LTE TDD UE industry chain is mature.
1.8 years
2 years
3.3 years
(Jan 2010–Oct 2011) (Jan 2010–Jan 2012) (Jan 2010–Apr 2013)
The number of LTE users exceed 100 million in 3.3 years, doubling the
growth rate of 2G or 3G UEs.
Increasing rapidly
since 2012
Insufficient LTE Network Optimization Capability
Issue 1: As an end-to-end network KPI, LTE throughput may fluctuate
due to various factors.
Issue 2: Optimization bottlenecks caused by limited optimization
methods due to insufficient in-depth analysis capability of RF
problems in LTE networks
Capacity
expansion
Neighboring
cell
Building
new sites
Bottleneck!
Issue 3: Poor batch delivery and high labor cost due to the current
optimization platform which provides only process data for analysis,
but no clear analysis results and closure actions.
SmartRNO:
1. Supporting neighboring cell planning
checks (topology analysis only)
FMA
FMA:
1. Supporting NE fault analysis and top cell
filtering
2. Cannot provide optimization suggestions
Issue 4: High network risk and O&M cost due to experience-based
adjustment or uniform optimization using baseline values
Suggestions
not
differentiated
Increase the
value as an
attempt. If
KPIs
deteriorate,
decrease the
value again.
Cell
Name
Value on
the Live
Network
Baseline
Value
Optimization
Suggestion
Cell A
X1
Y1
X1–Y1
Cell B
X1
Y1
X2–Y1
Cell C
X2
Y1
X2–Y1
Optimization Scheme
Low spectral efficiency
Low throughput
Poor user experience
Identification of
problematic cells
KPIs evaluation and Identification
of problematic cells
Select top cell groups based on
customer concerns and focus on
top sites
MRF
TCP/IP
RF
Problem isolation &
demarcation
Transmission
RF root
causes
Root cause identification
MME
SP
MRF, alarms, and CHR
Missing neighboring cells
Overshoot island coverage
PCI conflicts
Delayed handovers
PCI confusion
Azimuth exceptions
Deeper w eak coverage
No primary serving cells
Netw ork interference
due to coverage overlap
Uplink/dow nlink
imbalance
Pilot pollution
Perform end-to-end analysis and
associate the impact of various
network nodes on LTE throughput
Perform in-depth analysis to
identify air interface root causes
and problematic scenarios
CHR, MRs, engineering
parameters, and configurations
The blue blocks invoke other topics.
Key parameter adjustment
Optimization
PCI adjustment
Channel check
ACP antenna adjustment
Optimization suggestion for
different root causes
End-to-End Problem Isolation by Segment
Air interface
Air interface channels:
1. Air interface encoding
(MCS/MIMO/IBLER)
2. Air interface resources
(Grant/RB)
3. Weak
coverage/interference
Root Cause
1. Incorrect parameter
settings
2. Limited traffic capacity
3. Poor coverage
4. Interference
5. Handover exceptions
Non-Air Interface
Factors
Bearer network
transmission channels:
1. Bandwidth restriction
2. Long delay and jitter
3. Packet loss and
disorder
Root Cause
1. Incorrect
parameter settings
2. Limited capacity
or capability
3. Transmission
quality problems
Public Network
1. NEs with flow
control
2. Public network
bandwidth
restrictions
Root Cause
1. Incorrect TCP
parameter settings
2. Capacity
restrictions
1
Uu
UE
1. UE capability
2. QCI
configurations
3. AMBR rate
Root Cause
1. Hardware
performance
2. MME
configurations
eNodeB
1. eNodeB rate
restriction
2. eNodeB processing
capability
3. Algorithm feature
restrictions
Root Cause
1. Incorrect parameter
settings
2. Incorrect projects
3. eNodeB exceptions
4. Version quality
problems
CN
1. Registration
configurations
2. Rate
restriction
3. Packet
disorder
Root Cause
1. Incorrect
parameter settings
2. Device faults
3. Version quality
problems
SP
1. Server
capability
2. TCP parameter
settings
3. Software
configurations
Root Cause
1. Hardware
performance
2. Incorrect
parameter
settings
Note: Problems related to public networks and SP servers cannot be analyzed currently.
Weak Coverage Root Cause Location
Weak coverage scenarios:
Missing configurations of neighboring cells/delayed
handovers/island coverage/no primary servicing cells/link
imbalance/weak intensive coverage
Serving cell
Delayed
handovers
UE
✓
Missing
configurations of
neighboring cells
No primary
serving cells
Identification of
weak coverage
root causes
Link
imbalance
Island
coverage
Weak
intensive
coverage
Target cell
Low RSRP of the serving cell and high RSRP of the target cell.
➢
Unconfigured neighbor relationships: If the distance between the UE
and the serving eNodeB is smaller than the average inter-site
distance, the root cause of low throughput is missing configuration of
neighboring cells.
➢
If the distance between the UE and the serving cell is greater than the
average inter-site distance, the root cause of low throughput is island
coverage.
➢
If neighbor relationships are configured and the root cause of low
throughput is delayed handover, adjust handover parameters based
on the signal level difference between the neighboring cell and the
serving cell.
Weak Coverage Root Cause Location
-102 dBm
Serving cell
✓
UE
-104 dBm
Serving cell
UEs close to the serving eNodeB are in weak coverage areas. This
phenomenon is called coverage hole. This occurs because of a coverage
hole, mostly in indoor scenarios close to eNodeBs
Neighboring cell 1
UE
-101 dBm
Neighboring cell 2
Serving cell
UE
✓
✓
Due to link reciprocity in LTE TDD networks, path loss imbalance occurs
between the uplink and downlink. As a result, downlink signals may be too
weak for UEs far from eNodeBs to receive, causing link exceptions. This root
cause does not lead to problems to LTE FDD cells.
At the coverage border of multiple neighboring cells that have small
difference in the signal level, there is no primary serving cells with strong
signals, increasing the probability of ping-pong handovers.
Interference Root Cause Location
Interference scenarios:
overshoot coverage/PCI mod 3 conflicts/pilot
pollution/azimuth exceptions
Serving cell
Pilot
pollution
Overshoot
coverage
Identification of
air interface
root causes
UE
Azimuth
exceptions
Neighboring cell 2
✓
PCI mod 3
conflicts
Neighboring cell 1
The RSRP of the serving cell is high, but the channel quality is low.
➢
If the serving cell has an intra-frequency neighboring cell with a similar
RSRP value, intra-frequency interference has a large impact on the
throughput. If PCI mod 3 conflicts occur, the SINR deteriorates.
➢
If the serving cell has no intra-frequency neighboring cells or its
neighboring cells have low RSRP, inter-RAT interference may occur,
such as intermodulation interference of GSM 1800 band to band F and
outband interference from PAS.
Interference Root Cause Location
✓
PCI: 0
Method of checking the azimuths of cells (relative locations between cells)
PCI: 6
-80 dBm
Serving cell
-84 dBm
Neighboring cell
UE
✓
If PCI mod 3 conflicts occur between the serving cell and neighboring cells and
the reception level of the serving cell is lower than 6 dB, interference occurs in
pilot channels. As a result, the SINR on the RS channel deteriorates, and intrafrequency PCI mod 3 conflicts occur, affecting the throughput.
✓
•
•
•
•
Interference due to azimuth exceptions occurs if the following conditions are met at the
same time:
Relative locations between the serving cell and neighboring cells do not cause
overlapping coverage.
UEs receive signals from the neighboring cells.
PCI mod 3 conflicts occur.
The reception level of the serving cell is lower than 6 dB.
Interference Root Cause Location
Neighboring cell
PCI: 0
PCI: 6
PCI: 0
-84 dBm
-80 dBm
-80 dBm
Interference cell
Serving cell
Neighboring cell
-90 dBm
UE
-82 dBm
PCI: 2
Neighboring cell 2
PCI: 6
-91 dBm
Serving cell
✓
Neighboring cell 1
UE
Overshoot coverage of interference cells occurs when signals
from a remote cell passing through neighboring cells in between
cause interfere to the serving cell.
PCI: 0
-83 dBm
Serving cell
UE
✓
PCI: 1
Interference
cell
Overshoot coverage of the serving cell occurs when signals from
the serving cell passing through neighboring cells in between
cause overlapping coverage with a remote cell.
✓
If PCI mod 3 conflicts do not occur in multiple cells but
the RSRP of these cells are close, there is a probability
that carriers for data service transmission collide with
the RS channel, causing interference to the carriers. As
a result, the SINR deteriorates, and the throughput of
the serving cell decreases, causing pilot pollution.
Root Cause-based Optimization Suggestions
Parameter classification for optimization in specific problematic scenarios
1. Find the exact missing
neighbor relationships,
instead of performing
topology-based search
2. Quantize handover
parameters (CIO)
1. Identify incorrect handover
parameter settings based on air
interface quality
2. Perform targeted optimization for
different handover parameters
(magnetic hysteresis parameters
and CIO)
1. Check and optimize channels
and TMAs to address the
problem of severe path loss
imbalance betw een the uplink
and dow nlink
1. Provide optimization
suggestions on antenna
dow ntilts for cells
experiencing overshoot
coverage or w eak intensive
coverage
1. Provide accurate frequency
optimization suggestions
based on interference
measurement results and
changes associated w ith PCI
optimization
✓
Provide targeted optimization
methods for different problems to
ensure optimization effect.
✓
Perform intensive parameter
management to lower the
Accurate optimization
on neighboring cell
configurations
Accurate
optimization on
handover parameters
Accurate
optimization on
feature parameters
Quantitative
optimization on
antenna parameters
maintenance cost and ensure
PCI optimization
healthy network operation.
✓
Perform regular check on
parameters and neighboring cells to
Missing
configurations of
neighboring cells
Delayed
handovers
Link imbalance
Overshoot
coverage
PCI mod 3
detect minor and potential problems,
conflicts
ensuring optimal network
configurations.
Island coverage
No primary
Weak intensive
coverage
serving cells
Azimuth
exceptions
✓
Perform quantitative analyses on RF
problems and accurately measure
RF root causes
the percentage of weak coverage
Pilot pollution
and interface root causes to resolve
problems.