Enhanced CRS and 4Rx SU-MIMO Interference Mitigation Performance Requirements for LTE
The objective of this report is to investigate feasibility and specify requirements for 1) CRS-IM receivers for the generic scenarios with different number of CRS APs (2, 4) and different number of UE receive antennas and 2) SU-MIMO IM receivers for UEs equipped with 4 receive antennas. The work item [2] has the following detailed objectives:
- Investigate feasibility and specify requirements for the CRS-IM receivers for the generic scenarios with different number of CRS APs (2, 4) and different number of UE receive antennas for synchronous networks:
- Stage 1: Investigate performance benefits and feasibility of using CRS-IM receivers:
- Identify target scenarios including deployment scenarios, interference models, and others
- Reuse Rel-12 NAICS and Rel-13 CRS-IM WIs assumptions as the starting point
- Evaluate the CRS-IM performance benefits
- Identify reference CRS-IM receiver structure assumptions including at least number of cancelled cell(s), and IM algorithm.
- The tradeoff between complexity and performance should be analyzed in order to define reference receivers.
- Stage 2: Specify UE demodulation and CSI reporting performance requirements to verify practical CRS-IM operation for the identified scenarios based on the outcome of Stage 1.
- The work should be done under the following assumptions:
- The following scenarios are prioritized:
- 2 RX antennas UEs with 4 CRS APs in the serving and interference cell(s)
- 2 RX antennas UEs with a mix of 2 and 4 CRS APs in the serving and interference cell(s)
- 4 RX antennas UEs with 2 and 4 CRS APs in the serving and interference cell(s)
- CRS-IM can be used for different downlink physical channels:
- First priority: PDSCH (both CRS- and DMRS-based transmission modes)
- Second priority: DL control channels including PDCCH, PCFICH, PHICH and EPDCCH
- Non-colliding CRS scenarios are primarily considered.
- Colliding CRS scenarios are not precluded.
- Homogeneous deployment scenarios are primarily considered
- Heterogeneous deployment scenarios are not precluded.
- Single carrier case.
- Reference PDSCH receiver structure: LMMSE-IRC with CRS-IM.
- Investigate feasibility and specify requirements for the enhanced SU-MIMO inter-stream interference mitigation (SU-MIMO IM) receivers for the scenarios with 4 receive antennas UEs
- Stage 1: Investigate performance benefits and feasibility of using SU-MIMO IM receivers for the scenarios with 4 receive antennas UEs.
- Investigate and agree on target scenarios including layer number for spatial multiplexing, MCS, propagation conditions and others for performance evaluation
- Reuse the assumptions for Rel-12 SU-MIMO IM (Type-C receiver) and Rel-13 4Rx MIMO performance requirements as starting point.
- SU-MIMO scenarios
- rank 2/3/4 SU-MIMO is considered
- The maximum number of layers (e.g. rank3/4) should be determined based on feasibility study (e.g. operating SNR), realistic Tx EVM assumption and the study on performance gains, reference receiver complexity and testability, etc.
- Strive to reuse agreed Tx EVM for 4Rx in Rel-13 if the related agreement can be reached
- Consider 2 and 4 CRS APs scenarios
- Channel correlations
- Focus on the Medium, Medium A and High antenna correlation models
- Modulation order: up to 256QAM
- The considered modulation orders should be decided based on feasibility study (e.g. operating SNR), realistic Tx EVM assumption, performance gains, reference receiver complexity and testability, etc.
- Strive to reuse agreed Tx EVM for 4Rx in Rel-13 if the related agreement can be reached.
- Identify the reference receiver structure for SU-MIMO IM evaluation
- R-ML is considered in high priority
- Evaluate the performance of enhanced SU-MIMO IM receivers.
- Stage 2: Specify UE demodulation performance requirements to verify enhanced SU-MIMO receivers for the UEs equipped with 4 RX antennas
- Reference receiver structure and other test parameters are based on the outcome of Stage 1.
- Single carrier case.