1. Test strategy towards Massive MIMO Using LTE-Advanced Pro eFD-MIMO
Shatrughan Singh, Technical Leader
Subramaniam. H, Senior Technical Leader
Jaison John Puliyathu Mathew, Senior Engg. Project Manager

2. Abstract
A path for Massive MIMO(R15) is derived from concepts of FD-MIMO(R13-14).
FD-MIMO is derived from 8x8 MIMO(Rel-10)
FD-MIMO Supports upto16 CSI-RS ports in R13 & upto 32 in R14.
The intent of this paper is to set a test strategy platform and emulate test scenarios of eFD-MIMO thereby validating key performance and functional indicators which could be further utilised and extended for Massive MIMO.

3. Motivation behind eFD-MIMO/Massive MIMO
The main motivation is to improve:
Cell coverage
Cell edge user experience
Average spectrum efficiency
Optimise load-balancing between cells

4. Evolution path for Massive MIMO
Massive MIMO is a feature where base stations have very large numbers of antennas (in hundreds)
Massive MIMO will facilitate UE to report bigger rank/CQI
3GPP release
R10-R12 LTE-A
R13 LTE-A Pro
R14 LTE-A Pro
R15-5G
MIMO Technology
2D MIMO
FD-MIMO
eFD-MIMO
Massive MIMO
No. of CSI-RS ports
(Base station) 8 16 32
>=64 (assumed)
Transmission Mode
TM9, TM10
TM9, TM10 (assumed)
CSI-RS transmission
NonPrecoded
NonPrecoded/ Beamformed
NonPrecoded/ Beamformed (assumed)
No. of layers supported by UE
8 (assumed)

5. eFD MIMO
eFD-MIMO in 3GPP R14 increases total number of CSI-RS antenna ports upto 32.
Vertical and Horizontal beam propagation using 2D-AAA (Active antenna array) system applied with Kronecker Product (KP).
Increased MIMO layers facilitates optimal channel estimation by UE

6. eFD MIMO configuration
eFD-MIMO has two types of CSI-RS transmission,
CLASS-A (Non-Precoded)
CLASS-B (Beamformed)
Class-A or Class-B is configurable by higher layers

7. Non-precoded CSI-RS transmission (Class-A)
CSI-RS remains cell specific and not applied with any precoding.
In LTE Rel-10, upto 8 antenna CSI-RS ports (15-22) were supported.
eFD-MIMO will have upto 32 antenna ports (15-46) supported

8. Aggregation of CSI-RS Configuration
Class-A type supports total upto 32 CSI-RS Antenna ports.
Upto 32 CSI-RS Antenna ports achieved by aggregation of multiple CSI-RS configurations as mentioned below:
Note: Maximum number of UE-Specific DMRS ports are 8 (ports 7 to 14) and maximum supported layers by UE is still upto 8. So, UE can report only maximum 8 layers (Rank) to eNodeB

9. Codebook Config for Non-precoded type
No. of CSI-RS ports determined by codebookconfig
Below table shows all the possible combinations of (N1,N2) and (O1,O2) w.r.t different CSI-RS antenna ports {8,12,16,20,24,28,32}
(N1, N2) corresponds to number of antenna ports per polarization
(O1, O2) corresponds to spatial over-sampling rate in dimension x

10. Beamformed CSI-RS transmission (Class-B)
Precoded like DMRS. Allows upto 8 CSI-RS antenna ports (15-22) with one or more CSI-RS resource configuration
Concepts of multiple beam and CRI
codebook selection defined in Table to to precode CSI-RS
Total number of beams configured to UE is specified in , Section 6.3.2 

11. CRI Configuration in Beamformed (ClassB)
Class-B UE measures CRI-Upto 8 beam and reports optimal beam index + CSI to eNodeB.
Dedicated to selected UEs
Base station schedules data based on CRI+CSI feedback

12. Scenario of Class-A and Class-B transmission
Applicable when base station does not have current awareness of UE channel condition (during scheduling request for DL traffic). This is applicable for cell-center UEs.
Class-B
Applicable when base station has current awareness of UE channel condition (during on-going traffic with moving users) or UE reporting bad CSI in class-A because of cell edge.
This also increases cell coverage area.

13. Conclusion
IMT-2020 requirement is increase in peak data rate, average data rate, spectrum efficiency, network energy efficiency, area traffic capacity and connection density.
FD-MIMO simulation results:
Performance gain with beamforming in elevation dimension (20% gain in cell edge and 5% in cell average)
Performance gain of load balance with EBF/FD-MIMO in Het-Net (27% average gain and 39% cell edge gain)
Performance gain of MU-MIMO with EBF/FD-MIMO
- 3D-UMa : 98.2% cell average and 91.2% cell edge performance gain
- 3D-UMi : 117.3% cell average and 116% cell edge performance gain
With Massive MIMO we will possibly meet IMT-2020 requirement

14. References 3GPP TSG RAN WG1 Meeting #78bis R1-143730
3GPP TS , (RRC) Protocol specification (Release 14)
3GPP TS , UE radio access capabilities (Release 14)
3GPP TS , Physical channels and modulation (Release 14)
3GPP TS , Multiplexing and channel coding (Release 14)
3GPP TS , Physical layer procedures (Release 14)
3GPP TR , Study on elevation beamforming / Full-Dimension (FD) Multiple Input Multiple Output (MIMO) for LTE (Release 13)
3GPP TSG RAN WG1 Meeting #78bis R
3GPP TSG RAN WG1 Meeting #82bis R
3GPP TSG RAN WG1 #78bis R
Recommendation ITU-R M (IMT-2020)

15. Authors Biography
Shatrughan Singh
Working with Aricent for past 5+ years and total Telecom domain experience of 10+ years. Currently located in UK, working on LTE advanced releases of protocol and feature testing needs of client
Subramaniam H
Working with Aricent for past 8+ years and total Telecom domain experience of 12+ years. Currently located in UK, working on LTE protocol and feature testing needs of client
Jaison John Puliyathu Mathew
Working with Aricent for past 7+ years and has total Telecom domain experience of 14+ years. Currently located in UK and managing onsite testing team of engineers

16. Thank You!!!