LTE1402
Uplink Intra eNodeB CoMP
2017-12-26
Nokia NPO
1
© Nokia 2016
Feature Activation Proposal
Background
• UL throughput performance in some provinces is below the target, where LTE1402 can be
implemented to further improve the user experience in UL at the intra-eNB cell
overlapping area by combining the signal from neighbouring cell to achieve diversity gain.
• Together with the feature activation, UL Combination Mode should be changed from MRC
to IRC.
© Nokia 2016
2
Introduction
What is UL CoMP?
•
Receive UEs uplink signal by more than one cell
• Intra eNB CoMP: cells involved in reception of the UE belong to the same eNB (cells are colocated)
• LTE1402, LTE1691: UL inter-cell intra eNB reception + Interference Rejection Combining (IRC)
•
UL SINR enhancement allows for increased UL throughput on average and cell edge. Gains depend on load and
interference conditions in the network
•
•
Macro deployment: 8% average*
Hotspot deployment: 12% average*
•
•
•
•
In LTE1402 up to 2 cells can be selected for UL reception from so called CoMP sets containing up to 3 cells
Cell selection is performed per TTI based on instantaneous SINR measurements
CoMP reception can only be done for PUSCH. Other UL physical channels are received by serving cell antennas.
Cells involved in LTE1402 CoMP sets can only have 2 RX antennas
•
In LTE1402 Interference Rejection Combining (IRC) algorithm is used for UL reception
•
•
FDD: using 1 cell: LTE979 “IRC for 2 RX paths”; using 2 cells: LTE980 “IRC for 4 RX paths” **
TDD: using 1cell: LTE936 “UL IRC Receiver”; using 2 cells: Enhanced IRC**
*) UL Throughput gains compared to 2RX IRC with no UL CoMP
Nokia 2016
LTE980 and Enhanced
IRC will perform
equally
well to MRC,
LTE979UEs
and LTE936
will underperform
to MRC in noise
• **)
LTE1402
is©transparent
to UEs.
All 3GPP
Rel. whereas
8 compliant
will benefit
from thiscompared
feature.
limited scenarios
3
Technical Details
Why use UL CoMP?
In general, LTE has frequency reuse of 1. That means a lot of interference on cell edges. In effect, on cell
edge UEs are received with similar power by serving and neighbour cell…
• …but not always as a useful signal. To the neighbor cell, this is interference.
• CoMP aims to take this interference and turn it to the useful signal. Neighbor cell can do it to.
• But the main obstacle is to get the data from one cell to the other:
• There is a lot of data to be exchanged between cells
• Delay is crucial
© Nokia 2016
4
Technical Details
Why use UL CoMP?
Benefits of increasing the aperture in intra eNB UL CoMP
Combining gain on intra cell edge due to more antennas
90
40
(up to 3dB)
120
60
Effect of diversity gain in fading channel.
30
0
20
150
30
-10
4 Rx antennas
10
-20
3dB combining
gain
180
0
0.5
1
1.5
2
2.5
3
3.5
4
0
UL CoMP area
0
-10
210
330
2 Rx antennas
240
300
270
Additional diversity gain in fading channels – usually antennas
from two cells will have high enough separation to allow for close
to perfect decorrelation
© Nokia 2016
5
Channel Gain [dB]
-20
0
0.5
1
1.5
2
2.5
3
3.5
4
0
-10
1 Rx antenna
-20
0
0.5
1
1.5
2
Time [sec]
2.5
3
3.5
4
Technical Details
Intra eNB CoMP concept
With co-located cells being processed by the same System Module, sharing data among cells is no longer a problem
UEs in the internal cell boundaries will be received with similar levels by serving and neighbor cell
- Intra eNB UL CoMP is possible within internal cell boundaries
Sector3
LCR3: Tx1 & Rx1
Sector2
LCR2: Tx1 & Rx1
Sector3
LCR3: Tx2 & Rx2
Sector2
LCR2: Tx1 & Rx2
Sector1
LCR1: Tx1 & Rx1
No UL CoMP
between
different eNBs
Sector1
LCR1: Tx2 & Rx2
UL CoMP
RF
Module
System
Module
UL CoMP
Opt6
Opt1
Opt2
Opt3
UL CoMP
© Nokia 2016
6
Benefits and Gains
Stationary test trial result
102
D1: DLTG1
- 30 UE’s
- repetitive 10MB UL transfers
- RSRP -105…-95 dBm
- All UE’s in cell 102
D1
Cell 104
180.0
160.0
140.0
100.0
103
80.0
+10.5%
60.0
40.0
20.0
0.0
UL tput per PRB (kbps)
104
M8012C26/PDCP Throughput UL Mean (kbps)
M8011C37/UL PRB utilisation per TTI Mean (%)
M8001C217/Average number of available PRBs per TTI on PUSCH
UL tput per PRB (kbps)
LTE_5544b/Average SINR for PUSCH
Average MCS
Average number of UE's per TTI utilizing UL CoMP
M8001C223/Active UE per Cell average
capacity gain (%) [tput©per
PRB]2016
Nokia
7
+23.6%
120.0
D2
D2: DLTG2
- 72 UE’s
- repetitive 10MB UL transfers
- RSRP -90…-95 dBm
- UE’s both in cells 104 and 102
Cell 102
Cell 12033 / 104 / LCR1 Cell 12035 / 102 / LCR3
LTE1402 OFF LTE1402 ON LTE1402 OFF LTE1402 ON
4658.6
5541.2
2636.8
2895.0
84.0
80.8
86.0
85.4
42.0
42.0
42.0
42.0
132.1
163.3
73.0
80.7
15.8
16.9
6.1
7.6
18.5
21.2
13.5
14.6
0.0
2.4
0.0
1.2
25
27
37
39
0.0
23.6
0.0
10.5
Likely UEs in D1 were not doing CoMP
at all, gain for cell 102 comes only from
D2 UEs.
1dB increase in SINR for PUCCH as
number of RX antennas doubled – no
IRC combining gains visible in the
counters.
Benefits and Gains
Drive test trial result
•Stationary call generators placed in the cells
•40 UEs driven around the test route
•KPIs collected for whole network
30 UEs in 1
cell
eNB 47
8% TP gain
on network
level
170.0
160.0
150.0
+8%
140.0
130.0
120.0
LTE1402 OFF
110.0
100.0
UL tput per PRB (kbps)
LTE1402 ON
M8012C26/PDCP Throughput UL Mean (kbps)
M8011C37/UL PRB utilisation per TTI Mean (%)
M8001C217/Average number of available PRBs per TTI on PUSCH
UL tput per PRB (kbps)
LTE_5544b/Average SINR for PUSCH
Average MCS
Average number of UE's per TTI utilizing UL CoMP
M8001C223/Active UE per Cell average
capacity gain (%) [tput per PRB]
© Nokia 2016
8
12 UEs
Network level
LTE1402 OFF LTE1402 ON
1789.9
1930.2
27.5
27.5
43.4
43.5
149.9
161.5
16.9
17.4
20.6
21.3
0.0
1.4
9.5
8.9
0.0
7.8
20 UEs in 3
cells
eNB 49
eNB 41
42 UEs in
between 2
cells
eNB 43
Parameter Settings
LNBTS
mrbtsId
120000
LNCEL
lnBtsId
120000
Current
actUlCoMp
New
actUlCoMp
0
1
mrbtsId
120000
120000
120000
lnBtsId
120000
120000
120000
Current
New
lnCelId ulCombinationMode ulCombinationMode
11
0
1
12
0
1
13
0
1
ULCOMP
ULCOMPCELLLIST
New
mrbtsId lnBtsId ulCoMpId ulCoMpSinrThreshold
120000 120000
1
10
New
mrbtsId lnBtsId ulCoMpId
120000 120000
1
120000 120000
1
120000 120000
1
© Nokia 2016
9
listId
ulCoMpCellList
1
11
2
12
3
13
Performance update after feature activation – PY_Cluster01
© Nokia 2016
10
• Counter “UL_INTRA_ENB_COMP_UE_AVG” starts pegging after the activation
• UL IP throughput and average UE power headroom improved after feature activated on 23/Dec 00:00.
Performance update after feature activation – PY_Cluster01
© Nokia 2016
11
• Accessibility and Retainability KPIs are maintained.
• X2 handover performance is maintained
Performance update after feature activation – PY_Cluster01
© Nokia 2016
12
• Inter RAT mobility is maintained.
• UL and DL Data volumes are following the normal trend.
Performance update after feature activation – PY_Cluster01
• PYPY11C was the troublemaker on 25/Dec, where the UE was in poor radio condition (average power headroom = -15 dBm), causing a long duration to transmit
moderate amount of data, resulting an average throughput of 100 Kbps in UL.
• 26/Dec is not yet a full day result, only up to 17:00
© Nokia 2016
13
Conclusion
• A 10% improvement on UL throughput is
observed based on the collected data
between 18/Dec 0:00 to 26/Dec 17:00, from a
level of 1870 Kbps to 2070 Kbps.
• It is recommended to implement the feature in
the network to provide a better user
experience in UL performance at the intra-eNB
cell boundary area.
• The overshooting cells at cluster border, which
is highlighted before, couldn’t benefit much
from this feature since the combining gain only
applicable to cell overlapping area. Hence the
proposal to down-tilt overshooting cells still
valid in order to further improve the overall
performance.
© Nokia 2016
14
10%