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

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.

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

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)

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

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

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

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

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

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 36.213 Table 7.2.4-18 to 7.2.4-20 to precode CSI-RS Total number of beams configured to UE is specified in 36.331, Section 6.3.2 

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

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.

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

References 3GPP TSG RAN WG1 Meeting #78bis R1-143730 3GPP TS 36.331, (RRC) Protocol specification (Release 14) 3GPP TS 36.306, UE radio access capabilities (Release 14) 3GPP TS 36.211, Physical channels and modulation (Release 14) 3GPP TS 36.212, Multiplexing and channel coding (Release 14) 3GPP TS 36.213, Physical layer procedures (Release 14) 3GPP TR 36.897, Study on elevation beamforming / Full-Dimension (FD) Multiple Input Multiple Output (MIMO) for LTE (Release 13) 3GPP TSG RAN WG1 Meeting #78bis R1-143730 3GPP TSG RAN WG1 Meeting #82bis R1-156217 3GPP TSG RAN WG1 #78bis R1-143883 Recommendation ITU-R M.2083-0 (IMT-2020)

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

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