1. DAS Impact on LTE Network and UE IBTUF VIII Austin TX, Jan-2014
Nishank Save
Award Solutions

2. Objective
Understand the importance of macro optimization for improving DAS performance
List the RF parameter considerations to improve DAS performance
Explain SINR mapping changes that can improve throughput performance in DAS

3. Importance of Macro Optimization

4. Importance of Macro Optimization
Impact of Macro design on performance is more in DAS than Macro
Macro design
Lower the interference – better the throughput
Lower Macro RSRP
A lower RSRP from a Macro can result in significant cost savings
Lesser number of remotes and antennas required to overcome the Macro RSRP
Cost savings in DAS design
Throughput
Interference
Macro RSRP
DAS Cost $

5. Macro Optimization Challenges
DAS design team needs information about Macro
Inputs about Macro
A Macro was used to cover the venue before DAS deployment
Venue is no longer the primary objective of that Macro
DAS cut-over - Macro optimization?
Access to venues is easier for implementation/ integration/ build out, but limited for walk test and CW tests.
Walk Test and Drive Test data is scarce

6. Optimization Considerations
DAS design team to work in close interaction with the Macro design engineer for surrounding sites
Synergy
DAS cutover plan should include macro optimization plan – downtilts and azimuth changes
Cutover Plan
Abundant walk test and drive test data should be collected
Changes may be needed in legal framework to provide access to venues for walk test and CW tests.
Test Data

7. Action Plan – DAS cutover
Sector 1 – change azimuth from 120 deg to 100 deg
Sector 2 – change downtilt from 6 deg to 8 deg
Sector 3 – change A3 handover offset from 6 db to 2 db
Site
Sector 1 – add A5 measurement report
Sector 3 – change antenna from 65 deg HBW to 35 deg HBW
Site
Reduce from 4 sector site to 3 sector site – deactivate sector 2
Sector 1 – change azimuth from 40 deg to 70 deg
Sector 3 – change downtilt from 6 deg to 4 deg
Site

8. Handover in DAS Tightly controlled handovers reduce interference
6 | Configuring DAS
Tightly controlled handovers reduce interference
Boundaries
Well defined PCIs
Tweak Remote Unit Tx power
Remote Unit
Stairwells
Seating area splits
Select natural boundaries

9. Cell Reselection/Handover Parameters
Entry and exit points to venue
Starts receiving signals from 2nd tier macros
Customize cell reselection parameters
Qrxlevmin / Qoffset / Qrxlevminoffset / Qhyst / Qoffset
Walk test
RRC idle mode
Configure measurement reports A4 and A5
Customize handover parameters
Hys / Thresh / Ocn / Ocs / Off
RRC connected mode

10. Measurement Event A5 on DAS
Served by macro inside venue
Served by DAS inside venue
Shall we increase Thresh1
to speed up handover?
High throughput
Low throughput
Thresh2
Thresh1
Neighbor cell
Time at which the measurement report is sent
Serving cell

11. Measurement Event A4 on Macro
Served by macro
Served by DAS
Shall we increase Thresh to
– slow down handover to DAS?
High throughput
Low throughput
Thresh
Neighbor cell RSRP/RSRQ
Time at which the measurement report is sent
Event A4:
Neighbor becomes better than threshold

12. Design Parameter Considerations for DAS

13. Advertised vs. Actual Tx Power
eNB announces EPRE in SIB2
EPRE
40W eNB (10MHz LTE): EPRE = 18dBm
40mW remote (10MHz LTE): EPRE = -12dBm
Difference = 30 dB
Example

14. SIB Parameter Changes for DAS
UE overestimates path loss
Target Initial Received PowerDAS = Target Initial Received Powermacro ?
If Yes,
UE transmits the RA preamble at higher power (e.g., 30dB)
Optimize Target Initial Received PowerDAS and number of preamble retries

15. Tx Power Attenuation for DAS
Default eNB Tx Power = 40 W
DAS Headend input as low as 0 dBm
Attenuation in downlink using DAS Tray
Reverts to default value after a new download
Damage to the DAS Headend
Parameters may be customized

16. Check for PCI mod 6 and PCI mod 30 conflicts
PCI Planning
PCI = 254 (2, 14)
PCI = 342 (0, 12)
PCI = 402 (0, 12)
No Conflict
Conflict
Check for PCI mod 6 and PCI mod 30 conflicts

17. SINR and Throughput

18. RSRP and SINR Adequate RSRP + Good SINR = Good Throughput Good RSRP
+ Poor SINR = Poor Throughput
SINR is a better measure of potential performance than RSRP

19. CQI and SINR
CQI is estimated by the UE based on SINR of reference signal from the serving cell
DAS often have higher pollution, resulting in lower CQI estimates
CQI-to-SINR mappings should be modified for DAS

20. SINR Mapping Considerations
4 | LTE Essentials for DAS
CQI Index
Modulation
Typical SINR mapping (in dB)
SINR mapping
consideration for DAS (in dB)
Out of Range
1 – 6
QPSK
-6.00 <SINR< 2.75
-4.00 <SINR< 5.00
7 - 9
16QAM
5.00 <SINR< 8.50
6.75 <SINR< 10.75
64QAM
10.75 <SINR
12.50 <SINR

21. Questions?

22. Thank You!